Estimating Sediment Mass Fluxes on Surfaces Sheltered by Live Vegetation

Abstract

We present a simple model based on already existing and widely used equations for estimating particle mass fluxes on surfaces sheltered by live vegetation. Wind-tunnel measurements of vertical profiles of mass flux in three different dense live plant canopies, and as a function of the spatially averaged skin friction velocity $${u_{\tau }}'$$ , provide the baseline set of data. For the bare-sand surface, the total mass flux Q shows the typical $$b({u_\tau }' - {u_{\tau t}}')^{3 }$$ increase with increasing skin friction velocity $${u_{\tau }}'$$ , where b is a constant and $${u_{\tau t}}'$$ is the threshold at the onset of particle erosion. Similar relations, however, with different values for b and $${u_{\tau t}}'$$ compared to the bare-sand surface were found for experiments with 5.25 and 24.5 plants $$\hbox {m}^{-2}$$ and can be explained by the spatial variations of $$u_{\tau }$$ for the canopy cases. Based on the resulting parameters b and $${u_{\tau t}}'$$ , which are found to be functions of the roughness density $$\lambda $$ , we present a final simple relation $$Q(\lambda ,\, {u_{\tau }}')$$ used for estimating the total mass flux for surfaces sheltered by live vegetation.