Morphometric analysis and flash floods hazards assessment for Wadi Al Aawag drainage Basins, southwest Sinai, Egypt

Assessment of surface runoff in arid regions is extremely important. Water means life; hence, the best management of flash floods promote groundwater recharge, prevents flood hazards and soil drift that is required for developing purposes. The main objective of the present work is to evaluate the morphometric parameters and flash flood hazards that frequently occurred in Wadi Al Aawag Drainage Basin. The study is based on applying the Arc GIS 10.5 program to draw drainage basins and to compute their morphometric attributes. The hydraulic model (HEC-HMS) in the WMS program was used to compute the peak flow hydrograph of floods for different sub-basin. The calculations of water quantities and peak flow were based on the SCS unit hydrograph approach. Results indicate that all the studied sub-basins have low R_b (1.99–3.7), this tends to give more possibilities to flash floods. The studied sub-basins have high densities ranges between 1.21 (Maier) and 1.62 km/Km² (Ghewitat), this reflects high relief, impermeable subsurface material, and low contribution for groundwater, especially in the area covered by basement rocks (upstream portions). The decrease in time of concentration of Gebah is associated with an increase in the relief (1900 m) and relief ratio (83.3 m/km), which represent the land has a steep slope. Maier and Habran sub-basin, gives the maximum runoff volume, peak discharge, runoff depth, and runoff velocity during the storms of March 2014 and March 2020. These sub-basins have high CN value, the biggest area, long stream length, and high stream numbers. The study ended with a set of recommendations that mitigate the flash flood risks.