Flash Flood Risk Assessment of Wadi Degla Basin Protected Area, East of Maadi, Cairo, Egypt Based on Morphometric Analysis Using GIS Techniques

Abstract

The Wadi Degla basin is amongst the most important basins in the north-eastern part of the Eastern Desert, east of Maadi, Cairo, which drains into River Nile. It covers an area of about 177.6 km2. Although it located in an arid region, the basin could receive a huge amount of rainwater during heavy rainstorms which in turn lead to initiate flash flood hazard and causing catastrophic effects on existing infrastructure of main gate and tracks of protected area, also threatened visitor's life and surrounding environments. The present study aims to evaluate of flash flood risk in Wadi Degla and possible mitigation. The morphometric parameters investigation were carried out using ASTER Digital Elevation Model (DEM), GIS, and geomorphic field observations. Using a technique given by El-Shamy, the risk degree for the Wadi Degla basin's vulnerability to flash flooding risk was calculated. The first technique focuses on the relationship between drainage density and bifurcation ratio, whereas the second relies on the relationship between drainage frequency and bifurcation ratio. For the examined basin of the watershed, the third morphometric parameter (the bifurcation ratio, drainage density, and stream frequency) were obtained and calculated. The bifurcation ratio, stream frequency, and drainage density all have values of 1.7, 6.05, and 2 according to morphometric study. The bifurcation ratio, stream frequency, and drainage density have morphometric values of 1.7, 6.05, and 2 respectively, as per morphometric analysis. The Wadi Degla has elongated shape. According to the computed metrics (e.g., stream frequency, bifurcation ratio and drainage density), the Wadi Degla basin catchment area falls into category (A). This means that there is expected high susceptibility of flash flooding possibility in the area under consideration. This expected risk leads the Ministry of Water Resources and Irrigation to establish three dams on the pass of Wadi Degla to work as an obstacle for decrease the flash flood velocity flow. Consequently, from an environmental hazards point of view, the Wadi Degla Protected Area should be closed during heavy rainfall for visitor safety and also avoid the establishment of any basic infrastructure in the vicinity of the Wadi pass.