New developments in assessment of wave overtopping on single-layer cube armoured breakwaters based on laboratory experiments

Abstract Wave overtopping is a critical aspect to take into consideration when designing a coastal structure. An adequate crest geometry (a combination of height and width) is required to maintain the required acceptable safety levels for the population and infrastructure behind the structure. This paper presents the wave overtopping results of laboratory experiments for single-layer cube (SLC) armoured breakwaters with a regular placement pattern. The experiments considered different incident wave conditions and two armour layer porosities, 29% and 33%. Mean wave overtopping discharges obtained were generally higher than the ones observed in previous experiments for the same armour configuration. Available methods shown some limitations in predicting the measured overtopping discharges suggesting the relevance of other factors. It is observed that, by including the ratio of wavelength to the armour crest width in an alternative overtopping formula, the mean flow rate predictions are improved. It was also found that mean overtopping discharges increase by 16-42% due to a decrease in armour porosity with negligible differences in reflection coefficients. A different initial seed number in the wave generation series can lead to differences in wave overtopping discharges up to a factor of two. This work aims to contribute to the knowledge of wave overtopping in SLC armoured breakwaters considering the limited available information for this type of armour configuration.