Multicriteria Flood Risk Analysis of Lower Ogun River Basin

Abstract

Issues pertaining to flood and flood-related damages always generate global interest in different circles. This study utilised remote sensing techniques to develop flood risk map of Lower Ogun basin in Southwestern Nigeria. Microscale environmental variables of landuse and landcover typologies, rainfall, NDWI, DEM, slope, geological formation, and population density were used as input for weighted overlay multicriteria modelling using Idrisi Taiga and ArcGIS 10.0. These environmental variables were used to generate flood hazard map. Flood risk map was developed in which flood hazard map was combined with population data. Inter-parameter and intra-parameter modeling techniques were used to generate the flood risk based on flood-stimulating coefficient values. Results showed that about 77.62% of Lower Ogun lies within flood hazard zone (with 53.24% under high flood hazard intensity and 24.38% under very high flood hazard intensity. Further, flood risk intensity showed that 60.62% of the area is highly risky to flood occurrence. Therefore, it was recommended that a green belt buffer of 65 metres on both sides of the main river should be established for proper flood zone delineation.

Keywords: Flood modeling, environmental variables, water level, flood hazard, Remote Sensing and GIS