Instability of Grass Caused by Wave Overtopping

This paper presents a method to deal with the instability of turf in a grass cover that could be considered as an engineering approach, in which both turbulence and two strength models (root model and turf-element model) are discussed in a heuristic way. Turbulence is discussed because of its essential role in erosion. The root model determines the shear strength of rooted soil in the vertical direction. The turf-element model based on a force balance predicts not only the instability of the grass cover but also the initiation of motion of grass. The results of the turf-element model are compared with experimental data of some prototype experiments at Dutch sea dikes.