The thesis deals with the wave breaking process of waves propagating over a steep submerged bottom slope. The amount of energy dissipated in the wave breaking process is focused upon. An extensive number of experimental tests (>400) using regular and irregular waves breaking over a simulated reef in the hydraulic laboratory are performed. Based on the experimental tests several formulae developed. Formulae  are capable of predicting the transmitted wave height and wave energy flux, respectively. Futhermore, a numerical wave model based on the extended Mild-Slope equation has been developed. The model is capable of generating progressive irregular waves. Wave breaking has been included using a modification of the Battjes and Janssen [1978] periodic bore approach. The results from this study be applicable in the design of coastal structures as submerged breakwaters or artificial reefs.