Flood hazard assessment of River Dep floodplains in North-Central Nigeria

Abstract

Flood is a recurring event that leads to hazards. The probability of a flood occurring is normally investigated followed by flood hazard mapping which defines the areas that are at risk of flood inundation. This study carries out flood hazard assessment for the flood prone areas within the low-lying flat river valley of the River Dep watershed using Remote Sensing (RS) and geographic information system (GIS) for 2-year to 1000-year return periods, with regards to inhabited areas and other land uses that will be affected. Result shows that the most affected land use within the floodplain is agriculture with inundated area ranging from 68.82 to 146.10 km2. Low to medium flood hazards predominant dominate the floodplain with area extent increasing from 112.2 to 140.75 km2 for low hazard and 35.65 to 163.65 km2 for medium hazard. High hazard is mainly within the deep part of the floodplain with minimal area extent of 4.11 km2. The study recommends low hazard areas to be used for irrigation farming and early rainy season farming, medium and high hazard areas for irrigation farming only while low, medium and high hazard areas for the 100-year flood should be avoided with respect to construction of residential or commercial structures. Generally areas close to rivers should be avoided for rainy season farming and residential or commercial development.   Key words: Flood hazard, remote sensing, geographic information system (GIS), land use, land cover.