With the emergence and current trend towards Water-Sensitive Urban Design (WSUD) in South Africa, there is a growing demand for Sustainable Drainage Systems (SuDS) which are a robust, cost effective and practical in terms of the challenges presented by their use in a South African context. Traditional rainwater harvesting systems focus on above ground storage (often simply JoJo tanks). This approach has limitations in terms of the volume of storage available and the quality of water (which becomes degraded over time). It also limits the additional benefits of WSUD, namely; water quality, amenity and biodiversity.
Underground storage has the potential to significantly increase available storage volumes when compared to a few JoJo tanks. With increased underground storage comes greater flexibility in supplementing water supplies as well as improved water quality and amenity when coupled with a water feature as per the RainXchange example. Infiltration to groundwater is an additional advantage of underground storage systems when capacity is exceeded.
Water-Sensitive Urban Design (WSUD) is a service we offer which assesses the benefit of using sustainable drainage systems (SuDS) on a site. Our approach includes a conceptual model of a sites drainage which allows us to simulate the optimum SuDS configuration depending on a clients need. We achieve this using PCSWMM modelling software which enables both event based (e.g. 1:50-year storm) or long-term modelling. By modelling a SuDS in this way, we can assess the performance of a proposed drainage system with regards to its influence on both the quantity and quality of runoff. With the support of other specialists, we are further able to define the amenity and biodiversity value of a proposed WSUD scheme.