"Sponge city" refers to taking a series of ecological, natural and low-cost measures in urban planning and construction to enhance the hydrological cycle capacity of the city and reduce the impact of floods and pollutants. For example, increasing wetlands, building reservoirs and rain gardens, as well as green roofs and three-dimensional greening. These measures can effectively use rainwater, thus reducing the load of urban drainage system, reducing the impact on the natural environment and improving the city's disaster resistance.