Porous pavement, also known as porous concrete, is a type of lightweight porous concrete made from aggregates, cement, and water. In sponge cities, the functional manifestations of ecological porous pavement include the following points:

1. Sponge City --- Retention

Capture the rainwater while respecting the natural terrain and topography, allowing rainfall to scatter naturally. With artificial constructions disrupting the natural landscape, water can accumulate in one place in a short time, leading to internal flooding. Therefore, it's essential to store the rainfall for regulation and peak-shaving purposes. Currently, there are no fixed standards or requirements for the water storage phase in sponge cities. The underground storage styles are diverse, with two commonly used methods: plastic module water storage and underground reservoirs.

2. Sponge City — Retention

Its primary function is to slow down the runoff of rainwater formed in a short period. For instance, by adjusting micro-topography, it allows rainwater to slowly accumulate in one place, trading time for space. By "retaining," it can delay the peak formation of runoff. The specific forms can be summarized into three: rainwater gardens, ecological retention basins, infiltration ponds, and artificial wetlands.

3. Sponge City - Pure

Soil infiltration, through vegetation, green spaces, and water bodies, all contribute to water purification. Therefore, it should be collected, treated, and reused in urban areas. Rainwater purification systems are set up differently based on regional environmental variations, which can generally be categorized into three types: residential area rainwater collection and purification, industrial area rainwater collection and purification, and municipal public area rainwater collection and purification. Based on these three types of regional environments, different rainwater purification stages can be established. Currently, the familiar purification process is divided into three stages: soil filtration purification, artificial wetland purification, and biological treatment.

4. Sponge City - Utilizing

Rainwater, after undergoing soil filtration, artificial wetland purification, and multi-layer biological treatment, should be utilized as much as possible, regardless of whether it's in water-rich or water-scarce areas. Strengthening the utilization of rainwater resources is essential. Not only can it alleviate flood disasters, but the collected water resources can also be utilized, such as using purified rainwater from parking lots for car washing. We should cultivate water through "infiltration," retain it in place through "storage," and then use it locally through purification.

5. Sponge City --- Drainage

By combining urban vertical structures with engineering facilities, integrating drainage and flood prevention systems with natural waterways, and merging surface drainage with underground stormwater channels, general discharges and excess rainfall are achieved, thereby preventing internal flooding and other disasters. Some cities experience internal flooding due to excessive rainfall. This necessitates taking artificial measures to drain off the rainwater.