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

相位平均参数近岸波浪变换模型的性能在很大程度上取决于对波浪破碎机指数γ（破碎机高深比）的可靠估计，这是一个基本上控制破碎能量耗散量的自由模型参数。虽然之前的研究已经提出γ与近海波陡 ( s ₀ ) 或归一化局部水深 ( kh )之间的单独关系，但考虑到更广泛的条件和更可靠的物理基础，γ的参数化仍需要进一步研究。在这项研究中，我们使用波高的现场数据集和逆向建模方法来揭示复合依赖s ₀和kh上的γ。具体而言，结果显示对于较大的s ₀ γ对kh的正相关性，以及对于较小的s ₀ γ对kh的负相关性。基于这样的复合关系，一个新的γ提出了公式，并在三个海岸和14个实验室测试的可用波高数据集上验证了其性能。相对于文献中广泛使用的七种模型，在参数波模型中实施这个新公式可以将波高预测的误差降低 10-24%（平均值 = 19%）。特别是在海上波陡较小的波浪条件下获得了显着更高的模型精度，这对于研究陆上泥沙输送和海滩恢复具有重要意义。提出了波非线性效应的两种反作用物理机制，即破断增强机制和破断阻力机制来解释不同s范围内相反的γ - kh关系。₀ .