## 4 Results
### Flood Risk Assessment  
In this work, rainfall-runoff relationship was modeled from lag-time calculation and loss estimation methods. Many data such as DEMs, soil data, loss rate, base flow, and time concentration were combined to initiate the suitable hydrological models. The extracted runoff hydrographic curves for storms 2009 and 2019 are illustrated in Figures 10 and 11, and their hydrological results are tabled in Tables 5 and 6. In this study, the minimum value of the lag time was recorded for C6 (1.89 h), while its maximum value was calculated for C5 (2.46 h). The calculated concentration times were recorded as a lowest time for C6 (4.573) and a highest time for C1 (7.724). The water velocities of the study catchments are recording the lowest velocity for C5 (26.27 m/s) and the highest velocity for C6 (29.89 m/s). The peak discharge values (Qp) were calculated for the major six catchments and provide 117 m\({}^{3}\)/s and 70 m\({}^{3}\)/s for the storms of October 2009 and 2019, respectively. The peak discharge values of October 2009 were estimated to range from 36 (C2) to 113 (C4), while Qp values of the next studied storm event were recorded to range from 19 (C2) to 63 (C4). Finally, the flood volumes were estimated for the major catchments and provided 3,309,760.00 m\({}^{3}\) and 1,794,048.00 m\({}^{3}\) for October 2009 and 2019 storms, respectively. In October 2009, flood volume values recorded 250,048.00 m\({}^{3}\) and 831,488.00 m\({}^{3}\) for C2 and C4, respectively. 81,920.00 m\({}^{3}  
The present study investigates in details the flash floods risk assessment of one of the important Red Sea coastal zones. Discussing the morphometric analysis and hydrological characteristics of the catchments and sub-catchments between El-Qussier and Marsa Allam during October 2009 and 2019 storm events is the key for evaluating the flood risk levels and understanding the common behaviors of the similar storm events. The hydrological characteristics and related flash flood risks have been discussed in many different methods for several regions. The geomorphological hazards, including flash floods along the Egyptian Red Sea coast between Safaga and Quseir, were assessed by the study of [26]. The authors integrated geomorphological, geological, remote sensing, and climate data to confirm the paper results. The conclusion of the authors in Ref. [26] stated that the entire coastal line between Safaga and Quseir has been hit by floods frequently and these risks will accelerate based on different conditions. A study in [26] recommended proposing some dams to mitigate the effect of the flood risks. In [8] authors estimated the flash flood hazard along the Saint Katherine road in Sinai using morphometric analysis and remote sensing data. Morphometric analysis in [5] initiated a model that classified the catchments of the study area into high and low risks. While they recommended establishing a number of dams on the main channels, they believed that these dams might not stop the total flood water. A study in [21] processed seismicity and remote sensing data to compute the morphometric indexes in order to assess the geo-natural hazards of the region between Marsa-Alam and Abu Ghuson coastal line of the Egyptian Red Sea coast. In order to minimize the effect of flood risks and protect the urban regions, authors in ref. [21] recommended some strategies, including establishing dams in critical locations, particularly in wadis, and establishing any new projects away from the flooding courses. Quantitative morphometric analyses of the 15 catchments and sub-catchments were calculated to define the properties of the drainage systems of the study zone. Discussing the morphometric parameters of the study area is very valuable to understand the tectonic and geomorphic signatures of the different landforms [32; 37; 40]. The geometry indexes were calculated along the Red Sea coast to examine the natural hazard signals [21].