Hydraulic Engineering Office

Due to rapid urbanization in Taipei City in recent years, there have been many construction projects, resulting in increasing impervious areas and loss of water retention capacity on the ground surface. Not only has the city's ability to retain water been reduced, but the amount of surface runoff from heavy rainfall has also increased significantly. In order to solve the problem of insufficient water retention and water permeability and reduce the risk of flooding, the Hydraulic Engineering Office (HEO) has adopted engineering management to improve the city's flood carrying capacity.

Fulin Road located between Jiantan Mountain and the urban road,that is, the midstream of the rain water sewer system. Jiantan Mountain is big and the steep, when instant heavy rainfall occurs, the puddle at Fulin Road is getting worst. HEO has adopted the integrated flood management and flood mitigation strategy to improve the flood detention project. For example, in the Wenshan District, the HEO has constructed the flood detention basins in the Xinhai Ecological Park and the north side of the Wenshan Sports Center, thus significantly reducing the risk of flooding in the Wenshan District.

HEO has received several puddle reports from citizens around the Chiang Kai-shek Shilin Residence (Shilin Residence) since 2012. After observing and reviewing the cases, the reason for causing puddle is that the drainage capacity of the open gutter at Shihlin Residence is not enough to accommodate the runoff from Jiantan Mountain, the north and south sides of Fuhlin Road, and the surrounding watershed. The side ditches, stormwater wells, and connecting pipes in the area are all ultimately discharged to the gutter. Being the only large-scale drainage facility in the area, this is a tremendous challenge. Imagine turning on the faucet all the way, the pipe below the sink cannot drain the water immediately, then the sink will accumulate water in 5-10 cm high, and eventually the water will be slowly drained and gone; similarly, the sudden heavy rainfall would cause the water level in the open gutter to be higher than water return, which would cause the surrounding side ditches, rainwater wells, and connecting pipes not be able to drain. In this case, the terrain of the Section 5 of Zhongshan N. Rd. and the intersection of Fulin Road is considered to be the lowland, so the puddle condition is most severe.

The goal of building the Shilin Residence detention basin is to solve the problem of insufficient capacity in the Shilin Residence open gutter that absorbs 23.73 hectares of watershed on the north and south sides of Jiantan Mountain and Fulin Road. It is not just to collect the puddle in the lowland area. Together with the results of the pipeline survey to avoid Taipower ultra-high voltage, HEO has chosen a green space next to the Fulin Road and Lane 100 of the Fulin Road to set up a detention basin. The area of the basin is about 1,700 square meters, with a planned flood retention volume around 600 cubic meters in the upper basin and 10,400 cubic meters in the lower basin, the aggregate flood retention volume is about 11,000 cubic meters. The renovated detention basin includes an upper basin and a lower basin. The upper basin is surrounded by green space, pond, trails, plants, and recreational space. The space is more effectively utilized than the existing condition. Based on the energy-saving and carbon-reducing principles, we reuse the old concrete blocks for pavement and styling chairs, use permeable bricks for the sidewalk pavement and install rainwater retention bricks underneath, reuse the granite slabs, recycle the water in the detention basin, plan for solar panels to provide power for the circulation machine in the upper basin, and subsidize the water ladder on the south side to create the image of terraced fields, so the water can always flow and be exposed to the sun. Due to the deep excavation in the lower basin, the construction contractor will carefully apply soil retaining support when building the slurry wall. Prior to start construction, adjacent buildings will be assessed by a certifying authority. During construction, monitoring devices will be set up to monitor the site to ensure the structural safety of the adjacent buildings.

The "New Construction of North Side Detention Basin of Shihlin Residence" was commenced on March 14, 2024; the construction will last for 750 days, and is expected to be completed in early April, 2026. The total cost of the project is NT$460 million. We expect the detention basin will enhance the rainfall carrying capacity to 88.8mm/h which is the standard for flood control after the completion of the project.