GIS-Based Flood Hazard Mapping in Itang District of the Gambella Region, Ethiopia

Abstract

Flood is one of the natural disasters that affect societies around the world. Every year, flood claims hundreds of human lives and causes damage to the global economy and environment. Consequently, the identification of flood-vulnerable areas is important for comprehensive flood risk management. This study aims to delineate flood hazard areas in Itang District of Gambella Region, Ethiopia, applying the Gumbel probability distribution and Analytical Hierarchy Process (AHP) method. Distribution models applied in the study involve the generalized extreme value, Gumbel, Log-Normal, and Log Pearson type III. The Gumbel distribution provides the best fit according to the extreme value analyses. After obtaining discharge level through the method, the region's flood inundation area was mapped at 5, 10, 25, 50, and 100-year recurrence intervals. The developed methodology processes six parameters, namely, slope, elevation, land-use/land-cover, rainfall, discharge, and soil. Each criterion was evaluated with the aid of AHP and mapped by GIS. Data were assorted into five suitability classes, viz., very high, high, moderate, low, and very low flooding areas, representing 29.7%, 27.8%, 18.5%, 12.7%, and 11.4%, respectively. The outcome is extremely useful for evacuation planning, damage assessment, and losses estimation, thereby minimizing the natural disaster's effect in the study area.