Steady Flow Simulation for Flood Inundation Mapping of Calabar River Using HEC-RAS and QGIS

Abstract

Communities in Cross River State, Nigeria are regularly at risk of flooding. This study addresses this challenge by developing high-precision floodplain maps for the Calabar River, a key source of flood events. The terrain variations of the river were captured by creating a Digital Elevation Model (DEM) with QGIS and Google Earth Pro. Steady flow scenarios at seven profiles with a discharge of 198.22, 283.17, 1415.84, 1982.18, 2831.69, 3398.02, and 4247.53 cubic meters per second were simulated using the robust hydraulic modelling program HEC-RAS. A minimum discharge of 1415.84 cubic meters per second (m³/s) has been identified to trigger flooding in the region. This discharge corresponds to a water depth of 0.01 to 44.72 meters and an inundation area of 3473288 square meters. The Froude number along the channel ranges between 0.12 to 1.01. Specifically, areas like Maine-Edgerly Road, Garden Street, Eyo Edem Street, Marina Resort, Ekorinim Road, and Tinapa Resort were identified as particularly vulnerable under this flood scenario. The generated floodplain maps are for flood risk mitigation and disaster preparedness. Local authorities can leverage these maps to identify flood-prone areas, implement preventative measures, and develop effective evacuation plans. Furthermore, the study highlights the need for sustainable land-use practices to decrease the region's vulnerability to flooding. This research ultimately contributes to building resilient communities and enhancing environmental safety in Cross River State.