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上可用剪切应力的局部大气、地表和质地变量的详细知识很少。拟议的研究计划建立在我们最近从实地和实验室研究中获得的结果和经验的基础上，并将重点放在控制沉积物供应和沙尘运输的特定地表和质地因素上。这项工作的结果将为建立一个考虑沙尘排放和沙尘暴发展的时空变化的综合输沙模式的长期目标提供必要的投入。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）的剪切应力划分模型和最近的Okin和Gillette（2006）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，该模型使用具有一系列孔隙度、大小、纵横比、间距模式和地表覆盖的模拟植被元素。这项工作将在圭尔夫大学地学系进行，15m输沙隧道使用新开发的仪器，该仪器可以同时独立地测量单个植物元素和裸露中间表面的风力以及采样频率为1至10 Hz的输沙率。一项免费的实地调查也将在美国农业部新墨西哥州的Jornada试验场进行，该试验场位于以豆科植物和杂酚油灌木为主的干旱环境中。在几个有不同植被类型和覆盖面积的站点，风速的高速测量将使用传统的风速测量法在稀疏的植被冠层上方和内部进行方向测量。表面拖动和单个元素的拖动也将使用圭尔夫开发的独特仪器进行。利用电子跃变传感器测量的植被内输沙率与风流、地表剪应力分布和植被特征有关。

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.