Erosion pavements occur commonly in many semiarid watersheds due to selective erosion. However, quantitative information regarding the dynamic feedback between soil erosion, surface morphology, and flow hydraulics as erosion pavement develops is limited. In order to quantify the spatiotemporal evolution of rock cover and surface roughness, and measure their effects on flow velocities as erosion pavement develops, a series of rainfall simulations were conducted on a 2 by 6.1 m soil plot under three slope treatments (5%, 12%, and 20%) with surface elevation and rock cover measurements. The total applied rainfall volume for each experimental replication ranging from 1,400 to 2,240 mm caused the development of erosion pavement. The results showed (1) rock cover increased from 15% to 90% as rainfall progressed, and the terminal rock cover was not slope gradient dependent; (2) random roughness was positively correlated with rock cover in the upper and middle plot sections, and increasing surface roughness and rock cover reduced the flow velocity following power functions; (3) surface roughness in the lower sections did not uniformly increase with increasing rock cover due to the formation of rills; (4) the terminal surface roughness values of full plots were 5.3 and 5.1 mm, 4.2 and 4.5 mm, and 2.9 and 3.2 mm for replications of 20%, 12%, and 5% slopes, respectively, indicating that steeper slopes produced greater surface roughness; (5) flow velocities measured at the end of experiments reached a relative constant value that was a function of unit flow rates alone for a given section; (6) hydraulic resistances were correlated with flow discharge, slope gradient, and rock cover, exhibiting no unique hydraulic coefficient for a given surface condition. These results improve our understanding of the evolution of semiarid hillslopes.

中文翻译：

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模拟降雨条件下石质土壤岩石覆盖、表面粗糙度和流速的演变

由于选择性侵蚀，侵蚀路面常见于许多半干旱流域。然而，随着侵蚀路面的发展，关于土壤侵蚀、表面形态和流动水力学之间的动态反馈的定量信息是有限的。为了量化岩石覆盖和表面粗糙度的时空演变，并测量随着侵蚀路面的发展它们对流速的影响，在三个坡度处理（5%、12 % 和 20%）与表面高程和岩石覆盖测量。每个实验重复的总应用降雨量从 1,400 到 2,240 毫米不等，导致侵蚀路面的发展。结果显示 (1) 随着降雨的进行，岩石覆盖率从 15% 增加到 90%，末端岩层不依赖坡度；(2) 随机粗糙度与上、中小区断面岩石覆盖率呈正相关，增加地表粗糙度和岩石覆盖率降低了流速服从幂函数；(3) 由于细沟的形成，下部地表粗糙度没有随着岩石覆盖层的增加而均匀增加；(4) 对于 20%、12% 和 5% 坡度的重复，完整地块的终端表面粗糙度值分别为 5.3 和 5.1 mm、4.2 和 4.5 mm 以及 2.9 和 3.2 mm，表明越陡峭的坡度产生越大的表面粗糙度；(5) 在实验结束时测得的流速达到一个相对恒定的值，该值是给定部分的单独单位流速的函数；(6) 水力阻力与流量相关，坡度和岩石覆盖层，对于给定的地表条件不表现出独特的水力系数。这些结果提高了我们对半干旱山坡演化的理解。