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.
Highlights
Coastal dunes are distributed worldwide and acknowledged for their wide range of functions, including their contributions to coastal defense, ecological diversity and socioeconomic services, such as recreation and tourism [1,2]
In order to increase the effect of the root model, com16 of 21 bining rcc = 0.5 with a local friction value of nveg = 0.08 s/m1/3 resulted in good agreement with respect to dune profile differences (d) and increased the percentage decrease in overwash volume to 70.4%
While for DO, the root model resulted in good agreement with the upscaled belowground biomass (BGB)
Summary
Coastal dunes are distributed worldwide and acknowledged for their wide range of functions, including their contributions to coastal defense, ecological diversity and socioeconomic services, such as recreation and tourism [1,2]. Concerning coastal protection, dunes serve as a natural barrier at the boundary between land and sea. They have been recommended as one example of a more sustainable, cost-effective and ecologically sound coastal protection measure than conventional hard structures [3,4,5]. In this regard, dune vegetation was found to have an especially beneficial effect on the resilience of dunes against storm-induced erosion [6,7,8,9,10]. The basic idea is to locally increase the critical velocity for erosion due to additional root cohesion until the cumulative erosion exceeds a user-defined constant rooting depth
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