Parameterization of nearshore wave breaker index

The performances of phase-averaged parametric nearshore wave transformation models depend significantly on a reliable estimate the breaker index γ (the height-to-depth ratio), free model parameter that essentially controls amount breaking energy dissipation. While previous studies have suggested separate relationships between and offshore steepness (s0) or normalized local water depth (kh), parameterization still requires further investigation considering wider variety conditions sounder physical basis. In this study, we use field datasets height inverse modelling approach to reveal composite dependence both s0 kh. Specifically, results show positive kh for larger s0, negative smaller s0. Based such relationships, new formula is proposed, its performance verified against available in three coasts 14 laboratory tests. Implementation leads error reduction prediction by 10–24% (mean = 19%) relative seven widely used literatures. particular, remarkably higher accuracy obtained under with small steepness, which important studying onshore sediment transport beach recovery. Two counteractive mechanisms nonlinearity effects, namely intensification mechanism resistance mechanism, are explain opposite γ-kh within different ranges