Application of Geographic Information Systems in Reducing the Risk of Flash Floods. Case Study Wadi Ghareb, Gulf of Suez, Egypt

Abstract

Egypt has deficit in water resources, so the optimal use from rainfall water is necessary. Egypt is exposed sometimes to accidentally flash flood hazards. In spite of flash floods led to damage to infrastructures, properties and loss of life but it can be used to harvest runoff flood. This study is based on integrated geologic, topographic and geophorphologic studies to prepare the required input data for different GIS layers such as: Digital Elevations Model (DEM), land forms, geologic setting, watershed characteristics, drainage lines, morphometric parameters, slope, flow direction and flow accumulation. Ras Ghareb city is one of the places which is subjected recently to heavy rainfall storms such as those occurred on December 2010, October 2016, February 2018, April 2019, March 2020, January 2022
with rainfall depth of 38.9 mm, 25.1mm, 17.01mm, 28.5mm, 39.8 mm and 60.48mm, respectively. Storm of December 2010, which caused a great damage in the study area, is selected to be analyzed. The HEC-HMS software is applied to estimate the peak discharge and runoff volume. The results show that the runoff volume of Wadi Ghareb is about 7.0357 million m3 year. Return period is expected to occur each 72 years with a probability of 1.35%, while a rain of 1.0 mm can occur every year with a probability of 94.59%. So, suggested tools of harvesting techniques for mitigation of flash flood hazard is recommended such as culverts under the asphaltic roads to protect it, detention dams to reduce velocity of flash flood and giving chance for replenishment of shallow aquifers. Also, earth dams can be used to allow the water to flow. Rain station is recommended to measure collected rainfalls.