Influence of spatial vegetation structures on current- and wave-induced erosion processes on dunes (VesweED)

• Applicants: Professor Dr.-Ing. Nils Goseberg; Professor Dr.-Ing. Holger Schüttrumpf
• Subject Area: Geotechnics, Hydraulic Engineering
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 541400249

Due to the increasing intensity and frequency of hydrodynamic extreme events, the stress on sandy coasts will increase in the course of climate change. In the context of sustainable coastal protection, nature-based solutions such as the use of dunes are in focus. Here, an increasing spread of vegetation has been observed in recent years, which often characterizes the appearance of dunes in the form of vegetated (patches) next to unvegetated areas. Against the background of an intensification of the hydrodynamic load, a detailed understanding of how the hydro- and morphodynamic processes at the dune are influenced by existing vegetation structures is therefore necessary. In recent years, various physical model tests have already been carried out in this regard, and an increased erosion resistance of the dune due to existing above- and belowground vegetation structures was found. However, a systematic investigation of the influence of individual plant parameters and, in particular, of vegetation patches on the erosion processes at dunes and the temporal evolution of dune failure under hydrodynamic loading has not yet been carried out. The aim of this project is to improve the understanding of the interaction between vegetation and dunes under hydrodynamic loading (wave and current). In particular, general relationships regarding the influence of individual vegetation parameters (rooting depth, patchiness) on erosion resistance and dune failure under stationary flow and non-stationary wave loading are to be derived. For this purpose, a geometrically and dynamically scaled surrogate vegetation model will first be developed, which will allow accurate process mapping in the experimental work while eliminating challenges due to the use of live vegetation. Experiments on overflow (at IWW) and wave impact (at LWI) with systematic variation of vegetation parameters will be conducted in a complementary manner as part of the experimental work. The use of the same measurement techniques and a uniform model setup ensure the comparability of the results. This also incorporates the assessment and modelling of dune related properties such as geometry, sedimentological grading and bulk density, in turn acquired through suitable geotechnical field sampling equipment. These in turn serve as a basis for the setup of numerical models which are used to investigate a large number of additional parameter variations within the framework of a supplementary numerical parameter study. The final step is a synthesis of the experimental and numerical results to a correlation model for the description of the dune failure and the erosion processes in dependence of the vegetation properties as well as a basic process understanding of the erosion behavior of vegetated and unvegetated dunes and the effect of dune vegetation.

• DFG Programme: Research Grants