Sponge city practice in China: A review of construction, assessment, operational and maintenance

As the global climate change and the rapid progress of urbanization, the frequent occurrence of flooding disasters and non-point source pollution seriously threaten the sustainable development of modern cities. To alleviate these problems, China started to pilot construction of the “Sponge City” (SPC). Over a decade, it has attracted public attention, supports, and participations. The paper presents a literature review of sponge city construction (SPCC) process (planning, design and construction) as well as the assessment of SPC, including: operation, maintenance, and effectiveness. Research gap and future works are also proposed. The paper offers some tactics for SPCC, including: 1) in the planning and construction stage of SPC, the goals and systematic plans should be formulated according to local water-environmental conditions. The drainage plan should cover the strategy to dispose runoff volumes at sources and the ultimately goal for flood mitigation. The drainage design involves the combination of various green and grey infrastructures; 2) It is important to identify monitoring methods and hydrological models which can be used to assess the performance of a SPC. With adequate field data, all models and methods should be calibrated for not only runoff quantity and quality control but also the alleviation of urban heat island effects, including the base flows and local groundwater table; 3) Based on the regional field data, it is necessary to standardize regional design parameters, construction material specifics, and maintenance scheme and schedule that would significantly affect the facility's infiltrating and filtering processes, therefore, a regular maintenance program should be initiated to monitor the operations of the as-built facilities according to local climate conditions. The paper evaluated several maintenance methods for ten typical facilities to provide a reference for the operation and maintenance of facilities in SPCC.