## 4 Results  
### Quantitative Morphometric Analysis  
The largest area of the 15 studied catchments and sub-catchments was measured for catchment no. 1 (C1 = 1586.75 km\({}^{2}\)), while sub-catchment no. 1 was estimated as the smallest sub-catchment in the study area (SC1 = 68.34 km\({}^{2}\)) (Table 4; Figure 6). Based on [37], 10 catchments and sub-catchments were recognized as large catchments (greater than 100 km\({}^{2}\)), while five were considered as small catchments (SC1, SC4, SC5, SC6, and SC8 are less than 100 km\({}^{2}\)) (Table 4; Figure 6). Similarly, the largest catchment perimeter was recorded for C1, with a size of 295.55 km, and the smallest value was calculated for SC1, with a size of 44.98 km (Table 4; Figure 6). The measured lengths of the study zone ranged from 13.64 km (SC1) to 54.09 (C1). The largest catchment width was measured for C1 (35.71 km), while the smallest one was recorded for SC5 (5.64 km). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Catchments/** & **Area (km\({}^{2}\))** & **Perimeter (km)** & **Length (km)** & **Width (km)** \\ \hline C1 & 1586.75 & 295.55 & 54.09 & 35.71 \\ \hline C2 & 662.24 & 188.75 & 39.33 & 20.82 \\ \hline C3 & 859.14 & 229.69 & 48.57 & 33.39 \\ \hline C4 & 829.78 & 202.31 & 52.84 & 24.65 \\ \hline C5 & 749.01 & 189.46 & 45.50 & 27.25 \\ \hline C6 & 407.34 & 136.85 & 35.99 & 22.35 \\ \hline SC1 & 68.34 & 44.98 & 13.64 & 07.79 \\ \hline SC2 & 190.89 & 106.44 & 31.54 & 08.78 \\ \hline SC3 & 147.97 & 71.43 & 20.71 & 12.79 \\ \hline SC4 & 96.62 & 60.11 & 17.21 & 08.18 \\ \hline SC5 & 93.63 & 62.62 & 18.06 & 05.64 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Catchments geometry calculations of the study catchments and sub-catchments. \begin{table}
\begin{tabular}{c c} \hline \hline
**Equation** & **Abbreviation Description** \\ \hline T\({}_{\text{Lag}}=\text{L}^{0.8}(\text{S}+\text{I}_{\text{a}})^{0.7}/1900\sqrt{Y}\) \\ \hline T\({}_{\text{c}}=0.0001(\text{L}^{0.77}/\text{S}^{0.385})\) \\ \hline V = 0.2279 La/T\({}_{\text{C}}\) \\ \hline Qp = 0.208A/Tp & \multirow{2}{*}{T\({}_{\text{Lag}}\): lag time (h); Y: basin slope (\(\%\)); T\({}_{\text{c}}\): time of concentration (min); V: flow velocity; La: catchment length; Qp: peak discharge (m\({}^{3}\)/s); A: catchment area (Km\({}^{2}\)); Tp: time to peak (h); At: duration of designed storm; Q: direct runoff (mm); p: rainfall return periods (cm); S: potential maximum retention (mm); Ia: amount of total water before of flood; CN: curve number} \\ \hline Ia = 0.2S & \multirow{2}{*}{
\begin{tabular}{c} S = 1000 – 10 CN/CN \\ S = 25,400 – 254 CN/CN \\ \end{tabular} } \\ \cline{1-1} \cline{2-2} \end{tabular}
\end{table} 
Table 3: Computation methods of main flash floods parameters. Stream orders of the study catchments and sub-catchments vary from third-orders to sixth-orders. The dominant orders are the fifth and third-orders that were recognized for (C2-C6) and (Sc1, Sc4, Sc5, Sc6, and Sc8), respectively. The calculated orders are classified as follows: third-orders cover an area of about 6.81% of the entire studies zone, fourth-orders control around 11.17% of the catchments and sub-catchments, fifth-orders cover around 56.42% of the study zone, and finally, sixth-orders occupy an area of about 25.52% of the proposed zone. The total stream length of the study area reaches 5482.40 km. The stream lengths of the catchments and sub-catchments range from 55.80 km (SC1) to 1358.47 km (C1) (Table 5; Figure 7). The highest \(\rm R_{b}\) value is recorded for SC6 as 3.74, and the lowest value was estimated as 1.53 for SC4 (Table 5; Figure 7). The calculated stream frequency (F) of the entire studied zone is 9.41. The lowest value was recorded for SC1 at 0.497, while the highest value was recognized for SC2 at 0.701 (Figure 8). The drainage density values of the study catchments and sub-catchments ranges from 0.856 km/km\({}^{2}\) (C1) to 1.016 km/km\({}^{2}\) (SC3) (Table 5; Figure 8).