细沟侵蚀是坡面侵蚀的主要方式,在坡面侵蚀产沙及其输移过程中占有重要的地位和作用。通过放水冲刷试验,测定并研究了坡面细沟中径流的水力要素特征及其相互关系。试验中坡度采用6°,10°,12°和15°共4级,径流流量变化控制在40～500ml/s之间。结果表明,黄土陡坡上细沟径流的流速、过水断面宽度,以及径流深都能表示成径流量和坡度的函数。在确定坡面细沟流各水力要素间关系指数的基础上,探讨了用径流量和坡度因子估算细沟径流水力参数的方法。经用实测资料验证,在实验土壤及流量、坡度条件下,用文中提出的方法估算的细沟径流深具有一定的精度。

Soil erosion has been a worldwide environmental problem.Soil erosion results in not only degeneration of soil productivity, but also floods and pollution of water resources.Soil erosion and its controls have been studied extensively.A major field of these is the soil loss prediction which enables the planner to predict the average rate of soil erosion.With the development of computer technology, soil erosion prediction has shifted from empirical models to theoretical models.But it is difficult to measure the hydraulics needed in construction of process-based model.In this study, inflow experiments were conducted on the loess slope to determine hydrodynamic characteristics of flow in rills, and friction coefficients on the steep slope conditions.All experiments were conducted in a 5-m-long, 0.5-m-wide, and 0.7-m-deep flume.Slope steepness can be manually adjusted to 6?, 10?, 12?, 15? and 20?.To let water infiltrate tested soil freely, natural sands was packed into the flume about 0.3 m in depth before soil was filled in, and than tested soil was filled and adjusted to reach a bulk density of 1.17 g/cm 3.Inflow water was added from the top end of the flume and inflow volumes, controlled with a watergauge, were designed as 40, 60, 100, 200, 300 and 500 ml/s respectively.Throughout each run the following data were collected:mean velocity, depth of runoff, section shape of rill, and sediment samples.Each run consisted in 30-min duration and two replications of each of five slopes were assigned.Experiments results show that hydraulic geometry of rill on the loess slope, which are the mean width of cross sections, mean velocity, mean depth of flow, could be related to discharges and slope gradient in power relations.Manning roughness coefficient ranges from 0.035-0.071 with an average of 0.0536.Based on the relationship of hydraulic characteristics to discharges and slope gradients, a method to determine hydraulic coefficients of flow in rills are proposed.Data from experiments show that the predicted flow depth of rills using the method in the paper is close to the observed one.