## 3 Results and Discussions
### The Importance of Non-Geological Methods in Urban Flood Control
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Rainfall** \\ **Inensity/Return** \\ **Period** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Rainfall** \\ **(mm/d)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Storage** \\ **Rainfall** \\ **(10\({}^{6}\) m\({}^{3}\)/d)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Flood** \\ **Capacity of** \\ **Disprange** \\ **Capacity of** \\ **Disprange** \\ **Capacity of** \\ **Disprange** \\ **Disprange** \\ **Netwidth** \\ **(10\({}^{6}\) m\({}^{3}\))** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Reserved** \\ **Storage** \\ **Capacity of** \\ **Disprange** \\ **Network** \\ **(10\({}^{6}\) m\({}^{3}\))** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Storage** \\ **Capacity of** \\ **Disprange** \\ **Network** \\ **(10\({}^{6}\) m\({}^{3}\))** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Capacity of** \\ **Disprange** \\ **Disprange** \\ **Network** \\ **(10\({}^{6}\) m\({}^{3}\))** \\ \end{tabular} } \\ \hline Light rain & 10 & 27.50 & 7.86 & 27.91 & 62.57 & 7.79 & 106.13 \\ (upper limit) & 25 & 68.75 & 19.65 & 27.91 & 62.57 & 7.79 & 117.92 \\ Heavy rain & & & & & & \\ (upper limit) & 50 & 137.5 & 39.30 & 27.91 & 62.57 & 7.79 & 137.57 \\ Once a year & 76 & 209.00 & 59.74 & 27.91 & 62.57 & 7.79 & 158.01 \\ Rainstorm & & & & & & \\ (upper limit) & 100 & 275.00 & 78.60 & 27.91 & 62.57 & 7.79 & 176.87 \\ Once in 3 years & 111 & 305.25 & 87.25 & 27.91 & 62.57 & 7.79 & 185.52 \\ Once in 5 years & 127 & 349.25 & 99.82 & 27.91 & 62.57 & 7.79 & 198.09 \\ Once in a decade & 149 & 409.75 & 117.11 & 27.91 & 62.57 & 7.79 & 215.38 \\ Once in 30 years & 184 & 506.00 & 144.62 & 27.91 & 62.57 & 7.79 & 242.89 \\ Once in 50 years & 200 & 550.00 & 157.20 & 27.91 & 62.57 & 7.79 & 255.47 \\ Once in a century & 222 & 610.50 & 174.49 & 27.91 & 62.57 & 7.79 & 272.76 \\ Once in 200 years & 244 & 671.00 & 191.78 & 27.91 & 62.57 & 7.79 & 290.05 \\ Heavy rainstorm & & & & & & \\ (upper limit) & 250 & 687.50 & 195.68 & 27.91 & 62.57 & 7.79 & 293.95 \\ Once in 500 years & 273 & 750.75 & 195.68 & 27.91 & 62.57 & 7.79 & 293.95 \\ Once in a millennium & 295 & 811.25 & 195.68 & 27.91 & 62.57 & 7.79 & 293.95 \\ The 3-day rainfall of the “720” & 617.1 & 1697.03 & 195.68 & 83.73 & 62.57 & 7.79 & 349.77 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Non geological methods for assessing the drainage capacity of rainwater and floods in the study area. Table 6 shows that the combined action of geological and non-geological methods can almost solve the rain and flood-related problems caused by rainstorms in the study area, and geological methods can take a 33.56% share of the prevention and control of floods. However, these methods are insufficient to meet the requirements if the rainstorms are larger. In the case of preventing floods caused by heavy rainstorms, geological methods account for more than 30%, and the greater the rainfall intensity, the greater the proportion of drainage capacity of geological methods. For the \"720\" torrential rainstorm in the study area, the two methods taken together account for only a combined share of 49.14% in controlling the flood disasters. If the geological, ecological, and hydrogeological conditions are not fully utilized, and if the engineering aspects of sponge city construction are not followed, the situation could be different for the study area. If so, the impounding capacity at the source of the Jialu River will be reduced by 3.28 million m\({}^{3}\), and the seepage volume will be reduced by 14.53 million m\({}^{3}\) per day. This will lead to a sharp decline in the amount of rainwater and flood infiltration in the sponge construction area of the city, reducing its flood control capacity. As shown in Table 6, the flood control capacity achievable through a combination of geological and non-geological methods will be reduced from rainstorm to heavy rain.