TABLE OF CONTENTS The process of wave breaking on a beach is both one of the most dramatic visually and one of the most important physically for the wave motion and for the development of the nearshore currents.
Breaking of a wave "dissipates" energy (a term defined more closely in Section 4.2) and hence causes the height of the wave to decrease. Once a wave starts breaking this process has a tendency to continue. However, the sustained breaking found in the surfzone on a beach requires a reasonably large wave height relative to the water depth to maintain the breaking. Therefore the sustained breaking of the type we see in a nearshore surfzone will always be associated with a decreasing water depth. In fact if the depth is not decreasing fast enough for the (decreasing) wave height to remain large enough relative to the water depth, the breaking will stop. In particular if a breaking wave passes over the shoreward edge of a longshore bar and into the (even slightly) deeper water in the trough behind the bar, breaking often ceases almost immediately because the wave height to water depth ratio becomes too small.
Our knowledge about the processes involved in the initiation of and the sustained wave breaking is still far from complete. Therefore experimental results play an important role in the clarification of these processes. In this chapter we will outline the present state of knowledge and seek to systematize the insight we can gain using a combination of...
