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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.

Ludka, BC, Guza RT, O'Reilly WC, Merrifield MA, Flick RE, Bak AS, Hesser T, Bucciarelli R, Olfe C, Woodward B, Boyd W, Smith K, Okihiro M, Grenzeback R, Parry L, Boyd G.  2019.  Sixteen years of bathymetry and waves at San Diego beaches. Scientific Data. 6   10.1038/s41597-019-0167-6   AbstractWebsite

Sustained, quantitative observations of nearshore waves and sand levels are essential for testing beach evolution models, but comprehensive datasets are relatively rare. We document beach profiles and concurrent waves monitored at three southern California beaches during 2001-2016. The beaches include offshore reefs, lagoon mouths, hard substrates, and cobble and sandy (medium-grained) sediments. The data span two energetic El Nino winters and four beach nourishments. Quarterly surveys of 165 total cross-shore transects (all sites) at 100 m alongshore spacing were made from the backbeach to 8 m depth. Monthly surveys of the subaerial beach were obtained at alongshore-oriented transects. The resulting dataset consists of (1) raw sand elevation data, (2) gridded elevations, (3) interpolated elevation maps with error estimates, (4) beach widths, subaerial and total sand volumes, (5) locations of hard substrate and beach nourishments, (6) water levels from a NOAA tide gauge (7) wave conditions from a buoy-driven regional wave model, and (8) time periods and reaches with alongshore uniform bathymetry, suitable for testing 1-dimensional beach profile change models.

Rasmussen, L, Bromirski PD, Miller AJ, Arcas D, Flick RE, Hendershott MC.  2015.  Source location impact on relative tsunami strength along the US West Coast. Journal of Geophysical Research-Oceans. 120:4945-4961.   10.1002/2015jc010718   AbstractWebsite

Tsunami propagation simulations are used to identify which tsunami source locations would produce the highest amplitude waves on approach to key population centers along the U.S. West Coast. The reasons for preferential influence of certain remote excitation sites are explored by examining model time sequences of tsunami wave patterns emanating from the source. Distant bathymetric features in the West and Central Pacific can redirect tsunami energy into narrow paths with anomalously large wave height that have disproportionate impact on small areas of coastline. The source region generating the waves can be as little as 100 km along a subduction zone, resulting in distinct source-target pairs with sharply amplified wave energy at the target. Tsunami spectral ratios examined for transects near the source, after crossing the West Pacific, and on approach to the coast illustrate how prominent bathymetric features alter wave spectral distributions, and relate to both the timing and magnitude of waves approaching shore. To contextualize the potential impact of tsunamis from high-amplitude source-target pairs, the source characteristics of major historical earthquakes and tsunamis in 1960, 1964, and 2011 are used to generate comparable events originating at the highest-amplitude source locations for each coastal target. This creates a type of ``worst-case scenario,'' a replicate of each region's historically largest earthquake positioned at the fault segment that would produce the most incoming tsunami energy at each target port. An amplification factor provides a measure of how the incoming wave height from the worst-case source compares to the historical event.

Young, AP, Flick RE, Gallien TW, Giddings SN, Guza RT, Harvey M, Lenain L, Ludka BC, Melville WK, O'Reilly WC.  2018.  Southern California coastal response to the 2015-2016 El Niño. Journal of Geophysical Research Earth Surface. 123   10.1029/2018JF004771  
Bromirski, PD, Flick RE, Miller AJ.  2017.  Storm surge along the Pacific coast of North America. Journal of Geophysical Research-Oceans. 122:441-457.   10.1002/2016jc012178   AbstractWebsite

Storm surge is an important factor that contributes to coastal flooding and erosion. Storm surge magnitude along eastern North Pacific coasts results primarily from low sea level pressure (SLP). Thus, coastal regions where high surge occurs identify the dominant locations where intense storms make landfall, controlled by storm track across the North Pacific. Here storm surge variability along the Pacific coast of North America is characterized by positive nontide residuals at a network of tide gauge stations from southern California to Alaska. The magnitudes of mean and extreme storm surge generally increase from south to north, with typically high amplitude surge north of Cape Mendocino and lower surge to the south. Correlation of mode 1 nontide principal component (PC1) during winter months (December-February) with anomalous SLP over the northeast Pacific indicates that the dominant storm landfall region is along the Cascadia/British Columbia coast. Although empirical orthogonal function spatial patterns show substantial interannual variability, similar correlation patterns of nontide PC1 over the 1948-1975 and 1983-2014 epochs with anomalous SLP suggest that, when considering decadal-scale time periods, storm surge and associated tracks have generally not changed appreciably since 1948. Nontide PC1 is well correlated with PC1 of both anomalous SLP and modeled wave height near the tide gauge stations, reflecting the interrelationship between storms, surge, and waves. Weaker surge south of Cape Mendocino during the 2015-2016 El Nino compared with 1982-1983 may result from changes in Hadley circulation. Importantly from a coastal impacts perspective, extreme storm surge events are often accompanied by high waves.

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.

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   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.