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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.

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.

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.

The details of a new oscillatory flow tunnel at Scripps Institution of Oceanography are discussed. The flow tunnel has a large crosssection and large water excursion distance. The piston motion is programmable. The test bed can be tilted. These, and other aspects, make the facility useful to a wide variety of oscillatory flow sediment transport experiments.

Southern California was subjected to a series of severe winter storms in 198 3 that caused record damages to the coast. In the aftermath of the storms, emergency repairs were made and new designs were developed that responded to the severe conditions. These designs were often considerably more conservative than those previously undertaken. Agencies, owners, and engineers were compelled to use both higher design criteria and longer recurrence intervals to account for the wave characteristics and water levels that caused damages along the coast. This paper briefly discusses the unusual circumstances of the storm conditions and the associated damages. The primary purpose of the paper is to present new data that incorporates the effects of the 1983 winter storms to estimate the change in perception of what the wave climate and design criteria may be in this highly developed coastline. The results indicate that the design wave height for a given recurrence interval has increased approximately 26 percent, the wave periods are longer than previously used, and the severe storms tend to coincide with the extreme water levels. The engineer should consider the impacts of the 1983 winter storms in future designs. Despite the record damages, many structures survived. Merely using the highest water elevations and most severe waves of record may not be the most prudent design criteria. The concept of project life and economics must be employed to develop a design.

The California Department of Navigation and Ocean Development (DNOD), responsible for shoreline protection within the state, was particularly aware of the lack of coastal wave statistics to support their beach erosion program. As a direct result of the 1974 ASCE-sponsored New Orleans Conference on Ocean Wave Measurement and Analysis, discussion was initiated within DNOD and then with the Scripps Institution of Oceanography (SIO) at La Jolla, on the feasibility o"f establishing a regional wave monitoring network for California. The initial specification presented by DNOD was for a 200-station network reporting directional wave spectra twice daily for a period of ten years. SIO ocean engineering personnel responded with a system concept employing low-cost pressure transducers hardwired to shore with a dialup telephone data gathering link to a central station. The initial cost estimates appeared attractive when compared with Corps of Engineers experience as reported in Peacock (1974). As a result, a small program was funded in February 1975 at Scripps to demonstrate critical hardware items through the breadboard stage. With the successful completion of this work, additional funds were allocated by DNOD as matching funds for a California Sea Grant Project. Th_e first station in the network began operation on 3 December 1975 at Imperial Beach, California. A second station was added at Ocean Beach (San Diego) on 27 March 1976, a third at SIO (La Jolla) on 18 May 1976 and the fourth at Oceanside, California on 2 June 1976. The locations of these initial stations are shown in Figure 1. Considerable effort has been directed during the past 10 years toward the development of numerical models to predict deep-water wave conditions from meteorological data. Reasonable results have been obtained and sufficient accuracy achieved to allow routing of both commercial and military ship traffic.

The models for predicting longshore transport of sediment along straight coastlines that are presently in general use were derived empirically from very sparse measurements of both the forcing function (waves and currents) and the response function (sediment motions). A detailed treatment of these data sets is contained in Greer and Madsen (1978). In addition to the generally unsatisfactory nature of the basic measurements upon which they were based, the models may be deficient because they fail to employ such potentially significant factors as wind stress, sediment size distribution, bottom slope and spatial variations in waves and currents, including the effects of rip currents. Although these models have served certain engineering needs, there is a strong measure of uncertainty in the coastal engineering community about their general applicability. Certainly, because they are empirical rather than physically reasoned models, there is no rational means for extending their usefulness to predicting transport where coastlines are not straight -- such as the case of a tidal inlet. The economic impact of sediment transport in the nearshore regime is enormous and the need for improved predictive tools appears to be universally accepted. To be most useful, these improved models must be globally applicable. This implies very strongly that they must be based upon a thorough understanding of surf zone dynamics and the details of the response of the sediment. The surf zone flow fields are highly complex and nonlinear, implying an equally complex and difficult system of sediment responses. Characterizing the entire forcing and response functions simultaneously requires large and expensive field measurement programs that greatly exceed the present state of the art of measurement and analysis.' The approach of the last two decades of single investigators working at laboratory scale or in the ocean with a few single point measurements would not appear to ever meet these needs. However, the present costs for coastal dredging and shoreline protection, which can be measured in billions of dollars on a world scale, argue for a major undertaking to develop better predictive tools. In an attempt to satisfy these needs, an ad hoc group was formed at the Fifteenth Coastal Engineering Conference in Honolulu to plan a large scale and coordinated series of investigations leading to improved sediment transport predictive models. Less than a year later, the Nearshore Sediment Transport Study was initiated under the sponsorship of the Office of Sea Grant.

Seymour and King (1982) evaluated eight models for predicting cross-shore transport using beach profile data from the Torrey Pines experiment of the Nearshore Sediment Transport Study (NSTS). None of the models showed useful skill in predicting the sense, or direction, of transport. Three more data sets were acquired under NSTS and have been used in the present work to re-evaluate the original four models as well as another six not previously tested. The three new data sets include two nominally plane West Coast beaches and a barred beach on the Atlantic coast, each under a variety of wave conditions. Six of the models evaluated claimed a capability to predict the sense of the cross-shore transport, two predicted the beach slope as a result of cross-shore movement, and two gave detail predictions of changes to the beach profile position and shape. The performance of the six models predicting direction of transport ranged from a skill factor of 0.49 (less than chance) to only 0.68. Five of the models required large changes to their calibration factor (usually based upon laboratory data) in order to have approximately the same skill in predicting erosion or accretion. One of the slope models was validated and the other gave no useful results. One of the two generalized models gave interesting results in predicting the time history of profile changes on the plane beaches for which it was developed. The other general model was not evaluated because it exhibited the lowest skill in predicting direction of transport.

Waves with exceptional height and periods caused severe damage along the coast of California in 1982-83. Because these large wave events coincided with a strong El Nino-Southern Oscillation (ENSO) climatic anomaly, which occurs 20-25 times per century, there was interest in determining if the extreme waves resulted from the ENSO or its related features. The meteorological setting featured a very large and intense low pressure zone over the north-central Pacific. Associated with this Pacific-wide pattern, a series of large mid-latitude storms developed at about weekly intervals and produced exceptionally long fetchs directed at the California Coast. Two time series of extreme wave events, using buoy data after 1981 and hindcasts before, were used covering the period from 1900 to 1984. One series considered waves with significant heights greater than 3 m (10 ft) and the second for those greater than 6 m (20 ft.) These were compared with a time history of ENSOs for the same period. A strong association was established between northern hemisphere winters during ENSO years and large wave events in Southern California. Strong ENSO winters had the largest storm waves, moderate ENSOs less intense waves, and weak ENSOs tended not to have storm waves greater than the threshold value used in this study. The correlation between large waves and ENSO years is significant at the 1% level. The correlation between lack of large waves and non-ENSO years is significant at the 0.5% level. Because of the great southerly extent of the most energetic storms, a large number of energetic wave trains approach the coast from the west, rather than the northwest, as previously assumed by many. ENSO winters are responsible for producing all of the wave events in this study with both heights greater than 6 m and periods of peak energy longer than 19 seconds. Five out of nine eastern Pacific tropical storms making landfalls on California in the 85 year period occurred during the late northern summer of ENSO years.

The measurement of nearshore profiles has been the traditional method for evaluating on- and offshore transport of beach sand by waves. The measurement on that portion of the beach face which is dry at low tide presents no particular problems and can be effectively accomplished with conventional rod and level surveying techniques. Once the measurement location moves into the wet part of the foreshore, however, the problems rapidly increase. In general, it requires an extremely dedicated rod man to remain on position in breakers larger than a meter, although measurements in breakers up to 2 meters in height have been accomplished on a nonroutine basis. When waves exceed this height, or when the water depth exceeds the ability of a man to stand and hold the rod, this method must be abandoned. In deeper water, and well outside the surf zone, a boat and fathometer approach is normally employed with considerable loss in vertical and horizontal accuracy. In particular, the vertical resolution is decreased by the uncertainties in knowledge of the instantaneous sea level because of the combination of tides, waves and storm surge. If the tides are large and the waves small, it is possible to achieve an overlap between the boat survey and the shore survey. When the wave height exceeds the ability of the boat to operate, this method also must be abandoned. Although larger boats can operate in larger waves, they are generally also restricted to deeper water. The result of all of the restrictions described above is that profiles can be measured with reasonable accuracy only during periods of low waves. Unfortunately, the episodes of greatest interest are the rapid cutting back of the beach face and the accompanying offshore bar building which occur during times of high waves. The technology to measure the storm waves has been available for many years. The ability to correlate wave parameters with offshore transport rates requires the ability to make accurate profiles from the dry beach through and beyond the breaker line under storm wave conditions. This paper describes a vehicle that was developed to meet this need.

Knowledge of the distribution of wave intensity along a shoreline can be used to infer deepwater directional information for non-locally generated waves. Measurement of this energy distribution may be accomplished using a network of widely spaced nearshore wave gages known as an intensity array. Analysis for intensity array data uses the principle that deepwater swell of a given frequency produces varying patterns of nearshore wave intensity, which depend on the unrefracted directional energy distribution for that frequency. Assuming linear wave propagation to the measurement sites, this dependence may be inverted and applies at all frequencies. Energy spectra measured at the intensity array may be used in this manner to estimate the deepwater directional spectrum. In Part II, details of the relationship between deepwater directional spectrum and nearshore energy spectra are discussed. In Part III, intensity array data are applied to detection of waves incident within a narrow directional interval. Part IV describes the application of an intensity array to detection of long period southern swell in San Diego, California. Comments regarding the relative merits of the method follow in Part V.