细沟侵蚀特征及其产流产沙过程试验研究

Experimental study on rill erosion characteristics and its runoff and sediment yield process

在不同坡度(15°、20°、25°)和降雨强度(1.5mm/min和2.0mm/min)条件下,利用室内模拟降雨试验,研究了杨凌塿土和安塞黄绵土的坡面细沟发育过程、形态特征及水沙关系。结果表明,不同降雨强度和坡度下,塿土坡面的细沟发育规律基本一致,主要由沿坡面方向呈线状分布的跌坎链相互连通而成,表现为沟头溯源侵蚀和沟道下切侵蚀,细沟宽深比随雨强及坡度增加而变小,细沟密度则随之而增加;黄绵土的跌坎形状为长条状,细沟主要由单个跌坎发育而成,发育过程中溯源侵蚀和边壁崩塌现象更为明显,细沟的宽深比较大。相比黄绵土,塿土的产流和达到稳定径流量的速度较快,相同降雨强度条件下,不同坡度间径流量的差异性较小;不同降雨强度和坡度条件下,塿土的含沙量变化过程较为一致,最终会趋于一个稳定值,黄绵土含沙量的变化过程较为复杂。另外,两种土壤从含沙量开始较快增加至达到最高值的时间段与其细沟形成及发育的时间段大体吻合,相比之下塿土更易发生细沟侵蚀。

In an indoor simulating rainfall experiment with different slopes （15°, 20°, 25°） and rainfall in tensities （1.Smm/min and 2.0mm/min）, the rill development process, and its morphological characteristics and runoff and sediment yield were studied with cumulic cinnamon soil and loessial soil, The resuhs show that the rill development law is agreement for cumulic cinnamon soil under different slopes and rainfall in tensities, i.e. rills evolve from a series of stepdown floor which are parallel to each other and distributed with line at slope surface direction; the main characteristics of which is headward erosion and vertical ero sion, and rill widthdepth ratio decreases with increase in rain intensity and slope and so does the rill den sity. For the loessial soil, the shape of stepdown floor is long strip, the rills form mainly by a single stepdown floor, and headward erosion and side wall collapse is more apparent in the process of rill devel opment, so widthdepth ratio is larger. Compared with loessial soil, the speed of runoff yield and achiev ing stable runoff for cumulic cinnamon soil is faster, and the differences of runoff with different slopes are smaller, under the same rainfall intensity. At the same time, the change process of sediment concentration for cumulic cinnamon soil is more uniform in the condition with different rainfall intensity and slope, which could eventually tend to a stable value, instead, the effect of rainfall intensity and slope on the change process of loessial soil sediment concentration is more complicated. In addition, the periods for both soils from sediment concentration increasing rapidly to the maximum ones are consistent with the periods of their rill formation and development, and rill erosion for cumulic cinnamon soil is more likely to happen by comparison.