Flash Floods Risk Assessment of Sharg Alneel area, Khartoum State, Sudan Using Remote Sensing, GIS and Geophysical Techniques

Abstract

Abstract This study was carried out to investigate the geological sources that may cause the flash floods of Shareg Alneel area in the eastern part of Khartoum City, Sudan which lead to damage of property and the infrastructures of the residential areas. In this study, remote sensing technique using Landsat-8 images together with Shuttle Radar Topography Mission (SRTM) elevation data and geophysical techniques (resistivity and gravity) have been adopted. Wadi Soba, Green valley and Wadi El Sileit are the main seasonal water courses in the study area that drain into the Blue Nile with a regional parallel pattern. The results show that relatively steep slope from east to west may represent one of the factors contributing to the flood hazard during the rainy season. Also, it can be noted from band ratio technique that high concentration of clay sediment is located close to the River Nile and along these three valleys. This result was confirmed by resistivity technique which shows an existence of considerable amount of clayey sediments that obstruct water infiltration. The residual gravity reveals that the three valleys are characterized by relatively lower gravity anomaly indicating thicker sediments than the surrounding plains. From the obtained results, Flood hazard map has been created which divided the area into low, moderate and high risk areas. Accordingly, it was conducted that that the residential areas were superimposed over high risk zones. This study recommends re-planning of residential areas and construct dykes in the upper stream of the main valleys to decrease the flood hazard effects.