Modelling how sediment suspension controls the morphology and evolution of sand-bed rivers

模拟沉积物悬浮如何控制沙床河流的形态和演化

基本信息

批准号：
NE/L005441/1
负责人：
Gregory Sambrook Smith
金额：
$ 8.16万
依托单位：
University of Birmingham
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2015
资助国家：
英国
起止时间：
2015 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FL005441%2F1
关键词：
Modelling how sediment suspension controls

项目摘要

Sand-bed rivers dominate the drainage of the Earth's surface. For example, the world's 10 largest rivers, that drain almost 20% of global continental land & deliver 33% of the terrestrial sediment supplied to the oceans, are all sand-bed channels. Many river catchments, in which sand-bed channels are present, are subject to anthropogenic activities such as dam construction, water abstraction, river engineering, or deforestation. As a result, the rivers in these catchments can experience sudden and catastrophic environmental problems such as major bank retreat that promotes building collapse, river bed aggradation and flooding, and channel shifting that leads to habitat degradation. Despite the environmental, social and economic significance of these rivers, we have struggled to produce robust models of how sand-bed rivers work, how they transport their sediment, how rivers change over decades and centuries, how they produce the variety of channel patterns we see in the world, and how rivers respond to a change in environmental drivers such as climate, erosion rates and human interference.Very recent research indicates that the morphology, functioning and pattern of sand-bed rivers is strongly dependent upon whether the sand that they carry is transported in suspension (i.e. carried in the water column) or as bedload (moving in contact with the bed). In addition, theory suggests that, over the range of sediment sizes and flow conditions that are typical of sand-bed rivers, there is a dramatic shift from bedload to suspension-dominated sand transport. However, the physical mechanisms that control the link between how sand is transported and the resulting river morphology remain largely unexplained. This project will develop new models and quantitative understanding of the role of sediment suspension as a control on the morphology of sand-bed rivers. We will do this by implementing a research strategy that involves three key elements: First, we will apply an innovative image acquisition technique to obtain datasets that quantify river bed morphology at very high spatial resolutions (cm) over large areas (km) and multiple timescales (days to years). Second, we will use state-of-the-art field instrumentation to obtain concurrent measurements of flow and sediment transport processes and their relationship to river morphology over a range of discharges. Third, we will develop and apply two- and three-dimensional numerical models to quantify the interactions between riverine processes and channel morphology at bedform, bar and whole river scales. We will use field datasets to test our models in sand-bed rivers of different sizes and with contrasting flow regimes and bed sediment texture. Once validated, our models will provide robust new tools, which we will release as open-source code to the scientific community, for predicting and understanding how sand-bed rivers respond to environmental change. This research will also have significant end-user and educational benefits, which we will realise by working closely with project partner HR Wallingford, and by producing a collection of high-quality learning materials and teaching resources aimed at the Geography A-level curriculum, and released via national organisations with a strong commitment to educational outreach.

砂河统治着地球表面的排水。例如，全球10个最大的河流耗尽了近20％的全球大陆土地，并提供了向海洋供应的陆地沉积物的33％，都是沙床通道。许多存在沙床通道的河流集水区都受到人为活动，例如大坝建设，抽象，河流工程或森林砍伐。结果，这些集水区中的河流可能会遇到突然而灾难性的环境问题，例如主要的银行撤退，促进建筑物的崩溃，河床膨胀和洪水，以及导致栖息地退化的渠道转移。尽管这些河流具有环境，社会和经济意义，但我们仍在努力制作出强大的模型，以了解沙床河流如何运作，它们如何运输沉积物，数十年和几个世纪的河流如何变化，它们如何产生我们在世界上看到的各种渠道模式，以及河流如何对环境驱动因素的变化响应，例如，诸如气候，人类互动率的变化。强烈依赖于它们携带的沙子是在悬浮液中运输的（即在水柱中携带）还是作为床负荷（与床接触）。此外，理论表明，在沙床河流典型的沉积物大小和流动条件范围内，从床载到悬挂式主导的沙子运输的急剧转移。但是，控制沙子运输方式与由此产生的河流形态之间联系的物理机制在很大程度上无法解释。该项目将对沉积物悬浮液作为对沙床河流形态的控制的作用的新模型和定量理解。我们将通过实施涉及三个关键要素的研究策略来做到这一点：首先，我们将采用创新的图像采集技术来获取在很高的空间分辨率（CM）上量化河床形态（CM）的数据集（km）和多个时间表（天数到一年）。其次，我们将使用最先进的现场仪器来获得对流量和沉积物传输过程的同时测量，以及它们与河流形态的关系在一系列排放范围内。第三，我们将开发和应用二维数值模型，以量化床形，棒和整个河流尺度的河流过程与通道形态之间的相互作用。我们将使用现场数据集在不同尺寸的沙床河中测试我们的模型，并具有对比度的流程和床质质地。一旦得到验证，我们的模型将提供强大的新工具，我们将向科学界发布作为开源代码，以预测和了解沙床河流如何应对环境变化。这项研究还将具有重大的最终用户和教育福利，我们将通过与项目合作伙伴HR Wallingford紧密合作，并生产旨在旨在地理A级课程的高质量学习材料和教学资源的集合，并通过国家组织发行，并通过具有强烈的教育公开承诺来发布。