## 4 Results
### Flood Risk Assessment
On the other hand, catchments with high CN values are mainly composed of hard rocks and dominantly characterized by a large amount of runoff flow and a small amount of infiltration abstraction [61]. According to the SCS classification, major catchments (C1:C6) provide high CN values as 83.75, 82.36, 80.66, 82.50, 84.30, and 85.20, respectively (Table 6). CN results indicate that the majority of the study zone is expected to give high peak discharges. Because of the estimated large areas, the highest peak discharge is expected to be recorded for C1 (Table 6), but abnormally the highest values were recorded for C3 and C4 in 2009 storm and C4 during storm of 2019. Accordingly, this is the second recorded anomaly in the morphometric and hydrological calculations. The relief and slope indexes are very effective parameters for evaluating the intensity of flash flooding hazards, particularly in arid regions. Generally, steeper catchments provide suitable conditions for runoff water to be faster, more destructive, and produce higher catchment discharges. In the study area, the western strip is the highest subjected zone to flash floods because of the combining impervious soils and very steep slopes [36; 53]. The steep slope lands are characterized by high reliefs and relief ratios, in addition to low flow concentration time. During such strong storms, ref. [62] confirmed that the lower concentration flow time leads to more hazardous runoff. The relief of the major catchments ranges from 937 m (C5) to 1447 m (C2), while the concentration-time (T\({}_{\text{c}}\)) of the six catchments water flows give the lowest times for C6 and C2 (4.573 h and 5.592 h, respectively) and the highest time was recorded for C1 (7.72 h). Accordingly, C2 represents the most hazardous catchment with high relief and relief ratio values with low concentration-time (Tables 5 and 6). Total flood volumes are estimated based on the catchment area, catchments total stream length, and maximum peak discharges. Researchers in [36] applied geospatial analysis and a hydrograph model (HEC-HMS) in the WMS software to initiate flow hydrographs of flash floods in the Wadi Al Aaway drainage catchments in south Sinai. In addition, they used SCS unit approach to estimate the surface water and peak flow. They performed correlation analysis between many flood parameters that stated that, flood volume and peak discharge give positive consistency with the basin area, basin stream length, runoff depth, fellow velocity, and curve number. Authors in ref. [28] recommended constructing alternative barriers at some upstream parts to minimize flood risks, proposing storage dams, and initiating monitoring and warning systems. Authors in ref. [20] used Storm Water Management Model (SWMM) and WMS to initiate hydraulic and hydrologic model of the Aymmama River watershed in Istanbul. They concluded that integration of ArcGIS and WMS software is very effective in establishing hydraulic and hydrologic effective models and flash flood simulations. The hydrological characteristics of the major catchments stated that C4 has the maximum runoff volumes and the peak discharge during October 2009 storm event, while October 2019 storm provided the maximum peak discharge for C4 and maximum runoff volumes for C1 as an anomalous record (Table 6; Figures 10 and 11). CN and runoff velocity indexes of the major catchments provided relatively similar values, which lead us to consider these two values as minor effective values of the examined storm events (Table 6). The maximum area, longest stream length, and the highest total of stream numbers are recorded for C1 as 1586.75 km\({}^{2}\), 1358.47 m, and 1070, respectively (Tables 4 and 5). From the above discussion, integration between remote sensing technique, geospatial analysis, morphometric analysis, and hydrological modeling has proven that these methods are very effective for examining and assessing the different geological hazards [9; 10; 28; 56].