Sediment entrainment and transport in sparsley vegetated arid and semi arid environments

尽管最近在风蚀研究方面取得了进展，但目前关于直接控制沉积物供应和床面剪切应力的局部大气、表层和纹理变量的详细知识很少。拟议的研究计划建立在我们最近的实地和实验室研究的结果和经验的基础上，将重点放在控制沉积物供应和沙尘运输的特定表面和纹理因素上。这项工作的结果将为长期目标提供必要的投入，即开发一个综合性的沉积物输运模型，说明沙尘排放和沙尘暴发展的时间和空间变异性。拟议的研究计划有两个不同但相互关联的组成部分。我们将首先对Raupach等人（1993年）的剪应力分配模型和最近的Okin和Gillette（2006年）的非平衡侧向覆盖模型进行详细的现场和实验室风洞评估，使用具有一系列孔隙度、大小、长宽比、间距模式和表面覆盖的模拟植被元素。这项工作将在圭尔夫大学地理系进行，采用新开发的仪器，可以同时和独立地测量风力对个别植物元素和裸露的干预表面，以及沉积物的迁移率，采样频率为1至10赫兹。还将在新墨西哥州的美国农业部Jornada实验靶场进行一次免费的实地调查，该试验场位于以牧豆树和杂酚油灌木丛为主的干旱环境中。在几个地点，具有不同的植被类型和覆盖率，将使用传统的风速测量法在稀疏植被冠层上方和内部进行风速和风向的高速测量。还将使用在圭尔夫开发的独特仪器进行表面阻力和单个元件上的阻力。由电子跃移传感器测量的植被内的泥沙输运速率将与风流动、表面剪切应力分布和植被特性相关。

Despite recent advances in wind erosion research, little detailed knowledge is currently available regarding the localized atmospheric, surficial and textural variables that directly control both sediment supply and available shear stress at the bed. The proposed research program builds on the results and experience gained from our recent field and laboratory studies and will focus on specific surficial and textural factors that control the sediment supply and transport of sand and dust. Results of this work will provide necessary input for the long-term goal of developing a comprehensive sediment transport model accounting for the temporal and spatial variability of dust emissions and dust storm development. The proposed research program has two distinct but interrelated components. We will first carry out a detailed field and laboratory wind tunnel evaluations of the Raupach et al. (1993) shear stress partitioning model and the more recent Okin and Gillette (2006) non-equilibrium lateral cover model using simulated vegetation elements having a range of porosities, sizes, aspect ratios, spacing patterns and surface cover. This work will be undertaken in the Department of Geography, University of Guelph 15m sediment transport tunnel using newly developed instrumentation that can simultaneously and independently measure the wind force on individual plant elements and the bare intervening surface as well as the sediment transport rate at sampling frequencies from 1 to 10 Hz. A complimentary field investigation will also be carried out at the USDA Jornada Experimental Range, New Mexico, which is located in an arid environment dominated by mesquite and creosote shrubland. At several sites, having different vegetation types and per cent cover high speed measurements of wind speed, direction will be made above and within the sparse vegetation canopies using traditional anemometry. Surface drag and drag on individual elements will also be made using unique instrumentation developed at Guelph. Sediment transport rates measured within the vegetation by electronic saltation sensors will be related to the wind flow, surface shear stress distribution and vegetation characteristics.