Analysis of the mechanics of breaker bar generation in cross-shore beach profiles based on numerical modelling

In this work, a recently developed numerical model, capable of solving the hydro- and morphodynamics of the cross-shore beach profile, is used to gain insight into the relevant processes driving the generation of a breaker bar. The bedload and suspended sediment transport contributions are analysed separately. It has been shown that the bedload transport tends to accumulate sediment on the onshore side of the undertow detachment point, at a distance that depends on the skewness of the waves and the magnitude of the friction velocity, shaping the onshore face of the breaker bar. In contrast, the suspended transport contributes to the growth of the offshore side of the breaker bar. Besides, a comparison between the sediment transport rates produced by different types of breakers shows a faster bathymetric evolution and an offshore displacement of the position of the breaker bar for high Iribarren numbers. Differences are consistent with the proposed mechanisms driving the evolution of the beach profile. The findings of this work provide a better understanding of the processes driving the formation of breaker bars, how they interact with each other and the relative importance of bedload and suspended sediment transport at each location of the cross-shore profile.

Automated summary

In this study, a numerical model is used to analyze the hydro- and morphodynamics of a cross-shore beach profile and understand the processes driving the formation of breaker bars. The separate contributions of bedload and suspended sediment transport are examined. The results show that bedload transport accumulates sediment on the onshore side, shaping the breaker bar, while suspended transport contributes to the growth of the offshore side. Additionally, comparisons between different types of breakers reveal differences in bathymetric evolution and the position of the breaker bar.