Resilience effect of decentralized detention system to extreme flooding events

The experiences from recent urban flooding events suggest that the conventional centralized detention systems based on detention size expansion with minimum costs need to accommodate the extreme flooding events exceeding their design capacity. This study investigated the resilience effects of decentralized detention systems to address extreme flooding events in urban areas. An integrated flood resilience measure that integrates the regional performance of sub-basins with a decentralized flood control system was proposed and applied to an urban watershed including five sub-basins. Hydrologic and hydraulic analysis to quantify the hydrologic responses and resilience of the watershed to flooding scenarios was performed using the Hydrological Modeling System and Geospatial River Analysis System of Hydrological Engineering Centre models. The results identified the best locations of distributed detention ponds and characterized the effects of the decentralization levels of the detention system on enhancing flood resilience to extreme events. Additionally, an increase in the resilience effects of the decentralized detention system was found in the cases of more extreme flooding events from the combined impacts of high-intensity rainfall and land cover change. The findings suggest insights into incorporating decentralization strategies into decision-making on detention systems to resiliently cope with extreme flooding events in urban watersheds. HIGHLIGHTS The best locations of single or distributed detention ponds were in upstream or midstream sub-basins rather than downstream sub-basins.; The increase in decentralization level resulted in reduced peak flow and flooding duration during high-intensity rainfall events.; Decentralized detention systems were resilient to extreme flooding events due to synergistic storage effects on the overall watershed.; The resilience effects of the decentralized system increased as the decentralization levels of detention systems, and extremity of flooding events increased.; The proposed resilience measure was useful in evaluating the resilience effects of decentralized detention systems over a wide range of flooding scenarios.;