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Simulation analysis of runoff reduction and control effect in sponge building district -- taking a primary school in Beijing as an example

Publish date:2019/04/11 Click count:88 次

At present, sponge city construction in China is developing rapidly, and its construction has become a hot issue. The effect of sponge city construction, especially the effect of runoff reduction and control, is the primary standard to measure the construction work, and also the most noteworthy problem. Based on this, a numerical drainage model of a primary school sponge renovation project in Beijing is built by SWMM software. According to the sponge renovation scheme, sponge facilities are set up, and design rainfall and measured rainfall are selected respectively to simulate, so as to analyze the drainage capacity and runoff reduction and control effect of the network after the campus renovation.

1、 Sponge transformation of the project

The primary school is located to the east of the North Canal, the west of the East Narcissus Road, and the east of the JINGMAO home. It covers an area of about 2.2 hectares and a building area of about 19000 square meters. In this project, the sponge transformation is guided by the problem, part of the hardened pavement is set as permeable pavement, and the infiltration function of the underlying surface is increased; by organizing rainwater runoff, the roof and road rainwater is introduced into the biological detention facilities for storage and absorption; the excessive rainwater is introduced into the end water storage module for reuse.

2、 Project model building

1. At present, sponge city construction in China is developing rapidly, and its construction has become a hot issue. The effect of sponge city construction, especially the effect of runoff reduction and control, is the primary standard to measure the construction work, and also the most noteworthy problem. Based on this, a numerical drainage model of a primary school sponge renovation project in Beijing is built by SWMM software. According to the sponge renovation scheme, sponge facilities are set up, and design rainfall and measured rainfall are selected respectively to simulate, so as to analyze the drainage capacity and runoff reduction and control effect of the network after the campus renovation.

1、 Sponge transformation of the project

The primary school is located to the east of the North Canal, the west of the East Narcissus Road, and the east of the JINGMAO home. It covers an area of about 2.2 hectares and a building area of about 19000 square meters. In this project, the sponge transformation is guided by the problem, part of the hardened pavement is set as permeable pavement, and the infiltration function of the underlying surface is increased; by organizing rainwater runoff, the roof and road rainwater is introduced into the biological detention facilities for storage and absorption; the excessive rainwater is introduced into the end water storage module for reuse.

2、 Project model building

1. Model building

According to the characteristics of simulation target and model software, SWMM software is selected to build regional model. According to the basic data of the project area, the simulation area is generalized into 132 sub catchment areas, 82 drainage pipe network sections, 80 pipe network nodes and 3 end outlets, and calibrated and verified according to the monitoring data to ensure the accuracy of the model. The model building interface is shown in Figure 2-1.






  


Figure 2-1 project SWMM model interface

  
2. Model rainfall conditions

In this simulation, the design rainfall of 1 year return period, 2 year return period, 3 year return period and measured field rainfall in Beijing are taken as the model input conditions to simulate the runoff reduction and control effect of sponge transformation in the project area. The design rainfall and the measured rainfall are shown in table 2-1 and table 2-2.



3、 Analysis of simulation results

1. Analysis of drainage capacity of rainwater pipe network before and after sponge transformation

(1) Analysis of drainage capacity of current pipe network

The design rainfall (2H) with different return periods in Beijing is used to simulate the drainage capacity of the current pipeline network in the project area. The results show that the current pipeline network in the project area does not meet the drainage requirements of one-year return period. Under the condition of 1-year design rainfall, some pipe sections are full flow, and the pipe sections (red pipe section) that do not meet the requirements are shown in Figure 3-1.



  
Fig. 3-1 filling degree of current pipe network with 1-year return period in the project area
  
(2) Analysis of drainage capacity of pipeline network after sponge transformation

The design rainfall of different return periods (2H) in Beijing is used to simulate the drainage capacity of the pipeline network after sponge transformation in the project area. The results show that the pipeline network in the project area basically meets the drainage requirements of 2-year return period, but does not meet the drainage requirements of 3-year return period. Under the design rainfall condition of 2-year return period, full flow occurs in individual pipe sections. Under the design rainfall condition of 3-year return period, full flow occurs in some pipe sections. The pipe sections (red pipe sections) that do not meet the requirements are shown in Figure 3-2.



Fig. 3-2 pipe network fullness after 2-year and 3-year sponge reconstruction in the project area
  
2. Analysis of runoff reduction and control effect after sponge transformation

In order to evaluate the effect of runoff reduction and control after sponge transformation of the project, three measured rainfall fields are used for model simulation, and the simulation results are shown in table 3-1.

  



  由以上结果可得,该项目经过海绵改造,径流总量和峰值流量均有一定程度的削减。实测降雨1、实测降雨2和实测降雨3这三场降雨的降雨量分别为20.0mm、34.0mm和48.5mm,说明场次降雨量在30mm左右时,径流总量削减率可达到34.5%左右,峰值流量削减率可达到34.1%左右。From the above results, it can be concluded that the total runoff and peak flow of the project have been reduced to some extent after sponge transformation. The rainfall of measured rainfall 1, measured rainfall 2 and measured rainfall 3 are 20.0mm, 34.0mm and 48.5mm respectively, which shows that when the rainfall is about 30mm, the total runoff reduction rate can reach about 34.5%, and the peak flow reduction rate can reach about 34.1%.

4、 Simulation conclusion

The SWMM model can be used to evaluate the runoff reduction and control effect of the sponge transformation. By building a model to analyze the runoff reduction and control effect of a primary school sponge renovation project in Beijing, it can be concluded that after sponge renovation, from the perspective of drainage capacity improvement of the pipe network, the drainage capacity of the rainwater pipe network in the project area does not meet the standard of once-in-a-year to once-in-two-year, but it is still less than the drainage requirements of once-in-three-year, and the way of increasing the storage capacity of sponge facilities or pipe network renovation can be adopted Ensure that the pipe network meets the standard. From the point of view of runoff reduction, the total runoff and peak flow are reduced to a certain extent, and the effect of runoff control is more significant.