Estimating Sediment Mass Fluxes on Surfaces Sheltered by Live Vegetation

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_τ' , provide the baseline set of data. For the bare-sand surface, the total mass flux Q shows the typical b(u_τ' - u_τ t')^3 increase with increasing skin friction velocity u_τ' , where b is a constant and u_τ t' is the threshold at the onset of particle erosion. Similar relations, however, with different values for b and u_τ t' compared to the bare-sand surface were found for experiments with 5.25 and 24.5 plants m^-2 and can be explained by the spatial variations of u_τ for the canopy cases. Based on the resulting parameters b and u_τ t' , which are found to be functions of the roughness density λ , we present a final simple relation Q(λ , u_τ') used for estimating the total mass flux for surfaces sheltered by live vegetation.