Ocean Beach Research Articles

Numerical experiments on breaking waves on contrasting beaches using a two-phase flow approach

A mechanistic understanding of beach environments needs to account for interactions of oceanic forcing and beach materials, in particular the role of waves on the evolution of the beach profile. A fully coupled two-phase flow model was used to simulate nearshore fluid-sediment turbulent flow in the cross-shore direction. It includes the Reynolds-Averaged Navier–Stokes equations and turbulent stress closures for each phase, and accounts for inter-granular stresses. The model has previously been validated using laboratory-scale data, so the results are likely more reliable for that scale. It was used to simulate wave breaking and the ensuing hydrodynamics and sediment transport processes in the surf/swash zones. Numerical experiments were conducted to investigate the effects of varying beach and wave characteristics (e.g., beach slope, sediment grain size, wave periods and heights) on the foreshore profile changes. Spilling and plunging breakers occur on dissipative and intermediate beaches, respectively. The impact of these wave/beach types on nearshore zone hydrodynamics and beach morphology was determined. The numerical results showed that turbulent kinetic energy, sediment concentrations and transport rate are greater on intermediate than on dissipative beaches. The results confirmed that wave energy, beach grain size and bed slope are main factors for sediment transport and beach morphodynamics. The location of the maximum sediment transport is near the breaking point for both beach types. Coarse- and fine-sand beaches differ significantly in their erosive characteristics (e.g., foreshore profile evolutions are erosive and accretionary on the fine and coarse sand beaches, respectively). In addition, a new parameter (based on main driving factors) is proposed that can characterize the sediment transport in the surf and swash zones. The results are consistent with existing physical observations, suggesting that the two-phase flow model is suitable for the simulation of hyper-concentrated mixed water-sediment flows in the nearshore. The model thus has potential as a useful tool for investigating interactions between nearshore hydrodynamics and beach morphology.

Beach recreation impacts benthic invertebrates on ocean-exposed sandy shores

Ocean beaches are prime recreational assets and are becoming increasingly urbanised: more beaches today front metropolitan regions, are mechanically cleaned, and are used for recreation by increasing numbers of residents and tourists. This ‘urbanisation’ of beaches presents complex management and conservation challenges, including the accurate determination of ecological effects caused by human beach use. Here we tested whether spatial variation in recreational beach use translates into ecological changes in the benthic invertebrate assemblages inhabiting the intertidal zone in Eastern Australia. Detected faunal changes were consistent with an interpretation of trampling impacts on the lower part of the beach: here, reductions in key ecological measures were significant in terms of total abundance (−72% to −44% lower than control areas), and species richness (−55% to −5%), resulting in significant shifts in community structure. Conversely, upper-shore assemblages were structurally similar between trampling treatments. Because benthic invertebrates are structurally and functionally important in beach ecosystems (e.g. nutrient cycling, trophic links), human impacts from recreation are likely to propagate beyond the macrobenthos and hence require mitigation. Conservation measures for beaches are challenging in urban settings. However, a practicable approach to systematic conservation planning for urban beaches that recognises the social and political reality of beaches having a prime role as recreational assets while maximising environmental outcomes via spatial zoning and visitor management is not unrealistic.

Synthesis Study of an Erosion Hot Spot, Ocean Beach, California

Abstract Barnard, P.L.; Hansen, J.E., and Erikson, L.H., 2012. Synthesis study of an erosion hot spot, Ocean Beach, California (USA). A synthesis of multiple coastal morphodynamic research efforts is presented to identify the processes responsible for persistent erosion along a 1-km segment of 7-km-long Ocean Beach in San Francisco, California. The beach is situated adjacent to a major tidal inlet and in the shadow of the ebb-tidal delta at the mouth of San Francisco Bay. Ocean Beach is exposed to a high-energy wave climate and significant alongshore variability in forcing introduced by varying nearshore bathymetry, tidal forcing, and beach morphology (e.g., beach variably backed by seawall, dunes, and bluffs). In addition, significant regional anthropogenic factors have influenced sediment supply and tidal current strength. A variety of techniques were employed to investigate the erosion at Ocean Beach, including historical shoreline and bathymetric analysis, monthly beach topographic surveys, nearshore ...

GEOGRAFIA URBANA QUE FAZEMOS

This paper presents an overview about the state-of-art of studies on oceanic sandy beaches from the State of São Paulo, within the Coastal Geomorphology point of view. These studies embrace a sort of thematic issues, in special: beach profile monitoring, textural (grain size) parameters, heavy minerals assemblage and related indices, beach sedimentary dynamics, beach sedimentary budget, sediment transport patterns (morpho-textural and wave modeling methods), long term shoreline changes (remote sensing analyses), morphodynamic classification, coastal erosion and associated risk, and environmental sensitivity for oil spill. Some results related to morphodynamic classification, grain size parameters behavior, longshore drift patterns, and coastal erosion (indicators, causes and risk assessment) are showed for the seven morphodynamic sectors that this coast is comprised.

PRAIAS ARENOSAS OCEÂNICAS DO ESTADO DE SÃO PAULO (BRASIL): SÍNTESE DOS CONHECIMENTOS SOBRE MORFODINÂMICA, SEDIMENTOLOGIA, TRANSPORTE COSTEIRO E EROSÃO COSTEIRA

This paper presents an overview about the state-of-art of studies on oceanic sandy beaches from the State of São Paulo, within the Coastal Geomorphology point of view. These studies embrace a sort of thematic issues, in special: beach profile monitoring, textural (grain size) parameters, heavy minerals assemblage and related indices, beach sedimentary dynamics, beach sedimentary budget, sediment transport patterns (morpho-textural and wave modeling methods), long term shoreline changes (remote sensing analyses), morphodynamic classification, coastal erosion and associated risk, and environmental sensitivity for oil spill. Some results related to morphodynamic classification, grain size parameters behavior, longshore drift patterns, and coastal erosion (indicators, causes and risk assessment) are showed for the seven morphodynamic sectors that this coast is comprised.

Predictive distribution modeling of the sandy-beach supralittoral amphipod Atlantorchestoidea brasiliensis along a macroscale estuarine gradient

Exposed marine beaches are physically rigorous habitats in which macrofaunal patterns have been well correlated with physical factors. In this context, the habitat safety hypothesis (HSH) predicts an increase in abundance of supralittoral species from dissipative to reflective conditions in microtidal oceanic beaches. However, the HSH has not been adequately tested in estuarine sandy beaches. Here, we build a predictive model based on the supralittoral talitrid amphipod Atlantorchestoidea brasiliensis that allowed us to test the HSH along a macroscale estuarine gradient. Fifteen Uruguayan sandy beaches along a salinity gradient (from 0.1 to 34.3) generated by the Río de la Plata estuary (SW Atlantic Ocean) were sampled over a two-year period. A conditional two-step procedure using a General Additive Model (GAM) was performed in order to model A. brasiliensis occurrence (1st-step) and abundance (2nd-step), based on a comprehensive set of environmental variables [salinity, water temperature, beach face slope (BFS), mean grain size, wave height and sand compaction, moisture and organic matter]. Each GAM was parameterized using generalized linear models (GLMs). An external validation procedure was used. Data were divided randomly into training (75%) and test (25%) sets. The 1st-step GAM/GLM retained 5 physical descriptors in the model (decreasing order of importance): wave height, salinity, BFS, organic matter and sand compaction. The 2nd-step GAM/GLM retained 6 physical descriptors: sand compaction, water content, salinity, wave height, water temperature and organic matter. The predictive ability of these models and the resulted combined model, as well as their external validity, was highly significant and supported the predictions of the HSH. However, the highest and lowest abundances were observed, respectively, on reflective and dissipative beaches in the outer estuary; i.e., the predictions based on the HSH did not account for the high levels of abundance observed on these beaches compared with oceanic ones. Therefore, the HSH was expanded to include microtidal estuarine beaches.

Onshore Bar Migration in a Fetch/Limited Strong Wind Bay

WONG, H and STEPHENSON, W., 2011. Onshore Bar Migration in a Fetch/Limited Strong Wing Bay. In: Micallef, A. (ed.), MCRR3-2010 Conference Proceedings, Journal of Coastal Research, Special Issue, No. 61, pp. 458-469. Grosseto, Tuscany, Italy, ISSN 0749-0208.This paper investigates bar migration in a fetch limited strong wind bay (Seaford Beach SE Australia). Onshore bar migration on open ocean beaches is dependant on long period swell wave and occurs during low energy conditions. However, in a fetch limited environment such waves are absent and most studies suggest that during low energy conditions the beach remains in an arrested state (Jackson et al. 2002). This paper spans a three month study period (15th March – 8th June 2008). Measurement of near shore morphology and wind data were collected. The two bars at Seaford behaved very differently; both onshore and offshore migration was detected during the three recorded storm events. The paper found that, firstly, wave breaking was incomplete in the middle bar during event 1 — the inner bar migrated offshore. Secondly wave breaking in the middle bar was almost complete during event 2 and the inner bar migrated onshore. Thirdly when wave breaking was complete in the middle bar during event 3 — the inner bar remained arrested on some profiles but bar height increased on others. The wave steepness threshold for onshore migration of the inner bar was parameterized s 0.041 – 0.042. Beach sediment modeling in fetch limited strong wind bays remains understudied. Our results should help to improve the predictive capability of beach sediment budgets in fetch limited strong wind bays.

Resonances in an Evolving Hole in the Swash Zone

Water oscillations observed in a 10-m-diameter, 2-m-deep hole excavated on the foreshore just above the low-tide line on an ocean beach were consistent with theory. When swashes first filled the initially circular hole on the rising tide, the dominant mode observed in the cross-shore velocity was consistent with a zero-order Bessel function solution (sloshing back and forth). As the tide rose and swash trans- ported sediment, the hole's diameter decreased, the water depth inside the hole remained approximately constant, and the frequency of the sloshing mode increased according to theory. About 1 h after the swashes first reached the hole it had evolved from a closed circle to a semicircle, open to the ocean. When the hole was nearly semicircular, the observed cross-shore velocity had two spectral peaks, one associated with the sloshing of a closed circle, the other associated with a quarter-wavelength mode in an open semicircle, both consistent with theory. As the hole evolved further toward a fully semicircular shape, the circular sloshing mode decreased, while the quarter-wavelength mode became dominant. DOI: 10.1061/(ASCE)WW.1943-5460.0000136. © 2012 American Society of Civil Engineers. CE Database subject headings: Nearshore; Resonance; Standing waves; Water waves; Sediment transport; Wave runup. Author keywords: Nearshore; Resonances; Standing waves; Water waves; Sediment transport.

Experimental study of dune vegetation impact and control on leatherback sea turtle Dermochelys coriacea nests

The leatherback sea turtle Dermochelys coriacea is a Critically Endangered species that nests on oceanic beaches. Natural disturbance cycles of erosion and accretion maintain nest- ing habitat on these beaches by controlling dune vegetation and sand quality. The nesting beach at Sandy Point National Wildlife Refuge in St. Croix, US Virgin Islands, is designated 'critical habi- tat' for leatherback turtles by the US Fish and Wildlife Service. It harbors the largest nesting pop- ulation (>800 females) in the USA. It is an important rookery for Atlantic leatherback recovery efforts. For the past 30 yr, the beach has been continuously monitored and managed in order to increase hatchling recruitment and conservation. Our study highlights how a multiyear change in the natural disturbance cycle has affected dune plant growth and leatherback production at this beach. Reduced summer erosion relaxed natural control of Ipomoea pes-caprae, a native dune plant, allowing its seaward spread to cover >75% of the nesting beach. This spread of vegetation led to both direct and indirect interactions between nesting leatherbacks and I. pes-caprae. Because the beach is managed in order to protect leatherback nests, a dune vegetation control plan was needed. We measured the effects of 3 vegetation management options on nest success: herbicide treatment, aboveground mechanical removal, and undisturbed vegetation. These treat- ments were compared to nest success at a non-vegetated control site. We found that the spread of I. pes-caprae reduced nesting habitat and nest productivity. Aboveground vegetation treatment did not control root growth into nests. We discuss possible vegetation management strategies to improve leatherback nesting habitat quality and maximize nest productivity while minimizing anthropogenic disturbance to the natural beach dynamics.

Persistent organic pollutants in plastic marine debris found on beaches in San Diego, California

Plastic debris were collected from eight beaches around San Diego County, California. Debris collected include: pre-production pellets and post-consumer plastics including fragments, polystyrene (PS) foam, and rubber. A total of n = 2453 pieces were collected ranging from <5 mm to 50 mm in size. The plastic pieces were separated by type, location, and appearance and analyzed for polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and its breakdown products, and chlordanes. PAH concentrations ranged from 30 ng g −1 to 1900 ng g −1, PCBs from non-detect to 47 ng g −1, chlordanes from 1.8 ng g −1 to 60 ng g −1, and DDTs from non-detect to 76 ng g −1. Consistently higher PAH concentrations found in PS foam samples (300–1900 ng g −1) led us to examine unexposed PS foam packaging materials and PS virgin pellets. Unexposed PS foam contained higher concentrations of PAHs (240–1700 ng g −1) than PS virgin pellets (12–15 ng g −1), suggesting that PAHs may be produced during manufacturing. Temporal trends of debris were investigated at one site, Ocean Beach, where storm events and beach maintenance were found to be important variables influencing debris present at a given time.

Scale- and resolution-invariance of suitable geographic range for shorebird metapopulations

The habitat suitability of a shorebird metapopulation is studied as a function of the scale (extent) and resolution (grain-size) of the environmental covariates with a maximum entropy species distribution model ( MaxEnt) for integration with climate change simulations. For this study, the species considered is the Snowy Plover ( Charadrius a. nivosus), which is a threatened shorebird whose geographic range spans the northwest and southwestern gulf coasts of Florida. The habitat suitability is analyzed at different resolutions by coarsening the classes of the ecogeographical variables with two algorithms: (i) preserving the information of each class at the finer resolution (conservative algorithm); and (ii) considering the most frequent class (majority algorithm). Ultimately, the most suitable habitat is found to be estuarine and ocean beaches made of alkaline medium and fine white sand and silt. The model fit to the observed species distribution decreases with the resolution. Due to the loss of the physical habitat (barrier islands) resulting from the coarsening operation, there is a threshold below which the model fails to predict the species distribution. As a result, the suitable geographic range is resolution-invariant below a resolution-threshold that is determined by the geomorphological features of the landscape rather than by biological constrains. This result holds for both the coarsening algorithms, however the conservative algorithm allows a continuous mapping of the habitat suitability. The suitable geographical range is found to be scale- and resolution-invariant, yet the habitat suitability at-a-point appears scale-dependent due to the strong heterogeneity of the ecogeographical variables. The scale- and resolution-invariance of the suitable geographic range appears a universal result for metapopulations of different species. This is important for reducing the uncertainty of population viability models that are based also on the choice of extent and grain-size of habitat predictions. However, attention must be paid in choosing a resolution that is not too large in order to correctly represent the physical habitat of the species. This implies a potential increase in the effectiveness of conservation campaigns to face the threats of climate change, such as sea-level rise for the Snowy Plover.

Impact of erosion and accretion on the distribution of enterococci in beach sands

Bacterial pathogens in coastal sediments may pose a health risk to users of beaches. Although recent work shows that beach sands harbor both indicator bacteria and potential pathogens, it is neither known how deep within beach sands the organisms may persist nor if they may be exposed during natural physical processes. In this study, sand cores of approximately 100 cm depth were collected at three sites across the beach face in Kitty Hawk, North Carolina, before, during, and after large waves from an offshore hurricane. The presence of DNA from the fecal indicator bacterium Enterococci was detected in subsamples at different depths within the cores by PCR amplification. Erosion and accretion of beach sand at the three sites were also determined for each sampling day. The results indicate that ocean beach sands with persisting enterococci signals could be exposed and redistributed when wind, waves, and currents cause beach erosion or accretion.

Radon as an indicator of limited cross-shelf mixing of submarine groundwater discharge along an open ocean beach in the South Atlantic Bight during observed hypoxia

Hypoxic conditions (dissolved oxygen (DO)<2 mg l −1) have been documented in the nearshore coastal waters of Long Bay, South Carolina, United States of America, during summer months over the past several years. Hypoxia was documented in August 2009 in the nearshore (<500 m offshore) for ten consecutive days and four days in September 2009 corresponding with spring tides. This study measured radon activities of shallow beachface groundwater and nearshore bottom waters to estimate mixing rates and submarine groundwater discharge (SGD) in the nearshore waters of central Long Bay. Statistical analyses demonstrate significant correlations between high bottom water radon activities, low DO, and cooler bottom water temperatures during hypoxic conditions. Elevated radon activities during hypoxia were significantly influenced by upwelling favorable conditions which severely limited cross-shelf mixing. Model results indicate mixing of nearshore and offshore waters was limited by up to 93% (range: 43–100%) relative to non-hypoxic conditions. Data suggests previously overlooked natural phenomena including limited cross-shelf mixing and SGD can significantly influence nearshore water quality.

Pressure-gradient-driven nearshore circulation on a beach influenced by a large inlet-tidal shoal system

[1] The nearshore circulation induced by a focused pattern of surface gravity waves is studied at a beach adjacent to a major inlet with a large ebb tidal shoal. Using a coupled wave and wave-averaged nearshore circulation model, it is found that the nearshore circulation is significantly affected by the heterogeneous wave patterns caused by wave refraction over the ebb tidal shoal. The model is used to predict waves and currents during field experiments conducted near the mouth of San Francisco Bay and nearby Ocean Beach. The field measurements indicate strong spatial variations in current magnitude and direction and in wave height and direction along Ocean Beach and across the ebb tidal shoal. Numerical simulations suggest that wave refraction over the ebb tidal shoal causes wave focusing toward a narrow region at Ocean Beach. Due to the resulting spatial variation in nearshore wave height, wave-induced setup exhibits a strong alongshore nonuniformity, resulting in a dramatic change in the pressure field compared to a simulation with only tidal forcing. The analysis of momentum balances inside the surf zone shows that, under wave conditions with intensive wave focusing, the alongshore pressure gradient associated with alongshore nonuniform wave setup can be a dominant force driving circulation, inducing heterogeneous alongshore currents. Pressure-gradient-forced alongshore currents can exhibit flow reversals and flow convergence or divergence, in contrast to the uniform alongshore currents typically caused by tides or homogeneous waves.

Equilibrium shoreline response of a high wave energy beach

[1] Four years of beach elevation surveys at Ocean Beach, San Francisco, California, are used to extend an existing equilibrium shoreline change model, previously calibrated with fine sand and moderate energy waves, to medium sand and higher-energy waves. The shoreline, characterized as the cross-shore location of the mean high water contour, varied seasonally by between 30 and 60 m, depending on the alongshore location. The equilibrium shoreline change model relates the rate of horizontal shoreline displacement to the hourly wave energy E and the wave energy disequilibrium, the difference between E and the equilibrium wave energy that would cause no change in the present shoreline location. Values for the model shoreline response coefficients are tuned to fit the observations in 500 m alongshore segments and averaged over segments where the model has good skill and the estimated effects of neglected alongshore sediment transport are relatively small. Using these representative response coefficients for 0.3 mm sand from Ocean Beach and driving the model with much lower-energy winter waves observed at San Onofre Beach (also 0.3 mm sand) in southern California, qualitatively reproduces the small seasonal shoreline fluctuations at San Onofre. This consistency suggests that the shoreline model response coefficients depend on grain size and may be constant, and thus transportable, between sites with similar grain size and different wave climates. The calibrated model response coefficients predict that for equal fluctuations in wave energy, changes in shoreline location on a medium-grained (0.3 mm) beach are much smaller than on a previously studied fine-grained (0.2 mm) beach.

Geoarchaeology of the Nehalem spit: Redistribution of beeswax galleon wreck debris by Cascadia earthquake and tsunami (∼A.D. 1700), Oregon, USA

AbstractA coincidence of the Beeswax galleon shipwreck (ca. A.D. 1650–1700) and the last Cascadia earthquake tsunami and coastal subsidence at ∼A.D. 1700 redistributed and buried wreck artifacts on the Nehalem Bay spit, Oregon, USA. Ground‐penetrating radar profiles (∼7 km total distance), sand auger probes, trenches, cutbank exposures (29 in number), and surface cobble counts (49 sites) were collected from the Nehalem spit (∼5 km2 area). The field data demonstrate (1) the latest prehistoric integrity of the spit, (2) tsunami spit overtopping, and (3) coseismic beach retreat since the A.D. 1700 great earthquake in the Cascadia subduction zone. Wreck debris was (1) initially scattered along the spit ocean beaches, (2) washed over the spit by nearfield tsunami (6–8 m elevation), and (3) remobilized in beach strandlines by catastrophic beach retreat. Historic recovery of the spit (150 m beach progradation) and modern foredune accretion (&gt;5 m depth) have buried both the retreat scarp strandlines and associated wreck artifacts. The recent onshore sand transport might re‐expose heavy ship remains in the offshore area if the wreck grounded in shallow water (&lt;20 m water depth of closure). © 2011 Wiley Periodicals, Inc.

APPLICATION OF COASTAL STORM IMPULSE (COSI) PARAMETER TO PREDICT COASTAL EROSION

A new coastal storm-strength parameter, the Coastal Storm Impulse (COSI) parameter, was introduced at the ICCE 2006 (San Diego) and further discussed at the ICCE 2008 (Hamburg). COSI is based on the conservation of linear, horizontal momentum to combine storm surge, wave dynamics, and currents over the storm duration. Both tropical storms (hurricanes) and extra-tropical storms (northeasters) can produce similar COSI parameters that range from 0.69*10^6 N-m/hr to 49.72*10^6 n-m/hr with lognormal distribution. Potential implications of such a storm classification system include the evaluation of coastal structures and coastal infrastructure, as well as providing a universal storm strength indicator that is directly tied to coastal physical parameters and not limited to wind speed. This paper explores the application of COSI to predict coastal erosion along the sub-aerial ocean beach in Duck, North Carolina on the east coast of the United States. Data for the 10-year study period (1994 to 2003) has been analyzed to produce 249 storms for study of coastal erosion. When profile response to coastal storms was assessed through a pre- and post-storm volumetric determination, mixed results showing both erosion and accretion were observed. The paper also explores the possible explanations and implications of these findings.

Abundance of bottlenose dolphins, Tursiops truncatus (Cetacea: Delphinidae), inhabiting the Patos Lagoon estuary, southern Brazil: implications for conservation

A new mark-recapture abundance estimate and a photographic census were carried out to investigate the possible decline in the abundance of the bottlenose dolphins, Tursiops truncatus (Montagu, 1821), in the Patos Lagoon estuary due to the high levels of bycatch mortality which occurred between 2002 and 2006 in oceanic coastal areas close to the estuary. Fourteen systematic boat surveys were conducted between August and early December 2005 to photo-identify the bottlenose dolphins. The estimated number of animals, with long-lasting marks, in the population obtained from Chapman's and Mth models were 51 (95% CI = 49-53) and 52 (95% CI = 51-60), respectively. Taking into account the proportion of dolphins with long-lasting marks in the population, the total estimated population size ranged between 84 (95% CI = 76-93) and 86 (95% CI = 78-95) individuals, respectively, which was very similar to the 84 individuals revealed by the population census. Our results did not differ from the abundance estimate carried out in 1998, prior to the high fishing-related mortality event, suggesting that the population is stable. Plausible argument to explain the stability of the population is that some carcasses found on the oceanic coastal beaches near Patos Lagoon estuary come from animals that do not belong to the estuary community. Future studies should investigate fine-scale habitat partition between estuarine and adjacent coastal dolphins. If the existence of different communities living in close proximity (estuarine and coastal areas near to the estuary) is confirmed, a new abundance estimate is needed to access the conservation status of bottlenose dolphins in this region.

FIELD MEASUREMENT OF AEOLIAN SAND FLUX USING CERAMIC SAND FLUX SENSOR UD-101 AT A SAND DUNE

This study conducted field observations in terms of the number of blown sand impacts and wind velocity at an open ocean beach in Japan, in order to investigate characteristics of the aeolian sand transport flux over a sand dune slope. Charnock constant of a roughness length equation calculated from wind velocity data had a larger value over the slope compared to over a flat. Furthermore, the aeolian flux over the slope tended to be larger than that over the flat. Characteristics of the Charnock constant and the aeolian flux over the flat and the slope were demonstrated from the field measurements.

Anthropogenic influences on shoreline and nearshore evolution in the San Francisco Bay coastal system

Analysis of four historical bathymetric surveys over a 132-year period has revealed significant changes to the morphology of the San Francisco Bar, an ebb-tidal delta at the mouth of San Francisco Bay estuary. From 1873 to 2005 the San Francisco Bar vertically-eroded an average of 80 cm over a 125 km 2 area, which equates to a total volume loss of 100 ± 52 million m 3 of fine- to coarse-grained sand. Comparison of the surveys indicates the entire ebb-tidal delta contracted radially, with the crest moving landward an average of 1 km. Long-term erosion of the ebb-tidal delta is hypothesized to be due to a reduction in the tidal prism of San Francisco Bay and a decrease in coastal sediment supply, both as a result of anthropogenic activities. Prior research indicates that the tidal prism of the estuary was reduced by 9% from filling, diking, and sedimentation. Compilation of historical records dating back to 1900 reveals that a minimum of 200 million m 3 of sediment has been permanently removed from the San Francisco Bay coastal system through dredging, aggregate mining, and borrow pit mining. Of this total, ∼54 million m 3 of sand-sized or coarser sediment was removed from central San Francisco Bay. With grain sizes comparable to the ebb-tidal delta, and its direct connection to the bay mouth, removal of sediments from central San Francisco Bay may limit the sand supply to the delta and open coast beaches. SWAN wave modeling illustrates that changes to the morphology of the San Francisco Bar have altered the alongshore wave energy distribution at adjacent Ocean Beach, and thus may be a significant factor in a persistent beach erosion ‘hot spot’ occurring in the area. Shoreline change analyses show that the sandy shoreline in the shadow of the ebb-tidal delta experienced long-term (1850s/1890s to 2002) and short-term (1960s/1980s to 2002) accretion while the adjacent sandy shoreline exposed to open-ocean waves experienced long-term and short-term erosion. Therefore, the recently observed accelerating rates of bay sediment removal, ebb-tidal delta erosion, and open coast beach erosion are all correlated temporally.