Abstract: Climate change, rapid population growth, and damaged soil all contribute to flooding, which causes harm to people and property. This can be mitigated by applying flood prevention measures. One of these approaches is submerging flood-prone areas. As a consequence, this study employed GIS and HEC-RAS to map the flood-prone sites along the Machchu-II River. When a stream's release surpasses the bank-full stage along a river, flood inundation mapping is used to identify the flood-prone zones. In addition to topographical data, historical information on river banks and prior flood releases were utilized to construct maps that depicted the areas that were most likely to flood for various releases. These extreme floods had a devastating impact on the Machchu-II River region, threatening social and economic growth due to property loss and mortality. Agricultural fields and urban areas are located near rivers and are especially prone to floods. This study generated flood hazard maps for Machchu-II using the Hydrologic Engineering Centers River Analysis System (HEC-RAS) and GIS. During the preceding thirty-one flood, this river basin suffered significant property and human damage. A basic technique for processing the output of the HEC-RAS hydraulic model is also provided to aid with 2D floodplain mapping and analysis in the ArcView geographical information system.

Keywords: flood inundation, flood mapping, 2-D modelling, GIS, HEC-RAS.

| DOI: 10.17148/IARJSET.2024.11435