Abstract Rainfall or snow-melted water recharge easily saturates loose top soils with a less permeable underlayer, such as cultivated soil slope and partially thawed top soil layer, and thus, may influence the velocity of water flow. This study suggested a methodology and device system to supply water from the bottom soil layer at the different locations of slopes. Water seeps into and saturates the soil, when the water level is controlled at the same height of the soil surface. The structures and functions of the device, the components, and the operational principles are described in detail. A series of laboratory experiments were conducted under slope gradients of 5°, 10°, 15°, and 20° and flow rates of 2, 4, and 8 L min−1 to measure the water flow velocities over eroding and non-eroded loess soil slopes, under saturated conditions by using electrolyte tracing. Results showed that flow velocities on saturated slopes were 17% to 88% greater than those on non-saturated slopes. Flow velocity increased rapidly under high flow rates and slope gradients. Saturation conditions were suitable in maintaining smooth rill geomorphology and causing fast water flow. The saturated soil slope had a lubricant effect on the soil surface to reduce the frictional force, resulting in high flow velocity. The flow velocities of eroding rills under different slope gradients and flow rates were approximately 14% to 33% lower than those of non-eroded rills on saturated loess slopes. Compared with that on a saturated loess slope, the eroding rill on a non-saturated loess slope can produce headcuts to reduce the flow velocity. This study helps understand the hydrodynamics of soil erosion and sediment transportation of saturated soil slopes.

中文翻译：

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侵蚀作用下沿饱和黄土斜坡的水流速度

摘要 降雨或融雪水补给容易使松散的表层土壤饱和，底层渗透性较差，如耕作土壤坡度和部分融化的表层土壤层，从而可能影响水流速度。这项研究提出了一种方法和设备系统，可以从斜坡不同位置的底部土层供水。当水位控制在与土壤表面相同的高度时，水会渗入并浸透土壤。详细描述了该装置的结构和功能、部件和工作原理。在5°、10°、15°和20°的坡度和2、4和8 L min-1的流速下进行了一系列实验室实验，以测量侵蚀和未侵蚀黄土上的水流速度土壤坡度，在饱和条件下使用电解质示踪。结果表明，饱和斜坡上的流速比非饱和斜坡上的流速高 17% 到 88%。在高流速和坡度梯度下流速迅速增加。饱和条件适宜维持细沟地貌平整，水流较快。饱和土壤坡度对土壤表面有润滑作用，减少摩擦力，导致高流速。不同坡度和流速下侵蚀细沟的流速比饱和黄土边坡上的未侵蚀细沟低约14%～33%。与饱和黄土斜坡相比，非饱和黄土斜坡上的侵蚀细沟会产生切头，降低流速。