Geospatial Assessment of the Impact of Topography on Flood Vulnerability in Maiduguri, Nigeria

Abstract

In this paper, Remotely sensed data and Geographical Information System (GIS) techniques were used to assess the impact of topography on flood vulnerability of the terrain of Maiduguri. ASTER GDEM data were acquired online from which Triangulated Irregular Network (TIN) map of Maiduguri using contour 5 meters was generated. The TIN map was rasterized and classified into five flood liable zones: extremely liable, highly liable, liable, marginally liable and free flood zones. The flood vulnerability zone in each of the seventeen districts in Maiduguri was delineated and quantified. The study revealed that based on the topography of the city alone, eight (8) out of the seventeen districts in Maiduguri comprising Jabbamari, Dusuman, Maimusari, Old Maiduguri, Shehuri North, Tamsu Ngamdu and Yerwa constituting 21.88% of the Maiduguri land area, and holding the major population of the city, have their entire land area fall within either extremely liable or highly liable flood zones. Other districts with a high percentage of their land area within extremely or highly liable to flood zones are Gwange (80.72%), Mairi (68.78%), Bolori (56.55%). The result of the study also revealed that the impact of topography on excessive flooding in the core of Maiduguri (Yerwa, Shehuri North among others) as well as areas around the Jere Bowl is enormous. However, topography was found to play no role in the flooding of Bulumkutu area, which suggests that other factors other than topography are responsible for Bulumkutu floods. It was recommended that flood management and control should be prioritized based on how liable an area is. For instance, all the districts that were found to be highly liable to flooding should be given urgent attention before the ones with low possibility of being flooded. The integration of other factors, including topography for flood vulnerability of Maiduguri city as well as the causes of Bulumkutu floods is recommended for further studies.