A predictive approach to elucidate the interaction between wave-induced flows and vegetation

• Applicants: Professor Dr.-Ing. Markus Böl; Dr.-Ing. David Schürenkamp
• Subject Area: Geotechnics, Hydraulic Engineering
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 500319808

A major impact of anthropogenic changes to our climate is the accelerated rise in sea level. This rise is expected to alter the propagation velocity and kinetic energy carried by near-surface waves, challenging the effectiveness of natural coastal vegetation in preventing erosion and mitigating flood risk. In this project, we aim to take a step towards a predictive approach to quantifying kinetic energy dissipation and wave modulation by salt marsh vegetation. We do this by integrating plant-scale properties into a spatially resolved unit section of free surface flow through and over vegetation.Two main goals are to be achieved within the framework of this project: The first objective is to develop a numerical salt marsh model for Elymus that is able to describe the flow-vegetation interaction at the plant scale. This salt marsh model, whose plant modelling is based on the Kirchhoff-Love theory, is supported by corresponding mechanical/histological experiments at the culm and leaf scale, as well as by canonical data sets of high-resolution flow and pressure fields based on time-resolved tomographic PIV and force measurements on individual plants. On the one hand, this model can serve as a cost-effective and transferable tool for analysing the influence of mechanical and geometric or architectural properties of vegetation on wave attenuation. Currently, observations on this dependence are far from consistent and the relative roles played by plant bending stiffness, buoyancy and culm/leaf density are still controversial. On the other hand, the salt marsh model provides a springboard for a physical description on even larger scales. With these numerical tools and the corresponding experimental results, replacement systems for individual plants and complete plant communities will be created by means of three-dimensional additive manufacturing and experimentally sampled in the wave channel. The salt marsh section of Elymus replacement plants generated in this way represents the second main objective of this project. With this replacement system it is possible to do without costly sampling of real plant communities, which is especially important in national parks to test the interaction behaviour between salt marsh vegetation in the wave channel. Furthermore, almost any number of systematic experiments under different conditions and repetitions can be realised in the salt marsh vegetation.

• DFG Programme: Research Grants