In recent decades, China's economy has taken off under the background of reform and opening-up. With the development of economy, the process of urbanization is speeding up. As a result, extreme rainstorms have occurred frequently and led to severe waterlogging in Chinese cities. This could also be attributed to damages to urban hydrology by rapid urbanization (Lyu et al., 2018; Xu et al., 2018). The destruction of hydrological environment has caused a series of problems of rainwater management and control, and many cities have serious waterlogging problems in flood season (Guo 2019; KUANG et al. 2018; YANG et al. 2021). According to the research, urbanization makes the rainfall runoff increase significantly, and the high proportion of impervious area will lead to the problem of heat island effect, more precipitation, less evaporation, decreasing water permeability, increasing peak flow rate and so on (Zhou et al. 2018; Jacob et al. 2019).
Airports are mostly built in areas where the terrain is flat. In order to ensure the strength of the pavement in the flight area, the proportion of hardened surfaces in the airport underlying surface is very high, rainwater can’t penetrate into the ground effectively. The underground soil layer should be compressed and compacted, so the impact of rainfall runoff is particularly obvious when encountering heavy rainfall. In addition, China's traditional airport rainwater drainage mainly relies on rapid drainage, and only relies on pipes and pumps. The natural hydrological cycle is destroyed by this drainage method, and it is proved that even the drainage pipe with the largest diameter can’t cope with the excessive runoff. At the same time, aviation oil pollution, heavy metals and solid suspended matter after the initial rain wash in a short period of time into the pipeline deposition, the downstream water surrounding the airport was contaminated. This draining-without-storing method wastes rainwater resources, and many areas suffer from severe waterlogging during the rainy season and severe water shortages during the dry season (Peng et al. 2020; Li 2018; Qu et al. 2020).
In 2018, the Civil Aviation Administration of China issued the Action Plan for building a strong civil aviation country in the new era, which calls for the building of safe, green, intelligent and people-to-people airports with high quality. In the same year, the Civil Aviation Administration of China issued a consultation circular on Green Airport planning guidelines as a Green Airport planning guide. The research and design of green airport construction has become an important and arduous task in the new era of civil aviation design industry in China (Liu 2019). A sponge airport is the airport has the function of infiltration, stagnation, storage, purification and drainage when it rains like a sponge, and it can "release" and utilize the stored water when the airport needs it (Peng et al. 2021). The construction of Sponge Airport conforms to the background of the development plan of the new-type Green Airport in China, which has the function of preventing and controlling the flood disaster, improving the water environment and water ecology around the airport. It can help to ensure the safe and efficient operation of the airport and was concerned by the Civil Aviation Administration and airports.
In the construction of Sponge airport, many airports use the methods such as increasing the green area of the airport, building large-volume water storage facilities and Green Roof to control the rainwater runoff, and emphasize the treatment and Reuse of rainwater resources. The O'Hare International Airports has installed 232,534 ft2 of vegetated roofs and is installing 126,456 ft2 more (as of November 2010). The installations demonstrate that installing vegetated roofs at airports is practical and cost effective. Operational and maintenance cost savings are expected from increased roof life span, energy use reduction, and storm water quantity/quality management. Additional benefits achieved include a reduction in noise and heat islands, air quality protection, and enhanced aesthetics (Peter 2011). Amsterdam Airport Schiphol combines solar energy with green roofs to save energy, protect the environment and beautify the environment, while alleviating waterlogging in the airport and saving rainwater resources (Kuller et al. 2017). The Singapore Changi Airport uses outdoor green roofs for rainwater storage and purification, an indoor waterfall landscape, and Vegetation Irrigation to reuse rainwater, part of the roof rainwater as well as reclaimed water is collected into the interior to form a four-waterfall landscape and irrigation water (Changi 2018).
The research on urban storm flood model is very extensive, and the representative models are SWMM, STORM, Mike Urban, InfoWorks ICM, SUSTAIN and so on. Each model has its own characteristics, applicability and limitations (Jiang et al. 2021). A new drainage system was designed using the Storm Water Management Model (SWMM) to collect and channel storm water runoff generated by the airfield as well as optimize the drainage system to protect the integrity of the runways and reduce maintenance costs (Amendolara et al. 2016). The different protection alternatives of Ronald Reagan Washington National Airport were examined to compare under storm conditions. The three alternatives are: permanent sea walls, temporary flood barriers, and an improved drainage design, namely increased out flow pump capacities. The output of the simulation is the time an airport stays flooded once a storm surge event is initialized as well as the time it takes for an airport, specifically it's drainage system, to drain enough of the flood to resume operations at normal rates (Haji et al. 2017). To address the problems of high overflow rate of pipe network inspection well and low drainage efficiency, a rainwater control optimization design approach based on a self-organizing feature map neural network model (SOFM) was proposed. Through the optimization adjustment of the pipe network parameters of Beijing Daxing International Airport, the overflow rate of pipe network inspection wells has reduced by 36–67.5%, the efficiency of drainage has increased by 26.3–61.7% (Qiu et al. 2020).
The low impact development facilities generally have infiltration, regulation, storage, transmission, interception, purification and other major functions, aiming to alleviate the detrimental impacts of urbanization and climate change and enhance resilience (KANG et al. 2017; Islam et al. 2021; Bonneau et al. 2021). In practical engineering application, the appropriate LID facilities and its combination should be selected according to the principle of local conditions and high economic efficiency, considering the regional hydrogeological conditions and water resources, and the analysis of economic indexes. Most of the existing research focuses on the construction of the pipe network model, the design of different types of LID facilities and their combination, layout location, layout area, and other scenarios. The optimal scheme of LID measures was designed to simulate the effects of different scenarios on runoff regulation and to consider the environmental, economic and ecological benefits (Liu 2017; Koc et al. 2021; Sheikh and Izanloo 2021).
In order to evaluate the effectiveness of different sponge airport control strategies, the runoff discharge of the rainwater drainage system in the airport under LID facilities and other measures was simulated. In this study, three scenarios were designed. There was no LID facilities and other measures in Scenario 1. In Scenario 2, two pump stations were set up at Reservoir 2 and Reservoir 3 to pump water from the storage to external river, in case of the possibility of storage flooding. There were applied both LID facilities and pump stations in Scenario 3. The storm with return period of 5a was designed as inputs into the developed models to compare the effects of different control strategies at different scenarios. The LID facilities include permeable pavement, vegetative swale and rain barrel. The simulation results analyze the variation of the inflow, the maximum depth and full-flow duration of reservoirs, the full-flow duration and the peak flow decrease of typical nodes and so on. This study laid a foundation for LID facilities design of sponge airport and the real-time flood control management of the rainwater drainage system.