DEVELOPMENT OF A METHODOLOGY TO DETERMINE
THE APPROPRIATE BUFFER ZONE FOR DEVELOPMENTS
ASSOCIATED WITH WETLANDS, RIVERS AND
ESTUARIES
DELIVERABLE 11: PRACTICAL TESTING / FIELD
TESTING REPORT (DISCUSSION DOCUMENT)
Institute of Natural Resources NPC
I.P. Bredin, D.M. Macfarlane, J.B. Adams,
M.M. Zungu, G.C. O’Brien, G.C. Bate and
I
C.W.S.
Dickens
INR Report No:
476/14
DELIVERABLE 11: PRACTICAL TESTING / FIELD
TESTING REPORT (DISCUSSION DOCUMENT)
Prepared for:
Prepared by:
In Association with:
I.P. Bredin, D.M. Macfarlane, J.B. Adams, M.M. Zungu, G.C. O’Brien, G.C. Bate and C.W.S. Dickens
Please direct any queries to:
Mr Ian Bredin
P O Box 100396, Scottsville, 3209
Tel: 033 3460 796 Fax: 033 3460 895
E-mail: ibredin@inr.org.za
April 2014
Deliverable 11: Practical Testing / Field Testing Report
TABLE OF CONTENTS
1.
INTRODUCTION ....................................................................................................................................... 1
2.
APPROACH TO TESTING THE BUFFER METHOD ........................................................................................ 1
3.
DEVELOPMENT WORKSHOPS .................................................................................................................. 1
3.1.
WRC DEVELOPMENT WORKSHOPS ...................................................................................................... 1
3.1.1.
3.1.2.
First WRC development workshop ................................................................................................ 2
Second WRC development workshop ........................................................................................... 3
3.2.
SASAQS WORKSHOP ........................................................................................................................... 5
3.3.
NATIONAL WETLAND INDABA WORKSHOP ......................................................................................... 7
4.
4.1.
WETLAND CASE STUDIES ......................................................................................................................... 8
MOUNT MORELAND WETLANDS – FROGGY POND .............................................................................. 8
4.1.1.
4.1.2.
4.1.3.
4.1.3.1.
4.1.3.2.
4.1.3.3.
4.1.3.4.
4.1.3.5.
4.1.3.6.
4.1.3.7.
4.1.3.8.
4.1.3.9.
4.1.3.10.
4.2.
Site description ............................................................................................................................. 8
Description of the wetland ........................................................................................................... 9
Outcomes of field testing............................................................................................................ 12
Level of assessment ............................................................................................................................... 12
Proposed development scenario(s) ....................................................................................................... 12
Preliminary threat ratings and buffers ................................................................................................... 13
Sensitivity assessment ........................................................................................................................... 15
Site-based modifiers .............................................................................................................................. 16
Species of conservation concern............................................................................................................ 16
Additional mitigation measures ............................................................................................................. 17
Outcomes of the buffers model ............................................................................................................. 18
Time required to complete the buffers assessment .............................................................................. 26
Summary of comments and concerns raised ......................................................................................... 26
HAMMARSDALE WETLAND ............................................................................................................... 29
4.2.1.
4.2.2.
4.2.3.
4.2.3.1.
4.2.3.2.
4.2.3.3.
4.2.3.4.
4.2.3.5.
4.2.3.6.
4.2.3.7.
4.2.3.8.
4.2.3.9.
4.2.3.10.
4.2.3.11.
4.3.1.
4.3.2.
4.3.3.
4.3.3.1.
4.3.3.2.
Site description ........................................................................................................................... 29
Description of the wetland ......................................................................................................... 30
Outcomes of field testing............................................................................................................ 32
Level of assessment ............................................................................................................................... 32
Proposed development scenario(s) ....................................................................................................... 32
Preliminary threat ratings and buffers ................................................................................................... 32
Sensitivity assessment ........................................................................................................................... 33
Site-based modifiers .............................................................................................................................. 34
Additional mitigation measures ............................................................................................................. 34
Outcomes of the buffers model ............................................................................................................. 35
Time required to complete the buffers assessment .............................................................................. 38
Initial Scenario testing ............................................................................................................................ 38
Summary of comments & concerns raised ............................................................................................ 44
Outcomes of the updated model ........................................................................................................... 47
Site description ........................................................................................................................... 54
Description of the wetland ......................................................................................................... 55
Outcomes of field testing............................................................................................................ 55
Level of assessment ............................................................................................................................... 55
Proposed development .......................................................................................................................... 56
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4.3.3.3.
4.3.3.4.
5.
5.1.
RIVER CASE STUDIES .............................................................................................................................. 58
ELANDS RIVER ................................................................................................................................... 58
5.1.1.
5.1.2.
5.1.3.
5.1.3.1.
5.1.3.2.
5.1.3.3.
5.1.3.4.
5.1.3.5.
5.1.3.6.
5.1.3.7.
5.1.3.8.
5.1.3.9.
5.1.3.10.
5.2.
5.2.3.
5.2.3.1.
5.2.3.2.
5.2.3.3.
5.2.3.4.
5.2.3.5.
5.2.3.6.
5.2.3.7.
5.2.3.8.
5.2.3.9.
5.2.3.10.
6.1.
Site description ........................................................................................................................... 58
Description of the Elands River and use by the Sappi Ngodwana pulp and paper mill .............. 59
Outcomes of field testing............................................................................................................ 59
Level of assessment ............................................................................................................................... 59
Proposed development scenario ........................................................................................................... 59
Preliminary threat ratings ...................................................................................................................... 60
Sensitivity assessment ........................................................................................................................... 60
Site based modifiers ............................................................................................................................... 61
Additional mitigation measures ............................................................................................................. 61
Outcomes of the buffers model ............................................................................................................. 62
Time ....................................................................................................................................................... 63
Scenario testing ..................................................................................................................................... 63
Comments .............................................................................................................................................. 66
THUKELA ........................................................................................................................................... 66
5.2.1.
5.2.2.
6.
Outcomes of the buffers model ............................................................................................................. 56
Core habitat for species of conservation concern.................................................................................. 57
Site description ........................................................................................................................... 66
Description of the lower Thukela River and local land uses and proposed land-use development.
67
Outcomes of field testing............................................................................................................ 67
Level of assessment ............................................................................................................................... 67
Proposed development scenario ........................................................................................................... 68
Preliminary threat ratings ...................................................................................................................... 68
Sensitivity assessment ........................................................................................................................... 68
Site based modifiers ............................................................................................................................... 69
Additional mitigation measures ............................................................................................................. 69
Outcomes of the buffers model ............................................................................................................. 69
Time ....................................................................................................................................................... 70
Scenario testing ..................................................................................................................................... 71
Comments .............................................................................................................................................. 74
ESTUARY CASE STUDIES ......................................................................................................................... 74
FAFA ESTUARY .................................................................................................................................. 74
6.1.1.
6.1.2.
6.1.3.
6.1.3.1.
6.1.3.2.
6.1.3.3.
6.1.3.4.
6.1.3.5.
6.1.3.6.
6.1.3.7.
6.1.3.8.
6.1.3.9.
6.1.3.10.
Site description ........................................................................................................................... 74
Description of the estuary .......................................................................................................... 75
Outcomes of field testing............................................................................................................ 76
Level of assessment ............................................................................................................................... 76
Proposed development scenario ........................................................................................................... 76
Preliminary threat ratings ...................................................................................................................... 76
Sensitivity assessment ........................................................................................................................... 77
Site based modifiers ............................................................................................................................... 77
Additional mitigation measures ............................................................................................................. 77
Outcomes of the buffers model ............................................................................................................. 78
Time required to complete the buffers assessment .............................................................................. 79
Scenario testing ..................................................................................................................................... 79
Comments .............................................................................................................................................. 85
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6.2.
GOURITZ ESTUARY ............................................................................................................................ 85
6.2.1.
6.2.2.
6.2.2.1.
6.2.2.2.
6.2.2.3.
6.2.2.4.
6.2.2.5.
6.2.2.6.
6.2.2.7.
6.2.2.8.
6.2.2.9.
6.2.2.10.
7.
Description of the estuary .......................................................................................................... 85
Outcomes of field testing............................................................................................................ 86
Level of assessment ............................................................................................................................... 86
Proposed development scenario ........................................................................................................... 86
Preliminary threat ratings ...................................................................................................................... 89
Sensitivity assessment ........................................................................................................................... 89
Site based modifiers ............................................................................................................................... 90
Additional mitigation measures ............................................................................................................. 90
Outcomes of the buffer model .............................................................................................................. 91
Time required to complete the buffers assessment .............................................................................. 92
Scenario testing ..................................................................................................................................... 93
Summary of comments and concerns .................................................................................................... 96
SENSITIVITY ANALYSIS AND FURTHER REFINEMENT OF THE BUFFER ZONE MODELS ............................. 98
7.1.
FOCUS OF ASSESSMENT .................................................................................................................... 98
7.2.
APPROACH TO ASSESSMENT ............................................................................................................. 98
7.3.
OUTCOMES OF THE DRAFT BUFFER ZONE TOOL ................................................................................ 99
7.3.1.
7.3.2.
7.3.3.
7.3.4.
7.4.
REVISIONS TO THE DRAFT BUFFER ZONE MODELS .......................................................................... 103
7.4.1.
7.4.2.
7.4.3.
7.5.
Sensitivity of outcomes to climatic factors ................................................................................. 99
Sensitivity of outcomes to the sensitivity of water resources ................................................... 100
Sensitivity of outcomes to site-based attributes....................................................................... 101
Sensitivity of outcomes to full range of input variables............................................................ 102
Sensitivity of outcomes to the sensitivity of water resources ................................................... 104
Sensitivity of outcomes to site-based attributes....................................................................... 105
Sensitivity of outcomes to full range of input variables............................................................ 106
CONCLUSIONS FROM THE SENSITIVITY ANALYSIS............................................................................ 107
8.
SUMMARY OF ISSUES / CONCERNS & RECOMMENDATIONS ............................................................... 107
9.
REFERENCES ........................................................................................................................................ 114
10.
APPENDICES .................................................................................................................................... 116
10.1.
APPENDIX A – MINUTES FROM THE FIRST WRC DEVELOPMENT WORKSHOP .................................. 116
10.2.
APPENDIX B – MINUTES FROM THE SECOND WRC DEVELOPMENT WORKSHOP.............................. 123
10.3.
APPENDIX C – ATTENDANCE REGISTER FOR THE SASAQS WORKSHOP ............................................ 128
10.4.
APPENDIX D – ATTENDANCE REGISTER FOR THE NWI WORKSHOP.................................................. 129
10.5. APPENDIX E – MITIGATION MEASURES PROPOSED UNDER SCENARIO A: AGRICULTURE (IRRIGATED
COMMERCIAL CROPLAND) FOR FROGGY POND ........................................................................................... 132
10.6. APPENDIX F – MITIGATION MEASURES PROPOSED UNDER SCENARIO B: LOW IMPACT RESIDENTIAL
DEVELOPMENT FOR FROGGY POND............................................................................................................. 134
10.7. APPENDIX G - MITIGATION MEASURES PROPOSED FOR THE MIXED-USE DEVELOPMENT SCENARIO
AT HAMMARSDALE WETLAND ..................................................................................................................... 137
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10.8. APPENDIX H: MITIGATION MEASURES PROPOSED FOR THE GOLF COURSE DEVELOPMENT AT FAFA
ESTUARY. ..................................................................................................................................................... 140
10.9. APPENDIX I - MITIGATION MEASURES PROPOSED FOR THE IRRIGATION DEVELOPMENT AT THE
GOURITZ ESTUARY ....................................................................................................................................... 141
10.10.
APPENDIX J – MITIGATION MEASURES PROPOSED FOR THE SAPPI NGODWANA PULP AND PAPER
MILL, ELANDS RIVER .................................................................................................................................... 142
10.11.
APPENDIX K - PRELIMINARY BUFFER ZONE OUTCOMES CALCULATED USING CALCULATIONS
APPLIED IN THE DRAFT BUFFER ZONE MODEL UNDER A SUITE OF INPUT SCENARIOS. VARIABLES CHANGED
UNDER DIFFERENT SCENARIOS ARE INDICATED IN YELLOW. ........................................................................ 143
10.12.
APPENDIX L - REFINED BUFFER ZONE OUTCOMES BASED ON REVISIONS TO BUFFER ZONE
CALCULATIONS. VARIABLES CHANGED UNDER DIFFERENT SCENARIOS ARE INDICATED IN YELLOW. .......... 146
LIST OF FIGURES
Figure 1: Map showing the location of the Mt Moreland village where the wetland is situated along
the uMdloti River, just south of the KSIA........................................................................................ 8
Figure 2: Map showing the delineated “Froggy Pond” wetland at Mt Moreland and catchment area.
...................................................................................................................................................... 10
Figure 3: Photo showing the densely vegetated Phragmites australis reed bed associated with the
“Froggy pond” wetland at Mount Moreland, with wetland edges colonised by invasive alien
plants............................................................................................................................................. 11
Figure 4: Map showing construction phase buffer requirements for the Froggy Pond wetland at Mt
Moreland for Scenario A: Agricultural development (sugarcane). ............................................... 21
Figure 5: Map showing operational phase buffer requirements for the Froggy Pond wetland at Mt
Moreland for Scenario A: Agricultural development (sugarcane). ............................................... 22
Figure 6: Map showing construction phase buffer requirements for the Froggy Pond wetland at Mt
Moreland for Scenario B: residential development...................................................................... 25
Figure 7: Map showing operational phase buffer requirements for the Froggy Pond wetland at Mt
Moreland for Scenario B: residential development...................................................................... 25
Figure 8: Map showing the Hammarsdale wetland site, adjacent to the National Route 3 between
Drummond and Hammarsdale town, eThekwini Municipality, KZN. ........................................... 30
Figure 9: Photo showing the small “Hammarsdale wetland”, dominated by ...................................... 31
Typha capensis (bulrushes) and alien plants ........................................................................................ 31
Figure 10: Map showing the Hammarsdale wetland delineated above the tarred road. .................... 31
Figure 11: Map showing construction phase buffer requirements for the Hammarsdale wetland..... 37
Figure 12: Map showing operational phase buffer requirements for the Hammarsdale wetland. ..... 38
Figure 13: Location of the eSikhawini wetland ..................................................................................... 54
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Deliverable 11: Practical Testing / Field Testing Report
Figure 14 a and b: eSikhawini unchannelled valley bottom wetland with sugarcane and Eucalyptus
woodlots in the catchment ........................................................................................................... 55
Figure 15: Recommended core habitat for Pickersgill reed frog .......................................................... 57
Figure 16: The Sappi Ngodwana pulp and paper mill and effluent fields located adjacent to the
Elands River, Mpumalanga (25°34'43.92"S; 30°39'31.19"E). ....................................................... 58
Figure 17: The Elands River, Mpumalanga during base summer flows. Photo taken upstream of
activity site .................................................................................................................................... 61
Figure 18: The Sappi Ngodwana pulp and paper mill and effluent fields located adjacent to the
Elands River, Mpumalanga (25°34'43.92"S; 30°39'31.19"E) with buffer zones established in this
study superimposed...................................................................................................................... 63
Figure 19: The segment of the lower Thukela River, KwaZulu-Natal during base low flows that was
considered in the study. Scale bar represents 100m. (29°12'9.69"S; 31°25'28.54"E).................. 67
Figure 20: The Lower Thukela River, Mpumalanga during base summer flows. Photo taken upstream
of proposed activity site (Note the established woody vegetation on the right hand (south) bank
of the River (left of the photo)) which is proposed for development. ......................................... 69
Figure 21: The buffer zones proposed in this study to be established for the proposed dryland
sugarcane agriculture development and the Thukela River for both the north and south banks
of the river. The existing sugarcane plantation on the north bank is highlighted in the figure. .. 70
Figure 22: Fafa Estuary, situated along the south coast of KZN (red line indicates the 5 m contour .. 75
Figure 23: The north bank of Fafa Estuary illustrating coastal forest on the slopes and reeds and
sedges fringing the open water .................................................................................................... 76
Figure 24: Site based buffer requirements for Fafa Estuary. The supratidal zone is taken as the 5 m
contour line. .................................................................................................................................. 79
Figure 25: Location of the Gouritz Estuary indicating the development site (yellow polygon) in the
middle upper reaches; the estuary channel and 5 m contour line in blue. .................................. 87
Figure 26: Intertidal and supratidal salt marsh at the proposed development site which would occur
beyond the fence. ......................................................................................................................... 87
Figure 27: Vegetation map for the Gouritz Estuary. The proposed development will occur in
degraded floodplain. ..................................................................................................................... 88
Figure 28 A & B: Shows the topographical variability of the site; some areas have steep eroding
banks. ............................................................................................................................................ 88
Figure 29: Sensitive intertidal areas with eelgrass (Zostera capensis) exposed at low tide. ................ 90
Figure 30: Map indicating the recommended aquatic impact buffer zone for the proposed
development of irrigated agriculture along the banks of the Gouritz Estuary. ............................ 92
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Deliverable 11: Practical Testing / Field Testing Report
Figure 31: Responsively of the modelled buffer recommendations in response to variability in
climatic attributes ....................................................................................................................... 100
Figure 32: Responsively of the modelled buffer recommendations in response to variability in the
sensitivity of the receiving environment. ................................................................................... 101
Figure 33: Responsively of the modelled buffer recommendations in response to variability in sitebased buffer zone attributes. ..................................................................................................... 102
Figure 34: Variability in buffer zone recommendations across the full range of possible scenarios. 103
Figure 35: Graphs indicating the refinement to buffer recommendations in response to changes in
the range of sensitivity scores included in the model. ............................................................... 105
Figure 36: Graphs indicating changes to buffer zone recommendations in response to site-based
buffer zone attributes. ................................................................................................................ 106
Figure 37: Variability in buffer zone recommendations across the full range of possible scenarios. 107
LIST OF TABLES
Table 1: A summary of key comments and recommendations, and the project teams responses from
the first WRC development workshop............................................................................................ 2
Table 2: A summary of key comments and recommendations, and the project teams responses from
the second WRC development workshop....................................................................................... 4
Table 3: A summary of key comments and recommendations, and the project teams responses from
the SASQS workshop ....................................................................................................................... 5
Table 4: A summary of key comments and recommendations, and the project teams responses from
the NWI workshop .......................................................................................................................... 7
Table 5: Summary of buffer model outputs for the Froggy Pond wetland case study for Scenario A:
irrigated commercial cropland ...................................................................................................... 19
Table 6: Summary of buffer model outputs for the Froggy Pond wetland case study for Scenario B:
residential development ............................................................................................................... 22
Table 7: Summary of comments & concerns raised for the buffer model testing on the Mt Moreland /
Froggy Pond wetland .................................................................................................................... 26
Table 8: Summary of buffer model outputs for the Hammarsdale wetland case study ...................... 36
Table 9: Outcomes of the scenario evaluation for the Hammarsdale wetland case study .................. 39
Table 10: Summary of comments & concerns raised for the buffer model testing on the
Hammarsdale wetland .................................................................................................................. 45
Table 11: Outcomes of the initial scenario evaluation for the Hammarsdale wetland case study using
the updated wetland model. ........................................................................................................ 48
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Table 12: Buffer zone requirements calculated for a construction and operational phases of the Sappi
Ngodwana mill and associated infrastructure along the Elands River, Mpumalanga. ................. 62
Table 13: Outcomes of the scenario based evaluation of the Elands River. ........................................ 64
Table 14: Buffer zone requirements calculated for a construction and operational phases of the Sappi
Ngodwana mill and associated infrastructure along the Thukela River, Mpumalanga. ............... 70
Table 15: Outcomes of the scenario based evaluation of the Thukela River. ...................................... 72
Table 16: Buffer zone requirements calculated for a hypothetical golf course development alongside
Fafa Estuary in KwaZulu-Natal. ..................................................................................................... 78
Table 17: Outcomes of the scenario based evaluation of the Fafa Estuary (biodiversity sensitivity
scores excluded)............................................................................................................................ 80
Table 18: Summary of buffer model outputs for the Gouritz Estuary case study. ............................... 92
Table 19: Outcomes of the scenario evaluation for the Gouritz Estuary case study............................ 93
Table 20: Additional scenarios tested without the biodiversity sensitivity scores. .............................. 95
Table 21: Summary of comments for the buffer model testing on the Gouritz & Fafa estuaries. ....... 96
Table 22: Summary of issues / concerns & recommendations .......................................................... 107
LIST OF ACRONYMS
BZ
Buffer Zone
EFZ
Estuarine Functional Zone
EIS
Ecological Importance and Sensitivity
EMP
EWT
Environmental Management Plan
Endangered Wildlife Trust
GIS
GLV
Geographical Information System
General wastewater Limit Value
IFR
KSIA
KZN
In-stream Flow Requirement
King Shaka International Airport
KwaZulu-Natal
MAP
MAR
Mean Annual Precipitation
Mean Annual Runoff
PES
Present Ecological State
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Deliverable 11: Practical Testing / Field Testing Report
1. INTRODUCTION
This report is the eleventh deliverable in the Water Research Commission project K5/2200. Previous
deliverables for this project include:
1) A literature review;
2) A draft conceptual framework;
3) Minutes for the first stakeholder workshop and first steering committee meeting;
4) A revised conceptual framework;
5) A first draft of the method and model;
6) Minutes for the second steering committee meeting;
7) Minutes for the second stakeholder workshop and third steering committee meeting;
8) A revised draft of the method and model;
9) Draft guidelines for buffer zone management; and
10) Minutes for the third stakeholder workshop and fourth steering committee meeting.
The purpose of this report was to provide feedback on the practical testing of the buffer models
developed to determine appropriate buffer widths.
This discussion document will be shared with the reference group, technical peers and potential
implementing agencies. It will inform the revised version of technical report and the user manual.
2. APPROACH TO TESTING THE BUFFER METHOD
Approach to testing the method for determining appropriate buffer zones for developments
associated with wetlands, rivers and estuaries included:

Undertaking case studies to determine the effectiveness of the buffer model at determining
buffers for wetlands, rivers and estuaries;

Hosting development workshops to provide stakeholders with an opportunity to gain an
insight into the approach taken to develop the method for determining buffers for water
resources, and to provide them with an opportunity to actively contribute to the
development of the method and model; and

Undertaking a sensitivity analysis to establish the sensitivity of the model to changes in
parameters.
3. DEVELOPMENT WORKSHOPS
A series of workshops were held to provide stakeholders with an opportunity to:

Obtain feedback on the progress of the project;

Obtain insight into how the draft buffer models work; and

Provide feedback on the draft buffer models.
3.1. WRC Development Workshops
Two Water Research Commission (WRC) steering committee meetings were held in 2013. These
meetings provided an opportunity for the project team to present prototype buffer zone models to
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Deliverable 11: Practical Testing / Field Testing Report
the steering committee members and key stakeholders. Two development workshops were held on
the mornings before each of the steering committee meetings. The first development workshop was
held on the 26th of March 2013 and the second development workshop was held on the 17th of
September 2013 (minutes for each of these workshops are included in Appendix A and B
respectively). The findings from these workshops are highlighted below.
3.1.1.
First WRC development workshop
The first WRC workshop was hosted by Ian Bredin and Doug Macfarlane. The steering committee,
previous members of the steering committee and other key stakeholders were invited to participate.
The workshop included:

A presentation on the key aspects of the proposed method for determining appropriate
buffer zones for wetlands, rivers and estuaries that need to be taken into consideration for
the development of buffer guidelines;

A presentation on how the wetland buffer model works: A case study was used to illustrate
how the model works; and

A discussion session to provide participants an opportunity to comment on the proposed
approach and provide input into further developing the buffer methodology / models.
Table 1: A summary of key comments and recommendations, and the project teams responses
from the first WRC development workshop
KEY QUESTIONS / COMMENTS /
RECOMMENDATIONS
Will guidelines for defining different
types of developments be provided?
Are aspects such as soil, the landscape
and the flow of water within a
catchment taken into consideration
for determining a buffer zone?
Has the enforcement of the buffer
zone requirements been taken into
consideration?
RESPONSE FROM THE PROJECT TEAM / NOTES

Yes, there are guidelines provided which identify different sectors
and subsectors of a wide range of developments according to
available definitions.

Guidelines defining different types of developments will be included
in the User Manual.
Yes, the buffer model is designed to flag areas of concern. The model
allows for the risk to be identified. In addition, alternative mitigating
measures, other than buffer zones, would also need to be taken into
consideration to address impacts occurring in the catchments of water
resources.
It is important to remember that buffer zones are only one type of
mitigating measure. Appropriate alternative mitigating measures at
different stages of a development may provide more effective mitigation.
It was stressed that the development of buffer zones should be viewed as
a guideline as there may well be other more effective mitigating measures
that need to be considered. The Department of Water Affairs (DWA)
would also advocate the enforcement of justifiable site specific
requirements (i.e. establish what the risks are and identify what the
buffer zone should be according to the risks).
Have Ecological Water Requirements
(EWR) been taken into consideration?
The information required to be collected for a site-based assessment
starts to create links between critical components, which are important
for determining the EWR.
Does
The focus is on addressing impacts occurring adjacent to the edge of
the
buffer
model
address
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Deliverable 11: Practical Testing / Field Testing Report
KEY QUESTIONS / COMMENTS /
RECOMMENDATIONS
impacts occurring within a wetland?
RESPONSE FROM THE PROJECT TEAM / NOTES
wetlands, rivers and estuaries, and not in the water resources.

This concern has been identified by the project team. The limitations
of the desktop assessment will be clearly indicated. The project team
is considering adapting the model to indicate a recommended range
for buffer zones at a desktop level instead of a specific size. The
testing phase will confirm the effectiveness and limitations of the
assessments at the different levels.

Ensure the limitations of the desktop assessment are clearly indicated
in the User Manual.
Will a guideline to determine which
class each of the site-based modifier
aspects fall into be provided?

A guideline will be provided to assist the user in determining the
appropriate classes.

Ensure that guidelines are provided in each of the buffer models.
Does the model take into account the
type and density of vegetation in the
proposed buffer zone?
It takes into account basal cover. Both species composition and density
have a big impact on the functioning of the buffer zone. However, this is
where the management of the buffer zone becomes important.
Have cumulative impacts been taken
into consideration?
A conservative approach has been taken to address cumulative impacts,
in that in general the status quo would be required to be maintained.
However, this will all depend on the accuracy of the risks determined.
Assuming the risks are accurate, it would also be important that the
mitigation measures identified are undertaken correctly.
A general concern was noted
regarding the misuse of the desktop
assessment.
Shouldn’t the ‘time factor’ be taken
into consideration for determining the
effectiveness of the buffer zone and
other mitigating measures to address
the relevant impacts?

This is addressed to some degree through the sensitivity assessment
component of the model.

Consider providing guidance on the ‘time factor’ in the buffer models.
A concern was raised about the need
to address hydrology in more detail.
The model does flag areas, which can be used to identify other mitigating
measure that could be used to address hydrology concerns. Addressing
hydrology issues specifically is largely outside the scope of work for the
project.
Will soil type be used?
The focus will be on soil permeability and / or soil texture, which have
been identified as more important characteristics for determining buffer
zones.
Could the buffer tool be used for
rehabilitated wetlands?
The buffer tool could be used retrospectively. Therefore, it could be
applied to such circumstances.
3.1.2.
Second WRC development workshop
The second WRC workshop was hosted by Ian Bredin and Doug Macfarlane. The steering committee
and member of the Gauteng Wetland Forum were invited to participate. The workshop included:

A presentation on the key aspects of the proposed method for determining appropriate
buffer zones for wetlands, which need to be taken into consideration for the development of
buffer guidelines;

A presentation on how the wetland buffer model works. A case study was used to illustrate
how the model works; and
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
A discussion session to provide participants an opportunity to comment on the proposed
approach and provide input into further developing the buffer methodology / model.
Table 2: A summary of key comments and recommendations, and the project teams responses
from the second WRC development workshop
KEY QUESTIONS / COMMENTS / RECOMMENDATIONS
RESPONSE FROM THE PROJECT TEAM / NOTES
It was acknowledged by all participants that the models consider
a wide range of criteria, which are important for determining
buffer zones. While not all criteria are considered, it was agreed
that the focus should be on producing a method / model that
would allow for the guidance of management decisions, which is
based on the assessment of the majority of key criteria.
N/A.
The inclusion of soil data was recommended. The ARC land type
classification of soils was suggested as a possible option.
It was acknowledged that it would be important
to consider the surrounding soils. However, it
would be difficult to incorporate this information
into the existing model.
It was suggested that turbidity could be included, as this
determines the sensitivity of wetlands to sediment impacts.
Other criteria that may be worth investigating included: extent of
open water; sensitivity to vegetation to being submerged; and
vulnerability to erosion.

All of the other criteria mentioned are
considered in the wetland buffer model.

Consideration will be given to including
turbidity.
It was suggested by all that the model should try to find a link
between geographic constraints and buffer management.
Furthermore, it was stressed that the parameters used should be
specific for a specific management objective.
Agreed. This link is very important. While the
model takes into account geographical
constraints, management requirements will
equally be considered. These will be addressed in
the User Manual.
It was suggested that limitations of the model should be clearly
stated to prevent misinterpretation or misuse.
A section on limitations should be included in the
User Manual.
It was suggested that the buffer models should only be used by
qualified persons who have attended training on how to use the
models.
Guidance on the use of the buffer models will be
provided in the User Manual.

The active channel and / or the green line
will be used when determining the buffer
zone width for rivers. This was clarified
through consulting key riparian and aquatic
specialists.

Ensure that this is clearly described in the
technical report and User Manual.

Certain key drivers are
consideration in the model.

Guidance on other key drivers will also be
included in the model.
The use of either the macro channel or the active channel in
determining the buffer zone width for rivers needs to be clarified.
Important catchment aspects (especially flow) should be
considered, as understanding the catchment itself (i.e. drivers) is
paramount for guiding management decisions. The risks posed by
different landuses should only be considered once an
understanding of drivers has been attained.
taken
into
The use of indicator species should be considered.
Habitats and species of conservation concern are
taken into consideration.
It was stressed that it was critical that it be made clear that buffer
Ensure this is clearly stated in the models,
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KEY QUESTIONS / COMMENTS / RECOMMENDATIONS
RESPONSE FROM THE PROJECT TEAM / NOTES
zones are not appropriate for open cast mining and that this
should be clearly stated in the model.
technical report and User Manual.
Minimum buffer zones should be implemented to prevent
misapplication.
Agreed. A distance of 15m has been proposed
and will be investigated as part of the testing
phase.
The tool developed to aid in the selection of appropriate
alternative mitigating measures is useful. However, it must align
with current mitigating measures recommended in other
guidelines / policies being applied at a municipal and provincial
level.
The User Manual should make reference to this.
3.2. SASAQS Workshop
A workshop was hosted by Ian Bredin and Doug Macfarlane at the 2013 Southern African Society of
Aquatic Scientists (SASAQS) conference (the attendance register is included in Appendix C). The
workshop included:

A presentation on the key aspects of the proposed method for determining appropriate
buffer zones for wetlands, which need to be taken into consideration for the development of
buffer guidelines;

A presentation on how the wetland buffer model works. A case study was used to illustrate
how the model works; and

A discussion session to provide participants an opportunity to comment on the proposed
approach and provide input into further developing the buffer methodology / model.
Table 3: A summary of key comments and recommendations, and the project teams responses
from the SASQS workshop
KEY QUESTIONS / COMMENTS / RECOMMENDATIONS
RESPONSE FROM THE PROJECT TEAM / NOTES
Why is the buffer dependent on development? What if
the development changes? Perhaps consider basing
buffers on biophysical attributes instead.
The approach has been designed to align with the EIA
process and therefore threat of the development /
landuse is a key driver. Biophysical attributes are taken
into consideration. A buffer would need to be
determined for different developments.
What are you buffering the wetland for? Consider the
level of protection required for different targets e.g. Red
Data species in the wetland area.
Wetland is being buffered according to the threat of
the proposed development and the sensitivity of the
water resources. Core habitats requirements for Red
Data species are accounted for.
Functions of riparian zones need to be considered in the
river context e.g. is this for nutrient removal, sediment
etc.
The function of riparian zones has been taken into
consideration.
The design of buffers should be for sheet flow. Consider
the different types of flow i.e. are we going for an
ecological buffer or can it be artificial. Levelling
topography was suggested as this represents the best
Buffers will be designed according to the potential
lateral impacts of the proposed development. We are
advocating the development of an aquatic impact
buffer, which takes into consideration the existing
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KEY QUESTIONS / COMMENTS / RECOMMENDATIONS
RESPONSE FROM THE PROJECT TEAM / NOTES
flow and slope for a buffer. Vegetation considerations are
also linked to the flow e.g. tufts or grass-like vegetation
has a significant impact on the function of the buffer.
topography and vegetation.
How has landuse been incorporated? For example no
riparian zone due to farming. Is the buffered area the
source of the problem as it has been transformed? Does
the model consider or suggest rehabilitation?
Proposed landuse is a key driver in determining a
buffer. Transformed buffers may contribute to the
problem, which is why the management of the buffer
is important.
The concept of sacrificial areas. Has the study team
considered forgoing something else to preserve the main
wetland?
This is a management issue where the management
targets will determine what can be impacted to
preserve another system.
Add substratum type
infiltration) and slope.
Taking into consideration.
(affects
permeability
and
Do buffers have to be natural? Or can they be artificial?
How much is the project directed towards artificial
buffers?
Project is focused predominantly on natural buffers.
Artificial buffers are not excluded but this would need
to be considered as an alternative.
The tool must be able to help decision makers?
Agreed.
Do you bring in the different types of ecosystems and
their sensitivities?
Different types of water resources and their
sensitivities. Adjacent terrestrial sensitive ecosystems
are also considered.
Where exactly does the buffer start from?
For wetlands the edge of the temporary zone, for
rivers the edge of the active channel or ‘green line’,
and for estuaries the edge of the supertidal zone. For
rivers the riparian zone must be incorporated into the
buffer and for estuaries the 5m contour must be
incorporated as a minimum.
What is the approach that you have selected to deal with
extensive floodplain areas such as those in Limpopo? How
about using the 1:2 year flood line as suggested in an
earlier talk or the wet-bank edge?
Buffering large floodplains will be taking into
consideration.
Will this wetland buffer not cause confusion with existing
assessment and management structures?
If applied correctly it should not. The project clarifies
the linkages.
Include units to clarify just in case it gets lost down the
line.
Noted. Check model to ensure units are included
where relevant.
A concern was raised about the application of scientific
knowledge into government and whoever uses this
model.
It will be a recommendation that only SACNASP
registered specialists, who have received appropriate
training, should use the models.
Make sure that people do not take the desktop
assessment level as the standard.
Agreed, the limitation of the desktop assessment will
be clearly indicated.
What is the minimum buffer? How does this relate to the
30m buffer?
A minimum buffer is still to be determined.
Does the team get baseline/background data i.e. do you
check earlier assumptions about the wetland buffer?
The models will be tested. Baseline data from case
studies will be used.
How heavily does this model rely on other specialists?
Could this be a limiting factor if these experts do not
meet?
Specialist input is required for the biodiversity
component and the threat ratings for the proposed
development. Potentially, this needs to be assessed.
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KEY QUESTIONS / COMMENTS / RECOMMENDATIONS
RESPONSE FROM THE PROJECT TEAM / NOTES
Clearly define the limits of the model i.e. there are cases
where specialists cannot be replaced.
Agreed, limitations will be defined.
The model focuses a lot on water borne stressors, how
about air pollution? Particularly when you consider the
drift from pesticides, etc. Also consider noise pollution
and light pollution.
The model is only able to consider lateral impacts
occurring on the surface, neither airborne nor
subsurface.
For rivers, stream bank stability should be considered.
Noted. This will be taking into consideration.
The current buffer of 30m exists as a result of validation,
particularly for the practicality of the implementer.
Agreed, however this standard buffer has proven to be
problematic, which is why a site specific approach has
been advocated.
3.3. National Wetland Indaba Workshop
A workshop was hosted by Ian Bredin and Doug Macfarlane at the 2013 National Wetland Indaba
(NWI) (the attendance register is included in Appendix D). The workshop included:

A presentation on the key aspects of the proposed method for determining appropriate
buffer zones for wetlands, which need to be taken into consideration for the development of
buffer guidelines;

A presentation on how the wetland buffer model works. A case study was used to illustrate
how the model works; and

A discussion session to provide participants an opportunity to comment on the proposed
approach and provide input into further developing the buffer methodology / model.
Table 4: A summary of key comments and recommendations, and the project teams responses
from the NWI workshop
KEY QUESTIONS / COMMENTS / RECOMMENDATIONS
RESPONSE FROM THE PROJECT TEAM / NOTES
The proposed approach to developing buffer zones does
not take into consideration the alteration of flows.
While the alteration to flows and patterns does not
influence the buffer, the model does identify these as
important criteria that must be given consideration (i.e.
alternative mitigating measures would need to be
considered).
The scale and the timing of impacts need to be taken into
consideration.
Agreed. Scale and timing of impacts will be identified as
criteria that need to be considered when determining
buffer requirements.
What about including wetland type at a desktop level?
Wetland type may need to be confirmed infield and
therefore it is not appropriate for a desktop assessment.
Consideration needs to be given to the long-term
ownership / management of the buffer zone.
Agreed. The management of the buffer zone is just as
important as determining an appropriate correct buffer
width. Management of buffers is addressed in the
technical report and will be included in the User Manual.
Seasonal changes to the characteristics of the buffer zone
should also be considered. Basal cover is a key
characteristic, which may vary between seasons.
Guidance on considering seasonal changes will be
considered and where relevant included in the User
Manual and the appropriate models.
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KEY QUESTIONS / COMMENTS / RECOMMENDATIONS
RESPONSE FROM THE PROJECT TEAM / NOTES
In terms of forestry, buffer zones will not be able to
mitigate against the impact on hydrology from timber in
the greater catchment.
Agreed.
Does the model cater for wetland rehabilitation?
Buffers are determined for developments / landuses
adjacent to water resources, not activities taking place
within the resource. However, it would be possible to
determine a buffer retrospectively for the rehabilitation
of a wetland.
The buffers models should factor in the size of a particular
development.
Agreed. The model will provide guidance for the user to
adjust threat scores for developments of varying sizes.
4. WETLAND CASE STUDIES
4.1. Mount Moreland Wetlands – Froggy Pond
Doug Macfarlane and Adam Teixeira-Leite applied the model to the “Froggy Pond” wetland case
study, located at Mount Moreland, within the eThekwini Municipality, KwaZulu-Natal (KZN).
4.1.1.
Site description
The “Froggy Pond” wetland is located next to the uMdloti River on the KZN north coast, mid-way
between the urban centres of Verulam in the west and the coastal town of La Mercy in the east
(Figure 1), at approximately 290 38’ 32” S ; 310 51’ 20” E. The wetland is situated adjacent to the
“Mount Moreland village”, with the recently constructed King Shaka International Airport (KSIA)
located in the wetland catchment area in the north.
N2
freeway
Figure 1: Map showing the location of the Mt Moreland village where the wetland is situated
along the uMdloti River, just south of the KSIA
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The wetland is located within the Indian Ocean Coastal Belt bioregion of South Africa (Mucina &
Rutherford, 2006) with the landscape characterized by rolling hills and large river valleys, with the
local elevation at the wetland ranging between 6 and 25 m.a.s.l. The coastal region of KZN has been
subject to extensive transformation, with local land use in the area comprising mainly agriculture in
the form of commercial sugarcane farming under Tongaat Huletts, with infrastructure associated
with the residential area at Mt Moreland and the recently constructed KSIA to the north of the site.
Few areas of remaining indigenous forest, bushland and grassland characterise the area and are
mainly confined to river courses and steep vegetated slopes and drainage lines.
The local climate is characteristic of the subtropical climate in KZN, with generally warm, wet
summers and cool, dry winters. The site falls within Rainfall Intensity Zone 4 (high) characterized by
a mean annual precipitation of 983.2mm (MAP class: 801 – 1000mm) and a much lower mean
annual potential evapotranspiration rate of 247.3mm. This gives a MAP to PET ratio of 3.9
(vulnerability index of 0.9), which means that the wetland is moderately sensitive to hydrological
impacts (i.e. changes in water input volumes and patterns).
4.1.2.
Description of the wetland
The wetland known locally as “Froggy Pond” forms the eastern arm of a larger wetland system that
divides around a steep ridge upon which the Mt Moreland residential community is situated (Figure
2). Froggy Pond wetland is approximately 19ha in extent (6% of the catchment area) and is primarily
an unchannelled valley bottom wetland with flow being predominantly diffuse within the wetland.
The unchannelled nature of the valley bottom wetlands can be related to sufficiently low/diffuse
flow through the system and a supply of clastic sediment that is essentially high enough such that
longitudinal gradient is maintained. This high supply of clastic sediment would essentially limit
organic sedimentation within the system. The wetland is fed by a simple dendritic drainage network
consisting of steep coastal bedrock streams and small rivers. The streams and rivers are fed by rain
and storm water runoff as well as by auxiliary irrigation inputs from agriculture (numerous smallvegetated drainage lines feeding primary channels) and seepage from the valley sides. At the base
of the wetland, an artificial drain has been constructed and conveys water to the uMdloti River.
A large portion of the upper reaches of the catchment has been subject to considerable
transformation as a result of the development of KSIA and associated infrastructure. Storm water
now runs off the airport via an attenuation dam into the stream that feeds this wetland. A waste
water treatment works is also located upstream and is likely to contribute excess nutrients into the
wetland. Whilst some semi-natural and invaded vegetation occurs in the catchment, sugarcane
dominates much of the catchment with residential areas occurring directly west of Froggy Pond
wetland. Soils within the wetlands catchment are relatively sandy and considered erodible, posing a
threat to existing aquatic resources.
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Figure 2: Map showing the delineated “Froggy Pond” wetland at Mt Moreland and catchment
area.
The wetland is considered relatively diverse from a vegetation perspective. A large central
Phragmites australis reed bed is a primary feature of this wetland, where herbaceous vegetation in
the reed bed floats on the water surface, forming large floating mats where water depths are
typically deep (>1.5m) during both the summer growing and winter resting seasons (see photo
below). Cyperus latifolius/Cyperus dives and Typha capensis mixed marsh characterises the shallow
water areas in the southern and eastern sections of the wetland that are saturated to inundated
through most of the growing season. Lack of burning (and possible re-direction of flows through
channel incision/drainage) appears to be responsible for leading to a loss in vigour of some of the
wet meadow areas which have become colonised to varying degrees by a range of alien plant
species, the dominant ones including Solanum chrysotrichum, Cestrum laevigatum, Senna
didymobotrya and Canna glauca. Areas along the influent stream line and along the perimeter of the
wetland are also dominated by more terrestrial and alien invasive species such as Melia azedarach,
Solanum mauritianum, Schinus terebinthifolius, Chromolaena odorata and Lantana camara.
Encroachment by woody terrestrial and exotic species along the margins is evident in some places.
In addition, the upper and lower reaches of the system have been extensively drained and are
currently used for the cultivation of sugarcane.
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Figure 3: Photo showing the densely vegetated Phragmites australis reed bed associated with the
“Froggy pond” wetland at Mount Moreland, with wetland edges colonised by invasive alien plants
The current state of wetland integrity is regarded as being Moderately Modified (C Class) overall,
based on the WET-Health (Macfarlane et al., 2007) assessment undertaken. Hydrological and
geomorphological functioning has been moderately modified by catchment activities including
sugarcane farming and the recently constructed KSIA which has altered the natural hydrological
regime of the wetland to a large degree. Wetland vegetation integrity varies across the wetland unit
but is generally considered to be moderately modified. Although large sections of wetland habitat
remain largely natural (i.e. main reed bed and seasonal marsh areas), the upper and lower sections
of the wetlands have been drained and planted to sugarcane, with a significant degree of
encroachment by terrestrial and exotic woody vegetation in these areas and also along the wetland
margins.
In terms of ecological functioning, the wetland functions well at removing toxicants, nutrients and
trapping sediment (based on records of water quality sampled at the inflow and outflow points of
the wetland over a 3-4 year period) and is also considered important in controlling erosion and
attenuating flood waters. The broad wetland reed bed and Cyperus marsh habitat is also considered
important in terms of the maintenance of biodiversity, with the threatened Red data frog species
Hyperiolius pickersgilli (Pickersgill’s reed frog) occurring at the site, in addition to other endangered
frog species, reptiles and birds. Thousands of European Barn Swallows (Hirundo rustica) use the
dense reed bed as a seasonal migration and roosting site, attracting tourists to the Mount Moreland
area over the summer months. In terms of wetland EIS (Ecological Importance & Sensitivity), the
Froggy Pond wetland is regarded as having a Medium-High EIS rating, although at a finer-scale,
individual sections of the wetland system have been rated differently based on the variability in
wetland habitat condition and known locations within the wetland used by species of conservation
concern. The main Phragmites reed bed and Cyperus mixed marsh areas, for example, are
considered to be of High Ecological Importance and Sensitivity owing to their high level of ecological
integrity and ecological value from a biodiversity and functional perspective (harboring
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threatened/important species). Areas of invading swamp forest, alien infested marsh and drained
wetland areas planted to sugarcane are rated as Low to Medium (EIS) due to the disturbed state of
wetland habitat in these areas.
4.1.3.
Outcomes of field testing
4.1.3.1.
Level of assessment
The “Site-based” level of assessment was selected for the Froggy Pond/Mount Moreland wetland
study, which was informed by previous site visits and verification of the wetland and catchment area
by a specialist wetland ecologist familiar with wetland delineation and functional assessment
techniques and methods.
4.1.3.2.
Proposed development scenario(s)
Two development scenarios were considered for testing the buffers model on the Froggy Pond
wetland at Mount Moreland. These included:
Scenario A: Agricultural land use
Under this development scenario, sugarcane farming would be proposed for the catchment area and
areas immediately adjacent to the wetland area (see extent in Figures 4 & 5). Typical ecological
impacts/threats to the wetland resource would probably include:

Sedimentation as a result of bare stripped soils/tillage;

Increased nutrient and salt levels from fertiliser/manure application;

Altered catchment hydrology (flow volumes and timing of water inputs) as a result of
sugarcane cultivation;

Disturbance of wetland edges and increased threat of alien plants colonising wetland
habitat; and

Visual and noise disturbance impacts on biodiversity (fauna).
Scenario B: residential development
Under this development scenario, an extension of the existing Mount Moreland village is planned
and would primarily involve the construction of additional formal residences along the eastern ridge
of the Mount Moreland community (i.e. along the section close to the western edge of the Froggy
Pond wetland (see extent in Figures 6 & 7). Typical ecological impacts/threats to the wetland
resource would probably include:

Sedimentation mainly during construction phase;

Altered hydrology (flow volumes and timing of water inputs) as a result of an increase in
hardened surfaces;

Disturbance of wetland edges and increased threat of alien plant colonising wetland
habitat;

Risk of accidental waste water discharge from conservancy tanks associated with new
houses (no piped sewage system at present); and

Visual and noise disturbance impacts on biodiversity (fauna).
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The Sector selected in the buffer tool was the “Agriculture” type for Scenario A: Sugarcane farming
and the “Residential” type for Scenario B: Residential development. Sector selection for these two
scenarios was straight forward with no ambiguity posed by the model. In terms of Subsector type
selection, the “Irrigated commercial cropland” type for Scenario A: Sugarcane farming and the
“Residential Low impact / Residential only” type for Scenario B: Residential development. Subsector
selection was also straight forward with a relatively low level of ambiguity.
Mount Moreland “Froggy Pond” wetland
Scenario A
Scenario B
Sector
Agriculture
Residential
Subsector
Irrigated commercial cropland
Residential Low impact / Residential only
Note that potential threats/impacts to wetlands related to the KSIA have not been dealt with in this case study.
4.1.3.3.
Preliminary threat ratings and buffers
Scenario A: Irrigated cropland (sugarcane)
Under development Scenario A (sugarcane farming in the catchment), preliminary/desktop threat
ratings for the subsector selection “irrigated commercial cropland” indicate that anticipated
construction impacts (i.e. associated with tillage and land preparation) are likely to be variable, with
a High threat rating for sedimentation and nutrient inputs. This is a reasonably fair reflection of the
potential threat as a result of tillage and the use of fertiliser whilst preparing land for planting of
crops. Under the specialist threat rating, however, the threat of sedimentation during construction
was increased from a High to a Very High level as sediment is likely to be most problematic impact
during the stripping of areas and tillage (when soils are left bare and most at risk of runoff erosion).
The risk of toxic contaminants was estimated to be Moderate which is a fair estimate for agricultural
activities involving limited use of machinery/chemicals, etc. Alterations to hydrology (flow volume
and timing) are likely to be a low-moderate level threat at this stage of the activity, which is
accurately reflected in the desktop rating.
In terms of operational phase impacts (i.e. associated with growing of sugarcane, irrigation and
harvesting operations), a High threat rating was once again provided for sedimentation and nutrient
inputs, which is likely to remain an issue even during operation (continued use of fertiliser,
transportation of sediment to downstream areas as a result of drain construction and general soil
disturbance that could result during crop harvesting). Under the specialist threat rating, the threat of
sedimentation during operation was maintained as “High” as areas are likely to have been stabilised
once planted and pose less of a risk of erosion/sedimentation than during stripping/tillage.
Alterations to the timing of flows are likely to be significant during operation with artificial drains
(typically associated with sugarcane production), potentially concentrating flows to downstream
areas. This threat was appropriately reflected in the model.
Converting natural areas to cropland is also likely to alter the volume of water reaching the
downstream wetland as research has shown that crops such as sugarcane are generally fast-growing
and utilise significantly higher quantities of water than natural vegetation. This is reflected by the
“High” threat rating provided by the model. The only threat that could potentially be
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underestimated is pathogen inputs. Some sugarcane farmers are known to use animal/chicken
manure to fertilise their fields and in these instances, there would probably be a risk that E.coli levels
for example could increase in the water column reaching the wetland. Under the specialist threat
rating, the threat for pathogen inputs was therefore adjusted upwards from a Very Low level to a
Moderate level to account for this potential risk. Although the desktop threat ratings provide an
early indication of potential impacts, with most providing threat ratings that are meaningful,
some desktop ratings required adjustment by the wetland specialist based on a specific
understanding of planned activities. This highlights the importance of reviewing generic threat
ratings based on the specifics of a particular development activity.
Desktop buffer requirements provided by the model (based on the agricultural development – worst
case scenario) suggest a 74m and 99m buffer zone for construction and operational phases
respectively. The implication is that agriculture has a potentially significant impact on water
resources and that planning should reflect this by buffering wetlands by 100m in the absence of
more detailed information about the site or receiving water resource. It is also useful that the buffer
model highlights alteration of flow volumes and patterns as high risks which would need to be
carefully considered as part of any land use application process.
Scenario B: low impact residential development
At a desktop level, buffer requirements for residential development (worst case) are lower than for
agriculture with desktop buffer requirements indicating that buffers of 50m would be required for
construction (linked to sediment risk) and 74m for operation (linked to nutrient risks). This is
regarded as appropriately conservative for desktop planning purposes.
Under the specific development Scenario B (residential development at Mt. Moreland village),
preliminary/desktop threat ratings for the subsector selection “Residential Low impact / Residential
only” indicate that most anticipated construction impacts are likely to be Very Low, with a Medium
threat rating given for sedimentation impacts. This is a fair reflection of the potential threat level for
impacts that could be associated with the single-stand type developments. Site-specific information
pertaining to the nature of the receiving environment (sensitivity of the water resource) and
characteristics of the land between the development and the wetland (i.e. soil types, slope,
vegetation cover, etc.) will obviously modify these initial desktop threat ratings in this case.
In terms of operational phase impacts, these are generally rated as Low/Very Low at a preliminary
desktop level in terms of potential threat level, with altered flow volumes being rated as Moderate.
This is probably a reasonably fair reflection of the level of threat generally posed by residential
developments. Potential nutrient/bacterial inputs from residential areas (e.g. from septic tanks, etc.)
and associated contamination of groundwater are not specifically accounted for. There is therefore
a risk that impacts not specifically listed (another being point-source discharges) may not be
appropriately detected if this tool is used as a surrogate for impact identification and assessment.
There is therefore a need to consider this carefully when compiling guidelines / making
refinements to the model.
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It is also important to note that some developments may be phased or include a number of
different activities that would require the assessment of a number of different sub-sectors. This is
typical of residential areas where other infrastructure may be planned as part of the application. A
typical example would be the construction of additional parking areas which may pose greater risks
to the resource. Here, it would be useful to have some guidance on how this would be addressed.
Providing further clarity on the typical size / scale of development used in assigning initial threat
ratings would be useful to inform refinements to the threat ratings for small projects. Perhaps
assuming a footprint that would extend 100m upslope from the water resource would be a useful
starting point.
There is also a chance that the desired landuse during “operation” would change from natural
vegetation to maintained lawns / gardens in the case of residential areas. This impact should also
ideally be considered when setting EMP requirements for subsequent landuse and management.
Desktop buffer requirements provided by the model (based on the “Residential Low impact /
Residential only” scenario suggest a 15m buffer zone for construction. While it is understood that
the model should not be applied in this manner (without considering sensitivity and site-based
factors), there is a risk that this will be applied at a desktop level.
4.1.3.4.
Sensitivity assessment
The sensitivity assessment undertaken for the site was relatively easy to follow, with guidance and
rationale provided for each criterion to direct the user’s allocation of sensitivity ratings. The outputs
of the sensitivity assessment highlight that the wetland is moderately sensitive to most
threats/impacts, with sensitivity to sedimentation, altered water acidity, temperature changes and
pathogen inputs regarded as rather low. This is probably a fairly accurate reflection of the sensitivity
and resilience typically associated with densely vegetated, unchannelled systems.
The overall sensitivity class of the wetland does increase, however, due to the presence of
sensitive/ecologically important biodiversity features associated with the Froggy Pond system,
including the Critically Endangered Pickersgill reed frog (Hyperolius pickersgilli) which is present in
the seasonal-permanent Cyperus mixed marsh in the eastern sections of the wetland. Of importance
is also the presence of European Barn swallows (Hirundo rustica) for half of the years, which migrate
from the northern hemisphere and roost in the dense Phragmites reed bed. The biodiversity
sensitivity class ratings were therefore rated based on existing knowledge of the type and
abundance of sensitive species occurring at the site. The Critically Endangered frog species in
particular are known to be sensitive to changes in water quality and habitat, thus water quality
threats were rated as High to Very High in terms of biodiversity sensitivity. Alterations to nutrients
and flow volumes which could potentially result in changes in habitat were also rated as High, as
these impacts could affect habitat-specific sensitive species. The combined sensitivity class
outputted by the model, which takes into account both the sensitivity of the resource and
biodiversity aspects, provides a far better reflection of the sensitivity of the Froggy Pond wetland
system and its biodiversity components. This serves to highlight the need for specialist biodiversity
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input for important wetland ecosystems and also indicates the risk of misapplication of the model
unless undertaken by a well-trained and independent specialist.
Overall, the sensitivity assessment was found to be quick and easy to run through, with only a few
criteria where selection of ratings required further specialist interpretation to decide on ratings.
There is also a danger that wetland sensitivity can be over- or under-estimated. This is due to the
fact that some systems (such as the Froggy Pond wetland) may be spatially variable in terms of the
sensitivity of vegetation/habitat and biodiversity (species). In the case of the Froggy Pond wetland,
some sections of the wetland are considered more ecologically sensitive/important than others, and
there is a risk that large buffers could be proposed for areas of degraded habitat that are not
considered ecologically sensitive/important. In this instance the sensitivity assessment could be
applied to spatially explicit sections of the wetland rather than the entire unit as a whole, yielding
a variable buffer result applied to sections of the system rather than the whole unit.
4.1.3.5.
Site-based modifiers
Rating site-based modifiers based on the site-specific characteristics of the terrestrial buffer around
the wetland was relatively easy for this site as the catchment area around the wetland is relatively
homogenous (steep slope, moderate-high vegetation cover). The main areas where major variation
around the wetland needed to be accounted for were where the drainage lines enter the system (i.e.
concentrated flow paths). Ideally, any drainage lines or concentrated flow paths outside of the
recommended buffer zone would also need to be buffered to reduce risks of
sedimentation/pollution to downstream areas. This should be catered for through the river/stream
buffers model.
A concern with the current model though, is that it does not specify whether the operational or
construction buffer should be applied to inform planning (the maximum preliminary buffer
requirement for the construction phase was used in this case). In the case of agriculture, the
maximum buffer should clearly be used as once established, agricultural lands will continue to be
used. The issue is a little more obscure where a construction buffer is large but the operational
buffer requirement is small. Perhaps clearly indicating that the maximum buffer zone width should
be used would be worth including.
This issue should be easy to address by providing appropriate guidance when applying the model.
Another issue requiring clarification and further consideration is how the sensitivity modifiers are
calculated. At this stage, it is based on a weighted average of scores across the different components
assessed. Further investigation of the sensitivity of model outcomes to responses cited in empirical
studies would be useful in tweaking this component of the model.
4.1.3.6.
Species of conservation concern
In this particular case, the Critically Endangered Pickersgill’s reed frog (Hyperolius pickersgilli) is
known to occur at the site. The following extract on buffer recommendation has been extracted
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from a report by Jeanne Tarrant (EWT) and provides an indication of the nature of advice on buffers
that could be expected with specialist input:
“For all amphibian species, as well as considering core breeding habitat (in this case reed bed
wetlands), it is also crucial that terrestrial habitat surrounding breeding habitat is conserved. Most
amphibian species make use of terrestrial habitat surrounding wetlands, with almost 60% of species
moving beyond 60 m of the wetland (Boyd 2001). Terrestrial wetland buffers provide important core
habitat for wetland-dependent species for life history processes including foraging, dispersal and
aestivation during the non-breeding period, as well as a number of functional capacities such as
maintaining filtration processes and pollution attenuation that protect water resources (Semlitsch &
Bodie, 2002). Adverse disturbance of wetland buffers can result in changes to the biological, physical
and chemical properties and lead to a reduction in wetland function (Boyd 2001). Terrestrial buffers
are therefore vital for maintaining diversity and should be managed together with the aquatic
habitat.
Terrestrial buffers of up to 400m are recommended in the literature for wetland-dependent frogs
(Semlitsch & Bodie, 2002; Ficetola et al. 2008). Based on these recommendations, and on
distribution records of H. pickersgilli up to 1.2km away from wetland habitat, the following is
recommended:

A buffer of up to 250m, is established around wetland areas in which H. pickersgilli is
present.

Connectivity between wetlands is established and maintained through the proposed buffer
zones.”
In the case of this site, recommendations could be further refined by targeting areas of intact habitat
and perhaps relaxing requirements where significant transformation through sugarcane cultivation
has occurred. What is clear however is that requirements associated with species of conservation
concern can easily override aquatic impact buffer requirements.
4.1.3.7.
Additional mitigation measures
Additional mitigation measures for Scenario A: Irrigated cropland (sugarcane)
In addition to buffer requirements, a range of additional mitigation measures have been
recommended for the site (Appendix E). While these may help to reduce risks somewhat,
justifications were not regarded as sufficient to alter buffer requirements.
Additional mitigation measures for Scenario B: low impact residential development
In addition to buffer requirements, a range mitigation measures have been recommended for the
site. These measures were deemed necessary and relevant to deal with some of the site specific
ecological concerns likely to arise during the construction and operation phases of the proposed
development, which buffer zones in isolation are unlikely to mitigate adequately. These included:

Increased sediment inputs as a result of bulk earthworks near wetlands during construction;
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
The potential for further alien plant infestation of wetland areas and buffers following
disturbance;

Relatively steep sided valley prone to soil erosion (sandy-clay soils on shale bedrock are
considered erodible within the context of steep slopes and potential concentrated water
flows);

Potential for input of nutrients and pathogens from failing septic systems; and

Altered runoff characteristics as a result of increased hardened surfaces associated with
planned housing development.
Mitigation measures concentrated on erosion/sedimentation and flow alteration risks which were
highlighted by the buffers model as being of particular concern during both the construction and
operational phases of the residential development activity. In addition, generic mitigation measures
to deal with potential toxicants/contaminants arising during construction activities and possible
waste water contamination from septic tank systems were also recommended. The specifics
regarding mitigation measures that have been proposed for the site are documented in Appendix F.
Assuming that the mitigation and management measures proposed will be applied to the site,
refined threat classes were assigned to each impact type as per the table in Appendix F. Major
refinements to threat classes included:

Reducing the threat class from a Medium class to a Low class for patterns of flow during
construction. Provided on-site attenuation of flows takes place successfully and
consistently, this impact can be reduced to a low risk level.

Reducing the threat class from a Very High class to a High class for sedimentation &
turbidity risks during construction. Although on-site mitigation is likely to reduce this risk
somewhat, the risk of these impacts to wetland areas remains high due to the
characteristics of the site (steep slope, erodible soils).

Reducing the threat class from a High class to a Low class for patterns of flow during
operation. Provided on-site attenuation of flows takes place successfully and consistently,
this impact can be reduced to a low risk level.

Reducing the threat class from a High class to a Medium class for sedimentation & turbidity
risks during operation. On-site mitigation is likely to reduce this risk to a large extent, with a
moderate risk remaining as a result of the inherent characteristics of the site (steep slope,
erodible soils).

Reducing the threat class from a Medium to a Low level for increased toxic contaminants
reaching water resources through on-site mitigation and management of toxic
substances/wastes.
4.1.3.8.
Outcomes of the buffers model
Buffer outcomes for Scenario A: irrigated cropland (sugarcane)
Outcomes of the buffers model applied to the Mt Moreland “Froggy Pond” wetland for Scenario A
(irrigated cropland) are summarised in Table 5. The construction and operational phase buffer
requirements are also shown spatially in Figures 4 and 5, respectively.
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During the construction phase (preparation of land for cultivation), the risk of sedimentation
associated with soil erosion/disturbance of soils, and the potential increase in nutrient inputs from
fertilisers/manure are clearly the greatest threat posed to the wetland system downstream of
proposed agricultural activities. A 74m buffer was flagged in the buffers model for the construction
phase based on potential sediment threats and the nature of the potential buffer zone (steep slope,
erosion prone soils).
Whilst the sensitivity assessment of the wetland suggested that the wetland was moderately
sensitive to nutrient inputs, frogs (and associated habitat) may be more sensitive which resulted in
an increase in the risk rating for nutrient inputs. Taking biodiversity sensitivity into account resulted
in a considerable increase in buffer requirements to address potential nutrient risks. This
requirement was increased further when taking the steep slope and other buffer zone
characteristics into account. The model therefore suggests that a 61m buffer zone would be
required based on local site attributes. If this assessment was being undertaken for a
development, we would investigate the real threat of nutrients further to see if a case could be
made to reduce this threat rating which effectively drives the need for wide buffer requirements in
this case. Given the importance of this threat rating, there is a clear need to ensure that it is
appropriately motivated / justified.
Table 5: Summary of buffer model outputs for the Froggy Pond wetland case study for Scenario A:
irrigated commercial cropland
BUFFER
RECOMMENDATIONS
Desktop buffers
(Sub-sector)
Site-based buffers
CONSTRUCTION
BUFFER WIDTH
(M)
74
(44)
59
OPERATION
BUFFER
WIDTH (M)
99
(44)
61
COMMENTS
Desktop buffer requirements appear to be appropriately conservative
in attempting to mitigate risks of erosion/sedimentation and
increased nutrient inputs, given typical soil disturbance associated
with agricultural activities. It could however be argued that the threat
of sedimentation during construction should be rated as very high
rather than high due to the exposure of large areas during land
preparation.
The importance of refining desktop threat ratings is well illustrated in
this case study where, for example, application of manure would
significantly increase pathogen risks above that noted in the desktop
rating. A range of sustainable farming practices could also be
implemented to reduce these threats.
The tool provides
opportunities to refine these ratings up-front or through the inclusion
of mitigation measures to reduce the threat score.
Whilst the sensitivity assessment provides a useful basis for
differentiating between the sensitivity of wetlands to various impacts,
further guidance on its application is required.
A specific
recommendation is to sub-divide the wetland into different
sensitivity classes if wetland characteristics are sufficiently different
across the area being assessed. This could add significantly to the
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BUFFER
RECOMMENDATIONS
CONSTRUCTION
BUFFER WIDTH
(M)
OPERATION
BUFFER
WIDTH (M)
COMMENTS
ease of applying this tool however.
Desktop buffer requirements were reduced slightly when taking the
moderate-high sensitivity of the wetland resource and the site-based
modifiers (largely associated with the steep slope, reduced ground
cover and presence of erodible soils) into account. In the absence of
other forms of mitigation, a well vegetated buffer of 61m is
advocated. Given known efficiencies of buffers of this size in
attenuating sediment and nutrients, this recommendation is probably
appropriate for a system with very sensitive biota.
If this assessment was being undertaken for a development, we would
investigate the real threat of nutrients further to see if a case could be
made to reduce this threat rating which effectively drives the need for
wide buffer requirements in this case. Given the importance of this
threat rating, there is a clear need to ensure that it is appropriately
motivated / justified.
When habitat requirements for the Pickersgill reed frog are
considered, restriction zones would need to be increased
considerably (with a generic 250m buffer providing an indication of
potential implications).
Final buffer widths have not differed from the site-based buffer
recommendations as it was felt that mitigation of impacts associated
with agricultural development would be difficult to implement and
would not contribute significantly to reduced threat ratings for key
impacts identified.
Final buffers
59
61
Applying the recommended maximum final buffer zone of 61m shows
areas of existing sugarcane within the buffer zone, often right up to
the wetland boundary. This suggests that existing sugarcane activities
are likely to have a negative impact on the Froggy Pond wetland and
should ideally be removed to ensure the appropriate protection of the
wetland.
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Figure 4: Map showing construction phase buffer requirements for the Froggy Pond wetland at Mt
Moreland for Scenario A: Agricultural development (sugarcane).
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Figure 5: Map showing operational phase buffer requirements for the Froggy Pond wetland at Mt
Moreland for Scenario A: Agricultural development (sugarcane).
Buffer outcomes for Scenario B: low impact residential development
Outcomes of the buffers model applied to the Mt Moreland Froggy Pond wetland for Scenario B
(residential development) are summarised in Table 6, below whilst construction and operational
phase buffer requirements are shown in Figures 6 and 7, respectively.
During construction, the risk of sedimentation associated with soil erosion is clearly the greatest
threat that development would pose to the wetland system. This threat has been highlighted as
possibly the greatest cause for concern with regards to the impact on wetland areas. A 15m buffer
was flagged in the buffers model for the construction phase based on potential sediment threats and
the nature of the potential buffer zone (steep slope, erodible soils). The model suggests this could be
reduced to 10m if additional mitigation measures are implemented.
Table 6: Summary of buffer model outputs for the Froggy Pond wetland case study for Scenario B:
residential development
BUFFER
RECOMMENDATIONS
Desktop buffers
(Sub-sector)
CONSTRUCTION
BUFFER WIDTH
(M)
OPERATION
BUFFER
WIDTH (M)
50
(15)
74
(3)
COMMENTS
Desktop buffer requirements are appropriately conservative (74m)
when the worst-case sub-sector is chosen. If the sub-sector is
selected, buffer widths (15m) for the construction phase are not
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BUFFER
RECOMMENDATIONS
CONSTRUCTION
BUFFER WIDTH
(M)
OPERATION
BUFFER
WIDTH (M)
COMMENTS
considered large enough to mitigate risks of erosion and
sedimentation, due to the steep nature of slopes at the site and
potential concerns of increased runoff volumes/velocities. To cater for
this risk, worst-case site modifiers could be applied. This would result
in more conservative desktop buffers which are advocated at the
desktop assessment stage.
A concern was also raised that there is a risk that impacts not
specifically listed (e.g. groundwater contamination & point-source
discharges) may not be appropriately detected if this tool is used as a
surrogate for impact identification and assessment. There is therefore
a need to consider this carefully when compiling guidelines / making
refinements to the model.
Another issue raised is that some developments may be phased or
include a number of different activities that would require the
assessment of a number of different sub-sectors.
This is well
illustrated in this case study where parking areas may also be planned
or where a garden / lawns may be created within the “buffer zone”
following construction. The impacts of such activities should also
ideally be assessed and buffers established appropriately.
Providing further clarity on the typical size / scale of development
used in assigning initial threat ratings would also be useful to inform
refinements to the threat ratings for small projects. Perhaps
assuming a footprint that would extend 100m upslope from the water
resource would be a useful starting point. Other factors such as slope
can also have a significant effect on threats. Guidance on what site
attributes should be considered when defining specialist threat
ratings should therefore be provided.
Site-based buffers
21
9
Buffer width was reduced considerably when taking the moderate
sensitivity of the resource and the site-based modifiers (largely
associated with the steep slope and presence of erodible soils) into
account. In the absence of any other form of mitigation, a 21m buffer
by itself (no other forms of mitigation) downslope of a steep erodible
slope probably won’t provide a very high level of protection from
erosion and sediment impacts as runoff velocities could potentially be
high.
This issue could be resolved by adjusting the score for soil properties
and topography of the buffer up to better account for local erosion
risk could also provide a more appropriate outcome. Doing so, would
increase buffer requirements to 24m and 11m, for construction and
operational phases respectively, which is not a significant increase.
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BUFFER
RECOMMENDATIONS
CONSTRUCTION
BUFFER WIDTH
(M)
OPERATION
BUFFER
WIDTH (M)
COMMENTS
Provided the buffer zone is appropriately managed (well-vegetated, no
concentrated flow paths, etc.), a relatively small 21-24m buffer could
provide for sufficient mitigation of sediment risks vegetated (research
suggests that even a 15m buffer is likely to be 80% effective in
trapping sediment).
A concern was also raised that the sensitivity of model outcomes to
site base buffer attributes may not be sufficient. Further investigation
of the sensitivity of model outcomes to responses cited in empirical
studies would be useful in tweaking this component of the model.
Final buffers
10
4
Given additional mitigation measures for the site to deal with
sediment/pollution/runoff impacts, the threat ratings for these types
of risks was refined based on specialist input informed by the
recommendations for mitigating impacts on site. Final buffer widths
have been reduced by 50% when compared with the site-based buffer
requirements for the site, reflecting the reduced threat levels
anticipated for sediment and flow-related risks should additional
mitigation measures be implemented successfully and consistently.
Other risks such as light pollution and noise disturbance which could
affect populations of barn swallows and frog species are not addressed
here.
This would need to specifically be considered when
determining final setback requirements.
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Figure 6: Map showing construction phase buffer requirements for the Froggy Pond wetland at Mt
Moreland for Scenario B: residential development.
Figure 7: Map showing operational phase buffer requirements for the Froggy Pond wetland at Mt
Moreland for Scenario B: residential development.
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4.1.3.9.
Time required to complete the buffers assessment
Assuming that all site visits and wetland PES/EIS/biodiversity assessments have been undertaken
and documented, the approximate time taken to run through the buffers model for this wetland was
estimated at between 2 – 3 hours. Although most of the buffers tool/model was quick and easy to
run through, a large proportion of the total time was required for providing specialist input and
adjustments to threat ratings (with providing a rationale for any adjustments), running through the
biodiversity sensitivity component as well as in providing recommendations for additional
management/mitigation measures.
4.1.3.10.
Summary of comments and concerns raised
A number of concerns/difficulties were encountered during testing of the buffer model/tool. A
summary of the main concerns / difficulties encountered when applying the wetland buffers tool to
the Mt Moreland “Froggy Pond” wetland under two scenarios (Scenario A: irrigated commercial
cropland and Scenario B: residential development) together with suggestions for refinement is
documented in Table 7, below.
Table 7: Summary of comments & concerns raised for the buffer model testing on the Mt
Moreland / Froggy Pond wetland
CASE STUDY 2: MT MORELAND “FROGGY POND” WETLAND
Aspect considered
Comments / Concerns
Selection of sector /
sub-sector
It proved difficult to find each sub-sector within the drop down menu in the Excel
spreadsheet (small text and many subsectors all in one drop down menu).
Population of climatic
data
It would be good to provide a map of the Rainfall Intensity Zones in the model for easy
reference.
Desktop Threat Ratings
and Buffer requirements
Specialist threat ratings

Some of the desktop threat ratings appear to be either too high or too low, based on
further specialist investigation of the specific development type, nature of the site and
wetland and level of impacts anticipated. This emphasises the need for specialist input
to refine desktop ratings where a site-based assessment is undertaken.

Desktop buffer requirements seem generally fair and provide an initial indication of the
types of threats that could be problematic for different development types.

There is a concern that sub-sector will also be selected for the desktop-assessment.
Doing so provides results which are far from precautionary. It is therefore
recommended that worst-case site-based modifier scores are used when determining
desktop buffer requirements. This would result in a situation where desktop buffer
requirements are always adjusted down if threat ratings remain unchanged.

Threat is probably the most important criteria rated in this model as buffer zone
requirements are very strongly tied to this rating. Whilst the need to allow desktop
threat ratings to be customized is well founded, this assessment needs to be well
informed and be undertaken with appropriate diligence.

There is little guidance provided with regards to modifying the preliminary threat
ratings which could be built into the model if possible.

Reference to GLV values (as included in the guideline) is also not particularly useful for
practical application. A more useful suite of guidelines is therefore recommended to
allow users to rate threats in an objective manner.

The degree to which local site factors should be considered as part of this threat rating
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CASE STUDY 2: MT MORELAND “FROGGY POND” WETLAND
Aspect considered
Comments / Concerns
also requires some clarity (e.g. is sediment threat increased for a large site on a steep
slope or is this catered for through the site-based modifiers). From a sediment risk
perspective, site-based attributes are probably as relevant when assessing threat as
they are for evaluating buffer zone effectiveness.

Given the importance of this threat rating, there is a clear need to ensure that it is
appropriately motivated / justified. This would add significantly more time to the
assessment however.

It is very helpful to have a GIS system available in order to interrogate data and
calculate slopes, wetland vs catchment sizes, etc. The usefulness of such a tool should
be emphasized in the guideline.

It would be helpful to have quick access in the Excel spreadsheet to a description of
how to calculate catchment/wetland slopes, perimeter, vulnerability to erosion, etc.
This would improve the usability of the tool and help to cut back on time required for
assessments.

Consideration should be given to how the sensitivity modifiers are calculated. It may be
useful to weight each criteria more objectively using pairwise comparison rather than
simply calculating an average of the scores for each criterion. Alternatively, it may be
good to investigate the sensitivity of model outcomes to recommended buffer widths
cited in scientific studies to check that adjustments are appropriate.

A few criteria where selection of ratings required further specialist interpretation to
decide on ratings:
o inherent runoff potential of soils - requires further rationale/clarification;
o vulnerability of the site to erosion - is currently based only on slope and size but
soil characteristics should also be included (e.g. presence of dispersive soils,
indications of existing erosion features such as drains/gullies);
o sensitivity of vegetation to increased availability of nutrients/toxicant inputs –
requires specialist knowledge of vegetation at a site level; and
o level of domestic use – the tool could provide further clarity as to what types of
typical domestic use one can expect for wetland under the rationale for this
criterion.

There is a risk that wetland sensitivity can be overestimated or underestimated. This is
due to the fact that some wetlands may be spatially variable in terms of the sensitivity
of vegetation/habitat and biodiversity (species). Large buffers could be proposed for
areas of degraded habitat that are not considered ecologically sensitive/important. In
this instance the sensitivity assessment could be applied to spatially explicit sections of
the wetland rather than the entire unit as a whole, yielding a variable buffer result
applied to sections of the system rather than the whole unit.

In some instances (as with the Froggy Pond wetland), there are sections of the wetland
that are more sensitive than others. Consideration should be given to guide the
calculation of buffers for these cases where wetland integrity/sensitivity varies across
the system – especially when dealing with large wetland systems). In this instance the
sensitivity assessment could be applied to spatially explicit sections of the wetland
rather than the entire unit as a whole, yielding a variable result applied to sections of
the system rather than the whole unit. A variable buffer may need to be recommended
in these instances.
Sensitivity assessment
(wetland)
Sensitivity assessment
(biodiversity)
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CASE STUDY 2: MT MORELAND “FROGGY POND” WETLAND
Aspect considered
Preliminary buffer
requirements (excludes
local site attributes)
Site based modifiers
Sub-division of buffer
units
Site-based buffer
requirements
Additional Mitigation
Measures
Final buffer
requirements
Comments / Concerns

In the case of important biota, the rating of threats requires specialist input should be
based on the specialists understanding of species sensitivity to specific impacts. A
justification for these threat ratings should perhaps also be documented.

Integration of some confidence measure may be useful (although this could be used as
a cop-out for a poor assessment).

There is a definite need for specialist refinement of the preliminary threat ratings and
buffer widths outputted by the model.

An issue regarding rainfall intensity zones was identified and will need to be addressed
to ensure that buffer requirements are adjusted in an appropriate manner to cater for
differences in anticipated stormflows between rainfall intensity zones.

The site-based modifiers proved useful in refining threat scores and buffer widths, with
the outputs looking more reasonable than the preliminary buffer requirements.

Guidelines should provide clarity on whether the assessment is based on current buffer
characteristics or a worst-case scenario with development (e.g. steep unvegetated
slope vs gradual well-vegetated slope under pre-construction scenario).

Rating of soil characteristics could probably be refined to better cater for soil depth (as
this affects runoff) and erosion risk (in the case of sediment inputs).

Need to consider the issue of sub-dividing the buffer and rating site-based
modifications individually – need clear method and way of consolidating data for each
sub-division of the buffer (it looks like a separate spreadsheet will need to be
completed for each section of the buffer).

No guidance is provided on the width of area / buffer around the wetland to consider
when rating site-based modifiers. Clarity is therefore required to prevent confusion.

Where buffers are not homogenous and need to be broken up and assessed
individually, it is not clear as to how to capture this information. If a separate
spreadsheet needs to be completed in each case, this guidance should be provided.

The outcomes were regarded as reasonable.

Provide further guidance as to which buffer to use when looking at site-based buffer
modifiers (i.e. how relevant is a small operational buffer if construction buffers are
wide?).

Additional mitigation measures were recommended based on current best-practice
methods/techniques. The effect of other mitigation measures in reducing threat levels
for typical types of development activities could be documented in the tool.

There is a real concern that threat ratings are not reduced in a precautionary manner.
Whilst justification for reducing threat ratings is required, this could also be open to
abuse.

No guidance is provided as to mitigation of biodiversity aspects such as noise and visual
disturbance to sensitive species.

Final buffer widths have been reduced when compared with the site-based buffer
requirements for the site, reflecting generally reduced threat levels anticipated should
additional mitigation measures be implemented.

There are a number of other practical issues that are not addressed by the buffer zone
model. This includes factors such as other legal obligations (e.g. floodlines, existing
infrastructure located within recommended buffer zones), practical management
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CASE STUDY 2: MT MORELAND “FROGGY POND” WETLAND
Aspect considered
Comments / Concerns
considerations (e.g. can the wetland be managed with such a small buffer) and other
potential reasons for establishing a buffer zone (e.g. aesthetic value, screening of
visual/noise impacts for sensitive species, etc.). It would be useful if these factors could
be specifically flagged in the assessment as these criteria could be very important in
decision making.
Species of conservation
concern

The recommended maximum final buffer zones show areas of existing
farming/development within the buffer zone, often right up to the wetland boundary.
This has implications for the site in that these activities should essentially then be
required to pull out of the buffer zone areas and these areas would then need to be
rehabilitated such that the buffer is effective.

Further consideration should also be given to how buffer zone requirements are
documented in specialist reports. The current format of the model is not user friendly
for reporting purposes. An updated / refined front-end or output would help to
improve the usability and transparency of the outcomes of the assessment.
In this case study, catering for species of conservation concern would be the primary
determinant of setback requirements. Buffers of c.a. 250m have been recommended for
the critically endangered Pickersgill reed frog.
4.2. Hammarsdale Wetland
Doug Macfarlane and Adam Teixeira-Leite applied the model to the Hammarsdale Wetland case
study, located within the eThekwini Municipality, KZN.
4.2.1.
Site description
The wetland is located adjacent to the National Route 3 (N3) off-ramp to Hammarsdale, between the
towns of Drummond and Hammarsdale, eThekwini Municipality, KwaZulu-Natal (Figure 8). The site
is located within the sub-escarpment grassland bioregion of South Africa (Mucina & Rutherford,
2006) with the landscape characterized by steep incised river valleys and extensive grasslands on the
hillslopes and plateaus, with the local elevation ranging between 600 – 680m m.a.s.l. Local land use
in the area includes agriculture (sugarcane), subsistence farming, scattered residential holdings and
vast areas of open space (grassland and forest).
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Deliverable 11: Practical Testing / Field Testing Report
Drummond
N
3
Hammarsdale
Figure 8: Map showing the Hammarsdale wetland site, adjacent to the National Route 3 between
Drummond and Hammarsdale town, eThekwini Municipality, KZN.
The wetland is located at the base of a small valley that has been bisected by a tarred provincial road
and forms part of a broader wetland system that is located on a tributary river to the Sterkspruit
River. The local climate is characteristic of the subtropical climate in KwaZulu-Natal, with generally
warm, wet summers and cool, dry winters. The site falls within Rainfall Intensity Zone 4 (high)
characterized by a mean annual precipitation of 772.1mm (MAP class: 601 – 800mm) and a much
higher mean annual potential evapotranspiration rate of 1622.1mm. This gives a MAP to PET ratio
of 0.48 (vulnerability index of 1), which means that the wetland has a relatively high sensitivity to
hydrological impacts (i.e. changes in water input volumes and patterns).
4.2.2.
Description of the wetland
The wetland at Hammarsdale is very small in size (<0.5 ha) and forms part of a broader wetland unit
downstream (shown in Figures 9 and 10). The wetland can be classified as a dominantly
unchannelled valley bottom wetland, with channelled inflow via two small ephemeral drainage lines
that drain a relatively steep and very small catchment area above the wetland. Water flows diffusely
through the small wetland unit and exits via storm water culverts draining north beneath a formal
tarred road at the base of the wetland. The catchment comprises sandy mineral soils that are
considered well-draining. Land use in the catchment area of the wetland comprises old agricultural
lands (sugarcane farming) and secondary grasslands dominated by weeds and pioneer grasses, with
small drainage lines situated above the wetland that are vegetated with dense woody alien invasive
species. The wetland is characterised by a Typha capensis - Cyperus digitatus dominated herbaceous
mixed marsh that had been colonised by a range of alien invasive plants that comprise as much as
40% of the wetland habitat, the dominant of the exotic species being Lantana camara, Acacia
mearnsii, Rubus fruticosus and Solanum mauritianum.
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Deliverable 11: Practical Testing / Field Testing Report
Figure 9: Photo showing the small “Hammarsdale wetland”, dominated by
Typha capensis (bulrushes) and alien plants
Figure 10: Map showing the Hammarsdale wetland delineated above the tarred road.
The current state of wetland integrity is regarded as being Moderately Modified (C Class) overall,
based on the WET-Health (Macfarlane et al., 2007) assessment undertaken. Although wetland
geomorphology is considered to be largely intact, hydrology has been moderately modified due to a
combination of catchment impacts caused by land-cover transformation and a host of withinwetland modifications including the presence of a number of woody alien plants, infilling for road
construction and soil erosion features. Wetland vegetation has been largely modified (Class D),
primarily due to the extent of alien plants that have colonised the site as a result of current/historic
land-use and disturbance.
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Deliverable 11: Practical Testing / Field Testing Report
Based on a rapid level assessment of wetland goods and services for the system (WET-Ecoservices –
Kotze et al., 2007), it was estimated that the wetland provides Indirect Benefits such as flood
attenuation, sediment trapping and nutrient/toxicant removal to a low-moderate degree, whilst
Direct Human Benefits such as cultivated foods and tourism/cultural potential are generally
considered of far lower importance for this system. Wetland habitat is minimal and largely
fragmented from the wetland downstream and currently supports a range of common bird species
such as Burchell’s coucal, Southern Red bishop and Long-tailed whydah. Overall, the EIS (Ecological
Importance & Sensitivity) of the wetland is considered to be relatively low.
4.2.3.
4.2.3.1.
Outcomes of field testing
Level of assessment
The “Site-based” level of assessment was selected for the Hammarsdale wetland study, which was
informed by on-site sampling and verification of the wetland and catchment area by a specialist
wetland ecologist familiar with wetland delineation and functional assessment techniques and
methods.
4.2.3.2.
Proposed development scenario(s)
The proposed development scenario at the site is to establish a new Light Industrial, Warehousing
and Logistics precinct. The anticipated industrial development will comprise light industry
(warehouses), hardened parking areas and surfaced access roads. Bulk earthworks, hardened
infrastructure and access roads to the site are the primary activities expected to impact negatively
on the wetland. The Sector selected in the buffer tool was the “Mixeduse/Commercial/Retail/Business” type which best describes the development scenario (warehouses
& light industry). The “Medium Impact Mixed-use” Subsector type was selected to account for the
potential impacts of light industry proposed for the area. There could be some potential confusion
for these “mixed development” types, which could be placed under the “Industry” sector. In this
case it will be up to the specialist to review the desktop threat ratings and make sure that these
accurately reflect the level of risk/impact anticipated for a particular development. This places a
significant onus on the assessor which needs to be clearly communicated in the accompanying
guidelines.
Sector
Subsector
4.2.3.3.
Hammarsdale Wetland
Mixed-use/Commercial/Retail/Business
Medium Impact Mixed-use
Preliminary threat ratings and buffers
Preliminary/desktop threat ratings for the subsector selection indicate that impacts anticipated are
likely to be very low in terms of nutrient/contaminant inputs with a medium impact anticipated in
terms of increased sedimentation during construction. This seems to be a fair reflection of the
potential significance of impacts likely to be associated with the proposed bulk earthworks and
construction of hardened surfaces in the wetlands catchment area, although threats such as
sedimentation and altered hydrology will also depend largely on the specific of the development
project and the characteristics of the site being impacted. The desktop threat ratings do provide an
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Deliverable 11: Practical Testing / Field Testing Report
early indication of potential impacts to be flagged in terms of impact mitigation & management at
the site in addition to buffer requirements. Altered flow volumes to the wetland are potentially high
during operation, which is highly likely should storm water from the site be directed towards the
wetland area.
Desktop buffer requirements provided by the model (based on the worst-case scenario) suggest a
50m buffer zone for construction and 74m buffer for operation. This is regarded as appropriately
conservative when the specific nature of the industry or attributes of the site/wetland are not
known. It is worth noting however that when “Medium Impact Mixed Use” is selected as the SubSector, desktop buffer requirements declined to 15m during construction and 3m during the
operational phase to mitigate sediment impacts. While this reflects reduced risks associated with
the specific sub-sector, it does not account for local site characteristics which could require
significantly larger buffers. This should be addressed to ensure that desktop buffers are
appropriately conservative.
Desktop threat ratings required adjustment by the wetland specialist based on the anticipated sitespecific impacts and characteristics of the site (e.g. steep slopes, sandy erodible soils). Sediment
impacts were adjusted up to a Very High threat rating during construction in light of the site
characteristics and planned platform establishment adjacent to the wetland (slopes, soils).
Alterations to flow volumes reaching the wetland was adjusted down from a High to a Low threat
rating during operation as on-site attenuation of flows is being proposed for the development (see
mitigation & management measures in 1.4.6). Even with mitigation, it is anticipated that
sedimentation could still remain a problem during site operation due to the nature of the soils and
slopes above the wetland, and hence the threat rating was adjusted up from a Low to a High threat
level based on specialist input. This does highlight the importance of reviewing generic threat
ratings. While this detracts from the ease of applying the model, it does allow outputs of the model
to be tweaked based on a sound understanding of the site and planned development activity. This
does however increase the risk of misapplication of the model unless undertaken by a well-trained
and independent specialist.
4.2.3.4.
Sensitivity assessment
The sensitivity assessment undertaken for the site was relatively easy to follow, with rationale
provided for each criterion to direct the user’s allocation of sensitivity ratings. The outputs of the
sensitivity assessment highlight that the wetland is moderately sensitive to most threats/impacts,
with sensitivity to flow modifications (i.e. overall input volume and flood peaks) considered to be
high. This is probably a fair reflection for the wetland assessed, which was originally rated as lowmoderate in terms of the EIS (Ecological Importance and Sensitivity) of the system. No particularly
sensitive biodiversity features were identified for the wetland; hence the biodiversity sensitivity
assessment component was rated as low for all threats. The high sensitivity of the wetland to
alterations to flow regimes effectively increases the threat rating for this impact to a High threat
class.
Overall, the sensitivity assessment is quick and easy to run through, with only a few criteria where
selection of ratings required further specialist interpretation to decide on ratings. These included:

inherent runoff potential of soils - requires further rationale/clarification;
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Deliverable 11: Practical Testing / Field Testing Report

vulnerability of the site to erosion - is currently based only on slope and size but soil
characteristics should also be included (e.g. presence of dispersive soils, indications of
existing erosion features such as gullies);

sensitivity of vegetation to increased availability of nutrients/toxicant inputs – requires
specialist knowledge of vegetation at a site level.
4.2.3.5.
Site-based modifiers
Rating site-based modifiers based on the site-specific characteristics of the terrestrial buffer around
the wetland was relatively easy to apply for this site as the catchment area around the wetland is
relatively homogenous (moderate slope, moderate vegetation cover). The only area where variation
around the wetland needed to be accounted for was where the drainage lines enter the system
(concentrated flow paths). Since this was only a small section of the buffer, the buffer zone
modifiers were rated based on a single buffer unit, but taking into account slight variations in the
topography of the buffer. The only confusion related to exactly what buffer width to apply after
taking site-based characteristics into account (the maximum preliminary buffer requirement for the
construction phase was used in this case). This issue should be easy to address by providing
appropriate guidance when applying the model.
Another issue requiring clarification and further consideration is how the sensitivity modifiers are
calculated. At this stage, it is based on a weighted average of scores across the different
components assessed. A better approach could be to use pairwise comparison to determine an
appropriate weighting for the different input criteria. This would ideally performed by a group of
experts (potentially to be undertaken by the project team). The same comment applies to sitebased modifiers.
4.2.3.6.
Additional mitigation measures
In addition to buffer requirements, a range of mitigation measures have been recommended for the
site. These measures were deemed necessary and relevant to deal with some of the site specific
ecological concerns likely to arise during the construction and operation phases of the proposed
development, which buffer zones in isolation are unlikely to mitigate adequately. These included:
The potential for further alien plant infestation of wetland areas and buffers;

Relatively steep valley prone to soil erosion (sandy soils are considered highly erodible
within the context of potential concentrated water flows); and

Increased sediment inputs as a result of bulk earthworks near wetlands and altered runoff;
and

Increased flow volumes and velocities reaching wetland areas as a result of storm water
management during operation.
Mitigation measures concentrated on sedimentation and flow alteration risks which were
highlighted by the buffers model as being of particular concern. In addition, generic mitigation
measures to deal with potential toxicants/contaminants arising during construction & operation
were also included. The specifics regarding mitigation measures that have been proposed for the
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Deliverable 11: Practical Testing / Field Testing Report
site are documented in Appendix G. Assuming that the mitigation & management measures
proposed will be applied to the development site, refined threat classes were assigned to each
impact type as per the table in Appendix G. Major refinements to threat classes included:

Reducing the threat class from a Very High class to a High class for sedimentation & turbidity
risks during construction. Although on-site mitigation is likely to reduce this risk somewhat,
the risk of these impacts to wetland areas remains high due to the nature of the
construction activities planned (bulk earthworks) and the characteristics of the site (steep
slope, erodible soils).

Reducing the threat class from a High class to a Moderate class for sedimentation & turbidity
risks during operation. On-site mitigation involving the re-direction of flows away from
wetland areas is likely to reduce this risk to a moderate level, however some risk still
remains due to the nature of the construction activities planned (bulk earthworks) and the
characteristics of the site (steep slope, erodible soils).

Reducing the risk of altered flow volumes from a Moderate to a Low class during
construction & operational phases taking into account mitigation efforts aimed at directing
flows away from wetlands and implementation of a stormwater management system to
ensure that releases are closely aligned with pre-development conditions.

The risk of increased toxic contaminants reaching water resources remained Moderate, as
risk will vary depending on the specific types of light industry at the site (details not available
at the time of assessment).
4.2.3.7.
Outcomes of the buffers model
Outcomes of the buffers model applied to the Hammarsdale wetland are summarised in Table 8,
below whilst construction and operational phase buffer requirements are shown in Figures 11 and
12, respectively.
During construction, the risk of sedimentation associated with soil erosion is clearly the greatest
threat that development would pose to the wetland system. This threat has been highlighted as
possibly the greatest cause for concern with regards to the impact on wetland areas. A 31m buffer
was flagged in the buffers model for the construction phase based on potential sediment threats and
the nature of the potential buffer zone (steep slope). The model suggests this could be reduced to
15m as if adequate mitigation measures are implemented. With extensive earthworks and elevated
banks at the site, it will be difficult to reduce risks to any lower than a high threat level even with
proposed sediment/erosion control measures in place.
There are a number of other practical issues that are not addressed by the buffer zone model. This
includes factors such as other legal obligations (e.g. floodlines), practical management
considerations (e.g. can the wetland be managed with such a small buffer) and other potential
reasons for establishing a buffer zone (e.g. aesthetic value). It would be useful if these factors could
be specifically flagged in the assessment as these criteria could be very important in decision
making.
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Deliverable 11: Practical Testing / Field Testing Report
Table 8: Summary of buffer model outputs for the Hammarsdale wetland case study
Buffer
Recommendations
Desktop buffers
(Sub-sector)
Site-based buffers
Final buffers
Construction
Buffer Width
(m)
Operation
Buffer
Width (m)
50
(15)
74
(3)
31
13
15
2
Comments
Desktop buffer requirements are appropriately conservative when the
worst-case sub-sector is chosen. If the sub-sector is selected, buffer
widths for the construction phase are not considered large enough to
mitigate risks of erosion and sedimentation, given typical soil disturbance
associated with industrial developments. Buffers for the operational
phase are also considered inadequate given the steep nature of the site
and potential concerns of increased runoff volumes/velocities and the risk
of pollution from future industries. There is therefore a need to ensure
that desktop buffer requirements are adjusted to reflect a more
precautionary approach.
Buffer width was reduced considerably when taking the moderate
sensitivity of the resource and the site-based modifiers (largely associated
with the steep slope, reduced ground cover and presence of sandy,
erodible soils) into account. In the absence of other form of mitigation, a
31m buffer by itself (no other mitigation) downslope of a steep erodible
platform (with highly erodible soils) probably won’t provide a very good
level of protection from erosion and sediment impacts as runoff velocities
could potentially be high for this site. This issue could be resolved by
increasing the score for the slope of the buffer from 1 (moderate slope)
to 1.75 (steep slope) to account for platform development. Doing so,
would increase buffer requirements to 38m and 16m for construction and
operational phases respectively. Provided the buffer zone is appropriately
managed, this could prove sufficient for mitigation sediment risks.
Adjusting the score for soil properties up to better account for local
erosion risk could also provide a more appropriate outcome.
Given additional mitigation measures for the site to deal with
sediment/pollution/runoff impacts, the threat ratings for these types of
risks was refined based on specialist input informed by the
recommendations for mitigating impacts on site. Final buffer widths have
been reduced when compared with the site-based buffer requirements for
the site, reflecting the reduced threat levels anticipated should additional
mitigation measures be implemented.
The effectiveness of these buffer widths given the steep topography,
sandy nature of the soils and high rainfall intensities is questionable, with
initial thoughts being that a poorly vegetated 15m buffer may be
insufficient to adequately trap sediment. Research does however suggest
that a 15m buffer is likely to be 80% effective in trapping sediment which
may be acceptable in this instance.
The sensitivity of the model to changes in threat ratings is also quite a
concern, particularly when changing sediment threat from very-high to
high. While changes in buffer width are based on scientific information, it
can be subject to abuse. This could potentially be improved by providing
clearer guidance in rating threats as reference to GLV values is not
particularly relevant to most practitioners (e.g. link very high threat to
particular activity attributes).
Another concern that was picked up in the model was that there may be
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Deliverable 11: Practical Testing / Field Testing Report
Buffer
Recommendations
Construction
Buffer Width
(m)
Operation
Buffer
Width (m)
Comments
concerns with interpretation of rainfall intensity zones.
Buffer
1
requirements in Zone 1 are considerably higher that Zone 4 which is
contrary to expectations and to the description of calculations provided in
the ACRU user manual. The sub-contractor who assisted with running the
hydrological models will be contacted to obtain further clarity on this
matter.
Note too that the rainfall intensity zone map included in Wet-Ecoservices
and commonly applied by wetland ecologists is different to that used for
hydrological modelling (See Figure 5.16.2 in ACRU user manual). The most
appropriate rainfall intensity zone map will need to be included in the
final guidelines to ensure consistency of application.
Figure 11: Map showing construction phase buffer requirements for the Hammarsdale wetland.
1
In Zone 1, rainfall is characterised by long duration, relatively uniform events; Zones 2 or 3 are characterized by convective type storms
whist sites in Zone 4 are characterized by short cloudburst type events with very high
rainfall amounts Smithers & Schulze, 2004. ACRU AGROHYDROLOGICAL MODELLING SYSTEM. USER MANUAL.
VERSION 4.00. University of KwaZulu-Natal, Pietermaritzburg.
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Deliverable 11: Practical Testing / Field Testing Report
Figure 12: Map showing operational phase buffer requirements for the Hammarsdale wetland.
4.2.3.8.
Time required to complete the buffers assessment
Assuming that all site visits and wetland PES/EIS/biodiversity assessments have been undertaken
and documented, the approximate time taken to run through the buffers model for this wetland was
estimated at between 1 ½ – 2 hours. Although most of the buffers tool/model was quick and easy
to run through, a large proportion of the total time was required for providing specialist input and
adjustments to threat ratings (with providing a rationale for any adjustments) based on site-specific
characteristics and recommendations for additional management/mitigation measures for the
proposed development.
4.2.3.9.
Initial Scenario testing
To further test the sensitivity of the model outcomes to input variables, a range of additional
scenarios were evaluated which considered variations in climate, wetland sensitivity and site-based
attributes. Details of these scenarios and resultant outcomes are presented in Table 9, below.
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Deliverable 11: Practical Testing / Field Testing Report
Table 9: Outcomes of the scenario evaluation for the Hammarsdale wetland case study
SCENARIO
ACTUAL CASE STUDY
Sector
Sub-Sector
MAP Class
Rainfall Intensity Zone
Threat Ratings
Sensitivity
Assessment
Overall size
Perimeter to area ratio
Vulnerability of the HGM type to
sediment accumulation
Vulnerability of the site to erosion
given the site’s slope and size
Extent of open water, particularly
water that is naturally clear
Sensitivity of the vegetation to
Wetland
burial under sediment
attributes
Peat versus mineral soils
Inherent level of nutrients in the
landscape: is the wetland and its
catchment underlain by
sandstone?
Sensitivity of the vegetation to
increased availability of nutrients
Sensitivity
Modifiers
Level of domestic use
Increase in sediment inputs and
turbidity
Increased inputs of nutrients
Increase in pathogen inputs
601 - 800mm
Zone 4
2 (SENSITIVE DEPRESSIONAL
WETLAND)
Mixed-use/Commercial/Retail/Business
Medium Impact Mixed-use
>1201mm
601 - 800mm
Zone 1
Zone 4
As per test case (Without additional mitigation measures)
1 (WORST-CASE CLIMATE)
0.5-5 ha
Low-Intermediate
0.5-5 ha
Low-Intermediate
Unchannelled valley bottom
Unchannelled valley bottom
Moderately High (6-7)
Moderately High (6-7)
Low (<0.5%)
Low (<0.5%)
Intermediate
Intermediate
Mineral
3: LOW SENSITIVITY
FLOODPLAIN WETLAND
601 - 800mm
Zone 4
0.5-5 ha
High (>1500 m per ha)
Large (>300 ha)
Low (<500 m per ha)
Depression
Floodplain wetland
Low (<2)
Low (<2)
Intermediate (4-6%)
Mineral
High (>9% of the area)
High (e.g. short growing &
slow colonizing)
Mineral
Yes
Yes
Yes
Yes
Low (e.g. tall and dense
vegetation with low natural
diversity)
Low
Low (e.g. tall and dense
vegetation with low natural
diversity)
Low
High (e.g. short and/or
sparse vegetation cover with
high natural diversity)
Low
Intermediate (e.g. short
vegetation with moderate
natural plant diversity)
Low
0.93
0.92
0.92
0.93
0.92
0.92
1.21
1.46
1.17
0.64
0.79
0.5
Buffer
Assessment
39
Intermediate
Mineral
Deliverable 11: Practical Testing / Field Testing Report
SCENARIO
Buffer
attributes
Slope of the buffer
Vegetation characteristics
(Construction Phase)
Vegetation characteristics
(Operational Phase)
Soil properties
Topography of the buffer zone
Site-based
Modifiers
(Construction)
Site-based
Modifiers
(Operation)
Increase in sediment inputs and
turbidity
Increased inputs of nutrients
Increase in pathogen inputs
Increase in sediment inputs and
turbidity
Increased inputs of nutrients
Increase in pathogen inputs
Moderate
2 (SENSITIVE DEPRESSIONAL
WETLAND)
Moderate
3: LOW SENSITIVITY
FLOODPLAIN WETLAND
Moderate
Moderately Low
Moderately Low
Moderately Low
Moderately Low
Moderately Low
Moderately textured
Dominantly Non-uniform
topography
Moderately Low
Moderately textured
Dominantly Non-uniform
topography
Moderately Low
Moderately textured
Dominantly Non-uniform
topography
Moderately Low
Moderately textured
Dominantly Non-uniform
topography
1.23
1.25
1.23
1.23
1.25
1.23
1.23
1.25
1.23
1.23
1.25
1.23
1.09
1.08
1.09
1.09
1.08
1.09
1.09
1.08
1.09
1.09
1.08
1.09
31
3
2
31
61
5
5
61
58
3
2
58
18
3
2
18
13
2
2
13
46
4
4
46
26
2
2
26
8
2
2
8
Test case
Buffer requirements are very
responsive to climate.
Sensitivity of the model is
regarded as too high and
ACTUAL CASE STUDY
1 (WORST-CASE CLIMATE)
Moderate
Site-Based
Buffer
Requirements
Construction
Phase
Operational
Phase
Comments
Increase in sediment inputs and
turbidity
Increased inputs of nutrients
Increase in pathogen inputs
Buffer recommendation
Increase in sediment inputs and
turbidity
Increased inputs of nutrients
Increase in pathogen inputs
Buffer recommendation
40
Buffer requirements are very responsive to the sensitivity of
the receiving environment (Buffer requirements vary by
more than 3x when comparing low and high sensitivity
ecosystems). Suggest that responsitivity be reduced
Deliverable 11: Practical Testing / Field Testing Report
SCENARIO
ACTUAL CASE STUDY
1 (WORST-CASE CLIMATE)
will need to be
reconsidered.
2 (SENSITIVE DEPRESSIONAL
3: LOW SENSITIVITY
WETLAND)
FLOODPLAIN WETLAND
considerably.
(Note: Differences are compounded by site attributes where large modifiers are also
applied)
SCENARIO
Sector
Sub-Sector
MAP Class
Rainfall Intensity Zone
Threat Ratings
Sensitivity
Assessment
Overall size
Perimeter to area ratio
Vulnerability of the HGM type to sediment
accumulation
Vulnerability of the site to erosion given
the site’s slope and size
Wetland
Extent of open water, particularly water
attributes
that is naturally clear
Sensitivity of the vegetation to burial
under sediment
Peat versus mineral soils
Inherent level of nutrients in the
landscape: is the wetland and its
catchment underlain by sandstone?
4: IDEAL BUFFER
5: POOR CONDITION BUFFER
CHARACTERISTICS (GENTLY
(VERY STEEP WITH POOR
SLOPING NATURAL GRASSLAND)
VEGETATION COVER)
Mixed-use/Commercial/Retail/Business
Medium Impact Mixed-use
601 - 800mm
601 - 800mm
Zone 4
Zone 4
As per test case (Without additional mitigation measures)
ACTUAL CASE STUDY
601 - 800mm
Zone 4
0.5-5 ha
Low-Intermediate
0.5-5 ha
Low-Intermediate
0.5-5 ha
Low-Intermediate
Unchannelled valley bottom
Unchannelled valley bottom
Unchannelled valley bottom
Moderately High (6-7)
Moderately High (6-7)
Moderately High (6-7)
Low (<0.5%)
Low (<0.5%)
Low (<0.5%)
Intermediate
Intermediate
Intermediate
Mineral
Mineral
Mineral
Yes
Yes
Yes
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Deliverable 11: Practical Testing / Field Testing Report
ACTUAL CASE STUDY
4: IDEAL BUFFER
CHARACTERISTICS (GENTLY
SLOPING NATURAL GRASSLAND)
5: POOR CONDITION BUFFER
(VERY STEEP WITH POOR
VEGETATION COVER)
Low (e.g. tall and dense vegetation
with low natural diversity)
Low (e.g. tall and dense vegetation
with low natural diversity)
Low (e.g. tall and dense vegetation
with low natural diversity)
Low
0.93
0.92
0.92
Low
0.93
0.92
0.92
Low
0.93
0.92
0.92
Moderate
Very Gentle
Very steep
Moderately Low
Very high
Low
Increase in sediment inputs and turbidity
Increased inputs of nutrients
Increase in pathogen inputs
Increase in sediment inputs and turbidity
Increased inputs of nutrients
Increase in pathogen inputs
Moderately Low
Moderately textured
Dominantly Non-uniform
topography
1.23
1.25
1.23
1.09
1.08
1.09
High
Uniform topography
Dominantly Non-uniform
topography
0.7
0.74
0.7
0.7
0.7
0.7
Low
Moderately textured
Dominantly Non-uniform
topography
1.64
1.67
1.64
1.64
1.67
1.64
Increase in sediment inputs and turbidity
Increased inputs of nutrients
Increase in pathogen inputs
Buffer recommendation
Increase in sediment inputs and turbidity
Increased inputs of nutrients
Increase in pathogen inputs
31
3
2
31
13
2
2
17
1
1
17
8
1
1
41
3
3
41
20
3
2
SCENARIO
Sensitivity of the vegetation to increased
availability of nutrients
Sensitivity
Modifiers
Level of domestic use
Increase in sediment inputs and turbidity
Increased inputs of nutrients
Increase in pathogen inputs
Buffer
Assessment
Buffer attributes
Slope of the buffer
Vegetation characteristics (Construction
Phase)
Vegetation characteristics (Operational
Phase)
Soil properties
Topography of the buffer zone
Site-based
Modifiers
(Construction)
Site-based
Modifiers
(Operation)
Site-Based Buffer
Requirements
Construction
Phase
Operational Phase
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Deliverable 11: Practical Testing / Field Testing Report
SCENARIO
ACTUAL CASE STUDY
Buffer recommendation
Comments
13
Test case
43
4: IDEAL BUFFER
CHARACTERISTICS (GENTLY
SLOPING NATURAL GRASSLAND)
8
5: POOR CONDITION BUFFER
(VERY STEEP WITH POOR
VEGETATION COVER)
20
The model is very responsive to local site attributes, with buffer zones
varying between 17 and 41m in this case study.
This responsively appears reasonable but requires further verification.
Deliverable 11: Practical Testing / Field Testing Report
This scenario testing proved very useful in identifying some concerns regarding the sensitivity of the
model. Key concerns raised included:

The buffer requirement appeared to be overly responsive to changes in climatic variables in
high rainfall environments with buffer requirements more than doubling under a highest risk
climatic context;

The buffer requirements are probably overly responsive to the sensitivity assessment with
buffer zone requirements varying by close to three times in response to changes in wetland
sensitivity.

The nature of calculations (multiplication of modifiers) appears to result in extremely
inflated values when a range of modifiers are rated as high.
This points to the need for a more comprehensive sensitivity assessment that can be used to ensure
that resultant buffer recommendations occur within a reasonable range.
Two errors were also identified in the site-based modifiers template. The operational phase
vegetation score was not being carried through appropriately while the score for soil properties
under “Nutrient Inputs” was referencing the incorrect cell.
4.2.3.10.
Summary of comments & concerns raised
A number of concerns/difficulties were encountered during testing of the buffer model/tool. A
summary of the main concerns / difficulties encountered when applying the wetland buffers tool to
the Hammarsdale wetland mixed-use development scenario is documented in Table 10, below. In
light of these concerns/difficulties, the following suggestions have been made in an attempt to make
the tool more user-friendly:

Including guidelines either in the comments tab or in a new tab within the excel spreadsheet
on how to calculate/rate certain criteria in the sensitivity assessment (e.g. slopes, perimeter,
vulnerability to erosion, etc.);

Making it easier to select sub-sector types (perhaps using numbers per sub-sector for easy
reference & increasing the font in the drop-down list);

Provide further guidance as to which buffer to use when looking at site-based buffer
modifiers (i.e. how relevant is a small operational buffer if construction buffers are wide?);

Need to consider the issue of sub-dividing the buffer and rating site-based modifications
individually – need clear method and way of consolidating data for each sub-division of the
buffer (it looks like a separate spreadsheet will need to be completed for each section of the
buffer);

Potential exists to include some form of confidence index that weights certain criteria based
on the level of confidence of the assessor/user (e.g. biodiversity sensitivity ratings would
have a relatively low confidence index rating for an assessor that is largely unfamiliar with
biodiversity features in the study area or where such information is lacking and/or studies
have not been done in sufficient detail to warrant a high confidence rating).
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Deliverable 11: Practical Testing / Field Testing Report
Table 10: Summary of comments & concerns raised for the buffer model testing on the
Hammarsdale wetland
Aspect considered

Selection of sector /
sub-sector
Population of climatic
data



Desktop Buffer
requirement




Specialist threat ratings




Sensitivity assessment
(wetland)



Sensitivity assessment
(biodiversity)



Preliminary buffer
requirements (excludes
local site attributes)

CASE STUDY 1: HAMMARSDALE WETLAND
Comments / Concerns
Further clarity could be provided for the “mixed-use” type subsectors to better define
what sort of typical activities would be associated with this type.
It was difficult to find each sub-sector within the drop down menu in the Excel
spreadsheet (small text).
It would be good to provide a map of the Rainfall Intensity Zones in the model for easy
reference.
Desktop buffer requirements seem fair and provide an initial indication of the types of
threats that could be problematic for industrial developments as a sector.
There is a concern that sub-sector will also be selected for the desktop-assessment.
Doing so provides results which are far from precautionary. As such, adjustments need
to be made to the tool to ensure that more precautionary buffer requirements are
reflected.
Threat is probably the most important criteria rated in this model as buffer zone
requirements are very strongly to this rating. Whilst the need to allow desktop threat
ratings to be customized is well founded, this assessment needs to be well informed
and be undertaken with appropriate diligence.
There is little guidance provided with regards to modifying the preliminary threat
ratings which could be built into the model if possible.
Reference to GLV values (as included in the guideline) is also not particularly useful for
practical application. A more user suite of guidance is therefore recommended to allow
users to rate threats in an objective manner.
The degree to which local site factors should be considered as part of this threat rating
also requires some clarity (e.g. is sediment threat increased for a large site on a steep
slope or is this catered for through the site-based modifiers?). From a sediment risk
perspective, site-based attributes are probably as relevant when assessing threat as
they are for evaluating buffer zone effectiveness.
It may be useful for practitioner to document their rational for threat ratings applied –
although this would add time to the assessment.
It is very helpful to have a GIS system available in order to interrogate data and
calculate slopes, wetland vs catchment sizes, etc. The usefulness of such a tool should
be emphasized in the guideline.
It would be helpful to have quick access in the Excel spreadsheet to a description of
how to calculate catchment/wetland slopes, perimeter, vulnerability to erosion, etc.
This would improve the usability of the tool.
Consideration should be given to how the sensitivity modifiers are calculated. It may be
useful to weight each criteria more objectively using pairwise comparison rather than
simply calculating an average of the scores for each criterion.
Some suggestions for refining the sensitivity criteria are provided.
No particularly sensitive biodiversity features were identified for the wetland; hence
the biodiversity sensitivity assessment component was rated as low for all threats for
this wetland.
Since the rating of threats will be species-specific, specialist input should be based on
the specialists understanding of species sensitivity to specific impacts in order to
provide a meaningful rating in this instance.
Integration of some confidence measure may be useful (although this could be used as
a cop-out for a poor assessment).
There is a definite need for specialist refinement of the preliminary threat ratings and
buffer widths outputted by the model.
An issue regarding rainfall intensity zones was identified and will need to be addressed
to ensure that buffer requirements are adjusted in an appropriate manner to cater for
differences in anticipated stormflows between rainfall intensity zones.
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Deliverable 11: Practical Testing / Field Testing Report
Aspect considered


Site based modifiers




Sub-division of buffer
units


Site-based buffer
requirements

Additional Mitigation
Measures


Final buffer
requirements
Species of conservation
concern


CASE STUDY 1: HAMMARSDALE WETLAND
Comments / Concerns
The site-based modifiers proved useful in refining threat scores and buffer widths, with
the outputs looking more reasonable than the preliminary buffer requirements.
Guidelines should provide clarity on whether the assessment is based on current buffer
characteristics or a worst-case scenario with development. E.g. Very steep platform vs
gradual slope under pre-construction activities.
Rating of soil characteristics could potentially be refined to better cater for soil depth
(as this affects runoff) and erosion risk (in the case of sediment inputs).
The rationale / approach for combining sensitivity criteria into a single score should be
considered.
Two errors were identified in the site-based modifiers template. The operational phase
vegetation score was not being carried through appropriately while the score for soil
properties under “Nutrient Inputs” was referencing the incorrect cell.
No guidance is provided on the width of area / buffer around the wetland to consider
when rating site-based modifiers. Clarity is therefore required to prevent confusion.
Where buffers are not homogenous and need to be broken up and assessed
individually, it is not clear as to how to capture this information. If a separate
spreadsheet needs to be completed in each case, this guidance should be provided.
Concerns were raised as to whether or not a 31m buffer by itself (no other forms of
mitigation) on a relatively steep slope probably would provide an appropriate level of
protection from erosion and sediment impacts as runoff velocities could potentially be
high for this site. The issue could be resolved somewhat by rating slope according to
the anticipated final slope of the platform rather than based on existing buffer
attributes.
Additional mitigation measures were recommended based on current best-practice
methods/techniques. The effect of other mitigation measures in reducing threat levels
could be documented in the tool.
There is however a real concern that threat ratings are not reduced in a precautionary
manner. Whilst justification for reducing threat ratings is required, this could also be
open to abuse.
Final buffer widths have been reduced when compared with the site-based buffer
requirements for the site, reflecting the reduced threat levels anticipated should
additional mitigation measures be implemented.
There are a number of other practical issues that are not addressed by the buffer zone
model. This includes factors such as other legal obligations (e.g. floodlines), practical
management considerations (e.g. can the wetland be managed with such a small
buffer) and other potential reasons for establishing a buffer zone (e.g. aesthetic value).
It would be useful if these factors could be specifically flagged in the assessment as
these criteria could be very important in decision making.
No species of conservation concern were identified for this site.
Further consideration should also be given to how buffer zone requirements are documented in
specialist reports. The current format of the model is not user friendly for reporting purposes. An
updated / refined front-end or output would help to improve the usability and transparency of the
outcomes of the assessment.
The sensitivity assessment has also highlighted the need to undertake a more comprehensive
sensitivity assessment to ensure that multipliers used in the model result in an appropriate outcome.
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Deliverable 11: Practical Testing / Field Testing Report
4.2.3.11.
Outcomes of the updated model
Following initial field testing and the sensitivity analysis, the buffer zone model was updated. The
revised model was then applied against the same set of case studies used to test the draft model.
Results of this assessment are presented here.
Outcomes of the scenario evaluation
The results of the scenario evaluation are presented in Table 11, below. This showed that the
changes made had a significant bearing on recommended buffer widths. The following key points
are worth emphasizing:

Climate: Modifiers applied to rainfall intensity zones were miss-allocated in the initial model.
This error was corrected in the updated model and an adjustment to the weighting assigned to
climatic variables was included. The outcomes of the model now give a range in buffer widths of
between 45 and 71m for construction and 24 and 45m during operation for this case study.
Given the significant variability in stormflows expected across climatic regions, this variation
seems justifiable.

Wetland sensitivity: Recommended buffer widths were also responsive to changes in wetland
sensitivity, with recommended buffer widths ranging from 45 – 66m for construction and 25 –
33m for the operational phases respectively. This variability is regarded as moderate allowing
some tailoring of buffer requirements based on the receiving environment without making this a
dominant factor. This variability in outputs is significantly smaller than that produced by the
draft model.

Buffer attributes: Based on the literature, it is clear that buffer width only accounts for some of
the variability in buffer zone effectiveness and that a range of other factors need to be
considered when determining site-based buffer requirements. The model remains responsive
the changes in buffer attributes with ranges of 31 – 79m advocated to address construction risks
while those advocated for operational risks ranged from 18 – 46m.

Composite responses: When both wetland sensitivity and buffer attributes were altered, the
range of buffer attributes increased as anticipated. Indeed possible buffer ranges under the
prevailing climate ranged from 26 – 96m for construction and 15-56m for the operational phase.
While variability remains high, this is regarded as justifiable across the extremes represented
here.
It is important to note that buffer requirements in this test case were driven largely by sediment
risks, particularly those associated with construction activities. As can be seen from Table 4,
minimum buffers of 15m were consistently recommended for these other potential impacts due to
the low risks associated with the particular sub-sector in question. This reflects a precautionary
approach which has been integrated to alleviate some of the risks of buffer zone failure in the longterm due to poor management practices.
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Deliverable 11: Practical Testing / Field Testing Report
Table 11: Outcomes of the initial scenario evaluation for the Hammarsdale wetland case study using the updated wetland model.
1B: Best-case climate
2A:
Sensitive
depressional wetland
2B:
Low sensitivity
floodplain wetland
Scenario
Actual case study
1A: Worst-case climate
Focus of comparison
Reference
Climatic variability
Sector
Mixed-use/Commercial/Retail/Business
Sub-Sector
Medium Impact Mixed-use
MAP Class
601 - 800mm
>1201mm
0 - 400mm
601 - 800mm
601 - 800mm
Rainfall Intensity Zone
Zone 4
Zone 4
Zone 1
Zone 4
Zone 4
Threat Ratings
As per test case (Without additional mitigation measures)
Sensitivity of wetland
Sensitivity Assessment
Wetland
attributes
Overall size
0.5-5 ha
0.5-5 ha
0.5-5 ha
0.5-5 ha
Large (>300 ha)
Perimeter to area ratio
Low-Intermediate
Low-Intermediate
Low-Intermediate
High (>1500 m per ha)
Low (<500 m per ha)
Vulnerability of the HGM
type
to
sediment
accumulation
Unchannelled
bottom
Depression
Floodplain wetland
Vulnerability of the site to
erosion given the site’s slope
and size
Moderately High (6-7)
Low (<2)
Low (<2)
Extent of open water,
particularly water that is
naturally clear
Low (<0.5%)
High (>9% of the area)
Intermediate (4-6%)
Intermediate
valley
Unchannelled
bottom
valley
Moderately High (6-7)
Low (<0.5%)
Unchannelled
bottom
valley
Moderately High (6-7)
Low (<0.5%)
Sensitivity of the vegetation
to burial under sediment
Intermediate
Intermediate
Intermediate
High (e.g. short growing
& slow colonizing)
Peat versus mineral soils
Mineral
Mineral
Mineral
Mineral
Mineral
Inherent level of nutrients in
the landscape: is the
wetland and its catchment
underlain by sandstone?
Yes
Yes
Yes
Yes
Yes
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Deliverable 11: Practical Testing / Field Testing Report
Sensitivity
Modifiers
Sensitivity of the vegetation
to increased availability of
nutrients
Low (e.g. tall and dense
vegetation with low
natural diversity)
Low (e.g. tall and dense
vegetation with low
natural diversity)
Low (e.g. tall and dense
vegetation with low
natural diversity)
High (e.g. short and/or
sparse vegetation cover
with
high
natural
diversity)
Intermediate (e.g. short
vegetation
with
moderate natural plant
diversity)
Level of domestic use
Low
Low
Low
High
Low
Increase in sediment inputs
and turbidity
0.97
0.97
0.97
1.05
0.89
Increased inputs of nutrients
0.96
0.96
0.96
1.13
0.94
Increase in pathogen inputs
0.95
0.95
0.95
1.13
0.85
Slope of the buffer
Moderate
Moderate
Moderate
Moderate
Moderate
Vegetation characteristics
(Construction Phase)
Moderately Low
Moderately Low
Moderately Low
Moderately Low
Moderately Low
Vegetation characteristics
(Operational Phase)
Moderately Low
Moderately Low
Moderately Low
Moderately Low
Moderately Low
Soil properties
Moderately textured
Moderate permeability
Moderate permeability
Moderate permeability
Moderate permeability
Topography of the buffer
zone
Dominantly
Nonuniform topography
Dominantly
Nonuniform topography
Dominantly
Nonuniform topography
Dominantly
Nonuniform topography
Dominantly
Nonuniform topography
Increase in sediment inputs
and turbidity
1.23
1.23
1.23
1.23
1.23
Increased inputs of nutrients
1.25
1.25
1.25
1.25
1.25
Increase in pathogen inputs
1.23
1.23
1.23
1.23
1.23
Increase in sediment inputs
and turbidity
1.23
1.23
1.23
1.23
1.23
Increased inputs of nutrients
1.25
1.25
1.25
1.25
1.25
Increase in pathogen inputs
1.23
1.23
1.23
1.23
1.23
Buffer Assessment
Buffer
attributes
Site-based
Modifiers
(Construction)
Site-based
Modifiers
(Operation)
Site-Based Buffer Requirements
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Deliverable 11: Practical Testing / Field Testing Report
Construction
Phase
Operational
Phase
Comments
Increase in sediment inputs
and turbidity
54
71
45
66
45
Increased inputs of nutrients
15
15
15
15
15
Increase in pathogen inputs
15
15
15
15
15
Buffer recommendation
54
71
45
66
45
Increase in sediment inputs
and turbidity
32
42
25
39
26
Increased inputs of nutrients
15
15
15
15
15
Increase in pathogen inputs
15
15
15
15
15
Buffer recommendation
32
45
25
39
26
Test case
Adjustments to the model now provide a more
defensible range of scores when accounting for
climate (much narrower range).
50
Adjustments to the model now provide a more
defensible range of scores when accounting for
the sensitivity of the wetland.
Deliverable 11: Practical Testing / Field Testing Report
Scenario
Actual case study
3A:
Ideal buffer
characteristics (gently
sloping
natural
grassland)
Focus of comparison
Reference
Buffer attributes
Sector
Mixed-use/Commercial/Retail/Business
Sub-Sector
Medium Impact Mixed-use
MAP Class
601 - 800mm
601 - 800mm
601 - 800mm
601 - 800mm
601 - 800mm
Rainfall Intensity Zone
Zone 4
Zone 4
Zone 4
Zone 4
Zone 4
Threat Ratings
As per test case (Without additional mitigation measures)
3B: Poor condition
buffer (Very steep with
poor vegetation cover)
4A: Combination of 2A
& 3B
4B: Combination of 2B
& 3A
Worst-case vs. best-case
Sensitivity Assessment
Wetland
attributes
Overall size
0.5-5 ha
0.5-5 ha
0.5-5 ha
0.5-5 ha
Large (>300 ha)
Perimeter to area ratio
Low-Intermediate
Low-Intermediate
Low-Intermediate
High (>1500 m per ha)
Low (<500 m per ha)
Vulnerability of the HGM
type
to
sediment
accumulation
Unchannelled
bottom
Depression
Floodplain wetland
Vulnerability of the site to
erosion given the site’s slope
and size
Moderately High (6-7)
Low (<2)
Low (<2)
Extent of open water,
particularly water that is
naturally clear
Low (<0.5%)
High (>9% of the area)
Intermediate (4-6%)
Sensitivity of the vegetation
to burial under sediment
Intermediate
Intermediate
Intermediate
High (e.g. short growing
& slow colonizing)
Intermediate
Peat versus mineral soils
Mineral
Mineral
Mineral
Mineral
Mineral
Inherent level of nutrients in
the landscape: is the
wetland and its catchment
underlain by sandstone?
Yes
Yes
Yes
Yes
Yes
valley
Unchannelled
bottom
valley
Moderately High (6-7)
Low (<0.5%)
Unchannelled
bottom
valley
Moderately High (6-7)
Low (<0.5%)
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Deliverable 11: Practical Testing / Field Testing Report
Sensitivity
Modifiers
Sensitivity of the vegetation
to increased availability of
nutrients
Low (e.g. tall and dense
vegetation with low
natural diversity)
Low (e.g. tall and dense
vegetation with low
natural diversity)
Low (e.g. tall and dense
vegetation with low
natural diversity)
High (e.g. short and/or
sparse vegetation cover
with
high
natural
diversity)
Intermediate (e.g. short
vegetation
with
moderate natural plant
diversity)
Level of domestic use
Low
Low
Low
High
Low
Increase in sediment inputs
and turbidity
0.97
0.97
0.97
1.05
0.89
Increased inputs of nutrients
0.96
0.96
0.96
1.13
0.94
Increase in pathogen inputs
0.95
0.95
0.95
1.13
0.85
Slope of the buffer
Moderate
Very Gentle
Very steep
Very steep
Very Gentle
Vegetation characteristics
(Construction Phase)
Moderately Low
Very high
Low
Low
Very high
Vegetation characteristics
(Operational Phase)
Moderately Low
High
Low
Low
High
Soil properties
Moderately textured
High Permeability
Low permeability
Low permeability
High Permeability
Topography of the buffer
zone
Dominantly
Nonuniform topography
Uniform topography
Dominantly
Nonuniform topography
Dominantly
Nonuniform topography
Uniform topography
Increase in sediment inputs
and turbidity
1.23
0.7
1.77
1.77
0.7
Increased inputs of nutrients
1.25
0.74
1.75
1.75
0.74
Increase in pathogen inputs
1.23
0.7
1.77
1.77
0.7
Increase in sediment inputs
and turbidity
1.23
0.7
1.77
1.77
0.7
Increased inputs of nutrients
1.25
0.74
1.75
1.75
0.74
Increase in pathogen inputs
1.23
0.7
1.77
1.77
0.7
Buffer Assessment
Buffer
attributes
Site-based
Modifiers
(Construction)
Site-based
Modifiers
(Operation)
Site-Based Buffer Requirements
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Deliverable 11: Practical Testing / Field Testing Report
Construction
Phase
Operational
Phase
Comments
Increase in sediment inputs
and turbidity
54
31
79
96
26
Increased inputs of nutrients
15
15
15
15
15
Increase in pathogen inputs
15
15
15
15
15
Buffer recommendation
54
31
79
96
26
Increase in sediment inputs
and turbidity
32
18
46
56
15
Increased inputs of nutrients
15
15
15
15
15
Increase in pathogen inputs
15
15
15
15
15
Buffer recommendation
32
18
46
56
15
Test case
There is significant variation, particularly in the
case of recommended buffers to cater for
sedimentation risks which were rates as very high
for this case study. A major increase in buffer
width under this scenario appears justifiable.
53
When compared with the previous scenarios, it is
clear that buffer changes in an appropriate
direction under this scenario. While variability
remains high, this is justifiable across the extremes
represented here.
Deliverable 11: Practical Testing / Field Testing Report
4.3.
Zulti South - eSikhawini wetland system
Ian Bredin applied the model to the Zulti South wetland case study.
4.3.1.
Site description
The Zulti South mineral lease area is situated south of Richards Bay and the Umhlathuze River and
north of Port Dunford. It is on land owned by the Ingonyama Trust and falls mainly on the boundary
of an old forestry area. Lake Chubu, the town of Esikhawini and the N2 highway are to the northwest of the mining area (Figure 13). The proposed mining area covers a length of approximately 20
km and varies in width from 0.5 km to 2 km inland from the high water mark.
Figure 13: Location of the eSikhawini wetland
The eSikhawini township area is characterised by large valley bottom wetland systems located along
a series of dendritic drainage lines that flow towards the north away from the dune cordon. The
study area was one of the valley bottom wetlands, which drains inland (i.e. towards Lake Chubu).
The study area was located on the seaward side of the last major road running parallel to the dune
cordon, and is likely to provide an indication of the ecosystem service provision and health of the
greater wetland system (i.e. the wetland was only delineated to the road as this was the Zulti South
lease boundary).
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Deliverable 11: Practical Testing / Field Testing Report
4.3.2.
Description of the wetland
The wetland has been referred to as one of the arms of the larger eSikhawini wetland system. This
particular wetland is approximately 2.4ha and is primarily an unchannelled valley bottom wetland
with flow being predominantly diffuse within the wetland (Figure 14a).
The wetlands catchment consists primarily of indigenous grassland (largely disturbed grassland),
Eucalyptus grandi woodlots, sugarcane and a few homesteads. The cultivation of sugarcane does
extend into the temporary zone on the western boundary of the wetland.
The current state of wetland integrity is regarded as being Moderately Modified (C Class) overall,
based on the WET-Health (Macfarlane et al., 2007) assessment undertaken. Hydrological functioning
has been moderately modified by catchment activities including sugarcane farming and Eucalyptus
grandi woodlots. Wetland vegetation integrity is generally considered to be largely modified due to
the cultivation of sugarcane within a portion of the wetland and some Eucalyptus grandi trees and
other invader species (Figure 14b). Although modified there is still a large portion of wetland habitat
that remains largely natural (i.e. Cyperus marsh area – dominated by Cyperus dives).
Figure 14 a and b: eSikhawini unchannelled valley bottom wetland with sugarcane and Eucalyptus
woodlots in the catchment
In terms of ecological functioning, the wetland functions well at removing nutrients, trapping
sediment and maintaining biodiversity. The Critically Endangered frog species Hyperiolius pickersgilli
(Pickersgill’s reed frog) has been identified to occur at a number of wetlands in close proximity to
the case study site and given that the wetland has suitable habitat for the frog species it is likely that
it also utilizes the wetland. In terms of wetland EIS (Ecological Importance & Sensitivity), the wetland
is regarded as having a High EIS rating.
4.3.3.
4.3.3.1.
Outcomes of field testing
Level of assessment
The “Site-based” level of assessment was selected for the Zulti South wetland study, which was
informed by previous site visits and verification of the wetland and catchment area. The Sector
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Deliverable 11: Practical Testing / Field Testing Report
selected in the buffer tool was “Mining”. Sector selection was straight forward with no ambiguity
posed by the model. In terms of Subsector type selection, the “Moderate-risk mining operations”
was selected. Subsector selection was also straight forward with a relatively low level of ambiguity.
4.3.3.2.
Proposed development
Richards Bay Minerals (RBM) proposes to mine the dune sands within the Zulti South lease area. The
dune sands will be mined by a combination of dry mining and dredge mining, and processed to
produce a heavy mineral concentrate containing the valuable heavy minerals ilmenite, rutile and
zircon. The proposed mining method in the catchment of the eSikhawini wetland system will be dry
mining. Typical ecological impacts/threats to the wetland resource would probably include:

Sedimentation as a result of bare stripped soils/tillage;

Possible increased toxic contaminants from mining related activities;

Disturbance of wetland edges and increased threat of alien plants colonising wetland
habitat;

Visual and noise disturbance impacts on biodiversity (fauna); and

Altered catchment hydrology (both surface and groundwater) as a result of the mining
activity.
4.3.3.3.
Outcomes of the buffers model
By far the greatest impact associated with the proposed mining at Zulti South will be the impact on
the wetlands hydrology. Mining will take place within the catchment of the wetland and will also
occur below the regional groundwater table, therefore impacting all wetland systems in the vicinity
that are connected to groundwater (i.e. a large proportion of the wetlands within the northern KZN
sandy aquifer coastal plans are connected to groundwater at one level or another). Therefore the
hydrological impacts to the wetland are difficult to determine. Buffering a wetland will unfortunately
not address the impacts unless it includes the entire catchment affected by the mining activity, both
on the surface and below ground (i.e. the relevant aquifer).
Applying the threat ratings, sensitivity assessment and site-based modifier at the site was done with
relative ease. However, the recommended buffer widths of 50m at a desktop level and 93m at a sitebased level were not adequate to address the hydrological impacts. Note – the site-based buffer
was rounded off to 100m. Rounding up of buffer widths should be taken into consideration. This is
because the model was not developed to address hydrological impacts of this nature. Buffers are
determined according to increased sedimentation, increased nutrients, increased toxic
contaminants, and an increase in pathogens. The methodology clearly identifies the limitations of
the model when it comes to hydrological impacts. Therefore the model cannot be used to effectively
determine appropriate buffers when the proposed development is going to impact on the hydrology
of a water resource. In particular, open cast and underground mining, required additional
information to determine alternative mitigating measures to address hydrological impacts. In the
case of Zulti South, a comprehensive surface and groundwater assessment is being undertaken to
determine the impact on the wetlands and to identify possible mitigating measures.
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Consideration should be given to exclude all opencast and underground mining from the “Mining”
Sector in the buffer model. While the model may prove to have limitations when it comes to
assessing mining impacts it does, however, provide guidance for the user to further investigate the
key drivers that are likely to impact on the wetland. Therefore, it can still be considered as a useful
tool for the mining sector as long as the limitations are clearly understood.
4.3.3.4.
Core habitat for species of conservation concern
The Critically Endangered Pickersgill reed frog (Hyperiolius pickersgilli) is likely to occur at the site.
The following is recommended (Figure 15):

A core habitat of up to 250m is established around wetland areas in which H. pickersgilli is
present.

Connectivity between wetlands is established and maintained through the proposed core
habitat.
As with the Mount Moreland case study, recommendations could be further refined by targeting
areas of intact habitat and perhaps relaxing requirements where significant transformation through
sugarcane cultivation and/or and Eucalyptus grandi woodlots occur.
Figure 15: Recommended core habitat for Pickersgill reed frog
Note – Although the aquatic impact buffer is not appropriate for the proposed mining activity it is
still evident that core habitat requirements associated with species of conservation concern are
likely to override aquatic impact buffer requirements, suggesting that the biodiversity component
is adequately addressed.
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5. RIVER CASE STUDIES
The model was applied by Gordon O’Brien for the river case studies. The Elands River was selected
as a more appropriate case study to the uMvoti River. While both case studies consider the impacts
of a sugar mill, the Ngodwana mill is closer to the Elands River and dumps effluent onto pastures
which impact the river through runoff. The second river case study was the Thukela River.
5.1. Elands River
The following report documents the outcomes of the testing of the recently developed rivers buffers
model. The model was applied to a case study including the development of the Sappi Ngodwana
pulp and paper mill currently located on the banks of the Elands River, Mpumalanga.
5.1.1.
Site description
The Elands River is a biologically diverse tributary of the Crocodile River in South Africa which is
being used moderately and has been maintained in a suitable integrity state (O’Brien et al. 2014).
Following an accidental spill of paper mill effluent into the Elands River at Ngodwana in 1989
(Kleynhans et al. 1992), the conservation and management of the river received considerable
attention (Kleynhans et al. 1992; Ferreira et al. 2008, Ferreira et al. 2009). The Sappi Ngodwana pulp
and paper Mill, which is a vital part of the economy of the Mpumalanga region, is situated
approximately 40km east of Waterval-Boven adjacent to the main (N4) highway (which bisects the
valley) on the right bank of the Elands River, on the farms known in the past as Roodewal and
Grootgeluk (Figure 16) (Hocking 1987, Weddepohl et al. 1991).
Figure 16: The Sappi Ngodwana pulp and paper mill and effluent fields located adjacent to the
Elands River, Mpumalanga (25°34'43.92"S; 30°39'31.19"E).
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5.1.2.
Description of the Elands River and use by the Sappi Ngodwana pulp and
paper mill
The Elands River is a 5 – 15m wide river with a generally moderate to steep gradient consisting of
extensive riffle and rapid habitats (Roux 2001). Seasonal flow fluctuations are characteristic in
response to rainfall patterns within the Valley. In this portion of Mpumalanga, 90% of the mean
annual precipitation falls during the summer months from October to March (Weddepohl et al.
1991). Subsequently, the highest flows in the Elands River are recorded during these rainfall
months, while the lowest levels are recorded in late spring before the onset of the summer rains
(Weddepohl et al. 1991). The utilisation of the water in the Elands Valley has to an extent exceeded
the actual volume of water currently available to the system for ecological maintenance of the
Elands River and the in-stream flow requirements (IFR’s) of the system have been exceeded (Godfrey
et al. 2000). Water abstraction for domestic and agriculture purposes in the Elands River Valley
primarily comes from the Elands River itself. For industrial purposes, the largest consumer of water
in the Elands River Valley is Sappi. Water is abstracted from the Ngodwana Dam, an artificial
reservoir built on the Ngodwana River, one of the Elands River’s largest tributaries, to specifically
provide for the purposes of the Ngodwana Mill (Hocking 1987).
The Ngodwana Mill is one of the largest and most modern pulp and paper mills in the southern
hemisphere, and the largest single private sector investment in South Africa's history (O’Brien 2003).
The Ngodwana Mill produces 299 000 tons of unbleached pulp, 240 000 tons of fully bleached pulp,
1 250 000 tons of Kraft linerboard and white top linerboard, and 150 000 tons of newsprint per
annum (O’Brien 2003). The mill was originally designed with a closed water system; incorporating
high consistency oxygen bleaching and full filtrate recycle from post oxygen washing. Since the late
1980's, after a detrimental spill into the Ngodwana River (Kleynhans et al. 1992), the Mill has
constantly put tremendous effort into alleviating its effluent discharge. The mill has subsequently
been the first pulp mill in Africa to be accredited with ISO 14001 status. By making use of Sappideveloped technology, combined with state-of-the-art equipment, Ngodwana is the world's only
bleached kraft pulp and paper mill that discharges no effluent directly into the local Elands River.
However, all waste-water is used to irrigate pastures, which as a result which contain high levels of
chlorides, resulting in the aquifer being contaminated.
5.1.3.
5.1.3.1.
Outcomes of field testing
Level of assessment
Both desktop and site-based level of assessment was selected for the Elands River study, which was
informed by expert opinion from as many as eight years of bio-physical and risk assessments of the
Elands River (O’Brien 2003; Ferreira et al. 2008; O’Brien 2012; O’Brien et al. 2014).
5.1.3.2.
Proposed development scenario
The proposed development scenario at the site is the establishment of the Ngodwana pulp and
paper mill (Industrial activity) and the associated effluent irrigation fields. The development includes
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the footprint of the mill and its associated infrastructure, including pipelines to the irrigation
pastures on the southern boundary of the N4.
In this assessment the desktop and site based assessments were considered, the sector selected for
the case study was “Industry” and the sub-sector was selected as “Paper, pulp or pulp products
industries”. The Mean Annual Precipitation (MAP) range selected for the assessment was 8011000mm. The rainfall zone selected for the study was zone “3”.
5.1.3.3.
Preliminary threat ratings
The main operational impacts of the Ngodwana mill relate to the irrigation of effluent (up to
30m3/day) onto irrigation pastures adjacent to the N4. In addition, within the footprint of the mill
itself toxic chemicals, including salts, metals and organic contaminants are produced and
sedimentation threats to the Elands River are also produced. Thus most of the specialist threat
ratings were considered to range between moderate to high, aside from the input of toxic
substances which had a very high threat and sedimentation and turbidity which was scored as a high
impact during construction, but moderate during operation runoff mitigation measures including
vegetation will be established to minimise sedimentation from the mill.
This is the most important component of the excel model. The output of the model is dependent
on the specialist’s assessment of the threat ratings. Differences of opinion can result in different
outputs. The repeatability of the model using the same development example assessed by
different users would need to be tested further.
5.1.3.4.
Sensitivity assessment
The sensitivity assessment only required input of physical information of the Elands River which was
available for this assessment due to research that had been undertaken in the study area (O’Brien
2003; Ferreira et al. 2008; O’Brien 2012). As already mentioned Elands River is a clear flowing,
rejuvenated stream with high sensitivity to sedimentation and toxic contamination (Figure 17). The
steepness of the catchment was considered in this assessment as a major variable affecting buffer
width.
An indication of how important the rating scores are to the overall assessment is required so that
if some variable data is unavailable for the assessment the importance of the variable can be
removed, by assigning a score of “1” for example.
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Figure 17: The Elands River, Mpumalanga during base summer flows. Photo taken upstream of
activity site
5.1.3.5.
Site based modifiers
During the construction phase buffer requirements were considered to differ slightly from the
operational phase. The differences relate to the soli stability differences during construction and
prior to the operational phase of the mill the presence of toxic contaminants. For the assessment,
during the construction phase, the slope of the buffer was considered to be moderate and the basal
cover of vegetation was considered to be high. Soil properties were largely unknown so the
precautionary principle was followed and a moderately low score was assigned. The topography of
the buffer zone was considered to be uniform with few concentrated flow paths. During the
operational phase once the riparian zone has re-stabilised with vegetation the threat of
sedimentation and turbidity declined considerably.
In this case study the toxic contaminant component of the site-based modifiers was required but
unavailable during this assessment. In this case the threat of toxic contaminants entering the
Elands River during the operational phase is high.
5.1.3.6.
Additional mitigation measures
Two mitigation measures were available for the assessment including the reduction in water use
(volume) from the Elands River as the mill will make use of the Ngodwana Dam which was
constructed to store water for the mill. This mitigation measure will ultimately affect the patterns of
flow in the river as high flow events in the Ngodwana River will be removed. Water used by the mill
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is redirected to the Elands River via three major springs (known locally as “Eye’s”) through which
partially treated ground water irrigated onto the irrigation fields percolates through the
groundwater ecosystem and into the Elands River.
5.1.3.7.
Outcomes of the buffers model
The assessment resulted in the determination of buffers for the construction and operational phase
of the Ngodwana pulp and paper mill adjacent to the Elands River (Table 12, Fig 18). Interestingly,
the sit-based buffer requirement for the mill is slightly larger (41m) than the desktop assessment
(39m). This suggests that although slight, the precautionary approach was not adhered to for this
activity in the model which should be addressed.
As expected the buffer requirement for the activity decreases from 41m to 15m during operational
phase in relation to changes in the sedimentation threats of the activity. It is not clear as to how the
buffer zone reduction could be implemented after construction as any developments towards the
river (into the buffer) would require “construction”.
The width of the buffer proposed by this assessment is considered to be suitable and as indicated in
Fig. 3 was not adhered to by the mill. The assessment shows that the buffers proposed for this
activity on the Elands River cannot be met. The Ngodwana mill has however established a retainer
wall along the portion of the Elands River shown in this study to be affected by the footprint of the
paper mill. This wall may be diverting surface runoff into the suitable buffer zone on either side of
the retainer wall.
Table 12: Buffer zone requirements calculated for a construction and operational phases of the
Sappi Ngodwana mill and associated infrastructure along the Elands River, Mpumalanga.
Details of buffer requirement
Construction phase
Desktop Buffer Requirement
Site-Based Buffer Requirement
Site-Based Buffer Requirement (With Additional Mitigation Measures)
Operational phase
Desktop Buffer Requirement
Site-Based Buffer Requirement
Site-Based Buffer Requirement (With Additional Mitigation Measures)
62
Buffer (m)
39
41
41
22
15
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Figure 18: The Sappi Ngodwana pulp and paper mill and effluent fields located adjacent to the
Elands River, Mpumalanga (25°34'43.92"S; 30°39'31.19"E) with buffer zones established in this
study superimposed
5.1.3.8.
Time
The buffer model took about 4 hours to run, with most of the time dedicated to determining
specialist threat classes, sensitivity assessments and site based modifiers.
5.1.3.9.
Scenario testing
To further test the sensitivity of the model outcomes to input variables, a range of additional
scenarios were evaluated which considered variations in climate, river sensitivity and site-based
attributes. Details of these scenarios and resultant outcomes are presented in Table 13, below.
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Desktop
Threat
Rating
Table 13: Outcomes of the scenario based evaluation of the Elands River.
Construction Phase
Alteration to flow volumes reaching the water resource
Alteration of patterns of flows (increased flood peaks) reaching the water resource
Increases in sedimentation and turbidity
Increased nutrient inputs
Increased toxic contaminants
Alteration of acidity (pH) of diffuse surface water inputs
Increase in concentration of salts (salinization) in diffuse surface water inputs
Change (elevation) of temperature in diffuse surface water inputs
Pathogen inputs (i.e. disease-causing organisms)
Operational Phase
Alteration to flow volumes reaching the water resource
Alteration of patterns of flows (increased flood peaks) reaching the water resource
Increases in sedimentation and turbidity
Increased nutrient inputs
Increased toxic contaminants
Alteration of acidity (pH) of diffuse surface water inputs
Increase in concentration of salts (salinization) in diffuse surface water inputs
Change (elevation) of temperaturein diffuse surface water inputs
Pathogen inputs (i.e. disease-causing organisms)
Construction phase
Desktop Buffer Requirement (m)
Site-Based Buffer Requirement (m)
Site-Based Buffer Requirement (With Additional Mitigation Measures) (m)
Operational phase
Desktop Buffer Requirement (m)
Site-Based Buffer Requirement (m)
Site-Based Buffer Requirement (With Additional Mitigation Measures) (m)
64
Specialist Threat Rating
Scenarios
Real
High
Low
L
L
L
VL
L
H
L
H
H
H
L
M
VL
L
H
L
M
M
M
M
N/A
VL
VL
VL
N/A
M
M
M
L
L
L
L
VL
L
VL
VL
H
M
M
M
L
L
L
L
L
M
H
L
M
M
H
L
H
H
H
L
VH
H
H
L
H
VH
VH
VH
H
H
H
H
VL
L
L
L
39
41
41
39
41
41
39
3
3
22
15
15
22
38
38
22
3
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Sensitivity Rating Scenarios
Real
High
Low
1. Changes in water quantity (volumes of flow)
1.25
1.1 Stream order
1
1.2 Channel width
0.5
1.3 Perenniality
1
1.4 Natural runoff potential
2. Changes in patterns of flow (frequency, amplitude, direction of flow)
1.25
2.1 Stream order
1
2.2 Average catchment slope
0.5
2.3 Perenniality
1
2.4 Natural runoff potential
3. Increase in sediment inputs and turbidity
1.25
3.1 Geomorphology zone
0.75
3.2 Soil erodibility potential
1.25
3.3 Average catchment slope
4. Increased inputs of nutrients (phosphate, nitrite & nitrate)
1.25
4.1 Stream order
0.75
4.2 Retention time
0.75
4.3 Geological formations
5. Inputs of toxic contaminants
1.25
5.1 Stream order
0.75
5.2 Soil erodibility potential (K factor)
6. Changes in acidity (pH) from lateral inputs?
1.25
6.1 Stream order
1
6.2 Inherent buffering capacity
7. Changes in concentration of salts (salinization)
1.25
7.1 Stream order
1
7.2 Geological formations
8. Changes in water temperature
1.25
8.1 Stream order
1
8.2 River depth to width ratio
1
8.3 Climate (mean temperature)
1
8.4 River geomorphic setting
9. Increase in pathogen inputs
1.25
9.1 Stream order
1
9.2 River depth to width ratio
0.5
9.3 Level of domestic use
Construction phase
Desktop Buffer Requirement (m)
39
Site-Based Buffer Requirement (m)
41
Site-Based Buffer Requirement MM (m)
41
Operational phase
Desktop Buffer Requirement (m)
22
Site-Based Buffer Requirement (m)
15
Site-Based Buffer Requirement MM (m)
15
65
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
39
41
41
39
41
41
22
21
21
22
15
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5.1.3.10.
Comments
The assessment was simple to evaluate and suitable for this case study. An understanding of the
sensitivity of the ecosystem and potential impacts associated with the land based activity was
crucial. The model did not seem to be very sensitive to changes in threat scores and sensitivity rating
changes as demonstrated in Table 2. Figure 2 presents the buffer zones established in this study on
the footprint of the Sappi Ngodwana mill and associated effluent fields.
5.2. Thukela
5.2.1.
Site description
The Thukela River in KwaZulu-Natal is South Africa’s second largest river with a catchment size of 29
000km2 that has aptly been named for its ferocity (Whitfield & Harrison 2003). Increasing demand
for water related ecosystem services from the Thukela River catchment has resulted in an increase in
pressure on the structure and function of the system (Pienaar 2005). Various water quality and
quantity and habitat impacts associated with ecosystem service use including water abstraction,
waste dilution, waste assimilation, recreational activities, and subsistence fishing occur in the
Thukela system (DWAF 2004). The lower portion of the Thukela River has been characterised as an
ecologically important region of the Thukela Ricer catchment with various social and ecological
values associated with the use of ecosystem services (DWAF 2004). The state of the lower Thukela
River has recently been established as moderately modified (Class C) state (IWR 2004). This suggests
that although key ecosystem processes are occurring, some structure and function aspects of the
ecosystem may be negatively impacted on as a result of altered state of water quality, and or
quantity or habitat driver states (DWAF 2004). Activities associated with ecosystem service use in
the lower Thukela River include water abstraction for domestic use, industries, agriculture, mining,
recreation, waste water treatment and road and rail networks. Many of these ecosystem users
abstract water directly or indirectly (via municipal abstraction works) from the Thukela, Emandeni,
uMsunduze and or Amatikulu rivers and some of them release treated or partially treated effluent
back into these systems. Ecological impacts from the above mentioned resource users have been
reported on the lower Thukela River.
The Thukela River has a Mean Annual Runoff (MAR) of 3 865 x 106 m3. The Mean Annual
Precipitation (MAP) of the entire catchment is 840mm. The MAP is highly variable from more than
1500mm in the Drakensberg to approximately 650mm in the dry central regions (DWAF 2004).
Rainfall is very erratic with long periods of drought alternated with very wet periods. The geology of
the Thukela basin is made up largely (90%) by the Karoo system. The basaltic lavas, Stormberg beds
and Upper Beaufort Beds in the escarpment regions are important for water yields (Rivers-Moore,
2011). The Lower Beaufort beds and Natal Ecca beds in the middle of the basin generate substantial
quantities of dissolved substances, particularly calcium and magnesium bicarbonates, and large
amounts of silt (Rivers-Moore, 2011). The lower reaches are composed of Primitive Granites and
Gneisses, Table Mountain Sandstone and Natal Coastal Ecca Beds and contribute less dissolved
substances than the middle reach but yield higher quantities of chlorides and sulphates (Oliff 1960).
Deliverable 11: Practical Testing / Field Testing Report
Soils resulting from these formations are highly erodible via sheet erosion (IWR Environmental,
2003).
5.2.2.
Description of the lower Thukela River and local land uses and proposed
land-use development.
The portion of the lower Thukela River considered in this study (Fig. 19), lies within the transition
zone between the Maputaland Coastal Belt and the Coastal Belt Grassland zones of KwaZulu-Natal.
The Maputaland Coastal Belt zone is characterised by pockets of various forest types, thickets,
primary and secondary grasslands, extensive timber plantations and cane fields. The KwaZulu-Natal
Coastal Belt Grassland Zone is composed of a mosaic of extensive sugarcane fields, timber
plantations and coastal holiday resorts, with interspersed secondary Aristida grasslands, thickets and
patches of coastal thornveld. Themeda triandra dominated primary grassland still occurs in areas
where natural fire and grazing pressure continued.
In this case study an undisturbed portion of the right (south bank) of the Thukela River is proposed
to be incorporated into an existing intensive dryland sugarcane agriculture operation already
established on the left (north) bank of the river (Fig. 19). In this assessment attributes of the
proposed development and the Thukela River will be considered to propose a buffer zone for both
the north and south banks of the river.
Figure 19: The segment of the lower Thukela River, KwaZulu-Natal during base low flows that was
considered in the study. Scale bar represents 100m. (29°12'9.69"S; 31°25'28.54"E).
5.2.3.
5.2.3.1.
Outcomes of field testing
Level of assessment
Both desktop and site-based level of assessment was selected for the Thukela case study, which was
informed by expert opinion from as many as ten years of bio-physical and risk assessments of the
Thukela River (O’Brien and Wepener, 2009; O’Brien and Venter, 2012).
Deliverable 11: Practical Testing / Field Testing Report
5.2.3.2.
Proposed development scenario
In this case study an undisturbed portion of the right (south bank) of the Thukela River is proposed
to be incorporated into an existing intensive dryland sugarcane agriculture operation already
established on the left (north) bank of the river (Fig. 19). In this assessment attributes of the
proposed development and the Thukela River will be considered to propose a buffer zone for both
the north and south banks of the river.
In this assessment the desktop and site based assessments were considered, the sector selected for
the case study was “Agriculture” and the sub-sector was selected as “Dryland commercial
agriculture”. The Mean Annual Precipitation (MAP) range selected for the assessment was 8011000mm. The rainfall zone selected for the study was zone “4”.
5.2.3.3.
Preliminary threat ratings
The impacts associated with the proposed intensive dryland sugarcane agriculture development
include sedimentation and salinization during the construction phase and flow alterations,
sedimentation, increased toxic contaminants, salinization and temperature impacts. The generic
desktop assessment threat scores were modified to represent the stream order of the lower Thukela
River where the development will take place. This resulted in reductions of flow alteration threat
scores for the construction and operation phase.
This is the most important component of the excel model. A detailed understanding of the study
area is required for the site based assessment.
5.2.3.4.
Sensitivity assessment
The lower Thukela is a large, slow flowing, highly productive and silt laden river with relatively poor
species diversity (Fig. 20). The relative tolerance of the system to changes in patterns of flows,
sedimentation, nutrient inputs, acidity, salinity and water temperatures were reflected by the poor
scores. The river is considered however to be moderately vulnerable to water quality changes which
includes toxicants that were not assessed in this study (portion of the draft model did not include
this component).
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Figure 20: The Lower Thukela River, Mpumalanga during base summer flows. Photo taken
upstream of proposed activity site (Note the established woody vegetation on the right hand
(south) bank of the River (left of the photo)) which is proposed for development.
5.2.3.5.
Site based modifiers
During the construction phase buffer requirements were considered to differ slightly from the
operational phase. The differences relate to the soli stability differences during construction and
prior to the operational phase of the agriculture activity. On an annual basis however, during the
operational phase of the activity the harvesting process of the activity will result in impacts that are
comparable with the construction phase of the study.
For the assessment, during the construction phase, the slope of the buffer was considered to be low
and the basal cover of vegetation was moderate to high. The alluvial properties of the soil were
considered. The topography of the buffer zone was considered to be dominated with uniform with
few concentrated flow paths. During the operational phase once the riparian zone has re-stabilised
with vegetation the threat of sedimentation and turbidity reduced considerably.
5.2.3.6.
Additional mitigation measures
Only one mitigation measure was considered in the study including the construction of a temporary
barrier to restrict sedimentation into the river. Although this mitigation measure reduced the threat
score for sedimentation the buffer zone requirement did not change.
5.2.3.7.
Outcomes of the buffers model
The assessment resulted in the determination of buffers for the construction and operational phase
of the intensive dryland sugar agriculture operation in the lower Thukela River (Table 14, Fig 21).
Deliverable 11: Practical Testing / Field Testing Report
From the assessment the buffer requirement of 15m from the high water mark of the north bank of
the Thukela River has is not achievable. For the South bank where development is proposed a 39m
buffer can be established for the construction phase and reduced to 15m during the operational
phase.
Table 14: Buffer zone requirements calculated for a construction and operational phases of the
Sappi Ngodwana mill and associated infrastructure along the Thukela River, Mpumalanga.
Details of buffer requirement
Construction phase
Desktop Buffer Requirement
Site-Based Buffer Requirement
Site-Based Buffer Requirement (With Additional Mitigation Measures)
Operational phase
Desktop Buffer Requirement
Site-Based Buffer Requirement
Site-Based Buffer Requirement (With Additional Mitigation Measures)
Buffer (m)
39
28
6
22
15
15
Figure 21: The buffer zones proposed in this study to be established for the proposed dryland
sugarcane agriculture development and the Thukela River for both the north and south banks of
the river. The existing sugarcane plantation on the north bank is highlighted in the figure.
5.2.3.8.
Time
The buffer model took about 4 hours to run, with most of the time dedicated to determining
specialist threat classes, sensitivity assessments and site based modifiers.
Deliverable 11: Practical Testing / Field Testing Report
5.2.3.9.
Scenario testing
To further test the sensitivity of the model outcomes to input variables, a range of additional
scenarios were evaluated which considered variations in climate, river sensitivity and site-based
attributes. Details of these scenarios and resultant outcomes are presented in Table 15, below.
Desktop
Threat
Rating
Table 15: Outcomes of the scenario based evaluation of the Thukela River.
Construction Phase
Alteration to flow volumes reaching the water resource
Alteration of patterns of flows (increased flood peaks) reaching the water resource
Increases in sedimentation and turbidity
Increased nutrient inputs
Increased toxic contaminants
Alteration of acidity (pH) of diffuse surface water inputs
Increase in concentration of salts (salinization) in diffuse surface water inputs
Change (elevation) of temperature in diffuse surface water inputs
Pathogen inputs (i.e. disease-causing organisms)
Operational Phase
Alteration to flow volumes reaching the water resource
Alteration of patterns of flows (increased flood peaks) reaching the water resource
Increases in sedimentation and turbidity
Increased nutrient inputs
Increased toxic contaminants
Alteration of acidity (pH) of diffuse surface water inputs
Increase in concentration of salts (salinization) in diffuse surface water inputs
Change (elevation) of temperaturein diffuse surface water inputs
Pathogen inputs (i.e. disease-causing organisms)
Construction phase
Desktop Buffer Requirement (m)
Site-Based Buffer Requirement (m)
Site-Based Buffer Requirement (With Additional Mitigation Measures) (m)
Operational phase
Desktop Buffer Requirement (m)
Site-Based Buffer Requirement (m)
Site-Based Buffer Requirement (With Additional Mitigation Measures) (m)
72
Specialist Threat Rating
Scenarios
Real
High
Low
L
L
M
L
L
L
M
L
H
VH
VH
L
L
L
M
L
M
M
H
M
VL
VL
L
VL
VL
VL
L
M
N/A
N/A
VL
VL
L
VL
M
M
M
M
L
L
L
M
L
M
H
VH
L
M
M
H
L
M
M
H
L
L
L
M
L
L
L
M
VH
VL
VL
L
H
VL
VL
L
L
39
28
6
39
28
6
39
6
6
22
15
15
22
30
30
22
2
2
Sensitivity Rating Scenarios
Real
High
Low
1. Changes in water quantity (volumes of flow)
1.25
1.1 Stream order
1
1.2 Channel width
0.5
1.3 Perenniality
1
1.4 Natural runoff potential
2. Changes in patterns of flow (frequency, amplitude, direction of flow)
1.25
2.1 Stream order
1
2.2 Average catchment slope
0.5
2.3 Perenniality
1
2.4 Natural runoff potential
3. Increase in sediment inputs and turbidity
1.25
3.1 Geomorphology zone
0.75
3.2 Soil erodibility potential
1.25
3.3 Average catchment slope
4. Increased inputs of nutrients (phosphate, nitrite & nitrate)
1.25
4.1 Stream order
0.75
4.2 Retention time
0.75
4.3 Geological formations
5. Inputs of toxic contaminants
1.25
5.1 Stream order
0.75
5.2 Soil erodibility potential (K factor)
6. Changes in acidity (pH) from lateral inputs?
1.25
6.1 Stream order
1
6.2 Inherent buffering capacity
7. Changes in concentration of salts (salinization)
1.25
7.1 Stream order
1
7.2 Geological formations
8. Changes in water temperature
1.25
8.1 Stream order
1
8.2 River depth to width ratio
1
8.3 Climate (mean temperature)
1
8.4 River geomorphic setting
9. Increase in pathogen inputs
1.25
9.1 Stream order
1
9.2 River depth to width ratio
0.5
9.3 Level of domestic use
Construction phase
Desktop Buffer Requirement (m)
39
Site-Based Buffer Requirement (m)
41
Site-Based Buffer Requirement MM (m)
41
Operational phase
Desktop Buffer Requirement (m)
22
Site-Based Buffer Requirement (m)
15
Site-Based Buffer Requirement MM (m)
15
73
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
1.5
0.5
39
41
41
39
41
41
22
21
21
22
15
15
5.2.3.10.
Comments
The assessment was simple to evaluate and suitable for this case study. An understanding of the
sensitivity of the ecosystem and potential impacts associated with the land based activity was
crucial. The model did not seem to be very sensitive to changes in threat scores and sensitivity rating
changes as demonstrated in Table 15.
6. ESTUARY CASE STUDIES
The model was applied by Janine Adams, in a case study involving the development of irrigated
agriculture on the banks of the Gouritz Estuary situated in the southern cape 33km south-west of
Mossel Bay. The second estuary case study was for the Fafa Estuary. The model was applied by
Meredith Cowie and Janine Adams, for the second case study involving the development of a
hypothetical golf course at the Fafa Estuary situated 90km south west of Durban, KZN. The
Swartkops Estuary was not used as a case study as all land along its banks is developed and a
suitable site for testing could not be found. In addition recent field visits had taken place to the
Gourtiz and Fafa estuaries which provided the necessary site specific knowledge to run the model.
6.1. Fafa Estuary
6.1.1.
Site description
The estuary is situated south of Durban near the iFafa Beach and adjacent to the National Route 2
(Figure 22). The vegetation of the site has been described by Mucina & Rutherford (2006) and
Ezemvelo KZN-Wildlife (Scott Shaw & Escott, 2011) as KZN Coastal Belt comprised of grassland with
remnants of subtropical coastal forest. KZN has a highly dissected, undulating coastline with over 70
small estuaries that are intermittently open to the sea (Mucina & Rutherford, 2006; van Niekerk &
Turpie, 2012). Sugarcane cultivation is one of the main land use practices and has been the main
contributor to the loss of over 50 % of KZN Coastal Belt vegetation (Mucina & Rutherford, 2006).
According to the 2009 National Land Use Map natural, cultivation and urban-build up is present
within the Estuarine Functional Zone (EFZ), currently delineated by the 5 m topographical contour.
Existing developments include the iFafa Marina on the south bank in the middle reaches and a few
residential and resorts in the lower reaches. KZN has a subtropical climate and receives
predominately summer rainfall with a mean annual precipitation (MAP) of 800 to 1 500 mm (KZN
Regional Office 2001). Thus Fafa Estuary falls within Rainfall Intensity Zone 4 (high).
74
Figure 22: Fafa Estuary, situated along the south coast of KZN (red line indicates the 5 m contour).
6.1.2.
Description of the estuary
Fafa Estuary (30°27'17" S; 30°39'13" E) is a relatively small temporarily open/closed estuary with a
large catchment (231 km2). According to the National Biodiversity Assessment (van Niekerk & Turpie,
2012), Fafa Estuary is in a poor ecological condition (D is the Present Ecological State). Its hydrology
is considered ‘good’ as freshwater inflow alteration is minimal; however the physical habitat was
described as ‘poor’ due to medium pressures from pollution, habitat loss and the occurrence of
mining and artificial breaching (van Niekerk & Turpie, 2012).
The estuary is perched with steep channels and narrow riparian areas. High river inflow velocities
have caused excessive sedimentation and nutrient enrichment in this system, which also affects
macrophyte growth. Fafa Estuary has 51ha of estuarine area with reeds and sedges (mainly
Phragmites spp. and Schoenoplectus scirpoides) dominant (8ha) (van Niekerk & Turpie, 2012).
Swamp forest (Hibiscus tiliaceaus) and freshwater mangroves (Barringtonia racemosa) occupies 4.5
ha and submerged macrophytes occupy 1.5ha. However, no submerged macrophytes were visible
during a recent site visit in July 2013. Like most KZN estuaries invasive plants are prevalent in the
floodplain and include the blue gum (Eucalyptus globulus), black wattle (Acacia mearnsii), Brazilian
pepper (Schinus terebinthifolius), beefwood (Casuarina cunninghamiana), castor oil trees (Ricinus
communis) and syringa (Melia azedarach). Problematic herbaceous species include Ageratum
conyzoides, Ageratum houstonianum, Bugweed (Solanum mauritianum), Lantana camara, and Triffid
weed (Chromolaena odorata). Azolla Hydrilla and water hyacinth (Eichhornia crassipes) have invaded
aquatic habitats.
75
Figure 23: The north bank of Fafa Estuary illustrating coastal forest on the slopes and reeds and
sedges fringing the open water
6.1.3.
6.1.3.1.
Outcomes of field testing
Level of assessment
Both desktop and site-based level of assessment was selected for the Fafa Estuary test study, which
was informed by expert opinion and a recent visit to the Fafa Estuary.
6.1.3.2.
Proposed development scenario
The proposed development scenario at the site is to establish a new golf estate. The hypothetical
golf estate development will comprise fairways, a club house, hardened parking areas and surfaced
access roads. The Sector selected in the buffer tool was the “Open space” type and the subsector
was “golf courses- fairways”.
A golf course would consist of greens, fairways and some sort of development such as a clubhouse
or housing development. The model is unclear on what should be chosen as the relevant subsector. In this case study the dominant land use was chosen for the study site i.e. fairways of golf
courses. I would suggest that separate buffers should be determined for each proposed activity
(potentially also including a sub-sector for the club house). The layout could then be adjusted to
cater for the different risks associated with different aspects of the development.
6.1.3.3.
Preliminary threat ratings
The main operational impacts of a golf course are irrigation and the application of
fertilizers/pesticides/insecticides. Thus most of the specialist threat ratings were considered low to
very low, aside from the input of nutrients which had a medium threat and sedimentation and
turbidity which was scored as a medium impact during construction, but low during operation as
grass/vegetation will be planted. Increased toxic contaminants and salinization were rated as low for
76
the operational phase; this is probably a conservative score as the chemicals applied to maintain the
golf course could possibly affect these qualities.
This is the most important component of the excel model. The output of the model is dependent
on the specialist’s assessment of the threat ratings. Differences of opinion can result in different
outputs. The repeatability of the model using the same development example assessed by
different users would need to be tested further.
6.1.3.4.
Sensitivity assessment
The sensitivity assessment was straightforward requiring just the input of information on the
system. As already mentioned Fafa Estuary is turbid, 51ha in area, shorter than 5m in length and
supplied by an intermittent river (it is likely that flow is maintained throughout the year although at
much reduced flows in winter). KZN estuaries tend to be perched and thus are more frequently
closed. According to Begg (1978), Fafa Estuary is closed 96% (i.e. > 80%) of the time. The natural
runoff potential was selected as ‘moderate’. Submerged macrophytes have been recorded in Fafa
Estuary, although present occurrence is unlikely. Domestic use of the estuary is likely to be low as
only a few resorts and houses are located adjacent to the estuary.
Guidance on how to fill in the sensitivity threat for biodiversity is needed. In the site based
modifier sheet the drop down list for the operational phase activities does not appear (column L).
6.1.3.5.
Site based modifiers
During the construction phase the site was described as having a moderately steep slope with
dominantly non-uniform topography and a grassy vegetation cover considered to be high. The soil
was characterised as sandy loam (moderately textured). The only difference between the
construction and operational phase could be for the vegetation; however it is likely to remain high as
the golf course will have grassed areas and gardens. The site based modifiers would be the same for
the entire site except for the access road that, due to its locality, may have differing slope and
topography.
Site based assessment involves breaking up the delineation line into 100m segments; it was
unclear as to how this was done. Following a project meeting it was subsequently decided that the
delineation line be sub-divided only if there was significant variability in the slope, topography or
vegetation characteristics of the buffer zone. Including the rationale behind the site based
modifiers in the excel file as well as the method of assessment should be considered. I have
noticed that scoring is incorrect for this attribute. Catchments with a low runoff potential should
be rated more highly than those with a high runoff potential.
6.1.3.6.
Additional mitigation measures
The major threats identified for this development were an increase in sedimentation and turbidity
during construction and nutrient and toxic contaminant inputs during the operational phase.
Mitigations include the use of barriers, storage of top soil and limiting the use of chemicals or
77
organic fertilizers to maintain the golf course. However, some fertilizer use would still increase
nutrient input and thus the threat class was still considered to be medium.
6.1.3.7.
Outcomes of the buffers model
Based on the abovementioned selection the following buffers were calculated for the development
of a golf course near Fafa Estuary in KZN (Table 16, Figure 23, 24). According to the site-based
requirement (with additional mitigation measures) the construction phase would require a 8m
buffer and the operational phase a 51m buffer. However, when mitigated the site based buffer
requirement during the operational phase was reduced to 14m.
When the sub-sector was changed to golf courses- tee boxes and putting greens, the desktop buffer
requirement for the operational phase changed to 22m against the fairways subsector of 2m. This is
a more appropriate buffer distance to 2m. All buffers increased when the rainfall intensity class was
changed to 1 or 2.
When the nutrient inputs were changed from high to medium the buffer requirement was reduced
from 51m to 12m, which seemed rather drastic. However this links to the buffer efficiency curves
which demonstrate that quite small buffers are effective but that very large buffers are necessary if
an efficiency of 90-95% is required.
Table 16: Buffer zone requirements calculated for a hypothetical golf course development
alongside Fafa Estuary in KwaZulu-Natal.
Construction
Phase
Buffer Zone
Requirement
Operational
Phase
Desktop Buffer Requirement
15
Site-Based Buffer Requirement
8
Site-Based Buffer
Measures)
8
Requirement (With Additional Mitigation
Desktop Buffer Requirement
2
Site-Based Buffer Requirement
51
Site-Based Buffer
Measures)
14
78
Requirement (With Additional Mitigation
Development area
Estuarine Functional Zone (5 m contour)
Buffer with mitigation
Buffer without mitigation
Figure 24: Site based buffer requirements for Fafa Estuary. The supratidal zone is taken as the 5 m
contour line.
6.1.3.8.
Time required to complete the buffers assessment
The buffer model took about 1.5 hours to run, with most of the time dedicated to determining
specialist threat classes, sensitivity assessments and site based modifiers.
6.1.3.9.
Scenario testing
To further test the sensitivity of the model outcomes to input variables, a range of additional
scenarios were evaluated which considered variations in climate, wetland sensitivity and site-based
attributes. Details of these scenarios and resultant outcomes are presented in Table 17, below.
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Deliverable 11: Practical Testing / Field Testing Report
Table 17: Outcomes of the scenario based evaluation of the Fafa Estuary (biodiversity sensitivity scores excluded)
Scenario
Actual case study
1 (Worst-case climate)
2 (Sensitive estuary)
3: Low sensitivity
Sector
Open Space
Sub-Sector
Golf Courses - fairways
MAP Class
Rainfall Intensity Zone
601 - 800mm
>1201mm
601 - 800mm
601 - 800mm
Zone 4
Zone 1
Zone 4
Zone 4
Threat Ratings
As per test case (Without additional mitigation measures)
Sensitivity Assessment
Estuary
attributes
1.1 Estuary size
50-100 ha
50-100 ha
Small (<10 ha)
Large (>1000 ha)
1.2 Estuary length
5- 10 km
5- 10 km
<5 km
>30 km
1.3 Perenniality
Intermittent
Intermittent
Ephemeral
Perennial
Low
Low
Clear
Turbid
1.4 Natural runoff potential of
Moderate
catchment soils
Moderate
4.3 Water Clarity
Turbid
Turbid
4.4 Mouth closure as a measure of
>80%
flushing / residence time
>80%
4.5
Submerged
present
Yes
Yes
Yes
No
Low
Low
Low
Low
Changes in water quality
1.0
1.06
1.25
0.5
Changes in patterns of flow
1.0
1.06
1.25
0.5
Increase in sediment inputs and
turbidity
1.08
1.17
1.50
0.67
Increased inputs of nutrients
1.45
0.65
1.50
0.50
1.17
0.50
macrophytes
9.3 Level of domestic use
Sensitivity
Modifiers
1.20
1.25
Changes in the concentration of
1.08
salts
1.17
Increase in pathogen inputs
1
0.92
80
>80%
<20%
Deliverable 11: Practical Testing / Field Testing Report
Scenario
Actual case study
1 (Worst-case climate)
2 (Sensitive estuary)
3: Low sensitivity
Moderately steep
Moderate
Moderate
Moderate
Vegetation
characteristics
(Construction Phase)
High
High
High
High
Vegetation
characteristics
(Operational Phase)
High
High
High
High
Buffer Assessment
Slope of the buffer
Buffer
attributes
Soil properties
Moderate
Topography of the buffer zone
Dominantly
topography
Increase in sediment inputs and
Site-based
turbidity
1.18
Modifiers
Increased inputs of nutrients
1.17
(Construction)
Increase in pathogen inputs
1.18
Site-based
Modifiers
(Operation)
Moderate
Non-uniform Dominantly
topography
Moderate
Non-uniform Dominantly
topography
Moderate
Non-uniform Dominantly
topography
1.18
1.18
1.18
1.17
1.17
1.17
1.18
1.18
1.18
Increase in sediment inputs and
turbidity
1.18
1.18
1.18
1.18
Increased inputs of nutrients
1.17
1.17
1.17
1.17
Increase in pathogen inputs
1.18
1.18
1.18
1.18
Increase in sediment inputs and
turbidity
8
43
18
2
Increased inputs of nutrients
2
46
2
2
Increase in pathogen inputs
2
5
2
2
Buffer recommendation
Site-Based Buffer Requirements
Construction
Phase
Operational
Phase
8
46
18
2
Increase in sediment inputs and
turbidity
2
21
4
2
Increased inputs of nutrients
46
116
79
6
Increase in pathogen inputs
2
5
2
2
81
Non-uniform
Deliverable 11: Practical Testing / Field Testing Report
Scenario
Buffer recommendation
Comments
Actual case study
1 (Worst-case climate)
2 (Sensitive estuary)
3: Low sensitivity
46
116
79
6
Test case
Buffer requirements are very
Buffer requirements are extremely responsive to estuary
responsive to climate. Buffer
sensitivity. The variability is extreme and should be
distance more than doubles
moderated to a more acceptable level.
in the worst case scenario.
4:
Ideal buffer characteristics 5: Poor condition buffer (Very
(gently sloping natural grassland) steep with poor vegetation cover)
Scenario
Actual case study
Sector
Open Spaces
Sub-Sector
Golf Courses - fairways
MAP Class
601 - 800mm
601 - 800mm
601 - 800mm
Rainfall Intensity Zone
Zone 4
Zone 4
Zone 4
Threat Ratings
As per test case (Without additional mitigation measures)
Sensitivity Assessment
1.1 Estuary size
50-100 ha
50-100 ha
50-100 ha
1.2 Estuary length
5- 10 km
5- 10 km
5- 10 km
1.3 Perenniality
Intermittent
Intermittent
Intermittent
Moderate
Moderate
Turbid
Turbid
4.4 Mouth closure as a measure of
>80%
flushing / residence time
>80%
>80%
4.5 Submerged macrophytes present
Yes
Yes
Yes
Low
Low
Low
Changes in water quality
1.0
1.25
1.25
Changes in patterns of flow
1.0
1.25
1.25
1.4 Natural runoff potential of catchment
Moderate
soils
Estuary attributes 4.3 Water Clarity
9.3 Level of domestic use
Sensitivity
Modifiers
Turbid
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Deliverable 11: Practical Testing / Field Testing Report
Actual case study
4:
Ideal buffer characteristics 5: Poor condition buffer (Very
(gently sloping natural grassland) steep with poor vegetation cover)
Increase in sediment inputs and turbidity
1.08
1.17
1.17
Increased inputs of nutrients
1.20
1.25
1.25
Changes in the concentration of salts
1.08
1.17
1.17
Increase in pathogen inputs
0.92
1
1
Slope of the buffer
Moderately steep
Very gentle
Very steep
Vegetation characteristics (Construction
Phase)
High
Very high
Low
Vegetation characteristics (Operational
Phase)
High
Very high
Low
Soil properties
Moderate
High
Low
Topography of the buffer zone
Dominantly
topography
Uniform topography
Concentrated flow paths dominate
Site-based
Modifiers
(Construction)
Increase in sediment inputs and turbidity
1.18
0.70
1.86
Increased inputs of nutrients
1.17
0.74
1.83
Increase in pathogen inputs
1.18
0.70
1.86
Site-based
Modifiers
(Operation)
Increase in sediment inputs and turbidity
1.18
0.76
1.86
Increased inputs of nutrients
1.17
0.78
1.88
Increase in pathogen inputs
1.18
0.70
1.86
Increase in sediment inputs and turbidity
8
5
13
Increased inputs of nutrients
2
1
4
Increase in pathogen inputs
2
1
4
Buffer recommendation
8
5
13
Increase in sediment inputs and turbidity
2
1
4
46
27
73
2
1
4
Scenario
Buffer Assessment
Buffer attributes
Non-uniform
Site-Based Buffer Requirements
Construction
Phase
Operational Phase Increased inputs of nutrients
Increase in pathogen inputs
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Deliverable 11: Practical Testing / Field Testing Report
Scenario
Buffer recommendation
Comments
Actual case study
4:
Ideal buffer characteristics 5: Poor condition buffer (Very
(gently sloping natural grassland) steep with poor vegetation cover)
46
27
Test case
Buffer requirements are moderately sensitive to changes in buffer
characteristics. Poor condition buffer requirements were more than
double when compared with ideal buffer characteristics.
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6.1.3.10.
Comments
The Excel document could be made more user friendly- potentially directing the user from the one sheet to
the next so that they know exactly what needs to be filled in. Simple things such as adjusting the sub-sector
drop down to only the chosen sector’s subsectors, spelling mistakes, not having drop down lists for every cell
required complicate the use of the model. In Sheet 4 regarding Mitigation Measures, it seems redundant to
ask if there are additional mitigation measures, rather it should be filled in the description column. These
comments were included in the overall summary table in the Gouritz Estuary case study.
6.2. Gouritz Estuary
6.2.1.
Description of the estuary
The mouth of the Gouritz Estuary is situated at 35o21’ S; 21o 53’E and the system is permanently open to the
sea; it is marine-dominated and extends for about 8km to the causeway at “Die Eiland”. The health of the
estuary is influenced by catchment activities (water abstraction, siltation and infestation by alien plants). The
Gouritz Estuary is a channel like system with the absence of an extensive flood tidal delta or intertidal salt
marshes. Figure 24 indicates the lateral boundary of the estuary which is taken as the 5 m contour line. The
proposed development (i.e. irrigated agriculture) will take place inside of this boundary in a degraded
floodplain as this land is owned by a farmer. Morphology of the Gouritz Estuary is comparable to the
Gamtoos and Sundays estuaries in the Eastern Cape. The fringing estuarine vegetation consists of supratidal
salt marsh with Sarcocornia pillansii as the dominant species. The salt marsh covers approximately 21ha. In
the middle-upper reaches reeds and sedges fringe the estuary channel. Activities that degrade the Gouritz
Estuary habitat include coastal developments, off-road driving, boating, overfishing, trampling on salt
marshes, livestock grazing and a weir that obstructs river flow to the estuary. These activities damage the
salt marshes, destroy riparian vegetation, and cause severe bank collapse and erosion and impact on flow
dynamics. Much of the natural riparian vegetation has been cleared in places right up the edge of the river
for the cultivation of crops. These lands wash away periodically during floods resulting in a loss of topsoil
(Grindley 1989). Areas of the floodplain have been used for agriculture where ploughing has removed
vegetation and in some areas overgrazing occurs.
The Gouritz Estuary is ranked 50th out of 247 South African estuaries in terms of its conservation importance
(Turpie and Clark 2007). According to the National Biodiversity Assessment the estuary has a “C” ecological
health category which represents a moderately modified system. A loss and change of natural habitat and
biota have occurred but the basic ecosystem functions and processes are still predominantly unchanged. The
recommended ecological category was a “B” and it was recommended that 50% of the estuary margin be
protected (Van Niekerk and Turpie 2012). It is an important nursery area for many species of fish which are
dependent on the estuary for part of their life cycle.
The MAP class was 0-400 mm and the rainfall intensity zone was selected as Zone 3, i.e. some likelihood of
heavy storms. The catchment of the Gouritz Estuary is situated in the arid to semi-arid interior of the
southern Cape. About 1-3 rain days per month can be expected and 10 to 20 thunderstorms occur per year
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Deliverable 11: Practical Testing / Field Testing Report
where one occasional heavy storm can account for as much as half the normal annual rainfall (Heydorn
1989). Rainfall occurs from April to September and the reported MAP range is 270-350 mm.
Changing the Rainfall intensity Zone from 3 to 1 or 4 did not change the buffer width. This parameter
needs to be investigated further. The buffer width only changed when the rainfall was increased to greater
than 1000mm.
6.2.2.
6.2.2.1.
Outcomes of field testing
Level of assessment
The model was tested for both the desktop and site based assessment. The desktop assessment only
considers the worst case scenario whereas the site based assessment considers different sub-sectors.
6.2.2.2.
Proposed development scenario
The proposed development tested was for irrigated agriculture on the banks in the middle reaches of the
estuary (Figure 25). The sector chosen in the model was agriculture and the sub-sector was irrigated
commercial cropland. The main crops would be lucerne, wheat, oats and other grains for cattle feed. This
would take place on the steep banks adjacent to the estuary channel. Original vegetation in this area would
have been Strandveld and Renosterveld which would be naturally sparse in cover because of the low rainfall
in the area. The development is planned directly adjacent to the water resource in this case the salt marsh
and estuary channel and the sub-sector “irrigated agriculture” thus had the dominant impact. Figure 26
indicates the estuary channel, intertidal and then supratidal salt marsh distributed along an elevation
gradient. The vegetation map indicates that the proposed development will occur in a disturbed estuarine
floodplain area (Figure 27). The development site is not of uniform topography. In some areas there are
steep banks that show signs of erosion (Figure 28).
Activity sector on the first sheet should be linked to the corresponding sub-sector. The starting point used
for delineating aquatic impact buffers varies according to the water resource. For example for rivers this is
from the outer edge of the active channel, for wetlands the edge of the temporary zone and for estuaries
the upper edge of the supratidal zone. In many cases the 5m contour or lateral boundary of the estuary is
greater than that of the supratidal zone. The Gouritz Estuary case study is an example of a development
proposed within the 5m contour line on degraded floodplain as this land is currently owned by a farmer
and the development would indicate a change in land use practise.
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Figure 25: Location of the Gouritz Estuary indicating the development site (yellow polygon) in the middle
upper reaches; the estuary channel and 5 m contour line in blue.
Figure 26: Intertidal and supratidal salt marsh at the proposed development site which would occur
beyond the fence.
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Figure 27: Vegetation map for the Gouritz Estuary. The proposed development will occur in degraded
floodplain.
Figure 28 A & B: Shows the topographical variability of the site; some areas have steep eroding banks.
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Deliverable 11: Practical Testing / Field Testing Report
6.2.2.3.
Preliminary threat ratings
The specialist threat rating was considered to be low for flow and flow patterns. Increases in sedimentation
and turbidity, increased nutrient inputs and increased toxic contaminant inputs were all considered to be
high for this activity. The desktop threat class was medium for contaminants during operation however this
should be changed to high because of the risk of herbicides and pesticides to the estuarine biota. Changes in
acidity, salt and temperature were expected to be low to very low.
A table with preliminary threat scores and adjustments with a motivation should be included. Toxic
contaminants need to be included for estuaries.
Suggested changes to threat table:
Open spaces and increase in nutrients should have a medium rather than a low contribution to nutrient
levels; maintenance of grassy areas often requires the use of fertilizers. Water quantity pattern of flow –
high – large volumes of agricultural return flow could change patterns e.g. in some estuaries zero flow is
natural but now consistent baseflow due to agricultural input can occur.
6.2.2.4.
Sensitivity assessment
The sensitivity assessment criteria were easily applied for this activity. The Gouritz is greater than 100ha but
less than 1000ha in size. The estuary is between 10 and 20km in length. It has a perennial river system with
moderate run-off. The channel of the river has cut through sand and limestone down to the underlying
Bokkeveld beds which are exposed near the mouth. The natural run-off potential of the catchment soils was
moderately high. Much silt is carried down the Gouritz River to the mouth during floods (Heydorn 1989).
Violent floods are known to occur intermittently. Gouritz is a turbid estuary although some submerged
macrophytes such as the important seagrass (Zostera capensis) are present (Figure 29). The sensitivity class
for Biodiversity (summary template Sheet 1) was taken as high for all parameters. There are sensitive
Zostera capensis beds in the intertidal zone, the salt marsh is sensitive to the surrounding activities and the
rich intertidal banks colonized by sand prawns are easily disturbed.
The criteria used for the assessment can be included for all estuaries in the country. There is available
information on size, length, perenniality, water clarity, mouth closure and presence of submerged
macrophytes. It is recommended that these data are collated and added to the estuary model in the next
study phase. Mouth closure occurs for <20% of the time. A value of 0 should be added for mouth closure
i.e. some estuaries never close. However there is always the potential for the mouth to close and thus it is
recommended that this stay at 20%. Details for toxic contaminants must be added and the sensitivity of
different estuary vegetation (e.g. salt marsh, reeds sedges) to these parameters investigated. Increase in
pathogen inputs: need to add mouth closure as a parameter. If biodiversity was not considered this
changed the buffer recommendation from 70m (construction phase) to 25m and from 64m to 23m
(operational phase) – Scenario 1. Changing the sensitivity class for Biodiversity from high to low in Sheet 1
decreased the buffer width size for the site based assessment from 70m (construction phase) to 41m and
from 64m to 38m for the operational phase. Each of the threats should be looked at individually and rated
accordingly. This sensitivity class is not necessarily high for each of the threats. The important biodiversity
aspect in the estuary must be highlighted. All parameters on Sheet 2 were given their highest sensitivity
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score of 1.5 (Scenario 2) to see how this changed the buffer size. Biodiversity was not scored for this
scenario. The same development was considered however it was now a small short estuary closed for
greater than 80% of the time with a high run-off potential from the surrounding soils and a high level of
domestic water use. The buffer width for the desktop assessment remained at 74m but the buffer width
for the site based assessment increased for the construction and operational phase indicating the
sensitivity of the worst case scenario. These values reflect the change in sensitivity but the risk remains.
The site based buffer requirement for construction increased from 70 to 117m and from 64 to 108m
(operation). A scenario was also tested for a less sensitive estuary (Scenario 3). This was a large estuary (>
1000ha), greater than 30km in length, with perennial flow and low natural run-off of soils. The estuary
was turbid, the mouth closed for less than 20% of the time and there were no submerged macrophytes.
The level of domestic use was low. There was a drastic decrease in buffer width from 70 to 5m
(construction phase) and from 64 to 4m (operational phase).
Figure 29: Sensitive intertidal areas with eelgrass (Zostera capensis) exposed at low tide.
6.2.2.5.
Site based modifiers
Site based knowledge is needed to apply these criteria. The site is very steep in sections with low vegetation
cover. The site was characterised by moderately fine textured soils with a dominant uniform topography.
During the operational phase vegetation cover would be moderately low as this is a semi-arid area. This is
the only characteristic that would differ between the construction and operational phase.
6.2.2.6.
Additional mitigation measures
Mitigation measures were considered for all the high threat classes. The refined threat classes changed from
a high to a medium threat. The site based buffer requirements with the mitigation measures were
significantly reduced from 70m (construction phase) to 19m and from 64m (operation phase) to 18m.
Changing the threat from high to medium significantly reduced the required buffer zone. Mitigation
measures concentrated on sedimentation and turbidity and changes in water quality. Irrigated agriculture is
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expected to increase nutrient inputs to the estuary. Toxic contaminants in the form of herbicides and
pesticides would be a problem as well as salts as the area is dry. The mitigation methods are documented in
Appendix H.
The large change in the buffer width in response to mitigation measures assumes that these measures will
be implemented and carefully managed which is mostly not the case in the reality. Temperature and pH
which is currently not considered for estuaries must be added. A draft user-friendly look-up list of
appropriate mitigation measures for different impact types should be considered, depending on the type
of activity being proposed. This look-up list will be further developed during the testing phase. This should
be added to the excel model to assist users.
6.2.2.7.
Outcomes of the buffer model
The aquatic impact buffer was delineated in relation to the estuary boundaries and proposed development
site. Set-back requirements for water resource protection are then defined and mapped as the maximum of
either the water resource boundary (i.e. the 5m contour line) or the aquatic impact buffer zone. For the
Gouritz Estuary case study the buffer zone was mapped inland from the supratidal salt marsh but within the
5m contour line (Figure 30). The operational buffer requirements were shown.
Outcomes of the buffers model applied to the Gouritz Estuary are summarised in Table 18. The desktop
buffer requirement provided by the model was 74m for both the construction and operational phase. The
desktop buffer estimation represents the worst case scenario for the sub-sector and was therefore higher
than the site based buffer assessment. If the sub-sector was changed to dryland agriculture there was a
significant decrease in the required buffer zone which suitably indicates the sensitivity of the model to
different sub-sectors; in this case irrigated versus non-irrigated agriculture.
The site based buffer requirement was slightly lower than the desktop buffer requirement (74m) for both
the construction (70m) and operational phase (64m). For the construction phase the site based risk class for
flow volume and pattern were medium for the desktop assessment whereas this was low for the site based
assessment. This adequately represents the precautionary principle for the desktop approach.
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Development area
Supratidal boundary
Buffer with mitigation
Buffer no mitigation
Figure 30: Map indicating the recommended aquatic impact buffer zone for the proposed development of
irrigated agriculture along the banks of the Gouritz Estuary.
Table 18: Summary of buffer model outputs for the Gouritz Estuary case study.
Buffer
Recommendations
Desktop buffers
Site-based buffers
Final buffers
6.2.2.8.
Construction
Buffer Width
(m)
Operation
Buffer
Width (m)
74
74
70
19
Comments
Desktop buffer requirements were appropriately conservative
when the worst-case sub-sector is chosen.
64
Buffer width was reduced during the operation phase as
there would be greater vegetation cover, less run-off and
sediment input.
18
The inclusion of mitigation measures reduced the final buffer
widths for the sites, reflecting the reduced threat levels
anticipated should additional mitigation measures be
implemented. Research suggests that a 15m buffer is likely to
be 80% effective in trapping sediment. However there is little
information to say whether this buffer width would be
effective in controlling nutrient and toxin inputs from the
nearby irrigated agriculture.
Time required to complete the buffers assessment
The time will vary depending on whether the site based information is collated or whether you have to go
and find it and put it together before the assessment can be run. Assuming that all information is available
the most time consuming component was the adjustment to the threat ratings based on site specific
characteristics. The overall time taken to complete the excel model is approximately 2 hours.
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6.2.2.9.
Scenario testing
A range of additional scenarios were evaluated which considered variations in climate, estuary sensitivity
and site-based attributes. Details of these scenarios and resultant outcomes are presented below.
Table 19: Outcomes of the scenario evaluation for the Gouritz Estuary case study.
4: Ideal buffer
characteristics (gently
sloping natural grassland)
5: Poor condition buffer
(Very steep with poor
vegetation cover)
Scenario
Actual case
study
Sector
Agriculture
Sub-Sector
Irrigated commercial cropland
MAP Class
<400 mm
<400 mm
<400 mm
Rainfall Intensity Zone
Zone 3
Zone 3
Zone 3
Threat Ratings
As per test case (Without additional mitigation measures)
Sensitivity
Assessment
Estuary
attributes
Overall size
100-1000 ha
100-1000 ha
100-1000 ha
Length
10-20 km
10-20 km
10-20 km
Perenniality
Intermittent
Intermittent
Intermittent
Natural
run-off
potential
of
catchment soils
Moderately
high
Moderately high
Moderately high
Water clarity
Turbid
Turbid
Turbid
Mouth closure
< 20%
< 20 %
< 20 %
Submerged
macrophytes
present
Yes
Yes
Yes
Level of domestic
use
Low
Low
Low
0.92
0.92
0.92
Increased inputs of
nutrients
0.90
0.90
0.90
Increase in pathogen
inputs
0.75
0.75
0.75
Slope of the buffer
Very steep
Very Gentle
Very steep
Vegetation
characteristics
(Construction Phase)
Moderately
Low
Very high
Low
Vegetation
characteristics
(Operational Phase)
Low
High
Low
Soil properties
Moderately
Uniform topography
Moderately textured
Increase in sediment
inputs and turbidity
Sensitivity
Modifiers
Buffer
Assessment
Buffer
attributes
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4: Ideal buffer
characteristics (gently
sloping natural grassland)
5: Poor condition buffer
(Very steep with poor
vegetation cover)
Dominantly
uniform
topography
Dominantly
topography
Dominantly
topography
Increase in sediment
inputs and turbidity
1.59
0.79
1.55
Increased inputs of
nutrients
1.58
0.74
1.58
Increase in pathogen
inputs
1.59
0.79
1.55
Increase in sediment
inputs and turbidity
1.45
0.85
1.55
Increased inputs of
nutrients
1.46
?
1.58
Increase in pathogen
inputs
1.59
0.79
1.55
Increase in sediment
inputs and turbidity
40
20
39
Increased inputs of
nutrients
70
33
70
Increase in pathogen
inputs
3
2
3
Buffer
recommendation
70
33
70
Increase in sediment
inputs and turbidity
36
21
39
Increased inputs of
nutrients
64
38
70
Increase in pathogen
inputs
3
21
3
Buffer
recommendation
64
38
70
Test case
The model is responsive to local site attributes, with buffer
zones decreasing when site conditions changed from a
steep (test case) to a gentle slope with high vegetation
cover. There was little difference between the test and
poor condition buffer as this was similar to the test study.
Actual case
study
Scenario
textured
Topography of the
buffer zone
Site-based
Modifiers
(Construction)
Site-based
Modifiers
(Operation)
uniform
uniform
Site-Based
Buffer
Requirements
Construction
Phase
Operational
Phase
Comments
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Table 20: Additional scenarios tested without the biodiversity sensitivity scores.
Scenario
No biodiversity
(Scenario 1)
Sensitive estuary
(Scenario 2)
Low sensitivity
(Scenario 3)
Sector
Agriculture
Sub-Sector
Irrigated commercial cropland
MAP Class
<400 mm
<400 mm
<400 mm
Rainfall Intensity Zone
Zone 3
Zone 3
Zone 3
Threat Ratings
As per test case (Without additional mitigation measures)
Sensitivity
Assessment
Estuary attributes
Sensitivity
Modifiers
Overall size
100-1000 ha
<10 ha
>1000 ha
Length
10-20 km
< 5 km
>30 km
Perenniality
Intermittent
Ephemeral
Perennial
Natural
run-off
potential of catchment
soils
Moderately high
High
Low
Water clarity
Turbid
Clear
Turbid
Mouth closure
< 20%
>80%
< 20 %
Submerged
macrophytes present
Yes
Yes
No
Level of domestic use
Low
High
Low
Increase in sediment
inputs and turbidity
0.92
1.5
0.5
0.90
1.5
0.5
Increase in pathogen
inputs
0.75
1.5
0.5
Slope of the buffer
Very steep
Very steep
Very steep
Vegetation
characteristics
(Construction Phase)
Moderately Low
Moderately low
Moderately low
Vegetation
characteristics
(Operational Phase)
Low
Low
Low
Moderately
textured
Moderately textured
Moderately textured
Dominantly
uniform
topography
Dominantly
topography
Dominantly
topography
Increase in sediment
inputs and turbidity
1.59
1.59
1.59
Increased
1.58
1.58
1.58
Increased
nutrients
inputs
of
Buffer
Assessment
Buffer attributes
Soil properties
Topography
buffer zone
Site-based
Modifiers
(Construction)
of
inputs
the
of
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No biodiversity
(Scenario 1)
Sensitive estuary
(Scenario 2)
Low sensitivity
(Scenario 3)
Increase in pathogen
inputs
1.59
1.59
1.59
Increase in sediment
inputs and turbidity
1.45
1.45
1.45
Increased
nutrients
1.46
1.46
1.46
Increase in pathogen
inputs
1.59
1.59
1.59
Increase in sediment
inputs and turbidity
19
62
39
Increased
nutrients
25
117
74
Increase in pathogen
inputs
3
3
2
Buffer
recommendation
25
117
5
Increase in sediment
inputs and turbidity
17
57
39
Increased
nutrients
23
108
74
Increase in pathogen
inputs
3
3
2
Buffer
recommendation
23
108
4
Test case
Buffer requirements are extremely responsive to
estuary sensitivity. The variability is extreme and
should be moderated to a more acceptable level.
Scenario
nutrients
Site-based
Modifiers
(Operation)
inputs
of
Site-Based Buffer
Requirements
Construction
Phase
Operational
Phase
inputs
inputs
Comments
6.2.2.10.
of
of
Summary of comments and concerns
A number of concerns were encountered during testing of the buffer model. A summary of the main issues
identified during the Gouritz and Fafa estuary studies are documented in Table 21.
Table 21: Summary of comments for the buffer model testing on the Gouritz & Fafa estuaries.
Aspect
considered
Comments / Concerns
Selection of
sector / subsector
Activity sector on the first sheet should be linked to the corresponding sub-sector.
A golf course would consist of greens, fairways and some sort of development such as a clubhouse
or housing development. The model is unclear on what should be chosen as the relevant sub-
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sector. In the Fafa case study the dominant land use was chosen for the study site i.e. fairways of
golf courses.
Desktop Buffer
requirement
Specialist threat
ratings
Sensitivity
assessment
(estuary)

Desktop buffer requirements seem fair and provided an indication of the types of threats that
could be problematic for agriculture as a sector.

Could include an additional excel sheet with preliminary threat scores and adjustments with a
motivation.

Toxic contaminants need to be included for estuaries.

This is the most important component of the excel model. The output of the model is
dependent on the specialist’s assessment of the threat ratings. Differences of opinion can
result in different outputs. The repeatability of the model using the same development example
assessed by different users would need to be tested further.

The criteria used for the assessment can be included for all estuaries in the country. There is
available information on size, length, perenniality, water clarity, mouth closure and presence of
submerged macrophytes. It is recommended that these data are collated and added to the
estuary model in the next study phase.

A value of 0 should be added for mouth closure i.e. some estuaries never close. However there
is always the potential for the mouth to close and thus it is recommended that this stay at
<20%.

Details for toxic contaminants must be added and the sensitivity of different estuary vegetation
(e.g. salt marsh, reeds sedges) to these parameters investigated.

Increase in pathogen inputs : need to add mouth closure as a parameter.

Guidance on how to fill in the sensitivity threat for biodiversity is needed in the excel file.
Sensitivity
assessment
(biodiversity)

Biodiversity features were rated as high for all estuary features. This aspect was developed in
the model to include species of special concern but this has not been applied in this manner for
the estuary case study. This aspect needs further investigation for implementation in the
estuary buffer model and supporting report.
Preliminary
buffer
requirements
(excludes local
site attributes)

There is a definite need for specialist refinement of the preliminary threat ratings and buffer
widths outputted by the model particularly in relation to the lateral estuary boundary.

The buffer width only changed when the rainfall was increased to greater than 1000mm. This
will need to be investigated further to ensure that there is sensitivity to different climatic zones.

Check the scores for soil properties, error in cell J16, Sheet 3.

Some of the scores not being taken over automatically between other threat types.

Consider including the rationale behind the site based modifiers in the excel file.

This may need to be considered for the estuary assessment when the topography of the site is
very different over 100m of the bank length.

The site-based buffer requirement without any mitigation appeared adequate.

The large change in the buffer width in response to mitigation measures assumes that these
measures will be implemented and carefully managed which is mostly not the case in reality.

Temperature and pH were not considered for estuaries but should be added to the excel model
so that it is consistent with and as comprehensive as the wetland and river models.

A look-up list of appropriate mitigation measures for different impact types should be added to
Site based
modifiers
Sub-division of
buffer units
Site-based
buffer
requirements
Additional
Mitigation
Measures
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the excel model to assist users.

The starting point used for delineating aquatic impact buffers varies according to the water
resource. For estuaries this is the upper edge of the supratidal zone. In many cases the 5m
contour or lateral boundary of the estuary is greater than that of the supratidal zone. The
Gouritz Estuary case study is an example of this where development is proposed within the 5m
contour line on degraded floodplain. The geographical boundaries of the estuary need to be
considered when the final buffer width is considered.

It was difficult to assess whether the final buffer width (including mitigation) proposed for the
Gouritz Estuary test study would be effective in controlling nutrient and toxin inputs from the
nearby irrigated agriculture. Local research is needed to quantify these aspects.

No species of conservation concern were identified for this site. These protected species need
to be identified for estuaries and details on them included in the next phase of the project.
These species may include crocodiles, hippos and certain bird species that utilise the estuarine
riparian zone and require protection of a core habitat for survival.

For each of use it is recommended that a front page on the excel model be added to describe
the necessary steps for completion of the model.

Open spaces and increase in nutrients should have a medium rather than a low contribution to
nutrient levels; maintenance of grassy areas often requires the use of fertilizers.

Water quantity pattern of flow – high – large volumes of agricultural return flow could change
patterns e.g. in some estuaries zero flow is natural but now consistent baseflow due to
agricultural input can occur.
Final buffer
requirements
Species of
conservation
concern
Overall
Suggested
changes to
threat table
7. SENSITIVITY ANALYSIS AND FURTHER REFINEMENT OF THE
BUFFER ZONE MODELS
7.1. Focus of assessment
The focus of this assessment was to assess the sensitivity of the buffer zone models to primary input
parameters and where necessary, to refine the buffer zone tools to ensure that outcomes correspond with
expected outcomes documented in scientific literature.
7.2. Approach to assessment
In order to test the outcomes of the model, a wide range of potential scenarios were simulated using a
simplified version of the buffer zone tool. This involved creating a separate spreadsheet where buffer zone
outcomes were linked to the following key parameters:

Climatic Risk Score: This reflects the impact of MAR and rainfall intensity on storm flows which is
regarded as a key driver of diffuse source inputs.

Sensitivity of the water resource: This reflects the susceptibility of the water resource to impacts by
diffuse source pollutants.

Site-based attributes: This reflects variability in the efficiency of buffer zones in trapping diffuse
source pollutants based on a range of buffer zone attributes.
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In order to simulate the full range of possible outcomes, best-case and worst-case scenarios were
considered, together with a middle-of-the-road scenario.
The outcomes of the model under various scenarios were initially evaluated subjectively by comparing
outcomes against expectations and available literature (Appendix J). Graphs were also generated for each of
the buffer functions considered (sediment trapping, nutrient removal and pathogen removal). These
showed the relationship between (i) initial threat scores (linked to landuse activities) and recommended
buffer widths and (ii) refined risk scores and associated buffer zone requirements. These graphs clearly
indicated the variability in buffer outcomes of the model in response to changes in the suite key input
parameters. By maintaining certain variables constant, it was also possible to assess the influence of each of
the key input variables on buffer outcomes.
Based on the various simulations, concerns with the initial draft model were identified. A range of potential
changes to the model were then made and outcomes were systematically evaluated by comparing these two
expected outcomes based on available literature. Once acceptable results were achieved, these were
integrated into a revised version of the buffer zone tool (Appendix K). Refinements made as a result of this
sensitivity assessment were then incorporated into the updated version of the models for application in
selected test-cases.
7.3. Outcomes of the draft buffer zone tool
7.3.1.
Sensitivity of outcomes to climatic factors
Based on initial model outputs, it was evident that climate had a small but noticeable effect on modelled
outcomes. In climates characterized by high MAP and rainfall intensities, buffer requirements were typically
twice as high as those under arid conditions with low rainfall intensities.
This relationship is presented graphically in Figure 31, below and was derived by maintaining other input
parameters constant while varying climatic factors.
Sediment Retention
60.0
50.0
50.0
Buffer Requirement
Buffer Requirement
Sediment Retention
60.0
40.0
30.0
20.0
10.0
0.0
y = 69.643x2 - 23.071x + 3.6
40.0
30.0
20.0
10.0
0.0
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0
Threat Score
0.2
0.4
0.6
Risk Score
99
0.8
1
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Nutrient Inputs
Nutrient Inputs
120.0
120.0
100.0
100.0
Buffer Requirement
Buffer Requirement
y = 176.79x2 - 91.643x + 13.6
80.0
60.0
40.0
20.0
80.0
60.0
40.0
20.0
0.0
0.0
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0
0.2
0.4
Threat Score
Pathogen removal
0.8
1
1.2
1
1.2
Pathogen removal
35.0
35.0
30.0
30.0
Buffer Requirement
Buffer Requirement
0.6
Risk Score
25.0
20.0
15.0
10.0
5.0
y = 35.714x2 - 6.8571x + 1.6
25.0
20.0
15.0
10.0
5.0
0.0
0.0
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0
Threat Score
0.2
0.4
0.6
0.8
Risk Score
Figure 31: Responsively of the modelled buffer recommendations in response to variability in climatic
attributes.
While there is little scientific justification for this range in values, the importance of climatic factors in driving
storm water runoff is well established. This relationship is well established in the model with risk and
associated buffer requirements clearly responding to changes in climatic factors under a range of threat
scenarios.
7.3.2.
Sensitivity of outcomes to the sensitivity of water resources
A sound rationale has been provided in the buffer zone guideline for adjusting risk in response to the
sensitivity of the receiving environment. This is in line with international risk methodologies which typically
consider exposure (threat) and effect (sensitivity) in evaluating risk.
When evaluating preliminary model outcomes, it was clearly evident that sensitivity was having a major
influence on buffer zone outcomes. This was caused by the manner in which risk scores are calculated,
being determined by the product of risk and sensitivity scores. This effect is clearly indicated in Figure 32
which shows excessive variability in modelled buffer outcomes for water resources with different
sensitivities under a full range of threat scenarios. This difference is exacerbated under high threat
scenarios, although capping risk scores to a maximum of 1 did limit the upper range of possible buffer
requirements.
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Sediment Retention
60.0
50.0
50.0
Buffer Requirement
Buffer Requirement
Sediment Retention
60.0
40.0
30.0
20.0
10.0
0.0
y = 69.643x2 - 23.071x + 3.6
40.0
30.0
20.0
10.0
0.0
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0
0.2
0.4
0.6
Threat Score
0.8
1
1.2
1
1.2
1
1.2
Risk Score
Nutrient Inputs
Nutrient Inputs
120.0
120.0
100.0
100.0
Buffer Requirement
Buffer Requirement
y = 176.79x2 - 91.643x + 13.6
80.0
60.0
40.0
20.0
80.0
60.0
40.0
20.0
0.0
0.0
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0
0.2
0.4
Threat Score
Pathogen removal
0.8
Pathogen removal
35.0
35.0
30.0
30.0
Buffer Requirement
Buffer Requirement
0.6
Risk Score
25.0
20.0
15.0
10.0
5.0
y = 35.714x2 - 6.8571x + 1.6
25.0
20.0
15.0
10.0
5.0
0.0
0.0
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0
Threat Score
0.2
0.4
0.6
0.8
Risk Score
Figure 32: Responsively of the modelled buffer recommendations in response to variability in the
sensitivity of the receiving environment.
Based on these outcomes, it was clear that the risk calculations needed to be reviewed to narrow the
variability in buffer outcomes in response to sensitivity of the receiving environment.
7.3.3.
Sensitivity of outcomes to site-based attributes
The variability in potential site-based attribute scores is high, with scores ranging from 0.7 (most effective
buffer attributes) to 1.86 (buffers poorly suited to reduce impacts from diffuse source impacts). Based on a
preliminary review of model outcomes, it was quickly apparent that the variability in recommended buffer
requirements was excessive when compared with typical variability encountered in scientific literature and
reviews of buffer zone effectiveness. As for sensitivity, this was particularly problematic under higher threat
scenarios where ranges in outcomes were most variable (Figure 33). The range in outcomes was greater
than that for sensitivity as expected in response to the broader range in potential input values.
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Sediment Retention
60.0
50.0
50.0
Buffer Requirement
Buffer Requirement
Sediment Retention
60.0
40.0
30.0
20.0
10.0
0.0
y = 69.643x2 - 23.071x + 3.6
40.0
30.0
20.0
10.0
0.0
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0
0.2
0.4
0.6
Threat Score
0.8
1
1.2
1
1.2
1
1.2
Risk Score
Nutrient Inputs
Nutrient Inputs
120.0
120.0
100.0
100.0
Buffer Requirement
Buffer Requirement
y = 176.79x2 - 91.643x + 13.6
80.0
60.0
40.0
20.0
80.0
60.0
40.0
20.0
0.0
0.0
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0
0.2
0.4
Threat Score
Pathogen removal
0.8
Pathogen removal
35.0
35.0
30.0
30.0
Buffer Requirement
Buffer Requirement
0.6
Risk Score
25.0
20.0
15.0
10.0
5.0
y = 35.714x2 - 6.8571x + 1.6
25.0
20.0
15.0
10.0
5.0
0.0
0.0
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0
0.2
0.4
Threat Score
0.6
0.8
Risk Score
Figure 33: Responsively of the modelled buffer recommendations in response to variability in site-based
buffer zone attributes.
Given that site-based attributes also fed into the risk score in the draft model, it was clear that the risk
calculations were having too great an influence on the variability in buffer outcomes. It also highlighted an
important point that site-based attributes should not influence the risk score directly but should rather be
used to adjust the preliminary buffer recommendations derived from the initial risk assessment. This
learning was used to adjust the way that final buffer requirements were calculated in the buffer zone model
(See Section 4.2).
7.3.4.
Sensitivity of outcomes to full range of input variables
As expected, the variability in buffer zone outcomes increased further when all three input variables were
varied together (Figure 34). This emphasized the need to reconsider the relative weightings of input
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variables and the manner in which the relationships were formalized in the buffer model. Further details of
the changes integrated into the model in response to this sensitivity analysis are discussed in Section 4.
Sediment Retention
60.0
50.0
50.0
Buffer Requirement
Buffer Requirement
Sediment Retention
60.0
40.0
30.0
20.0
10.0
0.0
y = 69.643x2 - 23.071x + 3.6
40.0
30.0
20.0
10.0
0.0
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0
0.2
0.4
0.6
Threat Score
0.8
1
1.2
1
1.2
1
1.2
Risk Score
Nutrient Inputs
Nutrient Inputs
120.0
120.0
100.0
100.0
Buffer Requirement
Buffer Requirement
y = 176.79x2 - 91.643x + 13.6
80.0
60.0
40.0
20.0
80.0
60.0
40.0
20.0
0.0
0.0
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0
0.2
0.4
Threat Score
Pathogen removal
0.8
Pathogen removal
35.0
35.0
30.0
30.0
Buffer Requirement
Buffer Requirement
0.6
Risk Score
25.0
20.0
15.0
10.0
5.0
y = 35.714x2 - 6.8571x + 1.6
25.0
20.0
15.0
10.0
5.0
0.0
0.0
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0
0.2
Threat Score
0.4
0.6
0.8
Risk Score
Figure 34: Variability in buffer zone recommendations across the full range of possible scenarios.
7.4. Revisions to the draft buffer zone models
This assessment served to highlight a number of weaknesses in the draft buffer zone models which can be
summarized by the following key points:

The model outcomes are too responsive to sensitivity criteria. Outcomes need to be adjusted to
reflect a more acceptable range in buffer recommendations in response to the sensitivity of the
receiving environment.
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
The manner in which site-based attributes have been incorporated in buffer zone calculations is
inappropriate. It should be used to modify preliminary buffer recommendations (derived from
standard risk-buffer zone relationships) rather than being used to modify risk ratings.
These concerns were addressed by first refining the manner in which buffer zone requirements were
calculated and testing various ranges for the sensitivity assessment. This showed that the most reasonable
results were achieved when adjusting the range of sensitivity scores between 0.85 and 1.15. This resulted in
a maximum variation in risk scores of 0.3 under very high threat scenarios with a moderated effect under
lower threat scenarios (Appendix K). A comparison of modelled outcomes of the draft and updated model is
presented and briefly discussed for each of the key input variables (other than climate, which remains
unchanged) used in the buffer zone model.
7.4.1.
Sensitivity of outcomes to the sensitivity of water resources
Figure 35, below, clearly illustrates how the range of buffer zone scores has been refined by adjusting the
range of sensitivity scores. Outputs of the revised model now show that threat is the dominant factor in
determining buffer requirements but that moderate changes in buffer widths are made to accommodate
variation in the sensitivity of the receiving environment to diffuse source inputs.
Draft model
Updated model
Sediment Retention
60.0
50.0
50.0
Buffer Requirement
Buffer Requirement
Sediment Retention
60.0
40.0
30.0
20.0
10.0
40.0
30.0
20.0
10.0
0.0
0.0
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0.20
0.30
0.40
0.50
Threat Score
Nutrient Inputs
0.70
0.80
0.90
1.00
0.80
0.90
1.00
Nutrient Inputs
120.0
120.0
100.0
100.0
Buffer Requirement
Buffer Requirement
0.60
Threat Score
80.0
60.0
40.0
20.0
80.0
60.0
40.0
20.0
0.0
0.0
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0.20
Threat Score
0.30
0.40
0.50
0.60
Threat Score
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Pathogen removal
35.0
30.0
30.0
Buffer Requirement
Buffer Requirement
Pathogen removal
35.0
25.0
20.0
15.0
10.0
5.0
25.0
20.0
15.0
10.0
5.0
0.0
0.0
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0.20
0.30
0.40
Threat Score
0.50
0.60
0.70
0.80
0.90
1.00
Threat Score
Figure 35: Graphs indicating the refinement to buffer recommendations in response to changes in the
range of sensitivity scores included in the model.
Sensitivity of outcomes to site-based attributes
7.4.2.
The revised model now uses the site-based scores to adjust preliminary risk-based buffer outcomes as
illustrated in Figure 36, below. While it is difficult to formally defend the level of variability, this is regarded
as comparable with many of the international reviews which suggest that buffer effectiveness varies
considerably based on local site-based factors. Any deviations up or down are also well supported by
scientific literature as detailed in the section of the guidelines dealing with site-based buffer attributes.
Draft model
Updated model
Sediment Retention
Sediment Retention
60.0
y = 69.643x2 - 23.071x + 3.6
50.0
50.0
Buffer Requirement
Buffer Requirement
60.0
40.0
30.0
20.0
10.0
40.0
30.0
20.0
10.0
0.0
0.0
0
0.2
0.4
0.6
0.8
1
1.2
0.20
0.40
Risk Score
0.60
0.80
1.00
1.20
1.00
1.20
Risk Score
Nutrient Inputs
Nutrient Inputs
120.0
120.0
y = 176.79x2 - 91.643x + 13.6
100.0
Buffer Requirement
Buffer Requirement
100.0
80.0
60.0
40.0
20.0
80.0
60.0
40.0
20.0
0.0
0
0.2
0.4
0.6
0.8
1
0.0
1.2
0.20
Risk Score
0.40
0.60
0.80
Risk Score
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Pathogen removal
Pathogen removal
35.0
35.0
y = 35.714x2 - 6.8571x + 1.6
30.0
Buffer Requirement
Buffer Requirement
30.0
25.0
20.0
15.0
10.0
5.0
25.0
20.0
15.0
10.0
5.0
0.0
0
0.2
0.4
0.6
0.8
1
0.0
1.2
0.20
0.40
0.60
Risk Score
0.80
1.00
1.20
Risk Score
Figure 36: Graphs indicating changes to buffer zone recommendations in response to site-based buffer
zone attributes.
7.4.3.
Sensitivity of outcomes to full range of input variables
The outcomes of the revised buffer zone models under a full range of input values are indicated in Figure 37,
below. This illustrates a greater variability in the range of risk scores together with the responsiveness of the
model outcomes to local site attributes. This variability is regarded as appropriate for local application and
has therefore been incorporated into revised versions of the buffer models.
Draft model
Updated model
Sediment Retention
Sediment Retention
60.0
y = 69.643x2 - 23.071x + 3.6
50.0
50.0
Buffer Requirement
Buffer Requirement
60.0
40.0
30.0
20.0
10.0
40.0
30.0
20.0
10.0
0.0
0.0
0
0.2
0.4
0.6
0.8
1
1.2
0.00
0.20
0.40
Risk Score
0.60
0.80
1.00
1.20
0.80
1.00
1.20
Risk Score
Nutrient Inputs
Nutrient Inputs
120.0
120.0
y = 176.79x2 - 91.643x + 13.6
100.0
Buffer Requirement
Buffer Requirement
100.0
80.0
60.0
40.0
20.0
80.0
60.0
40.0
20.0
0.0
0
0.2
0.4
0.6
0.8
1
0.0
1.2
0.00
Risk Score
0.20
0.40
0.60
Risk Score
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Pathogen removal
Pathogen removal
35.0
35.0
y = 35.714x2 - 6.8571x + 1.6
30.0
Buffer Requirement
Buffer Requirement
30.0
25.0
20.0
15.0
10.0
5.0
25.0
20.0
15.0
10.0
5.0
0.0
0
0.2
0.4
0.6
0.8
1
0.0
1.2
0.00
0.20
0.40
Risk Score
0.60
0.80
1.00
1.20
Risk Score
Figure 37: Variability in buffer zone recommendations across the full range of possible scenarios.
7.5. Conclusions from the sensitivity analysis
This sensitivity assessment proved to be a very useful tool for quickly evaluating model outcomes under a
full spectrum of potential scenarios. This revealed a number of problems with the way final buffer
requirements were calculated. The findings of the assessment were then used to update the buffer zone
tools which are to be applied to selected test cases as part of the field testing component of this project.
8. SUMMARY OF ISSUES / CONCERNS & RECOMMENDATIONS
The project team held a workshop on the 13th and 14th of February 2014 to consolidate findings and clarify
what tasks resulting from the testing of the buffer models need to be undertaken to further refine the
method develop. Table 22 summaries the issues, concerns, challenges and recommendations identified.
Table 22: Summary of issues / concerns & recommendations
ASPECT
CONSIDERED
COMMENTS / CONCERNS

It proved difficult to find each sub-sector within the drop down menu in the Excel
spreadsheet (small text and many subsectors all in one drop down menu).
o

Selection of sector /
sub-sector
Population of
climatic data
DM
Need to refine model to facilitate this process.
A scenario was discussed, where a planned activity included a wide range of
potential sub-sector activities, with different threats (development of a large
paper mill). It was agreed that under such a scenario, each of the planned
landuses should be considered separately and be used to define aquatic impact
buffer zones for each activity. This should then inform where activities are placed
in the final site layout.
o

WHO
IB
It was suggested that it would be good to include further guidance
(potentially with a case study) in the guideline.
It would be good to provide a map of the Rainfall Intensity Zones in the model for
easy reference.
o
IB
Need standard maps (ideally in hard copy and GIS / kml format to inform
assessment).
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ASPECT
CONSIDERED
COMMENTS / CONCERNS

Doug briefly described how climatic factors were used to influence buffer zone
outcomes. The approach was regarded as acceptable despite the lack of technical
justification available.
o

Desktop Threat
Ratings and Buffer
requirements
Specialist threat
ratings

DM
Updated threat ratings to be included in revised models
o
The development was being planned directly adjacent to the water
resource (no buffer in place);
o
The sub-sector assessed is the dominant landuse and occurs at intensities
typical of the sub-sector;
o
Where intensities are variable (e.g. informal development / subsistence
cultivation), the typical realistic worst-case scenario was assessed;
o
In the case of sub-sectors that address linear developments (e.g.
footpaths / roads); threats were assessed based on typical width and
characteristics of the specific sub-sector and associated construction and
operational activities.
IB
DM
Above to be clearly documented in the guideline.
Desktop ratings do not take buffer zone attributes into account and as such,
results are far from precautionary.
o

It was agreed that the approach to integrating climatic factors into the
report should be clearly documented.
When assessing threat, the following assumptions were made:
o

DM
A concern was raised that some of the desktop threat ratings appear to be either
too high or too low for specific sub-sectors. These ratings were therefore
systematically reviewed and updated by the project team following the initial
workshop.
o

WHO
Incorporate worst-case site-based modifier scores into calculations of
desktop buffer requirements.
Threat is probably the most important criteria rated in this model as buffer zone
requirements are very strongly tied to this rating. Whilst the need to allow
desktop threat ratings to be customized is well founded, this assessment needs to
be well informed and be undertaken with appropriate diligence.
o
Need to emphasize the importance of this in the guidelines.
o
Motivation for specialist threat ratings to be included in the model.
There is little guidance provided with regards to modifying the preliminary threat
ratings.
o
Consider how guidelines could be improved to allow users to rate threats
in a more objective manner.
o
Include key considerations to guide specialist threat assessment. This
should include aspects such as: scale of development, slope length &
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ASPECT
CONSIDERED
COMMENTS / CONCERNS
WHO
steepness of land, soil erodibility, typical landuse and management.
o

It is very helpful to have a GIS system available in order to interrogate data and
calculate slopes, wetland vs. catchment sizes, etc.
o


Agreed that team would consider the need for further refinement.
o
Inherent runoff potential of soils requires further rationale/clarification;
o
Vulnerability of the site to erosion is currently based only on slope and size
but soil characteristics could also be included (e.g. presence of dispersive soils,
indications of existing erosion features such as drains/gullies);
o
Level of domestic use – the tool could provide further clarity as to what types
of typical domestic use one can expect under the rationale for this criterion.
o
To refine rationale to improve clarity.

There was a concern that sensitivity could be overestimated or underestimated
due to the spatial variability of the water resource under consideration. Following
further interrogation, it was noted that sensitivity criteria typically apply to the
wetland as a whole. There is therefore little risk of miss-applying the assessment.

Janine indicated that it may be quite straight-forward to capture sensitivity criteria
for all estuaries in a basic spreadsheet. This could then be integrated into the
model to auto-populate the model based on the specific estuary selected.

ALL
A few criteria required further specialist interpretation to decide on ratings. These
included:
o
Sensitivity
assessment
(biodiversity)
DM
Include both rationale and method of calculation in revised models.
Consideration should be given to how the sensitivity modifiers are calculated. It
may be useful to weight each criteria more objectively using pairwise comparison
rather than simply calculating an average of the scores for each criterion.
Alternatively, it may be good to investigate the sensitivity of model outcomes to
recommended buffer widths cited in scientific studies to check that adjustments
are appropriate.
o
Sensitivity
assessment
(wetland)
IB
The usefulness of such a tool should be emphasized in the guideline.
It would be helpful to have quick access in the Excel spreadsheet to a description
of how to calculate catchment/wetland slopes, perimeter, vulnerability to erosion,
etc. This would improve the usability of the tool and help to cut back on time
required for assessments.
o

Include guidance in models.
JA
Janine to see if this is feasible within the next 2 months.
In the case of important biota, the rating of threats requires specialist input
(should be based on the specialists understanding of species sensitivity to specific
impacts).
o
DM
It was agreed that a justification for these threat ratings should also be
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ASPECT
CONSIDERED
COMMENTS / CONCERNS
WHO
documented in the model.

A suggestion was made to include a measure of confidence in the assessment.
Following discussions, it was agreed that this would open the model up to abuse.

An issue regarding rainfall intensity zones was identified and will need to be
addressed to ensure that buffer requirements are adjusted in an appropriate
manner to cater for differences in anticipated stormflows between rainfall
intensity zones.
Preliminary buffer
requirements
(excludes local site
attributes)
o

The need for the guideline to provide clarity on whether the assessment is based
on current buffer characteristics or a worst-case scenario with development (e.g.
steep un-vegetated slope (new platform) vs. gradual well-vegetated slope under
pre-construction scenario) was identified.
o
Provide clarity in method & model

A suggestion was made to consider soil depth (as this affects runoff) and erosion
risk (in the case of sediment inputs) to refine site-based modifiers. Following
discussion, it was agreed that we should keep the model as simple as possible. No
extra criteria are therefore to be added to the site-based assessment unless
specifically identified as necessary to cater for toxic contaminants.

Two errors were identified in the site-based modifiers template. The operational
phase vegetation score was not being carried through appropriately while the
score for soil properties under “Nutrient Inputs” was referencing the incorrect cell.
Site based modifiers
o


Sub-division of
buffer units
DM
To check and update.
Given that most recommended buffer zones will be less that 50m, it is
suggested that this guidance be included in the guideline and model.
IB &
DM
Guidance on whether or not the buffer should be sub-divided for assessment
purposes (to account for local variability) was discussed. The following revisions
were proposed to the guideline and models:
o
o

IB &
DM
No guidance is provided on the width of area / buffer around the wetland to
consider when rating site-based modifiers. Clarity is therefore required to prevent
confusion.
o
Site-based buffer
requirements
DM
Update method and models in consultation with sub-contractor who
undertook the assessment.
Process for evaluating site-based attributes to be refined. This should
indicate that discrete sections of the water resource boundary should be
identified in cases where there is significant variability in slope,
vegetation characteristics and / or local topography of the buffer zone.
Model to be updated to accommodate a range of buffer zone segments if
possible.
Provide further guidance as to which buffer to use (e.g. how relevant is a small
operational buffer if construction buffers are wide?). It was agreed that the
maximum of these buffer requirements should be applied when placing a
development. It is however useful to differentiate between construction and
operational risks as it flags the need to consider alternative mitigation and
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ASPECT
CONSIDERED
COMMENTS / CONCERNS
WHO
management measures.
o

A concern was raised that threat ratings may not be reduced in a precautionary
manner. Whilst justification for reducing threat ratings is required, this could also
be open to abuse.

To counter this and to reduce the risk of pollution following authorization, it was
agreed that a 15m minimum buffer should be applied. This suggestion is based on
a scientific study that investigated the long-term maintenance and effectiveness of
buffer zones (See preliminary report on management of buffer zones).
o
Additional
Mitigation
Measures
IB
Guideline to be updated accordingly

Guideline to be updated to clearly communicate minimum buffer
requirements with a supporting motivation.
A concern was raised that there may be exceptional circumstances when a
reduction in buffer requirements is acceptable. It was agreed that such
recommendations should fall outside of the technical process.
o
No guidance is provided as to mitigation of biodiversity aspects such as noise and
visual disturbance, air borne contaminants etc. to sensitive species. It was agreed
that this should be left up to specialists as it falls outside the scope of this study.

The delineation line for estuaries and rivers was briefly discussed again. It was
agreed that the aquatic impact buffer would be determined from the edge of the
supratidal zone but that setback requirements would be based on the greater of
this line or the 5m contour (estuary boundary).
o

Final buffer
requirements

IB/DM
Ensure that this point is clearly communicated in the guideline with an
example indicating how the final setback line is determined.
DM
A check-box should also be included in the tool to ensure that the 5m
contour and edge of the riparian zone are clearly delineated.
The need to potentially buffer riparian areas was discussed. It was agreed that any
additional setback requirements around riparian areas should be based on
practical management considerations. These could include factors such as
preventing damage during construction, maintaining process value or the need to
manage such areas in a particular manner (e.g. burning of forest ecotones).
o
IB
It was suggested that a footnote be included in the guideline stating that
decisions to increase or decrease the recommended BZ should be left up
to the regulator as part of the decision making process.

o
IB
IB
Guidelines to be updated to emphasize the need to consider these
aspects when deciding on final setback requirements.
There are a number of other practical issues that are not addressed by the buffer
zone model. This includes factors such as other legal obligations (e.g. flood lines,
existing infrastructure located within recommended buffer zones), practical
management considerations (e.g. can the wetland be managed with such a small
buffer) and other potential reasons for establishing a buffer zone (e.g. recreational
space; aesthetic value; “adjustment” space to cater for catchment changes and
increased flood peaks screening of visual/noise impacts for sensitive species, etc.).
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ASPECT
CONSIDERED
COMMENTS / CONCERNS

o
It was agreed that there should be scope to increase setback
requirements to cater for these factors. This needs to be explicitly
included in the guideline.
o
It was agreed that a series of questions (with basic guidance) be included
in the “front-end” of the buffers tools to prompt users to ensure that
these aspects are considered.
In the absence of species information sheets, a suggestion was made to potentially
include a range of buffer widths recommended internationally for different groups
of species.

Following discussion, it was agreed that this would be open to abuse and would be
used without appropriate specialist input. The need for specialist input when
establishing setback requirements for species of conservation concern was
therefore supported.

The need to clearly indicate that sub-surface activities are not considered in the
threat assessments or buffer requirements was emphasized. As such, buffer
requirements would exclude most mining operations which can have a significant
impact on the hydrology of the landscape. The threat assessment is therefore
explicitly restricted to surface activities (spoils, gear, infrastructure etc.).
General

o
Guideline to be updated to ensure that this is explicitly stated.
o
Reference should be made to hydrological buffers typically used to limit
impacts to groundwater.
The importance of management objectives in defining buffer zone requirements
was discussed. It was agreed that this cannot be explicitly included in the model.
A meeting with Chris Dickens was proposed to determine how this is / is not used.

It was agreed that Janine would investigate and report back on her
recommendations.
It was noted that details on toxic contaminants had still not been included in the
method and model. Following discussion, it was agreed that this should be broken
down into two broad groups, namely organic contaminants and heavy metals.
o
Sensitivity analysis
IB
IB/DM
JA
The need to include temperature and pH in the estuaries model was briefly
discussed.
o

DM
It was agreed that an updated / refined front-end or output should be
developed to improve the usability and transparency of the outcomes of
the assessment.


DM
It was agreed that further consideration should be given to how buffer zone
requirements are documented in specialist reports. The current format of the
model is not user friendly for reporting purposes.
o
Species of
conservation
concern
WHO
Further development of these components will be pursued following the
field testing phase.
Preliminary results from applying the crystal ball software to the wetland model
were presented. Results were difficult to interpret and it was agreed that clear
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ASPECT
CONSIDERED
COMMENTS / CONCERNS
questions needed to be phrased before running the analysis.

It was agreed that Doug and Gordon would meet to discuss the way forward.

Budget constraints limited the number of case studies select for each water
resources, and case studies were selected based on available data and specialist
knowledge of the sites.

Involvement of additional specialists was limited.

Guidelines defining different types of developments will be included in the User
Manual.

Ensure the limitations of the desktop assessment are clearly indicated in the User
Manual.

Ensure that guidelines are provided in each of the buffer models.

Consider providing guidance on the ‘time factor’ in the buffer models.

Consideration will be given to including turbidity.

A section on limitations should be included in the User Manual.

Guidance on the use of the buffer models will be provided in the User Manual.

Ensure that this is clearly described in the technical report and User Manual.

Guidance on other key drivers will also be included in the model.

Ensure this is clearly stated in the models, technical report and User Manual.

The User Manual should make reference to this.

A distance of 15m has been proposed and will be investigated as part of the
testing phase.

Buffering large floodplains will be taking into consideration.

Noted. Check model to ensure units are included where relevant.

Specialist input is required for the biodiversity component and the threat ratings
for the proposed development. Potentially, this needs to be assessed.

For rivers, it was suggested that stream bank stability be considered. Noted. This
will be taking into consideration.

Scale and timing of impacts will be identified as criteria that need to be considered
when determining buffer requirements.

Management of buffers is addressed in the technical report and will be included in
the User Manual.

Guidance on considering season changes will be considered and where relevant
included in the User Manual and the appropriate models.

The model will provide guidance for the user to adjust threat scores for
developments of varying sizes.
Challenges
Outcomes of the
WRC development
workshops to be
considered
Outcomes of the
SASAQS
development
workshop to be
considered
Outcomes of the
NWI development
workshop to be
considered
113
WHO
DM
ALL
ALL
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9. REFERENCES
Begg, G. 1978. The Estuaries of Natal: A resource inventory report to the Natal Town and Regional Planning
Commission conducted under the auspices of the Oceanographic Research Institute, Durban. Natal Town
and Regional Planning Report Vol. 41.
Boyd, L. 2001. Buffer Zones and Beyond: wildlife use of wetland buffer zones and their protection under the
Massachusetts Wetland Protection Act. Department of Natural Resources Conservation, University of
Massachusetts, Massachusetts.
Ferreira, M., Wepener, V., van Vuuren, J.H.J. 2008. The effect of paper mill activities on the fish community
structure of Elands River, Mpumalanga. Suid-Afrikaanse Tydskrif vir Natuurwetenskap en technologie. 27, 83
– 94.
Ferreira, M., Wepener, V., van Vuuren, J.H.J. 2009. Spatial and temporal variation in the macroinvertebrate
community structure of the lower Elands River, Mpumalanga, South Africa. African Journal of Aquatic
Science 34, 231 – 238.
Ficetola, G.F., Padoa-Schioppa, E., De BErnardi, F. 2008. Influenc of landscape elements in riparian buffers on
the conservation of semiaquatic amphibians. Conservation Biology 23, 114 – 123.
Heydorn, H.J. 1989. Estuaries of the Cape Part II: Synopses of available information on Individual systems.
Report No. 38: Gourits (CSW 25). CSIR Research Report 437. Stellenbosch, South Africa.
Hocking, A. 1987. Paper Chain, the story of Sappi. Hollard South Africa, Bethulie, Orange Free State.
Kleyhans, C.J., Schulz, G.W., Engelbrecht, J.S., Rousseau, F.J. 1992. The impact of a paper mill effluent spill on
the fish populations of the Elands and Crocodile Rivers (Inkomati System, Transvaal). Water SA 18, 73 – 80.
Kotze DC, Marneweck GC, Batchelor AL, Lindley DS and Collins NB, 2007. WET-EcoServices: A technique for
rapidly assessing ecosystem services supplied by wetlands. WRC Report No TT 339/08, Water Research
Commission, Pretoria.
Macfarlane, D.M., Walter, D., Koopman, V., Goodman, P., Ellery, W., Goge, C. 2007. WET-Health: a technique
for assessing wetland health. WRC Report No. TT340/08, Water Research Commission, Pretoria.
Mucina, L., Rutherford, M.C. (eds) 2006. The Vegetation of South Africa, Lesotho and Swaziland. Strelitzia 19.
South African National Biodiversity Institute, Pretoria.
O’Brien, G.C. 2003. An ecotoxicological investigation into the ecological integrity of a segment of the Elands
River, Mpumalanga, South Africa. MSc Thesis, Rand Afrikaans University, South Africa.
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O’Brien, G.C. 2012. Regional scale risk assessment methodology using the relative risk model as a
management tool for aquatic ecosystems in South Africa. PhD Thesis, Department of Zoology, University of
Johannesburg, South Africa.
O'Brien G, Wepener V. 2009. Ecological integrity assessment of the fish communities of the Thukela estuary,
KwaZulu-Natal, with comparisons from the Matigulu/Nyoni and Umvoti estuaries provided, Center for
Aquatic Research, Johannesburg
O'Brien G and Venter H. 2012. Evaluation of eight years (2005 to 2012) of ecological integrity data from the
lower Thukela River/Estuary and associated systems with management considerations based on the risk of
hazards affecting ecosystem structure and function, KwaZulu-Natal., Water Research Group, North West
University
O’Brien, G.C., Smit, N.J., Wepener, V. 2014. Conservation of fishes in the Elands River, Mpumalanga, South
Africa: Past, present and future. Koedoe 56. http://dx.doi.org/10.4102/koedoe.v56i1.1118
Roux, D. J. 2001. Development of procedures for the implementation of the National River Health
Programme in the province of Mpumalanga. Pretoria: Water Research Commission. Report No: 850/01/01.
Scott Shaw, C.R., Escott, B. (eds) 2011. KwaZulu-Natal Provincial pre-transformation Vegetation Map - 2011.
Unpublished GIS coverage [kznveg05v2_1_11_wll.zip], Biodiversity Conservation Planning Division, Ezemvelo
KZN Wildlife, P.O. Box 13053, Cascades, Pietermaritzburg, 3202.
Semlitsch, R.D., Bodie, J.R. 2002. Biological criteria for buffer zones around wetlands and riparian habitats for
amphibians and reptiles. Conservation Biology 17, 1219 – 1228.
Turpie, JK & Clark BM. 2007. The health status, conservation importance, and economic value of temperate
South African estuaries and development of a regional conservation plan. Report to Cape Nature by Anchor
Environmental Consultants. Report No. AEC2007/05.
Turpie, J.K., Wilson, G. & Van Niekerk, L. 2012. National Biodiversity Assessment 2011: National Estuary
Biodiversity Plan for South Africa. Anchor Environmental Consultants Report No AEC2012/01, Cape Town.
Report produced for the Council for Scientific and Industrial Research and the South African National
Biodiversity Institute.
Van Niekerk, L. and Turpie, J.K. (eds) 2012. South African National Biodiversity Assessment 2011: Technical
Report. Volume 3: Estuary Component. Pretoria: South African National Biodiversity Institute. CSIR Report
CSIR/NRE/ECOS/ER/2011/0045/B. Stellenbosch: Council for Scientific and Industrial Research.
Weddepohl, J.P., du Plessis, H.M., Harris, J., Chutter, F.M. 1991. Sappi Ngodwana Mill water quality in the
Elands River. Pretoria. Division of Environment and Forestry Technology, CSIR.
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10. APPENDICES
10.1. Appendix A – Minutes from the first WRC development
workshop
WATER RESEARCH COMMISSION
K5/2200
MINUTES OF THE SECOND STAKEHOLDER WORKSHOP CONDUCTED ON THE 26TH OF MARCH 2013
AT THE PULA COMMITTEE ROOM, WRC, MARUMATI BUILDING, 18TH AVENUE, CORNER FREDERIKA
STREET, RIETFONTEIN, PRETORIA
___________________________________________________________________
PRESENT:
Mr BM Madikizela (Chairperson)
Ms N Fourie
Dr C Kleynhans
:
Ms C Thirion
Dr H Malan
Mr I Bredin (Act Scriber)
:
Dr C Dickens
Mr D Macfarlane
Mr H Marais
Mr U Bahadur
Mr D Kleyn
:
Water Research Commission
:
Department of Water Affairs
Department of Water Affairs
:
Department of Water Affairs
:
Freshwater Research Council
Institute of Natural Resources
:
Institute of Natural Resources
:
Eco-Pulse Environmental Consulting Services
:
Mpumalanga Tourism and Parks Agency
:
South African National Biodiversity Institute
:
Department of Agriculture, Forestry and Fisheries
APOLOGIES:
Mr G Marneweck
Mr A Maherry
Mr D Impson
Mr K Hamman
Mr R Parsons
STAKEHOLDER WORKSHOP
1. WELCOME AND INTRODUCTION
 Mr Bredin welcomed everyone to the workshop and introduced the project team, including
the team members who were not present (i.e. Prof. Guy Bate and Prof. Janine Adams).
 Mr Bredin acknowledged the work that has been completed to date, by Mr Macfarlane and
the original project team.
 All participants introduced themselves.
2. PRESENTATION BY THE TEAM
2.1. Summary of work completed to date (refer to the attached copy of the presentation):
 Mr Bredin presented a brief summary of the work that has been completed to date.
2.2. Overview of the approach taken and step-wise process (refer to the attached copy of the
presentation):
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Mr Bredin presented an overview of the approach taken to determining the requirements of
buffer zones, and the proposed step-wise process for determining buffer zones.
Mr Kleyn questioned how sensitivity was determined, in particular were criteria such as soil
type and slope considered. Mr Bredin confirmed that these criteria were taken into
consideration. Mr Macfarlane further highlighted that the criteria used to determine
sensitivity will be identified when he presents the draft model.
2.3. Draft buffer zone model:
 Mr Macfarlane presented the draft model for determining appropriate buffer zones and
used hypothetical examples to explain how the model works. He noted at the start of the
presentation that the criteria used in the model are still in a draft form and therefore there is
an opportunity for the workshop participants to contribute to the refining on the model.
 Mr Macfarlane used an example of a desktop assessment to explain the basic principles of
the model.
 Dr Malan questioned whether guidelines for defining different types of developments will be
provided. Mr Macfarlane confirm that there are already draft guidelines provided in an
annexure to the model that identifies different subsectors of a wide range of developments
according to available definitions.
 Dr Malan questioned whether the size of a development is taken into consideration when
determining a buffer zone. Mr Macfarlane indicated that the average impact of
developments is used to flag areas of concern and where there is a high risk then the size of
the development would be considered at a site level.
 Mr Madikizela questioned whether aspects such as soil, the landscape and the flow of water
within a catchment are taken into consideration for determining a buffer zone, as there is a
concern about how buffer zones will address impacts occurring in the catchment. Mr
Macfarlane explained that the model is designed to flag areas of concern. He used a forestry
example, where the reduction of volumes of flow is a major risk, to illustrate the difference
in risk to different types of wetlands within different catchments. The model allows for the
risk to be identified. Mr Macfarlane emphasized that alternative mitigating measures, other
than buffer zones, would also need to be taken into consideration to address impacts
occurring in the catchments of wetlands.
 Mr Bahadur questioned whether exceptions, such as the protection of Grass Owl habitat,
have been factored into the model. Mr Macfarlane explained how difficult it is to factor in
aspects such as these. However, the model does allow for consideration of such aspects (i.e.
at a site level).
 Mr Madikizela highlighted that the buffer zone method and model developed can be
scientifically defended, i.e. through peer review, etc., however, has the enforcement of the
buffer zone requirements been taken into consideration. Mr Macfarlane explained that it is
important to remember that buffer zones are only one type of mitigating measure.
Appropriate alternative mitigating measures at different stages of a development may
provide more effective mitigation, which would then allow for the buffer zone to be reduced
in size and still be effective (An example of a housing development was used). Mr
Macfarlane stressed that the development of buffer zones should be viewed as a guideline
as there may well be other more effective mitigating measures that need to be considered.
Ms Fourie confirmed that while there are current standard buffer zones recommended, the
Department of Water Affairs (DWA) would also advocate the enforcement of justifiable site
specific requirements (i.e. establish what the risks are and identify what the buffer zone
should be according to the risks). Mr Macfarlane reiterated that the model is tailored for
identifying such requirements.
 Dr Kleynhans questioned whether Ecological Water Requirements (EWR) have been taken
into consideration. After a brief discussion Mr Macfarlane indicated that EWR are something
that the team still needs to give consideration to and asked that Mr Bredin make a note of
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this requirement.
Mr Kleyn questioned whether old cultivated agricultural lands would be considered under
the construction or operational phase of the model. Mr Macfarlane indicated that generally
in terms of agricultural land, land clearing is viewed as the construction phase and the
planting and harvesting of crops is viewed as the operational phase. This may not always be
the case and therefore the model does allow for site specific conditions.
Mr Kleyn questioned whether the model addresses impacts occurring within the wetland
(i.e. a floodplain that is regularly ploughed for the planting of crops). Mr Macfarlane
explained that the buffer zones focus on addressing impacts occurring adjacent to the edge
of the wetland and not in the wetland.
Mr Marais raised a concern about the generalization of larger wetlands being viewed as
more important than smaller wetlands. Mr Macfarlane explained that at this level the main
focus was on processes and not on specific aspects such as biodiversity. Dr Dickens reminded
participants that we were discussing the desktop assessment and that important aspects
such as biodiversity have been factored into the model at a site specific level.
Dr Kleynhans cautioned against the use of the desktop assessment as it may lead to misuse.
Mr Macfarlane indicated that we need to be clear on what the desktop assessment can be
used for and that perhaps it would be worth reviewing this section to ensure that we clearly
indicate the limitations. Dr Dickens gave an example of how desktop assessments have been
misused. Mr Bredin indicated that the team is considering indicating a range for a desktop
assessment instead of specific size.
Dr Malan questioned whether the desktop assessment is going to be a more conservative
assessment. Mr Macfarlane indicated that this is where the range approach may be more
effective, i.e. the range being based on the worst case and best case scenarios. Dr Dickens
cautioned on the use of this approach and indicated that we would need to provide clear
justification for the recommended range.
Mr Marais highlighted that the desktop assessment can only be based on available data,
which is often limiting. In addition, he also raised a concern that desktop assessments are
often viewed as the end result and not as the initial assessment, which only provides a broad
perspective. Mr Macfarlane referred to discussions held with the steering committee at the
start of the project, where it was agreed that a method that could be applied at different
levels should be developed. He went on to emphasize that the testing will hopefully confirm
the effectiveness and limitations of the assessments at the different levels.
Dr Malan queried who we envisage will use the method developed. Mr Macfarlane suggests
that the primary users would be specialists undertaking assessments for EIAs. Mr Kleyn
indicated that he would also like to see it being used in the agricultural sector to ensure that
agricultural activities are kept out of sensitive areas. He also suggested that it could
potentially be applied to determine compensation for farmers who have lost crops due to
natural disasters, such as flooding (i.e. a reduced / no compensation for the loss of crops
within a demarcated buffer zone). Mr Bahadur suggested that the method could also be
useful for early warning systems.
Ms Thirion enquired as to what the desktop assessment would be used for. Mr Macfarlane
gave an example of using the desktop assessment to provide broad information for an
Environmental Management Framework (EMF) or alternatively a land use management plan.
Dr Kleynhans queried the applicability of General Authorizations (GA) for wetlands. Ms
Fourie indicated that a GA applies to all activities that are located further than 500m from a
wetland. She further stressed that the DWA concern is the hydrology in the catchment of the
water resource. However, she felt that consideration could be given to applying GA to low
risk developments that meet the determined buffer requirements.
Ms Fourie requested that where the desktop assessment doesn’t address certain criteria,
such as hydrology, that this be clearly indicated. Mr Macfarlane explained that while some
criteria are not addressed at a desktop level the model does allow for the flagging of such
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
issues, as each criteria identified will have a risk class assigned to it.
Mr Macfarlane then referred to an example of a detailed assessment to highlight the criteria
that need to be taken into consideration.
Dr Kleynhans commented that at a detailed level the wetland would need to be assessed in
terms of the different units or compartments. Mr Macfarlane confirmed that this level of
assessment would be required for the detailed assessment.
Dr Dickens queried whether this approach to the detailed assessment addresses to some
extent the EWR. Dr Kleynhans indicated that it does starts to create links between critical
components, which is important for determining the EWR.
Mr Kleyn enquired as to whether there would be a key to help the user determine which
class each of the site-based modifier aspects would fall into (e.g. a key to determine which
slope class would be applicable). Mr Macfarlane confirmed that a guideline will be provided
to assist the user in determining the appropriate classes.
Dr Malan queried whether the same criteria for determining slope for Wet Health would be
used. Mr Macfarlane indicated that the focus will be on the slope of the buffer zone and not
the wetland so the same criteria may not apply. In general the approach would be to use
1:50 000 topography maps (i.e. 20m contours) to determine the slope of the buffer zone.
Mr Madikizela queried whether the model takes into account the type and density of
vegetation in the proposed buffer zone. Mr Macfarlane agreed that vegetation, both species
composition and density, have a big impact on the functioning of the buffer zone. This is
where the management of the buffer zone becomes important, e.g. the effect of clearing
alien vegetation from a buffer zone, as part of the management objectives, would need to be
taken into consideration as this will affect the functionality of the buffer zone. The
management of buffer zones still needs to be addressed.
Dr Malan raised a concern about cumulative impacts and whether these are taken into
consideration. Mr Macfarlane indicated that a conservative approach has been taken to
address cumulative impacts, in that in general the status quo would be required to be
maintained. However, this will all depend on the accuracy of the risks determined. Assuming
the risks are accurate, it would also be important that the mitigation measures identified are
undertaken correctly.
Mr Marais commented on the need to consider the wide range of activities that occur in a
catchment and the impact of these activities. Mr Macfarlane acknowledged that there are
many activities that have an impact and in most instances buffer zones will not be able to
address these impacts. It is important to note that a buffer zone is only one type of
mitigating measure and other more applicable mitigating measures would need to be
considered for individual sites. It was also noted that the team advocates that no decisions
will be able to be made based on a desktop assessment, i.e. site based assessments will need
to be undertaken to allow for decisions to be made.
Mr Macfarlane discussed the concept of developing species information sheets to provide
the relevant biodiversity information to help determine the appropriate buffer zone.
Mr Marais cautioned that some land users try to advocate plans that are unrealistic, in order
to try and reduce the buffer zone requirements. Mr Macfarlane and Ms Fourie commented
that all parties involved, i.e. the specialists, the Environmental Assessment Practitioner (EAP),
the authorities, etc., have a responsibility to ensure they are satisfied with the
recommendations made.
Mr Bahadur queried the approach taken and whether or not it is a conservative approach.
Mr Macfarlane explained that a scientific defendable approach has been taken, where the
primary drivers are the relationships of the criteria and the levels of risk determined.
Therefore a conservative approach hasn’t been taken but rather an approach based on best
available science, which can be defended.
Mr Macfarlane discussed other mitigating measures, other than buffer zones, that need to
be taken into consideration. It was noted that it is important to consider other options. A
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draft spreadsheet of guidelines for alternative mitigating measures has been developed. It
was noted that it is important that where other mitigating measures are required that they
become as much of the requirements of the license as the buffer zone requirements would
be.
Mr Macfarlane raised a concern about how effective other mitigating measures are at
addressing impacts. The effectiveness of the mitigating measures has not been assessed in
detail in the project, unlike with the assessment of the effectiveness of buffer zones. It was
also noted that a concern regarding buffer zones is how certain can one be that the buffer
zone will be properly managed / maintained.
Mr Bredin queried whether all the detail for each of the mitigating measure will be written
into the authorization for the development. Ms Fourie confirmed that this information would
need to be included in the requirements for the authorization of a development (i.e. legally
binding).
Dr Malan commented that some of the mitigating measures will require maintenance. Mr
Macfarlane agreed and also indicated that a buffer zone would also need to be maintained.
Dr Malan highlighted that where there is a difference is when a smaller buffer is not
maintained it will be lost and there will likely be no other options. However, a larger buffer
that has not been maintained correctly may still recover its functionality through applying
alternative options.
Mr Macfarlane highlighted EThekwini’s concern about climate change and how it could
affect the current flood line estimates. He emphasized that there may be many other
concerns like the one raised by EThekwini, however, the buffer zone methodology cannot
address all of these aspects.
Mr Bredin suggested that a more conservative approach could be taken when considering
alternative mitigating measures. Mr Macfarlane cautioned against this because there could
be cases where the other mitigating measures are very effective. Dr Malan highlighted that it
should be remembered that there are other roles that buffer zones play and therefore a
conservative approach may be a safer option. Dr Dickens gave an example of how a
conservative factor is used in setting limits for water quality levels. Mr Macfarlane agreed
that it would be worth considering building in a conservative factor for other mitigating
measures (i.e. build in a limit to reduce the risk).
Dr Dickens suggested that the ‘time factor’ needs to be taken into consideration for
determining the effectiveness of the buffer zone and other mitigating measures to address
the relevant impacts (e.g. sedimentation in a river could be a long term or short term
impact). Mr Macfarlane indicated that the way we have tried to address the time factor is
through the sensitivity component of the model.
Ms Fourie raised a concern about the need to address hydrology in more detail, which was
noted as additional to the main focus of the project. Ms Fourie indicated that there is a need
to address hydrology issues through other mitigating measures, such as storm water
management plans. Mr Macfarlane highlighted that the model does flag areas, which can be
used to identify other mitigating measure that could be used to address hydrology concerns.
It was also noted that developing mitigating measures to address hydrology issues
specifically would largely be outside the scope of work for the project. Mr Bredin agreed. Dr
Dickens shared some of Ms Fourie’s concerns, in that clarification must be provided for the
role and limitation of buffer zones. Mr Madikizela highlighted that there are other tools and
process that need to be taken into consideration to address the issues of activities upstream
in the catchment, i.e. the buffer zones are only one of the tools available to mitigate impacts
on water resources. Ms Fourie emphasized that having a set buffer zone requirement for
areas further upstream in the catchment helps to address the impacts, e.g. addressing
forestry plantations in the catchment of the water resource. Dr Kleynhans emphasized that it
is a question of scale that needs to be taken into consideration, which Ms Fourie and Mr
Macfarlane agreed with.
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Mr Bredin referred to discussions with Prof Guy Bate where he emphasized that for estuaries
a buffer zone will only be able to mitigate lateral impacts. Impacts for upstream activities will
not be addressed through placing a buffer zone around an estuary.
Mr Kleyn queried whether soil type will be used. Mr Macfarlane indicated that the focus will
be on soil permeability or perhaps soil texture, which have been identified as more
important characteristics for determining buffer zones. Mr Marais suggested that where soils
data is available it could be useful. Mr Macfarlane indicated that a method needed to be
developed that could be applied whether the information was available or not.
Mr Madikizela had a final query with regards to the use of the buffers tool within urban
areas and for rehabilitated wetlands. Mr Macfarlane indicated that the buffer tool could be
used retrospectively, therefore it could be applied to such circumstances.
2.4. Overview of remaining deliverables and the proposed field testing (refer to the attached
copy of the presentation):
 Mr Bredin presented an overview of the remaining deliverables and the proposed approach
to field testing.
 Mr Madikizela queried whether a test site or sites have been identified, which will address
the relevant requirements. Mr Bredin indicated that the project team is considering the
Umvoti system as a possible test site, which should provide a range of aspects required to
test the methods repeatability and consistency. It was also noted that the estuarine
component may need to be tested in the Eastern Cape because that is where Prof Janine
Adams is based.
 Mr Madikizela indicated that the City of Johannesburg and the City of Cape Town, as well as
the EThekwini municipality, are interested in the project and should be contact to see if
there are any partnership opportunities (i.e. to further test the method). Dr Malan indicated
that Candice Haskins is chairing the Western Cape wetland forum, which has always had an
interest in this project, and we should contact her with regards to buffer guidelines /
legislation that have already been developed for the City of Cape Town.
 Ms Fourie enquired about stakeholder consultation. Mr Macfarlane indicated that there was
a lot of talk around this issue before the project was put on hold. While there is value in
undertaking the consultation there are budgetary and time constraints. Mr Bredin agreed
with the value of stakeholder consultation but suggested that the initial focus needs to be on
the scientist so that the method can be tested. Mr Madikizela indicated that the steering
committee would need to decide on an appropriate action to take.
…………………………………..
CHAIRPERSON
…………………………………….
COMMITTEE SECRETARY
……………………………………
DATE
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WATER RESEARCH COMMISSION
Water Linked Ecosystems
ATTENDANCE REGISTER
Project No
Date of workshop &
meeting
K5/2200
PULA COMMITTEE ROOM, WRC, MARUMATI BUILDING, 18
RIETFONTEIN, PRETORIA
Venue
Surname & Initials
Company
TH
26 March 2013
AVENUE, CORNER FREDERIKA STREET,
Chairman
Member / Project
Team / Stakeholder
Tel Number
Mr Madikizela
Fax Number
E-mail address
Madikizela B.
WRC
SC Member
012 330 0340
012 331 2565
bonanim@wrc.org.za
Fourie N.
DWA
SC Member
082 881 7321
012 336 6836
fourien@dwa.gov.za
Kleynhans C.J.
DWA
SC Member
082 800 4841
kleynhansn@dwa.gov.za
Thirion C.
DWA
SC Member
082 808 9846
thirionc@dwa.gov.za
Kleyn D.H.
DAFF
SC Member
082 789 6915
Malan H.
FRC
SC Member
082 411 7375
Bredin I.P.
INR
Project Team
082 442 1424
033 346 0895
ibredin@inr.org.za
Dickens C.
INR
Project Team
083 269 6207
033 346 0895
cdickens@inr.org.za
Macfarlane D.
Eco-Pulse Consulting Services
Project Team
084 368 4527
033 346 0895
dmacfarlane@eco-pulse.co.za
Marais H.
MTPA
Stakeholder
082 774 3303
hanneswetlands@gmail.com
Bahadur U.
SANBI
SC Member
079 497 3229
u.bahadur@sanbi.org.za
122
012 329 5938
davidk@nda.agric.za
heather.malan@gmail.com
For
office
use
Cap
Deliverable 11: Practical Testing / Field Testing Report
10.2. Appendix B – Minutes from the second WRC development
workshop
WATER RESEARCH COMMISSION
K5/2200
MINUTES OF THE STAKEHOLDER WORKSHOP CONDUCTED ON THE 17TH OF SETEMBER 2013 AT THE
PULA COMMITTEE ROOM, WRC, MARUMATI BUILDING, 18TH AVENUE, CORNER FREDERIKA
STREET, RIETFONTEIN, PRETORIA
PRESENT:
Mr BM Madikizela (Chairperson)
Mr P Fairall
Mr D Macfarlane
Mr I Bredin
Mr M Zungu
Mr S Mitchell
Ms N Newman
Mr U Bahadur
Mr D Kleyn
Ms N Fourie
Dr W Roets
Mr GC Marneweck
Ms J Gouws
Ms F Mbedzi
Mr M Boon
Ms J Eagle
Mr V Ndlopfu
: Water Research Commission
: Emifula Consulting Services
: Eco-Pulse Consulting Services
: Institute for Natural Resources (INR)
: Institute for Natural Resources (Student)
: EON Consulting
: City of Cape Town
: South African National Biodiversity Institute
: Department of Agriculture, Forestry & Fisheries
: Department of Water Affairs
: Department of Water Affairs
: Wetland Consulting Services
: Cape Nature
: Department of Water Affairs
: Lidwala EPS
: City of Johannesburg
: GDARD
APOLOGIES:
Dr C Dickens
Dr H Malan
Ms C Thirion
Mr M Rountree
Dr CJ Kleynhans
Ms N Thwala
Prof K Rogers
Mr W Sinclair
STAKEHOLDER WORKSHOP
1. WELCOME AND INTRODUCTION


Mr Bredin welcomed everyone to the workshop and introduced the project as well as
the project team.
All participants introduced themselves indicating the organizations they were
representing.
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Deliverable 11: Practical Testing / Field Testing Report
2. PRESENTATION BY THE TEAM
2.1. Summary of work completed to date, including an overview of the approach taken and
step-wise process
 Mr Bredin delivered a short presentation on the project, first providing background to the
project and then presenting a summary of the work that has been completed to date (Refer
to Appendix A for a copy of the presentation).
 Mr MacFarlane facilitated a discussion on criteria that should be considered when
determining wetland buffer zones. The discussion provided an opportunity for participants
to consider the extent of criteria that need to be considered. Responses included:
o Dr Roets emphasized the need to consider flow regimes and physical, chemical and
geomorphological characteristics of wetlands when designing buffer zones. He also
proposed that the determination of buffer zones should follow a risk-based
approach.
o Mr Marneweck agreed with the need to consider flow regimes. Any decision-making
must prioritize the maintenance of flows as these determine the condition and
functionality of wetlands. Mr Marneweck further stressed that the geohydrological
characteristics of wetlands need to be considered when delineating buffer zone
widths, as these characteristics are important for protecting groundwater from the
proposed activity. Furthermore, he also suggested that the precautionary principle
should be applied to determine buffer zones.
o Ms Newman suggested that before designing buffer zones, it is important to first
consider the type of wetland habitat as this is important in determining what types
of species occur there and what measures need to be considered to conserve them.
Secondly it is also important to consider the condition of the wetland (i.e. Present
Ecological State (PES)).
o Ms Eagle stressed the importance of considering the proposed/planned landuse in
the decision-making process. This is because different landuse types will affect
wetlands differently in terms of sediment flows, runoff, chemical composition of
water, etc. Thus the threat of the proposed landuse is a key criterion that needs to
be considered.
o Mr Ndlopfu supported Ms Eagle’s comments and suggested that depending on the
buffer requirements, the recommended buffer zones should go beyond current
wetland buffer guideline widths, providing sufficient justification is provided.
o Mr Madikizela highlighted the importance of using the buffer models in delineating
buffer zones to address issues such as flood risk, climate risk, etc. He paid special
emphasis to climate change risk as currently climate change is of great concern
globally.
o Mr Bahadur cautioned that policy should always guide the determination of buffer
zones.
o Mr Madikizela agreed with Mr Bahadur and stated that the Water Research
Commission (WRC) will review policies associated with buffer zone development to
make them more efficient at delivering the required outcomes.
o Mr Marneweck stressed the importance of considering soil characteristics when
determining buffer zones.
o Ms Eagle suggested that site characteristics (e.g. slope, vegetation, soils, etc.) play
an important role in determine a buffer zone. She also cautioned that the
management of a buffer zone is equally important.
 Mr MacFarlane thanked the participants for providing feedback on what criteria they felt
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Deliverable 11: Practical Testing / Field Testing Report

needed to be considered for determining buffer zones. It was agreed that there are a wide
range of criteria that need to be considered, which makes it challenging to develop a
method for determining buffer zones. Mr MacFarlane indicated that the majority of the
criteria recommended will be addressed when he goes through the draft model.
Mr Madikizela requested that a copy of Deliverable 8 and the draft models developed be
distributed to the participants.
Action: Project Team
2.2 Presentation of a wetland case study
 Mr Bredin presented a wetland case study, which would be used to describe how the
wetland buffer model works (Refer to Appendix A for a copy of the presentation).
2.3 Draft buffer zone model
 Mr MacFarlane went through a step-by-step process, explaining the model and how the
model was derived. In summary he indicated that the model has been designed to allow for
a desktop assessment and a more detailed site-based assessment. The desktop assessment
option considers the worst case scenario in terms of the threat of the proposed landuse and
can only be used as a guideline for planning (i.e. no decisions should be taken from the
results of a desktop assessment). The site based assessment considers the threats of the
proposed development / landuse, the sensitivity of the wetland, the site based
characteristics of the buffer zone, biodiversity, and additional mitigating measures. The sitebased assessment takes into account a wide range of criteria, which will make it a robust
method for determining buffer zones (this still needs to be proven during the testing phase).
 Feedback on the proposed buffer model included:
o It was acknowledged by all that the model considers a wide range of criteria, which
are important for determining buffer zones. While not all criteria are considered, it
was agreed that the focus should be on producing a method / model that would
allow for the guidance of management decisions, which is based on the assessment
of the majority of key criteria.
o Mr Marneweck suggested that the inclusion of soil data should still be considered.
He suggested that the ARC land type classification of soils could be considered. Mr
MacFarlane indicated that it would be important to consider the surrounding soils.
However, he acknowledged that it would be difficult to incorporate this information
into the existing model.
o It was suggested that turbidity could be included, as this determines the sensitivity
of wetlands to sediment impacts. Other criteria that may be worth investigating
included: extent of open water; sensitivity to vegetation on being submerged; and
vulnerability to erosion.
o It was suggested that the model should be customized based on site characteristics
such as aspect, slope, etc. Mr MacFarlane indicated that the model does take into
account site based characteristics for the proposed buffer zone.
o Mr Bredin highlighted that buffers are not the only option in mitigating landuse
impacts on wetlands. He indicated that the model provides an opportunity for the
user to consider alternative mitigating measures, which may be more effective at
mitigating a specific impact from a land use activity. Thus, a reduced buffer zone
could be considered in conjunction with the alternative mitigating measures.
o It was suggested by all that the model should try to find a link between geographic
constraints and buffer management. Furthermore, it was stressed that the
parameters used should be specific for a specific management objective.
o It was suggested that limitations of the model should be clearly stated to prevent
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Deliverable 11: Practical Testing / Field Testing Report


misinterpretation or misuse.
o It was suggested that the model should only be used by qualified persons, who have
attended training on how to use the model.
o It was suggested that a matrix of wetland tools should be considered, however, it
was agreed that this was not part of the project’s scope of work.
o The use of either the macro channel or the active channel in determining the buffer
zone width for rivers needs to be clarified.
Action: Project Team
o It was highlighted that the model should consider important catchment aspects
(especially flow), as understanding of the catchment itself (i.e. drivers) is paramount
for guiding management decisions. It was also suggested that the risks posed by
different land-uses should only be considered once the understanding of drivers has
been attained. Mr MacFarlane indicated that certain drivers are taken into
consideration in the model.
o Mr Marneweck suggested that the use of indicator species should be considered.
o Mr Marneweck stressed that it was critical that it be made clear that buffer zones
are not appropriate for open cast mining and that this should be clearly stated in the
model. Mr Bredin agreed.
The findings from applying the model to the case study resulted in a discussion of
appropriate minimum buffer zones. Ms Eagle emphasized that based on the fact that many
small municipalities lack qualified personnel who could make sound recommendations
regarding the application of the models outputs, minimum buffer zones should be ‘capped’.
It was emphasized that to prevent misapplication, the model output should set an
appropriate minimum buffer distance. Mr Bredin agreed, and indicated that a distance of
15m has been proposed and will be investigated as part of the testing phase.
Action: Project Team
Mr MacFarlane briefly presented the tool developed to aid in the selection of appropriate
alternative mitigating measures. Ms Eagle indicated that while the tool is useful it must align
with current mitigating measures recommended in other guidelines / policies being applied
at a municipal and provincial level.
…………………………………..
CHAIRPERSON
…………………………………….
COMMITTEE SECRETARY
……………………………………
DATE
126
Deliverable 11: Practical Testing / Field Testing Report
WATER RESEARCH COMMISSION
Water Linked Ecosystems
ATTENDANCE REGISTER
Date of workshop
& meeting
17 September
2013
Project No
K5/2200
Venue
PULA COMMITTEE ROOM, WRC, MARUMATI BUILDING, 18 AVENUE, CORNER FREDERIKA
STREET, RIETFONTEIN, PRETORIA
TH
Surname & Initials
Company
Member / Project Team /
Stakeholder
Tel Number
Fax Number
Mr Madikizela
E-mail address
For office use
Cap
Madikizela B.
Fourie N.
Newman N.
Zungu M.
WRC
DWA
City of Cape Town
INR
SC Member
SC Member
SC Member
Project Team
012 330 0340
082 881 7321
072 4959715
073 979 3489
Kleyn D.H.
Roets W.
Bredin I.P.
Macfarlane D.
Mitchell S.
Marneweck G.C.
Mbedzi F.
Ndlopfu V.
Fairall P.
Eagle J.
Boon M.
Gouws J.
Bahadur U.
DAFF
DWA
INR
Eco-Pulse Consulting Services
EON Consulting
Wetland Consulting Services
DWA
GDARD
Emifula Consulting
City of Johannesburg
Lidwala EPS
Cape Nature
SANBI
SC Member
SC Member
Project Team
Project Team
SC Member
SC Member
SC Member
Stakeholder
Stakeholder
SC Member
Stakeholder
SC Member
SC Member
082 789 6915
012 336 6910
082 442 1424
084 368 4527
082 795 1465
012 349 2699
012 808 9509
071 440 5703
012 993 0969
082 414 2431
074 761 2327
079 497 3229
127
Chairman
012 331 2565
012 336 6836
086 614 7806
033 346 0895
012 349 2993
012 808 0338
021 866 8000
012 843 5200
bonanim@wrc.org.za
fourien@dwa.gov.za
natalie.newman@capetown.gov.za
zungumm@gmail.com
davidk@nda.agric.za
roetsw@dwa.gov.za
ibredin@inr.org.za
dmacfarlane@eco-pulse.co.za
steve.mitchell@eon.co.za
garym@wetcs.co.za
mbedzif@dwa.gov.za
Vukosi.ndlopfu@gaunteng.gov.za
emifula@telkomsa.net
janee@joburg.org.za
mboon@lidwala.com
jgouws@capenature.co.za
u.bahadur@sanbi.org.za
Deliverable 11: Practical Testing / Field Testing Report
10.3. Appendix C – Attendance register for the SASAQS workshop
SASAQS WORKSHOP
ATTENDANCE REGISTER 03 JULY 2013
NAME
Mandla Dlamini
Brigitte Melly
Denise Scheal
Alexis Olds
Mathew Bird
Justine Ewart-Smith
Gerhard Diederides
Donovan Kotze
Samantha Adey
Dimitri Veldkornet
Janine Adams
Peter Ramollo
Daniel Lemley
Meredith Cowie
Luirenne Human
Phumelele Gama
Gavin Snow
Theile Mohlala
Warren Aken
Santosh Bachoo
Namhla Mbona
Graham Jewitt
Pierre de Villiers
Bruce Paxton
Kelly Rautenbach
Liaan Pretorius
Dean Ollis
Nancy Job
H Malan
B Grant
B Bester
Prof Guy Bate
Candice Haskins
Natalie Newman
Siyabonga Buthelezi
ORGANISATION
NMMU
NMMU
NMMU
Cape Nature
NMMU
Freshwater Research Centre
Environmental Biomonitoring Services
UKZN/MWP
Consultant
NMMU
NMMU
DENC
NMMU
NMMU
NMMU
NMMU
NMMU
WRC
Golder
KZN WILDLIFE
SAMBI
UKZN
Cape Nature
Freshwater Research Centre
NMMU
NMMU
FCG
Independent
FRC
SEF
SEF
NMMU
City of Cape Town
City of Cape Town
DWA-EC
128
EMAIL
cmindlo89@gmail.com
brigittemelly@gmail.com
denise.schael@nmmu.ac.za
aolds@capenature.co.za
mattsbird@gmail.com
justine@worldonline.co.za
gerhardd@mweb.co.za
kotzed@ukzn.ac.za
Samantha.Adey@gmail.com
dimitri.veldkornet@nmmu.ac.za
janine.adams@nmmu.ac.za
ramollopp@gmail.com
daniel.lemley@nmmu.ac.za
meredith.cowie@nmmu.ac.za
s203025105@live.nmmu.ac.za
phumelele.gama@nmmu.ac.za
gavin.snow@nmmu.ac.za
thellem@wrc.org.za
waken@golder.co.za
bachoos@kznwildlife.com
n.mbona@sanbi.org.za
jewittg@ukzn.ac.za
estuaries@capenature.co.za
bruce.r.paxton@gmail.com
kelly.rautenbach@nmmu.ac.za
liaan_p@yahoo.com
dean.ollis@gmail.com
nancymjob@gmail.com
heatherlmalan@gmail.com
byron@sefsa.co.za
byronb@sefsa.co.za
guy.bate@nmmu.ac.za
candice.haskins@capetown.gov.za
natalie.newman@capetown.gov.za
ButheleziS2@dwa.gov.za
Deliverable 11: Practical Testing / Field Testing Report
10.4.
Appendix D – Attendance register for the NWI workshop
ATTENDANCE REGISTER
Development workshop for the WRC Buffer Project (K5/2200) – National Wetland Indaba 2013
rd
Date: 23 of 0ctober 2013
First Name
Surname
Organisation
Tel Number
Cell phone
E-mail address
Ian
Bredin
INR
033 346 0796
082 442 1424
ibredin@inr.org.za
Doug
Macfarlane
Eco-Pulse
084 368 4527
dmacfarlane@eco-pulse.co.za
Support
Chavalala
City of JHB
011 587 4268
083 575 8722
Supportc@joburg.org.za
Pule
Makena
City of JHB
011 587 4266
076 335 1196
Pulema@joburg.org.za
Freddie
Letsoko
City of JHB
011 587 4274
083251 2598
FreddieL@joburg.org.za
Lize
Shaw
Mondi
035 902 2973
082 527 1845
lize.shaw@mondigroup.co.za
Bokang
Ntloko
Letseng Diamonds
0026663071081
0026663071081
Ntlokb@gmail.com
Brad
Graves
Groundtruth
033 343 2229
brad@groundtruth.co.za
Fiona
Eggers
Groundtruth
033 343 2229
Fiona@groundtruth.co.za
Noluthando
Bam
EC- DEDEAT
043 605 7069
082 332 6722
noluthando.bam@dedea.gov.za
Hennie
Swamevelder
EC-DEDEAT
042 292 0339
083 406 3159
hennie.swanevelder@dedea.gov.za
Nancy
Job
Private
Valerie
Rilian (Du plessis)
DWA
012 336 8679
082 809 2155
duplessisv@dwa.gov.za
Paul
Meulenbeld
DWA
012 336 7663
082 662 7719
meulenbeldp@dwa.gov.za
Shaun
Westraadt
West Projects
073 556 7260
s.westraadt@gmail.com
Janet
Ebersother
Eco-Route
082 557 7128
janet@ecoroute.co.za
nancymjob@gmail.com
044 381 0515
129
Deliverable 11: Practical Testing / Field Testing Report
First Name
Yolande
Surname
Vermaak
Wietsche
Roets
Kathy
Organisation
GIB-wfwetlands wfwater
Tel Number
042 283 0329
Cell phone
072 877 1033
E-mail address
yolande.v@gamtooswater.co.za
DWA
012 336 6570
082 604 7730
roetsw@dwa.gov.za
Taggart
Natural Scientific Services
011 7877 400
082 448 1923
Kathy@nss-sa.co.za
Jan
Huyser
Komatiland forests
013 754 2729
083 627 8607
jhuyser@klf.co.za
Chris
Foster
Komatiland forests
083 677 0839
083 677 0839
cfoster@klf.co.za
Steve
Haiely
Environmental Services
083 631 8633
013 7511 693
?
Bertus
Fourie
Galag environmental
082 921 5445
Zukiswa
Ngxowa
DAFF:LUSM
043 704 6800/9
084 051 3128
ZukiswaN@daff.gov.za
Coryl
Logie
St Francies Links
042 294 0588
083 529 5410
b.logie@telkomsa.net
Bekky
Mashego
Komatiland Forests
013 754 2700
083 677 0921
bekky@klf.co.za
Heather
Malan
Freshwater Res Centre
083 411 7375
heatherLMalan@gmail.com
Lulu
Pretorius
UFS
0795066702
pretorius.lulu@gmail.com
Gary
Rudzani
Taylor
Nemukula
Ekurhuleni Metro
Municipality
WESSA
083 744 1939
071 155 2316
gjtaylor@ekurhuleni.gov.za
rnemukula@wessanorth.co.za
Bisuairk
Mashau
GDARD
011 240 2500
083596 9821
Mpfareleni.mashau@gauteng.gov.za
Anger
Phaliso
Mabodo cc
011 900 7703
082 389 2409
mashudua@mweb.co.za
Collin
Silima
SANBI
015 516 2072
071 686 1975
cinemadodzi@sanbi.org.za
Eric
Qonya
Env Affairs
043 707 4108
083762 2723
eric.qonya@deaet.ecape.gov.za
Mamasangane
Ncubuka
SANBI
012 843 5225
0725079685
M.Ncubuka@sanbi.org.za
Goolam
Tambe
Cape Nature
012 955 5940
0837860027
gtambe@capenature.co.za
Gail
Andrews
Rand Water
Godfrey
Lambani
Rand Water
?
gandrews@randwater.co.za
0116820148
130
0732819220
glambani@randwater.co.za
Deliverable 11: Practical Testing / Field Testing Report
First Name
Zungu
Surname
Mene
Organisation
DEDEAT
Tel Number
0415085804
Cell phone
E-mail address
zungu.mene@deaet.ecape.gov.za
Nosinodi
Ntola
DEDEAT
0475311191
0763707969
nosinodi.ntola@deaet.ecape.gov.za
Laura
Danga
Primeafrica
0123480317
0747982221
L.danga@primeafrica.net
Martin
Ferreira
Jeffares & Green
011 807 0660
0833601813
ferreiram@jg.co.za
Liz
Day
FCG
0834542309
lizday@mweb.co.za
Kate
Snaddon
FCG
0722327709
katesnaddon@telkomsa.net
Jodi
Lategan
NMMU
Zamekhaya
Somdaka
DEDEAT
0437074101
Julia
Glenday
Living Lands
0795071449
Sithembile
Shaddai
Mbatha
Daniel
Ekurhuleni Metro municipality
DWA Western Cape
0119993140
0219416244
0763053533
0833206605
Sithembile.mbatha@ekurhuleni.gov.za
daniels@dwa.gov.za
Namsha
Muthraparsad
0123368083
0826504736
MuthraparsadN@dwa.gov.za
Tracy
Johnson
DWA: Environment
Recreation
UFS
0761016851
Trace17ed@gmail.com
Dirk
Va wyk
UFS
0835009984
Dirkie.inc@gmail.com
Andre
Beetge
SANBI
0842402264
A.breetge@sanbi.org.za
Mbodi
Maureen
SANBI PTA
0765209831
funolie.maureen@gmail.com
David
Lindley
WWF
0832229155
d.lindley@wwf.gov.za
Nifara
Mahadeo
WWF SA
0731602745
n.mahadeo@wwf.org.za
Grant
?
?
0833246503
grant@manatana.co.za
Henna
De Beer
Eskom
0829404539
henna.dbeer@eskom.co.za
131
0828390786
jodilate@gmail.com
0782598823
zamekhaya.somdaka@deaet.ecape.gov.za
Julia.Glenday@gmail.com
Deliverable 11: Practical Testing / Field Testing Report
10.5. Appendix E – Mitigation measures proposed under Scenario A: Agriculture (irrigated
commercial cropland) for Froggy Pond
Threat Type
Water Quantity - volumes of flow
Water Quantity - patterns of flow
Construction Phase
Sedimentation and turbidity
Threat
Class
Additional
mitigation
measures?
M
N
M
VH
Y
Y
Description
measures
of
proposed
mitigation
Refined
Threat
Class
Specialist justification for refined threat ratings with
clear reference to supporting documentation.
M
Berms to be constructed along contours to
limit concentrated flow paths forming.
Contour-ploughing can be used to limit
erosion risk in the steep slopes alongside
the wetland.
M
Although some practical mitigation measures can be
prescribed for the site and activity, it is unlikely that
this particular risk will be reduced to any large degree.
H
On-site sediment control measures and management
of activities can assist to a degree in reducing sediment
impacts during construction. It is however likely that
the risk of sedimentation will be difficult to reduce due
to the nature of the activity and steep nature of the
slopes in the area above the wetland, hence the threat
class has been adjusted down from Very High to High
only.
This impact will be difficult to mitigate as nutrients
from fertilizers will eventually end up contaminating
inflowing waters to wetlands.
Water Quality - Increased inputs of
nutrients
H
Y
H
Water quality - Increased toxic
contaminants
M
N
M
Water quality – changes in acidity
(pH)
VL
N
VL
Water quality – concentration of
VL
N
VL
132
Deliverable 11: Practical Testing / Field Testing Report
Threat Type
Threat
Class
Additional
mitigation
measures?
VL
N
Description
measures
of
proposed
mitigation
Refined
Threat
Class
Specialist justification for refined threat ratings with
clear reference to supporting documentation.
salts (salinization)
Operational Phase
Water quality – temperature
VL
Water quality – pathogens (i.e.
disease-causing organisms)
M
N
M
Water Quantity - volumes of flow
H
N
H
Water Quantity - patterns of flow
H
Y
Berms to be constructed along contours to
limit concentrated flow paths forming.
M
Contour-ploughing can be used to limit
erosion risk in the steep slopes alongside
the wetland.
H
Sedimentation and turbidity
H
Y
Water Quality - Increased inputs of
nutrients
H
N
H
Water quality - Increased toxic
contaminants
L
N
L
Water quality – changes in acidity
(pH)
VL
N
L
Water quality – concentration of
salts (salinization)
M
N
M
Water quality – temperature
VL
N
L
Water quality – pathogens (i.e.
disease-causing organisms)
M
N
M
133
This impact will be difficult to mitigate as any
bacteria/pathogens from manures will eventually end
up contaminating inflowing waters to wetlands.
Although some practical mitigation measures can be
prescribed for the site and activity, it is unlikely that
this particular risk will be reduced to any large degree.
Deliverable 11: Practical Testing / Field Testing Report
10.6. Appendix F – Mitigation measures proposed under Scenario B: low impact residential
development for Froggy Pond
Threat Type
Water Quantity - volumes of flow
Construction Phase
Water Quantity - patterns of flow
Threat
Class
L
M
Additional
mitigation
measures?
Description of proposed mitigation
measures
Y
Storm water management during
construction to manage/attenuate
flows on-site
Y
Storm water management during
construction to manage/attenuate
flows on-site and redirect away from
wetlands
to
prevent
erosion/scouring.
Sedimentation and turbidity
VH
Y
Recommendations provided for
managing erosion and sedimentation
onsite through practical measures
such as sediment fences/barriers as
well as the consideration of methods
of reducing the risk of erosion
through
dewatering
activities,
managing earthworks/activities on
steep slopes, rehabilitating erosion
points, method/timing and phasing
of activities to reduce risks, etc.
Water Quality - Increased inputs of nutrients
VL
Y
Generic pollution control measures
aimed at managing potential
contaminants on site, reducing risk of
134
Refined
Threat
Class
Specialist justification for refined threat
ratings with clear reference to supporting
documentation.
L
The risk of this impact is considered low
provided that on-site attenuation is
successful
L
A risk of increased runoff from construction
sites will remain during construction
activities. Efforts to direct flows away from
sensitive water resources and to implement a
storm-water management system will help to
reduce these risks.
H
On-site sediment control measures will aim
to limit exposed surfaces and to control
sediment-laden runoff prior to entering
water courses. Potential slope instability
concerns resulting in slumping and erosion
will pose a significant risk until areas are
properly stabilised.
VL
Pollution control measures at source are
specifically aimed to address this risk
Deliverable 11: Practical Testing / Field Testing Report
Threat Type
Threat
Class
Additional
mitigation
measures?
Description of proposed mitigation
measures
Refined
Threat
Class
Specialist justification for refined threat
ratings with clear reference to supporting
documentation.
VL
Pollution control measures at source are
specifically aimed to address this risk
spills, etc.
Water quality - Increased toxic contaminants
VL
Y
Water quality – changes in acidity (pH)
VL
N
VL
Water quality – concentration of salts (salinization)
VL
N
VL
Water quality – temperature
VL
N
VL
Water quality – pathogens (i.e. disease-causing organisms)
Water Quantity - volumes of flow
Water Quantity - patterns of flow
Operational Phase
Generic pollution control measures
aimed at managing potential
contaminants on site, reducing risk of
spills, etc.
Sedimentation and turbidity
VL
L
H
H
Y
Generic
recommendations
for
management of wastes/sanitation,
etc.
Y
Operational
storm
water
management plan including on-site
attenuation
VL
L
The risk of this impact is considered low
provided that on-site attenuation is
successful
Y
Appropriate design of storm water
outlets to reduce flow concentration
and erosion
L
A storm water management system will be
implemented to ensure that releases are
closely aligned with pre-development
conditions
Y
Implement
an
appropriate
Sustainable Urban Drainage System
(SUDS)
characterized
by
a
combination of open, grass-lined
channels/swales and stone-filled
infiltration ditches rather than simply
relying on underground piped
M
On-site mitigation can greatly reduce the
potential for soil erosion and silt-laden runoff
entering wetlands
135
Deliverable 11: Practical Testing / Field Testing Report
Threat Type
Threat
Class
Additional
mitigation
measures?
Refined
Threat
Class
Specialist justification for refined threat
ratings with clear reference to supporting
documentation.
Y
Generic pollution control measures
aimed at managing potential
contaminants on site, reducing risk of
spills, etc.
VL
Pollution control measures at source are
specifically aimed to address this risk
Generic pollution control measures
aimed at managing contaminated
storm water runoff
L
Pollution control measures at source are
specifically aimed to address this risk
Description of proposed mitigation
measures
systems or concrete V-drains
Water Quality - Increased inputs of nutrients
VL
Water quality - Increased toxic contaminants
M
Y
Water quality – changes in acidity (pH)
L
N
L
Water quality – concentration of salts (salinization)
L
N
L
Water quality – temperature
L
N
L
Water quality – pathogens (i.e. disease-causing organisms)
VL
Y
Recommendations
aimed
at
preventing accidental waste water
releases (e.g. management of septic
system with preventative measures,
tie in to municipal piped sewers, etc.)
136
VL
The risk of this impact is considered low
provided that on-site management of waste
water is successful
Deliverable 11: Practical Testing / Field Testing Report
10.7. Appendix G - Mitigation measures proposed for the Mixed-use development scenario at
Hammarsdale wetland
Threat Type
Water Quantity - volumes of flow
Construction Phase
Water Quantity - patterns of flow
Threat
Class
L
M
Additional
mitigation
measures?
Y
Description of proposed mitigation measures
Storm water management during construction to
manage/attenuate flows on-site and redirect away from
wetlands to prevent erosion/scouring.
Y
See above
Recommendations provided for managing erosion and
sedimentation onsite through practical measures such
as sediment fences/barriers as well as the consideration
of methods of reducing the risk of erosion through
dewatering activities, managing earthworks/activities
on steep slopes, rehabilitating erosion points,
method/timing and phasing of activities to reduce risks,
etc.
Sedimentation and turbidity
VH
Y
Water Quality - Increased inputs of
nutrients
VL
Y
Water quality - Increased toxic
contaminants
VL
Y
Water quality – changes in acidity
(pH)
VL
N
Generic pollution control measures aimed at managing
potential contaminants on site, reducing risk of spills,
etc.
Generic pollution control measures aimed at managing
potential contaminants on site, reducing risk of spills,
etc.
Refine
d
Threat
Class
L
L
A risk of increased runoff from construction sites
will remain during construction activities. Efforts
to direct flows away from sensitive water
resources and to implement a storm-water
management system will help to reduce these
risks.
H
On-site sediment control measures will aim to
limit exposed surfaces and to control sedimentladen runoff prior to entering water courses. The
potential height and instability of the platform
banks is a concern however as slumping and
erosion will pose a significant risk until properly
stabilised.
VL
VL
VL
137
Specialist justification for refined threat ratings
with clear reference to supporting
documentation.
Deliverable 11: Practical Testing / Field Testing Report
Threat Type
Water quality – concentration of salts
(salinization)
Water quality – temperature
Additional
mitigation
measures?
Description of proposed mitigation measures
Refine
d
Threat
Class
VL
N
VL
VL
N
VL
Water quality – pathogens (i.e.
disease-causing organisms)
VL
Y
Generic recommendations for management of
wastes/sanitation, etc.
VL
Water Quantity - volumes of flow
L
Y
Operational storm water management plan: including
on-site attenuation, appropriate design of storm water
outlets to reduce flow concentration and erosion
L
Water Quantity - patterns of flow
Operational Phase
Threat
Class
H
Y
See above
Sedimentation and turbidity
H
Y
Implement an appropriate Sustainable Urban Drainage
System (SUDS) characterized by a combination of open,
grass-lined channels/swales and stone-filled infiltration
ditches rather than simply relying on underground
piped systems or concrete V-drains
Water Quality - Increased inputs of
nutrients
VL
Y
Generic pollution control measures aimed at managing
potential contaminants on site, reducing risk of spills,
etc.
Generic pollution control measures aimed at managing
potential contaminants on site, reducing risk of spills,
etc.
Water quality - Increased toxic
contaminants
M
Y
Water quality – changes in acidity
L
N
L
Platforms will be designed to ensure that
drainage from the main platform is away from
the water resource and associated buffer zone. A
stormwater management system will then be
implemented to ensure that releases are closely
aligned with pre-development conditions.
M
Flows from the platforms will be directed away
from the buffer zones. With appropriate bank
stabilization, the risk of erosion of platform banks
can be significantly reduced.
VL
M
L
138
Specialist justification for refined threat ratings
with clear reference to supporting
documentation.
Pollution control measures at source together
with contingency plans are specifically aimed to
address this risk. Depending on the specific types
of industry, risk will be variable but is likely to
remain moderate.
Deliverable 11: Practical Testing / Field Testing Report
Threat Type
Threat
Class
Additional
mitigation
measures?
Description of proposed mitigation measures
Refine
d
Threat
Class
(pH)
Water quality – concentration of salts
(salinization)
Water quality – temperature
Water quality – pathogens (i.e.
disease-causing organisms)
L
N
L
L
N
L
VL
Y
Generic recommendations for management of
wastes/sanitation, etc.
139
VL
Specialist justification for refined threat ratings
with clear reference to supporting
documentation.
Deliverable 11: Practical Testing / Field Testing Report
10.8.
Appendix H: Mitigation measures proposed for the golf course development at Fafa Estuary.
Threat Type
Threat Class
Additional
mitigation
measures?
Description of proposed mitigation measures
Water Quantity - volumes of flow
VL
Y
Managing storm water drains to prevent flows
across the site which could also contribute towards VL
erosion.
Y
Practical management measures onsite to control
erosion and sedimentation- e.g. use of fences or
barriers, storing and reuse of top soil after M
construction, dewatering especially when windy
etc/
Water Quality - Increased inputs of nutrients L
Y
Prevent contamination on site using
measures such as preventing spills etc.
generic
Water quality - Increased toxic contaminants L
Y
Prevent contamination on site using
measures such as preventing spills etc.
generic
Water Quantity - volumes of flow
L
Y
Ensure storm water drains are functioning
L
properly. Irrigate only when necessary.
Sedimentation and turbidity
L
Y
Maintain the vegetation on the slopes to prevent
L
run-off causing erosion
Water Quality - Increased inputs of nutrients H
Y
Use of organic fertilizers, pesticides and herbicides.
Limiting application of chemicals to the fairways,
M
mechanical control of weeds and other generic
pollution control on site.
Water quality - Increased toxic contaminants M
Y
Same as above
Construction Phase
Sedimentation & turbidity
Operational Phase
Specialist justification for
refined threat ratings
Refined
with clear reference to
Threat Class
supporting
documentation.
M
140
VL
VL
L
Deliverable 11: Practical Testing / Field Testing Report
10.9. Appendix I - Mitigation measures proposed for the irrigation development at the Gouritz
Estuary
Threat Type
Threat
Class
Additional
mitigation
measures?
Recommendations provided for managing erosion and
sedimentation onsite through practical measures such as
sediment fences/barriers as well as the consideration of
methods of reducing the risk of erosion through
dewatering activities, managing earthworks/activities on
steep slopes, rehabilitating erosion points, method/timing
and phasing of activities to reduce risks.
Refined
Threat
Class
H
Y
H
Y
H
Y
Water Quantity - patterns of flow
H
Y
Sedimentation and turbidity
H
Y
Capturing run-off and allowing sediments to settle.
M
H
Y
Agricultural run-off will be directed into an artificial
wetland system. Potential use of organic fertilizers.
M
H
Y
Agricultural run-off will be directed into an artificial
wetland system.
M
H
Y
Agricultural run-off will be directed into an artificial
wetland system.
M
Sedimentation and turbidity
Water Quality - Increased inputs of nutrients
Water Quantity - volumes of flow
Operational Phase
Description of proposed mitigation measures
Water Quality - Increased inputs of nutrients
Water quality - Increased toxic contaminants
Water quality – concentration of salts (salinization)
Agricultural run-off will be directed into an artificial
wetland system.
Efficient irrigation systems will need to be applied. Runoff to be channeled into ditches / artificial wetlands.
M
M
M
M
141
Specialist justification for refined
threat ratings with clear reference
to supporting documentation.
On-site sediment control measures
will limit exposed surfaces and
control sediment-laden runoff prior
to entering water courses.
The artificial wetland is expected to
significantly reduce nutrient inputs
to the estuary.
Deliverable 11: Practical Testing / Field Testing Report
10.10. Appendix J – Mitigation measures proposed for the Sappi Ngodwana pulp and paper mill,
Elands River
MITIGATION MEASURES PROPOSED TO ADDRESS RISKS ASSOCIATED WITH PLANNED DEVELOPMENTS / ACTIVITIES
This table provides a description of additional mitigation measures identified to reduce the threat posed by landuses / activities. Where additional mitigation measures are proposed, these must be appropriately justified.
Operational Phase
Construction Phase
Threat Type
Water Quantity - volumes of flow
Water Quantity - patterns of flow
Sedimentation and turbidity
Water Quality - Increased inputs of nutrients
Water quality - Increased toxic contaminants
Water quality – changes in acidity (pH)
Water quality – concentration of salts (salinization)
Water quality – temperature
Water quality – pathogens (i.e. disease-causing organisms)
Water Quantity - volumes of flow
Water Quantity - patterns of flow
Sedimentation and turbidity
Water Quality - Increased inputs of nutrients
Water quality - Increased toxic contaminants
Water quality – changes in acidity (pH)
Water quality – concentration of salts (salinization)
Water quality – temperature
Water quality – pathogens (i.e. disease-causing organisms)
Additional mitigation Description of proposed mitigation measures
Threat Class
measures?
L
N
L
N
H
N
L
N
M
N
VL
N
M
N
L
N
L
N
M
Y
Water used by the mill has been provided by the Ngodwana
L
N
M
N
M
N
Stormwater runoff from the mill will be included into the
H
Y
treatment works.
H
N
VH
N
H
N
L
N
142
Refined Threat Specialist justification for refined threat ratings with clear reference to supporting
Class
documentation.
M
M
Because stormwater runoff will be diverted into waste treatment works threat of
toxics entering Elands River is reduced.
Deliverable 11: Practical Testing / Field Testing Report
10.11. Appendix K - Preliminary buffer zone outcomes calculated using calculations applied in the
draft buffer zone model under a suite of input scenarios. Variables changed under different
scenarios are indicated in yellow.
Low threat
Very Low threat
Scenario
Threat
rating
Climatic
risk
score
Threat
rating
(adjusted
for climate)
0.20
0
0.20
Buffer requirements
Sensitivity
Site-based
attributes
Risk
Score
0.1
1
1
0.5
0.2
1
0.20
1
0.3
0.20
0.5
0.2
0.20
0.5
0.20
Sediment
Retention
Nutrient
Inputs
Pathogen
removal
0.1
2.0
2.0
1.3
1
0.2
1.8
2.3
1.7
1
1
0.3
2.9
2.0
2.8
0.5
1
0.1
2.0
2.0
1.3
0.2
1
1
0.2
1.8
2.3
1.7
0.5
0.2
1.5
1
0.3
2.9
2.0
2.8
0.20
0.5
0.2
1
0.7
0.14
2.0
2.0
1.3
0.20
0.5
0.2
1
1
0.2
1.8
2.3
1.7
0.20
0.5
0.2
1
1.86
0.372
4.7
4.0
4.0
0.20
0
0.1
0.5
0.7
0.035
2.0
2.0
1.4
0.20
0.5
0.2
1
1
0.2
1.8
2.3
1.7
0.20
1
0.3
1.5
1.86
0.837
33.1
60.7
20.9
0.40
0
0.3
1
1
0.3
2.9
2.0
2.8
0.40
0.5
0.4
1
1
0.4
5.5
5.2
4.6
0.40
1
0.5
1
1
0.5
9.5
12.0
7.1
0.40
0.5
0.4
0.5
1
0.2
1.8
2.3
1.7
0.40
0.5
0.4
1
1
0.4
5.5
5.2
4.6
143
Preliminary review on buffer outcomes
Climate has only a small effect on outcomes
Sensitivity has a moderate impact on outcomes
Site-based attributes can have a noticeable impact on
outcomes
When dealing with a highly sensitive ecosystem and
very poor buffer zone, the buffer zone is increased
dramatically. Level of increase seems inappropriate
for sensitivity and site-based attributes > 1.
Climate has only a small effect on outcomes
Sensitivity has a moderate impact on outcomes
Deliverable 11: Practical Testing / Field Testing Report
Threat
High
Moderate threat
Scenario
Threat
rating
Climatic
risk
score
Threat
rating
(adjusted
for climate)
0.40
0.5
0.40
Buffer requirements
Sensitivity
Site-based
attributes
Risk
Score
0.4
1.5
1
0.5
0.4
1
0.40
0.5
0.4
0.40
0.5
0.40
Sediment
Retention
Nutrient
Inputs
Pathogen
removal
0.6
14.8
22.3
10.3
0.7
0.28
2.6
1.8
2.5
1
1
0.4
5.5
5.2
4.6
0.4
1
1.86
0.744
25.0
43.3
16.3
0
0.3
0.5
0.7
0.105
2.0
2.0
1.3
0.40
0.5
0.4
1
1
0.4
5.5
5.2
4.6
0.40
1
0.5
1.5
1.86
1
50.2
98.7
30.5
0.60
0
0.5
1
1
0.5
9.5
12.0
7.1
0.60
0.5
0.6
1
1
0.6
14.8
22.3
10.3
0.60
1
0.7
1
1
0.7
21.6
36.1
14.3
0.60
0.5
0.6
0.5
1
0.3
2.9
2.0
2.8
0.60
0.5
0.6
1
1
0.6
14.8
22.3
10.3
0.60
0.5
0.6
1.5
1
0.9
39.2
74.3
24.4
0.60
0.5
0.6
1
0.7
0.42
6.2
6.3
5.0
0.60
0.5
0.6
1
1
0.6
14.8
22.3
10.3
0.60
0.5
0.6
1
1.86
1
50.2
98.7
30.5
0.60
0
0.5
0.5
0.7
0.175
2.0
2.0
1.5
0.60
0.5
0.6
1
1
0.6
14.8
22.3
10.3
0.60
1
0.7
1.5
1.86
1
50.2
98.7
30.5
0.80
0
0.7
1
1
0.7
21.6
36.1
14.3
0.80
0.5
0.8
1
1
0.8
29.7
53.4
19.0
144
Preliminary review on buffer outcomes
Site-based attributes can have a major impact on
outcomes
When dealing with a highly sensitive ecosystem and
very poor buffer zone, the buffer zone is increased
dramatically. Level of increase seems inappropriate
for sensitivity and site-based attributes > 1.
Climate has only a small effect on outcomes
Sensitivity effect has increased considerably.
Variability is regarded as too high. To consider
refining the range of scores assigned to the sensitivity
assessment.
Site-based attributes can have a major impact on
outcomes. Variability is regarded as too high. To
consider refining the range of scores assigned to the
site-based attributes.
Range is far too variable. Adjustment to accounting
methodology definitely required.
Deliverable 11: Practical Testing / Field Testing Report
Very High Threat
Scenario
Threat
rating
Climatic
risk
score
Threat
rating
(adjusted
for climate)
0.80
1
0.80
Buffer requirements
Sensitivity
Site-based
attributes
Risk
Score
0.9
1
1
0.5
0.8
0.5
0.80
0.5
0.8
0.80
0.5
0.80
Sediment
Retention
Nutrient
Inputs
Pathogen
removal
0.9
39.2
74.3
24.4
1
0.4
5.5
5.2
4.6
1
1
0.8
29.7
53.4
19.0
0.8
1.5
1
1
50.2
98.7
30.5
0.5
0.8
1
0.7
0.56
12.5
17.7
9.0
0.80
0.5
0.8
1
1
0.8
29.7
53.4
19.0
0.80
0.5
0.8
1
1.86
1
50.2
98.7
30.5
0.80
0
0.7
0.5
0.7
0.245
2.1
1.8
2.1
0.80
0.5
0.8
1
1
0.8
29.7
53.4
19.0
0.80
1
0.9
1.5
1.86
1
50.2
98.7
30.5
1.00
0
0.9
1
1
0.9
39.2
74.3
24.4
1.00
0.5
1
1
1
1
50.2
98.7
30.5
1.00
1
1.1
1
1
1
50.2
98.7
30.5
1.00
0.5
1
0.5
1
0.5
9.5
12.0
7.1
1.00
0.5
1
1
1
1
50.2
98.7
30.5
1.00
0.5
1
1.5
1
1
50.2
98.7
30.5
1.00
0.5
1
1
0.7
0.7
21.6
36.1
14.3
1.00
0.5
1
1
1
1
50.2
98.7
30.5
1.00
0.5
1
1
1.86
1
50.2
98.7
30.5
1.00
0
0.9
0.5
0.7
0.315
3.2
2.3
3.0
1.00
0.5
1
1
1
1
50.2
98.7
30.5
1.00
1
1.1
1.5
1.86
1
50.2
98.7
30.5
145
Preliminary review on buffer outcomes
Deliverable 11: Practical Testing / Field Testing Report
10.12. Appendix L - Refined buffer zone outcomes based on revisions to buffer zone calculations.
Variables changed under different scenarios are indicated in yellow.
Low threat
Very Low threat
Scenario
Threat
rating
Climatic
risk
score
Threat rating
(adjusted for
climate)
0.20
0
0.20
Sensitivity
Site-based
attributes
Risk
Score
0.10
1
1
0.5
0.20
1
0.20
1
0.30
0.20
0.5
0.20
Buffer requirements
Sediment
Retention
Nutrient
Inputs
Pathogen
removal
0.10
2.0
2.0
1.3
1
0.20
1.8
2.3
1.7
1
1
0.30
2.9
2.0
2.8
0.20
0.85
1
0.17
2.0
2.0
1.5
0.5
0.20
1
1
0.20
1.8
2.3
1.7
0.20
0.5
0.20
1.15
1
0.23
2.0
1.9
1.9
0.20
0.5
0.20
1
0.7
0.20
1.2
1.6
1.2
0.20
0.5
0.20
1
1
0.20
1.8
2.3
1.7
0.20
0.5
0.20
1
1.86
0.20
3.3
4.4
3.1
0.20
0
0.10
0.85
0.7
0.09
1.4
1.4
0.9
0.20
0.5
0.20
1
1
0.20
1.8
2.3
1.7
0.20
1
0.30
1.15
1.86
0.35
7.3
5.6
6.5
0.40
0
0.30
1
1
0.30
2.9
2.0
2.8
0.40
0.5
0.40
1
1
0.40
5.5
5.2
4.6
0.40
1
0.50
1
1
0.50
9.5
12.0
7.1
0.40
0.5
0.40
0.85
1
0.34
3.8
2.9
3.4
0.40
0.5
0.40
1
1
0.40
5.5
5.2
4.6
0.40
0.5
0.40
1.15
1
0.46
7.7
8.9
6.0
0.40
0.5
0.40
1
0.7
0.40
3.9
3.7
3.2
146
Preliminary review on buffer outcomes
Minimum buffer requirements would override
these low values
Climate has a moderate effect on outcomes
with buffers of nearly double the size proposed
for high rainfall areas relative to arid areas with
limited storm water runoff.
Sensitivity has a minor effect on outcomes in
scenarios with very low risk ratings
Site-based attributes have a more significant
Deliverable 11: Practical Testing / Field Testing Report
eat
Thr
h
Hig
Moderate threat
Scenario
Threat
rating
Climatic
risk
score
Threat rating
(adjusted for
climate)
0.40
0.5
0.40
Sensitivity
Site-based
attributes
Risk
Score
0.40
1
1
0.5
0.40
1
0.40
0
0.30
0.40
0.5
0.40
Buffer requirements
Sediment
Retention
Nutrient
Inputs
Pathogen
removal
Preliminary review on buffer outcomes
0.40
5.5
5.2
4.6
1.86
0.40
10.3
9.7
8.5
impact on outcomes in scenarios with very low
risk ratings
0.85
0.7
0.26
1.6
1.2
1.5
0.40
1
1
0.40
5.5
5.2
4.6
1
0.50
1.15
1.86
0.58
24.8
36.0
17.6
0.60
0
0.50
1
1
0.50
9.5
12.0
7.1
0.60
0.5
0.60
1
1
0.60
14.8
22.3
10.3
0.60
1
0.70
1
1
0.70
21.6
36.1
14.3
0.60
0.5
0.60
0.85
1
0.51
9.9
12.8
7.4
0.60
0.5
0.60
1
1
0.60
14.8
22.3
10.3
0.60
0.5
0.60
1.15
1
0.69
20.8
34.5
13.9
0.60
0.5
0.60
1
0.7
0.60
10.4
15.6
7.2
0.60
0.5
0.60
1
1
0.60
14.8
22.3
10.3
0.60
0.5
0.60
1
1.86
0.60
27.6
41.4
19.2
0.60
0
0.50
0.85
0.7
0.43
4.5
4.6
3.6
0.60
0.5
0.60
1
1
0.60
14.8
22.3
10.3
0.60
1
0.70
1.15
1.86
0.81
56.1
101.2
35.8
The range of recommended buffers is highly
variable when taking factors affecting risk and
site based attributes into account. While the
variability is quite high, much of the variability
would be reduced when applying a minimum
15m buffer.
0.80
0
0.70
1
1
0.70
21.6
36.1
14.3
Climate has a moderate effect on outcomes
147
Notable increases in BZ requirements for highly
sensitive systems with buffer attributes poorly
suited to reduce impacts from diffuse source
pollution.
Climate has a moderate effect on outcomes
with buffers of nearly double the size proposed
for high rainfall areas relative to arid areas with
limited storm water runoff.
Sensitivity has a clear impact on outcomes,
with buffer zones nearly doubling for highly
sensitive systems relative to those of very low
sensitivity.
Site factors have a major influence on buffer
zone requirements. This is consistent with the
literature which suggests that buffer width
alone is only one of the factors determining
buffer zone effectiveness.
Deliverable 11: Practical Testing / Field Testing Report
Very High Threat
Scenario
Threat
rating
Climatic
risk
score
Threat rating
(adjusted for
climate)
0.80
0.5
0.80
Sensitivity
Site-based
attributes
Risk
Score
0.80
1
1
1
0.90
1
0.80
0.5
0.80
0.80
0.5
0.80
Buffer requirements
Sediment
Retention
Nutrient
Inputs
Pathogen
removal
Preliminary review on buffer outcomes
0.80
29.7
53.4
19.0
1
0.90
39.2
74.3
24.4
with buffers of nearly double the size proposed
for high rainfall areas relative to arid areas with
limited storm water runoff.
0.85
1
0.68
20.1
33.0
13.5
0.80
1
1
0.80
29.7
53.4
19.0
0.5
0.80
1.15
1
0.92
41.3
78.9
25.5
0.80
0.5
0.80
1
0.7
0.80
20.8
37.4
13.3
0.80
0.5
0.80
1
1
0.80
29.7
53.4
19.0
0.80
0.5
0.80
1
1.86
0.80
55.3
99.4
35.3
0.80
0
0.70
0.85
0.7
0.60
10.2
15.2
7.1
0.80
0.5
0.80
1
1
0.80
29.7
53.4
19.0
0.80
1
0.90
1.15
1.86
1.04
101.0
201.1
60.9
1.00
0
0.90
1
1
0.90
39.2
74.3
24.4
1.00
0.5
1.00
1
1
1.00
50.2
98.7
30.5
1.00
1
1.10
1
1
1.10
62.5
126.7
37.3
1.00
0.5
1.00
0.85
1
0.85
34.3
63.4
21.6
1.00
0.5
1.00
1
1
1.00
50.2
98.7
30.5
1.00
0.5
1.00
1.15
1
1.15
69.2
142.0
40.9
148
Sensitivity has a clear impact on outcomes,
with buffer zones nearly doubling for highly
sensitive systems relative to those of very low
sensitivity.
Site factors have a major influence on buffer
zone requirements. This is consistent with the
literature which suggests that buffer width
alone is only one of the factors determining
buffer zone effectiveness.
The range of recommended buffers is highly
variable when taking factors affecting risk and
site based attributes into account. While the
variability is quite high, much of the variability
would be reduced when applying a minimum
15m buffer.
Climate has a moderate effect on outcomes
with buffers of nearly double the size proposed
for high rainfall areas relative to arid areas with
limited storm water runoff.
Sensitivity has a clear impact on outcomes,
with buffer zones nearly doubling for highly
sensitive systems relative to those of very low
sensitivity.
Deliverable 11: Practical Testing / Field Testing Report
Scenario
Threat
rating
Climatic
risk
score
Threat rating
(adjusted for
climate)
1.00
0.5
1.00
Sensitivity
Site-based
attributes
Risk
Score
1.00
1
0.7
0.5
1.00
1
1.00
0.5
1.00
1.00
0
1.00
1.00
Buffer requirements
Sediment
Retention
Nutrient
Inputs
Pathogen
removal
Preliminary review on buffer outcomes
1.00
35.1
69.1
21.3
1
1.00
50.2
98.7
30.5
1
1.86
1.00
93.3
183.7
56.6
Site factors have a major influence on buffer
zone requirements. This is consistent with the
literature which suggests that buffer width
alone is only one of the factors determining
buffer zone effectiveness.
0.90
0.85
0.7
0.77
18.7
32.9
12.1
0.5
1.00
1
1
1.00
50.2
98.7
30.5
1
1.10
1.15
1.86
1.27
159.7
335.9
93.1
149
The range of recommended buffers is highly
variable when taking factors affecting risk and
site based attributes into account. While the
variability is quite high, much of the variability
would be reduced when applying a minimum
15m buffer.