Thoughts on the construction of sponge city?

The construction of sponge city is an important part of the construction of ecological civilization in China. At present, the construction of sponge city in China is still in the exploration stage. According to the idea of sponge city construction put forward in the Technical Guide of Sponge City Construction, taking Jingzhou as the research object, this paper discusses the idea of sponge city construction.

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In recent years, the rapid economic development and the acceleration of urbanization in China have brought many new problems. For example, the scale of the city is expanding, and the proportion of underlying surface hardening in the built-up area is increasing, which obviously changes the hydrological and hydraulic characteristics of the city; In addition, in the past, the urban drainage design concept based on "quick drainage" and "terminal concentration" control often resulted in "waterlogging when it rains, and drought and waterlogging turn sharply". In view of this severe problem, the China Municipal Government proposed to promote the construction of ecological civilization as an important strategic goal and to build a "sponge city" with natural accumulation, natural infiltration and natural purification.

1 the concept of "sponge city"

"Sponge city" refers to a city that has good elasticity like a sponge when dealing with various natural changes. When it rains, rainwater will be stored or utilized by means of storage, infiltration and purification to supplement groundwater resources; When the city needs water, it can release the remaining rainwater and improve the hydrological circulation system as a whole to cope with the long-term complex artificial and natural environment.

2 "Sponge City" construction approach

According to the Technical Guide for Sponge City Construction issued by the Ministry of Housing and Urban-Rural Development (hereinafter referred to as the Guide), there are three main ways to build a sponge city: ① to protect the original ecological background of the city. It is the basic requirement of sponge city construction to protect the original water ecological sensitive areas such as rivers, lakes, wetlands, pits and ditches to the maximum extent and maintain the natural hydrological characteristics before the development of the city. (2) Using ecological means to repair and restore other natural environments destroyed under the traditional urban construction mode, such as water systems and wetlands; ③ Low-impact development. Control the reasonable intensity of construction and development, reserve enough ecological construction land in the city with the development and construction concept of minimum impact on urban environment and ecology, and control the proportion of urban impervious underlying surface.

3 Jingzhou sponge city construction ideas

3. 1 Protection of ecological base-dividing the forbidden area and suitable area of sponge city.

Starting with the urban development pattern of Jingzhou, taking the urban area of 1576km2 as the research background space, in order to ensure the basic ecological security of the city, maintain the continuity, integrity and scientificity of the ecological environment system, and prevent the disorderly spread of urban built-up areas, the basic urban ecological control line has been initially formed. Water source protection areas, scenic spots, cultural relics protection areas, nature reserves, centralized basic farmland protection areas, country parks, major rivers, reservoirs and wetlands, ecological corridors and urban green spaces are all included in the basic ecological control line, forming an ecological security barrier for urban development. The suitable construction area for sponge city construction is 480km2 in the central city, that is, the central city 102.5km2 of construction land, which is included in the peripheral group, forming the area surrounded by the planned Erguang Expressway, 3 18 National Highway, the Yangtze River, Jianghan Canal, Niye South Road, Shanghai Avenue, Shagong Expressway, Shanghai-Chengdu Expressway and Changhu Lake, which is also the boundary of the central city.

3.2 Ecology

3.2. 1 Transformation of vertical channelized section There are two methods to transform vertical channelized section, namely, transforming it into slope ecological section and vertical ecological section. Transformation of vertical section into slope section: The water surface of the reconstructed river section is wide, and the surrounding area has certain purposes, mainly to break the vertical retaining wall, trim the slope section, plant waterfront plants and form natural slope protection. Transformation of vertical section into vertical ecological section: the area with narrow water surface and normal water level depth not exceeding 0.8m near the revetment is transformed, and bamboo baskets planted with soil and aquatic plants are placed near the vertical revetment, which enriches the shoreline landscape level and has a certain purification effect on water quality. 3.2.2 Slope-type channelization cross-section transformation The river section is slope-type, which requires high hydrophilicity and landscape. The transformation scheme is natural ecological slope protection, and waterfront plants are planted on the slope.

3.3 Low-impact development-The core idea of low-impact development is to control the source of rainwater path, so as to maintain the hydrological state before site development and minimize the impact of land development on the ecological environment. The main facilities of LID include green roofs, sunken green spaces, permeable pavements and other rainwater infiltration detention facilities. The main control objectives of low-impact development include total runoff control, flood peak runoff control, runoff pollution control and rainwater resource utilization. Because the goal of runoff pollution control and rainwater resource utilization can be achieved through total runoff control, the total runoff control is chosen as the primary control goal of low-impact development. According to the requirements of runoff control rate in Guiding Opinions on Promoting the Construction of Sponge City issued by the State Council General Office, it is determined that the annual runoff control rate of Jingzhou City is ≥70%.

After the target is determined, the annual runoff control rate target is decomposed. Referring to the zoning map of annual total runoff control rate in the Guide, the annual total runoff control rate of each sponge area in Jingzhou City is based on 75%, and the index value is adjusted according to the difficulty of sponge city construction or transformation. For areas with relatively more undeveloped land and moderate building density, it is difficult to build or transform sponge cities, and the index value can be appropriately improved; For areas with relatively large proportion of construction land and high building density, if it is difficult to build or transform sponge cities, the standards may be appropriately lowered. Determine the control objectives of each partition according to the above standards, as shown in Table 1. Through weighted average, the annual total runoff control rate of the central city is 7 1.7%, and the annual total runoff control rate of the construction land in the planning area is 73.8%, which meets the control requirements of 70% (see Figure 4).

4 conclusion

The construction of sponge city is an important part of the construction of ecological civilization in China. At present, the construction of "sponge city" in China is still in the initial stage of exploration and research, and its construction content has also been extended to urban water system problems such as urban waterlogging control, black and odorous water bodies and rainwater and sewage diversion. Planners should give full play to their own advantages in design and technology, integrate multiple disciplines, fully consider the protection and utilization of existing natural resources, design more urban sponges according to local conditions, and create an ecologically civilized and livable city.

The above are collected and sorted by Zhong Da Consulting Company.

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