Full-scale laboratory study on distribution of individual wave overtopping volumes over a levee under negative freeboard

• The full-scale flume tests in the combined wave and surge overtopping are done.
• The distribution of wave overtopping volume and instantaneous overtopping discharge under negative freeboard are obtained.
• The wave overtopping patterns under negative freeboard can be divided into two categories.
• The empirical equations for Weibull factors are developed in two different ranges of relative freeboard.
• The new equation gives better estimates of Weibull factors for the low discharge condition.

Wave overtopping parameters are key parameters in the design of levees and the management of coastal protection. This paper presents the distribution of wave overtopping volume and instantaneous overtopping discharge under negative freeboard. The analysis and discussions are based on the results of full-scale flume tests for a levee section in the combined wave and surge overtopping. Four wave overtopping patterns under negative freeboard were observed. Weibull distribution was used to represent the distribution of individual overtopping volumes and the distribution of instantaneous overtopping discharge. Based on the hydraulic characteristics of wave overtopping under negative freeboard, empirical equations for Weibull factors were developed in the two different ranges of relative freeboard. The new equation gives better estimates of Weibull factors for the low discharge condition.