High Wave Grouping in Shallow Water

Abstract

Characteristics of groups of high ocean waves are studied in varying water depths using field measurements and laboratory simulations. Field data were collected from a shore‐perpendicular line of gages at the Coastal Engineering Research Center Field Research Facility during one storm with onshore winds. Laboratory data were obtained over a plane 1:30 slope by generating the energy spectrum measured offshore in the field. Parameters indicative of wave grouping are observed to vary little outside the surf zone, but decrease greatly after wave breaking occurs. Field and laboratory parameters are generally consistent although some laboratory parameters sensitive to details in the record appear to be distorted by standing wave oscillations in the flume. In particular, the modulation period or time lag between successive groups and the length of the group containing the highest wave in the record are distorted in the laboratory.