Wave Overtopping at Seadikes

Abstract

This paper presents a summary of extensive research carried out on wave overtopping parameters over the last few years. Nevertheless, some aspects are worth mentioning for further research. Wind plays an important role for small overtopping volumes because overtopping water is transferred into spray and the loading of landward slope and the dike crests is reduced. Another important aspect is the three dimensionality of wave overtopping. This paper describes how wave overtopping has been responsible for many dike failures, dike breaches and severe flooding in the past. At first, it seems to be astonishing that dike failures are initiated on the landward slope since the incoming waves are hitting the seaward slop. Three aspects are responsible for this misinterpretation. First, wave overtopping has been often neglected for the design of seadikes because no overtopping criteria was assumed. Second, landward slopes of seadikes are often steeper and the cover (mostly clay) of the landward slope is thinner than the cover of the seaward slope. Third, the landward slope has been designed based on experience and no physically based design methods are available at present. In the future, the necessity of a well designed landward slope is increasing due to the uncertainties concerning sea level rise and the increasing frequencies and intensities of storm surges worldwide.