## 4 Discussion  
There are several other methods commonly used for storm flow design. The selection of the method depends on several factors, including the project requirements, available data, and local regulations. Engineering references, guidelines, or local authorities are usually consulted to determine the most appropriate method to calculate the storm flow design in a specific location. According to this, no standardized methodology has been proposed in the literature. In addition, references generally do not include standardized \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Rational Method**} & \multirow{2}{*}{**Chow Method**} & \multicolumn{2}{c}{**SCS Method**} \\ \cline{3-4}  & & \multicolumn{2}{c}{**Hydrograph of Direct Runoff**} & \multicolumn{2}{c}{**Triangular Unit Hydrograph**} \\ \hline
8.07 & 4.569 & 6.371 & 2.964 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Flow rates calculated using the different methods (m\({}^{3}\)/s). \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Tr (Years)**} & \multicolumn{8}{c}{**Duration (min)**} \\ \cline{2-11}  & **5** & **10** & **15** & **20** & **30** & **45** & **60** & **80** & **100** & **120** & **1440** \\ \hline
2 & 115.85 & 89.26 & 73.91 & 63.74 & 50.90 & 40.01 & 33.49 & 27.90 & 24.15 & 21.44 & 3.99 \\
5 & 181.45 & 139.80 & 115.76 & 99.84 & 79.72 & 62.67 & 52.45 & 43.70 & 37.83 & 33.58 & 6.25 \\
10 & 231.08 & 178.03 & 147.42 & 127.15 & 101.52 & 79.81 & 66.80 & 55.65 & 48.18 & 42.77 & 7.96 \\
25 & 296.68 & 228.57 & 189.27 & 163.24 & 130.34 & 102.47 & 85.76 & 71.45 & 61.86 & 54.91 & 10.23 \\
50 & 346.30 & 266.81 & 220.93 & 190.55 & 152.14 & 119.61 & 100.11 & 83.40 & 72.21 & 64.10 & 11.94 \\
100 & 395.93 & 305.04 & 252.59 & 217.85 & 173.94 & 136.75 & 114.45 & 95.35 & 82.55 & 73.28 & 13.65 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Rainfall intensities (mm/h) for different return periods and durations. Figure 7: Intensity duration frequency curves. procedures for delineating urban basins, and consequently, the dimensions of their areas and even their shapes can influence the magnitude of rainfall-runoff. Some of the commonly used methods are the unit hydrograph method, soil conservation service (SCS) method, time of concentration method, rational method, and hydrologic models. The unit hydrograph method involves developing a hydrograph, which represents the flow rate of stormwater over time, based on the rainfall characteristics and the catchment's response [48]. The unit hydrograph is derived from the observed hydrographs to estimate the peak flow rate and hydrograph shape for a given storm event. The SCS method is commonly used in the United States and uses a hydrologic soil group classification system to estimate the runoff volume and peak flow rate [49]. This classification system is based on the soil properties, land use, and rainfall characteristics to calculate storm runoff. The time of concentration method is based on the time it takes for the entire catchment area to contribute runoff to a specific point [50]. However, several specific factors, such as flow path length, slope, surface roughness, and some hydraulic properties, must be provided to determine this time. Once the time of concentration is known, this time can be used to calculate the peak flow rate. The rational method provides an estimate of the peak flow rate and is based on several assumptions. It is commonly used for the preliminary design and sizing of stormwater management systems. It is used to estimate the peak flow rate of stormwater runoff from a given catchment considering the land use and surface characteristics, and the rainfall intensity obtained from local weather records and using rainfall intensity-duration-frequency (IDF) curves specific to the study area [51]. In addition, there are various hydrologic models available that simulate the rainfall-runoff process. These models utilize complex algorithms and data inputs to estimate the peak flow rate and hydrograph.