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_{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.