Wave slopes and breaking distributions in the surf zone

Abstract

Field measurements from a cross-shore array of nine pressure sensors, spanning the surf zone, are used to examine the evolution of ensemble averaged wave face slopes of ocean waves as they propagate through the breaking region. Averaged wave slopes are determined from time series of the measured sea surface elevation and from an averaged waveform calculated from bispectral coefficients, and compared with predictions from a wave transformation model that includes wave breaking described by rollers. Measured percent wave breaking are used to examine the evolution of third moment and bispectral statistics in relation to breaking patterns. Shoaling waves gradually transform from peaked, Stokes-like waves to forward pitched asymmetric waves just prior to breaking. Inside the surf zone, wave asymmetry is modified by the breaking distributions and the effects of bottom topography. The observations suggest a relationship between the cross-shore wave breaking distributions and wave slopes. Wave slopes predicted using a calibrated wave transformation model which includes wave rollers are in qualitative agreement with measured wave slopes.