Flood Hazard and Flood Risk Vulnerability Mapping Using Geo-Spatial and MCDA around Adigrat, Tigray Region, Northern Ethiopia

Abstract

In Ethiopia, urban floods incidents are becoming a serious problem in recent years. They are mainly associated with poorly designed urban drainage system and land use planning. Combined to it, lack of early warning system and organized flood disaster mitigation measures at national and local level further increases the gravity of the problem. Adigrat is one of the north Ethiopian towns which is frequently attacked by these floods. To understand and address the issue, a study was conducted around Adigrat town with the aim to spatially delineate the flood hazard and risk with the help of geo-spatial and multi-criteria decision analysis (MCDA) tools. Baseline maps were developed using Landsat satellite images, DEM, aerial photographs, rainfall data and census population data. Different variables like slope, elevation, rainfall, water table, flow direction and flow accumulation, LULC, population density, building density and road density were considered for developing a model. After the data is collected and organized, Erdas Imagine and ArcGIS software were used to process and prepare the model, and finally weighted overlay model was adopted to stimulate the prototype. Each baseline maps was weighted against its impact since all factors have no the same importance. Accordingly, slope, LULC, elevations; and population density, flood hazard and LULC were found the most important factors. The flood risk areas are delineated based on flood hazard, LULC, population density, road and building density. The results indicate that the Kebeles03, 04 and 05 (center of the town) with flat slopes, low altitudes, more population and significant amount of built up area are found to be the most vulnerable for flood hazard. On the other hand, the Kebeles 01, 02 and 06 lying southwest and west of the study area are least affected by flood due to steep topography and high altitudes. It is suggested that similar type of inter-disciplinary studies are essential to minimize the damages and assure sustainable urban development. Keywords:  Geo-spatial; Flood hazard; Flood risk; Vulnerability mapping; Adigrat town; Ethiopia