JOURNAL OF DEGRADED AND MINING LANDS MANAGEMENT ISSN: 2339-076X (p); 2502-2458 (e), Volume 5, Number 4 (July 2018): 1363-1372 DOI:10.15243/jdmlm.2018.054.1363 www.jdmlm.ub.ac.id 1363 Research Article Application of analytic hierarchy process and geographic information system techniques in flood risk assessment: a case of Ofu river catchment in Nigeria M.I. Alfa 1* , M.A. Ajibike 2 , R.E. Daffi 1 1 Department of Civil Engineering, University of Jos, Nigeria 2 Department of Water Resources and Environmental Engineering, Ahmadu Bello University, Zaria, Nigeria * corresponding author: meshilalfa@gmail.com Received 27 April 2018, Accepted 25 May 2018 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 km 2 and 392.63 km 2 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. Keywords: analytic hierarchy process, flood, hazard, multi-criteria evaluation, risk, vulnerability To cite this article: Alfa, M.I., Ajibike, M.A. and Daffi, R.E. 2018. Application of analytic hierarchy process and geographic information system techniques in flood risk assessment: a case of Ofu river catchment in Nigeria. J. Degrade. Min. Land Manage. 5(4): 1363-1372, DOI: 10.15243/jdmlm. 2018.054.1363. Introduction There is a consensus of opinions among researchers that flood is one of the most devastating, frequently occurring and costliest natural hazards in the world, responsible for more than 30% of all geophysical related hazards, accounting for about 31 % of economic losses globally and adversely affecting more people than any other natural hazard (Nwafor, 2006; Ajin et al., 2013; Adebayo and Oruonye, 2013; Obeta, 2014, Komolafe et al., 2015). Flood generally referes to the inundation of areas of land which are normally dry. Among many other causes, the inability of a river channel to carry discharge volumes beyond its carrying capacity often results in the flooding of nearby lands which in most cases have catastrophic effect (Jeb and Aggarwal, 2008; Olajuyigbe et al., 2012). This has been the case of Ofu River catchment in Nigeria where the inability of the river to contain the volume of discharges in the peak of the rainy season has consistently resulted in the flooding of surrounding communities for over two decades now (Alfa et al., 2018). Notwithstanding this long disaster within the catchment of Ofu River, this study appears to be the first time the Flood Risk assessment will be carried out in this sub-basin. While flood risk assessment and flood risk mapping are not new, the methods adopted over time seem to be constantly evolving. Among the methods that have found very wide application in flood risk studies is the application of Multi criteria Evaluation (MCE) and Geographic