Diffusive Soil Transport and Hillslope Evolution

PI将追求与生物活动和表面雨水飞溅相关的扩散土壤运输和山坡演变的综合理论，建立在山坡地貌学最近的主要发展基础上。 他们的目标是：（i）澄清构成的基本要素和形式描述这些过程的（迁移）定律，说明迁移与地表坡度或土壤厚度与地表坡度的乘积成比例的条件;（ii）为山坡演变模型中所用的类扩散系数提供动力学理论的类似物，证明它是土壤颗粒活性、颗粒大小、土壤孔隙度和土壤厚度的显式非线性函数，并与气候和生物条件间接相关; ㈢利用高速录像和粒子跟踪技术，通过实验获得雨溅迁移的本构律形式; ㈣说明粒子活动梯度在产生迁移方面的基本意义，并在雨滴情况下使用沙盒实验，在地下迁移情况下使用土壤特性和示踪粒子的实地测量来证明这一点;（v）阐明表面和次表面颗粒扩散、混合和分类的成分，说明这些过程如何促成山坡连锁结构;及（vi）发展一个先进的扩散输送及山坡演变计算模式，以探讨陆面几何形状、土壤输送、土壤厚度及土壤生产之间的全面耦合，包括对外界及边界强迫的非线性反应。 这个为期四年的计划将网状理论，实验，实地和计算组件。 PI的理论工作将侧重于澄清：（一）颗粒分散，混合和分选土壤深度和连锁规模的成分;和（二）本构运输法的形式。 专业人员的实验/实地工作将：（一）侧重于雨水飞溅的过程，以及土壤内和土壤表面的颗粒混合和分选;（二）旨在测试/验证其工作的理论和计算方面。 他们还将应用基于不连续谱元素方法的高性能算法，开发先进的计算代码，用于模拟土壤深度尺度上的颗粒行为，以及模拟地貌尺度上的山坡演变。 在地球表面过程中心的主持下，该项目将涉及地貌学、流体力学、应用数学和高级计算方面的科学家专家的合作。 这项工作的结果将构成一个主要的，关键的，对山坡地貌学日益增长的理论基础的贡献。

PIs will pursue a comprehensive theory of diffusive soil transport and hillslope evolution associated with biological activity and surface rainsplash, building on recent, key developments in hillslope geomorphology. Their objectives are: (i) to clarify the fundamental ingredients and forms of constitutive (transport) laws describing these processes, demonstrating the conditions under which transport is proportional to the land-surface gradient or to the product of the soil thickness and surface gradient; (ii) to provide the analogue of a kinetic theory for the diffusion-like coefficient used in hillslope evolution models, demonstrating how it is an explicit nonlinear function of soil-particle activity, particle size, soil porosity and soil thickness, and indirectly related to climatic and biological conditions; (iii) to experimentally obtain the form of the constitutive law for transport by rainsplash using high-speed video and particle tracking techniques; (iv) to illustrate the fundamental significance of particle-activity gradients in producing transport, and demonstrate this using sandbox experiments for the case of rainsplash, and using field measurements of soil properties and tracer particles for the case of subsurface transport; (v) to clarify the ingredients of surface and subsurface particle dispersal, mixing and sorting, demonstrating how these processes contribute to hillslope catena structure; and (vi) to develop an advanced computational model of diffusive transport and hillslope evolution for exploring the full coupling between land-surface geometry, soil transport, soil thickness and soil production, including nonlinear responses to external and boundary forcing. This four-year program will mesh theoretical, experimental, field-based and computational components. The PIs theoretical work will focus on clarifying: (i) the ingredients of particle dispersal, mixing and sorting soil-depth and catena scale; and (ii) the forms of constitutive transport laws. PIs experimental/field work will: (i) focus on the process of rainsplash, and on particle mixing and sorting within soils, and at the soil surface; and (ii) be designed to test/validate the theoretical and computational aspects of their work. They will also apply high-performance algorithms based on discontinuous spectral element methods in developing advanced computational codes for simulating particle behavior at the soil-depth scale, and for simulating hillslope evolution at geomorphic scales. Under the auspices of the Center for Earth Surface Processes Center (CESPR), this project will involve collaboration of scientists expert in geomorphology, fluid mechanics, applied mathematics and advanced computations. The results of this work will constitute a major, and critical, contribution to the growing theoretical foundation of hillslope geomorphology.