Rainwater Harvesting Innovations for Flood-Resilient Cities

The expansion of impermeable surfaces in cities have absurdly increased the urban runoff; blocking its pathways to infiltration and evaporation. Rainwater harvesting can be considered as an effective initiative to tone-down the disruptions made to urban runoff pathways.While adopting built form-led solutions from one end to address the consequences of increased urban runoff which eventually increases the frequency and magnitude of urban flooding, rainwater harvesting solutionscan also be adopted in parallel. This study attempts to simulate runoff levelscorrespondent to different vertical-density configurations with reference to a selected micro-watershedin Colombo, Sri Lanka. Simulations were made for four hypothetical built form scenariosin which a roof rainwater harvesting system is in-built: high-rise, intermediate-rise, mid-rise and low-rise. The extent of land and the size population were constant under each scenario. As per the results revealed,low-rise built form was identified as the most disturbing to natural pathways, whereas high-rise built formwas recognized as relatively better options for built-up area expansion.