Sediment Transport by Overland Flow on Irregular Hillslope Surfaces

土壤侵蚀模型已成为土壤保持规划和设计以及各种其他土地管理和评估任务的重要工具。现代土壤侵蚀模型是基于过程的，几乎所有模型都包含预测输沙能力的公式，因为输沙能力既控制侵蚀速率，也控制沉积速率。虽然所有的山坡表面都是不规则的，但目前还没有一个公式能够准确地预测这些表面上的地表水流的输送能力。现在迫切需要制定这样一个公式。该项目将开发石头覆盖和草覆盖表面的沉积物运输公式，作为开发所有不规则表面更通用公式的第一步。这项研究将以实验室的两套水槽实验为基础。圆柱体将用来模拟石头，钉子将用来模拟草。实验将在一个6米长的水槽中进行，使用各种水流、梯度、颗粒大小、圆柱体和钉浓度。分析将建立输送能力与适当的水力变量之间的经验关系，这些变量反映了床附近耗散的能量和可用于输送沉积物的能量。基于过程的土壤侵蚀模型提供准确的土壤侵蚀预测的能力取决于它们所采用的输送能力方程的准确性。这项研究将产生适用于石头和草覆盖表面的公式，这些公式可以立即纳入现有的土壤侵蚀模型中。使用这些公式可以更准确地估计泥沙输送能力，从而更好地预测不规则地表上的土壤侵蚀速率。

Soil erosion models have become an essential tool for soil conservation planning and design and for a variety of other land management and assessment tasks. Modern soil erosion models are process based, and virtually all of them contain a formula for predicting sediment transport capacity, as transport capacity controls both rate of erosion and rate of deposition. Although all hillslopes have irregular surfaces, no existing formula is capable of accurately predicting the transport capacity of overland flow on such surfaces. There is an urgent need for development of such a formula. This project will develop sediment transport formulas for stone covered and grass covered surfaces as a first step toward development of a more general formula for all irregular surfaces. The research will be based on two sets of flume experiments in the laboratory. Cylinders will be used to simulate stones and nails will simulate grass. Experiments will be performed in a six meter long flume using a variety of water discharges, gradients, grain sizes, and cylinder and nail concentrations. The analysis will establish empirical relations between transport capacity and appropriate hydraulic variables that reflect the energy dissipated near the bed and available to transport sediment. The ability of process-based soil erosion models to provide accurate predictions of soil erosion is dependent on the accuracy of the transport capacity equation they employ. This research should produce formulas for stone and grass covered surfaces which can be incorporated immediately into existing soil erosion models. Use of these formulas should lead to more accurate estimates of sediment transport capacity and thus better predictions of soil erosion rates on irregular surfaces.