## 3 Case Study
### Multi-Targets Analysis  
(1) The 112 mm/1 h rainfall scenario  
The permeable pavement element of the low-impact development controls module in the stormwater management model hydrological model was used to simulate the base under the 112 mm/1 h rainfall scenario compared with the current surface runoff (93,744 m\({}^{3}\)) of the study base. The total surface runoff volume was reduced by about 47,196 m\({}^{3}\) (49.1%, shown in Figure 5), which also increased the infiltration area by about 14 hectares and improved the groundwater recharge. The current surface runoff of the base causes economic losses amounting to nearly NTD 3 million. After applying the general permeable pavement, the economic benefit can be reduced by about NTD 1,675,000 (44.2%). Compared with the original runoff in the 112 mm/1 h rainfall scenario, the total surface runoff volume can be reduced by about 33,624 m\({}^{3}\) (64.1%) using the JW \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Results** & **Scenario Events** & **112 mm/1 h** & **234.5 mm/3 h** & **350 mm/6 h** \\ \hline Peak (cms) & 9.33 & 16.52 & 17.65 \\ Total Volume (m\({}^{3}\)) & 93,774 & 188,352 & 270,360 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Comparison of the hydrographical simulation results of different short-duration intense rainfall events. ecological technology to simulate the base in the 112 mm/1 h rainfall scenario. The current surface runoff of the base causes economic losses amounting to nearly NTD 3 million. After applying JW ecological technology, its economic benefits can be reduced by approximately NTD 1.25 million (58.3%), which can effectively mitigate the negative impact of heavy rainfall. The summary comparisons of multi-targets are shown in Table 7.  
(2) The 234.5 mm/3 h rainfall scenario  
The 234.5 mm/3 h rainfall scenario was also compared with the current surface runoff (188,352 m\({}^{3}\)) of the base. The total surface runoff volume could be reduced by about 94,788 m\({}^{3}\) (49.6%, shown in Figure 6), increased the infiltration area of about 14 hectares, and improved the groundwater recharge. The current surface runoff of the base causes an economic loss of nearly NTD 7.9 million economic losses. After applying general permeable pavement, the economic benefits can be reduced by about NTD 3 million  
Figure 4: Flood damage estimation for residential area. Figure 5: Simulation result for 1 h/112 mm. (62.0%). Compared with the original runoff in the 234.5 mm/3 h rainfall scenario, the total surface runoff volume can be reduced by about 70,920 m\({}^{3}\) (62.3%) by using the JW ecological technology to simulate the base. The current surface runoff of the base causes an economic loss of nearly NTD 7.9 million economic losses. After applying JW ecological technology, its economic benefits can be reduced by approximately NTD 2.25 million (71.5%). (3) The 350 mm/6 h rainfall scenario  
The 350 mm/6 h rainfall scenario also compared with the current surface runoff (270,360 m\({}^{3}\)) of the base. The total surface runoff volume could be reduced by approximately 140,616 m\({}^{3}\) (48%, shown in Figure 7), increased the infiltration area by about 14 hectares, and improved the groundwater recharge. The current surface runoff of the base causes an economic loss of nearly NTD 9 million. After applying the general permeable pavement, the economic benefit was reduced by about NTD 600 500,000 (27.8%). Compared with the original runoff in the 350 mm/6 h rainfall scenario, the total surface runoff volume can be reduced by about 105,120 m\({}^{3}\) (61%) using the JW ecological technology to simulate the base in the 350 mm/6 h rainfall scenario. The current surface runoff of the base causes