黄土坡耕地径流水力学参数与侵蚀产沙的模拟

Simulation of Runoff Hydraulics Parameters and Sediment Yield at Loess Tilled Slope

为了明确连续降雨条件下黄土坡耕地微地形的径流产沙及水力学特征,基于4种坡度(5°,10°,15°,25°)、4种耕作方式(直线坡、人工锄耕、人工掏挖、等高耕作)和2种雨强(60mm/h,120mm/h)的组合,通过室内模拟连续90min降雨试验,对不同坡面的径流泥沙特征和水力学参数进行了定量分析和计算。结果表明:4种耕作措施的径流量和产沙量均遵循一致的规律,从大到小均为直线坡>人工锄耕>人工掏挖>等高耕作,直线坡的径流量和产沙量分别是等高耕作坡面的2倍和2.3倍,其水土保持效应依次增强;相同耕作方式下,与60mm/h雨强相比,120mm/h雨强下的径流量由1.04kg/min增大到3.02kg/min,雨强对径流量的影响显著;径流量和泥沙量随时间均呈现对数变化趋势;相同降雨历时下,坡面流随雨强和坡度的增大,从层流和缓流向紊流和急流发展,加剧了水土流失。耕作方式、雨强和坡度是影响黄土坡耕地侵蚀产沙过程及水力学特征的重要因素。因此,通过实施有效的保护性耕作、削弱坡度效应将有助于黄土坡耕地的水土保持。

The objective of this paper was to illustrate the mutual influence of runoff sediment characteristic as well as its hydraulic parameters under different slope gradients（5°,10°,15°,25°）,tillage measures（no treatment,artificial backhoe plowing,artificial digging plowing,contour tillage）and rainfall intensities（60mm/h,120mm/h）.Successive rainfall of 90-minutes duration was performed in the rainfall simulation laboratory of the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau.Runoff and sediment were collected once per two minutes when runoff came forth.Results showed that the amount of runoff and sediment of slopes with different tillage measures were in an order：no treatment artificial backhoe plowing artificial digging plowing contour tillage.This behavior illustrated that their soil water conservation effects enhanced sequentially.At loess slopes with same tillage method,their runoff increased significantly from 1.04kg/min to 3.02kg/min under the rainfall intensity of 120mm/h when compared with the rainfall intensity of 60mm/h,and the rainfall intensity had a great impact on runoff.Simultaneously,runoff and sediment amount were logarithmically increased with rainfall duration.Under the same rainfall duration,overland flow transformed from the transitional and subcritical flows to the turbulent and supercritical flows with the increase of rainfall intensity and slope gradient,thereby exacerbating the soil erosion.Tillage,rainfall intensity and slope gradient were critically important factors which affected slope erosion process,sediment yield and its hydraulics features.Thus,the adoption of effective conservation tillage,weakness of slope effect will contribute to the soil and water conservation at the loess sloping land on the Loess Plateau.