This chapter is about stability of individual stones or armour elements on a sloping surface under wave attack. Due to the complex water movement of waves breaking on a slope, it is not yet possible to derive a satisfactory theoretical expression for the forces and the stability of such elements. This means that this chapter contains a multitude of empirical formulae, all based on the results of small-scale experiments. Although it would not be wise to learn all these formulae by hearth, it is necessary to understand them and their significance to the designer of the breakwater.

For this lecture you need to read Breakwaters and Closure Dams, Chapter 7