Improving Flood Inundation Mapping Accuracy Using HEC-RAS Modeling: A Case Study of the Neches River Tidal Floodplain in Texas

The Neches River Tidal floodplain has been historically prone to flooding, resulting in critical shutdowns of refineries and port transit. This study implements a one-dimensional (1D) and a coupled 1D/two-dimensional (2D) Hydrological Engineering Center's River Analysis System (HEC-RAS) model including the bathymetry data of the main channel to develop flood inundation maps under different hydrological and hydraulic conditions. Comparing the 1D model with the FEMA Base Level Engineering (BLE) model, the results show that flood inundation maps are highly sensitive to the bathymetry data, which is essential to simulate accurate flood inundation maps for a river with dredged waterways. The inundation maps simulated by the 1D/2D model have better agreement with the high-water marks than the 1D model during Hurricane Harvey. In conclusion, coupled 1D/2D modeling provides a more realistic depiction of flood threats with the limited available data and is superior to the FEMA BLE model for producing accurate flood inundation maps of the Neches River Tidal floodplain.