华南红壤坡面侵蚀水动力学机制试验研究

华南红壤区是我国发生潜在水土流失危害的重点区域之一,红壤坡地的水土流失现象较为严重。华南红壤地区气候温暖,雨量丰沛,降雨特点通常表现为强度大、历时长,暴雨或大暴雨事件频发,因此暴雨驱动因子影响作用更为显著,研究探讨华南红壤坡面侵蚀过程及动力特征有着重要的现实意义。通过室内35场不同雨强（30、60、90、120、180、210、270 mm·h-1）、不同坡度（5°、10°、15°、20°、25°）的人工模拟降雨试验,研究了华南红壤侵蚀的水动力学机制。主要取得以下研究结果：（1）红壤坡面侵蚀水流的流态大部分均处于＂层流—缓流区＂,除平均流速随着模拟雨强的增加而增加外,其他水动力参数（坡面侵蚀水流的阻力、曼宁糙率、径流剪切力、以及水流功）均会受到雨强和坡度改变的影响,但是不呈现特定的函数关系,规律不明显;（2）从水动力学角度解析了红壤坡面水蚀过程,得出了相对水深和曼宁糙率系数两种水动力因子共同组成的复合水动力特征参数,可作为表征不同雨强及坡度下的坡面水蚀侵蚀产沙的特征水动力参数指标。

Experimental study on soil erosion and flow hydraulics on red soil slope

In China, there is another potential heavy erosion area of china is red soil slope land in south China except loess slope.There is soil erosion potential danger due to heavy storm rainfall affairs often occur in red soil slope land in south China. It is very important to study mechanism of flow hydraulics on red soil slope in such area. This study used simulated rainfall method to investigate the interactive influence by soil slope gradien（t5°, 10°, 15°, 20°, 25°）and rainfall intensity（30, 60, 90, 120, 180, 210, 270mm h-1） on red soil erosion processes and flow hydraulics. The results show that：（1） the most treatments were shown erosion flow regimes usually indicated in sub-critical laminar flow and a little indicated in super-critical laminar（Except for two treatments： 5°slope gradient and 120mm/h rainfall intensity; 20° slope gradient and 270mm/h rainfall intensity）. Except for average flow velocity increased as simulated rainfall intensity increased, the other flow hydraulics, such as Manning roughness coefficient, Manning roughness coefficient, Shear stress, and Steam power can impacted by rainfall intensity and slope gradient, but cannot fitted by a simple function.（2） The rate of Manning roughness coefficient（n/h） is a better hydraulic parameter indicator for predicting the sediment load in red soil slope erosion.