## 2 Study Area  
### Description of the Research Area  
The Egyptian Red Sea Coast is characterized by a long history of flash flooding catastrophes. On 27 and 28 October 2016, huge flash flood hit Ras Gharib City on the Red Sea coast and extended to cover some cities along the Nile River, it causes many deaths and injuries [21,24]. In October 2019, floods attacked the new Cairo City inside the capital of Egypt and caused 11 deaths and significant property damage [21]. This flood was reported as the most significant event during the last 50 years in terms of rising rates [25]. This flooding events started in August and increased in October, with a very intense rainfall rate [25]. In Lake Nasser, the water level has reached the highest level in comparison to the previous 50 years [25]. During the same year, particularly on November 14, heavy floods hit south Marsa Alam City in addition to Abu Ghosun village [21]. Extensive hydrological and flash floods assessments were applied with a focus on the Red Sea coast using different materials and techniques, e.g., [21; 26; 27]. Furthermore, in 2009, the first early flood warning system was installed in Egypt. This system contains different models for rainfall-runoff modeling, rainfall forecasting, and hydraulic modeling [25]. Egypt and its eastern desert reflect a large amount of sunshine, which averaged 3530 h in the long-term [28]. The average maximum temperature reaches 35 \({}^{\circ}\)C during July and August, while it could decreases to 10 \({}^{\circ}\)C in January and February [25]. The annual humidity ranges between 71% in summer and 53% in the wintertime [25]. Particularly, the Red Sea coastal line is characterized by strong winds that come from northwest regions [28]. In Hurghada region, the wind speed was estimated to be recorded at 5.5 m/s [25; 28]. The weather conditions data of the study area were collected from Data Access Viewer-NASA POWER ([[https://power.larc.nasa.gov/data-access-viewer/](https://power.larc.nasa.gov/data-access-viewer/)]([https://power.larc.nasa.gov/data-access-viewer/](https://power.larc.nasa.gov/data-access-viewer/)) (accessed on 16 May 2022)) in 2009 and 2019, respectively. It reflects 39.19% and 38.28% of humidity, 3.35 m/s and 3.84 m/s of wind speed, and 27.95 \({}^{\circ}\)C and 28.64 \({}^{\circ}\)C of average temperature, respectively. The study area occupies a coastal line zone of the western Red Sea coast of Egypt. It is located in the central-eastern desert between latitudes 24\({}^{\circ}\)50\({}^{\prime}\) and 26\({}^{\circ}\)15\({}^{\prime}\) N and longitudes 33\({}^{\circ}\)30\({}^{\prime}\) and 35\({}^{\circ}\)00\({}^{\prime}\) E (Figure 1), which covers about 6216.7 km\({}^{2}\). The coastal line between El-Qussier and Marsa Allam lies on the southwestern part of the Egyptian Red Sea Coast (Figure 1). It is located within a relatively high seismic region that is surrounded by the Gulf of Suez in the north, the Red Sea Mountains in the west, and active faults such as Kalabsha strike-slip Fault in the south. Marsa Allam City is known by a very productive gold mine (El-Sukari gold mine) and Wadi El-Gemal natural reserve. The study area is crossed horizontally by two asphaltic roads: Qifit--El-Qussier road in the north that extends for about 175 km between Qif City in the Nile valley and El-Qussier City along the Red Sea coast and southward, Edfu--Marsa Allam road that connects Edfu City in the west and Marsa-Allam City in the East for about 220 km. In addition, the study catchments are connected from north to south by the El-Qussier--Marsa Allam road along the Red Sea coast. The study area is covered by rocks from Pre-Cambrian to Quaternary (Figure 2). The climatic and hydrological conditions of the study area provide a wide range of mean rainfall amounts.