Due to the effects of global warming and rapid urbanization in recent years, urban rainstorm events are becoming more frequent [1
], and are occurring at the same time across the world, resulting in a high risk of urban rainstorms and flood disasters [4
China is a high-risk, flood-prone area when it comes to the frequency of global flood-causing factors [7
]. It is estimated that the global economic exposure to rainstorms and floods will increase to USD $
158 billion by 2050 [7
]. “Waterlogging every rainstorm” has become a significant problem in the sustainable development of large- and medium-sized cities in China [8
]. It has led to serious economic losses, casualties, and various kinds of urban operation risks, arousing strong concern from society [12
]. Global warming, rapid economic growth, poor infrastructure, lack of urban planning and design concepts, insufficient comprehensive regulations and control ability of river basin systems, paralytic thinking and fluke mentality in urban disaster prevention and, finally, heavy rain, can destroy the defense capabilities of a city, and lead to large-scale urban waterlogging [13
]. For safe and healthy development of a city, urban rainstorm waterlogging needs to be improved and solved by comprehensive measures [17
Two-thirds of China’s land area is presently at risk of flooding [18
]. About 62% of more than 500 cities in China have experienced urban rainstorm waterlogging disasters in recent years [19
]. Among them, 137 cities have suffered from rainstorm waterlogging more than three times, and 57 cities have accumulated water for more than 12 h [20
]. Moreover, there were 184 cities in China experienced waterlogging in 2012; 234 in 2013; 127 in 2014; 154 in 2015; 183 in 2016 [21
]. In general, rainstorm waterlogging disasters in China are more serious in the south than in the north, more serious in the mid-east, especially in the eastern urban agglomerations, and light in the west [22
]. The rainstorm waterlogging disaster in China is becoming more serious [25
], and the situation is not optimistic.
Considering the background of severe rainstorm waterlogging, how to better understand the natural and human causes of rainstorm waterlogging in China is not only the focus of academic circles [32
], but also the basic work of the government (i.e., to carry out rainstorm waterlogging control). It is also one of the important aspects of this paper. Regarding natural, man-made factors, this paper first analyzes the potential factors causing rainstorm waterlogging in China. Then, based on the international model of urban rainstorm waterlogging management, their advantages and typical characteristics are analyzed. Combined with the sponge city construction policy proposed by China, to solve the problem of urban rainstorm waterlogging, this paper analyzes the main problems faced by China in promoting the construction of a sponge city. On the basis of the above analysis, this paper finally provides policy suggestions for the Chinese government to control urban rainstorm waterlogging, and expounds China’s experiences in controlling urban rainstorm waterlogging, which may be of reference value to other countries and regions in the world (Figure 1
4. Main Problems of Sponge City Construction in China
The first problem of a sponge city construction in China is the construction of an urban rainwater recovery system (Figure 3
). An urban rainwater recovery system is an important part of sponge city construction. In 2006, the Ministry of Housing and Urban Rural Development issued the “Technical Code for Rainwater Utilization in Buildings and Residential Quarters”, which aims to promote the scientific development and construction of an urban rainwater recovery system in China, so as to obtain comprehensive economic, social, and environmental benefits [21
]. However, at present, the scale (and construction) of an urban rainwater recovery system is affected by many aspects of urban construction and development in China; the urban rainwater recovery system has not really been built or played its role in China [37
]. Moreover, the urban rainwater recovery must deal with pollutants. At present, the construction of an urban rainwater recovery system in China has not been mentioned in the national policy [27
The second problem of a sponge city construction in China is the construction of urban rainwater storage facilities (Figure 3
). In China, urban land is precious and scarce [30
]; thus, how to scientifically plan and effectively use urban rainwater storage facilities is key. The core issue is that the type, scale, and quantity of urban rainwater regulation and storage facilities have not been reasonably demonstrated. Therefore, the implementation of urban rainwater regulation and storage facilities is affected. In addition, the lack of awareness of the natural geographical pattern in the existing urban construction in China has led to the continuous emergence of facilities, such as a sunken overpass, which also has a negative impact on the construction of a sponge city [43
The third problem of a sponge city construction in China is the construction of a data platform (Figure 3
). Sponge city construction involves information data sharing and integrating data across departments. In China, this generally includes a transportation department, urban construction department, hydrological department, meteorological department, civil affairs department, emergency management department, public finance department, etc. [44
]. Although the concept of a sponge city has been put forward—for many years—in China, an official website that integrates data across departments, has not been built. How to cooperate with multiple departments in sponge city construction is not only a policy level matter, but also concerns determining internal functions and responsibilities, which need to be considered as a whole.
5. Key Points, Guiding Principles, and Policy Suggestions for the Chinese Government to Solve Urban Rainstorm Waterlogging
It is necessary to abide by the principle of urban sustainable development to deal with urban rainstorm waterlogging. Based on the above diversified causes of urban rainstorm waterlogging in China, international governance experience and problems faced by sponge cities in China, the effective governance of urban rainstorm waterlogging in China not only requires changing the concept of urban rainstorm waterlogging governance from the height of top-level design, and upgrading it to the height of national construction and governance, but also requires learning and absorbing the advanced ideas and practices of urban rainstorm waterlogging governance in the world [43
]. At the same time, in practice, the Chinese government should cooperate with various forces of urban governance, gather consensus, and create a joint force, to effectively control urban rainstorm waterlogging (Figure 4
First, to deal with urban rainstorm and waterlogging, the Chinese government should coordinate the coping with climate change and ecological civilization construction (Figure 4
). Simply dealing with climate change cannot meet the needs of urban system operations. Urban areas should promote the control of waterlogging to the height of ecological civilization construction, take climate change as the starting point, pursue advantages, avoid disadvantages, and follow scientific planning, to ensure the long-term stability of a city. China’s ecological civilization construction policy essentially requires efforts to promote green development, circular development, and low-carbon development; adhere to the basic national policy of saving resources and protecting the environment, and adhere to the policy of giving priority to conservation, protection, and natural recovery [44
]. China’s ecological civilization construction policy should not only involve its own ecological construction, environmental protection, and resource conservation well, but also include it in a prominent position, in national development, and integrate it into all aspects (i.e., the whole process of economic construction, political construction, cultural construction, and social construction), which means that the construction of ecological civilization is not only parallel with economic construction, political construction, cultural construction, and social construction, but also in a comprehensive way, in order to form the five major constructions, The Chinese government should integrate the concept, viewpoint, and method of ecological civilization into the process of economic construction, political construction, cultural construction, and social construction. The above objectives of China’s ecological civilization construction policy provide a solid theoretical basis, top-level design, and policy support for coping with the risk of climate change, especially urban rainstorm and waterlogging. Therefore, the first problem to be solved in China’s current urban rainstorm waterlogging is the change of governance concept—that is, to coordinate the response to climate change and ecological civilization construction [43
Second, in regards to China’s sponge city construction, foreign experience needs to be studied (Figure 4
). Foreign urban storm water management technology has advantages of conforming to local policies and environments. It is necessary to study foreign governance paradigms of urban rainstorm waterlogging, develop sponge city construction technologies and schemes suitable for different regions, establish a perfect rainstorm waterlogging management system, and effectively improve urban resilience.
Third, the Chinese government should unite multiple subjects, integrate multiple elements, design multiple processes, form a joint force, and create an all-around response system to deal with urban rainstorm waterlogging (Figure 4
). Through construction, communication, coordination, and cooperation, a top-level design is carried out. From the response concept of urban rainstorm waterlogging, scientific fortification, multi-participation, and sponge city construction, multiple elements are integrated to achieve advantages and avoid disadvantages. At the defense level, we should cooperate with governments, institutions, enterprises, and individuals at all levels to actively participate in the construction of a sponge city, and effectively deal with urban rainstorm and waterlogging.
Based on the above guiding principles, the government needs to take specific policy recommendations as follows in China:
Firstly, the government needs to establish the idea of “fighting a protracted war” of urban rainstorm and waterlogging (Figure 5
). The current urban waterlogging problem in China cannot be solved in a short-time. With the process of climate change and urbanization, the problem of urban rainstorms and floods in China will become more prominent. Therefore, it is necessary to do a good job in top-level design, system formulation, long-term construction, maintenance, and operation preparation for urban waterlogging control. At present, it is critical to establish a basic rainwater and sewage diversion system, and reconstruct the rainwater pipe network and drainage pump station in key areas. The government should pay back historical debts as soon as possible, treat the symptoms and root causes, get rid of the state of “waterlogging every rain”, and gradually achieve the goal of no-ponding in light rain, no waterlogging in heavy rain, no black and smelly water bodies, and relief of urban heat islands.
Secondly, the city should improve the defense standard and encourage society to participate in the management of urban rainstorm waterlogging disaster risk (Figure 5
). Combining the experience and technology of urban rainstorm flood control construction from foreign countries with the actual situations of urban rainstorms and floods in China would involve reasonably improving the drainage design standard, scientifically planning the construction of an underground corridor, and avoiding the old development road of “above ground first and then underground”. In addition, relying solely on government funding to construct a drainage pipe network places great pressure on China’s economic development. Therefore, it is suggested that, while the central, provincial, and municipal governments finance the construction of an urban underground pipe network, various financial means, such as insurance, funds, and bonds, should be used to promote the construction of the project, and social capital should be encouraged to participate in the construction of a sponge city.
Thirdly, the government should promote the construction of a high-quality sponge city (Figure 5
). The concept of a sponge city is put forward to solve the problem of urban waterlogging. According to its concept, urban planners should start the construction of roof rainwater collection systems as soon as possible, promote sponge type buildings and communities, sponge roads, and squares, and promote the construction of green space parks and natural ecological restoration. It would not only absorb and utilize more rainwater on site, and reduce rainwater discharge in the drainage network, but also save thousands of cubic meters of tap water for toilet flushing, reduce waterlogging, and save water—effectively achieving a win–win situation.
Fourthly, the government should strengthen the scientific demonstration of comprehensive and systematic planning of large- and medium-sized cities (Figure 5
). On the one hand, the original natural river network survey is carried out, on the other hand, the urban micro topography and geomorphic fluctuation changes are investigated. The impact of large-scale road and bridge construction on local disasters is evaluated, and the harmonious coexistence of urban development and natural geographical patterns are emphasized. At the same time, new technologies and new materials should be used in urban construction to promote industrial upgrading and transformation, effectively improve the fortification level of infrastructure, promote the transformation and relocation of villages in cities with prominent security problems, and enhance the comprehensive disaster prevention capacity of vulnerable areas.
Fifthly, the government should improve disaster monitoring, early warning, and forecasting system (Figure 5
). The first is to carry out large-scale investigations of natural disaster risks, and compile a large-scale comprehensive natural disaster risk assessment and zoning map of the whole city. The government should carry out the general survey and detailed investigation on the hidden danger points of urban waterlogging, plain flood discharge areas, ancient river channel areas, mountain torrents, collapses, landslides, debris flows, and earthquake hazard sources in mountainous areas, and compile account books. It is critical to establish and improve the comprehensive natural disaster monitoring and forecasting early warning network systems by using the modern internet of things, high-precision remote sensing, a geographic information system, and communication technology, as well as a group survey. It is urgent to establish and regulate a unified reporting channel of natural disaster information by provinces, cities, districts, streets, and communities, and acknowledge the important role of grassroots community organizations in regards to disaster information early warnings, disaster statistics, and verification, to ensure timely and accurate reporting of disaster information.
Sixthly, it is critical to strengthen the construction of the metropolis’s capacity to cope with a catastrophe (Figure 5
). It is crucial to improve the construction system of an urban lifeline access capacity and warning system under catastrophic disaster conditions. At the same time, it is necessary to establish the risk assessment system (of a lifeline system) under catastrophe conditions, and formulate a catastrophe response plan for the metropolitan area. In urban planning and construction, it is necessary to integrate the two major constructions—of lifeline accessibility and warning—to promote urban development and the construction of a comprehensive disaster prevention plan. Focus on the case study of heavy and special natural disasters, use scenarios and simulation technology to formulate emergency plans for serious and special natural disasters, and objectively evaluate the ability and effect of an urban lifeline system to cope with catastrophic disasters.
Seventhly, it is imperative to enhance the long-term, sustainable, and institutionalized awareness of urban planning of decision makers at all levels (Figure 5
). On the one hand, once scientific urban planning is approved, it must be stipulated in the form of legislation. If there is no major accident, it cannot be changed at will to ensure the continuity of urban construction; even if it must be changed, it needs to be evaluated by a third party appointed by higher authorities. At the same time, urban decision makers should improve their understanding of urban construction, and incorporate it into the national strategy of ecological civilization construction. On the other hand, the relevant business management departments should scientifically prepare flood risk maps, formulate risk assessment and emergency plans for catastrophic floods, including reservoir optimal operation plans, reservoir dam break risk identification, emergency plan management of engineering and non-engineering measures, personnel risk avoidance, transfer methods, etc., which is an insurmountable task for urban development. At the same time, the government should make full use of modern information technology and model means to improve the intelligence and credibility of decision-making.
Eighthly, it is urgent to strengthen the awareness of disaster risk prevention and cross regional disaster risk coordination (Figure 5
). First, strengthen education. In schools, we should strengthen disaster prevention and mitigation education, compile teaching materials, train teachers, increase disaster prevention, and reduce education hours. In communities, we should popularize disaster knowledge, improve risk prevention awareness, be familiar with disaster risks in the jurisdiction, master escape skills, and understand the setting and use of surrounding shelters and related disaster prevention and mitigation facilities. Secondly, to use traditional and new media, such as television, radio, and microblogging to carry out regular disaster prevention and mitigation publicity activities, so that the public cannot only understand the level of various disasters in the forecast information, but also understand how to deal with such disasters, and understand the meaning of various disaster warning signs. Thirdly, to establish the concept of urban safety development, which is to be prepared for danger in times of safety, to improve the public’s psychological ability to bear and deal with natural disasters, to minimize the loss of disasters. We should strengthen the coordination of cross regional disaster relief/risk prevention efforts, strengthen the construction of natural disaster rescue command systems and disaster relief material (regarding emergency support capacity), and improve and strengthen the construction of grassroots disaster relief teams and disaster relief emergency equipment.
6. Insights of China’s Governance of Urban Rainstorm Waterlogging to the Global Audience
Urban rainstorm waterlogging is the result of the interactions among climate change and rainstorms, urban development planning and concepts, and waterlogging prevention facilities and human activities. China’s urban rainstorm waterlogging control has some aspects that are worthy of reference and learning (from a global audience)—from a governance concept to specific practice.
First, China implements more comprehensive and scientific ecological civilization construction (regarding urban rainstorm waterlogging control). Human beings need “self-revolution” to accelerate the formation of the green development mode and lifestyle, to build an ecological civilization and a beautiful earth [45
]. One of the key directions in the construction of an ecological civilization is to actively deal with the integration of climate change and green city development. It focuses on system planning to promote the integration of strategic planning, to highlight synergy (to promote the integration of policies and regulations), and to lay a solid foundation to promote the integration of the system. The construction of an ecological civilization requires that, in the face of resource constraints, serious environmental pollution, and ecosystem degradation, we must establish the concept of an ecological civilization that respects, conforms to, and protects nature, following the path of sustainable development. Therefore, the construction of an ecological civilization has become China’s national strategy to deal with the climate change risk, including urban rainstorm waterlogging, and it is also one of China’s plans to deal with the risk of global climate change [43
Second, a sponge city construction concept proposed by China involves a new generation of urban stormwater management, which aims to make cities as flexible as sponges in adapting to environmental changes and natural disasters brought by rainstorms. Starting from ecosystem services, the core of a sponge city is to build water ecological infrastructure through cross-scale construction, combined with various specific technologies. A sponge city is an innovative performance of promoting green building construction, low-carbon city development, and smart city formation. It is an organic combination of modern green new technology and social, environmental, cultural, and other factors under the background of global change. The construction of a sponge city follows the principle of ecological priority, which combines natural ways with artificial measures [44
]. On the premise of ensuring the safety of urban drainage and waterlogging prevention, it can maximize the accumulation, infiltration, and purification of rainwater in urban areas, and promote the utilization of rainwater resources and ecological environment protection. The construction of a sponge city is not to replace the traditional drainage system, but to “reduce the burden” and supplement the traditional drainage system, to maximize the role of the city itself. In the construction of a sponge city, the systematicness of natural precipitation, surface water, and groundwater, the coordination of water supply, drainage, and other aspects of water recycling, and the consideration of its complexity and long-term nature are coordinated [27
]. Therefore, sponge city construction is a concrete plan for China to promote green urbanization, providing a reference for the construction and development of cities across the world, especially in developing countries [43
Dealing with urban rainstorm and waterlogging has become one of the prominent problems faced by urban security development, and its governance involves different levels of problems. From a global perspective, effective response to climate change and its disastrous impact is related to human well-being and sustainable development. How to gather the consensus of all countries in the world and form an effective mechanism to deal with global climate change is still a difficult problem for policymakers in all countries. Because climate change itself has the characteristics of space–time difference, the adverse impact on some areas may be small or favorable in a short-time. However, in the long run, climate change is not conducive to the well-being of human beings. Human society should form a consensus to deal with climate change and cooperate to implement countermeasures as soon as possible. From the regional level, under the background of global climate change, how to give consideration to the scientificity, long-term, and predictability of urban development, and how to formulate a strategic plan in line with regional sustainable development, is a development problem that policymakers of all countries must face. Urban rainstorm waterlogging, as a product of natural and human factors, needs top-level design at the institutional level. At the local level, how to systematically promote the construction of a sponge city, systematically solve the problem of urban rainstorm waterlogging, and promote the development of a local economy, requires multi-disciplinary system thinking.
Based on the above analysis, we think that we can carry out relevant research and practices from management concepts, legal policies, applications in planning, and technical levels. In terms of management concept, we should adhere to the basic principles of sustainable development, close to the natural state and multi-functional urban stormwater management concept, change the separate flood discharge and waterlogging storage mode, and form a multi-functional management mode of flood control and disaster reduction, pollution control and prevention, water ecosystem restoration and protection, and urban environmental beautification and comprehensive utilization of water resources. In terms of laws and policies, we should build an efficient urban rainwater management system, formulate laws and regulations on urban rainwater utilization and management, adjust the coordinated management mode of urban rainwater and flood, change the chaotic management situation of water control, implement the integrated construction of water affairs, and ensure the implementation and promotion of sustainable urban rainwater and flood management technical scheme. In terms of application and planning, according to the comprehensive urban planning, the development of population, economy, resources, and ecological environment shall be coordinated. Considering factors, such as natural conditions, land use, infrastructure construction, and economic development level, the appropriate technical scheme for urban rainwater and flood management shall be established to deal with the urban rain and flood problems under the changing environment. In terms of the technical level, the government should strengthen the research and practice of source control technology and prevention measures, establish long-term monitoring and evaluation technology, combined with engineering measures and non-engineering measures, to ensure the effectiveness and adaptability of urban rainwater and flood management technology to improve the level of urban rainwater and flood management.