The swash zone can firstly be identified as a part of the beach, over which the oscillating shoreline travels. This swash zone is extremely important in the natural beach morphology and the subsequent design of coastal structures. These structures and beaches are in constant interaction with the varying shoreline and while this swash zone is particularly important in coastal engineering, a relatively small amount of study has been carried out in this area. It is important to understand the process and dynamics of the swash zone to make a reasonable prediction of the effects these forces will incur on coastal structures.
For the purpose of our project topic, ‘swash overtopping a truncated plane beach’, the runup and overtopping of the steep beach will be considered to occur where the mean water level of the coastal system is below the crest of the approaching wave. This leads to the swash occurring exclusively due to incident waves. Due to the nature of the beach structure, the swash can be considered to have a relatively small height above the beach bed.
When considering the case of breaking waves, with the wave crest higher than the mean shoreline, a swash event occurs with the arrival of every new wave. This swash event travels up the beach until it returns to the shoreline or it is overtaken by the following swash event. The model, which was constructed in the laboratory, is relatively restricted in its ability to provide incident waves with sufficient periods to induce the scenario where the swash period is smaller than the wave period. This results in the majority of research to be undertaken where the initial swash event is overtaken by the following swash event.