# Research on Ecological Lawn Regulation and Storage System in Flight Area Based on Sponge Airport
## 3 Design of Ecological Lawn Regulation and Storage System in Flight Area  
Low-impact development (LID) [24; 25] is a concept that emphasizes small-scale and decentralized source control based on the concept system of the sponge city in order to achieve the goals of the total flow of rainwater runoff, the peak value of runoff, runoff pollution, waterlogging control, etc. LID facilities mainly include sunken green spaces, grass-planted ditches, rainwater gardens, green roofs, underground storage and infiltration, permeable pavements, etc. The sponge airport is different from other spaces in the sponge city in that hardened pavements account for a huge proportion and are prone to flood disasters in rainstorms. There is also a problem of high levels of COD (chemical oxygen demand), TN (total nitrogen), TP (total phosphorus), TSS (total suspended solids) [26] and other pollutants in rainwater runoff due to pollutants such as de-icing waste liquid, oil and chemicals in the flight area. During the construction of LID facilities, it is necessary not only to solve the problem of airport flood control and drainage but also to pay attention to the problem of initial rainwater pollution. In addition, airports have special requirements for operational safety, clearance and other aspects. During the construction of LID facilities in the sponge airport flight area, the presence of anything that affects airport clearance, such as tall vegetation and trees, is not allowed, and planting also needs to meet the requirements of bird-strike prevention [27; 28]. The characteristics of traditional airport flight areas are mainly covered by runways and green spaces, with a large area of lawn surrounding the runways and taxiways. Therefore, the low-impact development measures for the sponge airport flight area are suitable for choosing grass-planted ditches and sunken green spaces for the \"infiltration, retention, storage, purification, utilization, drainage\" of rainwater [29]. During light rainfall, a lawn with fine roots is able to increase the resistance of surface runoff and reduce the surface runoff. A retention channel is able to physically separate the surfaces of runways from the large area of lawn to quickly discharge the surface runoff from the surface of runways [30; 31]. A filter screen is equipped at the top of the retention channel [32] to reduce the initial rainwater runoff pollution. The inner side of the retention channel consists of permeable bricks and a water level sensor, which are used to capture the change in water level in the retention channel then feed back to the intelligent terminal and slowly release the retained rainwater to the surrounding area through the permeation effect of permeable bricks for a long time after the rainfall. During moderate rainfall, the water level sensor in the retention channel transmits the rising rate of the water level to the intelligent terminal in real time. If the rising rate of the water level is too fast, the  
Figure 3: Rainstorm hydrographs with different return periods. intelligent terminal will open the intelligent valve to discharge rainwater into the water storage module [33] through an overflow pipe. The water storage module also stores surface runoff, which is set below a sunken ground area and covered with coarse sand and large stones to reduce the phenomena of siltation and the overgrowth of weeds in traditional turfgrass ditches. The rainwater in the water storage module is purified and recycled to irrigate the lawn after the rainfall. During heavy rainfall, the water level sensor and the intelligent terminal indicate when the retention channel and the water storage module are unable to carry the total amount of rainfall. After the retention channel and the water storage module are full, the intelligent valve is opened to quickly discharge the overflow rainwater through the drainage pipes (Figure 4).