ObjectiveThe suburban hilly area is the ecological barrier of city. Due to the steep slope of terrain in the suburban hilly area and the short peak time of flood peak, it is easy to form seasonal floods, resulting in flood disasters. The purpose of this paper is to explore reasonable stormwater management methods in suburban hilly area and to study the applicability of different stormwater management scenarios in mountainous area.
MethodTaking the upper reaches of the Jiakuohe River in the shallow mountainous area of Beijing as an example, the hydrological model of HEC-HMS and HEC-RAS was used to simulate the stormwater runoff process under the once in 10 years stormwater. The three different stormwater management scenarios(traditional management scenario, low impact development scenario, and natural scenario) were compared and analyzed in stormwater control effects, ecological environmental impacts, and landscape effects, thereby exploring the effectiveness of stormwater management measures in different suburban hilly areas.
Result(1) In terms of stormwater control effects, the storage capacity under traditional management scenario and low impact development scenario were 3.8 times and 5.0 times of natural scenario, and the maximum flooding range was 2.0% and 1.2% higher than natural scenario. The reduction rate of peak traffic flow in traditional management scenario and low impact development scenario was 18.3% and 31.5%, respectively, and the peak current time was delayed by 35 and45 min, respectively. (2) In terms of ecological environment impact, the positive effects of low impact development model on river vegetation environment and hydrological connectivity were greater than traditional management model and natural model. (3) In terms of landscape effects, low impact development scenario had great advantages in terms of water body scope and environmental fit.
Conclusion(1) Compared with the traditional stormwater management model, the low impact development model has a good stormwater storage and storage function, which can increase the stormwater storage capacity, reduce the peak flow rate, delay the peak time, and further reduce the development mode. It can improve the river ecological environment and has a good landscape effect. Therefore, through comprehensive judgement, low impact development scenario is more suitable for the research basin of this paper. (2) The low impact development model can take advantage of the topography of suburban hilly area and collect upstream water collection by designing a stormwater reservoir in a gentle terrain. At the same time, the low impact development model formulates the stormwater flood target according to the design specifications of the sponge city, and realizes that the annual total runoff control rate of the upper reaches of the river channel is greater than 85%, taking into account the river ecological and landscape needs.(3)The HEC-RAS hydrological model can quantify and visualize different stormwater management scenarios and provide technical support for stormwater management in suburban hilly area. (4) The study emphasizes the particularity of each region. The stormwater management measures in suburban hilly area extend the application of low impact development scenario from another level, indicating that traditional water conservancy facilities are also applicable to the stormwater management concept of low impact development.