Wave Overtopping of Coastal Structures. Physical Model versus Desktop Predictions

Wave overtopping of coastal structures represents a potential hazard for people, property and infrastructure within the vicinity of wave impact areas. Depending on the acceptable risk and required degree of certainty related to wave overtopping, coastal engineers rely on predictions from semi-empirical desktop methods or physical model studies. This paper reports and compares two-dimensional physical model testing of both vertical seawall and sloping rubble structures with overtopping predictions made using best practice desktop techniques. The structures investigated, relating to the development of several LNG (liquefied natural gas) facilities in Australia, are being constructed in locations where the wave climate is dominated by recurrent cyclonic events. The singularity of the wave climate, extreme wave heights and water levels, coupled with the high economic value of the infrastructure and operations to be protected, has led to the requirement of this in depth physical model and desktop investigation of wave overtopping. Desktop predictions were generally found to be consistent with overtopping measurements from physical model testing in terms of order of magnitude and they proved to be a useful tool for preliminary engineering design. However, physical model tests remain the most reliable methods to characterize overtopping processes, in particular in such cases as coastal structures defending sensitive infrastructure and property or when public safety is a concern.