On the influence of wave breaking on the height limits of two-dimensional wave groups propagating in uniform intermediate depth water

The present study provides more robust and universal characterisation of breaking in transitional water than previously determined by geometric wave observations. Using the same measurement techniques as those of Saket et al. (2017), we have investigated the breaking threshold proposed by Barthelemy et al. (2018) but for different classes of unforced unidirectional wave groups in intermediate water depths. The threshold parameter Bx =Us/C (where Us is the horizontal surface water particle velocity at the wave crest and C is the wave crest point speed) which distinguishes breaking from non-breaking waves was found to be 0.835 ± 0.005 with the experimental uncertainty of each data point of ±0.020. This threshold is applicable to water depth to wavelength ratios as low as 0.2 including the deep water conditions investigated by Saket et al. (2017). No dependence on peak spectral wavenumber was found.