Coarse sediment supply sets the slope of bedrock channels in rapidly uplifting terrain: Field and topographic evidence from eastern Taiwan
Coarse sediment supply sets the slope of bedrock channels in rapidly uplifting terrain: Field and topographic evidence from eastern Taiwan
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粗沉积物的供应决定了快速隆起地形中基岩河道的坡度：台湾东部的现场和地形证据
DOI：
10.1002/esp.5200
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发表时间：
2021
影响因子：
3.3
通讯作者：
J. Yen
中科院分区：
文献类型：
--
作者：
L. Lai;J. Roering;N. Finnegan;R. Dorsey;J. Yen
基岩河道的下切率和陡度取决于水流流量、抬升率、基底岩性、泥沙通量和推移质大小。然而，这些因素的相对作用和河道陡度对快速（>1 mm yr−1）隆升速率的敏感性仍然不清楚。我们对台湾东部沿海山脉沿着河流基岩河道进行了实地和地形分析，以评估对基岩河道陡度的控制，该地区的抬升速率为1.8 - 11.8 mm/年，降水量相对稳定（1.5-2.7 m/年）。我们发现，通道陡度是独立的岩石隆起率和年降水量，但增加单调与沉积物的大小和基底强度。此外，在具有均匀基底岩性（泥岩和复理石）的河段中，河道陡度随沉积物源岩而系统地变化，但不随河道宽度而变化。当应用于我们的数据时，机械切割模型（跃移磨蚀模型）表明，海岸山脉通道的陡度主要由粗沉积物供应决定。我们还观察到，较大的颗粒主要由来自火山岩和砾岩的抗岩性组成。这一结果表明，源区的山坡基岩性质通过该环境下粗泥沙的产生对近端河道的陡度产生了主要控制作用。我们认为，在快速上升的景观中，河道陡度可能对上升速率和流量不敏感，其中切割过程由粗泥沙尺寸和供应量决定。假设下切率和基底剪切应力（水流功率）之间成比例的模型可能无法完全捕获对滑坡主导景观中河流通道剖面的控制。可能需要除河道变陡以外的其他过程，如增强的推移质冲击和泥石流冲刷，以平衡这些运输限制系统中的岩石隆起和切割。
The incision rate and steepness of bedrock channels depend on water discharge, uplift rate, substrate lithology, sediment flux, and bedload size. However, the relative role of these factors and the sensitivity of channel steepness to rapid (>1 mm yr−1) uplift rates remain unclear. We conducted field and topographic analyses of fluvial bedrock channels with varying channel bed lithology and sediment source rock along the Coastal Range in eastern Taiwan, where uplift rates vary from 1.8 to 11.8 mm yr−1 and precipitation is relatively consistent (1.5–2.7 m yr−1), to evaluate the controls on bedrock channel steepness. We find that channel steepness is independent of rock uplift rate and annual precipitation but increases monotonically with sediment size and substrate strength. Furthermore, in reaches with uniform substrate lithology (mudstone and flysch), channel steepness systematically varies with sediment source rock but not with channel width. When applied to our data, a mechanistic incision model (saltation‐abrasion model) suggests that the steepness of Coastal Range channels is set primarily by coarse‐sediment supply. We also observe that larger particles are mainly composed of resistant lithologies derived from volcanic rocks and conglomerates. This result implies that hillslope bedrock properties in the source area exert a dominant control on the steepness of proximal channels through coarse‐sediment production in this setting. We propose that channel steepness may be insensitive to uplift rate and flow discharge in fast‐uplifting landscapes where incision processes are set by coarse sediment size and supply. Models assuming a proportionality between incision rate and basal shear stress (stream power) may not fully capture controls on fluvial channel profiles in landslide‐dominated landscapes. Processes other than channel steepening, such as enhanced bedload impacts and debris‐flow scour, may be required to balance rock uplift and incision in these transport‐limited systems.
影响因子：
5.3
作者：
Alexander B. Neely;R. DiBiase;L. Corbett;P. Bierman;M. Caffee
通讯作者：
Alexander B. Neely;R. DiBiase;L. Corbett;P. Bierman;M. Caffee
影响因子：
3.3
作者：
B. Yanites;N. Mitchell;J. Bregy;G. Carlson;Kirstyn Cataldo;Margaret Holahan;G. Johnston;A. Nelson;J. Valenza;M. Wanker
通讯作者：
B. Yanites;N. Mitchell;J. Bregy;G. Carlson;Kirstyn Cataldo;Margaret Holahan;G. Johnston;A. Nelson;J. Valenza;M. Wanker
不频繁移动的巨石在调节景观演化和地貌灾害中的作用
影响因子：
12.1
作者：
Shobe C
通讯作者：
Shobe C