基于不同重现期降水的LID措施水文调控性能研究

Hydrological Regulation Performances of LID Practices Based on Different Rainfall Reappearance Periods

作为最典型的土地利用变化过程之一,城市化进程通过改变该地区的下垫面条件,改变了天然状态下的水文机制,并进而产生一系列水环境问题。低影响开发(LID)的雨洪调控措施通过在源头上消纳径流,被视为解决城市雨洪问题的新方法。通过SWMM(Storm water management model)软件建立模型,对不同重现期降水的典型LID措施截流池、入渗带、透水性路面和生物滞留池进行了模拟。模拟结果表明,各LID措施的调控性能随着降水重现期的不同而产生明显的变化;随着降水量的增大,各措施的洪峰流量消减率及入渗补给率(截流池除外)均有不同程度的下降,但洪峰流量消减量随着降水量的增大而增大,入渗量基本保持不变(截流池除外);当采用相同的表面面积设计时,滞留池的洪峰流量消减性能最好,入渗带的入渗补给性能最好;决定其调控性能最主要的因素本质上为其"有效容积",即各措施所能容纳的水量。

Urbanization caused hydrological change and increased stormwater runoff volumes,which led to flooding,erosion and the degradation of instream ecosystem health. Low impact development（ LID）options had been proposed as an alternative approach to mimic the natural flow regime by using decentralized designs to control stormwater runoff at the source,rather than at a centralized location in the watershed. Hydrological regulation performances of these LID practices can be influenced by rainfall characteristics,such as rainfall intensity and duration. To evaluate the impacts of different rainfall reappearance periods,rainfall analysis was conducted to determine the rainfall characteristics and SCS II type was selected for the analysis. A modeling approach based on SWMM was described to incorporate these LID practices into an existing hydrological model to estimate the impacts of LID practices on the surface runoff. Results demonstrated that the LID practices led to significant stormwater control for different rainfall reappearance periods. Hydrological regulation performances of the LID practices were varied with rainfall reappearance periods. For LID practices with the same surface area,the detention pond performed the best in reducing peak flow rate, which was followed by infiltration trench,bioretention cell and porous pavement. Detention pond was capable to reduce the peak flow rate of 100-year storm to the value of 10-year storm,indicating significant performances. Differences in peak flow reduction were due to structure differences in the LID practices. For the infiltration regulation performances,infiltration trench had the highest recharge ratio for all the rainfall reappearance periods,followed by bioretention cell and porous pavement. Porous pavement,though made of 100% pervious material,infiltrated small runoff which was limited by the native soil infiltration rate when the rainfall volume exceeded the storage capacity. Deep analysis was conducted to determine the reasons that the LID practices performed differently when they had the same surface area. Results showed that the ＂effective storage＂,which was the water volume that a facility can contain,was the crucial factor. When rainfall intensity was larger than native soil infiltration rate,the excessive water was stored in the facility,and then it was released or infiltrated to the groundwater,depending on the facility structure. Consequently,the water exceeded the ＂effective storage＂was flowed over the LID practices and made contribution to the surface runoff directly. Calculation results showed that the ＂effective storage＂for the detention pond was1 861. 20 m^3,which was the largest among the four LID practices,and it explained the reason that detention pond worked the best in peak flow reduction. The ＂effective storage＂for the infiltration trench,porous pavement and bioretention cell were 744. 48 m^3,80. 37 m^3 and 565. 14 m^3,respectively.