This study aims at improving the XBeach model in predicting dune erosion in the presence of belowground (land-based) biomass under varying hydrodynamic conditions. In this regard, the XBeach model was extended by a literature-derived root model, which increases the critical velocity for erosion in user-defined areas due to additional root cohesion. The model was validated by using the results of a small-scale wave flume experiment as a basis, where the presence of belowground biomass reduced the measured dune erosion. Control runs considering an exclusively sand-based dune, which served as a comparison in the physical experiment, were used to setup and calibrate a one-dimensional (1D) XBeach model. Due to the application to small-scale, default parameters related to sediment transport were scaled within the scope of calibration. Results showed that the XBeach model is not capable to reproduce the observed control dune profiles satisfactorily for all hydrodynamic conditions. Subsequently, the calibrated model was applied to the physical model runs with belowground biomass. Regardless of the hydrodynamic conditions, applying the root model led to a decrease in the mean sediment concentrations and, in turn, the model-predicted erosion in the vegetated area was mainly driven by avalanching. As a result, erosion volumes were reduced in the vegetated area and a higher agreement with the measurements was achieved. At this stage, the root model is highly simplified and only validated for collision at small-scale. In this regard, the translation of the model setup to field scale would eliminate the need for parameter scaling and could result in an overall better performance of the default model. Further research should address the influence of belowground biomass on the time evolution of dune failure and avalanching.

本研究旨在改进 XBeach 模型，以预测在不同水动力条件下存在地下（陆基）生物量的沙丘侵蚀。在这方面，XBeach 模型通过文献衍生的根模型进行了扩展，由于额外的根内聚力，它增加了用户定义区域中侵蚀的临界速度。该模型通过使用小规模波浪水槽实验的结果作为基础进行验证，其中地下生物量的存在减少了测量的沙丘侵蚀。在物理实验中用作比较的完全基于沙丘的控制运行用于设置和校准一维 (1D) XBeach 模型。由于适用于小尺度，与泥沙输移相关的默认参数在校准范围内进行了缩放。结果表明，XBeach 模型无法在所有水动力条件下令人满意地再现观察到的控制沙丘剖面。随后，将校准模型应用于具有地下生物量的物理模型运行。无论水动力条件如何，应用根模型导致平均沉积物浓度降低，反过来，模型预测的植被区侵蚀主要由雪崩驱动。结果，植被区的侵蚀量减少了，并且与测量值达到了更高的一致性。在这个阶段，根模型被高度简化，并且只验证了小规模的碰撞。在这方面，将模型设置转换为现场比例将消除对参数缩放的需要，并可能导致默认模型的整体性能更好。进一步的研究应该解决地下生物量对沙丘破坏和雪崩时间演变的影响。