Flood Susceptibility Modelling Using GIS-Based Analytical Hierarchy Process (AHP) in Benin City, Nigeria

Flooding is a major hazard in both urban and rural areas today. There are several factors that determine the susceptibility of an area to flooding, and the problem of flooding cannot be solved if the flood susceptible areas are unidentified. Flood susceptibility mapping is an important way of controlling floods because it identifies the flood prone regions within an area of interest. This study aims to present a method of determining the flood susceptible zones for a watershed area in Benin City using the Multi-Criteria Decision Analysis (MCDA) approach, particularly the Analytical Hierarchy Process (AHP) and Geographic Information System (GIS). Six flood conditioning factors were selected for the study: slope, drainage density, distance from rivers, flow accumulation, elevation, and curve number. These factors were presented as raster datasets. The factors were ranked based on their potential contribution to flooding and given factor weights according to the AHP technique. The combination of these flood conditioning factors with their corresponding weights in the QGIS software was used to produce the flood susceptibility map. From the flood susceptibility map, it was observed that 26.1% of the watershed area was characterized by very high and high susceptibility to flooding.