Climatic and Autogenic Controls on the Morphodynamics of Mega-Rivers: Modelling Sediment Flux in the Alluvial Transfer Zone

巨型河流形态动力学的气候和自生控制：冲积转移带沉积物通量建模

• 批准号: NE/J021571/1
• 负责人: Rolf Aalto
• 金额: $ 26.8万
• 依托单位: UNIVERSITY OF EXETER
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FJ021571%2F1
• 关键词: Climatic; Autogenic; Controls; Morphodynamics; Mega

The world's largest rivers transport ~19 billion tonnes of sediment each year, with a significant fraction being sequestered in the large deltas that are home to 14% of the world's population. Most (>70%) of these large deltas are under threat from rising sea levels, ground surface subsidence & declining riverine sediment supply required for delta construction. However, while measurements & projections of sea level rise & subsidence exist for many deltas, data quantifying historic changes in fluvial sediment supply are sparse, limiting our understanding of how delta building is related to climatic fluctuations. This situation reflects the complexity of controls on river sediment loads, which include the influence of climate & land use change in upland areas, dam construction, & flood driven storage & remobilisation of sediment within the extensive floodplains that characterise the lowland reaches ("sediment transfer zones") of the world's major rivers. This project will provide the first comprehensive quantification of these controls on riverine sediment fluxes for one of the world's largest rivers (the Mekong), leading to new generic understanding of the relationships between climatic variability, fluvial processes & sediment flux to deltaic zones & the ocean.To meet this aim we will develop a new generic simulation model that will, for the very first time, quantify the effects of climatic & morphological controls on all individual components, & at sub-annual resolution, of the alluvial sediment transfer budget of a large river. The approach is to use a hydrological model to predict sediment supplied from the catchment to the head of the river's sediment transfer reach (the part of a river that links sediment source areas upstream with sediment sinks downstream). Within the transfer reach the model will account for the key morphodynamic processes of river bed & bank erosion, & floodplain sedimentation, which either supply material to the transfer reach, or store the material for later release. The model will be parameterised & validated using targeted field data that we will collect in this proposal. We will run the model to explore historical trends of within-reach sediment fluxes over a multi-decadal period encompassing the last 50+ yrs. The data derived from our simulation model will be unique: the very first annually resolved mega-river sediment budget encompassing a multi-decadal period. These data will enable us to explore a series of specific research questions: What is the net effect on the Mekong sediment load of sediment exchanges within the alluvial transfer reach? Do sediment fluxes associated with floodplain storage & bank erosion promote a net increase or reduction in efflux from the transfer zone? How large is this modulating effect in both absolute & relative terms? How strong is the interannual variability in this modulation, & what factors drive this? In fact, we expect interannual variability to reflect the net effect of changes in the various components of the budget linked to specific climate indices that control each component. This will be explored by testing specific hypotheses concerning (i) the role of specific modes of climate variability (Indian Ocean Dipole & the El-Niño Southern Oscillation) in modulating sediment transfer, and; (ii) the ways in which extreme events (associated with tropical cyclones) control river bank erosion & floodplain deposition. Predicting fluvial sediment transfer through one of the world's great rivers is a scientific challenge that is novel, timely & significant. Addressing this challenge will improve our ability to predict sediment transfer from 'source-to-sink' thereby aiding (i) interpretations of floodplain sedimentary records, (ii) understanding of how sediment, nutrient & carbon fluxes respond to climate, (iii) assessment of changes in flood risk within deltas, & (iv) the physical processes by which ecosystem services within large rivers are sustained.

全球最大的河流每年运输约190亿吨的沉积物，其中很大一部分在大型三角洲的占地面积，这是全球14％的人口。这些大三角洲中的大多数（> 70％）受到海平面上升，地面沉降和河流沉积物供应的威胁。然而，尽管许多三角洲的海平面上升和沉降的测量和项目，但量化河流沉积物供应历史变化的数据却很少，这限制了我们对三角洲建筑如何与杂交波动有关的理解。这种情况反映了对河流沉积物负荷的控制的复杂性，其中包括高地地区气候和土地利用变化的影响，大坝建设以及洪水驱动驱动器的存储和延误沉积物在广泛的洪泛区内，这表征了世界主要河流的低地覆盖范围（“沉积物转移区”）。该项目将为世界上最大的河流之一（湄公河）提供对河流沉积物通量的这些控制的首次全面量化，从而使对气候变化，河流过程和沉积物通量之间的关系有了新的一般理解，以达到三角洲的Zones＆Ocean。 ＆以年底分辨率，大河的冲积沉积物转移预算。该方法是使用液压模型来预测从集水区到河流沉积物转移范围的沉积物（这是将沉积物源区域上游与沉积物下游连接到下游的河流的一部分）。在转移范围内，该模型将说明河床和河岸侵蚀的关键形态动力学过程，以及洪泛区沉积物，这些过程要么为转移范围提供材料，要么存储材料以供以后释放。该模型将使用我们将在此建议中收集的目标字段数据进行参数化和验证。我们将运行该模型，以探索在涵盖最后50年以上的多年期间，探索范围内沉积物通量的历史趋势。从我们的仿真模型中得出的数据将是唯一的：每年第一次解决的大型河流沉积物预算包括多年时期。这些数据将使我们能够探索一系列具体的研究问题：在冲积转移到达内沉积物交换的湄公河沉积物负载的净影响是什么？与洪泛区储存和银行侵蚀相关的沉积物通量会促进转移区的净增加或减少净值吗？这种调节效果在绝对和相对术语中有多大？该调制的年际变异性有多强？实际上，我们预计年际变异性会反映与控制每个组件的特定气候指数相关的预算组成部分变化的净效应。这将通过测试有关（i）气候变异性特定模式（印度洋偶极子和El-NiñoSouthern振荡）在调节沉积物转移中的特定模式的作用来探讨这一点， （ii）极端事件（与热带气旋相关）控制河岸侵蚀和洪泛区沉积的方式。通过世界上一条巨大的河流预测河流沉积物的转移是一项科学挑战，是新颖，及时和重要的。应对这一挑战将提高我们预测沉积物从“源到源”转移的能力，从而有助于（i）对洪泛区沉积记录的解释，（ii）理解沉积物，营养和碳通量如何应对气候的响应，（iii）评估三角架内洪水风险的变化，以及（iv）生态系统内部的物理过程中维持大型遗迹的物理过程。

项目成果

River bank instability from unsustainable sand mining in the lower Mekong River

• DOI: 10.1038/s41893-019-0455-3
• 发表时间: 2020-01-13
• 期刊: NATURE SUSTAINABILITY
• 影响因子: 27.6
• 作者: Hackney, Christopher R.;Darby, Stephen E.;Houseago, Robert C.
• 通讯作者: Houseago, Robert C.

Multiscale structure of meanders

• DOI: 10.1002/2016gl068238
• 发表时间: 2016-04
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: B. Vermeulen;A. Hoitink;G. Zolezzi;J. Abad;R. Aalto

Source-to-sink research: economy of the Earth's surface and its strata

• DOI: 10.1016/j.earscirev.2015.11.010
• 发表时间: 2016-02
• 期刊: Earth-Science Reviews
• 影响因子: 12.1
• 作者: J. Walsh;P. Wiberg;R. Aalto;C. Nittrouer;S. Kuehl