Hydro-Geomorphological Mapping for Flash Flood Risk Assessment in Jigawa State

Flash floods in North West Nigeria's semi-arid environment cause recurrent loss of life, property, and agricultural output with limited warning. This study develops a hydro-geomorphological map for flash flood risk assessment in Jigawa State using remote sensing and GIS. SRTM digital elevation data are processed to delineate watersheds, stream networks, and geomorphological units including pediments, valley fills, alluvial fans, and floodplains. Morphometric parameters including drainage density, basin shape factor, and stream frequency are computed for 12 sub-catchments. Flash flood susceptibility is modelled using a weighted multi-criteria evaluation integrating slope, curvature, drainage density, land use, rainfall intensity, and geomorphological unit type. Results classify 23 percent of the state's land area as high or very high flash flood susceptibility, concentrated along the Hadejia River corridor and the Kafin Hausa plain. Validation using a geo-referenced inventory of documented flash flood events from 2015 to 2023 achieves an area under the ROC curve of 0.87. The study provides geomorphological risk data for the Jigawa State Emergency Management Agency. Keywords: flash flood, geomorphological mapping, GIS, Jigawa, risk assessment