Assessment of Water Erosion Hazards by Flash Floods Using Remote Sensing and GIS: A Case Study of Wadi Alhaytah Watershed in Wadi Natrun, Egypt

Abstract

Water erosion by flash floods is one of the major threats to the sustainable development and the environment. Recently, in Egypt, flash floods occurred frequently, causing loss of life and destruction of ecosystems. The objectives of this study are to assess the hazards of the November 5, 2015 flash flood in wadi Alhaytah watershed in Egypt using GIS and remote sensing, and develop a flood control strategy that reduces an unexpected flood risk. Two Sentinel-2 satellite images were selected for the study, which acquired on August 16 and November 14, 2015. The maximum likelihood supervised classification technique was applied on the two images to produce temporal land use/cover (LULC) maps. The hazards of the flash flood and water erosion were assessed through monitoring of LULC changes between the two dates. A flood control strategy was proposed for the watershed through a developed GIS procedure. Results indicated that the catchment area is characterized by remarkable variations in elevations and slopes. Assessment of flood hazards revealed that 32.23 km2 (3223 ha) and 1.04 km2 (104 ha) of the cropland and fish farms, respectively, were removed or destroyed, which would affect the national agricultural production and food security. Therefore, fifty six suitable locations of storage dams were spatially proposed in the catchment area to mitigate unexpected floods, prevent loss of human and animal lives, decrease soil erosion, enhance soil moisture, and increase the yield of the existing aquifers, especially ground water is the only water resource available for agricultural development in the region.