Ecosystem Guidelines for Environmental Assessment

FRESHWATER
Introduction to the system of:
- terrestrial alien and invasive vegetation
- aquatic alien vegetation
- alien fish and other animals
Pollution sources affecting water quality - point and non-point sources.
Pollution sources affecting water quantity (e.g. stormwater runoff; discharge from waste water
treatment works).
Inter-basin transfers.
Emphasis on development that compromise long-term ecosystem functioning.
What are the “bottom lines” and non-negotiables
A flow regime that is adequate to maintain the river at a desired and attainable Management Class.
Water quality that is adequate to maintain the river at a desired and attainable Management Class.
Buffers that:
- are adequate to protect from the threats identified below, as relevant to each system,
- allow for future rehabilitation, and
- protect the habitat integrity of the receiving watercourse.
Maintenance of existing ecosystem linkages/connectivity at an appropriate scale.
No new concrete canalisation or piping of river channels.
What broad spatial guidelines can be given with respect to
the best approach to development and disturbance
Allow adequate buffering of rivers and drainage lines. Ideally, buffer areas should first make allowance
for future rehabilitation of the channel e.g. regrading and reshaping of hardened river banks - and then
impose development setbacks from the theoretical edge of the rehabilitated river bank. The City of Cape
Town's Floodplain Management Guidelines 1 should be used as broad guidelines for minimum setback
areas. Additional evaluation of specific functional requirements of the buffer areas, on a site-specific
basis (e.g. providing an appropriate buffer width for a system receiving treated effluent runoff, versus
providing an adequate buffer against noise pollution or alien invasion).
Spatial depiction of existing or past linkages between wetlands, drainage channels and rivers/streams
should be provided, including groundwater information where applicable; these linkages should be
maintained where possible, and restored where feasible and ecologically desirable.
What are the critical things to maintain in terms of managing these
systems for biodiversity, and ensuring its persistence
Flow regime, including seasonality, water quantity and links to the water table and groundwater system.
Water quality.
Bank slope and stability.
Maintenance of natural erosion and sedimentation processes.
Plant community structure and zonation.
Habitat availability and accessibility.
Instream biotope quality and availability.
Control over invasion by opportunistic weeds and other invasive plant species.
Control over invasion by introduced exotic fish and other alien fauna.
76 : FRESHWATER ECOSYSTEMS - RIVERS 1. City of Cape Town (November 2000) Development Control Guidelines for Flood-prone
Areas – Draft edition. CCT Catchment, Stormwater and River Management, Catchment
Management Department, Cape Town.