Analysis of Several Problems in the Construction of Sponge City

Sponge city refers to a new urban construction concept used to solve urban flood disasters and water ecological problems. It is important for the construction of ecological civilization. It plays an important role in the green development and livability of the city. In the construction of a sponge city, it is necessary to make special urban planning and improve the top-level design. In recent years, China has developed a number of sponge city pilot projects. The numerous experiments act as important references for the urban construction in China. This paper mainly analyzes the requirements for the construction of sponge city and discusses several problems as well as solutions in the construction.

Flood Control and Aquifer Recharge Effects of Sponge City: A Case Study in North China

Sponge City is an integrated urban stormwater management approach and practice to tackle waterlogging, flooding, water scarcity, and their related problems. Despite many positive effects of Sponge City on flood control that have been investigated and revealed, the effect on aquifer recharge is still less known. Considering maximizing the function of natural elements such as surface water bodies and subsurface storage space, to minimize the use of a gray drainage system, a Sponge City design was proposed to substitute the planning development scheme in the study area. The stormwater management model of SWMM (storm water management model) and the groundwater flow model of MODFlow (Modular Three-dimensional Finite-difference Groundwater Flow Model) were adopted to evaluate the flood-control effect and aquifer-recharge effect, respectively. Compared with the traditional planning scenario, the peak runoff is approximately 92% less than that under the traditional planning scenario under the condition of a 5-year return period. Due to the increase in impervious areas of urban construction, the total aquifer recharge from precipitation and surface water bodies was decreased both in the present planning scenario and the Sponge City design scenario. However, the Sponge City design has a positive impact on maintaining groundwater level stabilization and even raises the groundwater level in some specific areas where stormwater seepage infrastructure is located.

Sponge City Policy and Sustainable City Development: The Case of Shenzhen

The massive construction of buildings has changed the city’s aquatic ecological environment. The aquatic ecological condition of the city has been deteriorated with serious water issues. To coordinate various departments to jointly build the sponge city and improve the water environment, the Shenzhen government formulated the policy note on “Interim Measures for the Construction Management of Shenzhen Sponge City”. This article discusses the impact of the policy note on Shenzhen’s construction of sponge cities. The result shows that the policy is effective from the perspective of the environment. However, in the face of a complex water ecological environment, there are still some deficiencies in the policy. We therefore put forward policy suggestions for the Shenzhen municipal government to better manage its construction of sponge city in the future.

A New Strategy for Sponge City Construction of Urban Roads: Combining the Traditional Functions with Landscape and Drainage

Urban roads play a key role in sponge city construction, especially because of their drainage functions. However, efficient methods to enhance their drainage performance are still lacking. Here, we propose a new strategy to combine roads, green spaces, and the drainage system. Generally, by considering the organization of the runoff and the construction of the drainage system (including sponge city facilities) as the core of the strategy, the drainage and traffic functions were combined. This new strategy was implemented in a pilot study of road reconstruction conducted in Zhangjiagang, Suzhou, China. Steel slag was used in the structural layers to enhance the water permeability of the pavement and the removal of runoff pollutants. The combined effects of this system and of the ribbon biological retention zone, allowed achieving an average removal rate of suspended solids, a chemical oxygen demand, a removal of total nitrogen and total phosphorus of 71.60%, 78.35%, 63.93%, and 49.47%; in contrast, a traditional road could not perform as well. Furthermore, the volume control rate of the annual runoff met the construction requirements (70%). The results of the present study indicate that, combining the traditional basic functions of roads with those of landscape and drainage might be a promising strategy for sponge city construction of urban road.

Sponge-city-based urban water system planning: a case study of water quality sensitive new area development in China

In recent years, sponge city has been booming in China aiming to alleviate urban flooding and improve water quality of natural water bodies. LID/green infrastructure has been gradually introduced to urban planning and urban water system planning. Efficient deployment of LID facilities is critical, which requires modeling and evaluation to develop rational planning. A case study of Guian New Area was presented to show the application of SWMM and the planning methods in sponge-city-based urban water system planning for water quality sensitive new areas development. Based on SWMM, two river network water quality models, the Dongmenqiao River and the Chetian River, were established through a systematic analysis of the case study area. Baseline scenarios were simulated and analyzed, and assimilation capacities of the two river basins were calculated by a trial-and-error method. Finally, two LID scenarios were carefully designed, simulated, and analyzed to support the planning. The simulations showed that in order to meet the strict water quality requirements in Guian New Area, large scales of LID facilities are required to cut down the rainfall-runoff pollution. Moreover, measures such as more frequent cleaning to reduce pollutants accumulation on the ground should also be taken to mitigate the maximum buildups of pollutants.