Climate-induced flood inundation for the Arial Khan River of Bangladesh using open-source SWAT and HEC-RAS model for RCP8.5-SSP5 scenario

Abstract Bangladesh is one of the largest flood-prone deltas GBM (Ganges–Brahmaputra–Meghna) basins, and recently, it categorized as 7th worst climate-affected country in world. Future climate change along with economic development, urbanization, increase population may worsen this situation manifolds. To cope future flood situations lessen probable losses, essential to develop maps major rivers considering scenarios. In study, inundation Arial Khan River its floodplain has been assessed for predicted scenario RCP 8.5 (Representative Concentration Pathway 8.5) using open-source mathematical models. A calibrated validated hydrologic model basins SWAT (Soil Water Assessment Tool) used estimate flow magnitudes at Bahadurabad Transit (Brahmaputra River) Hardinge Bridge (Ganges extreme emission 8.5. Using magnitude these two stations upstream boundaries, an HEC-RAS 1D set up Brahmaputra, Ganges, Padma generating offtake River. Later, 1D-2D coupled are prepared depth, duration, extent. The assessment different projections shows that there increasing trend terms from 2020s 2080s. Hence, becomes more hazardous by end century. impact on projected under SSP5 (Shared Socioeconomic Pathways 5) which indicates total flood-affected will be nearly twice 2080s compared 2020s. So, going have a dreadful effect floodplain.