Scour near low-crested breakwaters: review and technical challenges

Abstract

Low-crested breakwaters are widely used structures for coastal protection, but they are vulnerable to scouring caused by wave and current action. This paper analyses information from available mobile bed physical models, the progress made in recent years on numerical modelling alongside the major limitations of the developed models and the available formulations for scour hole prediction and protection design. Physical modelling has been the primary approach for studying scour processes around low-crested breakwaters. However, existing scour depth prediction formulations have limited applicability to these structures due to their geometric characteristics. Gaps in current research include uncertainties derived from the use of scaling laws for mobile bed physical models, the effects of plunging breakers on the evolution of scour phenomena, and challenges arising from the permeability and crest freeboard of the structure and its effect on the quantification of scour phenomena. Furthermore, there is a need to investigate the impact of the slope angle, water depth, crest freeboard and wave characteristics on the scour hole evolution, as well as to optimise scour protection elements in terms of their geometric characteristics. Moreover, this review emphasises the importance of using integrated methodologies combining physical and numerical modelling with monitoring data, to comprehensively understand scour phenomena and develop mitigation measures.