Publications

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1975
Sanford, TB, Flick RE.  1975.  Relationship between Transport and Motional Electric Potentials in Broad, Shallow Currents. Journal of Marine Research. 33:123-139. AbstractWebsite
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1976
Inman, DL, Nordstrom CE, Flick RE.  1976.  Currents in Submarine Canyons - Air-Sea-Land Interaction. Annual Review of Fluid Mechanics. 8:275-310.   10.1146/annurev.fl.08.010176.001423   AbstractWebsite
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1980
Flick, RE, Guza RT.  1980.  Paddle Generated Waves in Laboratory Channels. Journal of the Waterway Port Coastal and Ocean Division-Asce. 106:79-97. AbstractWebsite
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1981
Flick, RE, Guza RT, Inman DL.  1981.  Elevation and Velocity-Measurements of Laboratory Shoaling Waves. Journal of Geophysical Research-Oceans and Atmospheres. 86:4149-4160.   10.1029/JC086iC05p04149   AbstractWebsite

Measurements of wave elevation and orbital velocity in the shoaling, breaking, and bore regime of single-frequency laboratory waves show that third-order Stokes theory, when energy flux is conserved, predicts the wave height change and harmonic growth in the regime where the Ursell number Ur = (H/ h)/(kh)2 is 0(1) or less. Shoreward of the Stokes region and up to the breakpoint, harmonic amplitudes are well described by the cnoidal theory. It is shown theoretically that a smooth transition regime exists between Stokes and cnoidal regions for waves which eventually break by plunging. The wave profile asymmetry about the vertical plane observed in near-breaking waves and bores is due to slow changes of phase of the harmonics relative to the primary wave as the wave train shoals. By contrast, only asymmetry about the horizontal plane is possible in the Stokes and cnoidal wave theories, since these classical solutions allow no relative phase shifts between harmonics. Velocity measurements made with hot-film anemometers show that ‘unorganized’ fluctuations at the bottom under breaking waves are of the order of half the rms amplitude of the wave-induced ‘organized’ flow. The correlation between surface elevation and bottom velocity under breakers and bores suggests that turbulence contributes more strongly to the unorganized flow at the bottom under plunging than under spilling waves.

1984
1985
Zetler, BD, Flick RE.  1985.  Predicted Extreme High Tides for California - 1983-2000. Journal of Waterway Port Coastal and Ocean Engineering-Asce. 111:758-765. AbstractWebsite
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Zetler, BD, Flick RE.  1985.  Predicted Extreme High Tides for Mixed-Tide Regimes. Journal of Physical Oceanography. 15:357-359.   10.1175/1520-0485(1985)015<0357:pehtfm>2.0.co;2   AbstractWebsite
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1986
1994
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.

1995
Elwany, MHS, Oreilly WC, Guza RT, Flick RE.  1995.  Effects of Southern California Kelp Beds on Waves. Journal of Waterway Port Coastal and Ocean Engineering-Asce. 121:143-150.   10.1061/(asce)0733-950x(1995)121:2(143)   AbstractWebsite

The effect of a Macrocystis kelp forest on shoreward propagating surface gravity waves was measured. Observations were made over a 67-day period at four locations around a 350-m-wide kelp bed off Carlsbad, California. Instruments were located directly offshore and onshore of the kelp bed at depths of 13 m and 8 m, respectively, and at control stations at the same depths, but displaced 750 m alongshore, away from the kelp bed. The bathymetry between the offshore and onshore sites was gently sloping and featureless. The measured spectra, significant wave height, mean wave direction at peak frequency, and total radiation stress differed only slightly between the offshore kelp and control stations and were similar at the onshore sites. The similarity of the wave field at the onshore kelp and control sites shows that this typical southern California kelp bed, with an average density of about 10 plants per 100 m(2), does not have a significant effect on waves. These measurements can be used to place upper bounds on drag coefficients in numerical models of the effect of kelp on waves.

1996
Elwany, MHS, Flick RE.  1996.  Relationship between kelp beds and beach width in Southern California. Journal of Waterway Port Coastal and Ocean Engineering-Asce. 122:34-37.   10.1061/(asce)0733-950x(1996)122:1(34)   AbstractWebsite

The relationship between the width of kelp beds and the width of the beaches inshore was examined in the San Diego region of Southern California. Two statistical approaches were used. The first simply determined the correlation between kelp-bed width and adjacent-beach width. A small (0.3), but statistically significant, positive correlation was found in the 20% of shoreline that had both a nonzero beach width and an offshore kelp bed; however, no correlation was found when the entire shoreline was considered. The second method examined differences in width between beaches inshore of the kelp beds and those immediately to the north and south. No statistically significant differences were found. The overall conclusion is that there is no clear correlation or consistent pattern indicating that offshore kelp beds have any direct influence on adjacent-beach width.

1998
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%).

1999
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.

2003
Flick, RE, Murray JF, Ewing LC.  2003.  Trends in United States tidal datum statistics and tide range. Journal of Waterway Port Coastal and Ocean Engineering-Asce. 129:155-164.   10.1061/(asce)0733-950x(2003)129:4(155)   AbstractWebsite

Yearly tidal datum statistics and tide ranges for the National Oceanic and Atmospheric Administration/National Ocean Service long-term stations in the United States tide gauge network were compiled and used to calculate their trends and statistical significance. At many stations, significant changes in the tide range were found, either in the diurnal tide range [mean higher high water (MHHW)-mean lower low water (MLLW)], or mean tide range [mean high water (MHW)-mean low water (MLW)]. For example, at San Francisco, the diurnal tide range increased by 64 mm from 1900 to 1998, while at Wilmington, N.C., the mean tide range increased at a rate of 542 mm per century from 1935 to 1999. This analysis suggests that any studies concerned with present or future water levels should take into account more tidal datum statistics than just mean sea level (MSL). For example, coastal flooding and storm damage studies should consider trends in high water levels, since it is the peak values that cause flooding and determine the design of coastal structures. For habitat restoration planning, mean low water and tide range changes should be considered.

Elwany, MHS, Flick RE, Hamilton MM.  2003.  Effect of a small southern California lagoon entrance on adjacent beaches. Estuaries. 26:700-708.   10.1007/bf02711981   AbstractWebsite

This paper considers the effects of natural and artificial openings of a typical, small, southern California coastal estuarine lagoon on the adjacent barrier beach. A detailed history of beach profiles and lagoon entrance transects before and after flood-induced and artificial openings of San Dieguito Lagoon in Del Mar, California, has been analyzed. The results suggest that there is no statistically significant erosional effect on the adjacent beach when the lagoon inlet is artificially opened to tidal flow.

Bromirski, PD, Flick RE, Cayan DR.  2003.  Storminess variability along the California coast: 1858-2000. Journal of Climate. 16:982-993.   10.1175/1520-0442(2003)016<0982:svatcc>2.0.co;2   AbstractWebsite

The longest available hourly tide gauge record along the West Coast (U. S.) at San Francisco yields meteorologically forced nontide residuals (NTR), providing an estimate of the variation in "storminess'' from 1858 to 2000. Mean monthly positive NTR (associated with low sea level pressure) show no substantial change along the central California coast since 1858 or over the last 50 years. However, in contrast, the highest 2% of extreme winter NTR levels exhibit a significant increasing trend since about 1950. Extreme winter NTR also show pronounced quasi-periodic decadal-scale variability that is relatively consistent over the last 140 years. Atmospheric sea level pressure anomalies (associated with years having high winter NTR) take the form of a distinct, large-scale atmospheric circulation pattern, with intense storminess associated with a broad, southeasterly displaced, deep Aleutian low that directs storm tracks toward the California coast.

2005
Bromirski, PD, Cayan DR, Flick RE.  2005.  Wave spectral energy variability in the northeast Pacific. Journal of Geophysical Research-Oceans. 110   10.1029/2004jc002398   AbstractWebsite

The dominant characteristics of wave energy variability in the eastern North Pacific are described from NOAA National Data Buoy Center ( NDBC) buoy data collected from 1981 to 2003. Ten buoys at distributed locations were selected for comparison based on record duration and data continuity. Long- period ( LP) [ T > 12] s, intermediate- period [ 6 <= T <= 12] s, and short- period [ T < 6] s wave spectral energy components are considered separately. Empirical orthogonal function ( EOF) analyses of monthly wave energy anomalies reveal that all three wave energy components exhibit similar patterns of spatial variability. The dominant mode represents coherent heightened ( or diminished) wave energy along the West Coast from Alaska to southern California, as indicated by composites of the 700 hPa height field. The second EOF mode reveals a distinct El Nino-Southern Oscillation (ENSO)-associated spatial distribution of wave energy, which occurs when the North Pacific storm track is extended unusually far south or has receded to the north. Monthly means and principal components (PCs) of wave energy levels indicate that the 1997 - 1998 El Nino- winter had the highest basin- wide wave energy within this record, substantially higher than the 1982 - 1983 El Nino. An increasing trend in the dominant PC of LP wave energy suggests that storminess has increased in the northeast Pacific since 1980. This trend is emphasized at central eastern North Pacific locations. Patterns of storminess variability are consistent with increasing activity in the central North Pacific as well as the tendency for more extreme waves in the south during El Nino episodes and in the north during La Nina.

2008
Bromirski, PD, Flick RE.  2008.  Storm surge in the San Francisco Bay/Delta and nearby coastal locations. Shore & Beach. 76:29-37. Abstract

California’s San Francisco Bay/Sacramento-San Joaquin Delta (bay/delta) estuary system is subject to externally forced storm surge propagating from the open ocean. In the lower reaches of the delta, storm surge dominates water level extremes and can have a significant impact on wetlands, freshwater aquifers, levees, and ecosys- tems. The magnitude and distribution of open-ocean tide generated storm surge throughout the bay/delta are described by a network of stations within the bay/delta system and along the California coast. Correlation of non-tide water levels between stations in the network indicates that peak storm surge fluctuations propagate into the bay/delta system from outside the Golden Gate. The initial peak surge propa- gates from the open ocean inland, while a trailing (smaller amplitude) secondary peak is associated with river discharge. Extreme non-tide water levels are generally associated with extreme Sacramento-San Joaquin river flows, underscoring the po- tential impact of sea level rise on the delta levees and bay/delta ecosystem.

Cayan, DR, Bromirski PD, Hayhoe K, Tyree M, Dettinger MD, Flick RE.  2008.  Climate change projections of sea level extremes along the California coast. Climatic Change. 87:S57-S73.   10.1007/s10584-007-9376-7   AbstractWebsite

California's coastal observations and global model projections indicate that California's open coast and estuaries will experience rising sea levels over the next century. During the last several decades, the upward historical trends, quantified from a small set of California tide gages, have been approximately 20 cm/century, quite similar to that estimated for global mean sea level. In the next several decades, warming produced by climate model simulations indicates that sea level rise (SLR) could substantially exceed the rate experienced during modem human development along the California coast and estuaries. A range of future SLR is estimated from a set of climate simulations governed by lower (B1), middle-upper (A2), and higher (A1fi) GHG emission scenarios. Projecting SLR from the ocean warming in GCMs, observational evidence of SLR, and separate calculations using a simple climate model yields a range of potential sea level increases, from 11 to 72 cm, by the 2070-2099 period. The combination of predicted astronomical tides with projected weather forcing, El Nino related variability, and secular SLR, gives a series of hourly sea level projections for 2005-2100. Gradual sea level rise progressively worsens the impacts of high tides, surge and waves resulting from storms, and also freshwater floods from Sierra and coastal mountain catchments. The occurrence of extreme sea levels is pronounced when these factors coincide. The frequency and magnitude of extreme events, relative to current levels, follows a sharply escalating pattern as the magnitude of future sea level rise increases.

2009
Young, AP, Flick RE, Gutierrez R, Guza RT.  2009.  Comparison of short-term seacliff retreat measurement methods in Del Mar, California. Geomorphology. 112:318-323.   10.1016/j.geomorph.2009.06.018   AbstractWebsite

Seacliff retreat has been variously characterized as the recession rate of the cliff top, of the cliff base, and as the bulk recession rate based on volumetric changes of the entire cliff face. Here, these measures of retreat are compared using nine semi-annual airborne LiDAR (Light Detection And Ranging) surveys of southern California seacliffs. Changes in the cliff base location (where the steeply sloping cliff face intersects the beach) include cliff retreat owing to basal erosion, but also reflect changes in beach sand level and basal talus deposits. Averaged over the 2.5 km alongshore study span, the cliff base actually prograded seaward about 12 cm during the 4-year study. Cliff top change was dominated by few, relatively large (several meters) localized retreats. Cliff face changes, that include failures and deposits anywhere on the cliff profile, had a relatively small mean magnitude compared to cliff top changes and were more widely distributed alongshore. However, the similar alongshore averaged. cumulative cliff top and net bulk cliff face end-point retreat (14 and 19 cm, respectively) suggest that mean cumulative cliff top retreat can potentially be a viable surrogate for mean net cumulative cliff-wide erosion (and vice versa) over relatively short time periods. Cliff face erosion occurred repeatedly at some locations, confirming the presence of seacliff erosion hot-spots during the study period. (C) 2009 Elsevier B.V. All rights reserved.

Young, AP, Guza RT, Flick RE, O'Reilly WC, Gutierrez R.  2009.  Rain, waves, and short-term evolution of composite seacliffs in southern California. Marine Geology. 267:1-7.   10.1016/j.margeo.2009.08.008   AbstractWebsite

A four-year time series of nine airborne LiDAR surveys were used to assess the roles of wave attack and rainfall on the erosion of 42 km of southern California seacliffs. Nine continuous seacliff sections, separated by coastal lagoon mouths, all show maximum seacliff erosion in the rainiest time period (when wave energy was not particularly elevated), and in most sections the squared correlations between rainfall and erosion time series exceeded 0.8. Although rain and associated subaerial mechanisms such as groundwater seepage triggered most of the observed seacliff failures, wave attack accelerated seacliff erosion, with erosion rates of cliffs exposed to wave attack five times higher than at adjacent cliffs not exposed to waves. The results demonstrate the importance of both waves and rain in the erosion of southern California seacliffs and suggest that the combined influences of marine and subaerial processes accelerate the erosion rate through positive feedbacks. (C) 2009 Elsevier B.V. All rights reserved.

2010
Ewing, L, Flick RE, Synolakis CE.  2010.  A review of coastal community vulnerabilities toward resilience benefits from disaster reduction measures. Environmental Hazards-Human and Policy Dimensions. 9:222-232.   10.3763/ehaz.2010.0050   AbstractWebsite

The coast has always been an area of significant hazards. In situations of community self-sufficiency, consequences of coastal hazards might be isolated to regions directly affected by the hazard. But, in the current global economy, fewer and fewer communities are isolated; damage to one location frequently has consequences around the globe and coastal community resilience can have broad-reaching benefits. Hazard responses for the built coastal environment have typically been resistance: constructing stronger buildings, enhancing natural barriers or creating artificial barriers. These approaches to hazard reduction through coastal engineering and shoreline defence efforts have been crucial to sustained coastal development. However, as coastal forces continue or magnify and resources become scarcer, resistance alone may be less effective or even unsustainable, and interest in resilience has grown. Resilience is a community's ability either to absorb destructive forces without loss of service or function, or to recover quickly from disasters. Community resilience encompasses multiple elements, ranging from governance to structural design, risk knowledge, prevention, warning systems and recovery. This paper focuses on hazards of coastal communities, and provides a review of some recent engineering efforts to improve the resilience elements of risk knowledge and disaster warnings for coastal disaster reduction.

Young, AP, Olsen MJ, Driscoll N, Flick RE, Gutierrez R, Guza RT, Johnstone E, Kuester F.  2010.  Comparison of Airborne and Terrestrial Lidar Estimates of Seacliff Erosion in Southern California. Photogrammetric Engineering and Remote Sensing. 76:421-427. AbstractWebsite

Seacliff changes evaluated using both terrestrial and airborne lidar are compared along a 400 m length of coast in Del Mar, California. The many large slides occurring during the rainy, six-month study period (September 2004 to April 2005) were captured by both systems, and the alongshore variation of cliff face volume changes estimated with the airborne and terrestrial systems are strongly correlated (r(2) = 0.95). However, relatively small changes in the cliff face are reliably detected only with the more accurate terrestrial lidar, and the total eroded volume estimated with the terrestrial system was 30 percent larger than the corresponding airborne estimate. Although relatively small cliff changes are not detected, the airborne system can rapidly survey long cliff lengths and provides coverage on the cliff top and beach at the cliff base.

Young, AP, Raymond JH, Sorenson J, Johnstone EA, Driscoll NW, Flick RE, Guza RT.  2010.  Coarse Sediment Yields from Seacliff Erosion in the Oceanside Littoral Cell. Journal of Coastal Research. 26:580-585.   10.2112/08-1179.1   AbstractWebsite

The coarse sediment fraction of geologic formations exposed in 42 km of southern California seacliffs in the Oceanside Littoral Cell was estimated using more than 400 samples An impulse laser, oblique photographs, and coastal maps were used to define thickness and alongshore extent of the geologic units exposed in the seacliffs The coarse sediment (defined as diameter > 0 06 mm) fraction in each geologic unit was estimated by sieving About 80% of the exposed cliff face is coarse and can contribute to beach building Finer cliff sediments are transported offshore by waves and currents Although there are some differences, the observed 80% coarse fraction is generally consistent with previous estimates based on an order of magnitude fewer samples Coastal development has largely eliminated about 40% of seacliffs in the Oceanside Littoral Cell as potential beach sand sources For the remaining seacliffs, 1 cm of average cliff retreat yields 10,000 m(3) of potential beach-building material

2011
Young, AP, Guza RT, O'Reilly WC, Flick RE, Gutierrez R.  2011.  Short-term retreat statistics of a slowly eroding coastal cliff. Natural Hazards and Earth System Sciences. 11:205-217.   10.5194/nhess-11-205-2011   AbstractWebsite

The frequency, spatial distribution, and dimensions of coastal cliff retreats, a basic statistic underlying cliff top hazard assessment, are presented for 7.1 km of unprotected and slowly retreating coastal cliffs near Point Loma in San Diego, California, US. Using 8 airborne light detection and ranging (lidar) surveys collected over 5.5 years, 130 individual cliff edge failures (primarily rockfalls, block falls, and topples) were detected. Footprint areas varied from 3 to 268 m(2), maximum landward retreats from 0.8 to 10 m, and alongshore lengths from 2 to 68 m. The failures with the largest landward retreats were also relatively long, and 13% of the slides accounted for 50% of the lost cliff area over the study period. On this short (5.5 years) time scale, "no change" was the most common observation (84% of the cliff edge). Probability distributions of non-zero cliff retreat during each time interval usually had a single peak between 1 and 2.5 m. Intervals with high mean retreat had elevated numbers of failure in all class sizes, and also contained the largest individual retreats. Small and medium slides tended to reoccur preferentially (relative to randomly) near previous small and medium slides, forming short-term hot spots, while large slides were less likely to reoccur near previous large slides. Cumulative distributions of landslide failure parameters (area, mean retreat, maximum retreat, and length) follow an inverse power-law for medium to large size events, similar to previously reported distributions of coastal and inland landsliding.