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

超过90%的地球陆地表面被风化层所覆盖，这是一层大小不等的颗粒，从巨石到粘土。这些粒子的大小分布是对地球表面环境的基本控制。在河道中，上游沉积物的粒度分布影响侵蚀速率、河道几何形状和水生生物的栖息地类型。在河流沉积物发源的山坡上，岩石和土壤的粒度分布影响水文响应、化学风化速率和植被类型。尽管它的重要性，我们有很少的数据和有限的理论，以告知山坡和河流沉积物颗粒的大小分布如何在景观变化的预测。 我的目标是开发一个全面的框架，了解地球表面颗粒的大小分布的演变，在控制其生产，运输和转换从源到汇的岩性，气候和地貌因素。我专注于构造活动，侵蚀景观，连接河流沉积物的山坡源的途径是最容易识别的。 该研究计划的第一个长期目标是量化控制山坡上产生的颗粒物粒径分布并提供给河流的因素。为此，我将：测量山坡颗粒大小在现场现场沿着梯度在三个关键控制因素-侵蚀率，气候和岩石类型;测试的假设，在基岩裂缝的间距设置的初始大小分布的颗粒进入山坡风化引擎;和挖掘数据从土壤数据库的山坡颗粒大小分布的大规模趋势。 我的第二个长期目标是开发一个基于过程的预测模型，用于研究沉积物通过河流网络运输时颗粒尺寸分布的演变。为了做到这一点，我将量化磨蚀导致的粒径减小过程如何取决于岩石强度以及沉积物混合物中粒径和形状的分布。 我还将建立方法，预测率的颗粒尺寸减少在现场设置按比例放大实验室的结果。 这些结果将使人们有可能测试的假设如何山坡，渠道和景观之间的反馈联系山坡风化和河流切割，这决定了景观如何演变的构造和气候强迫。预测各种地貌沉积物大小的能力也有助于解决许多实际问题，包括：恢复鲑鱼和其他水生生物的生境，这些生物的生命周期阶段取决于是否有特定的颗粒大小分布;预测和管理流入水库和其他水资源基础设施的沉积物;诊断和减轻伐木、修路和其他土地使用对沉积物的影响。

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.