This study was undertaken to establish the most reliable breaker depth index formula that will yield satisfactory predictions for a wide range of hydraulic and beach conditions. The applicability of six existing formulas for computing the breaker depth index was examined with the use of a large amount of published laboratory data (524 cases collected from 22 sources). The behavior of these formulas was studied with respect to the main governing parameters, which are the beach slope and the deep-water wave steepness. It was found that most formulas show quite good predictions for cases including gentle slopes (0.01 < m ≤ 0.07). However, the predictions are typically not satisfactory for breaking waves on steep slopes (m > 0.1), and the formulas do not always present a physically correct behavior with respect to the two main parameters. A new formula is proposed to predict the breaker depth index with the best possible accuracy. Also, a discussion is included on the application of the formula to random waves and on the relationship between the breaker depth index and the Irribaren number to distinguish between different breaker types.

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