Waterfall height sets the mechanism and rate of upstream retreat
Waterfall height sets the mechanism and rate of upstream retreat
复制标题
瀑布高度决定了上游退却的机制和速度
作者：
Inoue, T.;Izumi, N.;Scheingross, J.S.;Hiramatsu, Y.;Tanigawa, S.;Sumner, T.
瀑布是河网中侵蚀最快的部分之一，但由于多种过程可能导致瀑布侵蚀，因此预测自然瀑布退缩率很困难。我们缺乏关于瀑布高度如何影响上游瀑布退缩机制和速度的数据。我们通过实验测试落差对瀑布后退的影响来解决这一知识差距。我们的实验表明，当基岩强度、沉积物供应和水流量恒定时，较短的瀑布后退速度比较高的瀑布快五倍。这种退缩率差异是由于侵蚀机制的变化造成的。短瀑布通过形成几个小的、快速侵蚀的基岩台阶（即循环台阶）而退缩，而高瀑布往往会形成大型基岩跌水池，其中侧向跌水池侵蚀允许头墙底切和随后的瀑布退缩。由于瀑布高度可以部分地由瀑布形成机制决定，因此我们的结果强调，瀑布后退的速度和随后的景观演变可以通过瀑布的形成过程来调节。
Waterfalls are among the fastest-eroding parts of river networks, but predicting natural waterfall retreat rates is difficult due to multiple processes that can drive waterfall erosion. We lack data on how waterfall height influences the mechanism and rate of upstream waterfall retreat. We addressed this knowledge gap with experiments testing the influence of drop height on waterfall retreat. Our experiments showed that shorter waterfalls retreat up to five times faster than taller waterfalls, when bedrock strength, sediment supply, and water discharge are constant. This retreat rate difference is due to a change in the erosion mechanism. Short waterfalls retreat by the formation of several small, rapidly eroding bedrock steps (i.e., cyclic steps), whereas tall waterfalls tend to form large bedrock plunge pools where lateral plunge pool erosion allows headwall undercutting and subsequent waterfall retreat. Because waterfall height can be partially set by the waterfall formation mechanism, our results highlight that the rate of waterfall retreat and subsequent landscape evolution can be modulated by the processes that form waterfalls.