草地坡面水动力学特性及其阻延地表径流机制研究

Study on the Dynamic Characteristics of Overland Flow and Resistance to Overland Flow of Grass Slope

利用野外实地放水试验,分析草地减流减沙效益,研究草地与裸地坡面的产流产沙过程与坡面流水动力学特性。试验结果表明,草地与裸地坡面土壤入渗过程均符合Horton入渗公式,且裸地坡面土壤入渗率约为草地的45%;草地坡面含沙率平均值较裸地减少70%左右、输沙率减少80%左右、径流系数减少30%左右;裸地与草地坡面流雷诺数Re均属于层流范畴,当坡面径流量较小时,裸地和草地坡面流的雷诺数和弗劳德数属于层流中的缓流范畴,当坡面径流量进一步增大,裸地坡面径流属于过渡流急流流态;草地和裸地坡面径流深没有明显差异,草地坡面径流流速明显较裸地低,而且Darcy-weisbach阻力系数f和曼宁糙率系数n的平均值分别是裸地的3.4和2倍。

The effect of grass on runoff and sediment reductions was analyzed by using field experiment. And the generation process of runoff and sediment erosion and the hydrodynamic characteristics of flow on grass slope were quantitatively studied. The result indicated that the process figure of water infiltration in the slope without grass was coincidental with Horton formula, as well as the grass slope. And the soil infiltration rate in the slope without grass is 45 % of the grass slope;compared with the slope without grass, the average runoff sediment concentration rate, sediment yield rate and runoff coefficient of grass slope decreased 70N ,80N and 30N,respectively. When the runoff was little, the flow regime on both the slopes was tranquil and laminar flow. As the runoff increased, the flow regime on slope without grass was a rushing and transition flow. The runoff depth of both slopes was not significantly different. However, runoff velocity of grass slope will significantly reduced compared to slope without grass. The average flow resistance coefficients of grass slope, f and n, were 3.4 times and twice the coefficients of slope without grass.