We are using a hydrodynamics model to simulate compound flooding (river flow, rainfall, and storm tide) in the coastal region of Bangladesh. We are using HEC-RAS (Hydrologic Engineering Center’s River Analysis System) rain on grid for inland flood modeling forced by rainfall from the regional climate model and upstream from the projected stream flow of the Ganges, Brahmaputra, and Meghna Rivers based on a hydrological model, which provides a comprehensive and scientifically robust framework for simulating river hydraulics, floodplain inundation, and water surface profiles under various hydrological and climatic conditions. The code was developed by the U.S. Army Corps of Engineers (USACE). HEC-RAS was used to perform Rain on Grid two-dimensional (2D) hydraulic simulations to analyze flow dynamics within river networks and floodplain systems. To develop the model, we used digital elevation data, river and coastal bathymetry, and boundary conditions such as discharge hydrographs from upstream, a global (internal) boundary for the rain on a grid model, and downstream storm tide from the coastal hydrodynamics model to compute water depth, velocity, and flood extent over time. We are also using the Delft3D model, which is a state-of-the-art hydrodynamic, water quality, and morphology modeling suite designed to simulate coastal, estuarine, and riverine processes in two or three dimensions. It was developed by Deltares (Netherlands). The model is commonly employed to simulate storm surge flooding, tidal dynamics, sediment transport, and salinity intrusion in coastal and deltaic settings. The model can simulate wave-current interactions and inundation patterns across floodplains, integrating meteorological forcing (e.g., wind, pressure) and boundary conditions (e.g., tides, river discharge). Its ability to couple hydrodynamic, sediment, and water quality modules makes Delft3D a comprehensive modeling tool for coastal zone management, climate adaptation planning, and resilience assessment in vulnerable deltaic regions like southwest Bangladesh.