Water waves are one of the principal causes of shoreline changes. When waves break along the shore, they release their energy and momentum and give rise to a longshore current. The longshore current, along with the stirring action of the waves, is the primary mechanism for longshore sediment transport. The longshore sand transport rate is an essential factor determining erosion or accretion along a coast. If the longshore sand transport rate can be accurately estimated, a quantitative picture of shoreline evolution can be evaluated, including changes of the shoreline due to marine structures. In the present study, analytical and numerical models are developed based on a longshore current model for random waves and a sediment transport formulation by Thornton to predict the cross-shore sediment transport distribution and to compute the total volume of sand transport rate. The model is compared with the field data acquired from Leadbetter Beach, Santa Barbara, California.

The omni-present low frequency wave motion (30-300 sec) contains a substantial fraction of the total wave energy inside the surf zone. A more complete description of nearshore wave processes considers incident short period waves superposed on, and interacting with, long standing waves. The wind waves are modulated in amplitude, wavenumber and direction due to relatively slowly varying depth changes caused by the long waves. The energy in the wind wave band is enhanced by side band growth at the sum and difference frequencies of short and long waves (order 15% at the shoreline). The modulation is identified in the analysis of field data as a positive correlation between the long waves and the wind wave envelope near the shoreline. Considering oblique incident waves, a steady longshore current showing a non-vanishing current at the shoreline is found as a result of the non-linear interaction between monochromatic incident and infragravity waves. An analytical solution describing the unsteadiness of the longshore current is developed. Keywords include: Infragravity, Longshore Current, Sediment transport, and Surf zone dynamics. (Theses).

The procedures and results of an experiment performed to measure the longshore sand transport rate in the surf zone as part of the SUPERDUCK field data collection project are described in this report. Cross-shore distributions of the longshore sand transport rate, as well as its variation at a point in the surf zone through time, were measured with portable sand traps. Comparison of measurements made with two closely spaced traps indicates trap reliability and consistency. The longshore sand transport rate measured at SUPERDUCK was found to be closely related to the product of wave height and longshore current speed, consistent with previously derived theoretical models of transport. The correlation was considerably improved, however, by including corrections due to energy dissipation introduced by breaking waves and the variation in the longshore current speed. A complete listing of the sand transport rate, wave height, longshore current, and sand grain size data is given. Keywords: Sediment transport, Field experiment, Longshore sand transport, Streamer trap, Surf zone.

Masters Theses in the Pure and Applied Sciences was first conceived, published, and disseminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS) * at Purdue University in 1 957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dissemination phases of the activity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all con cerned if the printing and distribution of the volumes were handled by an interna tional publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Cor poration of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 29 (thesis year 1984) a total of 12,637 theses titles from 23 Canadian and 202 United States universities. We are sure that this broader base for these titles reported will greatly enhance the value of this important annual reference work. While Volume 29 reports theses submitted in 1984, on occasion, certain univer sities do report theses submitted in previous years but not reported at the time.

Local down- drift profile changes were found to be poor indicators of the local updrift impoundment. In general, the longshore transport profiles were found to be bimodal with peaks just landward of the breakpoint and near the shoreline; the relative significance of the longshore transport shifted from the near-breakpoint peak to the near-shoreline peak as the wave condition varied from spilling to collapsing breakers. Alternately stated, the longshore transport distribution appeared strongly beach profile dependent, as transport was most pronounced over local regions of high bed steepness. Between 10% and 30% of the total longshore transport was observed seaward of the breakpoint for all cases. Long- shore transport in the swash zone represented at least 5% to 60% of the total transport, where the largest swash contributions were associated with plunging/collapsing and collapsing surf conditions.