Landslides control the spatial and temporal variation of channel width in southern Taiwan: Implications for landscape evolution and cascading hazards in steep, tectonically active landscapes
Landslides control the spatial and temporal variation of channel width in southern Taiwan: Implications for landscape evolution and cascading hazards in steep, tectonically active landscapes
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DOI：
10.1002/esp.4353
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发表时间：
2017-12
影响因子：
3.3
通讯作者：
B. Yanites;N. Mitchell;J. Bregy;G. Carlson;Kirstyn Cataldo;Margaret Holahan;G. Johnston;A. Nelson;J. Valenza;M. Wanker
中科院分区：
文献类型：
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作者：
B. Yanites;N. Mitchell;J. Bregy;G. Carlson;Kirstyn Cataldo;Margaret Holahan;G. Johnston;A. Nelson;J. Valenza;M. Wanker
强烈的降水或地震事件可以在整个景观中产生聚集的质量运动过程。这些罕见的事件对景观有重大影响，然而，这些事件的罕见性导致它们在一系列时间尺度上如何影响整个地貌系统的不确定性。台湾地势陡峭，构造活跃，容易发生山崩和泥石流，特别是在遭遇暴雨事件时。台风莫拉克于2009年8月登陆台湾，在台湾南部造成大面积山体滑坡。台湾南部山谷地形由南向北的趋势导致滑坡敏感性的空间变异，这为推断此类滑坡事件对河道形态的长期影响提供了机会。我们使用台风前和台风后的图像来量化这个事件对通道宽度的传播影响，因为碎片是通过景观路由。研究结果显示，台湾南部沿着走向的20个盆地中，以河川宽度（包括台风前后）与山坡坡度的型态为基础，显示山崩造成的连锁灾害对景观演化的重要性。在莫拉克台风之前，研究区域中部的河道比南部的河道宽约3-10倍。台风过后，这些中央至北方盆地的沉积和加宽也达到最大值，这些盆地的山坡坡度和河道陡度都很高，突出了台风前的模式。结果进一步表明，西北航道位于航道陡度最低的地方，这一观察结果与河流演变的分离限制模型不一致。我们推断，这种模式表明沉积物供应和相关的滑坡事件对长期河道演变具有重要作用。这些研究结果在一系列的空间和时间尺度，包括了解级联的危险在陡峭的景观和地貌解释的通道形态的影响。版权所有© 2018约翰威利父子有限公司
Intense precipitation or seismic events can generate clustered mass movement processes across a landscape. These rare events have significant impacts on the landscape, however, the rarity of such events leads to uncertainty in how they impact the entire geomorphic system over a range of timescales. Taiwan is steep, tectonically active, and prone to landslide and debris flows, especially when exposed to heavy rainfall events. Typhoon Morakot made landfall in Taiwan in August of 2009, causing widespread landslides in southern Taiwan. The south to north trend in valley relief in southern Taiwan leads to spatial variability in landslide susceptibility providing an opportunity to infer the long‐term impact of such landslide events on channel morphology. We use pre‐ and post‐typhoon imagery to quantify the propagating impact of this event on channel width as the debris is routed through the landscape. The results show the importance of cascading hazards from landslides on landscape evolution based on patterns of channel width (both pre‐ and post‐typhoon) and hillslope gradients in 20 basins along strike in southern Taiwan. Prior to Typhoon Morakot, the river channels in the central part of the study area were about 3–10 times wider than the channels in the south. Following the typhoon, aggradation and widening was also a maximum in these central to northern basins where hillslope gradients and channel steepness is high, accentuating the pre‐typhoon pattern. The results further show that the narrowest channels are located where channel steepness is the lowest, an observation inconsistent with a detachment‐limited model for river evolution. We infer this pattern is indicative of a strong role of sediment supply, and associated landslide events, on long‐term channel evolution. These findings have implications across a range of spatial and temporal scales including understanding the cascade of hazards in steep landscapes and geomorphic interpretation of channel morphology. Copyright © 2018 John Wiley & Sons, Ltd.