Optimization of aeolian soil erosion control with sand fences

该项目的动机是需要一种可靠的数值工具来优化保护泥沙土壤免受风蚀的措施。风对土壤侵蚀的控制通常需要竖起不同排列的沙栏，这些栅栏可以与植被栽培结合使用，以减少风能并诱导沉积。然而，仅仅基于实验来评估它们保护大规模风沙景观的有效性是困难的，这既是因为涉及到河床演变的长期过程，也是因为土壤地形动力学强烈依赖于当地的地形和风的行为。因此，需要一个数值工具来设计保护土壤免受风蚀的优化策略，并将在本项目中开发。该数值工具将土壤和竖起的栅栏上平均湍流风场的计算流体动力学(CFD)模拟与最先进的泥沙地貌地貌动力学模拟结合在一起。为了验证模拟的有效性，在巴西东北部Jericoacara的沙丘地区进行了平均基面切应力、高度综合泥沙通量和河床剖面演变的现场测量，并将结果与数值预测进行了比较。随后，应应用数值工具来推导最佳土壤保护策略，使用不同孔隙度、间距和高度的栅栏阵列，以及在不同的风况和沙子可获得性条件下。为了调查沙栏对植被覆盖发展的影响，模拟应扩展到包括风、跃迁中的颗粒和植被之间的相互作用的模型。这对于制定改进的防治荒漠化措施和解决长期存在的沙丘固定问题十分重要。

This project is motivated by the need for a reliable numerical tool to optimize measures for protecting sediment soil from wind erosion. Control of soil erosion by wind often requires the erection of different arrays of sand fences, which may be applied in combination with vegetation cultivation to reduce wind power and induce deposition. However, evaluating their efficacy to protect large-scale aeolian landscapes based on experiments alone is difficult both due to the long-term processes involved in the bed evolution and because soil morphodynamics depends strongly on local topography and wind behavior. Therefore, a numerical tool for designing optimized strategies to protect soils against wind erosion is required and shall be developed in the present project. The numerical tool couples Computational Fluid Dynamic (CFD) modeling of the average turbulent wind field over the soil and the erected fences with state-of-the-art morphodynamic modeling of sediment landscapes. To validate the simulations, field measurements of the average basal shear stress, height-integrated sediment flux and bed profile evolution shall be performed in the dune field of Jericoacoara, Northeastern Brazil, and the results compared with numerical predictions. Subsequently, the numerical tool shall be applied to derive strategies for optimal soil protection using arrays of fences of different porosity, spacing and height, and under different wind regimes and conditions of sand availability. To investigate the effect of sand fences on the development of vegetation cover, the simulations shall be then extended to include a model for the interaction between wind, particles in saltation and vegetation. This is important to develop improved anti-desertification measures and to address the long-standing problem of dune immobilization.