## 1 Introduction  
The annual average rainfall in Taiwan is more than 2500 mm, which is 2.6 times more than the world average. However, it is distributed unevenly and is high in summer. Urbanization has caused an increase in impermeable areas in cities, population concentration, and a significant change in land utilization. Forests and agricultural coverage have decreased, and as the precipitation infiltration rate and groundwater resources goes down, the surface runoff increases. This increased runoff overloads the drainage system and may lead to inundation in low-lying lands. In rapid urban development, drainage system planning is spatially and financially restricted. [PERSON] et al. [1] opened that the natural phenomena must be followed with a continuous data collection. The results can be applied to engineering practice through statistical research. Engineering from the database and model results also explores whether existing constructions will be affected by the extreme weather event caused by climate change, such as the increase in average sea level, frequent heavy rainfall, drought, and landslide events. According to [PERSON] [2], the JW ecological technology of permeable pavement emphasizes laying a considerable thickness of gravel under the artificial pavement. With its water storage and water activation of the soil, its load capacity can be applied to the road pavements to withstand various vehicles ([PERSON], [PERSON]) [3]. The surface of permeable pavement has about 100 holes per square meter, and air-conditioning water pipes are used to provide rainwater penetration. [PERSON] et al. [4] indicated that low-impact development is a method of stormwater management, which detains runoff near its source by preserving natural landscape features and limiting impermeability. Their study also shows that the technique of low-impact development can reduce runoff of the maximum flow generated by stormwater. [PERSON] et al. [5] reported that under this circumstance, green roofs offer many benefits, including the simulation of on-site rainwater management with natural hydrological conditions of urban areas, which can retain large amounts of rainwater for extended periods and delay peak discharges. However, [PERSON] and coworkers also referred to fully developed areas where many old building structures may have already used vegetative roofs. Urbanization leads to increased runoff, leading to erosion, floods, and deterioration of the health status of river ecosystems. Although best management practices are widely adopted to control stormwater and runoffs, the low-impact development plan has been proposed as an alternative by utilizing a dispersed design to control stormwater and better simulate the natural flow. [PERSON] et al. [6] adopted the rainwater management model from the US Environmental Protection Agency (USEPA) to quantify the benefits of stormwater management and observed that rainwater harvesting can reduce runoff by 20% in semi-arid areas, while long-term simulations revealed that runoff was significantly reduced for heavy rainfall areas [7]. Overall, these results show that the cities in the U.S. and individual households can benefit from rainwater harvesting as a means of harnessing rainwater and alternative water source. On the other hand, the most applicable scope of low-impact development facilities is on single development basis. Hence, if land-use planning and detailed planning are included during the proposal stages, the overall benefits are more significant ([PERSON], J.-Y.) [8]. [PERSON] et al. [9] observed that the combination of low-impact development facilities also affected runoff characteristics and that the total runoff and peak runoff were significantly reduced by increasing retention capacities and permeable areas. Integrated planning can be carried out by utilizing professional help in groundwater conservation, such as hydrological analysis, flood potential analysis, etc., in conjunction with land use, allocation of runoff, etc.