Evaluating the effectiveness of Water Sensitive Urban Design (WSUD) measures in reducing runoff at the water institute in Dar es Salaam, Tanzania

Abstract

Rapid urbanization in cities like Dar es Salaam has led to increased stormwater runoff due to expanding impervious surfaces and insufficient drainage systems. The Water Institute, one of the region’s fastest-growing institutions, is also experiencing these pressures. This study investigates the effectiveness of Water Sensitive Urban Design (WSUD) measures such as bioretention ponds, rain gardens, rain barrels, and infiltration trenches at the Water Institute (WI) using the Storm Water Management Model (SWMM). A Digital Elevation Model (DEM) and ArcGIS 10.4 were used for topographic and hydrological analysis, while soil infiltration capacity was measured in the field using a Guelph permeameter, which indicated rates ranging from 1.6 to 14.9 mm/hr. Simulations revealed that combining multiple WSUD measures could reduce stormwater inflows into the drainage system by up to 68.2%, indicating substantial reduction in surface runoff volumes generated from impervious campus areas. These findings underscore WSUD’s value in managing urban runoff, promoting sustainability, and highlight the need for broader application across the Dar es Salaam and other rapidly urbanizing cities.