Waterlogging in many cities in South China and Jiangnan

  Sponge cities: China's solution to urban water management

  Our reporter Guan Xiaopu

  At 15:00 on July 2, typhoon "Siamba" landed in Maoming, Guangdong with violent storms. This is the first typhoon to land in my country this year.

South China will face continuous strong wind and rain, and the north will also face a new round of precipitation.

The meteorological department reminded that the typhoon season is now active, and some areas overlap with areas with significantly more precipitation during the "Dragon Boat Water" period in South China this year, and the risk of disasters is high.

Since May, South China, Jiangnan and other places have been hit by heavy rainfall. The regional average rainfall in Fujian, Guangdong, Guangxi and other three provinces and regions is the third in the same period in history since 1961.

Studies have shown that systematically promoting the construction of sponge cities is conducive to enhancing the function of urban water storage and flood control.

  In April this year, the "Notice on Further Clarifying the Requirements for the Construction of Sponge City" issued by the General Office of the Ministry of Housing and Urban-Rural Development proposed that the construction of sponge cities should focus on the problems caused by rainwater within the built-up area of ​​the city, and focus on alleviating urban waterlogging. Rainwater runoff pollution, improve the level of rainwater collection and utilization.

my country's "14th Five-Year Plan" and the outline of the long-term goals for 2035 propose to build an urban flood control and drainage system that combines emission reduction at the source, combined storage and drainage, drainage and risk elimination, and emergency response to excess standards, and promotes urban waterlogging control to achieve significant results.

  Focusing on the problem of the masses "in front of the house and behind the house", dynamically eliminate the water points

  When it comes to urban water environment, residents are concerned about many issues: Can the urban water environment be further improved so that rivers, lakes and wetlands no longer have pungent odors?

How to solve the problem of waterlogging and waterlogging in old communities?

  "My requirement is very simple. In case of heavy rain, there should be no stagnant water on the road. If I need to go further, it is that the greenery around me can be evergreen and beautiful all year round." Heqi, Binhu District, Wuxi City, Jiangsu Province Street resident Zhang Guosheng said.

  Wuxi, the city known as the "Pearl of Taihu Lake", has a suitable climate, abundant rainfall, and is dotted with rivers and lakes. The number of wetlands ranks first in Jiangsu Province, with water and green space accounting for more than 60%.

In 2021, Wuxi City will become the first batch of demonstration cities in the country to create a systematic global promotion of sponge.

In March this year, the Ministry of Finance released the performance evaluation results of the central government's sponge city construction demonstration subsidy fund in 2021, and Wuxi ranked among the five A-level cities.

  Focusing on urban stormwater management, Wuxi City has explored and formed an urban waterlogging management model of "watershed-level flood planning, city-level storage and drainage balance, operation and management combined drainage and joint adjustment, and one-point-one-policy for waterlogging point management", and established a "waterlogging-prone point within the year". Dynamic elimination" mechanism, the city's overall waterlogging prevention standard basically reaches once in 50 years, the utilization of rainwater resources reaches 4.637 million tons per year, and the proportion of permeable ground area is 42.3%.

As of 2021, the up-to-standard area of ​​sponge cities will account for 26.2% of the built-up area, exceeding the state's established 20% progress requirement.

The sponge function is becoming an effective means to improve the community environment and the level of refined governance, enhance living comfort and improve the ability to resist waterlogging.

  Taking Binhu District as an example, sponge city has become an important concept throughout the whole process of urban and rural planning and construction.

In the Taihu Lake National Tourism Resort Sewage Treatment Center, the "sewage treatment plant" is integrated with the "ecological wetland park", effectively improving the regional water environment, increasing biodiversity, and becoming one of the important sources of ecological replenishment of the regional river water network; Hua The construction of the livable area reconstruction project in Jingxin Village takes into account the site conditions, and adopts sponge city measures such as sunken green space, permeable pavement, glass pumice, and mobile flower boxes. Sponge city measures such as permeable pavement, bioretention facilities, sunken green space, and grass-planting ditch have been adopted.

Up to now, the construction area of ​​sponge city in Binhu District accounts for 25.3% of the total area of ​​the existing built-up area of ​​the city.

  "Sponge city is a new concept of urban construction and development that reshapes the relationship between city, people and water under the background of ecological civilization construction and based on the urban hydrological cycle." Secretary and director of the Party Committee of Wuxi Housing and Urban-rural Development Bureau, director of the Office of the Municipal Sponge City Construction Leading Group Chen Xuefeng said that he will adhere to the people-centered, focus on urban rainwater management, focus on urban rainwater management, further improve urban flood control and drainage capacity, dynamically eliminate water accumulation points, and implement the concept of sponge city to transform old communities and urban areas. In-depth management of water environment, comprehensive elimination of inferior water bodies, continuous improvement of urban ecological quality, enhancement of urban ecological quality, and creation of a poetic living environment.

  It is not only necessary to improve the "face" of the city, but also to consolidate the "interior" of the city

  The sidewalk paved with permeable bricks has a "notched curb" every tens of centimeters, sunken green spaces, ecological parking lots, rain gardens... Today's sponge city, with these "secret weapons", no need for light rain Worrying about wet shoes, the phenomenon of road water accumulation has also been greatly improved.

The absorption and storage of rainwater by the "sponge" can not only alleviate the peak runoff, reduce the pressure of flood control and drainage of the pipe network, prevent waterlogging, and the rainwater can be recycled and reused.

  "We should not only improve the city's 'face', but also consolidate the city's 'interior'." Chen Xuefeng introduced that in combination with the "big plate" of urban development, Wuxi constantly explores the "embedded" urban construction and development model of the sponge city concept.

In the reconstruction and expansion projects, the "project + sponge" model is adopted, adheres to the problem orientation, effectively improves the living environment, and collaboratively solves the problems that the people care about and concern about, such as waterlogging, runoff pollution, and imperfect drainage facilities.

In new residential communities, municipal roads, square green spaces, urban water systems, new parks, and development zones, etc., high standards and all-round implementation of sponge city construction requirements will form a group of sponged high-quality ecological products to provide the masses with inclusive benefits. people's well-being.

  In April this year, a series of documents of the "Action Plan for the Systematized Global Promotion of Sponge Demonstration City Construction in Wuxi City" were released, and the construction drawings were scheduled for the global promotion of the construction of sponge demonstration cities.

The Action Plan clarifies the construction tasks of 6 categories of projects, including residential quarters, roads and squares, parks and green spaces, water system management, drainage pipeline networks and stations, and capacity building, and a total of 366 engineering projects are arranged.

  Such as renovation of old residential areas and urban renewal projects, roof maintenance should use materials that do not pollute rainwater or have less pollution. If conditions permit, roof rainwater drainage facilities can be set up, rainwater collection facilities can be added, and drainage pipe network renovations should be improved and dredged. Sewage and rainwater pipe network, implement rainwater and sewage diversion to ensure smooth drainage.

Park green space projects require permeable pavement for pedestrian systems and parking lots. Constructed wetlands, rain gardens, sunken green spaces, grass-planting ditch, etc. are built in the green space according to local conditions.

For another example, within the range of the greening control line of the waterfront green belt, facilities such as wet ponds and rainwater wetlands should be constructed to regulate, store and purify the runoff rainwater. When the green belt receives the runoff rainwater from the impervious catchment surface such as adjacent urban roads, a vegetation buffer zone should be set up. , to reduce runoff velocity and pollution load.

  When the sponge is connected, the ecological benefits can be magnified.

Just this year, all districts in Wuxi will form at least one sponge city demonstration area with contiguous effect.

From underground pipe network renovation to roof greening, from river and lake water ecological restoration to building block rain gardens, 9 areas including Canal Bay, Railway Station South Plaza, and the former Xixing Steel Plant have fully implanted the concept of sponge city in the renovation and upgrading plan. It will combine the construction of houses, roads, squares and greening facilities to create a comprehensive sponge area, and gradually form a continuous sponge area in the area.

  Many cities are facing the problem of "more water, less water and dirty water" at the same time, and building a sponge city is to solve it systematically

  Wang Jiazhuo, president of the Ecological Municipal Institute of the China Academy of Urban Planning and Design, believes that many cities in my country are facing the problems of "more, less and dirty water" at the same time.

To build a sponge city is to solve these problems systematically.

  The so-called "sponge city" means that the city can be like a sponge, with good "elasticity" in adapting to environmental changes and responding to natural disasters. Water is "released" and utilized. By strengthening the management of urban planning and construction, we can give full play to the absorption, storage and slow release of rainwater by ecosystems such as green spaces and water systems, effectively control rainwater runoff, and achieve natural accumulation, natural infiltration, and natural purification. Urban development concept.

  Huang Guoru, a professor at the School of Civil Engineering and Transportation at South China University of Technology, believes that its essence is modern urban stormwater management, which is in line with the green (rainwater) infrastructure proposed in recent years.

  "The concept of low-impact development, which is widely used today, refers to the hydrological process of reducing the impact on the environment as much as possible in the process of urban development and restoring it to its original natural state through some measures." Huang Guoru told reporters, "traditional drainage The model is that the more rainwater is discharged, the faster the better, and the low-impact development of the rainwater system is based on the policy of 'infiltration, retention, storage, purification, utilization, and drainage', and the infiltration, retention, collection, storage, purification, and recycling of rainwater are used. It is closely integrated with drainage, and comprehensively considers multiple goals such as waterlogging prevention, runoff pollution control, rainwater resource utilization and water ecological restoration, so as to achieve a more livable, safer, more energy-saving and more ecological."

  Generally speaking, sponge city measures can be divided into three categories.

The first is "small sponges", that is, sponge city measures in a narrow sense, emphasizing source control, and controlling the amount and quality of water during rainfall through measures such as bioretention ponds, grass ditches, green roofs, storage facilities and permeable pavements, and reduce drainage. The pressure of conduit facilities is mainly for frequent light rain events.

The second is "medium sponge", which corresponds to drainage pipeline facilities and waterlogging drainage and risk-removing facilities. Through pipe network pumping stations, underground deep tunnel projects and large-scale storage projects, rainwater is discharged or stored, which can alleviate the risk of moderate and heavy rain events. Urban flooding.

The third is the "big sponge", that is, the countryside, farmland, rivers and lakes and wetlands around the city are included in the scope of sponge city construction, so that the city's waterlogged water can be drained.

  Huang Guoru pointed out that from the perspective of infrastructure construction, the "green, gray and blue" problems should be properly handled in the construction of sponge cities.

Green infrastructure corresponds to "small sponges", which can reduce stormwater runoff, delay the peak time of stormwater runoff, effectively remove runoff pollutants, replenish groundwater, and improve the urban "heat island" effect, thereby improving water quality and mitigating floods.

The gray infrastructure corresponds to the "medium sponge", emphasizing that the runoff treated by the green infrastructure should be discharged to the blue infrastructure as soon as possible, so as to play a linking role.

The blue infrastructure gives full play to the huge regulation and storage function of the largest sponge body in the river network water system, giving priority to the use of natural forces to store and drain water, so as to control the water volume.

  The prevention and control of urban waterlogging is a systematic project, which should emphasize the combination of source and end, underground and above-ground, and green, gray and blue.

  People are no strangers to urban waterlogging.

Regarding the main goal of sponge city construction, the "Notice on Further Clarifying the Relevant Requirements for Sponge City Construction" issued by the General Office of the Ministry of Housing and Urban-Rural Development clarifies that sponge city construction is one of the important measures to alleviate urban waterlogging and can effectively deal with the recurrence period of waterlogging prevention and control design. The heavy rainfall within the range makes the city have good "elasticity" and "resilience" in adapting to climate change and resisting rainstorm disasters.

  Let’s first look at the causes of urban waterlogging. Heavy rain is the most important and direct factor.

Studies have shown that due to the continuous increase of urbanization rate in my country, the local rainfall conditions have been changed, and some cities have "heat island" and "rain island" effects, and water vapor is more likely to condense, increasing the possibility of heavy rain.

  In addition, the change of the underlying surface of the city is also a major reason.

With the expansion of cities, the original rural suburbs have become urban areas, that is, the impervious area increases, the permeable area decreases, and the storage, stagnation, and seepage capacity decreases, aggravating the formation of rainstorms and floods.

In addition, there are also reasons for the lack of long-term planning for the development and construction of urban underground drainage pipelines, low drainage standards, and insufficient drainage capacity with the large-scale urban expansion and construction.

  Where is the difficulty in preventing and controlling urban waterlogging?

Huang Guoru believes that, on the one hand, under the background of frequent extreme rainstorms caused by global climate change, the superposition of my country's urbanization process has magnified the possibility of disasters; Due to the scarcity of land and the high cost of demolition, it is difficult to build a rainwater system for high-density and low-impact development in a short period of time, and it is also difficult to upgrade the drainage network.

"my country has always had the institutional advantage of concentrating its efforts on major events. After more than ten years of construction and development, according to the country's timetable, there will be great improvements in 2035." Huang Guoru said.

  Although sponge city has been promoted in China for eight years, as an urban development concept, it is still a new thing, and some misunderstandings in understanding are constantly corrected in practice.

For example, in the past, most of the emphasis was placed on end-to-end treatment, and all problems were solved in rivers, sewage plants, and rivers and lakes wetlands, which was half the effort. Now all localities realize that only by controlling the source, making low-impact development facilities between community units, and then rebuilding Good pipelines, river courses, river and lake wetlands, and comprehensive measures can achieve twice the result with half the effort.

  The prevention and control of urban waterlogging is a systematic project.

In the process of sponge city construction, attention should be paid to the combination of source and end, the combination of underground and above ground, and the close combination of green, gray and blue, rather than simply equating sponge city construction with low-impact development in a narrow sense.

In terms of professional integration, it is necessary to highly integrate various industries such as municipal administration, water affairs, water conservancy, urban planning, landscape architecture, urban management, etc. In the face of the opportunities and challenges brought by the construction of sponge cities, all majors should be closely integrated and coordinated, and must not be Working alone, only in this way can the construction of sponge cities develop sustainably and truly solve the complex water problems faced by our country.