This thesis focuses on the erosion of the grass sod during overtopping wave volumes. Several tests have been performed in the last few years with the wave overtopping simulator. During this thesis, some of these locations have been tested for the strength of the grass sod with a newly developed method. This new method, called the sod pulling method, tests the actual strength of the grass by lifting the grass sod out of the top layer. The measured forces needed to lift the grass sod can be rewritten into critical grass normal stresses. Furthermore, the displacement is measured as a function of the measured force.@en