Application of Analytic Hierarchy Process and Geographic Information System Techniques in Flood Risk Assessment: A Case of Ofu River Catchment in Nigeria

Abstract

Flood risk assessment of Ofu River Catchment in Nigeria was carried out by integration of thematic maps in ArcGIS 10.2.2. Analytic Hierarchy Process (AHP) was applied in the decision making and ranking of flood causative factors before their integration for development of hazard map in ArcGIS. The social and physical vulnerability of the catchment were considered in the development of the vulnerability map. The flood risk map was developed as a product of the hazard and vulnerability map. The results showed that the land areas within the Very High and High Risk zones were respectively 163.07 km² and 392.63 km² with Igalamela/Odolu Local Government Area (LGA) accounting for about 62% and 31% respectively. A total of 19, 034 and 47,652 persons are respectively at very high and high risk of flood within the catchment. Oforachi community in Igalamela/Odolu LGA and Ejule Ojebe Community in Ibaji LGA both in Kogi State are respectively at Very High and High Risk of Ofu River flood. High Impacts were recorded by about 35% and 52% of Oforachi Community during the 1995 and 2000 historical flood events. A watershed management plan is therefore required to prevent the serious damage experienced in previous flood events.