Aeolian shear stress ratio measurements within mesquite-dominated landscapes of the Chihuahuan Desert, New Mexico, USA

Abstract

A field study was conducted to ascertain the amount of protection that mesquite-dominated communities provide to the surface from wind erosion. The dynamics of the locally accelerated evolution of a mesquite/coppice dune landscape and the undetermined spatial dependence of potential erosion by wind from a shear stress partition model were investigated. Sediment transport and dust emission processes are governed by the amount of protection that can be provided by roughness elements. Although shear stress partition models exist that can describe this, their accuracy has only been tested against a limited dataset because instrumentation has previously been unable to provide the necessary measurements. This study combines the use of meteorological towers and surface shear stress measurements with Irwin sensors to measure the partition of shear stress in situ. The surface shear stress within preferentially aligned vegetation (within coppice dune development) exhibited highly skewed distributions, while a more homogenous surface stress was recorded at a site with less developed coppice dunes. Above the vegetation, the logarithmic velocity profile deduced roughness length (based on 10-min averages) exhibited a distinct correlation with compass direction for the site with vegetation preferentially aligned, while the site with more homogenously distributed vegetation showed very little variation in the roughness length. This distribution in roughness length within an area, defines a distribution of a resolved shear stress partitioning model based on these measurements, ultimately providing potential closure to a previously uncorrelated model parameter.

Vegetation in Drylands: Effects on Wind Flow and Aeolian Sediment Transport

“…Dupont et al [52] coupled a LES model with a physically based saltation model to resolve turbulent wind flow over heterogeneous vegetated landscapes composed of trees and shrubs. The erosion patterns simulated by Dupont et al's [52] model were qualitatively consistent with previous wind tunnel [59,78] and field [46,140] observations. Minimal dune models (e.g., [168,169]), which combine analytical descriptions of turbulent wind velocity with continuum saltation models, have also been used to successfully simulate transitions between barchan and parabolic dunes [169,170].…”

“…During the 1990s, more attention was given to the development of drag partitioning techniques that could establish the wind momentum flux at the soil surface in the presence of roughness elements. The schemes of Raupach [57,121] and Marticorena and Bergametti [118] were widely adopted on the basis of their good agreement with wind tunnel experiments using solid objects on non-complex surfaces (e.g., [51,71,[140][141][142][143]). However, the drag partition schemes have also been found to be limited in application in several respects.…”

Spatio-Temporal Surface Shear-Stress Variability in Live Plant Canopies and Cube Arrays

“…Brown et al (2008) found no significant effect of different spatial arrangements of non-erodible roughness elements on the drag partition. (ii) Field experiments with no control over the wind conditions (Musick and Gillette 1990;Wolfe and Nickling 1996;Wyatt and Nickling 1997;Lancaster and Baas 1998;King et al 2006;Gillies et al 2007). In field experiments it is difficult to decouple the influences of the plants on surface shear stress from those induced by the variations in the wind.…”

“…Gillies et al (2007) found that the Raupach (1992) drag partition model performed very well for regular arrays of solid elements of different roughness densities within a large open area. (iii) Spatial and temporal averages: only limited data are available on local peak shearstress values (Crawley and Nickling 2003;King et al 2006;Brown et al 2008) or temporal variations of surface shear stress (Sutton and McKenna-Neumann 2008). Sutton and McKenna-Neumann (2008) examined bed level flow patterns around solid cylinders for varying roughness densities and correlated vortices shed by the obstacles with their erosive capability.…”

A tribute to Michael R. Raupach for contributions to aeolian fluid dynamics

“…The method used in Raupach (1992 19 20 To test the theory of Raupach (1992) The simplicity of Eq. (7) is a strength for its application, in that it requires only a few measurable 2 parameters (Wolfe and Nickling, 1996; Lancaster and Baas, 1998; King et al, 2006). This 3 approach is widely used today in wind erosion models.…”