Implementation Strategies of Detention Tanks for Improving Drainage System Resilience

Globally, recent intensification of human activities for urbanization and climate change has triggered significant growth in urban runoff, responsible for increased frequency and magnitude of urban flooding and drainage system failure. Detention tanks are one of the efficient stormwater control measures extensively adopted as temporary storage of flood volume during frequent extreme rainfall events. Different positions of detention tanks within catchment not only have different impacts on upstream and downstream drainage system performance and their designed efficiencies but also have a strong influence on other parts of the drainage system and network of detention tanks. This study aims to propose and compare four implementation strategies of detention tanks, named (1) Analytic Hierarchy Process (AHP)-based, (2) centralized-based, (3) drainage area-based, and (4) land use-based under different designed rainfall scenarios (e.g., 2, 5, 10, 20, 50 and 100-year return periods) and performance evaluation measures (e.g., flood volume reduction, outlet peak flow reduction, system resilience) in a real case study in an urban district of Shanghai City, China. Results conclude AHP-based strategy performed far better than others for the improvement of system resilience and flood volume reduction, followed by drainage area and centralized-based approaches, and the least performance was shown by landuse approach. Efficient planning and designing of detention tanks for optimal locations need a preliminary screening of locations at an earlier planning stage considering multiple local construction constraints.