不同植物边坡的糙率系数和水力学特征参数

目的]研究北方土石山区植物边坡糙度,为坡面生态防护的最佳植物配置选择提供依据。方法]在北京市昌平区试验基地设置多组不同地表类型的径流小区,设计了控制流速、流量的野外放水冲刷试验。结果](1)与乔灌植被相比较,草本植被对地表径流流速具有良好的阻滞作用,毛白杨对地表流速有加速作用。(2)草地的平均糙率系数最大,裸地最小。对裸地进行处理后发现,铺设枯枝物,可以有效提高地表糙率系数值,通过砾石压盖处理的地表糙率系数并未有明显改变。(3)各类地表下垫面的雷诺系数Re均介于21.34~23.49之间,枯落物小区Re最大,毛白杨小区Re最小,水流均为层流,紊动性弱;弗劳德数Fr介于0.35~2.55之间;阻力系数f介于1.03~54.43之间。结论]枯落物和草地可以有效减缓地表径流流速;毛白杨下垫面防蚀功能最弱。

Roughness Coefficient and Hydraulics Characteristics Parameters of Slopes with Different Plants

Objective] In order to determine the optimal plant configuration of slope ecological protection, we designed a washout test by control the velocity and flow of water in runoff plots of different surface type. Methods] Based on experimental data, we studied the effect of different surface types on both surface roughness coefficient and hydraulics characteristic parameters. Results] (1) The effect of herbaceous vegetation on the velocity of the block is better than shrub tree species. Populus tomentosa promote the surface velocity. (2) The largest average roughness coefficient is in the lawn plot, the smallest is bare plot. Laying litter in bare ground can effectively increase the surface roughness coefficient value and there is no significantly change by laying gravel. (3) Reynolds coefficient(R_e) is 21.34~23.49 and the largest is the litter surface, the smallest is Populus tomentosa surface. Water flow is laminar flow, the turbulence is weak, Froude coefficient(F_r) is 0.35~2.55, Darcy-Weisbach resistance coefficient(f) is 1.03~54.43. Conclusion] The bare land with litters and grassland surface can effectively resist runoff scour and the Populus tomentosa underlying surface has the potential to cause the most amount of soil erosion.