Hillslope topographic change in response to climate and climate change is a key aspect of landscape evolution. The impact of short-duration rainstorms on hillslope evolution in arid regions is persistently questioned but often not directly examined in landscape evolution studies, which are commonly based on mean climate proxies. This study focuses on hillslope surface processes responding to rainstorms in the driest regions of Earth. We present a numerical model for arid, rocky hillslopes with lithology of a softer rock layer capped by a cliff-forming resistant layer. By representing the combined action of bedrock and clast weathering, cliff-debris ravel, and runoff-driven erosion, the model can reproduce commonly observed cliff-profile morphology. Numerical experiments with a fixed base level were used to test hillslope response to cliff-debris grain size, rainstorm intensities, and alternation between rainstorm patterns. The persistence of vertical cliffs and the pattern of sediment sorting depend on rainstorm intensities and the size of cliff debris. Numerical experiments confirm that these two variables could have driven the landscape in the Negev Desert (Israel) toward an observed spatial contrast in topographic form over the past 10⁵–10⁶ years. For a given total storm rain depth, short-duration higher-intensity rainstorms are more erosive, resulting in greater cliff retreat distances relative to longer, low-intensity storms. Temporal alternation between rainstorm regimes produces hillslope profiles similar to those previously attributed to Quaternary oscillations in the mean climate. We suggest that arid hillslopes may undergo considerable geomorphic transitions solely by alternating intra-storm patterns regardless of rainfall amounts.

中文翻译：

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暴雨强度和时间模式对旱地盖层悬崖持续性和山坡形态的影响

响应气候和气候变化的山坡地形变化是景观演化的一个关键方面。短期暴雨对干旱地区山坡演化的影响一直受到质疑，但在景观演化研究中往往没有直接检验，这些研究通常基于平均气候代理。这项研究的重点是地球最干燥地区暴雨响应的山坡表面过程。我们提出了一个干旱、岩石山坡的数值模型，其岩性为较软的岩石层，上面有悬崖形成的抵抗层。通过表示基岩和碎屑风化、悬崖碎片崩解和径流驱动侵蚀的综合作用，该模型可以再现常见观察到的悬崖剖面形态。采用固定基准面的数值实验来测试山坡对悬崖碎片颗粒尺寸、暴雨强度和暴雨模式交替的响应。垂直悬崖的持续存在和沉积物分类的模式取决于暴雨强度和悬崖碎片的大小。数值实验证实，这两个变量可能推动内盖夫沙漠（以色列）的景观在过去 10 ⁵ –10 ⁶ 年中观察到地形形式的空间对比。对于给定的总暴雨深度，短时高强度暴雨的侵蚀性更强，导致相对于较长时间、低强度的暴雨来说，悬崖后退距离更大。暴雨状态之间的时间交替产生的山坡剖面与之前归因于平均气候第四纪振荡的山坡剖面相似。我们认为，无论降雨量如何，干旱山坡仅通过交替风暴内模式就可能经历相当大的地貌转变。