Benefit of Application of Wetland Basin as LID Measures for Management of Stormwater Runoff of an Embanked Drainage Catchment with Pumping Facilities

Megacities like Dhaka face significant challenges from rainfall-induced flooding, driven by climate change, unplanned urbanization, and inadequate drainage systems. The Boalia Khal catchment, in northeastern Dhaka, is one such area with a proposed embanked drainage system and pumping facilities. This research investigates the impact of Wetland Basins (WB) as low impact development (LID) measures on reducing runoff, flood extent, and pumping duration in the Boalia Khal catchment. A 1D–2D coupled drainage model, developed using the DHI MIKE URBAN interface, was used to simulate various rainfall scenarios. The drainage system is designed to manage a 1-day, 5-year rainfall event, while the pumps are set for a 2-day, 5-year event. The effectiveness of WBs was assessed for 1-day, 10-year and 25-year storm events. Results show that the application of WBs reduces peak water levels by 4.5 cm upstream and 8.4 cm downstream during a 25-year event. Additionally, flood extent decreases by 3% for a 10-year storm and 6% for a 25-year storm. WB implementation also leads to a 46% reduction in pumping duration, or 7.5 h, for a 10-year event. The study concludes that Wetland Basins significantly improve flood mitigation and drainage performance when integrated with the proposed system, especially when the inlet control structure is placed below the pump start level.