Flood risk assessment by analysing flood frequency and probable inundation maps for Ishwardi Upazila, Pabna, Bangladesh

ABSTRACT Flooding in Bangladesh, driven by geomorphology and climate, poses significant risks to livelihoods and infrastructure. This study evaluates the flood risk in Ishwardi Upazila, a key agricultural and economic region, using flood frequency analysis and inundation mapping. The results show an alarming upward trend in water levels at the Hardinge Bridge Pakshi station on the Padma River, increasing the long-term flood risks. The Pearson Type III distribution was identified as the most suitable model for flood frequency analysis, revealing that 20.82, 46.32, 59.73, and 60.02% of Ishwardi could experience inundation during 2.33-, 10-, 100-, and 200-year return period floods, respectively. Low-lying areas (F3 and F4) are likely to be fully inundated during extreme events, while highlands (F0), covering 52% of the region, remain unaffected, offering critical refuges. Key infrastructure, including the Ruppur Nuclear Power Plant and Export Processing Zone, is protected by higher elevations. However, unions such as Lakhsmikandi, Muladuli, Dashuria, and Sahapur may face severe flooding risks. Despite limitations in the GSMap rainfall data, the MIKE 11 NAM-based rainfall–runoff model highlights the risks of reduced groundwater recharge and increased waterlogging due to urbanisation. These findings emphasise the need for proactive flood risk management and infrastructure planning.