Permeable, fence-like coastal structures are increasingly deployed in coastal engineering applications for wave attenuation and shoreline stabilization. Despite their growing importance—particularly in the context of nature-based solutions and the restoration of coastal ecosystems such as seagrass meadows—the hydrodynamic loading acting on quasi-two-dimensional permeable structures remains limited.
Methodology
The study is based on prototype-scale wave flume experiments conducted at the Ludwig-Franzius-Institute. Fully submerged willow fences with varying permeabilities were exposed to regular waves under water depths ranging from shallow to transitional conditions. Drag and inertia coefficients (CD und CM) were determined using a weighted least squares (WLS) approach within the framework of the Morison equation.
Results
The results demonstrate a strongly drag-dominated hydrodynamic response across all tested configurations (), with inertia contributions becoming negligible for permeable structures. The drag coefficient is shown to depend on both the Reynolds number and the permeability . Based on regression analysis, a novel empirical model is proposed that expresses the drag coefficient as a function of these two parameters. The findings offer a practical engineering tool for the rapid estimation of wave-induced forces on fully submerged, quasi-two-dimensional coastal structures such as groynes and willow or bamboo fences.
Publication
Kamperdicks, L., Kerpen, N., Wynants, M., Bischoff, C., Schlurmann, T., & Paul, M. (2026). Wave-induced forces on submerged permeable fence-like structures: prototype-scale experiments and empirical model. Applied Ocean Research, 174, 105193. https://doi.org/10.1016/j.apor.2026.105193
