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Records of deepwater sea surface elevation alone, even when taken at high sampling rates, do not allow determination of those waves in the record that are breaking. Although visual observations of steep random waves clearly show even the beginning of a breaking event, the white capping and collapse of the front face of a breaking wave do not appear in any meaningful way in the recorded output of an elevation gauge. Considerable research has been devoted to finding a method of detecting breaking events in a wave elevation record. Some criteria have been advanced, but most of the models show little skill. The present study evaluates the power of the Phase-Time Method based on the Hilbert transform, in detecting breaking waves in large-scale laboratory experiments under a variety of deep water wave conditions. A limited validation of the method in the field was performed. A useful model of deepwater breaking wave detection is developed, and its limits are stated. The behavior of the model suggests that these results may be useful in the understanding of the breaking mechanism in deep water.

The applicability of one-dimensional wave generation models to fetches that are restricted in width as well as length is considered. An analytical estimation approach, the spectral contribution method, is developed and compared with the established effective fetch method. Estimated wave fields are compared with measured results from four sites with varying degrees of fetch restriction. For width restricted fetches, the spectral contribution method is a more efficient estimator than the effective fetch method. Two one-dimensional wave generation models and two directional distribution models are investigated. For limited fetches, the JONSWAP spectrum appears slightly superior to the Bretschneider spectrum and the Pierson, Neumann, and James distribution yields better estimates than the Longuet-Higgins, Cartwright, and Smith distribution.

An analytical technique is developed for correcting the time‐averaged net sediment transport rate under oscillatory flows for the effects of the cessation of transport whenever the magnitude of the near‐bottom velocity is less than some threshold value. This estimation scheme eliminates the analytical complexity of incorporating the threshold effect directly into the transport model. The threshold speeds are calculated using an empirical formulation. Using a simple model of longshore transport across the surf zone and employing some recent findings on velocity distributions, the magnitudes of threshold effects are explored for both broadband and monochromatic waves. An explanation for the observed difference in longshore transport efficiency for laboratory and field observations is suggested. A simple model for cross‐shore transport is used to explore the effects of threshold of motion on this transport mechanism. [Graphical presentations are used to show under what combinations of wave height, wave perio...

Previous studies investigated the correlation between predictions of existing cross-shore transport models using observed surf zone parameters and the measured beach face responses from Torrey Pines Beach, California. Following the Torrey Pines experiment, 3 more Nearshore Sediment Transport Study (NSTS) data sets were obtained by the present writer: (1) from Scripps Beach, California; (2) from Virginia Beach, Virginia; and (3) from Santa Barbara, California. These results are presented to enable testing of cross-shore transport models.

A six‐year program, with a budget of $6 million, was undertaken by the Office of Sea Grant in 1976 to develop improved engineering predictive models for transport of sediment in and near the surf zone by waves and currents. The project, called the Nearshore Sediment Transport Study, has involved ten investigators from six different institutions who worked cooperatively on field studies. Three major field experiments have been conducted, the first in 1978, the second in 1980, and the last in 1981. The first two field experiments had a duration of approximately a month and involved synoptic measurements of more than 100 parameters of surf zone dynamics and sediment response. Sand tracer experiments were also performed and the last two field sites include concurrent trap experiments for longshore transport. All data were recorded on magnetic tape and more than a billion words were obtained in the second experiment. In the final two years of the project, emphasis has been placed on the formulation of predicti...

Describes laboratory experiments at one-half scale using simulated random seas and field tests at full scale of an installation of a dynamic floating breakwater system in a limited fetch situation. An analytical model is described which successfully predicted the performance of a tethered float breakwater configuration, given the incident wave spectrum. The methodology for selecting the arbitrary resistance coefficients in the predictive model is considered. Predicted and measured performance data for a total of 60 laboratory and field experiments are displayed, covering a very broad range of wave climates.

Seven West Coast sites are selected having from one to three years of nearshore directional wave measurements several times a day during the period 1979–82. Time series of daily net longshore transport are estimated using the energy flux method, based upon measured Sxy. Investigations are made on frequency and cumulative distributions of transport, and from these, a number of statistics characterizing the degree of episodic transport are generated. The transport is found to be very episodic, with almost half of the gross transport occurring during only 10% of the time. The maximum transport occurring in a single day each year produced between ten times, and more than 600 times, the mean daily net transport. Inferences concerning the design requirements for sand bypass systems are drawn from the statistics of episodicity.

During the Nearshore Sediment Transport Study experiment at Torrey Pines Beach, CA, in November 1978, beach profiles were measured over a several week period concurrent with extensive daily measurements of wind, waves, and currents. These surf zone data were used to predict the cross-shore transport of sand using eight models available in the literature. Several models were found to have skill in predicting major changes, but none was capable of predicting more than a third of the total beach volume variability.

A system is described for sampling coastal data from a remote central station under computer control. The data gathering network handles wave measurements from offshore buoys and nearshore pressure sensors, and velocity components from current meters and anemometers. Coastal station locations range from Hawaii to North Carolina with system interconnection through ordinary dial up telephone lines. Data are objectively edited automatically, analyzed and are available for remote display within a few minutes of the observation. Measuring instruments, system hardware, operations, and reports are described.