The use of HEC-RAS in mapping the flood inundation area: A Study on Surma River Basin, Bangladesh

Flooding poses a significant threat to Bangladesh, particularly in the Surma River Basin, where monsoonal rains and upstream discharges frequently inundate large areas. This study utilizes the Hydrologic Engineering Center’s River Analysis System (HEC-RAS) and Geographic Information System (GIS) to model and map flood inundation areas across the basin for return periods of 2, 5, 10, 25, 50, and 100 years. High-resolution floodplain maps were generated, identifying vulnerable zones and quantifying flood risks. The analysis revealed that low-lying areas near riverbanks are particularly prone to flooding, with inundation extents increasing significantly for higher return periods. Additionally, an upward trend in flood frequency over recent decades underscores the impact of climate variability. Despite challenges such as data gaps and modeling limitations, the study provides actionable insights for policymakers, including recommendations for flood zoning, infrastructure improvements, and early warning systems. The findings highlight the efficacy of HEC-RAS and GIS in addressing the complexities of flood management in Bangladesh, emphasizing the need for sustainable and adaptive measures to mitigate future risks.