## 3 Results and Discussion
### Analysis of Model Optimization Results  
The optimization results reveal a significant annual decrease in internal flooding events. This suggests that implementing an upgraded drainage system and low-impact development (LID) strategies have greatly improved the area's flood prevention capabilities. The study considered a combination of LID measures, such as permeable pavements and rain gardens, alongside traditional infrastructure upgrades, including new stormwater mains, additional drainage branches, and stormwater storage ponds. The optimal solution, \begin{table}
\begin{tabular}{c c c} \hline
**Index** & **Pre-Optimization** & **Optimized** \\ \hline Average duration of waterlogging (h) & 7.43 & 3.12 \\ Average water depth (cm) & 21.27 & 8.65 \\ Drainage efficiency (\%) & 58.32 & 91.46 \\ Reduction of peak flood flow (\%) & 0 & 25.38 \\ Surface runoff reduction & 0 & 20.16 \\ Increase of soil water content & 0 & 15.98 \\ Amount of increase in groundwater recharge & 0 & 17.32 \\ Utilization rate of rainwater & 61.84 & 77.14 \\ Failure rate of drainage system & 5.15 & 1.86 \\ \hline \end{tabular}
\end{table} 
Table 4: Drainage capacity condition. derived through the genetic algorithm, incorporated a mix of these measures to achieve maximum drainage efficiency. Specifically, stormwater storage ponds, permeable pavements, rain gardens, and the construction of new stormwater mains were prioritized in the final solution. The shorter duration of flooding indicates that the enhanced drainage system can move water away more efficiently, reducing the impact on residents and economic activities. Notably, during heavy rainfall periods, a quicker drainage response helps limit disruptions to traffic, daily life, and infrastructure. A reduction in the average water depth further supports the idea that the area's overall drainage capacity has improved, leading to better conditions during heavy rains and easing the strain on daily travel and activities. Enhanced drainage efficiency means that the optimized system can now remove precipitation more swiftly and limit water accumulation, even under similar rainfall levels. This improvement is the result of expanding and renovating the drainage network and installing rainwater storage tanks to alleviate pressure on the system during peak flows. The reduced peak flow suggests that the improved system can better manage and delay runoff during intense rainfall, which decreases peak flow rates. Implementing LID measures like rainwater storage tanks and permeable paving helps rainwater infiltrate and be stored more effectively, reducing pressure during peak flow events. The reduction in overall rainfall runoff shows that, by using LID measures and optimizing the drainage network, a larger portion of rainwater is being absorbed and stored instead of converting directly into runoff. This not only reduces flood risks but also supports groundwater recharge and helps maintain ecological balance. The decrease in surface runoff indicates that more rainwater is being intercepted and absorbed through LID measures like rain gardens and permeable paving, leading to a reduction in direct runoff formation. This improvement helps mitigate flooding risks and protect surface water resources. The increased soil moisture levels suggest that greater rainwater infiltration is enhancing the soil's moisture content, thereby supporting plant growth and strengthening the ecosystem's stability and resilience. The increased groundwater recharge indicates that more rainwater is seeping into the ground to replenish groundwater reserves, which strengthens the region's water resources. Groundwater recharge also plays a critical role in sustaining the balance of rivers and wetlands. Likewise, greater utilization of rainwater points to better effectiveness through LID practices and rainwater harvesting, reducing dependence on municipal water and lowering the burden on the drainage system.