Quantifiable effectiveness of experimental scaling of river-and delta morphodynamics and stratigraphy
Quantifiable effectiveness of experimental scaling of river-and delta morphodynamics and stratigraphy
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DOI：
10.1016/j.earscirev.2014.03.001
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发表时间：
2014-06-01
影响因子：
12.1
通讯作者：
Cheshier, Nathan
中科院分区：
文献类型：
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作者：
Kleinhans, Maarten G.;van Dijk, Wout M.;Cheshier, Nathan
模拟地貌和地层的实验室实验往往受到尺度效应的影响，因为缩短长度和时间尺度会导致水和沉积物的不同行为。传统上，缩放是从运动方程和泥沙输运的量纲分析开始的，稍有让步，如垂直长度比例失真，就能得到可接受的结果。在过去的十年中，许多实验严重违反了这些尺度规则，但仍然产生了重要的和有见地的结果，这些结果以可量化的方式类似于真实的世界。在这里，我们专注于实验中的自生河道和河道模式。本文的目的是：1）确定哪些方面的缩放考虑是最重要的实验，模拟河流和三角洲的形态动力学和地层学，2）建立一个设计策略的实验的基础上结合放松的经典比例尺规则，酒吧和曲折的理论，小规模的实验集中在特定的过程。我们提出了一些小的实验室设置和协议，我们使用快速量化的侵蚀和沉积类型的形式和动态，在景观实验中开发的功能的详细属性，如有效的材料强度，并评估潜在的规模效应。最重要的是，河道的宽深比决定了沙坝的形态和曲流倾向。河漫滩材料的强度决定了这些河道的尺寸，理论预测，实验室河流的宽深比应该比相同的酒吧模式大1.5倍。我们展示了如何河漫滩的形成可以通过添加粉砂大小的silicaflour，膨润土，苜蓿（紫花苜蓿）或部分水解聚丙烯酰胺（合成聚合物），以不良分选沉积物控制。实验表明，有一个狭窄的范围内的条件之间没有流动性的床或银行，太多的流动性。植被的密度和淤泥的体积比例允许很好地控制通道尺寸，而聚合物被证明难以控制。这里提出的理论，详细的量化方法和实验设置表明，在实验室中创建的河流和三角洲似乎表现为天然河流时，实验条件下，坚持宽松的缩放规则，这里确定的，所需类型的河流三角洲形态动力学可以复制的基础上选择的一系列小规模实验的基础上的条件和沉积物。(c)2014爱思唯尔有限公司版权所有。
Laboratory experiments to simulate landscapes and stratigraphy often suffer from scale effects, because reducing length- and time scales leads to different behaviour of water and sediment. Classically, scaling proceeded from dimensional analysis of the equations of motion and sediment transport, and minor concessions, such as vertical length scale distortion, led to acceptable results. In the past decade many experiments were done that seriously violated these scaling rules, but nevertheless produced significant and insightful results that resemble the real world in quantifiable ways. Here we focus on self-formed fluvial channels and channel patterns in experiments. The objectives of this paper are 1) to identify what aspects of scaling considerations are most important for experiments that simulate morphodynamics and stratigraphy of rivers and deltas, 2) to establish a design strategy for experiments based on a combination of relaxed classical scale rules, theory of bars and meanders, and small-scale experiments focussed at specific processes. We present a number of small laboratory setups and protocols that we use to rapidly quantify erosional and depositional types of forms and dynamics that develop in the landscape experiments as a function of detailed properties, such as effective material strength, and to assess potential scale effects. Most importantly, the width-to-depth ratio of channels determines the bar pattern and meandering tendency. The strength of floodplain material determines these channel dimensions, and theory predicts that laboratory rivers should have 1.5 times larger width-to-depth ratios for the same bar pattern. We show how floodplain formation can be controlled by adding silt-sized silicaflour, bentonite, Medicago sativa (alfalfa) or Partially Hydrolyzed PolyActylamide (a synthetic polymer) to poorly sorted sediment. The experiments demonstrate that there is a narrow range of conditions between no mobility of bed or banks, and too much mobility. The density of vegetation and the volume proportion of silt allow well-controllable channel dimensions whereas the polymer proved difficult to control. The theory, detailed methods of quantification, and experimental setups presented here show that the rivers and deltas created in the laboratory seem to behave as natural rivers when the experimental conditions adhere to the relaxed scaling rules identified herein, and that required types of fluvio-deltaic morphodynamics can be reproduced based on conditions and sediments selected on the basis of a series of small-scale experiments. (c) 2014 Elsevier B.V. All rights reserved.