Geospatial Assessment of Urban Flood Susceptibility Using AHP-Based Multi-Criteria Technique: Case Study of Musanze, Rwanda

Abstract

Over the last decade, flood events in the northern and western urban areas of Rwanda have increased due to anthropogenic activities and the effects of  climate change. This study aims to use the Analytic Hierarchy Process (AHP) geospatial multi-criteria technique to identify flood susceptibility areas and  exposed assets in Musanze City. Seven factors were considered such as Topographic Wetness Index (TWI), Rainfall, Land Use Land Cover (LULC), Slope,  Soil Texture, River, and Digital Elevation Model (DEM) to create a flood susceptibility map with 5 classes (from very low to very high). To validate the final  map, 26 GPS points were collected from areas with a history of flooding, and the susceptibility classes were compared. Results showed that 33% of the  area (~2367 ha) was classified as high to very high risk, 23% (~1645 ha) was classified as moderate, and 44% (~3113 ha) was classified as low and very low susceptibility. The study also identified physical infrastructure and land use exposed in high and very high flooding areas, including 24 schools, 2  markets, and 1 health facility, 18668 km of roads, and 3400 buildings that are highly exposed to flooding. The applied methods in this study are useful for  urban planners and government officials in developing flood mitigation policies, strategies, and plans.