Predicting the size distribution of sediments on hillslopes and rivers at the landscape scale

在景观尺度上预测山坡和河流沉积物的尺寸分布

• 批准号: RGPIN-2019-05501
• 负责人: Sklar, Leonard
• 金额: $ 4.2万
• 依托单位: Simon Fraser University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=738336
• 关键词: Predicting; size; distribution; sediments; hillslopes

Over 90% of Earth's land surface is covered by regolith, a blanket of particles ranging in size from boulders to clay. The size distribution of these particles is a fundamental control on Earth's surface environments. In a river channel, the size distribution of sediments supplied from upstream influences rates of erosion, channel geometry, and the type of habitats available to aquatic organisms. On hillslopes, where river sediments originate, the size distribution of rocks and soil influences hydrologic response, rates of chemical weathering and types of vegetation. Despite its importance, we have few data and limited theory to inform predictions of how the size distribution of hillslope and river sediment particles varies across landscapes. My goal is to develop a comprehensive framework for understanding the evolution of the size distributions of earth surface particles, in terms of the lithologic, climatic and geomorphic factors that control their production, transport and transformation from source to sink. I focus on tectonically active, erosional landscapes, where the pathways linking river sediments to their hillslope sources are most readily identified. The first long-term objective of this research program is to quantify the factors that control the size distributions of particles produced on hillslopes and supplied to rivers. To do this I will: measure hillslope particle size at field sites along gradients in three key controlling factors - erosion rate, climate, and rock type; test the hypothesis that the spacing of fractures in bedrock sets the initial size distribution of particles entering the hillslope weathering engine; and mine data from soils databases for landscape-scale trends in hillslope particle size distributions. My second long-term objective is to develop a process-based, predictive model for how particle size distributions evolve as sediments are transported through river networks. To do this I will quantify how the process of particle size reduction by abrasion depends on rock strength, and on the distributions of particle sizes and shapes in sediment mixtures. I will also establish methods for predicting rates of particle size reduction in field settings by scaling-up from laboratory results. These results will make it possible to test hypotheses for how hillslopes, channels and landscapes are linked by feedbacks between hillslope weathering and river incision, which determine how landscapes evolve in response to tectonic and climatic forcing. The ability to predict sediment size across landscapes can also help solve many practical problems, including: restoring habitat of salmonids and other aquatic organisms with life cycle stages that depend on availability of specific particle size distributions; predicting and managing sediment inputs to reservoirs and other water resources infrastructure; and diagnosing and mitigating sediment-related impacts of logging, road building and other land uses.

超过 90% 的地球表面被风化层覆盖，风化层是一层从巨石到粘土的颗粒层。这些颗粒的尺寸分布是对地球表面环境的基本控制，在河道中，沉积物的尺寸分布。上游影响侵蚀速率、河道几何形状以及水生生物的栖息地类型。在河流沉积物的发源地山坡上，岩石和土壤的尺寸分布影响水文响应、化学风化速率和水生生物类型。尽管它很重要，但我们几乎没有数据和有限的理论来预测山坡和河流沉积物颗粒的尺寸分布如何在景观中变化。我的目标是开发一个全面的框架来了解地球表面尺寸分布的演变。就控制颗粒的产生、运输和从源头到汇的转化的岩性、气候和地貌因素而言，我关注的是构造活跃的侵蚀景观，在这些景观中，最容易识别出连接河流沉积物与其山坡源头的路径。该研究计划的第一个长期目标是量化控制山坡上产生并供应给河流的颗粒尺寸分布的因素。为此，我将：沿三个关键控制因素的梯度测量山坡颗粒尺寸。侵蚀率、气候和岩石类型；测试基岩裂缝间距决定进入山坡风化引擎的颗粒的初始尺寸分布的假设；以及来自土壤数据库的矿山数据，以了解山坡颗粒尺寸分布的景观尺度趋势。第二长期目标是开发一个基于过程的预测模型，用于了解沉积物通过河流网络输送时颗粒尺寸分布如何演变。为此，我将量化磨损导致颗粒尺寸减小的过程如何取决于岩石强度和岩石强度。我还将通过扩大实验室结果来建立预测现场环境中颗粒尺寸减小率的方法，这些结果将使测试关于山坡、河道和景观如何变化的假设成为可能。通过山坡之间的反馈联系起来风化和河流切割，决定了地貌如何响应构造和气候强迫而演变。预测地貌中沉积物大小的能力还可以帮助解决许多实际问题，包括：恢复鲑鱼和其他水生生物的栖息地，其生命周期阶段取决于特定粒度分布的可用性；预测和管理水库和其他水资源基础设施的沉积物输入；以及诊断和减轻伐木、道路建设和其他土地利用与沉积物相关的影响。