Coarse sediment dynamics in a large glaciated river system: Holocene history and storage dynamics dictate contemporary climate sensitivity
Coarse sediment dynamics in a large glaciated river system: Holocene history and storage dynamics dictate contemporary climate sensitivity
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大型冰川河流系统中的粗沉积物动态：全新世历史和储存动态决定了当代气候敏感性
DOI：
10.1130/gsab.s.12616562.v1
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
K. Jaeger
中科院分区：
文献类型：
--
作者：
S. Anderson;K. Jaeger
怀特河的砾石层流经华盛顿州一个1279平方公里的盆地，低地由大陆冰川和活跃的冰川成层火山的源头雕刻而成。河口附近的冲积扇沿着的慢性淤积逐渐减少了洪水的输送。为了更好地了解预测的气候变化如何影响粗泥沙输送和淤积率在这个低地沉积环境中，我们评估了粗泥沙通过流域的当代输送和路由;这项评估是基于丰富的地形，沉积学，水文数据从过去的世纪，重点是重复高分辨率的地形调查，从过去的十年。
我们发现，大部分的下游河流的当代推移质通量起源于持续侵蚀的冲积层在较低的分水岭。这种侵蚀是对1906年发生在该扇上的一次大的撕脱造成的当地基准面下降的反应，随后的疏浚又使其扩大。1906年的撕脱和现代不平衡谷剖面反映了大陆冰川作用和大规模的中全新世拉哈尔的景观调节作用。在冰前源头，罕见的大沉积物脉冲已经完成了大部分观察到的粗沉积物出口，出口材料覆盖下游谷底，在典型的洪水，输送床材料主要来源于这些谷底洪水的侵蚀。在整个流域，我们观察到十年尺度的粗泥沙动态强烈相关的山谷规模的沉积物存储超过102-104年的时间尺度上的填充或排空，往往是在响应重大干扰，无论是安置大型存款或影响其重新分配。在大流域的准冰川响应建议是内在复杂的，间断的内部地形相互作用和随机/阈值依赖的事件的结果。我们认为，在结合，全新世扰动，存储动态，和人类流量的修改粗泥沙通量在较低的怀特河相对不敏感的年代际气候变化。结果突出了河流对当代干扰的敏感性，气候或其他方面，可能取决于当地和特殊的流域历史，强调需要解开这些历史，同时证明流域尺度的高分辨率地形的实用性。
The gravel-bedded White River drains a 1279 km2 basin in Washington State, with lowlands sculpted by continental glaciation and headwaters on an actively glaciated stratovolcano. Chronic aggradation along an alluvial fan near the river’s mouth has progressively reduced flood conveyance. In order to better understand how forecasted climate change may influence coarse sediment delivery and aggradation rates in this lowland depositional setting, we assessed the contemporary delivery and routing of coarse sediment through the watershed; this assessment was based on a rich set of topographic, sedimentologic, and hydrologic data from the past century, with a focus on repeat high-resolution topographic surveys from the past decade.
We found that most of the lower river’s contemporary bed-load flux originates from persistent erosion of alluvial deposits in the lower watershed. This erosion is a response to a drop in local base level caused by a major avulsion across the fan in 1906 and then augmented by subsequent dredging. The 1906 avulsion and modern disequilibrium valley profiles reflect landscape conditioning by continental glaciation and a massive mid-Holocene lahar. In the proglacial headwaters, infrequent large sediment pulses have accomplished most of the observed coarse sediment export, with exported material blanketing downstream valley floors; during typical floods, transported bed material is largely sourced from erosion of these valley floor floods. Throughout the watershed, we observe decadal-scale coarse sediment dynamics strongly related to the filling or emptying of valley-scale sediment storage over 102–104 yr time scales, often in response to major disturbances that either emplace large deposits or influence their redistribution. Paraglacial responses in large watersheds are suggested to be inherently complicated and punctuated as a result of internal landform interactions and stochastic/threshold-dependent events. We argue that, in combination, Holocene disturbance, storage dynamics, and human flow modification make coarse sediment fluxes in the lower White River relatively insensitive to decadal climate variability. Results highlight the degree to which river sensitivity to contemporary disturbance, climatic or otherwise, may be contingent on local and idiosyncratic watershed histories, underscoring the need to unpack those histories while demonstrating the utility of watershed-scale high-resolution topography toward that end.
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影响因子：
3.3
作者：
T. Heckmann;S. McColl;D. Morche
通讯作者：
T. Heckmann;S. McColl;D. Morche
高地沉积物级联的沉积物连续性：高地河流对极端洪水事件的地貌响应
影响因子：
3.9
作者：
Joyce H
通讯作者：
Joyce H
影响因子：
3.9
作者：
J. Carrivick;T. Heckmann
通讯作者：
J. Carrivick;T. Heckmann
影响因子：
3.3
作者：
Naylor L
通讯作者：
Naylor L