ornia. Data were first corrected for dropouts. Next the data quality was verified through a consistency check on the redundant velocity measurements of opposing beams, an evaluation of high frequency spectral noise levels, and a comparison of velocity and pressure measurements using linear wave theory. Finally wave height and direction spectra estimated from the ADCP data were compared to data from a directional wave buoy. The analysis revealed that the ADCP data can suffer from low signal to noise ratios in benign conditions and deeper water. Whereas the wave height estimates are sensitive to these errors, the wave direction estimates are surprisingly robust.

Approved for public release; distribution is unlimited. / Swell propagates across thousands of kilometers of ocean in almost unchanged parallel wave fronts. Within the nearshore region however, refraction causes wave fronts to turn toward shallow depths transforming the wave field. The Nearshore Canyon Experiment (NCEX) Pilot, conducted from October 10 to October 17, 2002, observed wave transformation across the Scripps and La Jolla canyon system near San Diego, CA. Four Datawell Directional Waverider Buoys, three Nortek Vector PUV recorders, and two pressure sensors were deployed in depths ranging from 10 to 300 m. Observed energy density spectra and mean propagation directions were examined for three case studies representative of the range of observed swell conditions. Observations were compared to predictions of a back-refraction model provided by Dr. William O'Reilly. Observations indicate that refraction causes the waves to propagate along the deep axes of the Scripps and La Jolla canyons. At the shallow canyon heads, the convergence and divergence of ray trajectories cause extreme (2-3 orders of magnitude!) spatial variations in wave energy. Considering the complexity of the canyon environment, predictions of wave transformation agree surprisingly well with observations. / Ensign, United States Naval Reserve

This thesis presents an examination of the nearshore wave bottom boundary layer under conditions of significant sediment response. Using both field observations and simple models, the response of the bottom boundary layer to random waves is shown to have a complex behavior. First, the linearized wave bottom boundary layer governing equation is solved with a transformation of the cross-shore velocity to a distorted spatial domain, resulting in an analytic expression for the temporal and vertical structure of the cross-shore velocity under an arbitrary wave field. Model predictions of the bed shear velocity are in good agreement with laboratory measurements. The model is limited by assuming zero velocity at a fixed bed and that turbulence generation is solely due to bottom shear. Next, a comprehensive set of near bed cross-shore velocity, sediment suspension, and bed elevation observations, collected in 2 m water depth on the North Carolina coast, are presented. The observations show a cross-shore velocity structure which decays with increasing proximity to the bed as predicted by simple theory. Bottom shears based on rms amplitude decay and time-averaged phase shifts are lower than model predictions and may be indicative of more rapid mixing of momentum than assumed in the above model. Also, frequency-dependent estimates of the phase and amplitude vertical structure show a nonlinear response of the wave bottom boundary layer over the incident band. Through most flow phases, estimates of turbulent kinetic energy increase linearly from the bed, however under large wave crests, enhanced turbulence levels are observed and are well correlated to active sediment suspension events. Estimates of dissipation rates are significantly less than those observed in an actively breaking surf zone wave, and significantly greater than those observed in ocean boundary layers, and continental shelf current boundary layers. Finally, an Oregon coast field experiment showed an intermittent high frequency velocity variance structure which was correlated to suspended sediment events. A linear shear instability analysis determined that during the period of flow reversal there exists a potential for generating turbulence due to shear instabilities of the vertical structure of cross-shore velocity. / Graduation date: 1997

Thesis (M.S. in Physics)--Naval Postgraduate School, December 2009. / Thesis Advisor(s): Walters, Donald. Second Reader: Borden, Brett. "December 2009." Description based on title screen as viewed on January 27, 2010. Author(s) subject terms: Ocean waves, Laser Scattering, Absorption, Refraction. Includes bibliographical references (p. 55). Also available in print.

Thesis (Ph. D.)--University of California, San Diego, 2000. / Vita. Includes bibliographical references.

Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Thomas H.C. Herbers, Edward B. Thornton. Includes bibliographical references (p. 37). Also available online.

Experiments on regular two dimensional waves breaking over an artificial sand bar were conducted in a glass walled flume to facilitate an investigation of the hydrodynamic processes that evolve in the surf zone. The instantaneous time averaged velocities and the velocity flow fields have been measured using digital video imaging and analysis techniques. The instantaneous velocity flow fields were then processed, resulting in the phase-ensemble-averaged velocities, time averaged velocities and energy and momentum fluxes. The time averaged velocities above the trough level have been found to be much higher than those below. After wave breaking, kinetic energy and momentum flux are shown to increase, reaching a peak value and decreasing thereafter. An estimate of the relative density of the fluid in the wave crests was obtained by comparing the forward and reverse velocity fluxes. Other surf zone physical parameters such as the free surface displacements, wave heights across the flume and potential energies have been derived from the resistive wave gauge measurements. A spectral analysis of the water level time series was conducted and the energy growth in each spectral component was examined. It was noticed that there is a transfer of energy from the primary frequency of the wave maker to higher harmonics. Also, wave breaking has little effect on the amplitudes of the harmonic components. The roller and aeration areas were also computed. Two methods of estimating the roller area have been explored and these are the analysis of the wave gauge measurements of the surface elevation and the analysis of the video images. There was agreement between the results obtained and those published in the literature. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2005.

Graduation date: 1986

Graduation date: 1982

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1989. / Includes bibliographical references. / Microfiche. / xix, 113 leaves, bound ill. 29 cm