A New Approach to Account for Species-Specific Sand Capture by Plants in an Aeolian Sediment Transport and Coastal Dune Building Model

Abstract

Vegetation plays a crucial role in coastal dune building. Species-specific plant characteristics can modulate sediment transport and dune shape, but this factor is absent in most dune building numerical models. Here, we develop a new approach to implement species-specific vegetation characteristics into a process-based aeolian sediment transport model. Using a three-step approach, we incorporated the morphological differences of three dune grass species dominant in the US Pacific Northwest coast (European beachgrass Ammophila arenaria, American beachgrass A. breviligulata, and American dune grass Leymus mollis) into the model AeoLiS. First, we projected the tiller frontal area of each grass species onto a high resolution grid and then re-scaled the grid to account for the associated vegetation cover for each species. Next, we calibrated the bed shear stress in the numerical model to replicate the actual sand capture efficiency of each species, as measured in a previously published wind tunnel experiment. Simulations were then performed to model sand bedform development within the grass canopies with the same shoot densities for all species and with more realistic average field densities. The species-specific model shows a significant improvement over the standard model by (a) accurately simulating the sand capture efficiency from the wind tunnel experiment for the grass species and (b) simulating bedform morphology representative of each species' characteristic bedform morphology using realistic field vegetation density. This novel approach to dune modeling will improve spatial and temporal predictions of dune morphologic development and coastal vulnerability under local vegetation conditions and variations in sand delivery.