Flood Inundation Mapping of Calabar River Using Hec-Ras and QGIS

Floods pose significant challenges worldwide, affecting communities, ecosystems, and economies. In Cross River State, Nigeria, the Calabar River, with its complex river network and climate conditions, is particularly vulnerable to recurrent floods. Recent events, such as the destructive flood in Cross river Local Government Areas highlight the urgent need for comprehensive flood management in the region. This study addresses the ongoing flood problem by utilizing a combination of HEC-RAS and QGIS for detailed flood mapping. Geospatial data extraction from Google Earth Pro, Digital Elevation Model (DEM) development in QGIS, and high-precision floodplain mapping using HEC-RAS form the core of the research scope. Three simulation Profiles with varying discharges of 1189.31, 1727.33 and 2491.88 cubic meters per second were used. The study found that the flow in the channel is subcritical, with a Froude number between 0.2 and 0.72. The results revealed that Profile 1, 2 and 3 resulted in an inundation area of 3365733.24, 3770894.64 and 3994215.90 square meters respectively with Profile 3 resulting in the highest flooding area. The findings reveal subcritical flow in the Calabar River, indicating slow and calm flow conditions. The study's key contribution lies in providing a detailed Flood map, offering crucial insights for disaster preparedness and risk mitigation. These findings highlight the importance of comprehensive flood mapping and robust risk assessment in flood-prone regions provides practical tools for enhancing flood resilience in the Calabar River region and beyond.