Indicators for Disaster Vulnerability to the Overflowing of the Niger River in Adjoining Settlements in the Confluence City of Lokoja, Nigeria

Abstract

River overflow is one of the main causes of flooding and erosion. In Nigeria, flooding affects (loss and damage to properties and distortion of sources of livelihood) and displaces more people than any other disaster (loss and damage to properties and distortion of sources of livelihood). The 2012 overflowing of the River Niger and the subsequent flooding of Lokoja historically represent the most devastating natural disaster in the city. The study was based on the Geographic Information System’s (GIS) Multi Criteria Analysis (MCA) and examined the risk and vulnerability of Lokoja’s settlements adjoining the Niger River to flooding. The criterion considered were elevation, land cover, slope, curvature, flow accumulation, the Normalised Difference Water Index (NDWI) and the drainage density of the study area. The data used for this study was obtained from a secondary source United States Geological Survey (USGS). The relationship between the NDWI and the precipitation in Lokoja showed that the NDWI and precipitation were inversely related. This implied that an increase in precipitation was consequential to the intensity of the water index in the study area. This study successfully showed the capability of remote sensing and the GIS to assess both pre- and post-disaster (flooding) vulnerability. It also revealed that high precipitation and increasing physical development due to urbanisation in lowlands increased the vulnerability of an area to flooding. The recommendation forwarded was the need for improved river basin management and flood disaster prevention. Keywords: Niger River Overflow, Building Susceptibility and Vulnerability, Urban Flooding and Erosion, Flood Prone Areas, Spatio-temporal Analysis, Multi Criteria Analysis (MCA).