植被类型对河岸带坡面流水动力特性的影响

Influence of Vegetation Types on the Hydrodynamic Characteristics of Overland Flow on Slopes in Riparian Zone

为了研究河岸带植被类型对坡面流水动力学特性的影响,通过野外简易径流小区放水冲刷试验,在3种流量(4,6,8 L/min)和6种不同坡面类型条件下对河岸带坡面流水动力学参数变化进行了分析。结果表明:(1)坡面植被的存在具有明显降低径流流速的作用,裸坡坡面平均流速(0.276±0.065 m/s)显著高于其他植被类型(p<0.05),坡面平均径流流速随着来水流量的增加而增加;(2)雷诺数随着放水流量和放水时间的增加而增加,所有河岸带边坡流型都属于层流;弗劳德数随着放水时间先减小后趋于稳定,各坡面流均属于急流状态(弗劳德数大于1);(3)植被覆盖能够明显减小坡面径流雷诺数和弗雷德数,裸坡的雷诺数(128.53)和弗雷德数(4.0)显著高于其他坡面类型(p<0.05)。狗牙根坡面的Darcy-weisbach阻力系数(3.71)以及曼宁糙率系数(0.062)均最大,表现出对坡面流流速最好的阻滞效果。

In order to study the influence of riparian zone vegetation types on the hydrodynamic characteristics of the overland flow, through the field water discharge scour experiments simple runoff plot, the variations of hydrodynamic parameters of overland flow were analyzed at three flow rates(4, 6, 8 L/min) and 6 different slope types. The results show that:(1) the average flow velocity increases with runoff inflow rates and the presence of vegetation on the slope has the effect of reducing the flow velocity;the average flow velocity [(0.276±0.065) m/s] of the bare slope is significantly higher than those on the slopes with other vegetation types(p<0.05);(2) the Reynolds number increases with runoff inflow rates, and shows an overall increasing trend with the increase of the runoff inflow time, the overland flow patterns of all riparian zones belong to laminar flow;the Froude number decreases firstly and then stabilizes with the increase of runoff inflow time;except for Cynodondactylon, the average Froude number is greater than 1 in all types, indicating that the overland flow belongs to the rapid flow;(3) vegetation coverage can significantly reduce the slope runoff Reynolds number and Froude number, and the Reynolds number(128.53) and Froude number(4.0) of the bare slope were significantly higher than those of the other slope types(p<0.05). The Darcy-weisbach resistance coefficient(3.71) and the Manning roughness coefficient(0.062) of the Cynodondactylon were the largest, showing the best hindrance to the overland flow on the slope.