Abstract

A review of the stormwater system in the residential suburb of Belhar, Cape Town (South Africa) concluded that an existing retention pond was oversized. In addition, discharged runoff was increasing the levels of pollutants and litter in the Kuils River.

Remedial options were considered, inter alia an evaluation of a wet pond and a dry pond as management tools. Important factors included both water quantity (flow rates and volumes) and water quality (especially particulates).

SWMM (USEPA Storm Water Management Model) was used to simulate the hydrology of the Belhar catchment, and the hydraulics of the stormwater network. The analysis included typical rainfall event-based modeling of ponds and their overflow structures, and a first-order water quality study.

The results of the analysis prompted the selection of a dry pond as a pollution- and flood-mitigating measure. These results also led to an existing pond being partially filled in to allow for housing and commercial use.

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