Integrating ecosystem services
considerations into line function
management
Stormwater
Candice Haskins
City of Cape Town - Catchment, Stormwater & River Management
29 February 2012
Stormwater Management in Cape Town
…..setting the scene…..
Stormwater management in urban built up areas is a local
authority competency….(Constitution)
Cape Town’s “stormwater system” encompassres both the constructed and
natural facilities, including pipes, culverts, watercourses/wetlands and their
associated floodplains….(Stormwater By-Law)
Integrated Urban Catchment Management approach with the entire stormwater
system managed holistically
Strategic focus areas:

Development control adjacent to rivers and wetlands

Flood management – protection of infrastructure and public

Water quality management for protection of public & ecosystem health

Proactive maintenance to maintain / improve functioning of stormwater system
Impacts of urban development on
surface waters
General “physical” impacts
Impervious surfaces & highly compacted soils – reduced infiltration &
greatly increased run-off
Roads – fragmentation of habitats
Infilling & drainage of wetlands
Encroachment on aquatic systems & riparian areas – habitat
disturbance
Canalisation of natural streams – creates sterile, homogenous habitat
Impacts relating specifically to urban stormwater
Water quality > mobilisation of pollutants on land surface
Water quantity > altered hydrological regime & seasonality
Compromised groundwater recharge
Consequences of Urban Impacts for “Aquatic”
Goods & Services
 Reduced
biodiversity > loss of sensitive species & increased
generalist / pollution-tolerant species.
 Loss
of regulating services e.g. natural purification & flood
attenuation functions.
 Toxic
events e.g. fish kills and potential human health risks.
 Quality
of recreational waters impaired & reduced aesthetic
appreciation of urban watercourses & wetlands.
 Reduced
property values near watercourses & wetlands.
 Increased
costs > ecosystem management, rehabilitation &
maintenance
 Bad
press > economic / tourism losses
What can be done to reduce / manage
these urban impacts?
Policy, planning & development guidelines.
Development setbacks & buffers around sensitive areas.
Plan & design developments to minimize impervious
Ad hoc? Or a
areas, runoff & pollution.
“water
Minimize the use ofpurposeful
detergents, fertilizers
& pesticides.
approach
to
Use indigenoussensitive”
plant species adapted
to local conditions.
Understanding drainage
pathways > “drains
managing
and to river / sea”.
Report pollution, illegal
dumping, or cities?
soil erosion.
designing
By-law enforcement.
Education
Water Sensitive Urban Design
Integration of urban planning with the management, protection and
conservation of the urban water cycle that ensures that urban water
management is sensitive to natural hydrological and ecological
processes
Stormwater, Potable Water & Sewage infrastructure and value chains
Consider the environment in conjunction with infrastructure design and
management at the earliest possible stage of the decision-making and
planning process.
Key WSUD principles:

Protect existing natural features & ecological processes.

Maintain natural hydrologic behaviour of catchments.

Protect water quality of surface & ground waters.

Minimise demand on potable water supply system.

Minimise sewage discharges to natural environment.

Integrate water into landscape to enhance visual, social, cultural and ecological
values
Extent to which WSUD is achieved can be
tracked along a continuum
C
a
p
e
T
o
w
n
?
?
Approved Council Policies (2009)
Floodplain and River Corridor Management Policy
Developments set back beyond the applicable flood prone
area or ecological buffer which ever represents the greater
setback distance from the river / wetland.
Buffers represent a mechanism to protect aquatic systems
from adjacent developments and activities.
Management of Urban Stormwater Impacts Policy
New developments are required to introduce “Sustainable
Urban Drainage Systems (SUDS) to manage stormwater
quality and quantity on site and encourage infiltration.
SUDS include a range of structural and non-structural best
management practises such as site house-keeping / pollution
Both policies
management, infiltration basins, swales, treatment wetlands.
supported by
Applicable throughout the catchment - has ultimate
Stormwater Byobjective of protecting receiving environments from the
Law
harmful affects of urban development.
City Spatial Development Framework
Policy imperatives
encompassed in
City’s SDF
Other high level sectoral iniatives…
Climate Adaptation Plan of Action (CAPA) Stormwater
“Rehabilitation and sound management of wetlands, rivers and floodplains could
assist with ensuring sustainability of ecosystem “goods and services” such as flood
attenuation, increased carbon sequestration and pollution abatement. The retention
of these ecosystem services is imperative in increasing the resilience of the
landscape to cope with the expected changes and thereby reduce the risk profile and
increase the adaptive capacity of the City as a whole”
Urban Design Policy (in prep) Water Sensitive Urban Design principles
WRC national project Water Sensitive Urban Design (WSUD) or Low
Impact Design (LID) for improving water resource protection/conservation
and reuse in urban landscapes (WRC K5/2071/1)
Learning Alliances and community of practice to promote WSUD in CT
TOOLS / Available Data and Information
River and wetlands
spatial data (GIS)
with descriptive
attributes relating to
type, condition and
importance
List of criteria for
assessing functional
importance of
wetlands (CCT
Wetland Mapping
Project: ground-truth
phase)
THANK YOU
http://www.capetown.gov.za/en/CSRM/Pages/default.aspx