THE EFFECTS OF VEGETATION AND SOIL TYPE ON STREAMBANK EROSION, SOUTHWESTERN VIRGINIA, USA¹

Abstract

The goal of this research was to evaluate the relative effects of root density, freeze/thaw cycling, and soil properties on the erodibility and critical shear stress of streambanks. The erodibility and critical shear stress of rooted bank soils were measured in situ at 25 field sites using a submerged jet test device; several soil, vegetation, and stream chemistry characteristics shown to influence soil erosion were also assessed. Multiple linear regression analysis was conducted to determine those factors that most influenced streambank erodibility and the relative impact of riparian vegetation. Study results indicated that soil erosion is a complex phenomenon that depends primarily on soil bulk density. Freeze/thaw cycling, soil antecedent moisture content, the density of roots with diameters of 2 to 20 mm, soil texture, and the interaction of soil pore water and stream water had a significant impact on soil erodibility and critical shear stress, depending on soil type. Riparian vegetation had multiple significant effects on soil erodibility. In addition to reducing soil erodibility through root reinforcement, the streamside vegetation affected soil moisture and altered the local microclimate, which in turn affected freeze/thaw cycling (FTC). This study represents the first in situ testing of the erodibility of vegetated streambanks and provides a quantitative analysis on the effects of vegetation on streambank erosion, relative to other soil physical and chemical parameters.

Linking fine root and understory vegetation to channel erosion in forested hillslopes of southwestern China

“…Gyssels et al (2005) showed that while dense root systems produced by a mix of small trees, shrubs, and grasses were important in maintaining slope stability, shallow dense root networks produced by grasses appear to be more effective in protecting soils from water erosion by concentrated flow. It is also the case that fine and small roots (0.5-2.0 mm in diameter) at deeper soils (root depth>30 cm) with high tensile strength, especially for tree species, are more efficient in supporting stream bank stability (Davidson et al 1989;Wynn et al 2004;Wynn and Mostaghimi 2006). The grasses and shrubs are optimum cover types for slope stabilization largely due to their large numbers of small, strong roots (Li.…”

Numerical simulation of hydrodynamics and bank erosion in a river bend

“…For example, progress in quantifying fluvial erosion (i.e., the removal of bank material by the action of hydraulic forces) has included the development and application of specific techniques for measuring in situ the erodibility parameters of the bank sediments [Tolhurst et al, 1999;Hanson and Simon, 2001;Wynn and Mostaghimi, 2006;Clark and Wynn, 2007], as well as methods to model the near-bank flow field using computational fluid dynamics (CFD) and other techniques [Darby et al, 2004;Smith, 2006a, 2006b;McBride et al, 2007;Julian and Torres, 2006;Papanicolaou et al, 2007]. With respect to mass failure, recent studies have focused on two main topics:…”

Watershed Variability in Streambank Erodibility and Implications for Erosion Prediction

“…As suggested by previous research [13,29,[48][49][50], variability observed in erodibility parameters can be attributed to soil heterogeneity and subaerial processes. When compared to other studies [13,29,[48][49][50], less variability in erodibility parameters was observed along FC-FM and FC-WC.…”