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

点击翻译按钮获取中文摘要

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.