Extreme event-driven sediment aggradation and erosional buffering along a tectonic gradient in southern Taiwan
Extreme event-driven sediment aggradation and erosional buffering along a tectonic gradient in southern Taiwan
复制标题
DOI：
10.1130/g49304.1
复制
发表时间：
2022-01-01
期刊：
影响因子：
5.8
通讯作者：
Rittenour, Tammy M.
中科院分区：
文献类型：
--
作者：
DeLisle, Clarke;Yanites, Brian J.;Rittenour, Tammy M.
在大多数景观演化模型中，极端降雨会增强河流下切。然而，在陡峭的景观中，这些事件会引发山体滑坡，通过增加沉积物输送和加积来缓冲切割。我们量化滑坡沉积物加积和侵蚀缓冲在台湾南部的自然实验，在构造活动的北向梯度驱动景观陡峭度增加。我们发现，景观响应极端降雨在2009年莫拉克台风变化沿着这个梯度，陡峭的地区经历了广泛的渠道沉积物淤积>10米，不太陡峭的地区没有明显的淤积。我们模拟沉积物出口，以估计沉积物去除的时间轴，并发现，陡峭的，构造活跃的地区，最加积可能需要几个世纪才能恢复基岩切口。预期的沉积物覆盖时间反映了构造抬升。我们发现，尽管高流功率，沉积物覆盖可能会保持陡峭的渠道侵蚀基岩长达一半的一个给定的时间段。这项工作突出了动态沉积物覆盖景观演变的重要性，并提出了一种机制，在构造活动的景观侵蚀效率可能会减少景观陡度的增加。
In most landscape evolution models, extreme rainfall enhances river incision. In steep landscapes, however, these events trigger landslides that can buffer incision via increased sediment delivery and aggradation. We quantify landslide sediment aggradation and erosional buffering with a natural experiment in southern Taiwan where a northward gradient in tectonic activity drives increasing landscape steepness. We find that landscape response to extreme rainfall during the 2009 typhoon Morakot varied along this gradient, where steep areas experienced widespread channel sediment aggradation of >10 m and less steep areas did not noticeably aggrade. We model sediment export to estimate a sediment removal timeline and find that steep, tectonically active areas with the most aggradation may take centuries to resume bedrock incision. Expected sediment cover duration reflects tectonic uplift. We find that despite high stream power, sediment cover may keep steep channels from eroding bedrock for up to half of a given time period. This work highlights the importance of dynamic sediment cover in landscape evolution and suggests a mechanism by which erosional efficiency in tectonically active landscapes may decrease as landscape steepness increases.