Geospatial Mapping of Areas at Risk to Flood along Sokoto-Rima River Basin, Sokoto Nigeria

Abstract

The study focused on Geospatial mapping of areas at risk to flooding along Sokoto-rima river basin, Sokoto Nigeria. Five Local Government Areas were considered for this study. Natural factors causing flood in the river basin such as: soil type, precipitation, land use, slope, drainage density, and elevation were considered. Landsat 7ETM+ of 30m resolution, ASTER Global Digital Elevation Model, Global Positioning System and Precipitation Data were the methods and materials used for the study. The weightage generated for the factors through Analytical Hierarchical Process (AHP), revealed that precipitation has more effect on the flood with a total of 34%. The analysis further revealed that slope had 30%, elevation 18%, soil type 4%, drainage density 9% while land use land cover had 5% in that order. Flood vulnerability was evaluated in five classes that are: less vulnerable (1.25%), vulnerable (20.04%), more vulnerable (63.04%), very vulnerable (11.32%) and highly vulnerable (4.35%). The reclassification results further revealed that water body is less vulnerable to flood with a weight of 3, agriculture and wet land areas are highly vulnerable with a weight of 20, built-up areas are extremely vulnerable with a weight of 42, forested areas are very vulnerable with a weight of 10, while bare land surfaces are more vulnerable with a weight of 5. Vulnerability map of the study area and a percentage area of each vulnerability class was produced as the final result. This will assist decision makers in the implementation of preventive or rescue work on the menace posed by the disaster.