北京山区单沟洪水演进水动力模型研究

Study on hydrodynamic model of single gully flood routing in Beijing mountainous area

为模拟北京山区洪水演进,以二维浅水方程为基本理论,综合考虑地质以及土地利用情况,采用有限体积法进行离散,构建了山区小流域内的单沟水动力学模型。通过引入整体修正通道流量的方法,解决陡坡和薄水层汇流时容易出现的虚假流量问题,提升模型精度,并在此基础上模拟洪水演进。以北京山区典型单沟两场实测降雨数据进行模型验证,对应时间点水位误差小于0.027 m,流速误差小于0.014 m/s,含水率误差小于0.005 m3,模型可靠度高,且计算效率良好。对研究区域内四种重现期下的山洪进行模拟,结果显示:随降雨强度增大,达摩沟主沟及支沟3为积水最为严重的区域,需重点进行防洪排水建设。该模型可为有关部门提供防洪减灾参考依据,同时研究成果也为小流域的单沟山洪演进提供了新的思路和方法。

In order to simulate the flood routing in Beijing mountainous area,a single gully hydrodynamic model of a mountainous small watershed is established by finite volume method.Confluence calculation is completed by two-dimensional shallow water equations based on Navier-Stokes equations.In this process,the finite volume method of unstructured grid is used for discretization,and the whole modified channel flow is introduced to reduce the influence of false flow.The model is verified with the measured rainfall data of two typical single gullies in Beijing mountainous area.The water content error range is less than 0.005 m3,the water level error range is less than 0.027 m,and that of current velocity is less than 0.014 m/s.The model has high reliability and good calculation efficiency.Based on the mathematical model,flows under four recurrence periods in the study area are simulated.The results show that with the increase of rainfall intensity,the main gully and branch gully 3 of Damo gully are the areas with the most serious stagnant water,and it is necessary to focus on flood control and drainage construction.This model can provide reference for relevant departments in flood prevention and disaster reduction.At the same time,the research results also provide new ideas and methods for the evolution of single gully mountain torrent in small watershed.