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: Concordia University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=715583
• 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%的地球陆地表面被风化层覆盖，风化层是一层颗粒，大小从巨石到粘土不等。这些颗粒的大小分布是对地球表面环境的基本控制。在河道中，上游提供的沉积物的大小分布影响着侵蚀速率、河道几何形状和水生生物可获得的栖息地类型。在河流沉积物起源的山坡上，岩石和土壤的大小分布影响水文反应、化学风化速率和植被类型。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大小分布如何在不同的景观中变化。