坡面流速及侵蚀产沙空间变异性试验

Field experiment investigation into the spatial variability of overland flow velocity and soil erosion

在野外放水试验条件下,利用染色法和侵蚀针法分别观测坡面流速和侵蚀产沙空间变异性。结果表明,坡面各横向断面的流速与距坡顶距离之间呈正相关,且相关性随流量增大逐渐变得显著,纵向断面流速的变异程度明显强于横向断面。总体上,上、下坡位侵蚀程度较重,而中坡位最轻;小流量时沉积作用明显,大流量时距坡顶0-2 m范围为净侵蚀区;各坡段侵蚀量与其距坡顶距离之间呈负相关;发生泥沙沉积部位随流量增大逐渐下移,细沟侵蚀量占坡面总侵蚀量的比例随流量增大不断增加。试验条件下流速为0.30 m/s时,细沟侵蚀产沙大于细沟间侵蚀,且坡面侵蚀量迅速增大。随流量增大,流速和侵蚀产沙量呈增大趋势;但在流量较大时,坡面各坡位侵蚀量与流速呈负相关,这可能与坡面中下部位粗颗粒泥沙沉积以及含沙水流的挟沙能力基本达到饱和有关。

The spatial variability of overland flow velocity and soil erosion,and their relationship under different discharges,were investigated using a field runoff plot combined with the erosion pins. There exists a positive correlation between flow velocity and the distance from the top of slope,with the correlation becoming more significant as discharge increased. Variability of velocity at each cross section was stronger than that of the lateral section. The eroded sediment yield at the top or bottom of slope was greater than those at the middle. Sediment deposition clearly occurred for small flow discharge,and for high flows net erosion dominated the section of 0—2 m from the top of the slope. As flow discharge increased,the deposition zone gradually shifted down,and the proportion of rill erosion to the total amount of erosion increased. When overland flow velocity was greater than 0. 30 m / s,the amount of rill erosion exceeded that of inter-rill erosion,and the erosion amount of the whole slope increased rapidly. As flow discharge increased,the overland flow velocity and erosion amount also increased. However,under the same slope,greater overland flow velocity corresponding to the down-slope tended to generate smaller erosion sediment yield,which may be attributed to the deposition of coarse sediment and the almost saturated sediment carrying capacity at the down-slope.