Considering the Effect of Land-Based Biomass on Dune Erosion Volumes in Large-Scale Numerical Modeling

Abstract

This paper presents and validates a novel root model which accounts for the effect of belowground biomass on dune erosion volumes in XBeach, based on a small-scale wave flume experiment that was translated to a larger scale. A 1D-XBeach model was calibrated by using control runs considering a dune without vegetation. Despite calibration, a general model–data mismatch was observed in terms of overestimated erosion volumes around the waterline. Furthermore, the prediction of overwash had to be induced by increasing the maximum nearshore wave height within the XBeach simulation. Subsequently, applying the root model resulted in a good agreement with the belowground biomass cases, and the consideration of spatially varying rooting depths further improved the results. Predictions of the root model while using locally increased friction coefficients were in line with the aboveground and belowground biomass cases. However, the effect of the root model on the erosion predictions varied among the hydrodynamic conditions, so further improvements are required. Therefore, future research should focus on quantifying the effects of land-based biomass and individual plant characteristics, such as root density, on dune erodibility at large scales, along with their influences on the temporal evolution of dune scarping and avalanching.

Morphodynamic Evolution and Sustainable Development of Coastal Systems

“…Applying a novel root model in XBeach, Schweiger and Schuettrumpt [9] investigated the effect of belowground biomass on dune erosion volumes. The root model allows two modes: a constant mode with a unique rooting depth and a dynamic mode with spatial varying rooting depth.…”

“…The root model allows two modes: a constant mode with a unique rooting depth and a dynamic mode with spatial varying rooting depth. The Manning roughness coefficient in vegetated areas varied following Equation (3) [9] in order to account for spatial and temporal variability of the bed friction. The root model was validated for a large-scale experiment by upscaling a small-scale model setup (flume experiment).…”

“…Analyses of field data for morphodynamic evolution [1][2][3]; • Sustainable development for coastal protection [4,5]; • Numerical modelling of hydro-morphodynamic processes [6][7][8][9][10];…”

Dune Erosion at the German Baltic Coast—Investigation and Analysis of a Large-Scale Field Experiment Compared to Life Dunes

“…Coastal protection dunes at the Baltic Sea are usually planted (ammophila arenaria) to protect them against wind erosion and to make the sediment at least a bit more resistant to erosion during storm surges through root penetration. The increased resistance from vegetation is often considered an increased bed friction coefficient in numerical models [60,61]. In addition, the consideration of more accurate grain size distribution data in the modelling may improve the simulation quality, as discussed in [62,63].…”