Norfolk & Suffolk Team
Dragonfly House
2 Gilders Way
Norwich
Norfolk NR3 2UB
Tel No 0845 600 3078
www.naturalengland.org.uk
Email: enquiries@naturalengland.org.uk
CONSERVATION OBJECTIVES and DEFINITIONS OF FAVOURABLE
CONDITION for DESIGNATED FEATURES OF INTEREST:
These Conservation Objectives relate to all designated features on the SSSI,
whether designated as SSSI, SPA, SAC or Ramsar features.
Name of Site of Special Scientific Interest (SSSI)
River Wensum
Names of designated international sites
River Wensum
Special Area for Conservation (SAC)
Special Protection Area (SPA)
N/A
N/A
Ramsar:
Relationship between site designations
In relation to the River Wensum SSSI, the boundary of the Wensum SAC is concurrent with
the boundary of the SSSI, with the exception that the SAC does not include Site Unit 7.
Version Control information
Final
Status of this Version (Draft, Consultation Draft,
Final)
Prepared by:
Richard Leishman
Date of this version:
16 03 11
CSM Guidance for Rivers and Streams (Mar
Date of generic guidance on favourable condition
2005)
used:
Other notes/version history :
Quality Assurance information
Checked by
Name: Peter Leverton
Date: 16 03 11
Signature
Peter Leverton
Conservation Objectives: River Wensum
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Conservation Objectives and definitions of Favourable Condition: notes for users
Conservation Objectives
SSSIs are notified because of specific biological or geological features. Conservation
Objectives define the desired state for each site in terms of the features for which they have
been designated. When these features are being managed in a way which maintains their
nature conservation value, then they are said to be in ‘favourable condition’. It is a
Government target that 95% of the total area of SSSIs should be in favourable condition by
2010.
Definitions of Favourable Condition
The Conservation Objectives are accompanied by one or more habitat extent and quality
definitions for the special interest features at this site. These are subject to periodic
reassessment and may be updated to reflect new information or knowledge; they will be used
by Natural England and other relevant authorities to determine if a site is in favourable
condition. The standards for favourable condition have been developed and are applied
throughout the UK.
Use under the Habitats Regulations
The Conservation Objectives and definitions of favourable condition for features on the SSSI
may inform the scope and nature of any ‘appropriate assessment’ under the Habitats
Regulations. An appropriate assessment will also require consideration of issues specific to
the individual plan or project. The habitat quality definitions do not by themselves provide a
comprehensive basis on which to assess plans and projects as required under Regulations 2021, 24, 48-50 and 54 - 85. The scope and content of an appropriate assessment will depend
upon the location, size and significance of the proposed project. Natural England will advise
on a case by case basis.
Following an appropriate assessment, competent authorities are required to ascertain the
effect on the integrity of the site. The integrity of the site is defined in para C10 of PPG9 as
the coherence of its ecological structure and function, across its whole area, that enables it to
sustain the habitat, complex of habitats and/or the levels of populations of the species for
which it was classified. The determination of favourable condition is separate from the
judgement of effect upon integrity. For example, there may be a time-lag between a plan or
project being initiated and a consequent adverse effect upon integrity becoming manifest in
the condition assessment. In such cases, a plan or project may have an adverse effect upon
integrity even though the site remains in favourable condition.
The formal Conservation Objectives for European Sites under the Habitats Regulations are in
accordance with para. C10 of PPG 9, the reasons for which the European Site was classified or
designated. The entry on the Register of European Sites gives the reasons for which a European
Site was classified or designated.
Explanatory text for Tables 2a, 2b, 3a, 3b, 3c, 3d, 3e, 3f
Tables 2a, 2b, 3a, 3b, 3c, set out the measures of condition which we will use to provide
evidence to support our assessment of whether features are in favourable condition. They are
derived from a set of generic guidance on favourable condition prepared by NE specialists,
and have been tailored by local staff to reflect the particular characteristics and site-specific
circumstances of individual sites. Quality Assurance has ensured that such site-specific
tailoring remains within a nationally consistent set of standards. The tables include an audit
trail to provide a summary of the reasoning behind any site-specific targets etc. In some cases
the requirements of features or designations may conflict; the detailed basis for any
reconciliation of conflicts on this site may be recorded elsewhere. Tables 3d, 3e and 3f
present non-mandatory objectives which are related to biodiversity hosted by the SSSI.
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Conservation Objectives
The Conservation Objectives for this site are, subject to natural change, to maintain the
following habitats and geological features in favourable condition (*), with particular
reference to any dependent component special interest features (habitats, vegetation types,
species, species assemblages etc.) for which the land is designated (SSSI, SAC, SPA, Ramsar)
as individually listed in Table 1.
Habitat Types represented (Biodiversity Action Plan categories)
Rivers & Streams
Geological features (Geological Site Types)
Not applicable
(*) or restored to favourable condition if features are judged to be unfavourable.
Standards for favourable condition are defined with particular reference to the specific
designated features listed in Table 1, and are based on a selected set of attributes for features
which most economically define favourable condition as set out in Tables 2a, 2b, 3a, 3b, 3c,
3d, 3e, 3f
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Table 1 Individual designated interest features
Type III Group AIIIb-chalk river
N.B. Any sections classified as
Type IV are considered to be in
unfavourable condition.
Water course of plain to montane
levels with the Ranunculion
fluitantis and Callitricho
batrachion vegetation
Cottus gobio
Lampetra planeri
Austropotamobius pallipes
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Aquatic
vegetation
characterised by
species of watercrowfoot and
starwort
Bullhead
Brook lamprey
White-clawed
crayfish
*
*
*
*
*
3c 1% of
population
3a 20000
waterfowl
*
2a Hosting
rare species
&c
*
Ramsar criteria applicable to
specific habitats
1a Wetland
characteristics
River & streams
Waterfowl
assemblage
Type I Group A1c-fenland river
Migratory
species
Rivers & Streams
SPA bird populations
dependency on specific
habitats
Annex 1
species
Explanatory
description of the
feature for
clarification
SAC designated
interest features
Specific designated features
SSSI designated
interest features
BAP Broad Habitat
Type
*
Lowland
meadows
(*)
Heathland
(*)
Broadleaved, Mixed
& Yew Woodland
Lowland Neutral
Grassland
Dry Heathland
NB.
W6 Alnus glutinosa-Urtica dioica woodland
MG8 Cynosurus cristatus-Caltha palustris
grassland, MG8-related (south) M22, M23
lowland meadows
H8 Calluna vulgaris – Ulex gallii heath
3c 1% of
population
Desmoulin’s
whorl snail
Wet woodland
S5 Glyceria maxima swamp
S7 Carex acutiformis swamp
S25 Phragmites australis-Eupatorium
cannabinum tall-herb fen, Cladium mariscus
sub-community.
Vertigo moulinsiana
3a 20000
waterfowl
[*]
[*]
Ramsar criteria applicable to
specific habitats
1a Wetland
characterist
ics
2a Hosting
rare species
&c
Sedge swamp
Swamp and
reed-bed
Swamp
Swamp
Tall-herb fen
Waterfowl
assemblage
S3 Carex paniculata sedge-swamp
S4 Phragmites australis swamp and reed-beds
Migratory
species
Fen, Marsh &
Swamp
SPA bird populations
dependency on
specific habitats
Annex 1
species
Explanatory
description of
the feature for
clarification
SAC designated
interest features
Specific designated features
SSSI designated
interest features
BAP Broad Habitat
Type
[*]
[*]
[*]
*
(*)
Features where asterisks are in round brackets (*) indicate habitats which are not notified for specific habitat interest (under the relevant designation)
but have been included within the boundary of the site, either because they are hydrologically linked to the River Wensum, or in the case of the dry
heathland at Great Ryburgh Common, because an area of W10 woodland on ground just outwith the floodplain includes a clearing that supports this
habitat. Features where asterisks are in square brackets [*] indicate habitats which are not notified for specific habitat interest (under the relevant
designation) but should be regarded as being of special interest as they host populations of Desmoulin’s whorl snail.
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Audit Trail
Rationale for the identification of the features of special interest of the SSSI
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The features of special interest - The River Wensum SSSI was selected as a ‘whole river SSSI’ (1989 Guidelines on the selection of biological SSSIs:
Freshwater habitats – paragraph 6.2.1). It is classified as a JNCC River Type III: “lowland chalk & oolite rivers with generally stable flow regimes” with a
transition in its downstream section to Type I “lowland rivers with minimal gradients on mixed geology in England”. In addition the site was submitted to
Europe as it supports the Annex I Corine Biotope: Water course of plain to montane levels with the Ranunculion fluitantis and Callitricho batrachion
vegetation. This Biotope is the habitat hosted by Type III and Type I rivers and the two JNCC river types and the Annex I habitat they support should be
regarded as an interest feature of the SSSI.
Of the invertebrates that are present on the site, Desmoulin’s whorl snail and white-clawed crayfish are highlighted as being of particular significance and are
two of the European features for which the River Wensum was submitted to Europe as an SAC. Desmoulin’s whorl snail and white-clawed crayfish are
should therefore be regarded as separate features of interest in their own right. However, it should be noted the invertebrate assemblage is not regarded as an
interest feature of the SSSI.
The remaining two European features hosted by the River Wensum SSSI are bullhead and brook lamprey, and populations of both of these species should also
be regarded as features of special interest of the SSSI.
Although the Citation and the Criterion Sheet make reference to the vascular plant assemblage, which includes over 100 species of vascular plants, this
assemblage does not support a sufficient number of Nationally Scarce or Nationally Rare species to quality as an interest feature in its own right.
Condition Assessment of River Units - Where the freshwater habitat of a site is designated (as either SSSI or SAC), conservation objectives and associated
condition assessment should be based on the relevant generic habitat FCT(s), featuring a range of environmental attributes and consideration of the plant
community. If there are additional freshwater species designations on the site, environmental attributes in the relevant species FCTs should only be considered
if the generic habitat FCT inadequately safeguards habitat conditions for the species. Bespoke species monitoring would generally only be used as a crosscheck on site condition rather than as a routine assessment tool. Therefore, the presumption is that the conservation objectives will be based on the relevant
generic habitat FCT, with additional consideration of the environmental targets in generic species FCTs only where the habitat FCT is inadequate to protect
the relevant species.
Bullhead (Cottus gobio), Brook lamprey (Lampetra planeri), and White-clawed crayfish (Austropotamobius pallipes), are all species which are associated
with and dependant on the Annex I Corine Biotope: Water course of plain to montane levels with the Ranunculion fluitantis and Callitricho batrachion
vegetation and it is therefore deemed appropriate for the condition of the river units to be determined through an assessment of the condition of this biotope.
Non-mandatory methodologies for the assessment of these species are presented in Tables 4a, 4b, 4c & 4d.
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Condition Assessment of terrestrial units - In accordance with the 1989 Guidelines, the River Wensum SSSI also includes areas of adjoining terrestrial
habitat. The guidelines state that, “Any adjacent semi-natural, wet habitat which is intimately linked with the river and which is probably dependent on the
river for its continued existence should be included within the SSSI boundary. Such areas may be unimproved alluvial flood-plain meadows, marshland, wet
heathland, fens, bogs, flushes, swamps and wet woodland such as willow and alder carr.” It can therefore be inferred that:

The River Wensum SSSI was selected for the aquatic and emergent communities that the river supports and was not selected for the presence of specific
grassland, fen or mire communities that are present on those areas of the floodplain included within the boundary of the site. In order to qualify for
inclusion within the site boundary, terrestrial compartments were selected against less stringent criteria than is the case for the selection of sites supporting
specific vegetation communities associated with floodplain habitats.

The terrestrial compartments were selected because they are semi-natural and because they are hydrologically linked with the river. This defines their
special interest. Their inclusion within the boundary of the site was necessary in order to represent the range of floodplain habitats associated with the
river to maintain selected areas from the overall mosaic of habitats within the floodplain.
The interest of the terrestrial compartments is reflected in the Citation Sheet, and statements and objectives in the Site Objective Statement. The latter states
that, “Adjacent habitat areas of wet, semi-natural habitat included as they form an integral & dependent part of the river system”. However, the Site Objective
Statement presents targets such as: “Maintain and enhance adjacent semi-natural habitat within the SSSI”, and; “Maintain and enhance the vascular plant
species diversity”. This can be accommodated by regarding the vegetation communities of the terrestrial compartments as hosted features of biodiversity
interest and Tables 3c, 3d, 3e & 3f provide non-mandatory objectives in relation to hosted features of biodiversity.
The exceptions to this rationale are the habitats that support Desmoulin’s whorl snail. Desmoulin’s whorl snail is the only one of the European features which
is associated with habitats that occur on the terrestrial compartments. The favourable condition tables for this snail indicate that its status can be maintained
by ensuring that the appropriate vegetation communities that support this feature are maintained. While these tall herb swamp and fen communities are not
features of special interest in their own right, monitoring of their extent and structure will be necessary in order to evaluate the favourable condition of this
species on the site.
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Table 2 Habitat Features - Extent Objectives
Conservation Objective
for habitat extent
Extent - Dynamic
balance
To maintain the designated habitats in favourable condition, which is defined in part in relation to a balance of habitat extent
(extent attribute). Favourable condition is defined at this site in terms of the following site-specific standards:
On this site favourable condition requires the maintenance of the extent of each designated habitat type. Maintenance implies
restoration if evidence from condition assessment suggests a reduction in extent.
Habitat Feature (BAP
Broad Habitat level, or
more detailed level if
applicable)
Estimated extent
(ha) and date of
data source/estimate
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Site Specific Target range and Measures
Comments
Rivers & Streams
71 kilometres
Watercourses Characterised
by Ranunculion fluitantis
and Callitricho-Batrachion
Vegetation.
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Much of the river is over-widened, over-deepened,
and impounded. As a result the area of
watercourse has been artificially enlarged. As
river restoration is implemented, and the
impounding impacts of structures reduced, so the
quality of the river habitat will improve, while
paradoxically its area will diminish. It is therefore
more appropriate to provide data on the length of
watercourse, rather than its area.
Where river restoration occurs, this may involve
diverting the river from engineered channels, and
back into earlier river channels. As little of the
floodplain is included within the boundary of the
SSSI, this involves diverting the river outwith the
designated boundary.
Where the river has been diverted from the
notified boundary of the SSSI, and designated
boundary of the SAC, any proposals of owners /
occupiers / statutory bodies to modify these
channels require Section 28E consent, or Section
28G assent, unless the proposed activities are
permitted under other mechanisms, in which case
Natural England would be consulted in relation to
Section 28I advice.
It is expected that environmental targets laid down by the FCT
will be complied with throughout the site.
This has implications with regard to the targeting of HLS on the
whole of the floodplain of the River Wensum, and on the
evaluation of management of banks and watercourses connected
to the River Wensum as practiced on land within existing agrienvironment agreements.
It should be noted that the tributaries of the Wensum, that have
not been included within the boundary of the SSSI also support
the habitats and species for which the site was notified. These
tributaries therefore have a strong relationship with the integrity
of the river as a whole.
The appropriate survey methodologies for Watercourses
characterised by Ranunculion fluitantis and CallitrichoBatrachion Vegetation have been assimilated within table 3a Site-Specific definitions of Favourable Condition for freshwater
habitats and species on the River Wensum SSSI.
All river units should be regarded as having the potential to
support populations Ranunculion fluitantis
and Callitricho-Batrachion Vegetation.
Fen, Marsh and Swamp
-
Desmoulin’s whorl snail
As indicated above, the individual floodplain
communities are not regarded as interest features
in their own right. However, those plant
communities which support Desmoulin’s whorl
snail are regarded as an interest feature by default.
In addition to maintaining the semi-natural communities of the
terrestrial compartments of the SSSI, HLS schemes should be
targeted at maintaining the biodiversity of the floodplain
corridor as a whole.
With regard to the area of fen, marsh and swamp,
as a whole, there should be a presumption against
the loss of these important BAP habitats.
It should be noted that Desmoulin’s whorl snail occupies fen
communities on the wider floodplain, including land-parcels
within the boundary of the SSSI, but also floodplain habitats
outwith the boundary of the site, e.g. Great Witchingham
Common, which supports the strongest know population in the
Wensum Valley.
However, in the case of those fen, marsh and
swamp communities which support Desmoulin’s
whorl snail, there should be no reduction in the
total combined extent of wetland. No more than
25% reduction from baseline in core habitat area
or abundance of food plant.
Refer to current and previous aerial photographs
for baseline.
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It is anticipated that during the course of river restoration, some
habitat which currently supports Desmoulin’s whorl snail may
be lost, while opportunities for increasing the extent of suitable
habitat in other areas are likely to occur. This snail is known to
have a good ability to colonise suitable habitat, and the
expectation is that it behaves as a metacolony within the river
system as a whole.
Broadleaved, Mixed and
Yew Woodland
-
Although as indicated above, the individual
floodplain communities are not regarded as
interest features in their own right, there should be
a presumption against the loss of these important
BAP habitats, and certainly no loss of ancient
semi-natural stands
At least current area of recent semi-natural stands
maintained, although their location may alter.
Targets for extent may be modified where a target has been set
to increase the extent of other habitat features on the site at the
expense of woodland
In addition to maintaining the semi-natural communities of the
terrestrial compartments of the SSSI, HLS schemes should be
targeted at maintaining the biodiversity of the floodplain
corridor as a whole.
It should be noted that bank-side trees are of
particular significance in providing diversity of
light and shade, and also in providing woody
debris to the river.
Refer to current and previous aerial photographs
for baseline
Lowland Neutral Grassland
-
Although, as indicated above, the individual
floodplain communities are not regarded as
interest features in their own right, there should be
a presumption against the loos of these important
BAP habitats.
No reduction in area and any consequent
fragmentation without prior consent
Refer to current and previous aerial photographs
for baseline
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In addition to maintaining the semi-natural communities of the
terrestrial compartments of the SSSI, HLS schemes should be
targeted at maintaining the biodiversity of the floodplain
corridor as a whole.
Rationale for site-specific targets (including any variations from generic guidance)
Rationale for the subdivision of site specific targets: Specific targets are presented in 6 separate tables:

Riverine Interests – Mandatory objectives (Table 3a) - The riverine habitats constitute the core interest of the River Wensum SSSI and mandatory objectives are
presented in this table. These targets have implications with regard to the management of the river, the management of the floodplain, and the management of the
catchment as a whole.

Common objectives for all terrestrial compartments – Mandatory and non-mandatory objectives (Table 3b) - Mandatory objectives for all the terrestrial
compartments of the SSSI should ensure that these continue to support semi-natural communities and remain hydrologically linked to the river. In addition, the
management of the terrestrial compartments of the SSSI and adjacent floodplain habitats should not negatively impact the riverine interest of the SSSI. Mandatory
objectives for the terrestrial compartments, and non mandatory objectives for bank-side habitats are presented in this table.

Terrestrial Compartments supporting tall fen and swamp communities – Mandatory objectives (Table 3c) – Although these BAP habitats are effectively hosted by
the River Wensum SSSI, many of these communities support populations of Desmoulin’s whorl snail. Objectives for these communities should therefore be regarded as
mandatory so as to ensure that populations of Desmoulin’s whorl snail are maintained in favourable condition.

Terrestrial Compartments – Non-mandatory objectives for semi-natural vegetation communities - The woodlands, grasslands and heathland communities present
on the terrestrial compartments are BAP habitats that are hosted by the SSSI. The objectives for these communities are therefore non-mandatory and are presented as
follows:

Broadleaved, Mixed and Yew Woodland (Table 3d)

Lowland Neutral Grassland (Table 3e)

Heathland (Table 3f)
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Other Notes
Maintenance of the range of terrestrial habitats on the floodplain and implications with regard to agri-environment schemes and Woodland Grant Schemes
Although the River Wensum SSSI was primarily notified for its river communities, there is a recognition that where the river is hydrologically linked to its floodplain, the
predominance of semi-natural vegetation and the range of grasslands, fens, and woodland that are present contribute to the richness of the fauna and flora in the river its-self.
In relation to this point the citation states, “Unusually for a lowland river in England, much of the adjacent land is still traditionally managed for hay crops and by grazing,
giving a wide spectrum of grassland habitats some of which are seasonally inundated. The mosaic of meadow and marsh habitats, including one of the most extensive reedbeds in the county outside the Broads, provide niches for a wide variety of specialised plants and animals.”
The importance of this juxtaposition of habitats is indicated by the assemblages of breeding birds and invertebrates that utilise floodplain and river habitats. Of particular note
are breeding waders such as snipe; kingfisher and sand martin which utilise the river banks for nesting; wildfowl such as little grebe, gadwall, pochard, and water rail; and a
range of passerines such as reed warblers, sedge warblers and grey wagtail. The larger reed-beds support breeding marsh harrier, and are used as feeding or resting areas by
bittern. With regard to the assemblages of invertebrates that are supported by the site, these include: 10 species of mayflies, 19 molluscs, 25 caddis-flies and 10 water beetles.
The assemblage is dependent on the juxtaposition of river and terrestrial habitats in order to provide for all stages of aquatic and terrestrial life-cycle.
Although the River Wensum SSSI has not been notified specifically for each of the individual grassland, fen and woodland communities that occupy the terrestrial
compartments of the SSSI and adjacent floodplain habitats, the maintenance of these habitats is desirable. For this reason, non-mandatory targets have been set for the
grassland, and woodland communities on the floodplain with a view to ensuring that the range and diversity of semi-natural communities are protected, enhanced, and where
opportunities arise, extended across the floodplain.
However, the Criteria Sheet broadly specifies the habitats that the terrestrial compartments support and this should be used as a guide in relation to understanding the more
significant communities where a mosaic exists (see below).
Although these objectives need not be adopted for the purposes of formal condition assessment, they will be of assistance in drawing up the objectives for agri-environment
schemes and Woodland Grant Schemes, and for evaluating the appropriateness of proposals, both on the terrestrial units of the River Wensum SSSI but also with regard to
habitats on the wider floodplain as a whole.
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The Favourable Condition Tables should influence HLS,ELS, CSF, and WGS applications with regard to the following:






To reduce the wider catchment diffuse pollution issues that are contributing to the unfavourable condition of the eleven river units.
To ensure that the terrestrial units of the River Wensum SSSI continue to support semi-natural vegetation ;that they should be hydrologically linked to the river and that
the management of this vegetation is compatible with the special interest of the river.
To ensure that the management of the land immediately adjacent to the river, but outwith the boundary of the SSSI is compatible with the special interest of the river.
To deliver wider biodiversity objectives in terms of the Norfolk Ecological Network and Norfolk Biodiversity Action Plan
Creation of additional floodplain habitat on land adjacent to those areas of the floodplain that already support diverse habitats.
Where appropriate, to reverse seral change which has occurred as a result of the abandonment of traditional management of floodplain habitats.
As indicated above, the Criteria Sheet broadly specifies the habitats present in the terrestrial compartments as follows:


















Two areas of land adjacent to the River Tat – Unimproved meadow
Shereford: land north of river – Fen, with encroaching scrub and alder carr
Shereford: land south of river – Fen (northern section); unimproved meadow with wet pools (southern section)
Sculthorpe Moor – Fen, with invasive scrub and alder carr
Land at Fakenham – Fen
Great Ryburgh Common – Unimproved meadow, fen and scrub.
Land between Starmoor plantation and Spa Well Wood – Unimproved meadow
Kettlestone Common – Unimproved meadow
Little Ryburgh Common – Fen
Large area of land at Guist north of river - Unimproved meadow; reed-bed, some scrub and alder carr
Turf Common – Unimproved meadow; some scrub and alder carr
Land at Billingford/North Elmham – Unimproved meadow
Land upstream of Swanton Morley adjacent to gravel pits – unimproved meadow
Land at Swanton Morley – Unimproved meadow
Land adjacent to river downstream of Lyng – Unimproved meadow
Land at Costessey – Unimproved meadow and fen
Land south of river & downstream of Costessey – Unimproved meadow and fen
Land north of river, near confluence with River Tat – Unimproved meadow and fen
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Table 3a Site-Specific definitions of Favourable Condition
To maintain the freshwater habitats and species on the River Wensum SSSI in favourable condition, with particular
CONSERVATION
reference to relevant specific designated interest features. Favourable condition is defined at this site in terms of the
OBJECTIVE FOR THIS
following site-specific standards:
HABITAT TYPE
Site-specific details of any geographical variation or limitations (where the favourable condition standards apply)
With regard to the Type III chalk river, it should also be noted that Norfolk has been overlain by deposits of boulder clays, sands and gravels, and as a
consequence, the upper river is not a ‘classic’ chalk river. River restoration should therefore aim to restore the river to a form characteristic of a chalk river in
Norfolk.
The headwater reaches tend to be fed by a combination of surface runoff and springs directly from the chalk. Within the catchment as a whole, headwater
reaches have been grossly modified, and as a consequence there are no recognisable winterbournes on the River Wensum. (N.B: Some of the tributaries arise
on sands and gravels and therefore there is a base-flow component to flow – i.e. not all the flow is direct run-off. Springs from the chalk tend to rise at the
junction of the floodplain and valley sides. These are intercepted by drainage ditches, but can contribute significantly to flows in the river). However, other
tributaries, and particularly those to the south of the catchment arise on more clay dominated soils, and here the flow is dominated by runoff, rather than baseflow from underlying aquifers.
Site-specific standards defining favourable condition
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Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
Use
for
CA?
Rivers
Habitat
functioning:
water flow
Data on gauged and
naturalised flows, flow
accretion methods, and the
Resource Assessment
Method (RAM) Framework
(including the Habitats
Directive Ecological River
Flow objectives).
Flow regime should be
characteristic of the river.
Levels of abstraction should
not exceed the generic
thresholds laid down for
moderately sensitive SSSI
rivers by national guidance
(but see Comments).
Maximum acceptable
percentage deviations from
daily naturalised flows
throughout the river:
<Qn50 flows – 20%
Qn50-95 – 15%
>Qn95 – 10-15%
The importance of River Flows - River flow affects a range of
habitat factors of critical importance to characteristic flora and
fauna, including current velocity, water depth, wetted area,
substrate quality, dissolved oxygen levels and water temperature.
The maintenance of both flushing flows and seasonal base flows,
based on natural hydrological processes, is vital. Detailed and
ecologically robust investigations of habitat-flow relationships
may indicate that a more or less stringent threshold may be
appropriate for a specified reach; – in these instances generic
targets may be over-ridden (guidance on this process is available).
Yes
There should be no obvious
problems with water
availability within the
monitoring unit.
Ecological flow criteria
already laid down for the
river (e.g. for passage of
migrating salmon) should
also be complied with.
Guidance on setting
conservation objectives
allows for the use of locally
derived flow targets where
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Naturalised flow is defined as the flow in the absence of
abstractions and discharges. The generic targets vary according to
the specific sensitivity of the reach type, with large lowland rivers
having somewhat lower sensitivity than headwater streams. Any
relaxation of generic targets on regulated SSSI rivers should relate
to the desirability and ecological sustainability of regulating
structures.
Broadland Rivers Catchment Abstraction Management
Strategy and the Environment Agency Review of Consents Water resource management within the Wensum SAC has been
guided by the Broadland Rivers Catchment Abstraction
Management Strategy (CAMS) and the Environment Agency
Review of Consents (RoC) under Regulation 50, the Conservation
(Natural Habitats &c.) Regulations 1994.
. Through these processes, it has been concluded that the upper
reaches of the river are over-licensed, and that the historic usage
has not exceeded the flow targets for the river. The upper reaches
of the river are therefore regarded as being ‘at risk’
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
there can be shown to be
more ecologically relevant
than generic flow targets, as
long as they are based on
Robust Hydroecological
Investigations covering all
potential mechanisms of
abstraction impact on all
flow-sensitive components
of the biological
community.
However, the RoC has concluded that downstream of the
Costessey Public Water Supply abstraction, the river is overabstracted and that sustainability changes are required in order that
the impacts of over-abstraction are addressed. The impact of
Public Water Supply abstraction within the Wensum catchment
has been the subject of an AMP4 investigation, and a full Options
Appraisal as to how this will be addressed during the AMP5 and
AMP6 periods is due to be completed in 2012.
Natural England have
recently produced a
Research Report on the
setting of flow targets for
SSSI rivers. This process
will summarise the evidence
base, revise generic flow
targets where necessary, and
generate more detailed
guidance on what
constitutes robust hydroecological investigations.
This report can be viewed
at:
http://naturalengland.etrader
stores.com/NaturalEnglandS
hop/NERR035
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To assist in the process of managing the impacts of low flows
within the Wensum catchment, an abstraction licensing policy has
been agreed between Natural England and the Environment
Agency, to provide clear criteria as to how license renewals and
new applications for water should be determined within the
Wensum catchment as a whole.
Use
for
CA?
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
Use
for
CA?
Rivers
Habitat
functioning:
water flow
Field observations
Springs in aquifer-fed rivers
should be maintained.
The importance of maintaining flow in headwater reaches Headwater sections are particularly vulnerable to abstraction, and
downstream migration of perennial heads, other than in drought
conditions, is a sign of unfavourable condition.
Yes
It should be noted that due to the depth of boulder-clay, sands and
gravels that overlie the chalk, and the modification to channel
form, headwater reaches, do not support recognisable
winterbourne habitats as is the case on ‘classic’ chalk rivers.
Headwater reaches are dependent on a combination of runoff and
base-flow and the proportion of these will depend upon the depth
of the overlying deposits and their permeability to groundwater.
Water chemistry is therefore influenced by the properties of the
soil type overlying the chalk .
Rivers
Habitat
functioning:
water quality
(General
assessments)
EA standard monitoring
protocols
Biological GQA Class ‘A’
for all reaches of the river
Biological GQA - A wide range of water quality parameters can
affect the status of interest features, but standard biological
monitoring techniques provide a reasonably integrated picture in
relation to many parameters. The Biological Module of the
Environment Agency’s General Quality Assessment scheme is
based on assessment of the macro-invertebrate community.
All classified reaches within the site should comply with the
targets given.
The generic biological target based on macro-invertebrates is
intended to be a catch-all, as invertebrates reflect most pollutant
impacts. However, all EQSs should be complied with to ensure
that the site is managed to prevent pollution impacts.
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Yes
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
Use
for
CA?
It is important that EA monitoring continues so as to maintain data
sets over an extended timescale.
Pesticides - Pesticide Bulletins provided by the Voluntary
Initiative and ADAS for the England Catchment Sensitive
Farming Delivery Initiative pesticide priority Anglian Region
catchments indicate that in the Wensum catchment, the pesticide
with elevated levels are The incidence of different pesticides are
a concern to Anglian Water Services Ltd, as much of the Public
Water Supply for Norwich is derived from a surface water
abstraction at Costessey. The Voluntary Initiative and England
Catchment Sensitive Farming Delivery Initiative seek to work
with land managers so as to reduce the risk of pesticide pollution
of water courses.
Rivers
Habitat
functioning:
water quality
(General
assessments)
EA standard monitoring
protocols
Chemical GQA Class ‘A’
for all reaches of the river
Chemical GQA - The chemical module of the GQA scheme sets
standards for dissolved oxygen, biochemical oxygen demand and
total ammonia. It therefore covers a number of water quality
parameters that commonly cause problems within river systems.
Where modelling has been undertaken, the river should comply
with the targets at all points along its length except within effluent
mixing zones of acceptable size.
Yes
It is important that EA monitoring continues so as to maintain data
sets over an extended timescale.
Rivers
Habitat
functioning:
water quality
EA monitoring
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Final 16 03 11 Format Version 2.0
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Un-ionised ammonia
<0.021 mg L-1 .as a 95percentile
Unionised ammonia - The un-ionised form of ammonia is
highly toxic to freshwater fauna. This target is the same as the
EQS used by the EA. Where modelling has been undertaken, the
river should comply with the targets at all points along its length
Yes
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
Use
for
CA?
except within effluent mixing zones of acceptable size.
It is important that EA monitoring continues so as to maintain data
sets over an extended timescale.
Rivers
Habitat
functioning:
water quality
EA monitoring.
Suspended solids
No unnaturally high loads
The impacts of suspended solids - Many characteristic species
of different river types are susceptible to elevated solids levels,
through reduced light availability (for photosynthesis), the
clogging of respiratory structures, impaired visibility or siltation
of coarse substrates. Lowland clay and alluvial river sections are
more depositional in character and resident biota are generally
more tolerant. Suspended solids measurements are also essential
to the estimation of particulate loads within the river network (in
combination with gauged flow data), to provide an indication of
the risk of siltation.
Targets should be set locally according to river type, catchment
characteristics and an analysis of available data. The highest value
that may be appropriate is 25 mg L-1 (annual mean), based on the
EC Freshwater Fish Directive. Considering prevailing
concentrations in most SSSI rivers, a more precautionary target of
no more than 10mg L-1 is likely to be suitable for most river
reaches.
Targets of considerably less than 10 mg L-1 may be appropriate
for some river sections where solids levels are currently very low
(such as chalk streams through the growing season) – an analysis
of available data is suggested to verify target selection.
Catchment Sensitive Farming - This initiative is addressing the
problems of diffuse pollution from agriculture. From an initial
Conservation Objectives: River Wensum
Final 16 03 11 Format Version 2.0
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Yes
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
Pilot Project, the initiative is now in its 6th year. With the WFD
target areas showing the River Wensum as a ‘failing’ river, further
emphasis will be put on reducing sediment and phosphate
problems within the catchment. Much of the targeting will be
through anecdotal, monitoring and sediment fingerprinting work.
The latter report is due out in the next few months and will
provide a cornerstone for future input from CSF. In the meantime,
targeting will be on specific sub catchments within the Wensum,
including Wendling Beck, River Tat, Lyng Forge and the
Blackwater.
Wensum Demonstration Test Catchment - However, it should
be noted that the Demonstration Test Catchments (DTC) project
includes the Wensum Catchment as one of four pilots. The
objectives of this project is to develop a large-scale research
platform to test measures for reducing diffuse pollution from
agriculture. It is considering the impacts and effects on both
ecosystems and sustainable production. It started in spring 2010
and it is anticipated that it will operate initially for five years.
The project is providing research on a national scale to help Defra
to policies on water quality in relation to agriculture, It will:
Conservation Objectives: River Wensum
Final 16 03 11 Format Version 2.0
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
Provide information on measures to improve the effectiveness
of Environmental Stewardship for resource protection.

Improve our confidence in schemes like Catchment Sensitive
Farming and help us to understand how to optimise them to
reduce diffuse pollution.
Use
for
CA?
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
One element of the work that is being undertaken is Sediment
Fingerprinting, to provide an apportionment as to proportion of
diffuse pollution that is derived from the wider catchment, and the
proportion that is derived from the erosion of road-side verges.
Once the results of this investigation are known, it can be
anticipated that further action will be required in relation to the
management of road infrastructure so as to reduce the input of
road runoff to the Wensum and its tributaries.
Diffuse Water Pollution Plans - It is recognised that diffuse
pollution is derived from a wide range of sources, and is conveyed
to the river through a complex network of pathways. Catchment
Sensitive Farming is focussed on liaison with the farming
community. However, in order to identify and address the full
range of sources, and pathways,, a Diffuse Water Pollution Plan
has been formulated for the Wensum Catchment.
The need for continuous monitoring - The achievement of
targets can only be truly assessed through continuous monitoring
of turbidity on the main river. Monthly sampling is appropriate
with regard to the evaluation of the impacts of turbidity in the
water column, as the concern in this instance is chronic exposure,
rather than the impact of transient events. However, exposure of
substrates to impacts of turbidity is strongly related to deposition
events linked to run-off events. This can be looked at via the
condition of the substrate itself, or via water column suspended
sediment concentrations, or both. For data on suspended sediment
concentrations to allow an evaluation of impacts in relation to
substrate condition, it is necessary to ensure that data is collected
in relation to sediment concentrations during high flow events,
and for this the most appropriate monitoring regime is the use of
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Use
for
CA?
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
Use
for
CA?
continuous turbidity monitoring or event-triggered auto-sampling.
In the case of classic chalk streams, continuous monitoring is not
deemed necessary. However, the River Wensum SAC is not a
classic chalk stream, as the chalk is overlain by varying depths of
gravels, sands, silts, crag and boulder clay and a monthly sampling
regime would not be sufficient to assess the impacts on substrates.
Monitoring of sediment yield - The monitoring of sediment
yields is desirable, as a means of characterising sediment delivery
problems within the catchment. However, this would require a
good understanding of the concentrations of solids during high
flows, and continuous turbidity monitoring would be required.
Rivers
Habitat
functioning:
water quality
EA monitoring
Total Reactive
Phosphorus - An annual
average phosphate
concentration of 0.04mg/l
from the upstream limits of
the SSSI to Sculthorpe;
0.06mg/l from Sculthorpe to
Taverham Bridge; and
0.1mg/l from Taverham
Bridge to the downstream
limit of the SSSI
The impacts of elevated levels of phosphorus - Elevated
phosphorus levels interfere with competitive interactions between
higher plant species and between higher plants and algae, leading
to dominance by attached forms of algae, deterioration of
vegetative habitat, and declines in abundance and/or diversity of
characteristic plant species (which may include lower plants such
as mosses and liverworts).
The respiration of artificially large growths of benthic or epiphytic
algae may generate large diurnal sags in dissolved oxygen in the
water column and/or substrate fish and invertebrate species.
Excessive benthic algal growth can also enhance the trapping of
fine sediments within riverine gravels, enhancing siltation and
exacerbating poor substrate conditions.
The river should comply with the targets at all points along its
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Yes
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
length except within effluent mixing zones of acceptable size.
With regard to phosphate pollution, consideration should also be
given to the presence and management of adjacent water bodies,
and water bodies that are directly linked with the river.
Phosphate modelling - It should be noted that the PSYCHIC
Model has been used to understand phosphate pollution within the
catchment in association with the Catchment Sensitive Farming
Delivery Initiative; and that the SIMCAT Model has been used by
the Environment Agency in relation to the RoC for the
apportionment of phosphate input from point source pollution and
diffuse pollution. The management of diffuse pollution is
discussed above in relation to turbidity, but phosphates are bound
to the particulates in suspension.
The Sediment Fingerprinting Investigation carried out as part of
the Wensum Demonstration Test Catchment Project will provide
further insights as to catchment wide sources of phosphate
pollution, and will provide opportunities for targeting of
resources.
Point Source Pollution - It should be noted that phosphate
stripping was implemented at the Dereham STWs and Fakenham
STWs during the AMP3 period. The conclusion of the RoC was
that point source delivery to the river was still in excess of Natural
England targets and as a consequence, a further programme of
phosphate stripping has been included in the AMP5 programme.
Phosphate stripping will be implemented at:

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Sculthorpe STW - Modify - emission limit of 1 mg/1OP
Use
for
CA?
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments






Use
for
CA?
East Rudham STW - Modify - emission limit of 2.5mg/1OP
Weasenahm St Peter STW - Modify - descriptive consent
changed to volumetric - 32m3/dDWF
Foulsham STW - Modify - emission limit of 1mg/1OP
North Elmham STW - Modify - emission limit of 1mg / 1OP
Swanton Morley STW - Affirm or Modify (emission limit of
2.5mg/1OP
Reepham STW Modify - emission limit of 2 or 1mg/1OP
Phosphate input from shallow lakes - Impacts may derive from
the recycling of nutrients in shallow lakes. Waters discharged into
the river from water bodies where artificial fisheries management
is practiced may also be of concern and policies in relation to the
densities of stocked fish have been included in the draft ‘Fish
Stocking Strategy for the River Wensum SSSI & SAC, and Stillwaters in the Wensum Catchment’ in order to address this.
Rivers
Habitat
structure:
substrate
Field observations
Siltation
No excessive siltation.
Channels should contain
characteristic levels of fine
sediment for the river type.
The impacts of siltation - Siltation levels vary naturally,
depending upon the reach type and hydrodynamic regime. Most
sites should have a variety of channel substrates. Localised
accumulations of silt on the inside of bends or in back channels do
not necessarily indicate a problem. However, widespread siltation
of riverine sediments, caused by high particulate loads and / or
reduced scour within the channel (due to artificial channel
modifications such as weirs), is a major threat to the characteristic
river habitat and associated flora and fauna.
Many characteristic species of fish, invertebrates and even plants
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Yes
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
are susceptible to siltation at some stage in their life-cycle.
Mechanisms of impact can relate to reduced interstitial spaces in
coarse substrates, reduce water flow-through the substrate leading
to poor quality of interstitial waters, and reduced sediment surface
‘roughness’ that eliminates refugia for animals with epibenthic
habitats and prevents plant seeds and fragments from lodging in
the substrate and taking root.
For river types characterised by extensive Ranunculus beds, there
should be a predominance of ‘clean’ gravels, pebbles and cobbles,
with relatively low cover by silt-dominated substrates. Maximum
fines content should not be too great to prevent establishment of
new plants. Fines are defined as particles< 0.83 mm.
Sources of silt include run-off from agricultural land, sewage and
industrial discharges. A fluvial audit is recommended where
specific problems have been identified, e.g. where there is a
perceived risk of damage occurring or where species characteristic
of the habitat are already believed to be in decline.
Fluvial audit is not a monitoring tool but can deliver an
understanding of geomorphological problems unattainable by any
other method, and help to discriminate between problems of
sediment delivery and problems of channel structure.
Geomorphological Appraisal of the River Wensum SAC - A
Geomorphological Appraisal of the River Wensum SAC has been
carried out, consisting of a detailed fluvial audit, geodynamic
assessments and multi-criteria analysis. This concluded that the
high levels of silt in the river are derived from run-off from
agricultural land, particularly in the headwater reaches, rather than
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Use
for
CA?
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
Use
for
CA?
erosion from the river banks or river bed. It also concluded that
the road network was a significant factor with regard to the
transportation of sediment from source to receptor.
Rivers
Habitat
structure:
channel and
banks
Assess river morphology
using RHS (see text and
Appendices 4 and 5 of the
monitoring protocol for
details).
In addition, for planform:
map data, aerial survey data,
historical records and local
knowledge.
Channel form
Channel form should be
generally characteristic of
river type, with
predominantly unmodified
planform and profile.
For planform the target is a
score for the assessment
unit of at least 3 (see
Appendix 4 of the
monitoring protocol).
For naturalness of the
profile using transect data
the target is a score for the
assessment unit of 4 or 5
(see Appendix 5 of the
monitoring protocol).
No RHS site to have any of
the eight categories of bank
profile modification
(Section I in RHS 2003
form) recorded as
‘extensive’.
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The significant of channel form and function - The river
should support all of the habitat features necessary for
characteristic flora and fauna to thrive, in characteristic
proportions. Widening or deepening of channels, and extensive
artificial reinforcement of banks, are indicators of unfavourable
condition. Headwater sections are particularly vulnerable to
reprofiling.
Watercourses with a high degree of naturalness will be governed
by dynamic processes which result in a variety of physical habitat
features, including a range of substrate types, variations in flow,
channel width and depth, in-channel and side-channel
sedimentation features, erosion features and both in-channel and
bank-side vegetation cover.
The new version of Habitat Modification Score (HMS) enables a
more sophisticated assessment to be made, based on the nature of
modifications to a river and their estimated persistence. Details are
being finalised by the Environment Agency, but a guideline target
might be 90% or more of condition monitoring sites should fall
within the semi-natural HMS class 1, with the remainder
predominantly unmodified (class 2).
Geomorphological Appraisal of the River Wensum SAC - In
order to understand the form and function of the river, English
Nature worked closely with the Environment Agency and King’s
Lynne Consortium of IDBs with regard to the development of the
Yes
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
Geomorphological Appraisal of the River Wensum SAC. This
concluded that:


The gravel bed is a relic from higher energy flows during
periglacial climatic conditions and once removed cannot be
reformed under current climatic conditions.
Over-deepening, over-widening and the impoundments
upstream of mills have had a profound impact on
geomorphological process.
The Geomorphological Appraisal presents restoration options on a
reach by reach basis, but does not give detailed plans for
implementation of river restoration. The Geomorphological
Appraisal can be viewed at:
http://naturalengland.etraderstores.com/NaturalEnglandShop/R68
5
River Wensum Restoration Strategy - In order to take the
conclusion of the Geomorphological Appraisal forward, Natural
England worked closely with the Environment Agency and
Norfolk Rivers IDB with regard to the formulation of the River
Wensum Restoration Strategy. This presented an unconstrained
geomorphological vision as to how the River Wensum might be
restored, with detailed consideration of options relating to river
restoration and the structures on the river. The Strategy was
formulated at the same time as the review of the River Wensum
Water Level Management Plan, and these were drawn up so as to
dovetail with each other. It should be noted that the Strategy has
been drawn up as a guide to owners, occupiers, and statutory
Conservation Objectives: River Wensum
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for
CA?
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
undertakers with regard to the river restoration options most
appropriate to given reaches of river. The River Wensum
Restoration Strategy can be viewed at:
http://naturalengland.etraderstores.com/NaturalEnglandShop/NEC
R010
The work of the River Wensum Restoration Working Group Once formally signed off by the Environment Agency and Natural
England, implementation of the recommendations of the Strategy
were taken forward through the River Wensum Restoration
Working Group. Stakeholder Drop-In Meetings were arranged so
as to give the opportunity for all stakeholder groups to comment
on the strategy, and their aspirations for individual river reaches.
Through consideration of constraints, and aspirations of
stakeholders, detailed feasibility studies for all Main River reaches
are under development and can be viewed on the Environment
Agency website at:
http://www.environmentagency.gov.uk/homeandleisure/wildlife/114676.aspx
In addition, Targeted Maintenance Protocol and a Mill Operating
Protocol are being developed in order to ensure that these
activities are compatible, and where possible contribute to river
restoration objectives.
A number of successful river restoration projects have been
undertaken, which have been based upon the Feasibility Studies,
and further schemes are anticipated in the future.
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Use
for
CA?
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
Use
for
CA?
Rivers
Habitat
structure:
channel and
banks
For bank vegetation: a
simplified Phase I habitat
survey, carried out at 10
RHS transect locations or as
part of the sweep-up survey
(see Appendix 6 of the
monitoring protocol).
Bank and riparian zone
vegetation Bank and
riparian zone vegetation
structure should be nearnatural.
Note: The protocol in Appendices 6 and 7 used to assess bank
and riparian zone naturalness incorporates a modification due to
negative indicator species. Targets may need to be adjusted to
account for unmodifiable problems with vegetation. Problems
with vegetation can be addressed through management agreements
and Environmental Stewardship.
Yes
In-channel vegetation of SSSI/SAC rivers should be dominated by
characteristic species. Species composition and abundance should
be assessed using data from two 500 m stretches in each
assessment unit where possible.
Yes
For the riparian zone: RHS
transect data, assessed using
the protocol in Appendix 7
of the monitoring
protocol.
Rivers
Plant
community:
species
composition
and abundance
Survey the macrophytes of
representative stretches at
intervals of ca. 5 km , using
the method of Holmes
(1983) and a standard
check-list of macrophyte
species (see Appendix 2 of
the protocol).
Evaluate the community
against the target
community in the constancy
tables (Appendix 8 of the
protocol).
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For bank vegetation the
target is a mean score for
the assessment unit of 4 or
5.
For riparian zone vegetation
the target is a mean score
for the assessment unit of 4
or 5.
(i) Species Composition
The following should all
occur: at least 60% of
species with abundance V
or IV in the constancy table
for Type 11/Group A2
rivers should be present,
AND at least 25% of
species with abundance III
should be present.
(ii) Loss of Species
60% of species with cover
>1 in the initial baseline
survey should be at least
When assessing targets (ii) and (iii), the data from all macrophyte
survey sites in the assessment unit should be pooled and compared
against pooled baseline data/reference condition.
Cover values are expressed using a simplified DAFOR 3-point
scale. Where necessary, 5-point scale data converts into the 3point scale as follows: 5/4 = 3, 3 = 2, 2/1 = 1. Any sections
classified as Type IV are considered to be in unfavourable
condition.
Criteria
feature
Rivers
Attribute
Plant
community:
reproduction
Measure
Site-specific Targets
Comments
Record measures of species
composition and abundance
on the form in Appendix 9
of the protocol.
present and all species
recorded as dominant in the
initial baseline survey
should still be present.
Comparisons in (ii) and (iii) should be made with the initial
baseline survey/reference condition, not with survey data from the
previous monitoring cycle.
Alien species, filamentous
green algae (including
Cladophora, Vaucheria, and
Enteromorpha) and other
species indicative of
eutrophication are not
included in these targets and
are dealt with in separate
targets below.
(iii) Abundant Species
At least 25-35% of species
recorded as dominant in the
initial baseline survey
should still recorded as
dominant.
Field observations during
macrophyte survey.
A sufficient proportion of
all aquatic macrophytes
should be allowed to
reproduce in suitable
habitat, unaffected by river
management practices.
Use
for
CA?
The text under Targets summarises the suggested specific targets
for each of the criteria. These should be used to guide those
undertaking the condition assessment, but because of local
variation it cannot be expected that all elements will ‘pass’. This
is especially likely where sites are on the edge of their ‘type’ – e.g.
upper reaches of chalk streams that may be occasionally dry or
upstream sites where downstream seeding of species may be
limited. Loss or gain of species can be indicative of either
deterioration or improvement, so assessment needs to take account
of the reasons for change.
This only applies where control measures such as weed cutting are
implemented (usually in Ranunculus rivers, but can apply in other
vegetation types).
Yes
Flowering outside the normal period and weed cutting or other
activities that do not leave patches of plants to flower and set seed
are indicators of unfavourable condition.
25% of the total habitat / macrophyte population should be left
uncut for the full duration of the growing season.
Rivers
Negative
indicators:
native species
Survey the macrophytes of
representative stretches at
intervals of ca. 5 km, using
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Targets are set to register
high or increasing cover as
unfavourable.
Care should be taken with the setting of these targets as thresholds
may vary considerably by site and conservation goals.
Yes
Criteria
feature
Attribute
Measure
Site-specific Targets
the method of
Holmes(1983) and a
standard check-list of
macrophyte species (see
Appendix 2 of the protocol).
For blanketweed,
epiphytic or other algae,
Potamogeton pectinatus or
Zannichellia palustris:
Cover values over 25%
should be considered
unfavourable, and should
trigger further investigation.
Cover values should not
increase significantly from
an established baseline.
ii) For taxa with STRs as
follows: For taxa with STR
values of 1 or 2, cover
values over 25% should be
considered unfavourable,
but should trigger further
investigation.
Cover values should not
increase significantly from
an established baseline.
Rivers
Negative
indicators:
alien/
introduced
species
For aquatic and marginal
macrophytes the presence of
alien species listed in
Appendix 10 of the protocol
should be noted during the
macrophyte survey and the
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No impact on native biota
from alien or introduced
species
Aquatic and marginal
macrophytes
The mean SERCON score
Comments
Use
for
CA?
Taxa typically associated with enrichment are considered negative
indicators of favourable condition. The species will vary
depending on the River Community Type. Species that are
characteristic of enrichment, or have atypically low Species
Trophic Ranks (STRs) in the Mean Trophic Rank (MTR) system
(Holmes et al., 1999) and that are recorded as dominant (3), are
used as indicators. Note: in using MTR, each species is allocated a
score dependent on its tolerance to eutrophication; this system
cannot be used to assess acidification.
Expert judgement will be important in assessing the ecological
significance of cover values of these species. At some sites, it may
be appropriate to set more stringent targets. Occasionally
thresholds may need to be raised, according to wider conservation
objectives.
Alien species are assessed within the Negative indicators: alien/
introduced species attribute instead.
The impact of Non-native species - Non-native species
constitute a major threat to many river systems. Note: ‘Introduced
species’ include species that are native to the UK but outside of
their natural range.
The SERCON scoring system for naturalness of aquatic and
marginal macrophytes is used to assess alien plant species.
Yes
Criteria
feature
Attribute
Measure
Site-specific Targets
scoring system for
naturalness applied.
for naturalness (derived
from individual survey
sites) should be 4 or 5 (see
Appendix 10 of the
protocol).
For other organisms contact
external organisations (e.g.
EA) for local reports on
alien or introduced species.
Other organisms
No alien/introduced species
present at levels likely to be
detrimental to the
characteristic biological
community.
Comments
Note: This protocol applies to negative indicator species of the
channel and channel margins. Negative indicator species found on
banks and the riparian zone are assessed as part of the naturalness
of banks and naturalness of riparian zone assessment and form
part of the CSM structure attribute
For other organisms, expert judgement will be needed to
determine whether there is sufficient evidence to generate an
unfavourable condition assessment. For example, for signal
crayfish, presence alone would constitute unfavourable condition.
Other species, such as barbel, can be tolerated at low levels;
higher levels would constitute unfavourable condition.
Invasive aliens that should be controlled where they occur on the
River Wensum include signal crayfish, Himalayan balsam
(Impatiens glandulifera) and giant hogweed (Heracleum
mantegazzianum).
The Norfolk None Native Species Initiative - The Norfolk
None Native Invasive Species Initiative (hosted by the Norfolk
BAP Partnership) is in its second of three years of funding. With
regard to Himalayan balsam, it has undertaken survey work to
confirm its distribution, and based upon this has developed a
Strategy Plan for its control. Control measures will be instigated
in 2011,and will be focussed upon the eradication of outlying
populations. The Initiative has also carried out control measures
on giant hogweed at Fakenham. However, a coordinated approach
to control of invasive aliens in the Wensum Valley, over the
longer term is uncertain.
Signal crayfish - Signal crayfish have been found in the
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Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
Use
for
CA?
Reepham Stream and have entered the Wensum by way of this
tributary. They have also been found at a number of sites in the
vicinity of Swanton Morley.
Azola filiculoides can become apparent on the river’s edge in
autumn but does not appear to pose a threat to aquatic
communities. However, Crassula helmsii has been found on sites
adjacent to the river and may pose a threat for terrestrial site units,
and for wetlands on the floodplain as a whole.
Rivers
Negative
indicators:
Fish
introductions
Assessment of stocking
consents in relation to
guidance on acceptable
stocking levels.
Fish introductions should
not interfere with the ability
of the river to support selfsustaining and healthy
populations of characteristic
species.
The impact of fish introductions - Many characteristic species
can be affected by fish introductions, through increased predation,
competition or genetic introgression, or through disease transfer.
Guidance is being generated on the levels of stocking deemed to
be ecologically acceptable within SSSIs.
The draft Fish Stocking Strategy for the River Wensum SSSI
& SAC, and Still-waters in the Wensum Catchment - This
draft strategy was drawn up by the Environment Agency, in
consultation with Natural England to ensure that fish stocking is in
line with the conservation objectives of the site. This gives
guidance on such issues as bio-security of flood-plain lakes,
biomass per hectare post stocking of floodplain lakes, and the
policies relating to the stocking of native and none-native species
in the river. Although, there has been subsequent national
guidance in relation to the stocking of certain species (e.g. the
stocking of trout in SAC rivers), this document will need to be a
foundation stone for the development of the Environment
Agency’s
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Yes
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
Live Fish Movement Scheme - Fish are typically moved between
inland waters for stocking purposes, and this includes the stocking
of floodplain water bodies, and the river its self. Currently the
movement of fish is regulated through ‘Section 30 consents’
(referring to Section 30 of the Salmon and Freshwater Fisheries
Act 1975). The consenting process is overseen by the
Environment Agency and applies to the movement of any fish or
crayfish between freshwaters in England and Wales. If the fish to
be moved are on a specified non-native list this activity also
requires an ILFA (Import of Live Fish Act) licence.
During 2011, this will be replaced by the EA Live Fish Movement
Scheme, where fish will be stocked in a permitted fishery in
accordance with a Site Permit, agreed in advance with the
Environment Agency. The formulation of individual Site Permits
will need to be drawn up so that there is no ‘in combination’
impacts on the river system.
Management of barbel fisheries on the Wensum - Natural
England has a general desire to conserve natural fish communities,
particularly within SSSIs, so in general we would not be in favour
of any intention to introduce species that are not part of the
historical/resident community of a site. However, barbel have
been legally introduced to the river, and have been present in the
river at low densities since the 50’s, and no adverse impact on
integrity of the site has been observed. It is for this reason that the
Citation for the River Wensum SSSI makes mention of the barbel
as part of the site context.
The Joint Nature Conservancy Council Common Standards
Monitoring Guidance for Rivers, Version March 2005 ISSN
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Use
for
CA?
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
Use
for
CA?
1743-8160 (online) states in a section relating to invasive, and
alien species that, “Species, such as barbel, can be tolerated at low
levels; higher levels would constitute unfavourable condition”. It
is for this reason that management of the barbell fishery at Lyng
and Norwich can be tolerated, provided that the density of barbel
remain at low levels. Higher levels would constitute unfavourable
condition.”
While barbel stocking is not desirable, we have been able to
conclude that there would be no adverse impact on integrity as a
result of proposals for low levels of barbel stocking. Through
detailed investigation, Environment Agency surveys have
concluded that barbel recruitment is at a very low level. We can
therefore be confident that barbel populations will not increase out
of hand if further stockings were proposed and carried out,
providing that these further stockings were limited in terms of
numbers. Problems arise where angling quarry species are
introduced at a level above the carrying capacity of a river reach,
and this results in significant ecological imbalances within the
system, whether that species is native to the river or not.
Rivers
Negative
indicators:
In-stream
barriers
Strategic assessment of
barriers affecting the
characteristic species of the
SSSI.
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No artificial barriers
significantly impairing
characteristic migratory
species from essential lifecycle movements.
The impact of barriers - Barriers may take the form of weirs,
barrages or intakes/off-takes that entrain characteristic species.
Species may be anadromous (e.g. salmon), catadromous (e.g. eels)
or migrate over relatively short distances within the river system
(e.g. bullhead, brook lamprey and invertebrates without flying life
stages). A range of data sources may be used and brought together
to make this assessment. Specific studies may be required in
relation to some barriers where impacts are uncertain and remedial
costs are potentially high.
Yes
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
Mill structures on the Wensum - The series of mill structures
on the Wensum has implications with regard to the migration of
fish species. The first mill structure to obstruct fish is at New
Mills, which marks the tidal limit of the river. From the
downstream limit of the SSSI there are a further 14 water control
structures. The River Restoration Feasibility Studies consider
opportunities and constraints and identify the most appropriate
option for the retention, modification, replacement or removal of
mill structures, or alternatively, bypasses to structures.
Implementation of the appropriate options for each mill will
increase the accessibility of the river to migratory fish.
Low Head Hydro Schemes - LHHP can have a fundamental
effect on the physical character of a river, altering physical habitat
provision for characteristic flora and fauna. There are three main
effects of LHHP generation on river habitat:

alterations to the geomorphology and hydraulics of the river
channel, through the impounding structures used to create a
head of water;

alterations to flow regime associated with abstraction of water
out of the channel;

Interruption of biological connectivity, including the passage
of fish and invertebrates.
Decision-making should be based on the following issues, which
should be considered sequentially. Where a proposal is found to
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Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
be unacceptable on the basis of the first issue, there is no need to
consider subsequent issues.

Impacts of impounding structures - The impact of
impounding structures on physical habitat provision should
always be evaluated, irrespective of whether the proposal is
based on an existing structure or a new structure. Decisions
should be consistent with judgements about the removability
of existing structures made through the development of
strategic restoration plans for river SSSIs. Where there are no
immovable constraints to removing a structure, the objective
should be for structure removal and any LHHP proposal
connected with it should therefore not be authorised.
If a decision is made through the restoration planning process
that a certain structure cannot realistically be removed, or can
only be modified to an extent that would not preclude a
hydropower scheme, then river restoration should not be seen
as a hindrance to authorisation. However, we would still need
to be satisfied that any scheme would not derogate flow
targets for the river or unduly constrain biological movement.
Proposals involving new impoundments on river SSSIs
should not be authorised, due to effects on natural
geomorphological processes and consequent impacts on
habitat provision for biological communities characteristic of
the river.

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Impacts of flow depletion Evaluation of proposals on river
SSSIs should be made on the same basis as any other
Use
for
CA?
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
abstraction proposal. Generic flow targets are defined by the
site’s conservation objectives, based on acceptable deviations
from daily naturalised flows throughout the year. As with all
non-consumptive abstractions, small non-compliances over a
short stretch of river would not be deemed inconsistent with
the Favourable condition of the site, but such impacts must be
considered on a cumulative basis considering all abstractions
generating a deviation from naturalised daily flows. No
quantitative targets are defined for acceptable spatial extent of
non-compliances, but such impacts should be viewed at a
river reach (ENSIS reporting unit) not whole-site level. As a
guide, small cumulative non-compliances over more than a
few percent (<5%) of reach length are unlikely to be
considered consistent with Favourable condition.

Impacts on biological connectivity - Existing impacts on
biological connectivity within river SSSIs are being addressed
through the development of strategic plans for physical
habitat restoration. Where the objective for an existing
structure is for removal, any LHHP proposal based on that
structure should already have been rejected (see above).
Where a structure is accepted as immovable in the context of
strategic restoration planning, and an acceptable flow regime
consistent with conservation objectives has been agreed, then
residual impacts on biological connectivity should be
considered.
Any in-channel structure on which a proposal is based should
be made passable to the characteristic biological community,
to avoid both short and long-term (climate-related) impacts
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Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
associated with lack of access to upstream river sections.
Rivers
Indicators of
local
distinctiveness
As appropriate. (See
appendix 11 for riverine
Red List and Nationally
scarce plant and invertebrate
species.)
Maintain distinctive
elements (e.g. rare species,
habitat features) at current
extent/levels and/or in
current locations
This attribute is intended to cover any site-specific aspects of this
habitat feature (forming part of the reason for notification) which
are not covered adequately by the previous attributes, or by
separate guidance (e.g. for notified species features).
For ‘notable’ species (e.g. Red List and Nationally scarce plants or
species rare in rivers) it is not intended to set a target for detailed
species monitoring, rather to provide a rapid indication of
presence/absence and/or approximate extent, allowing for natural
fluctuations in population size. For ‘notable’ features (e.g. shingle
bars) the same approach applies.
Over 100 species of aquatic and emergent vascular plants have
been recorded on the River Wensum. Characteristic chalk river
species of the upper reaches of the river include Berula erecta,
Ranunculus pencillatus, Groenlandia densa, and the nationally
rare Callitriche truncate.
The middle and lower reaches are characterised by rich lowland
plant communities and support Nuphar lutea, Butomus
umbellatus, Potamogeton pectinatus, Potamogeton perfoliatus,
and Sagittaria sagittifolia.
Other species with widespread distribution include Ceratophyllum
demersum, Myriophyllum spicatum, Ranunculus circinatus,
Sparganium erectum, Scirpus lacustris, Zannichellia palustris and
the nationally scarce Oenanthe fluviatilis.
Population attributes of designated species
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for
CA?
Criteria
feature
Attribute
White-clawed
crayfish
(Austropotam
obius pallipes)
White-clawed
crayfish
(Austropotam
obius pallipes)
Measure
Site-specific Targets
Comments
Use
for
CA?
Population
densities
These should not differ
significantly from those
expected for the site under
conditions of high physical
and chemical quality, and in
any case should not drop
below recent levels.
Insufficient data are available on typical densities in different river
types to set reliable targets. Monitoring units would be expected to
average at least “moderate” abundance according to monitoring
category protocols. However, crayfish densities may be lower than
this on some units/rivers due to natural factors and it would be
wrong to assume such lower densities necessarily constitute
unfavourable condition. Determination of unfavourable condition
should only be made where low densities are known to be related
to an impact of some kind, or where historical survey data suggest
that higher densities should be present. Regular monitoring on
different river types using the standard protocol will provide data
on which targets can be produced in the future.
No
Population
health
Absence of individuals
infected with crayfish
plague
Crayfish plague can be introduced by the entry of non-native
crayfish species into a site, but also by a variety of other routes,
including contaminated equipment (nets, boots, etc.) and stocked
fish from infected waters1. Outbreaks of crayfish plague typically
result in 100% mortalities, unless there are isolated headwaters
with crayfish in the catchment. This target requires that the utmost
care be taken in terms of fish stocking and general
surveying/monitoring to ensure that plague vectors are not
introduced. Disinfection or thorough drying of equipment (or
perhaps dedicated equipment for use only in native crayfish rivers)
and stocking fish from uninfected waters are vital elements.
Nationally agreed EN/EA policy on stocking fish into crayfish
SSSIs/SACs should prevent stocking from catchments containing
signal crayfish or known to have experienced plague. However,
given that SAFFA S. 30 does not apply to fish farms, fish from
high risk farms could conceivably be introduced, via apparently
risk-free farms. EA/EN are addressing this issue at present.
No
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Criteria
feature
Attribute
White-clawed
crayfish
(Austropotam
obius pallipes)
Measure
Site-specific Targets
Comments
Use
for
CA?
Population
health
Thelohaniasis (Porcelain
Disease) should not affect
>10% population.
This disease rarely causes mass mortalities and may be present in
a population at low levels without apparent harm. However, a
prevalence exceeding 10% is of concern.
No
White-clawed
crayfish
(Austropotam
obius pallipes)
*Negative
indicators
Non-native crayfish should
be absent. If present,
measures should be taken to
control their numbers.
Once non-native crayfish species are established in a water body,
native populations are usually eliminated quite rapidly, if not by
competition and predation then by crayfish plague. If already
present in an SAC, measures should be taken to control the spread
of alien species and, if possible, reduce their numbers.
No
Brook
lamprey
(lampetra
planeri)
Distribution
within
catchment
Lampreys should be present
at not less than 2/3 of sites
surveyed.
Distribution in the catchment should be appropriate to the natural
geomorphology. Any accessible silt beds should be expected to
contain ammocoetes of Lampetra spp, although in practice some
beds are likely to be naturally unoccupied (e.g. due to washout).
Any silt beds adjacent to or downstream of known Petromyzon
spawning sites should contain Petromyzon ammocoetes. If the
distribution of Petromyzon in the catchment is unknown, surveys
of spawning sites should be carried out in June-July.
No
As a minimum, there should
be no reduction in the
distribution of ammocoetes
within the catchment.
Where barriers to migration or pollution issues are thought to be a
problem, the population should be classed as being in
unfavourable condition and targets for an appropriate increase
should be set.
Brook
lamprey
(Lampetra
planeri)
Age structure
For samples of 50 or less, at
least two distinct size
classes should normally be
present.
If more than 50 ammocoetes
are collected, at least three
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Lamprey ammocoetes grow at a reasonably steady rate and
distinct size classes are usually apparent. Ammocoetes typically
range from 10 – 150 mm, corresponding to up to six year classes.
The largest ammocoetes are usually brook lampreys (river
lampreys metamorphose at about 100 – 120 mm), while the
smallest individuals are likely to be young-of-year sea lampreys,
since this species spawns later in the year than Lampetra.
No
Criteria
feature
Attribute
Measure
Site-specific Targets
size classes should be
present.
Comments
Use
for
CA?
The full range of age classes of ammocoete larvae, from 0+ up to
metamorphosis should be present. However, sampling error may
make these difficult to discern unless large samples are taken. If
more than 100 lampreys are collected, at least three size classes
should be present.
Brook
lamprey
Lampetra
planeri)
Ammocoete
density
Chalk streams >5 m-2
Overall catchment mean:
>5m-2
Density targets need to relate to river type (at least in broad terms),
since production varies considerably. Chalk streams are not as
productive as other systems because their low physical variability
and low energy means that large, deep silt beds suitable for
lampreys are rare. However, ammocoetes are still common in
marginal habitat, among macrophyte beds etc., though at lower
densities.
No
Bullhead
(Cottus gobio)
Adult
population
densities
There should be no
reduction in densities from
existing levels, and in any
case no less than 0.2 m-2 in
upland rivers (source
altitude >100m) and 0.5 m-2
in lowland rivers (source
altitude ≤100m).
Routine Environment Agency monitoring is not capable of
providing suitable data. A least-cost methodology for monitoring
this attribute has been developed by the LIFE in UK rivers project,
involving the sampling of representative reaches within an SAC.
No
Bullhead
(Cottus gobio)
Distribution
within SAC
Bullheads should be present
in all suitable reaches. As a
minimum, no decline in
distribution from current.
In the UK, bullhead are widespread in any flowing water at an
altitude of less than 300 m. Well oxygenated water over a gravel /
pebble / cobble substrate is preferred (and is essential for
successful reproduction). Riffles are a favoured microhabitat. Very
sluggish water with a clay / silt substrate or cold, steep-gradient
upland sections with numerous cascades and boulder / bedrock
substrate should be viewed as sub-optimal.
No
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Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
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for
CA?
Bullheads can occur in very small channels (<1 m wide) where
they may be the only fish species present.
Bullhead are very poor colonists, to the extent that catchments
may contain many individual subpopulations. It is not feasible to
assess each of these individually, but it is very important that there
is no loss of these populations, and that access routes between
them are not impeded (see environmental disturbance notes
below).
Bullhead
(Cottus gobio)
Reproduction/
Age Structure
Young-of-year fish should
occur at densities at least
equal to adults.
Young-of-year fish should be easily identifiable using lengthfrequency analysis. In September they are typically less than 30
mm long.
Young-of-year are often much more numerous than adults, so the
current target is rather conservative (to allow for natural variation
in recruitment and habitat type). A ratio of 3 or 4:1 for Y-O-Y:
adults is not unusual. It may be necessary to refine this target at a
site-specific level.
Audit Trail
Rationale for limiting standards to specified parts of the site
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No
Rationale for site-specific targets (including any variations from generic guidance)
Whilst not forming part of formal condition assessment, the following detailed information on the habitat requirements of individual designated species may be useful for the
management of the site and should be considered when judging the detailed effects of activities.
White-clawed crayfish (Austropotamobius pallipes)
Natural channel morphology provides a diversity of refuge and feeding opportunities. The proximity of different refuges facilitates foraging and the movement of individuals
to different habitats with age. Operations that widen, deepen and/or straighten the channel reduce variations in habitat. New operations that would have this impact are not
acceptable within an SAC, whilst restoration may be needed in some reaches. Extent of cobbles/ boulders: where they occur naturally, cobbles and boulders are used
extensively by crayfish as refuge. Engineering works can result in the loss of large material – any works should at least replace the pre-works availability of such refuges.
Extent of large woody debris: where they are present, fallen branches and trunks are used extensively by crayfish as refuge. Woody debris is typically removed during
maintenance operations, but it is important to retain as much as possible, particularly where other forms of refuge are in short supply. Density of bank-side refuges: these
provide important refuges and are often lost during engineering operations. Any works should at least replace the pre-works availability of refuges. Extent of submerged and
marginal vegetation: submerged higher plants provide cover away from the banks, and also represent a valuable food source. Marginal emergents also provide important cover
and feeding opportunities. Vegetation management should be limited to no more than 50% of the channel width (submerged plants) and 50% of bank length (marginal fringe).
Extent of overhanging riparian vegetation: this should cover at least 10% of bank length throughout the year, distributed in patches along the margins, and considerably more
where other forms of refuge are in short supply. Extent of bank-side tree cover: overhanging trees provide valuable shade and food sources and, in addition, supply woody
debris to the river. Submerged tree-root systems provide important cover and refuges from flood flows.
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Brook lamprey (Lampetra fluviatilis)
The characteristic channel morphology provides the diversity of water depths, current velocities and substrate types necessary to fulfil the spawning, juvenile and migratory
requirements of the species. Lamprey species require a combination of coarse substrates for spawning and stable beds of fine sandy/silty material for larval development. The
close proximity of these habitats facilitates movement to new preferred habitats with age. Operations that widen, deepen and/or straighten the channel reduce variations in
habitat. New operations that would have this impact are not acceptable within the SAC, whilst restoration may be needed in some reaches.
Area of spawning habitat: Defined as well-oxygenated gravel / pebble-dominated (1.5-11 cm) substrate of at least 10cm depth, overlain by a range of water depths (0.2-1.5
m). River and sea lamprey typically spawn in deeper water than brook lamprey, but in larger river reaches brook lamprey also spawn in deeper areas. Elevated levels of fines
(particles <0.83 mm) can interfere with egg survival.
Area of nursery habitat: Defined as open-structured, aerated, silty and sandy substrates, between 2 and 40cm depth, typically overlain by less than 0.5 m of water. Slack-water
channel margins are particularly important, whilst silt accumulations behind weirs can also be valuable in impounded sections. The requirements of the three species are
similar and so they are often found in the same nursery beds, but in deeper water (up to 2.2 m) sea lamprey are more likely to dominate. Brook lamprey will be the only
species present above impassable weirs.
Area of emergent marginal vegetation: Emergent vegetation within marginal nursery habitat stabilises the substrate and greatly increases habitat suitability.
Extent of bank-side tree cover: This helps to provide temperature micro-gradients within the channel, which provides greater flexibility in habitat selection.
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Bullhead (Cottus gobio)
The importance of submerged higher plants to bullhead survival is unclear, but it is likely that where such vegetation occurs it is used by the species for cover against
predators. Weed cutting should be limited to no more than half of the channel width in a pattern of cutting creating a mosaic of bare substrate and beds of submerged plants.
Bullheads are particularly associated with woody debris in lowland reaches, where it is likely that it provides an alternative source of cover from predators and floods. It may
also be used as an alternative spawning substrate.
Vertical drops of 18-20 cm are sufficient to prevent upstream movement of adult bullheads. They will therefore prevent recolonisation of upper reaches affected by lethal
pollution episodes, and will also lead to constraints on genetic interactions that may have adverse consequences. New in-stream structures should be avoided, whilst the
impact of existing structures needs to be evaluated.
The characteristic channel morphology provides the diversity of water depths, current velocities and substrate types necessary to fulfil the spawning, juvenile and dispersal
requirements of the species. The close proximity of different habitats facilitates movement to new preferred habitats with age. Operations that widen, deepen and /or
straighten the channel reduce variations in habitat. New operations that would have this impact are not acceptable within the SAC, whilst restoration may be needed in some
reaches. Points to consider include:Extent of un-silted coarse (gravel / pebble / cobble) dominated substrate: males guard sticky eggs on the underside of stones. Larger stones on a hard substrate providing clear
spaces between the stream bed and the underside of pebbles / cobbles are therefore important. Elevated levels of fines can interfere with egg and fry survival. Sources of fines
include run-off from arable land, land (especially banks) trampled by livestock, sewage and industrial discharges.
Extent of slack-water refuges: these provide important refuges against high flow conditions. Suitable refuges include pools, submerged tree root systems and marginal
vegetation with >5 cm water depth.
Rationale for selection of measures of condition (features and attributes for use in condition assessment)
The attributes and targets used for condition assessment in the above FCT provide a basic evaluation of the integrity of the river habitat, in terms of
anthropogenic hydrological. Chemical, physical and biological (invasive non-native species, fish stocking) stresses. Population attributes and targets for
specific species features are provided for context and are not part of formal condition assessment. Consideration of species status is restricted to a simple
check of continued presence, as a cross-check on compliance based on habitat attributes.
Conservation Objectives: River Wensum
Final 16 03 11 Format Version 2.0
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Other Notes
River Restoration Techniques appropriate for Type I – Lowland, low gradient rivers –








Reduced/modified channel maintenance operations, to promote natural recovery of form and function.
Bank reprofiling to improve the hydrological transition zone, for the benefit of characteristic riparian plants such as brooklime, water speedwells, water-cresses watermint and marsh woundwort.
Removal/lowering of in-channel control structures, to re-establish riffle habitat, restore characteristic water depths and allow free movement of fauna.
Re-meandering or meander reconnection to restore habitat length/area and improve flow, substrate and depth diversity, thereby provide improved habitat conditions to a
wider range of fauna and flora.
Reinstatement of coarse bed material for the benefit of riffle-dwelling fish and invertebrates, preferably using material reclaimed from the flood banks using grading
machinery.
Introduction of large woody debris, as part of bank re-profiling or as partial logjams, to restore diversity of substrate and water depth/velocity.
Removal/set-back of embankments to restore hydrological continuity with the floodplain, allowing the recreation of wet grassland communities including breeding
waders. (Note: There are few if any true flood banks on the Wensum, though deposited dredgings often effectively sever the connectivity between river and floodplain)
Riparian tree-planting along stretches with no trees, to provide a beneficial mosaic of channel and riparian conditions and enhance the introduction of woody debris into
the channel.
River Restoration Techniques appropriate for Type III – Chalk rivers and other base-rich rivers with stable flows –








Reduced/modified channel maintenance operations, to promote natural recovery of form and function, particularly in respect of the seasonal encroachment of marginal
vegetation and the establishment of woody debris in the channel.
Bank reprofiling to improve the hydrological transition zone, for the benefit of characteristic riparian plants such as brooklime, water speedwells, water-cresses watermint and marsh woundwort.
Removal/lowering of in-channel control structures, to re-establish riffle habitat, restore characteristic water depths and current velocities, reduce siltation of gravel
substrates and allow free movement of fauna.
Reinstatement of coarse bed material for the benefit of riffle-dwelling fish and invertebrates, preferably using material reclaimed from historical spoil using grading
machinery.
Introduction of large woody debris, as part of bank re-profiling or as partial logjams, to restore diversity of substrate and water depth/velocity.
Re-meandering or meander reconnection to restore habitat length/area and improve flow, substrate and depth diversity, thereby providing improved habitat conditions to
a wider range of fauna and flora.
Reconnecting the floodplain, allowing the recreation of fen, carr and wet grassland communities.
Riparian tree-planting along stretches with no trees, to provide a beneficial mosaic of channel and riparian conditions and enhance the introduction of woody debris into
the channel.
Conservation Objectives: River Wensum
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Table 3b Site-Specific definitions of Favourable Condition
To maintain the terrestrial compartments and adjacent bank-side habitats of the SSSI so as not to negatively affect the
CONSERVATION
functionality of the freshwater habitats and species of the River Wensum SSSI so as to ensure that they remain in
OBJECTIVE FOR THIS
favourable condition. Favourable condition is defined at this site in terms of the following site-specific standards:
HABITAT TYPE
Site-specific details of any geographical variation or limitations (where the favourable condition standards apply)
These targets will be of assistance in drawing up the objectives for agri-environment schemes and for evaluating the management on areas covered by existing
schemes, both on terrestrial units of the River Wensum SSSI, but also with regard to land on the floodplain.
Site-specific standards defining favourable condition
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
Use
for
CA?
Rivers
Functionality of
Terrestrial
compartments
Field observation.

The terrestrial unit is in
hydrological continuity
with the river;
The terrestrial unit
supports semi-natural
vegetation;
Management of the
terrestrial units does not
contribute to the
unfavourable condition
of the river units.
Terrestrial compartments of the SSSI should be maintained in
accordance with the ‘89 Guidelines.
Yes
If a terrestrial unit is not hydrologically connected to the river, this
implies that restoration of the relationship between the river and
its floodplain is necessary.
he management of the terrestrial components of the SSSI should
not result in detrimental impacts with regard to the riverine
interests of the River Wensum SSSI.
Yes
Management of the
adjacent bank-side and
floodplain habitat,
where not included
within a terrestrial unit
of the SSSI does not
contribute to the
The management of floodplain habitats immediately adjacent to
the SSSI boundary should not result in detrimental impacts with
regard to the riverine interests of the River Wensum SSSI.
No


Rivers
Functionality of
Terrestrial
compartments
and adjacent
bank-side
habitats.
Field observation.
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Final 16 03 11 Format Version 2.0
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
Yes
Criteria
feature
Attribute
Measure
Site-specific Targets
Comments
Use
for
CA?
unfavourable condition
of the river units.
Audit Trail
Rationale for limiting standards to specified parts of the site
Rationale for site-specific targets (including any variations from generic guidance)
Terrestrial Compartments of the River Wensum SSSI - Although not part of the riverine interest of the site, the management of the terrestrial compartments of the SSSI
and adjacent floodplain habitats should not negatively impact the riverine interest of the SSSI. Objectives for the terrestrial compartments of the SSSI should ensure that these
areas continue to support semi-natural communities and remain hydrologically linked to the river as per the ’89 Guidelines.
Bank-side Habitats immediately adjacent to the River Wensum SSSI - It should be noted that the management of all floodplain habitat immediately adjacent to the
channel of the Type III river reaches of the River Wensum SSSI has potential impacts on the aquatic and emergent communities on the river. This has implications with
regard to the targeting of future HLS schemes on the floodplain as whole, and also on the evaluation of management associated with existing agri-environment schemes. The
Wensum Valley should be regarded as a key wildlife corridor in the Norfolk Ecological Network which is being developed by the Norfolk Biodiversity Partnership
Rationale for selection of measures of condition (features and attributes for use in condition assessment)
(The selected vegetation attributes are those considered to most economically define favourable condition at this site for the broad habitat type and any
dependent designated species).
Other Notes
N.B Where road run-off has been diverted off the road, through a terrestrial compartment, and straight into the river, the terrestrial unit should be regarded as being in
unfavourable condition.
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Table 3c Site-Specific definitions of Favourable Condition
To maintain the Fen, Marsh and Swamp on the River Wensum SSSI in favourable condition, with particular reference to
CONSERVATION
relevant specific designated interest features. Favourable condition is defined at this site in terms of the following siteOBJECTIVE FOR THIS
specific standards:
HABITAT TYPE
Site-specific details of any geographical variation or limitations (where the favourable condition standards apply)
These targets will be of assistance in drawing up the objectives for agri-environment schemes and for evaluating the management on areas covered by existing schemes,
both on terrestrial units of the River Wensum SSSI, but also with regard to land on the floodplain.
S3, S4, S5, and S7 are the primary habitats that host Desmoulin’s whorl snail. Favourable condition of populations of this mollusc is assessed through ensuring that the
vegetation communities that support populations of this mollusc are managed within appropriate parameters. However, Desmoulin’s whorl snail is sensitive to the impacts
of grazing, and is most likely to occur where there are significant stands of these vegetation types.
V. moulinsiana requires highly humid conditions which are met by a high water table below the stands of vegetation in which it lives. Many of the drier reed-bed
communities that are present on the site are too dry. Many of the stands of S25, S26 are secondary and have resulted from a cessation of grazing. Where this has occurred,
Desmoulin’s whorl snail is unlikely to colonise. However, where stands of S25 and S26 have developed from what were once wetter stands of reed-bed community such as
S4, then it may be appropriate to modify the hydrological regime to favour appropriate conditions for the snail.
Populations of Desmoulin’s whorl snail have been found on compartments 8, 9, 10, 11, 41 & 42, but it likely to be present at a wide range of sites on the floodplain, and the
most robust known population in the Wensum Valley is at Great Witchingham Common, immediately adjacent to the boundary of the SSSI.
Desmoulin’s whorl snail has also been found at Sculthorpe Moor (Site Unit 8), associated with S4 and S25c. This is an area which after years of neglect has been managed
by the Hawk & Owl Trust, who has carried out extensive removal of W2 secondary woodland, and has adjusted the hydrological management to make the site wetter. This
is an approach that may be appropriate for other site units e.g. Site units 5 & 6.
It should be noted that the stand of S25c at Sculthorpe Moor, the stands of S4 at Guist Common (Site Unit 22) are some of the largest stands of these communities in
Norfolk, outside the Broads. Both sites are flushing with groundwater which has further enhanced the biodiversity of these areas.
Where Site Units support fen communities that support populations of Desmoulin’s whorl snail, but also support stands of M22 and MG8 floodplain grazing marsh
communities, the level of grazing should be at a level where by the grazing marsh communities are maintained on the dryer ground, but there is only a slight impact on the
wetter tall fen and reed-bed communities. This requires a grazing regime which may be more extensive than is usually appropriate for grazing marsh communities. This
issue is particularly pertinent to Site Units 9, 10, 11, 40, 41, 42 & 43.
Conservation Objectives: River Wensum
Final 16 03 11 Format Version 2.0
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Site-specific standards defining favourable condition
Criteria
feature
Attribute term in
guidance
Measure
Site-specific Target
Comments
S3, S4,
S5, S7,
S25c
Habitat structure
Visual estimate of % cover.
Total extent of litter cover across
the area assessed should be no
more than 25%.
More than 25% litter cover indicates
insufficient removal of biomass by grazing.
S3, S4,
S5, S7,
S25c
Habitat structure
Visual estimate of % cover.
Total extent of exposed substrate
across the area assessed should be
no more than 10%.
More than 25% litter cover indicates
insufficient removal of biomass by grazing.
S3, S4,
S5, S7,
S25c
Habitat composition
A baseline map showing the
boundary of the components (where
appropriate), should be used to assess
any changes in extent. Aerial
photographs can offer a convenient
means of rapidly assessing extent in
some cases.
As a generic target there should be
no loss of the component types.
Yes
S3, S4,
S5, S7,
S25c
Vegetation
composition: positive
indicators
Visual assessment of cover, using
structured walk or transects and
recording quadrats. Comparison
against accurate baseline maps,
assessments of whether a certain
percentage of sample points laid out
upon a grid conform to the
community or not, shifts in the
position of community interfaces
along permanent transects.
As a generic standard, the
frequencies of positive indicators
should at the very least, confirm
the presence of the target
community.
Yes
Conservation Objectives: River Wensum
Final 16 03 11 Format Version 2.0
Page 53 of 75
Use
for
CA?
Yes
Yes
Site-specific standards defining favourable condition
Criteria
feature
Attribute term in
guidance
Measure
Site-specific Target
Comments
S3, S4,
S5, S7,
S25c
Vegetation
composition: indicators
of negative change undesirable non-woody
species
Visual assessment of cover, using
structured walk or transects and
recording quadrats
(a) Invasive non-native species
should be absent, or no more than
rare if present.
Invasive aliens within lowland fens may
include Crassula helmsii, Acorus calamus,
Mimulus spp., Impatiens glandulifera,
Fallopia japonica, Heracleum
mantegazzianum.
Use
for
CA?
Yes
Native species which can also be invasive
include graminoids such as Phragmites
australis, Phalaris arundinacea, Glyceria
maxima, Typha latifolia, Juncus spp.,
Molinia caerulea; tall herbs such as
Epilobium hirsutum, Urtica dioica,
Pteridium aquilinum, Rubus fruticosus; and
bryophytes such as Brachythecium
rutabulum, Eurhynchium praelongum,
Sphagnum recurvum.
S3, S4,
S5, S7
Vegetation
composition: indicators
of negative change woody species
Visual assessment of cover of the
whole feature, using structured walk
or transects. Aerial photography may
be a useful aid though will not pick
up small saplings and seedlings.
Conservation Objectives: River Wensum
Final 16 03 11 Format Version 2.0
Page 54 of 75
Woody species (including Betula,
Salix, Rhododendron, Pinus, other
gymnosperms) should be no more
than scattered, predominantly
<1.5m high. Cover should be
<10% on open fen
Saplings/seedlings should be no
more than rare. None of these
species should be present on
flushes & springs, although Salix
is acceptable at least 5m from
petrifying springs.
On many sites, the cessation of grazing has
lead to invasion of woody species and a
number of fens have moved from reed-bed
communities to W2 woodland. Although a
limited amount of scrub enhances the
biodiversity of a reed-bed, it should not be
allowed to expand at the expense of the
communities. Occasional bushes can be
important for nesting birds, and are also
used as a perch by marsh harriers.
Yes
Site-specific standards defining favourable condition
Criteria
feature
Attribute term in
guidance
Measure
Site-specific Target
S3, S4,
S5, S7
Indicators of local
distinctiveness* e.g.
notable spp., transitions
to other habitats,
presence of pools or
other structural features
Visual assessment of
frequency/cover of rare/scarce/local
species in sample points chosen to
represent their known distribution.
Structured observation or sampling.
Aerial photos may offer a convenient
means of rapidly assessing these.
Vertigo moulinsiana
Comments
Maintain the existing population of
Vertigo moulinsiana locations.
1. The extent of suitable habitat
should be maintained, compared to
the extent on a baseline map, over
appropriate area of fen or broad
margin [area of fen, swamp or
broad, and number of sample
stretches to be decided locally].
Suitable vegetation will be dense,
unbroken stands of Glyceria
maxima, Carex riparia, C.
acutiformis, C. paniculata,
Cladium mariscus and/or sparse
Phragmites.
2. Water table must be close to the
surface so that the ground remains
squelchy all year, i.e. never drying
out, so that, even in high summer,
water will rise when the soil is
trodden. Winter flooding is
permissible.
V. moulinsiana requires highly humid
conditions which are met by a high water
table below the stands of vegetation in
which it lives. Unfavourably wet
conditions can result from prolonged
flooding in summer or water penning being
set too high. Note the site has a tidally
fluctuating water level.
Current research (2000-01) will refine
acceptable limits and measures for soil
moisture.
Conservation Objectives: River Wensum
Final 16 03 11 Format Version 2.0
Page 55 of 75
Use
for
CA?
Yes
Site-specific standards defining favourable condition
Criteria
feature
Attribute term in
guidance
Measure
Site-specific Target
Comments
3. Not more than 10% (occasional
on the DAFOR scale) replacement
of preferred dominant species by
dense tall reed or by plants of drier
conditions, e.g. Urtica dioica,
Epilobium hirsutum, and low
grasses invading the litter layer,
within pre-selected stands (as
selected for).
Not more than 10% (occasional on the
DAFOR scale) replacement of tall
monocotyledons by plants preferring wetter
conditions, e.g. Rorippa nasturtiumaquatilis, Apium nodiflorum and Berula
erecta.
4. Average height of the stands no
less than 50 cm.
5. >=‘b’
In addition, no drop in class from
exiting situation.
6. >= RE3
In addition, no drop in class from
exiting situation.
V. moulinsiana requires tall leaves on
which it lives almost of the year. Heavy
grazing and mowing may be detrimental if
it removes most taller clumps.
Although the snail lives out of the water,
water quality may influence vegetation
structure and perhaps the microflora living
on the leaf surfaces where the snail feeds,
and chemical quality may directly affect the
snail when it is submerged during floods.
Future experience and research may
indicate that these variables are
inapplicable to V. moulinsiana.
No values are given for suspended solids as
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Final 16 03 11 Format Version 2.0
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Use
for
CA?
Site-specific standards defining favourable condition
Criteria
feature
Attribute term in
guidance
Measure
Site-specific Target
Comments
Use
for
CA?
this pollutant has no direct influence on the
condition of the habitat for moulinsiana.
No monitoring targets are set for hardness
but assessments for projects must take
account of the snail’s need for water whose
hardness must not fall below value
expected for the catchment.
Audit Trail
Rationale for limiting standards to specified parts of the site
Rationale for site-specific targets (including any variations from generic guidance)
Rationale for selection of measures of condition (features and attributes for use in condition assessment)
(The selected vegetation attributes are those considered to most economically define favourable condition at this site for the broad habitat type and any
dependent designated species).
Other Notes
As indicated above, the swamp communities that occupy the terrestrial compartments of the SSSI do not form part of the core special interest of the SSSI and for this reason,
assessment of these habitats using common standards monitoring is not mandatory.
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Table 3d Site-Specific definitions of Favourable Condition
To maintain the Broadleaved, Mixed and Yew Woodland on the River Wensum SSSI in favourable condition, with
CONSERVATION
particular reference to relevant specific designated interest features. Favourable condition is defined at this site in terms of
OBJECTIVE FOR THIS
the following site-specific standards:
HABITAT TYPE
Site-specific details of any geographical variation or limitations (where the favourable condition standards apply)
These targets will be of assistance in drawing up the objectives for agri-environment schemes and for evaluating the management on areas covered by existing
schemes, both on terrestrial units of the River Wensum SSSI, but also with regard to land on the floodplain associated with the upper river.
Many of the terrestrial compartments of the SSSI support stands of W5 and W6 woodland, many of which are of secondary origin, and have only developed
since the 1940s. Where these are fully established with no vestiges of the original vegetation communities present, they should be regarded as the optimum
community for the site. However, where W5/W6 or other forms of scrub are encroaching on open fens and grazing marsh communities, then it would be
appropriate to knock back the edge of the scrub and prevent further encroachment.
Site units which are dominated by extensive stands of W5 & W6 woodland are Site Units 13 & 14. These compartments should be regarded as supporting
established woodland, rather than scrub. Compartments where W5& W6 forms an established component of the mosaic are Site units 4, 5, 6, 7, 8, 10, 11, 19,
28, 29, 31 & 36.
Site-specific standards defining favourable condition
Criteria feature
Attribute term in
guidance
Measure
Conservation Objectives: River Wensum
Final 16 03 11 Format Version 2.0
Page 58 of 75
Site-specific Target
Comments
Use for
CA?
Site-specific standards defining favourable condition
Criteria feature
W5/W6
Attribute term in
guidance
Structure and Natural
processes
Measure
Site-specific Target
Comments
Assess by field survey
using structured walk
and/or transects.
Understory (2-5m) present over at
least 20% of total stand area (except
in parkland)
In coppiced stands a lower canopy cover (of
standards) can be accepted, as will also be
the case in parkland.
Canopy cover present over 30-90 %
of stand area (except in parkland
stands)
At least three age classes spread
across the average life expectancy of
the commonest trees.
Some areas of relatively undisturbed
mature/old growth stands or a scatter
of large trees allowed to grow to
over-maturity/death on site (e.g. a
minimum of 10% of the woodland or
5-10 trees per ha).
A minimum of 3 fallen lying trees
>20 cm diameter per ha and 4 trees
per ha allowed to die standing.
Conservation Objectives: River Wensum
Final 16 03 11 Format Version 2.0
Page 59 of 75
Use for
CA?
No
Site-specific standards defining favourable condition
Criteria feature
W5/W6
Attribute term in
guidance
Composition
Measure
Site-specific Target
Comments
Assess by field survey
using structured walk
and/or transects.
At least 95% of cover in any one
layer of site-native or acceptable
naturalised species.
Where cover in any one layer is less than
100% then the 95% target applies to the area
actually covered by that layer.
Use for
CA?
No
Death, destruction or replacement of
native woodland species through
effects of introduced fauna or other
external unnatural factors not more
than 10% by number or area in a five
year period.
W5/W6
Indicators of local
distinctiveness
Assess by field survey
using structured walk
and/or transects, or as
appropriate to feature.
80% of ground flora cover referable
to relevant W6 NVC community.
No
W5/W6
Regeneration
potential
Assess by field survey
using structured walk
and/or transects.
Signs of seedlings growing through
to saplings to young trees at
sufficient density to maintain canopy
density over a 10 yr period (or
equivalent regrowth from coppice
stumps)
No
No more than 20% of areas
regenerated by planting. All sp.
No planting in sites where it has not
occurred in the last 15 years.
Conservation Objectives: River Wensum
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Audit Trail
Rationale for limiting standards to specified parts of the site
Rationale for site-specific targets (including any variations from generic guidance)
Rationale for selection of measures of condition (features and attributes for use in condition assessment)
(The selected vegetation attributes are those considered to most economically define favourable condition at this site for the broad habitat type and any
dependent designated species).
Other Notes
As indicated above, the woodland communities that occupy the terrestrial compartments of the SSSI do not form part of the core special interest of the SSSI and for this
reason, assessment of these habitats using common standards monitoring is not mandatory.
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Table 3e Site-Specific definitions of Favourable Condition
To maintain the Lowland Neutral Grassland on the River Wensum SSSI in favourable condition, with particular reference
CONSERVATION
to relevant specific designated interest features. Favourable condition is defined at this site in terms of the following siteOBJECTIVE FOR THIS
specific standards:
HABITAT TYPE
Site-specific details of any geographical variation or limitations (where the favourable condition standards apply)
These targets will be of assistance in drawing up the objectives for agri-environment schemes and for evaluating the management on areas covered by existing
schemes, both on terrestrial units of the River Wensum SSSI, but also with regard to land on the floodplain. Many of the terrestrial compartments of the SSSI
are characterised by stands of MG8, M22, M23, and can form complex mosaics. However, they have become vulnerable to the cessation of grazing and tend
to become invaded by the dryer reed-bed communities. On some site units vestiges of the grazing marsh communities remain and in these situations it may be
appropriate to reinstate a grazing regime so as to reinstate grazing marsh communities.
Compartments where maintenance of MG8, M22, and M23 is the priority for management are Site Units 1, 2, 3, 4, 7, 9, 10, 11, 16, 17, 18, 19, 20, 21, 22, 23,
24, 25, 26, 27, 31, 32, 33, 34, 35, 36, 38, 39, 41, 43, & 44.
Site-specific standards defining favourable condition
Criteria feature
Measure
Site-specific Target
Comments
MG8, MG8-related
(south) M22, M23
Attribute term in
guidance
Sward structure: bare
ground
Record extent of bare ground
(not rock) distributed through the
sward, visible without disturbing
the vegetation, e.g. from the
seasonal effects of flooding.
Record in period May - end of
August (before hay cut in
meadows). Also record
sometimes in aftermath grazing
period in hay meadows.
MG8, MG8-related: No more
than 15% in May-early June or
no more than 5% in mid-JuneJuly
Outside target indicates problems with stock
management e.g. poaching, supplementary
feeding or excessive flooding.
MG8, MG8-related
(south) M22, M23
Sward structure: bare
ground
Record extent of bare ground
(not rock) distributed through the
sward, visible without disturbing
M22, M23: No more than 10%
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Use for
CA?
No
No
Site-specific standards defining favourable condition
Criteria feature
Attribute term in
guidance
Measure
Site-specific Target
Comments
Use for
CA?
the vegetation, e.g. from the
seasonal effects of flooding.
Record in period May - end of
August (before hay cut in
meadows). Also record
sometimes in aftermath grazing
period in hay meadows.
MG8, MG8-related
(south) M22, M23
Sward structure: litter
Record cover of litter where in a
more or less continuous layer,
distributed either in patches or in
one larger area. Record in period
May - end of August (before hay
cut in meadows). Also record
sometimes in aftermath grazing
period in hay meadows.
Total extent no more than 25%
of the sward
Outside target indicates biomass removal is
insufficient .e.g. lack of or insufficient
grazing or not cut for hay.
No
MG8, MG8-related
(south) M22, M23
Sward structure:
average height
Record sward height in period
May - end of August (before hay
cut in meadows). Upper target
refers to pastures only.
MG8, MG8-related Sward 5 15 cm
Sward height above upper target shows that
habitat is not being managed sufficiently e.g.
lack of or insufficient grazing or if below
lower target, is being overgrazed.
No
MG8, MG8-related
(south) M22, M23
Sward structure:
average height
Record sward height in period
May - end of August (before hay
cut in meadows). Upper target
refers to pastures only.
M22, M23 Sward 2 cm or
greater (excluding Juncus spp.)
but no more than 25% over 40
cm (including Juncus species)
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No
Site-specific standards defining favourable condition
Criteria feature
MG8, MG8-related
(south) M22, M23
MG8, MG8-related
(south) M22, M23
Attribute term in
guidance
Sward composition:
positive indicator
species
Measure
Site-specific Target
Record the frequency of positive
indicator species from the list
below to give an overall total of
2 frequent and 4 occasional or
locally abundant. Record in
period May - end of August
(before hay cut in meadows).
Achillea ptarmica, Berula erecta,
Caltha palustris, Cardamine
pratensis, Cirsium dissectum,
Eupatorium cannabinum,
Filipendula ulmaria, Galium
palustre/G. uliginosum, Geum
rivale, Hydrocotyle vulgaris,
Lotus pedunculatus, Lychnis
flos-cuculi, Mentha aquatica,
Orchidaceae spp., Potentilla
palustris, Ranunculus flammula,
small blue-green Carex spp.
(leaves less than 5mm wide) (C.
flacca, C.nigra, C.panicea),
Succisa pratensis, Thalictrum
flavum, Valeriana dioica,Viola
palustris.
Overall total of at least two
species/taxa frequent plus at
least four species/taxa
occasional throughout the
sward or locally abundant in
more than 10% of the sward
Sward composition:
indicators of
waterlogging M22,
M23 only
Record % cover of large Carex
spp. (Leaves more than 5mm
wide) e.g. Carex acutiformis.
Record in period May - end of
August (before hay cut in
meadows).
No species/taxa together or
singly covering more than 20%
of the sward
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Comments
Use for
CA?
No
Species chosen to indicate waterlogging
problems when outside target e.g. from
raised water tables.
No
Site-specific standards defining favourable condition
Criteria feature
Attribute term in
guidance
Measure
Site-specific Target
Comments
Use for
CA?
MG8, MG8-related
(south) M22, M23
Sward composition:
indicators of
waterlogging M22,
M23 only
Record % cover of Deschampsia
cespitosa, large grasses (leaves
more than 10mm wide, stout
stems) .i.e. Glyceria maxima,
Phalaris arundinacea,
Phragmites australis. Record in
period May -end of August
(before hay cut in meadows).
No species/taxa together or
singly covering more than 10%
of the sward
Species chosen to indicate waterlogging
problems when outside target e.g. from
raised water tables.
No
MG8, MG8-related
(south) M22, M23
Sward composition:
indicators of
waterlogging MG8,
MG8-related only
Record % cover of Juncus spp,
Deschampsia cespitosa, large
Carex spp. (leaves more than
5mm wide) e.g. Carex
acutiformis, large grasses (leaves
more than 10mm wide, stout
stems) i.e. Glyceria maxima,
Phalaris arundinacea,
Phragmites australis. Record in
period May -end of August
(before hay cut in meadows).
No species/taxa together or
singly covering more than 10%
of the sward
Species chosen to indicate waterlogging
problems when outside target e.g. from
raised water tables.
No
MG8, MG8-related
(south) M22, M23
Sward composition:
negative indicator
species.
Record the % cover of negative
indicator species. Record in
period May - end of August
(before hay cut in meadows).
Senecio aquaticus
No species more than
occasional throughout the
sward or more than 5% cover
Outside target can discourage hay/grazing
management because the species is toxic to
livestock, and is palatable when dry.
No
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Site-specific standards defining favourable condition
Criteria feature
Attribute term in
guidance
Sward composition:
cover of Juncus spp
M22, M23 only
Measure
Site-specific Target
Comments
Record the % cover of Juncus
species from groups A and B.
Record in period early June - end
of August (before hay cut in
meadows). Group A: jointed
rushes (Juncus acutiflorus, J.
articulatus, J. subnodulosus)
Group B: Juncus conglomeratus,
J. effusus and J. inflexus.
Species from group A at least
occasional throughout the
sward. All species combined
no more than 80% cover, of
which no more than 50% made
up of species from Group B
Juncus spp can be characteristic components
of the communities. However, increasing
cover is indicative of insufficient
management by grazing or cutting. Group B
species may indicate problems of
eutrophication from various sources when
outside target e.g. stock feeding, fertiliser
use.
MG8, MG8-related
(south) M22, M23
Sward
composition:
negative indicator
species
Record the frequency and %
cover of negative indicator
species. Record in period Mayend of August (before hay cut in
meadows). Cirsium arvense,
Cirsium vulgare, Rumex crispus,
Rumex obtusifolius, Urtica
dioica.
No species more than
occasional throughout the
sward or singly or together
more than 5% cover
Invasive species chosen to indicate problems
of eutrophication and disturbance from
various sources when outside target e.g.
poaching, stock feeding.
No
MG8, MG8-related
(south) M22, M23
Sward composition:
negative indicator
species
Record the % cover or frequency
of negative indicator species in
period May - end of August
(before hay cut in meadows). All
tree and scrub species excluding
Salix repens, considered
together. NB If scrub/tree
species in pastures are more than
occasional throughout the sward
but less than 5% cover, they are
soon likely to become a problem
if grazing levels are not
No more than 5% cover.
Invasive species outside target shows that
habitat is not being managed sufficiently e.g.
lack of or insufficient grazing/cutting
No
MG8, MG8-related
(south) M22, M23
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Use for
CA?
No
Site-specific standards defining favourable condition
Criteria feature
Attribute term in
guidance
Measure
Site-specific Target
Comments
Use for
CA?
sufficient or if scrub control is
not being carried out.
Audit Trail
Rationale for limiting standards to specified parts of the site
Rationale for site-specific targets (including any variations from generic guidance)
Rationale for selection of measures of condition (features and attributes for use in condition assessment)
(The selected vegetation attributes are those considered to most economically define favourable condition at this site for the broad habitat type and any
dependent designated species).
Other Notes
As indicated above, the lowland neutral grassland communities that occupy the terrestrial compartments of the SSSI do not form part of the core special interest of the SSSI
and for this reason, assessment of these habitats using common standards monitoring is not mandatory.
Table 3f Site-Specific definitions of Favourable Condition
To maintain the Dwarf Shrub Heath at River Wensum in favourable condition, with particular reference to relevant
CONSERVATION
specific designated interest features. Favourable condition is defined at this site in terms of the following site-specific
OBJECTIVE FOR THIS
standards:
HABITAT TYPE
Site-specific details of any geographical variation or limitations (where the favourable condition standards apply)
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These targets will be of assistance in drawing up the objectives for agri-environment schemes and for evaluating the management on areas covered by existing
schemes, on terrestrial units of the River Wensum SSSI.
Within the woodland on Great Ryburgh Common, (Site Unit 13) there is small clearing which supports a stand of H8 heath community. In the absence of
livestock, scrub encroachment has threatened to overcome this clearing, despite regular attempts to control gorse and willow. Although of limited extent, it is
one of the few remaining examples of heath vegetation in the Wensum Valley and should therefore be regarded as a notable BAP habitat hosted by the SSSI.
The site would benefit and could be expanded through clearance scrub, and knocking back of the woodland edge. The basic objective of management is to
ensure that Great Ryburgh Common (Site Unit 13) continues to host this BAP habitat.
Site-specific standards defining favourable condition
Criteria feature
H8
Attribute term in Measure
guidance
Vegetation
Visual assessment of cover, using
composition:
structured walk or transects
dwarf shrubs
Site-specific Targets
Comments
At least two species of dwarf shrubs
present and at least frequent.
In naturally species-poor sites the
presence of just one dwarf-shrub
species may be enough to meet the
target. For species-rich sites a higher
target may be appropriate (see text).
Use for
CA?
No
H8
Vegetation
structure: %
cover of dwarf
shrubs
Visual assessment of cover, using
structured walk or transects and aerial
photographs, maps.
Dwarf shrub cover 25-90% (see
section 10.4)
Dwarf-shrubs include: Calluna
vulgaris, Erica cinerea, E. tetralix,
Genista anglica. .Assess over whole
feature. Annual variation and
succession should be accounted for
within the targets.
No
H8
Vegetation
structure: %
cover of Ulex
spp.
Visual assessment of cover, using
structured walk or transects and aerial
photographs, maps.
Total Ulex and/or Genista spp. cover
<50%, with Ulex europaeus <25%.
Assess over whole feature. Gorse
species support a rich invertebrate and
vertebrate fauna. However, the can
affect the soil characteristics. See also
‘negative indicators’.
No
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Site-specific standards defining favourable condition
Criteria feature
H8
Attribute term in Measure
guidance
Vegetation
Record presence,
composition:
walk or transects
graminoids
Site-specific Targets
Comments
using structured
At least 1 species at least frequent
and 2 species at least occasional
throughout the sward; but
Deschampsia flexuosa and Nardus
stricta no more than occasional and
<25% cover Graminoids include:
Agrostis spp., Ammophila arenaria,
Carex spp., Danthonia decumbens,
Deschampsia flexuosa, Festuca spp.,
Molinia caerulea, Nardus stricta,
Trichophorum cespitosum.
In naturally species-poor sites, the
presence of just one graminoid species
may be enough to meet the target. For
species-rich sites a higher target may be
appropriate (see text).
Use for
CA?
No
Lowland dry
heathland *H1,
H2, H3, H4, H6,
H7, H8, H9,
H10, H11, H12
H8
Negative
indicators:
Species
Visual assessment of cover, using
structured walk or transects
<1% exotic species Negative
indicators – exotics include:
Rhododendron ponticum, Gaultheria
shallon, Fallopia japonica.
Exotic species should be eradicated if
possible.
No
Negative
indicators:
Species
Visual assessment of cover, using
structured walk or transects
<10% bracken (dense canopy)
Species in this list may be beneficial
for a range of invertebrates and only
become indicators of negative quality if
they are over the established limit.
No
H8
Negative
indicators:
Species
Visual assessment of cover, using
structured walk or transects
< 1 % ragwort, nettle, thistles and
other herbaceous spp Negative
indicators – other herbaceous spp
include: Cirsium arvense, Digitalis
purpurea, Epilobium spp. (excluding.
E. palustre), Chamerion
angustifolium, Juncus effusus, J.
squarrosus, Ranunculus spp.,
Senecio spp., Rumex obtusifolius,
Urtica dioica, ‘coarse grasses’.
Species in this list may be beneficial
for a range of invertebrates and only
become indicators of negative quality if
they are over the established limit.
No
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Site-specific standards defining favourable condition
Criteria feature
Attribute term in Measure
guidance
Site-specific Targets
Comments
Use for
CA?
H8
Negative
indicators:
Species
Visual assessment of cover, using
structured walk or transects
< 15% trees & scrub Tree and scrub
spp include: Betula spp., Prunus
spinosa, Pinus spp., Rubus spp.,
Sarothamnus scoparius, Quercus
spp., Hippophae rhamnoides
Up to 25% scrub cover can be accepted
if indicated in conservation objectives
or management plan.
No
H8
Negative
indicators: signs
of disturbance
Visual assessment of cover, using
structured walk or transects
<1% of habitat heavily eroded.
Record presence of signs of
overgrazing or intensive fires in the
activities list on the field form.
No
Audit Trail
Rationale for limiting standards to specified parts of the site
Rationale for site-specific targets (including any variations from generic guidance)
Rationale for selection of measures of condition (features and attributes for use in condition assessment)
(The selected vegetation attributes are those considered to most economically define favourable condition at this site for the broad habitat type and any
dependent designated species).
Other Notes
As indicated above, the lowland heath communities that occupy the terrestrial compartments of the SSSI do not form part of the core special interest of the SSSI and for this
reason, assessment of these habitats using common standards monitoring is not mandatory.
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Table 4 Species population objectives (Non-mandatory)
Conservation Objective
for species populations
To maintain the designated species in favourable condition, which is defined in part in relation to their population attributes.
Favourable condition is defined at this site in terms of the following population targets and the environmental targets specified in
the Favourable Condition Table:
Population balance
On this site favourable condition requires the maintenance of the population of each designated species or assemblage.
Maintenance implies restoration if evidence from condition assessment suggests a significant reduction in size of population or
assemblage.
Bullhead (Cottus gobio), Brook lamprey (Lampetra planeri), and White-clawed crayfish (Austropotamobius pallipes), are all
species which are associated with and dependant on the Annex I Corine Biotope: Water course of plain to montane levels with the
Ranunculion fluitantis and Callitricho batrachion vegetation and it is therefore deemed appropriate for the condition of the river units to
be determined through an assessment of the condition of this biotope.
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Table 4a – Non-mandatory protocol for monitoring Cottus gobio
Site Specific Target range and Measures (specify geographical range over which
target applies .i.e. site, BAP broad habitat or more specific)
The protocol for monitoring is described in Monitoring the Bullhead Cottus gobio,
Conserving Natural 2000 Rivers Monitoring Series No. 4. Monitoring of bullhead
should be carried out by electric fishing, with a combination of quantitative (multi-run
depletions method) and semi-quantitative (calibration method) sampling techniques.
Assessments should be made in terms of abundance classification and population
demographic structure.
Comments
In relation to abundance, compliance in lowland rivers is set at an average adult relative
population density of above 0.5 individuals per metre square. To achieve favourable
conservation status, where bullhead populations are abundant in discrete sections of a
river, more than 40% of the individuals should be in the 0+ age class. Further
assessment of the status can be derived from mapping the distribution of bullheads.

All river units should be regarded as having the potential to support populations of
bullhead. The key features that dictate the distribution and abundance of bullhead
are: water depth, water velocity and substratum composition. In lowland rivers,
the bullhead reaches maturity after one year and there are usually three or four age
classes in the population. The monitoring of bullhead populations through
electro-fishing should:


Be carried out by electric fishing on 5-10 m riffle stretches in five runs for
depletion estimates.
Stop nets should not be used during sampling.
To reduce the impact on juvenile development and avoid saturation of catches
with 0+ fish, sampling should not be carried out before August.
Table 4b – Non-mandatory protocol for monitoring Lampetra planeri
Site Specific Target range and Measures (specify geographical range over which target applies .i.e. site,
BAP broad habitat or more specific)
Comments
The protocol for monitoring is described in Monitoring the River, Brook and Sea Lamprey Lampetra fluviatilis, L. planeri
and Petromyzon marinus. Conserving Natural 2000 Rivers Monitoring Series No. 5. To provide an overview of the status
of lamprey ammocoete populations in SAC river catchments, monitoring by quadrat-based electric fishing is recommended.
The ammocoete condition assessment includes three strategies for assessment of the conservation status of lamprey
ammocoete:
All river units should be regarded as having the potential to
support populations of brook lamprey. Lamprey habitat
preferences appear to change with the stages of their life cycle.
They show a preference for gravel-dominated substratum for
spawning, and mainly silt and sand dominated substratum for
nursery habitat. Other important environmental characteristics for
optimal ammocoete habitat are shallow water with low water
velocity, and the presence of organic detritus and/or plant material.



Abundance classification – It is important that an appropriate number of sites are surveyed to account for natural
spatial variation in lamprey populations.
Population demographic structure – To achieve favourable conservation status, where abundant, river, brook lamprey
ammocoete populations should have at least two age classes in the populations sampled from optimal habitat.
Distribution – Distribution patterns should be linked to favourable habitats status, whereby no deterioration in habitat
quality is registered.
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Aammocoetes grow at a reasonably steady rate and the full range
of age classes of ammocoete larvae, from 0+ up to metamorphosis
should be present.
Table 4c – Non-mandatory protocol for monitoring Austropotamobius pallipes in Rivers and Streams
Site Specific Target range and Measures (specify geographical range over which target
applies .i.e. site, BAP broad habitat or more specific)
The protocol for monitoring is described in Monitoring the White-clawed Crayfish
Austropotamobius pallipes, Conserving Natural 2000 Rivers Monitoring Series No. 1. The
survey method recommended in this protocol for monitoring rivers is manual survey of selected
habitat refuges within a site. The method involves selection of five patches of habitat that
appear to be favourable for crayfish and can by physically searched. A search is made of 10
potential refuges in each habitat patch. The aim is to find relatively stable, individual refuges
that have the highest probability of being used by crayfish.
The relative abundance of crayfish is defined as the average number of crayfish per 10 refuges
searched. Details are recorded of the environmental conditions at the time of survey and the
features of each patch surveyed that are most relevant to crayfish. Target should not differ
significantly from those expected for the river type/reach under conditions of high physical and
chemical quality, and in any case should not drop below recent levels.
There should be an absence of individuals infected with crayfish plague and Thelohaniasis
(Porcelain Disease) should not affect >10% population.
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Comments
All river units should be regarded as having the potential to support
populations of white-clawed crayfish.
Insufficient data are available on typical densities in different river types to
set reliable targets. Monitoring units would be expected to average at least
“moderate” abundance according to monitoring category protocols.
However, crayfish densities may be lower than this on some units/rivers
due to natural factors and it would be wrong to assume such lower densities
necessarily constitute unfavourable condition. Determination of
unfavourable condition based on population attributes should only be made
where low densities are known to be related to an impact of some kind, or
where historical survey data suggest that higher densities should be present.
Regular monitoring on different river types using the standard protocol will
provide data on which targets can be produced in the future.
Table 4d – Non-mandatory protocol for monitoring Vertigo moulinsiana in Fens, Marsh and Swamp based on Presence or absence of the
named species, at the appropriate life stage which provides consistent monitoring.
Site Specific Target range and Measures (specify
geographical range over which target applies .i.e. site,
BAP broad habitat or more specific)
Monitor species once in every 6 year monitoring cycle
using generic species monitoring form as presented in
Monitoring Desmoulin’s Whorl Snail Vertigo
moulinsiana, Conserving Natural 2000 Rivers Monitoring
Series No. 6
Comments
The basis of the protocol is that the conservation status of
populations at each site will be assessed by:





Establishing a baseline of information (area and
pattern of occupancy, relative abundance and habitat
quality) within each component of each SAC.
Establishing semi-permanent transects in
representative areas of each SAC.
Carrying out yearly surveys to enable a comparison
of the data collected in each component of each SAC
with the baseline.
The surveys should provide a comparison with the
baseline using the following measures:
Population:
Area of occupancy
Relative abundance of population
Habitat:
Vegetation height
Vegetation species
Ground moisture levels
Scrub cover
Other Information: Site management
Hydrological information
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Desmoulin’s whorl snail is an annual species, and therefore needs to reproduce successfully each year. The
species may be very quickly lost from a site if conditions become unsuitable. The hydrological requirements for
the species are essentially transitional between terrestrial and aquatic; and the preferred vegetation is not a climax
community, so long-term maintenance is required to prevent succession. Desmoulin’s whorl snail is found in
two distinct habitats on the River Wensum:
Broad silty berms that are in excess of 5 metres in width.
Terrestrial compartments where a suitable hydrological, vegetation communities and management regime are
present.
Silty berms tend to be too narrow on the upper river, and Desmoulin’s whorl snail is only found in this habitat
from Guist, and other sites downstream, particularly in impounded reaches immediately upstream of mill
structures. The fact that Desmoulin’s whorl snail occurs on silty berms upstream of impounding structures must
be considered in relation to river restoration. It is possible that in the course of river restoration some populations
might be reduced on the SSSI through the manipulation of hydrological relationships.
Terrestrial compartments on which Desmoulin’s whorl snail are known to occur are Site Units 8, 9, 10, 11, 12,
40, 41, 42. However, other compartments support suitable fen vegetation where Desmoulin’s whorl snail may yet
be found. Desmoulin’s whorl snail thrives on terrestrial compartments where there is a very low intensity of
grazing pressure. However some of the site units on which it occurs also support vegetation communities of
dryer ground which depend upon a higher intensity of grazing management e.g. MG8. Where this is the case,
careful consideration needs to be given as to whether grazing can be practiced on the site at a density that is
compatible with populations of Desmoulin’s whorl snail.
However, Desmoulin’s whorl snail is known to readily colonise suitable habitats, and with the restoration of the
hydrological relationship between the river and its floodplain that would result through river restoration, this can
be used to mitigate against loss through the creation of suitable habitat elsewhere on the floodplain.
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