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Young, AP, Guza RT, O'Reilly WC, Burvingt O, Flick RE.  2016.  Observations of coastal cliff base waves, sand levels, and cliff top shaking. Earth Surface Processes and Landforms. 41:1564-1573.   10.1002/esp.3928   AbstractWebsite

Concurrent observations of waves at the base of a southern California coastal cliff and seismic cliff motion were used to explore wave-cliff interaction and test proxies for wave forcing on coastal cliffs. Time series of waves and sand levels at the cliff base were extracted from pressure sensor observations programmatically and used to compute various wave impact metrics (e.g. significant cliff base wave height). Wave-cliff interaction was controlled by tide, incident waves, and beach sand levels, and varied from low tides with no wave-cliff impacts, to high tides with continuous wave-cliff interaction. Observed cliff base wave heights differed from standard Normal and Rayleigh distributions. Cliff base wave spectra levels were elevated at sea swell and infragravity frequencies. Coastal cliff top response to wave impacts was characterized using microseismic shaking in a frequency band (20-45Hz) sensitive to wave breaking and cliff impacts. Response in the 20-45Hz band was well correlated with wave-cliff impact metrics including cliff base significant wave height and hourly maximum water depth at the cliff base (r(2) = 0.75). With site-specific calibration relating wave impacts and shaking, and acceptable anthropogenic (traffic) noise levels, cliff top seismic observations are a viable proxy for cliff base wave conditions. The methods presented here are applicable to other coastal settings and can provide coastal managers with real time coastal conditions. Copyright (C) 2016 John Wiley & Sons, Ltd.

George, R, Flick RE, Guza RT.  1994.  Observations of Turbulence in the Surf Zone. Journal of Geophysical Research-Oceans. 99:801-810.   10.1029/93jc02717   AbstractWebsite

Turbulence generated by waves breaking on a natural beach is examined using hotfilm anemometer data. Turbulence intensity is estimated from dissipation rates determined from wavenumber spectra of short (1/8 s) hotfilm time series. The resulting Froude-scaled turbulence intensities are relatively uniform between the seabed and the wave trough level and are similar in vertical structure but lower in magnitude than in existing laboratory studies. The magnitudes of the turbulence intensities observed in both the field and laboratory are consistent with an existing macroscopic model of bore dissipation in the surf zone. Scaling by this bore model relates turbulence intensities generated by monochromatic waves in small-scale laboratory experiments to those generated by random waves in the natural surf zone.

Bromirski, PD, Flick RE, Graham N.  1999.  Ocean wave height determined from inland seismometer data: Implications for investigating wave climate changes in the NE Pacific. Journal of Geophysical Research-Oceans. 104:20753-20766.   10.1029/1999jc900156   AbstractWebsite

Knowing the wave climate along the California coast is vital from the perspectives of climatological change and planning shore protection measures. Buoy data indicate that the wave climate is very similar along much of the California coast. We show that elements of the wave climate can be accurately reconstructed using near-coastal inland broadband seismometer data. Such reconstructions are possible because swell approaching the coast generates pressure fluctuations that are locally transformed into seismic waves at the seafloor that propagate inland and are detectable by land-based seismometers. Buoy and seismometer data show that most of the microseism energy recorded inland near the coast is generated from wave events at nearby coastal locations. A site-specific, empirically derived seismic-to-wave transfer function is demonstrated to be applicable to seismic data from the same location for any year. These results suggest that ocean wave heights estimated from near-coastal broadband seismometer data are sufficiently reliable for monitoring the coastal wave height when buoy data are unavailable, provided that adequate simultaneous nearby buoy measurements are available to calibrate the seismometer data. The methodology presented here provides an important tool that allows the investigation of potential wave climate changes from reconstructions using archived seismic data collected since the 1930s.

Elwany, MHS, Flick RE, Aijaz S.  1998.  Opening and closure of a marginal southern California lagoon inlet. Estuaries. 21:246-254.   10.2307/1352472   AbstractWebsite

Over the past 50 yr, direct observations of the inlet status (open or closed) of San Dieguito Lagoon, a typical southern California lagoon located in Del Mar, California, have shown that river flooding is the major natural determinant of inlet conditions on time scales longer than a few years. River flooding is strongly dependent on rainfall in the San Dieguito River watershed and on the influences of two water storage reservoirs in the area. Rainfall fluctuates on yearly and longer time scales and undergoes cycles of wet and dry periods. Over short time periods, ranging from a few months to several years, inlet status is primarily determined by the available tidal prism and littoral sand transport. Recognition of these factors is crucial in order to correctly evaluate the probability that a small lagoon will remain open naturally. A probability approach is essential because the variables controlling inlet conditions are random in nature. The results of our study show that the inlet will remain open naturally 34% of the time. The tendency to remain open is vastly smaller during years of dry weather (12%) versus times of above-average rainfall (66%).