This dataset provides raw and processed data generated in the experimental campaign: “Wave dissipation and transformation over coastal vegetation under extreme hydrodynamic loading”. The experiments were performed in the Large Wave Flume (Grosser Wellenkanal, GWK) of Forschungszentrum Küste (FZK) in Hannover, Germany. The objectives of the experiments were Quantify the role of vegetation on wave attenuation under extreme conditions that are essential for flood defence designs; Identify water depth / wave height / wave steepness thresholds that mark the transition from (a) conditions in which vegetation has a negligible effect on wave energy to (b) those regimes where vegetation significantly affects waves, to (c) those conditions that cause bed/canopy/plant ‘failure’/’breakage’; Quantify the forces and response of two species types (Elymus and Puccinellia), at the front of the vegetated section to the various depth/energy regimes; Quantify the effect of a non-vegetated marsh platform on waves, for comparison with the effects of the vegetated platform (control condition). Observations and measurements were based on a submerged vegetated platform of approximately one wave length (40 m) subjected to irregular waves of different characteristics. The tested vegetation was made up of typical north-western European species-rich middle to high elevation marsh communities. The data acquisition covered The wave characteristics in front of, over, and behind the platform; Current velocity profiles above the vegetation; Point flow velocities; Plant stem density; Soil surface profiles; Net floating organic debris, and Forces exerted on real and artificial plants mounted in front of the test platform. In addition to measurements, the plant movements and the whole experimental area were video recorded. Due to their very large sizes, video recordings cannot be placed to this repository. This data and the data from number 4 to 6 of the list above may be provided on demand. Please contact the manager of the FZK laboratory. More information about the experiments may be found in the auxiliary files (see the readme.txt file) provided here, and associated publications as follows: Möller, I., Kudella, M., Rupprecht, F., Spencer, T., Paul, M., Wesenbeeck, B.K. van, Wolters, G., Jensen, K., Bouma, T.J., Miranda-Lange, M., Schimmels, S., 2014. Wave attenuation over coastal salt marshes under storm surge conditions. Nature Geoscience 7, ngeo2251. https://doi.org/10.1038/ngeo2251 Rupprecht, F., Möller, I., Paul, M., Kudella, M., Spencer, T., van Wesenbeeck, B.K., Wolters, G., Jensen, K., Bouma, T.J., Miranda-Lange, M., Schimmels, S., 2017. Vegetation-wave interactions in salt marshes under storm surge conditions. Ecological Engineering 100, 301–315. https://doi.org/10.1016/j.ecoleng.2016.12.030 Spencer, T., Möller, I., Rupprecht, F., Bouma, T.J., van Wesenbeeck, B.K., Kudella, M., Paul, M., Jensen, K., Wolters, G., Miranda-Lange, M., Schimmels, S., 2016. Salt marsh surface survives true-to-scale simulated storm surges. Earth Surf. Process. Landforms 41, 543–552. https://doi.org/10.1002/esp.3867