longshore wave variability along non straight coastlines abstract the present paper demonstrates the role of wave direction and shoreline alignment on wave attenuation along a non straight coastline a numerical model was calibrated against measured data at six locations along a non straight coastline and a hybrid method composed by wave case selection simulation and nearshore time series reconstruction was applied to transfer 20 years of wave time series from offshore to nearshore the results highlight the importance of the orientation of the coastline to different degrees of wave exposure to the wave attenuation process the varying orientation of the coastline at each of the six sites resulted in non uniform wave attenuation alongshore under different wave directions the extreme wave conditions at each of the sites were also shown to vary significantly along the coast e g 18 alongshore at 17 m australian height datum ahd and as much as 34 from offshore 70 m ahd to nearshore 17 m ahd the results presented here reinforce the importance of assessing variations in wave attenuation along the coast as opposed to simply using the closest offshore wave dataset available improved understanding of nearshore wave attenuation along non straight coastlines aids in better informing future coastal protection and management strategies

facies mosaics across the persian gulf and around antigua stochastic and deterministic products of shallow water sediment accumulation abstract among broadly different types of sedimentary successions those that accumulate in nearshore settings are perhaps unique in that a very wide range of rock types recurs with high frequency over relatively short stratigraphic intervals this vertical lithofacies heterogeneity suggests that deposition of any sedimentary unit at any site was short lived that many different sediment types existed within a complex mosaic over the depositional surface and that this facies montage repeatedly moved across surfaces of accumulation in response to eustatic sedimentologic and or tectonic forcing data on numbers and thicknesses of lithofacies units from several dozen such sequences define the size frequency distribution expected if horizons of lithologic change occur randomly within sedimentary successions walther s law suggests that the amount of vertical lithologic heterogeneity manifest in a sedimentary sequence should reflect the degree of lateral heterogeneity in sediment composition that existed across depositional surfaces if so this repetition should also be manifest in sizes and areal distributions of sediment patches constituting the depositional mosaic in order to examine size frequency relations of sediment bodies across surfaces of sediment accumulation we tabulated numbers and areal extents of lithotopes across two rather dissimilar settings across the persian gulf and around the caribbean island of antigua although compositions and lateral extents of different sediment types exhibit broad lateral variation across interior to margin transects in either area lithotope abundances and areal extents define frequency distributions that are in excellent agreement with those anticipated for a facies mosaic of elements whose mean linear widths constitute an exponential frequency distribution these are the size frequency distributions one would expect if mosaic element boundaries occur randomly across regions of sediment accumulation and suggest that distributions of lithotope areas from holocene surfaces are directly analogous to lithofacies thickness frequencies from ancient successions in addition to the fact that both of the size frequency distributions attest to the importance of stochastic processes during sediment deposition they also afford numerical descriptors of abundances and areal extents of holocene lithosomes that can then be used as controlling parameters in computational models of sediment accumulation importantly results derived from such simulations are based not on inference of water depth varying in response to change in subsidence sea level and rate of sediment accumulation but on statistical attributes intrinsic to modern and ancient marginal marine successions

controls on links between geomorphical and surface sedimentological variability aitutaki and maupiti atolls south pacific ocean abstract isolated carbonate platforms and atolls occur throughout the geologic record from archean to present although the roles of sea level change tectonics and sediment supply on large scale changes in stratigraphical architecture of these systems are relatively well understood the details of the nature and controls on sedimentological variability between and within individual geomorphic elements on platforms and atolls are less well constrained the purposes of this study are 1 to describe compare and contrast geomorphological and sedimentological characteristics of surficial holocene sediments from two south pacific atolls aitutaki and maupiti representing different physical and chemical oceanographic settings and 2 to explore possible causes for sedimentological heterogeneity by contrasting the patterns with those present on other platforms and regions both atolls include annular shelf edge reef systems with a red algal rim and reef flat flanked lagoonward by reef sand aprons up to 1 500 m wide these aprons consist of moderately sorted coarse sand and gravel with an abundance of halimeda coral and red algal fragments broadly sediments become finer and better rounded away from margins water depths increase abruptly inboard of these reef sand aprons into platform interiors with depths up to 25 m maupiti and 9 m aitutaki although patch reefs dot these lagoons sediment is commonly poorly sorted with bimodal and polymodal size distributions and includes a mix of whole and fragmented skeletal grains peloids and ooids mud and fine sand are abundant up to 80 on maupiti 85 on aitutaki the occurrence of peloids fine ooid sand and oolitically laminated skeletal grains on maupiti atoll as previously documented on aitutaki is consistent with interpretations of the impact of elevated regional ocean total alkalinity ta and ph levels in this part of the pacific on these wave dominated atolls open ocean waves impinging on the platform margins generate currents that transport sediment from the reef across the sand apron and towards the platform interior unlike the tide dominated platforms of the bahamas however weak tides preclude strong daily agitation and circulation so ooids do not grow large and mud and fine sand transported into the atoll interiors is sequestered there in the interiors both sediment produced in situ and fine allochthonous sediment are more influenced by biological processes than by physical transport processes so bioturbated muddy sand is most common collectively the comparative analysis provides actualistic process based conceptual models for the nature and controls on variability of shelf margin reef and reef apron systems and platform interiors within and among atolls

tidal correction of topex poseidon altimetry for seasonal sea surface elevation and current determination off the pacific coast of canada altimetry from the topex poseidon satellite is analyzed for the waters off british columbia canada tides are removed using harmonic constants from two coastal and two global models and the accuracy of this detiding is assessed by using these same models and one digital filter to remove the tide from the time series of three representative coastal tide gauges it is demonstrated that inaccurate m2 s2 and k1 tide removal from topex poseidon altimetry can introduce systematic biases to the calculation of seasonally averaged fields average summer and winter sea surface heights are calculated from the detided altimetry and estimates of their accuracy nearshore are computed using concurrent time series from 11 tide gauges finally these seasonal elevations are blended with those from the 11 tide gauges and the associated surface currents are calculated using a diagnostic finite element model these currents are compared with those calculated from historical conductivity and temperature versus depth measurements and those measured by historical near surface current meters

open ocean validation of topex poseidon sea level in the western equatorial pacific during the verification phase of the topex poseidon radar altimeter mission a rigorous open ocean validation experiment was conducted in the western equatorial pacific ocean from august september 1992 to february march 1993 two tropical ocean and global atmosphere toga tropical atmosphere ocean moorings at 2os 156 e 1739 m depth and 2os 164 4 e 4400 m depth were outfitted with additional temperature salinity and pressure sensors to measure precisely the dynamic height from the surface to the bottom at 5 min intervals directly beneath two topex poseidon crossovers bottom pressure gauges and inverted echo sounders were deployed as well a predeployment design study using full depth conductivity temperature depth casts subsequently confirmed by postdeployment analyses indicated this suite of instruments was capable of measuring sea surface height fluctuations to within 1 2 cm the validation experiment also benefited from the comprehensive set of ocean atmosphere measurements that were made in the region during the toga coupled ocean atmosphere response experiment intensive observation period of november 1992 to february 1993 the surface relative to bottom dynamic height fluctuations observed in situ during the 6 7 month experiment had a standard deviation of 5 cm with excursions of order t 15 cm energetic steric sea level variability was found to exist on short timescales of order hours to a few days most notably the quasi permanence of strong semidiurnal internal tides such internal tides were noted to induce changes in surface dynamic height with a standard deviation of 2 dynamic centimeters at the shallower of the two sites 2 s 156 e a possible nonlinear rectification of the internal tide was observed occasionally to change the dynamic height by as much as 30 cm over less than an hour on timescales longer than the 10 day repeat of the topewposeidon satellite the low frequency fluctuations of dynamic height were related to interannual variations corresponding to the 1991 1993 ei nino southern oscillation to the seasonal cycle and to intraseasonal variations associated with the 40 to 60 day oscillations of the equatorial zonal wind field instantaneous comparisons between the 1 s topex poseidon altimeter retrievals and the 5 min dynamic height were performed with regard to several tide models the barotropic tide measured in situ european centre for medium range weather forecasts surface air pressure and the surface air pressure measured in situ depending on the choice of altimeter and of the environmental corrections applied to the altimeter data the rms differences between the satellite and the in situ measurements of sea level were as low as 3 3 cm at 2os 156 e and 3 7 cm at 2os 164 4 e when additional satellite data in the general vicinity of the mooring are included and after the use of a 30 day low pass filter the satellite and in situ data were found to be highly correlated with correlation coefficients of about 0 95 and rms differences around 1 8 cm

the use of landsat imagery to map fluvial sediment discharge into coastal waters abstract the sediment discharge of the river yare via breydon water estuary into the north sea has been studied sixty samples were taken the average of each sample in the band tm1 was used to estimate the concentrations of suspended solids sixty samples were used to extract information from the reflective bands tm1 tm4 the spatial distribution of suspended solids as well as the spatial and vertical extent of different turbidity levels were then detected estimated and mapped based on this information the water circulation pattern at the mouth of river yare was identified and mapped the influence of wind velocity and direction as well as the tidal current conditions prior to and during the image time on turbidity and water circulation patterns were examined the tidal influence was found to be the most significant factor in shaping and guiding water circulation near the mouth of river yare

seasonal response of the sea surface to the wind in the equatorial atlantic from february 1983 through september 1984 18 inverted echo sounder deployments yielded time series from 10 locations as part of the seasonal response of the equatorial atlantic sequal program using historical and in situ data the sounders travel time data are interpreted as dynamic height 0 relative to 500 dbar and then related to representations of the synoptic wind field the seasonal variations of the zonal pressure gradient along the equator and the height of the dynamic ridge along 3 n relative to the equator and 9 n are described the pressure gradient between 10 w and 34 w has a minimum each april and a maximum each july its value ranges between 1 4 not significantly different from zero and 8 3 10 5 dyn g 1 during the observational period the zonal pressure gradient is correlated with zonal wind stress from an in situ wind sensor at midfetch and a 10 day lag time is indicated the north equatorial countercurrent trough attains a maximum in the late boreal summer and fall and a minimum in the spring it ranges from 39 to 8 dyn cm deep at 38 5 w and from 18 to 1 dyn cm at 28 w a two layer model calculation using monthly mean winds derived by servain et al 1986 for the appropriate time period generally reproduces the observed seasonal variation along the two meridians and the large zonal variation between them tracking the individual terms month by month illustrates the rate of the sverdrup adjustment to the local wind stress with surface elevation rising as fast as 10 cm per month

decadal scale coastal cliff retreat in southern and central california abstract airborne lidar data collected in 1998 and 2009 2010 were used to measure coastal cliff erosion and retreat between the mexico california border and bodega head california cliff erosion was detected along 44 of the 595 km of shoreline evaluated while the remaining cliffs were relatively stable the mean cliff top retreat rate was 0 12 m yr while mean retreat averaged over the entire cliff face was 0 04 m yr the maximum cliff top and face retreat rates were 4 2 and 3 8 m yr respectively historical 1930s to 1998 and recent retreat rates were significantly inversely correlated for areas with large historical or recent cliff retreat such that locations with elevated historical retreat had low levels of recent retreat and locations with elevated recent retreat were preceded by low rates of historical retreat the strength of this inverse correlation increased with cliff change magnitudes up to r2 of 0 91 for cliff top retreat rates 2 9 m yr mean recent retreat rates were 52 83 lower than mean historical retreat rates although beaches can protect cliffs against wave driven erosion cliffs fronted by beaches retreated 49 more than cliffs without beaches on average unarmored cliff faces retreated 0 05 m yr between 1998 and 2009 2010 about three times faster than artificially armored cliffs alongshore metrics of wave cliff impact precipitation and cliff hardness were generally not well correlated with recent cliff changes a cliff hazard metric is used to detect cliff steepening and areas prone to future cliff top failures

hindcast of the wave conditions along the west iberian coast this paper describes the development of a wave prediction system for the west iberian coast the implemented wave prediction system is based on two state of the art spectral wave models wam for the ocean area and swan for the nearshore however because of its extended geographical space the swan model will include some generation effects in the coarse swan simulations complemented by wave transformation effects near the coast the system was validated by means of extended hindcast runs in various regions belonging to the continental portuguese coastal environment which were compared with buoy data focusing on the extreme energetic events and both direct comparisons and statistical results are presented

complex decapod burrows and ecological relationships in modern and pleistocene intertidal carbonate environments san salvador island bahamas abstract burrowing by thalassinidean shrimp in modern tropical shallow subtidal to intertidal carbonate environments is widespread and a powerful agent of bioturbation particularly within sandy substrates deep and intense burrowing by callianassids commonly occurs along the intertidal margins of hypersaline lagoons throughout the bahamas such as pigeon creek on san salvador island where the sediments of extensive sand flats are thoroughly bioturbated by glypturus acanthochirus in addition to dominating the deep tier infauna g acanthochirus is a true ecosystem engineer and its prodigious burrowing activity results in a highly mounded topography on sand flats individual sediment cones commonly coalesce with time to form large composite mounds with surfaces stabilized by the development of microbial mats this unique biogenetically produced topography sets the stage for colonization by shallow tier burrowers particularly the upogebiid shrimp upogebia vasquezi and several species of fiddler crabs burrow systems of u vasquezi are distinctive and complex they typically consist of a pair of u shaped burrows in close proximity or criss crossing with knobs or short tunnels at their bases the entire u burrow pair is lined by a thick externally pelleted wall inside burrow diameters range from 0 2 to 1 cm and burrow depths are 10 15 cm in contrast to the much deeper callianassid burrows these complex upogebiid burrows also occur as trace fossils in late pleistocene lagoon margin facies of the grotto beach formation on san salvador initially reported as fragmentary burrow fills whole burrow systems virtually identical to the modern upogebiid burrows recently have been found at several localities these fossil burrows are most abundant in beds lying immediately below a terra rossa paleosol that marks the late pleistocene holocene stratigraphic boundary and the beds likely were deposited with sea level stillstand and regression associated with the onset of wisconsinan glaciation with their high potential for preservation these complex upogebiid trace fossils may prove useful as both paleoenvironmental and sea level position indicators in the study of quaternary carbonate sequences throughout the bahamas and other geologically similar regions

patterns of sediment composition of jamaican fringing reef facies recent carbonate sediments from jamaican north coast fringing reefs were collected along three parallel traverses in the vicinity of discovery bay each traverse extended from near shore across the back reef reef crest and fore reef to a depth of 75 m relative abundances of the biotic constituents vary between sites reflecting general patterns of reef community composition the sediment is dominated by highly comminuted coral fragments 27 1 to 63 1 plates of the calcareous green alga halimedu 0 4 to 38 7 coralline algae 4 7 to 16 2 and the encrusting foraminiferan homotremu rubrum 0 7 to 9 5 with lesser amounts of other taxonomic groups non encrusting foraminifera 1 3 5 5 molluscs 1 4 7 0 echinoderms 0 9 5 0 coral fragments coralline algae and particles of homotrema rubrum dominate the sediments of the shallow portions of the fore reef 5 15 m whereas plates of hulimedu are most abundant in sediments from the back reef and deeper portions of the fore reef 2 24 m q mode cluster analysis using sediment constituent data resulted in the delineation of four reef biofacies over the depth range of this study 1 75 m

a simple model for interannual sandbar behavior time and length scales of beach variability have been quantified using 16 years of beach surveys sampled at the army corps of engineers field research facility located on the u s atlantic coast between 50 and 90 of the bathymetric variability at this site was explained by alongshore uniform response over the approximately 1 km alongshore span of the surveys although the incident wave height variance was dominated by frequencies at or higher than 1 cycle yr more than 80 of the bathymetric variance at all cross shore locations was explained by frequencies 1 cycle yr interannual cycles consisting of sandbar formation migration and decay contributed to the low frequency variability the observed behavior can be explained by a simple heuristic model the model assumes that bars migrate toward a wave height dependent equilibrium position this position was shown to coincide with the wave breakpoint additionally the rate of bar response is taken to be variable and was empirically determined to be proportional to the wave height cubed the net effect of a variable response rate is to shift the expected long term mean sandbar position offshore toward the equilibrium position associated with the largest waves the model explained up to 80 of the observed bar position time series variance and up to 70 of the variance of bar crest velocity time series which were extracted from three different sandbars characteristic bar response times related to the inverse of the response rate were found to be long relative to the characteristic timescale of the forcing 1 year in our case as a result transient response i e bar position far from equilibrium tended to persist for many cycles of the forcing transient bar behavior appears in the observations when bars formed near the shoreline or when outer bars decayed and inner bars faced a changed wave climate while the present model is able to explain the evolution of these transients it does not contain a mechanism for their introduction

forecasting and hindcasting waves with the swan model in the southern california bight abstract the naval research laboratory created a wave forecasting system in support of the nearshore canyon experiment ncex field program the outer nest of this prediction system encompassed the southern california bight this forecasting system is described in this paper with analysis of results via comparison to the extensive buoy network in the region there are a number of potential errors two of which are poor resolution of islands in the bight which have a strong impact on nearshore wave climate and the use of the stationary assumption for computations these two problems have straightforward solutions but the solutions are computationally expensive so an operational user must carefully consider their cost the authors study the impact of these two types of error relative to other errors such as error in boundary forcing using several hindcasts performed after the completion of ncex it is found that with buoy observations as ground truth the stationary assumption leads to a modest increase in root mean square error this is due to relatively poor prediction of the timing of swell arrivals and local sea growth decay the model results are found to be sensitive to the resolution of islands however coarse resolution does not incur an appreciable penalty in terms of error statistics computed via comparison to buoy observations suggesting that other errors dominate inaccuracy in representation of the local atmospheric forcing likely has a significant impact on wave model error perhaps most importantly the accuracy of directional distribution of wave energy at the open ocean boundaries appears to be a critical limitation on the accuracy of the model data comparisons inside the bight

aeolian sediment transport on a beach thresholds intermittency and high frequency variability abstract during a field experiment designed to measure wind flow and sediment transport over the beach and foredune at greenwich dunes prince edward island national park measurements were made on october 11 2004 during a storm with wind speeds ranging from 4 ms 1 to over 20 ms 1 this paper examines thresholds of sand movement intermittency and the relationship between fluctuating winds and transport intensity based on high frequency measurements of wind speed and saltation wind speed was measured at four points across the beach profile using cup anemometers set at a height of 0 6 m the anemometers were co located with saltation probes set at a height of 0 02 m that measure the impacts of saltating sand grains the instruments were sampled at 1 hz during runs of 1 or 2 h over an eight hour period sand transport was highly intermittent early in the day when winds were only slightly above threshold and became more continuous towards the upper beach because of increasing fetch distance and decreasing surface moisture despite more continuous transport and increasing wind speed through the day a zone of highly intermittent transport migrated landward across the beach as water levels rose due to storm surge examination of three thresholds related to measures of wind speed the maximum wind speed without transport u tmax minimum wind speed with transport u tmin and the intermittency threshold u t showed that none provide a consistently robust measure of the threshold although they all provide some insight into conditions controlling entrainment while graphs of instantaneous saltation intensity crudely mimic the pattern of fluctuating wind speed statistical correlations over periods of 2 10 min were generally poor r 2

estimating the fluvial sediment input to the coastal sediment budget a case study of ghana knowledge of fluvial sediment supply to the coastal sediment budget is important for the assessment of the impacts on coastal stability such knowledge is valuable for designing coastal engineering schemes and the development of shoreline management planning policies it also facilitates understanding of the connection between rivers in the hinterland and adjoining coastal systems ghana s coast has many fluvial sediment sources and this paper provides the first quantitative assessments of their contributions to the coastal sediment budget the methods use largely existing data and attempt to cover all of ghana s significant coastal rivers initially work was hindered by insufficient direct measured data however the problem was overcome by the application of a regression approach which provides an estimated sediment yield for non gauged rivers based on data from gauged rivers with similar characteristics the regression approach was effective because a regional coherence in behaviour was determined between those rivers where direct measured data were available the results of the assessment revealed that ghana s coast is dissected by many south draining rivers stream and lagoons these rivers streams and lagoons supply significant amounts of sediment to coastal lowlands and therefore contribute importantly to beaches anthropogenic impoundment of fluvial sediment especially the akosombo dam on the volta river has reduced the total fluvial sediment input to the coast from about 71 106 m3 a before 1964 pre akosombo dam to about 7 106 m3 a at present post akosombo dam this sharp reduction threatened the stability of the east coast and prompted an expensive 83 million defence scheme to be implemented to protect 8 4 km long coastline at keta sections of ghana s coast are closely connected to the hinterland through the fluvial sediment input from local rivers therefore development in the hinterland that alters the fluvial sediment input from those local rivers could have significant effects on the coast there is the need therefore to ensure that catchment management plans and coastal management plans are integrated or interconnected

analyzing spatial patterns in modern carbonate sand bodies from great bahama bank abstract three carbonate sand bodies on great bahama bank which show a range of depositional facies patterns typifying modern deposits as well as their ancient counterparts are quantitatively interrogated to broaden our perspective of the types of information that can be derived from studies of modern environments rimming the southern end of tongue of the ocean toto is the broadest expanse of high energy sands found in the bahamas characterized by narrow sandbars separated by wide deep channels and a lack of islands a variation of the tidal bar motif with broader and more irregular sandbars relatively narrow channels and few small islands occurs at the northern end of exuma sound schooners sands associated with tidal channels and the numerous islands of the exumas chain along the western edge of exuma sound occur primarily as flood tidal deltas the geometry of sandbars that inhabit the three sand bodies is quantified using landsat remote sensing and assembled along with optically derived bathymetric surfaces into a gis this database is quantitatively examined using a suite of morphometric tools to compare and contrast geometric character of sandbars within and between the three sand bodies considered are properties such as the size shape complexity distribution orientation and topography of the individual sandbars profiles and spatial analysis tools enable sandbar and channel spacing position relative to the platform margin connectedness separation distances and density to be characterized as has been previously reported for reef dominated environments certain aspects of the geometry of the three systems are found to behave in a systematic and hence predictable manner though important mathematical differences are revealed between the scaling of reefal landscapes and the grainy geobodies considered by this study because the three sand bodies are disparate in their overall extent and depositional settings e g orientation prevalence of islands this predictable behavior has the potential to impart considerable insight to the characterization of grainstone systems

poisson processes of carbonate accumulation on paleozoic and holocene platforms abstract cambro ordovician carbonate lithofacies units in the elbrook and conococheague formations exposed at wytheville virginia as well as those in many other phanerozoic peritidal sequences exhibit exponential thickness frequency distributions that is occurrence frequency decreases exponentially with linear increase in unit thickness such distributions are characteristic of waiting times between independent poisson events this relative frequency of spaces of different size between horizons of lithologic change is what one would expect if the horizons were distributed randomly throughout carbonate successions abundances of different lithologies both as net stratigraphic thickness and as number of occurrences also decreases exponentially among successively rare sediment types with each lithology being about 60 as plentiful as the next more abundant rock type relations between net thickness and number of occurrences for each facies define a linear trend coincident with a mean thickness for all wytheville units of 0 48 m a relation indicating that thickness distribution is independent of facies type similar relations are apparent for the horizontal extent of carbonate sediment bodies from the holocene florida bahama platform areal extents of individual facies units lithotopes are described by a frequency distribution in agreement with that anticipated for a population of equidimensional facies elements whose diameter distribution follows an exponential frequency distribution although regional gradients in sediment texture and composition are also apparent along most transects from platform margin to interior such frequency distributions indicate that lateral extents of individual sediment reflect a largely stochastic distribution of facies boundaries across this holocene surface lithotope abundances also yield trends of exponentially decreasing dominance among successively subordinate facies with each being about 70 as extensive the next more abundant sediment type relations between areas and abundances for all lithotopes define a covariant trend corresponding to a mean area of 2 2 103 km2 for all florida bahamas lithotopes we consider several numerical models of stochastic carbonate accumulation although not demonstrably unique scenarios incorporating the sequential superposition of randomly placed coniform lithotopes result in thickness and area frequency distributions that are the same as those observed in ancient and modern platform deposits such simulations of poisson processes of sediment accumulation are in general agreement with stochastic models of lithologic heterogeneity that have been more widely applied to petroleum reservoirs and groundwater aquifers to the as yet unknown degree that peritidal lithofacies area and thickness are correlated data from paleozoic and holocene platforms suggest that carbonate units should exhibit length height ratios of approximately 105 given the decimeter scale over which facies are designated in most paleozoic peritidal successions these relations predict mean lateral extents on the order of several tens of kilometers a value in general agreement with the few data that exist on spatial continuities of peritidal lithotopes in paleozoic carbonate sequences

modeling dune response to an east coast low coastal dunes can act as a method of soft coastal protection against inundation and direct impact of waves during storms if they are substantially large enough in volume to withstand erosion without breaching however the time evolution of sand dunes under direct wave impact is not well understood and many available models require site specific calibration and have had limited verification at field scales here we test three models of varying complexity in their ability to predict both dry beach erosion volumes and dune to a retreat for an east coast low storm event that occurred on the gold coast australia the process based model xbeach which models the entire profile was able to reproduce both dune toe retreat and dry beach volume however was sensitive to calibration parameters the two parametric models that only modeled erosion above the initial dune toe position were capable of accurately predicting dune toe retreat however under estimated dry beach erosion volumes with no calibration the parametric model proposed by palmsten and holman 2012 produced the smallest errors of dune toe retreat with mean error in final dune position of 6 6 m or 18 of the total measured dune retreat with minimal calibration estimated absolute error in average dune toe retreat was less than 13 of observed retreat for all three models

coral reef sedimentation on rodrigues and the western indian ocean and its impact on the carbon cycle coral reefs in the southwest indian ocean cover an area of ca 18530 km2 compared with a global reef area of nearly 300000 km2 these regions are important as fishing grounds tourist attractions and as a significant component of the global carbon cycle the mass of calcium carbonate stored within holocene neritic sediments is a number that we are only now beginning to quantify with any confidence in stark contrast to the mass and sedimentation rates associated with pelagic calcium carbonate which have been relatively well defined for decades we report new data that demonstrate that the reefs at rodrigues like those at reunion and mauritius only reached a mature state reached sea level by 2 3 ka thousands of years later than most of the reefs in the australasian region yet field observations show that the large lagoon at rodrigues is already completely full of carbonate detritus typical lagoon depth less than 1 m at low spring tide the presence of aeolian dunes at rodrigues indicates periodic exposure of past lagoons throughout the pleistocene the absence of elevated pleistocene reef deposits on the island indicates that the island has not been uplifted most holocene reefs are between 15 and 20 m in thickness and those in the southwest indian ocean appear to be consistent with this observation we support the view that the co2 flux associated with coral reef growth acts as a climate change amplifier during deglaciation adding co2 to a warming world southwest indian ocean reefs could have added 7 10 to this global flux during the holocene

two dimensional time dependent hurricane overwash and erosion modeling at santa rosa island abstract a 2dh numerical model which is capable of computing nearshore circulation and morphodynamics including dune erosion breaching and overwash is used to simulate overwash caused by hurricane ivan 2004 on a barrier island the model is forced using parametric wave and surge time series based on field data and large scale numerical model results the model predicted beach face and dune erosion reasonably well as well as the development of washover fans furthermore the model demonstrated considerable quantitative skill upwards of 66 of variance explained maximum bias 0 21 m in hindcasting the post storm shape and elevation of the subaerial barrier island when a sheet flow sediment transport limiter was applied the prediction skill ranged between 0 66 and 0 77 in a series of sensitivity tests in which several hydraulic forcing parameters were varied the sensitivity studies showed that the variations in the incident wave height and wave period affected the entire simulated island morphology while variations in the surge level gradient between the ocean and back barrier bay affected the amount of deposition on the back barrier and in the back barrier bay the model sensitivity to the sheet flow sediment transport limiter which served as a proxy for unknown factors controlling the resistance to erosion was significantly greater than the sensitivity to the hydraulic forcing parameters if no limiter was applied the simulated morphological response of the barrier island was an order of magnitude greater than the measured morphological response

the significant role of sediment bio retexturing within a contemporary carbonate platform system implications for carbonate microfacies development abstract assessments of carbonate platform reef lagoon sediments and benthic habitats around rodrigues island south west indian ocean have been undertaken in order to examine carbonate sediment textural properties and the controls on texturally defined sediment fabrics reef lagoon sediments sampled from across the expansive 8 km wide carbonate dominated windward platform principally comprise poorly sorted medium to coarse grained bioclastic sands composed of a low diversity of grain constituents predominantly non geniculate coralline algal bioclasts despite a marked homogeneity in sediment compositional and grain size properties eight distinct sediment textural groups can be identified that form a heterogeneous mosaic across the contemporary reef lagoon system only along the narrow outer platform margins reef crest sand apron and outermost lagoon environments do we observe consistent predictable transitions in sediment textural groups where physical processes are the primary drivers of selective sediment transport and sorting in contrast across the main expanse of the lagoon the sediment substrates are characterised by an irregular mosaic of texturally defined sediment groups formed primarily as a function of sediment bio retexturing the burrowing activities of alpheid and callianassid shrimps are particularly important in this respect and impart a distinctly unique textural fabric to the upper sediment horizons in the environments in which the respective organisms occur the consequence of this is that at the platform system scale individual texturally defined sediment groups are relatively poor indicators of prevailing hydrodynamic regimes or of local sediment production reflecting more the biological action of organisms inhabiting the substrate this has important implications for understanding the development of carbonate sediment fabrics in the context of palaeoenvironmental reconstructions and for interpreting a key diagnostic criteria of carbonate microfacies

shoreline dynamics and beach rotation of artificial embayed beaches abstract artificially embayed beaches are an increasingly common environment in retreating and urban coasts the study of embayed beaches usually focuses on the concept of some equilibrium configuration of the shoreline caused by the wave approach and the location of protection structures but detailed studies of their shoreline dynamics are scarce the study reported herein monitored the shoreline dynamics of three artificial embayed beaches in barcelona city during a three year period using an argus video system to examine the behaviour of the emerged beach in order to assess the main factors affecting the shoreline and to analyze the processes causing beach rotation at different time scales the length and degree of protection of the three beaches were different and so were their morphological behaviours two of the beaches presented a general retreating trend with rapid abrupt displacements of the shoreline caused by oblique wave incidence during storm events and to the effects of beach nourishment after nourishment slower changes at the beaches determined beach evolution which was also influenced by the formation of long lasting megacusps the third beach the most protected one showed an accretionary trend no formation of megacusps and episodes of beach rotation related to the gradual recovery of the beach after storm events it is concluded that factors controlling the evolution of barcelona city beaches are associated with both natural processes and man induced actions resulting in a more complex pattern than would be expected for small embayed beaches beach rotation appears as a key process for understanding the morphodynamics of embayed beaches it occurs as a fast response to storms but also as a medium term adaptation of the shoreline configuration to morphological changes in the beach or to the recovery of a more stable orientation after storm events and man made changes in the beach orientation resulting from nourishment or sand relocation

bio retexturing early diagenetic fabric modifications in outer ramp settings a case study from the oligo miocene of the central mediterranean abstract bioturbation is ubiquitous in cenozoic outer ramp settings the oligo miocene ramp carbonate sequences of se sicily and the maltese islands provide specific examples to illustrate the effects of sediment retexturing by burrowers and provide significant conclusions which must be taken into account by sedimentologists when interpreting palacoenvironments thalassinoidean burrow systems may penetrate several metres into the underlying beds with evidence of concentrated activity at selected levels the general intra bed process of this crustacean dominated bioturbation is well documented however the effects when several beds are involved can be dramatic 1 a buried homogeneous wackestone beds can be depleted in lime mud by gallery excavation the dumping of this mud at the sediment surface leads to lime mud enrichment of the contemporary accumulating layer and might be a major factor in the development of the tabular outer ramp bedforms 2 b vertical reworking of unlithified sediment between beds both upwards and down is capable of homogenising two distinctly dissimilar lithologies producing a third which in no way reflects the surface processes of the depositional setting 3 c bioturbation often continues during incipient near seafloor lithification this produces random lateral variations in lithology within single beds the degree of lateral dissimilarity is proportional to the intensity longevity of the bioturbation episode bio retexturing destroys primary depositional fabrics and masks inorganic process related structures it can be as effective a remodelling agent as tidal energy it can texturally remodel areas of high primary permeability into irregular interconnected zones of low permeability as the outer ramp provides a potential fluid migration route from basin to shallow water clearly bio retexturing must exert a major influence on longer term formation wide diagenetic processes

estimating sea level slope on the equator abstract a new method for diagnosing the zonal gradient of sea level on the equator from in situ data is proposed and validated using satellite altimetry a no turbulent stress level boundary condition in the pacific equatorial undercurrent core constrains the average flux of zonal momentum above uniquely determining the zonal sea level gradient the method is applied to simultaneous data from tropical atmosphere ocean array moorings spanning 154 165 e and adcp moorings in the vicinity of 157 5 e from 6 october 1992 to 21 december 1993 an independent estimate of sea level slope is obtained from contemporaneous daily equatorial crossings of the first european remote sensing satellite ers 1 and ocean topography experiment topex poseidon altimeters the slope is also estimated by assuming no pressure gradient at 500 m depth when accelerations and the pressure gradient can be estimated at the same location 5 day averages of the no stress level estimate explain 59 of the variance in the altimetry dat

an interannual study of the atlantic north equatorial countercurrent abstract beginning in 1983 the dynamic height difference at the sea surface defining the countercurrent trough at 38 w was continuously observed by inverted echo sounders at 3 n and 9 n for six years and ten months the amplitude of the average annual signal for that time period was 36 cm and the range of the interannual variability was 25 cm thus the annual signal dominates as expected but the interannual variability is of comparable magnitude two years 1983 and 1987 are noted as years of sharp increase in the interannual signal periods immediately following el nino events in the pacific from a derived relationship for geostrophic volume transport it is estimated that every year the north equatorial countercurrent attained a transport of 20 sv 106 m3 s 1 for at least one month while in the cited years it sustained this value for over half the year the output of an unbounded reduced gravity model forced by monthly averaged wind stress is compared to the observations the model can be t

low frequency changes of sediment volume on the beachface at warilla beach new south wales 1975 1985 abstract characteristic patterns of shore parallel and shore normal movements of sediment on a sandy beach are described in this study the sediment movements are apparent as low frequency variations in the volume of sediment stored above mean low water spring tide mlwst level on warilla beach n s w they were determined by an empirical orthogonal function eof analysis of beach profile records the profiles were surveyed from eighteen stations along a 2 km long beach at least monthly generally fortnightly for over 10 years from july 1975 until august 1985 results from the eof analysis confirm and substantially extend an earlier study of warilla beach when the first 5 years of the beach survey record was examined the importance of low frequency beachface change identified in the earlier shorter study was confirmed from the extended data set zones of maximum variability linked with rip current activity are consistent in both studies and similar patterns of alongshore sediment movement in the swash zone were determined from both analyses the principal differences between the two sets of results highlight beachface responses to processes operating in different time scales amplitude spectra from time series describing the characteristic modes of sediment movement along and across the beachface have periodicities of 2 0 1 7 and 1 0 years beach changes with periods close to 3 years are apparent in the record but cannot be resolved by standard spectral analysis techniques each period is associated with a characteristic pattern of beach change the triennial and 1 7 year cycles with alongshore sediment transport and the biennial cycle with onshore offshore sediment exchange eigenvectors from the eof analysis identify the characteristic patterns of beach change from survey data specified to highlight the shore parallel sediment movement along 0 5 m deep horizontal segments of beach and shore normal sediment movement along the beach profiles in the analysis of shore parallel variation in beach profile configuration the fundamental eigenvectors explain between 70 and 80 of beachface variance in each instance and different patterns of sediment movement were identified for each horizontal slice on the upper part of the beachface all eigenvectors identified a zone of low variability along the shoreline skirting a rockwall below berm crest in the swash and intertidal zones of the beach and away from the rockwall the northern half of the beach was highly variable second mode eigenvectors cellular flux modes explain a further 5 to 14 of the variance and describe sediment exchanges between discrete zones in each horizontal segment of the beachface zones of greatest variability occurred landward of places where rip currents frequently develop conversely zones of low variability are coincident with areas of beachface in the lee of places where inshore bars frequently form analysis of sediment movement along each profile is consistent with the beach changes described the fundamental eigenvectors account for 91 to 99 of the variance on each profile they describe an onshore offshore movement of sediment through the intertidal zone of the beach

the impact of sea level rise and climate change on inshore wave climate a case study for east anglia uk in coastal areas offshore wave propagation towards the shore is influenced by water depth variations due to sea bed bathymetry tides and surges considering implications of climate change both on atmospheric forcing and sea level rise a simple methodology involving numerical modelling is implemented to compute inshore waves from 1960 to 2099 simulations take into account five scenarios of linear sea level rise and one climatic scenario for storm surges and offshore waves the methodology is applied to the east anglia coast uk extreme event analysis is performed to estimate climate change implication on inshore waves and the occurrence of extreme events it is shown for this coastal region that wave statistics are sensitive to the trend in sea level rise and that the climate change scenario leads to a significant increase of extreme wave heights in the northern part of the domain for nearshore points the increase of the mean sea level alters not only extreme wave heights but also the frequency of occurrence of extreme wave conditions

internal tides observed at 2 s 156 e by in situ and topex poseidon data during the coupled ocean atmosphere response experiment coare during the enhanced monitoring phase of the coupled ocean atmosphere experiment coare semidiurnal baroclinic tides were observed at 2 s 156 e 1739 m depth the tropical atmosphere ocean tao mooring outfitted with additional sensors from surface to bottom provides an interesting tool for describing the internal tides m2 s2 and n2 baroclinic components were detected explaining 59 of the semidiurnal variance on surface dynamic height at the semidiurnal frequency vertical displacements of isopycnals highly variable in time can reach 30 m and are mostly a combination of the m2 s2 and n2 internal waves the two first baroclinic modes explain 70 of the variance in vertical displacement m2 and s2 internal waves have different vertical structure m2 resembles the first baroclinic mode and s2 resembles the second baroclinic mode the m2 and s2 internal waves projected on their respective baroclinic mode are highly related to the modeled barotropic tide two topex poseidon tracks cross over the mooring every 10 days and the internal wave signature can be expected in sea level along the tracks despite the weakness of the signal sea level spectra along both ascending and descending tracks show the existence of energy around the 250 km and the 120 km wavelength respectively which is in accordance with a first baroclinic wave propagating northeastward as suggested in previous studies from wavelet transform the baroclinic tide signatures on the ascending descending track are centered around 2 5 s 3 5 s with a 1 2 latitudinal extension respectively limited to the ontong java plateau we confirm the northeastward propagation of the baroclinic tides and their source could be a series of islands parallel to the kilinailau trench or the large sloping topography between the kilinailau trench and the ontong java plateau

shallowing upwards sedimentation in a coral reef lagoon great barrier reef of australia abstract sediments in the 5 25 m deep lagoon of davies reef a typical mid shelf reef in the central great barrier reef are described based on data gleaned from 19 soft sediment cores 75 mm diameter up to 7 5 m penetration 22 surface sediment samples and air lift surveys the holocene sediment pile which averages 5 10 m thickness is entirely skeletal in origin and has a very poorly sorted coral gravel rich base which grades up into poorly sorted muddy sands with infaunal molluscan gravel these muddy sands mainly derived from the reef rim as opposed to being produced in situ on the lagoon floor have been intensely bioturbated by callianassid shrimps leaving the infaunal molluscan gravel patchily distributed and the bivalves disarticulated and preferentially oriented sub hori ontally concave up there are no vestiges of primary depositional sedimentary structures such as bedding or cross bedding radiocarbon dating suggests that significant accumulation of muddy sand in the center of the lagoon did not begin until about 2 500 3 000 yr bp and that sediment accumulation rates have increased through time from an average of 1 4 mm yr between 2 400 and 640 yr bp to 3 4 mm yr over the past 640 years interpreting these data the coral gravel rich base to the sediment pile represents a period of prolific coral growth across the top of davies reef platform following flooding by the holocene transgression but before the outer reef rim caught up with sea level to form a lagoon when the rim did reach sea level about 3 000 4 000 yr bp it started to shed large qua tities of mud and sand grade sediment into the center of the reef platform and this combined with decreased water circulation led to the demise of coral growth in the newly formed lagoon as the area of reef rim at sea level increased so too did the supply of sediment to the lagoon which explains the observed increase in sediment accumulation rate through time using previously published data to aid speculation into the future development of the lagoon a shallowing upwards model for reef lagoon sedimentation is developed in this model a complete sequence consists of a fining upwards base reflecting the gradation from coral gravel up into bioturbated muddy sands and a coarsening upwards top reflecting a gradation from bioturbated muddy sands up into a zone of shallow subtidal co al rubble and patch reefs then inter and supratidal windward storm shingle ramparts and leeward sand cays

on the influence of wave directional spreading on the equilibrium planform of embayed beaches abstract equilibrium beach formulations are engineering tools for estimating a response of beaches in the long term they aim at defining the final orientation of a beach on a scale of years and thus they are used for evaluating the shoreline response due to human interference ports breakwaters protection works etc several equations can be found in the literature for obtaining the static equilibrium planform sep of headland bay beaches hbbs one such being the parabolic bay shape equation pbse the sep is strongly dependent on the location of the down coast control point po which is the downdrift limit from which the pbse is applicable the literature recommends the determination of the po point by means of the direction of the mean wave energy flux at the diffraction point however when this is applied to equilibrium embayed beaches in zones with a wide variability of wave climate directionality and or in cases where the diffraction point is located far from the equilibrium shoreline this approach is no longer valid and thus the resulting planform shape does not properly fit the sep for such conditions this paper investigates the methodology for locating the po point of the sep for such cases exploring the role of wave climate directional spreading employing 44 hbbs in spain and latin america it correlates the planform shape in the long term with the directional variability of the wave climate at the diffraction point additionally an extensive series of numerical simulations using a spectral wave model was carried out to model the combined effects of refraction diffraction in the lee of a breakwater defining the part affected by the coastal structure under different wave conditions the results clarify the importance of wave directional spreading in locating the po indicating that the wider the directional spreading the farther the po point on the shoreline moreover the farther the diffraction point from the coast the smaller the part of the beach affected by the coastal barrier a new formula has been derived to locate the down coast control point po of the parabolic part of the shoreline corresponding to the pbse as a function of the directional variance of the wave climate and the location of the diffraction point the model produced good results with r2 0 9117 and a rmse 1 8297 in estimating the location of the po point in various natural and man made beaches with different degrees of wave directionality

wind wave variability in a shallow tidal sea spectral modelling combined with neural network methods in this paper the wind wave variability in the tidal basins of the german wadden sea is modelled with combined numerical and neural network nn methods first the wave propagation and transformation in the study area are modelled with the state of the art third generation spectral wave model swan the ability of swan to accurately reproduce the phenomena of interest in nonstationary conditions governed by highly variable winds water levels and currents is shown by comparisons of the modelled and measured mean wave parameters at four stations the principal component analysis of the swan results is then used to reveal the dominating spatial patterns in the data and to reduce their dimensionality thus enabling an efficient and relatively straightforward nn modelling of mean wave parameters in the whole study area it is shown that the data produced with the approach developed in this work have statistical properties discrete probability distributions of the mean wave parameters etc very close to the properties of the data obtained with swan thus proving that this approach can be used as a reliable tool for wind wave simulation in coastal areas complementary to often computationally demanding spectral wave models

contemporary sedimentation in the cocos keeling islands indian ocean interpretation using settling velocity analysis abstract textural parameters of grain size distributions derived from sieve analysis and component analysis have been used to the exclusion of other methods to examine sedimentary processes in modern reef environments however because these methods do not reflect the hydraulic behaviour of bioclastic sediment this study uses settling velocity analysis accounting for grain size density and shape variability and component analysis of separated settling velocity fractions to describe and differentiate bioclastic deposits and infer transport pathways in the cocos keeling islands an indian ocean atoll principal component and cluster analysis of settling 251 samples and component 90 samples characteristics discriminated eight settling velocity and five component classes a derived settling velocity classification reflecting the hydraulic properties of the sediments describes a lagoonward gradient from those with fast settling characteristics on the outer reef flat to those with moderate settling character on sand aprons the active sediment transport system is constrained between these zones component analysis of bulk samples identifies two broad sediment types 1 those with reef derived components found throughout the active transport zone reef flat to sand aprons and 2 those characterised by greater proportions of gastropod and halimeda fragments which are produced and deposited in situ in the lagoon component analysis of settling fractions further resolves details of sediment movement in the active transport zone sediment is transported from the productive reef flat to passage entrances which form initial depositional environments slower settling material is selectively transported from the entrances through the passage conduits to passage exit environments these form the main depositional areas under mean energy conditions during moderate to high energy events sediment is flushed from the passage to sand apron zones with slower settling grains deposited in the deep lagoon sinks results show that settling velocity analysis and component analysis of settling fractions can resolve the nature of sediment transport patterns in reef environments at a much finer scale than studies in which analysis is based on grain size distributions

a simple equilibrium model for predicting shoreline change abstract this contribution describes the development calibration and verification of a 1 d behaviour orientated shoreline prediction model the model primarily encapsulates shoreline displacement forced by wave driven cross shore sediment transport hysteresis effects are shown to be important and are included in the model whereby present shoreline change is influenced by past hydro morpho dynamic conditions the potential magnitude of shoreline change increases with incident wave power and the degree of disequilibrium the latter disequilibrium term eq is expressed in terms of the time evolving equilibrium eq and instantaneous dimensionless fall velocities and dictates the direction of shoreline movement following wright et al 1985 the equilibrium fall velocity is defined as a function of the weighted antecedent conditions and is a proxy for the evolving beach state the decay rate of the weighting function used to compute eq is a model free parameter determined by calibration against measured data which physically reflects the degree of observed memory of the system the decay in amplitude of this weighting function with time is controlled by a memory decay term where the weighting reaches 10 1 and 0 1 at 2 and 3 days prior to the current calculation time the model is applied to two multi year 6 years data sets incorporating hourly wave and weekly shoreline measurements from two contrasting energetic sites in se australia the first is the relatively dissipative straight gold coast qld and the second is a more intermediate embayed beach at narrabeen nsw the model shows significant skill at hindcasting shoreline change at both sites predicting approximately 60 of the total shoreline variability the gold coast shoreline is dominated by a strong seasonal signal conversely at the narrabeen embayment shoreline variability and morphology is more dynamic responding at storm frequency evidence suggests that there is a strong coherence between the shoreline position and morphodynamic state and that both have response times characterised by it is hypothesised that optimised values in the shoreline model physically relate to the efficiency of sediment exchanges between the shoreface and offshore bars and the prevalence of one or two dimensional horizontal circulation the general success of this new shoreline model for hindcasting the observed shoreline behaviour at two distinctly different open coast sites suggests that this approach may be suitable for broader application

the predictability of cross shore bed evolution of sandy beaches at the time scale of storms and seasons using process based profile models deterministic and probabilistic profile models have been compared with hydrodynamic and morphodynamic data of laboratory and field experiments on the time scale of storms and seasons the large scale laboratory experiment is a pure 2d case and offers and ideal test case for cross shore profile models as disturbing alongshore non uniformities are absent the field experiments are performed at the egmond site the netherlands during the eu coast3d project and represent storm time scale oct nov 1998 as well as seasonal time scale conditions may 1998 sep 1999 the objective of the paper is to present information of coastal processes on these time scales and to assess the predictive capabilities coastal process based profile models with respect to hydrodynamics and morphodynamics at sandy beaches on the time scales of storms and seasons profile models can quite accurately errors smaller than 10 represent the cross shore significant wave height distribution in the surf zone if the wave breaking model is properly calibrated the wave breaking coefficient should be a function of local wave steepness and bottom slope for most accurate results profile models can reasonably represent the cross shore and longshore currents undertow in a pure 2d case and in 3d field conditions profile models including cross shore mixing effects and breaker delay effects do not produce better predictions of the longshore and cross shore current velocities profile models using default settings can quite reasonably simulate the behaviour of the outer and inner bars on the storm time scale the behaviour of the beach cannot be modelled with sufficient accuracy on the storm time scale profile models can reasonably simulate the post storm onshore bar migration provided that the near bed orbital velocities and wave asymmetry related sand transport are represented in a sufficiently accurate way using non linear wave theories profile models cannot simulate the beach recovery processes on the post storm time scale because these essentially 3d processes are not sufficiently known to be included in the models profile models using default settings cannot simulate the behaviour of the outer and inner bars and the beach on the seasonal time scale the behaviour of the outer bar on the seasonal time scale can only be represented properly after tuning using measured bed profiles the simulation of the inner bar and beach morphology on the seasonal time scale could not be improved by tuning

foredune morphological changes and beach recovery from the extreme 2013 2014 winter at a high energy sandy coast the beach dune response at truc vert sw france is analysed using dgps topographic surveys sampled every 2 4 weeks covering an alongshore distance of 1 5 km combined with wave tide and extreme water level hindcast and beach dune photographs during the 2013 2014 winter which was the most energetic since at least 1948 the beach dune system at truc vert eroded by approximately 180 m3 per beach width divided equally between beach and dune erosion beach and dune erosion was strongly variable alongshore with cuspate type rhythmic dune erosion scarps stripped of vegetation with a cross shore amplitude of 25 m the alongshore variable scarps were coupled with an alongshore variability in elevation of the beach with lower beach levels co located with the megacusp bays the following 10 months showed modest morphological beach and dune changes with for instance destabilisation of the scarped dune by trough blowouts scarp slumping and filling and seasonal beach berm dynamics the most profound morphological and vegetation changes occurred during the subsequent 10 months only 1 5 years after that winter the beach dune system at truc vert almost recovered to its pre winter volume but not to its pre winter foredune profile most of the sand volume recovery occurred during spring summer autumn 2015 when approximately 120 m3 m of sand naturally came back in the system the beach volume recovery rate was relatively steady and uncorrelated with wave conditions with rates twice as large across the megacusp bay profile as across the that of the megacusp horns during that period the widened and risen dry beach provided large fetch length enhancing onshore windblown transport and a rapid rising of the backshore the slumped and filled dune scarp which was providing a high barrier to aeolian transport from the beach to the dune since the 2013 2014 winter reformed as a dune ramp providing efficient conduit for beach dune delivery exchange of sediment by the end of the study this process favoured both natural revegetation into the scarp and incipient foredune formation despite the reinstatement of natural processes between the beach and the dune the dune foot was still located landward by more than 10 m on average with respect to its pre 2013 2014 winter position this study shows that even after the most severe winter over the last 68 years in terms of average wave energy arriving at the coast beach recovery can be a relatively fast process along high energy sandy beaches backed by large dunes in contrast foredune recovery which timing and magnitude can provide a proxy measure for the resilience of the system to climatic variability and change is a much slower process that can take years to decades

a shoreline evolution model considering the temporal variability of the beach profile sediment volume sediment gain loss abstract the prediction of shoreline variability along sandy coastlines is a valuable skill for a broad range of coastal engineering applications currently there are multiple proposals in the literature for equilibrium cross shore shoreline evolution models based on a constant equilibrium condition correlated with the shoreline position the aim of this paper is to present an extension of an existing equilibrium shoreline evolution model adding a rate of change component which in turn modifies the relationship between the equilibrium shoreline position and the incident wave energy as a function that advances or retreats over time the proposed model is applied to two study sites on the spanish coast on the one hand one and a half years of shoreline position data obtained from a video camera system at nova icaria beach catalonia are used to evaluate the shoreline evolution during a period of sediment contribution which is attributed to a sand bypass coming from bogatell beach on the other hand 16 years of shoreline position data acquired from beach profile surveys in campo poseidon huelva are used to reproduce the shoreline evolution taking into account the trend of sediment loss due to sediment drift alongshore the results obtained from both study sites using the proposed model show overall good performance the model successfully represents the general shoreline erosion accretion oscillations and the progressive trend of sediment gains or losses through the evolutionary relationship between the equilibrium shoreline position and the incident wave energy

a behavioral template beach profile model for predicting seasonal to interannual shoreline evolution 1 this contribution presents a simple behavioral template model for beach profile evolution which is calibrated and tested against a 6 year time series of shoreline position derived from a coastal imaging system at the gold coast australia from a coastal management perspective the position of the shoreline is arguably one of the most important morphodynamic parameters to be monitored and predicted and therefore forms the focus of this paper the template model attempts to encapsulate some of the current understanding of coastal dynamics deduced from both scientific investigations and observations the model framework is based on a simple relaxation model whereby the profile approaches a template exponentially with time under conditions of constant forcing the template evolves dynamically in response to incident wave forcing such that when a threshold value of the dimensionless fall velocity hs wtp where hs offshore significant wave height tp peak wave period and w sediment fall velocity is exceeded the beach face erodes and flattens and the shoreline retreats landward forming an erosional scarp and a breakpoint bar conversely when the falls below threshold progradation and steepening of the shoreface ensues accompanied by the evolution of a swash bar and breakpoint step the gold coast data are used to calibrate the threshold value of 4 0 which is close to the time series mean 3 8 testing the calibrated model on unseen data shows that it is able to reproduce the dominant seasonal interannual shoreline succession observed at this site and up to 77 of the detrended shoreline variability

sediments of the dry tortugas south florida usa facies distribution on a ramp like isolated carbonate platform abstract four sedimentary facies may be delineated based on quantitative analysis of texture and composition of modern surface sediments on the dry tortugas carbonate platform these include 1 mollusk halimeda wackestone 2 mollusk packstone to grainstone 3 coralgal halimeda grainstone and 4 coralgal grainstone even though the tortugas platform is characterized by an open circulation due to deep broad marginal channels and a lack of a continuous surface breaking marginal reef facies are not distributed at random and show bathymetrical zonation also facies appear to cover wide belts rather than forming a mosaic mollusk halimeda wackestone occurs in protected platform interior areas ca 10 18 m deep mollusk packstone to grainstone occurs in more open platform interior settings adjacent to channels and in deeper outer reef areas of 14 25 m water depth coralgal halimeda grainstone is found on shallow marginal shoals 1 11 m deep and coralgal grainstone on the somewhat deeper 3 16 m seaward edges of these shoals however there is bathymetrical overlap of facies in intermediate depths of ca 5 17 m this limitation has implications for the interpretation of the fossil record because changes in water depth are commonly thought to be reflected in facies changes e g in sequence stratigraphy comparison with previous sediment studies of the 1930s 1960s and 1970s in the area exhibit a decrease in coral fragments and increases in coralline algal and mollusk shell fragments these observations might be a result of environmental changes such as coral decline and die outs during temperature events disease and the increase in macroalgae due to the ecological extinction of the echinoid diadema the results suggest that more long term studies are needed that further explore the influence of environmental change on reef sediment composition dry tortugas surface sediments consist of lower portions of halimeda plates and mollusk shell fragments and higher percentages of coralline algal fragments as compared to sediments of the adjacent florida reef tract possibly as a consequence of differences in platform morphology and exposure to waves and currents

a comparison of coincidental time series of the ocean surface height by satellite altimeter mooring and inverted echo sounder altimetric measurements of sea surface height at two locations in the western tropical pacific ocean are compared to estimates of the dynamic sea surface height computed from cotemporal surface to bottom temperature salinity measurements on moorings and acoustic travel time measured by bottom moored inverted echo sounders the results show statistically high correlation between the in situ measurements at periods greater than 5 days and between the altimeter and in situ measurements at periods greater than 20 days the rms difference between any two modes of observation is consistently between 2 and 3 cm

relationship between foredune profile morphology and aeolian and marine dynamics a conceptual model abstract foredunes are highly dynamic coastal features that are intrinsically connected with their adjacent beaches correlations among parameters representative of aeolian and marine dynamics and the size and location of foredunes were carried out the results indicate that foredune steady state location depends mainly on marine dynamics given that foredune toe level was positively correlated with the total water level of 10 year return period which guarantees that the foredune is only eroded by waves occasionally and therefore will have time to recover and return to its long term morphological state foredune steady state size was characterized by its volume which was positively correlated with aeolian sediment drift potential and exponentially related to the total water level with a 10 year return period aeolian sediment drift potential is indicative of the total amount of sand that potentially reaches the foredune and therefore the foredune size is directly related to it higher total water level with a 10 year return period leads to a foredune located further from the shoreline and at a higher altitude higher toe level as mentioned above consequently the beach is wider and the presence of moisture is expected to be lower this wider and dryer beach allows the aeolian sediment transport to approximate to its maximum value increasing its potential to build a bigger foredune data confirmed that the total water level with a 10 year return period and the foredune volume are exponentially related the correlations found show that foredune steady state size is related to both aeolian sediment drift potential and marine dynamics based on these results a long term conceptual model is proposed to explain the different morphological characteristics of the steady state shape of foredunes as a function of the joint action of marine and wind dynamics

wavenumber frequency analysis of landslide generated tsunamis at a conical island part ii eof and modal analysis abstract in this paper the empirical orthogonal function eof method is applied to extract from the experimental data related to landslide tsunamis around the coast of a conical island the spatial modes that contribute to the wave field for each mode the wavenumber and the frequency are calculated by analyzing the shape along the coast and the time function the relevant modes are then compared with those obtained through numerical eigenanalysis of the long wave equation around the considered island it was possible to associate each eof mode with some eigenvectors and the corresponding eigenfrequencies both on the basis of the spatial shape the wavenumber calculated along the coast and the frequency results confirm that landslide generated waves propagate along the coast as trapped edge waves and the zero th order mode is the most important further of exploring the physics it is believed that this paper can be of use as some of the most relevant and straightforward techniques for modal identification are applied to the same problem and dataset

on the relation between the direction of the wave energy flux and the orientation of equilibrium beaches abstract the equilibrium beach planform concept has been widely used in recent years as an engineering tool for modeling shoreline changes designing new beaches and for stability studies of existing ones it defines the final shape of a beach on a scale of years which is important for solving erosion problems and for the design of nourishment projects throughout the literature the planform final shape hereinafter denoted as the static equilibrium beach orientation sebo is obtained based on the direction of the mean wave energy flux of whole waves impinging on the coast this paper investigates the effect of beach sediment size and the shape of the directional distribution sdd of the energy flux of the wave climate on the direction that dictates the sebo the study employs field data from 32 beaches along the spanish coast and available long term databases of directional wave climates initiation of sediment motion due to wave action is taken into account in order to filter the directional wave climate to consider only waves that are capable of moving the sediment the results indicate that the direction of the mean energy flux of filtered waves is more appropriate for the determination of the sebo than that of whole waves additionally the results confirm the importance of both the filtration process of the local directional wave climate and the usage of the whole directional spectra in stability studies and coastal engineering practice

a currents of removal approach for interpreting carbonate sedimentary processes abstract this study develops a currents of removal methodology to examine and quantify the nature of physical transport processes affecting the formation of bioclastic deposits in the cocos keeling islands an indian ocean atoll this approach is based on the hydraulic settling and threshold of entrainment characteristics of bioclastic deposits and measured current energy potential mobility pm analysis of 157 samples quantifies the proportion of deposits able to be transported in each geomorphic zone results show that under mean energy conditions wave induced currents entrain and transport sediment within the atoll and show that transport of sediment is not solely reliant on storm energy conditions gradients of pm values are used to reconstruct sediment transport pathways from the reef flat 85 100 pm through shallow passages 75 100 pm to sand aprons 50 75 pm and shallow 0 20 pm and deep lagoon 0 pm comparison of settling velocity distributions of bed material and sediment retained in sediment trap experiments show that actual mobility levels correspond with pm estimates potential mobility analysis also identifies the immobile portions of deposits which increase lagoonward constituent analysis of immobile fractions and analysis of settling frequency distributions are used to differentiate the importance of physical and biological processes in the formation of deposits throughout cocos and identify the role of each geomorphic zone in the transport system the pattern of sediment is controlled by physical processes between the reef flat the primary sediment production zone with sediment transported through the shallow passage conduits to the sand aprons the formation of shallow and deep lagoon deposits is controlled by autochthonous sediment production and storm deposition potential mobility analysis is a powerful tool enabling physical transport processes within bioclastic sedimentary environments to be quantified the ability to examine an individual deposit s hydraulic behaviour and development also enables depositional processes to be examined at a much finer resolution than previously attempted using conventional textural approaches

natural variability of shoreline position observations at three pocket beaches we investigated the variability of shoreline position of three adjacent pocket beaches at barcelona city nw mediterranean over a period of two years daily measurements of shoreline position were extracted from high resolution video images and used to determine shoreline variability using empirical orthogonal function analysis we determine two dominant modes of shoreline variability for all beaches analysed the mode that explains most of the variability around 70 describes the beach plan form rotation which primarily occurs at the seasonal scale the cross shore translation of the beach profile is described by the 2nd mode which explains around 30 both types of shoreline movement have been related to the previous nearshore conditions this relationship was explored standardizing the translation rotation of the shoreline and comparing it with time averages of the cross shore energy flux efcsh and the energy flux direction efd averages over 7 to 12 days of efcsh were significantly correlated to the translation movement plan form rotation was well described by 28 to 40 day averaging of efd comparing results from the three beaches we determined that the time required to average the previous wave conditions depends on the beach characteristics beach length and sediment grain size in such a way that the greater the length of the beach and its sediment grain size the slower its response

high resolution downscaled ocean waves dow reanalysis in coastal areas abstract large scale wave reanalysis databases 0 1 1 spatial resolution provide valuable information for wave climate research and ocean applications which require long term time series 20 years of hourly sea state parameters however coastal studies need a more detailed spatial resolution 50 500 m including wave transformation processes in shallow waters this specific problem called downscaling is usually solved applying a dynamical approach by means of numerical wave propagation models requiring a high computational time effort besides the use of atmospheric reanalysis and wave generation and propagation numerical models introduce some uncertainties and errors that must be dealt with in this work we present a global framework to downscale wave reanalysis to coastal areas taking into account the correction of open sea significant wave height directional calibration and drastically reducing the cpu time effort about 1000 by using a hybrid methodology which combines numerical models dynamical downscaling and mathematical tools statistical downscaling the spatial wave variability along the boundaries of the propagation domain and the simultaneous wind fields are taking into account in the numerical propagations to performance similarly to the dynamical downscaling approach the principal component analysis is applied to the model forcings to reduce the data dimension simplifying the selection of a subset of numerical simulations and the definition of the wave transfer function which incorporates the dependency of the wave spatial variability and the non uniform wind forcings the methodology has been tested in a case study on the northern coast of spain and validated using shallow water buoys confirming a good reproduction of the hourly time series structure and the different statistical parameters

a reevaluation of coastal embayment rotation the dominance of cross shore versus alongshore sediment transport processes collaroy narrabeen beach southeast australia 1 over 30 years of wave and beach survey data at collaroy narrabeen beach in southeast australia are analyzed to investigate the extent to which shoreline variability within this coastal embayment is dominated by shoreline oscillations due to cross shore sediment exchange or shoreline rotations due to alongshore exchange between the beach s extremities offshore wave data are derived from both buoy measurements and era 40 reanalysis data eof analysis of the monthly shoreline data suggests that the dominant mode of shoreline variability 60 of variability is an onshore offshore sediment exchange that is greater at the more exposed northern end of the beach than at the predominantly sheltered southern end this mode is primarily associated with variability in wave energy storms which by the nature of the wave climate of this region chiefly occurs from the south southeast the secondary mode of shoreline variability 26 of variability is a rotational signal between either end of the beach which coincides with 24 of the offshore wave climate shifting between the south southeast and east as well as changes in the wave period and wave energy storms a distinct annual cycle is identified in this rotation signal it is concluded that alongshore sediment transport processes associated with embayment rotation is more subtle than previously thought and a refined conceptual model of coastal embayment variability in this region is presented highlighting the dominance of cross shore sediment exchange processes

tidal corrections for topex altimetry in the coral sea and great barrier reef lagoon comparisons with long term tide gauge records 1 the well known capability of topex poseidon altimetry to map sea levels precisely in the deep oceans motivates its application to the topographically complex coral sea and ne australian continental margin we assess several global tidal models for correcting topex altimetry in the coral sea and find csr3 0 offers good overall performance based on comparisons of model predicted and tide gauge harmonic constituents using csr3 0 tidal corrections we evaluate residual sea surface height ssh root mean square rms variability and residual m2 tidal alias errors away from large reefs and islands csr3 0 amplitude and phase errors for m2 are typically less than 5 cm and 8 deg respectively with rms tidal errors of 5 cm or less and rms ssh residuals approximating 10 cm since model deficiencies appear in the macro tidal region of the southern great barrier reef lagoon near broad sound we employ a high resolution hydrodynamic model in this area to compute the tidal corrections predicted m2 amplitude and phase in this region are within 3 cm and 5 deg of observations rms errors are mostly under 4 cm and coastal rms ssh residuals are as low as 15 cm in spite of coastal trapped waves and submesocale eddies in the lagoon daily and monthly smoothed ssh residual time series respectively yield optimal lagged correlations with in situ sea level data in the range 0 3 0 9 and 0 6 0 9 for locations spanning the coral sea and in the lagoon lag correlations of monthly smoothed geostrophic current anomalies derived from topex ssh gradients with long term currents from the continental slope yield optimal correlations of 0 5 and 0 8 respectively near jewell lat 14 deg s and myrmidon reef 19 deg s our results demonstrate that low frequency sea level and geostrophic current variations can be reliably observed using altimetry over the coral sea and ne australian continental slope and for selected locations on the continental shelf if appropriate tide correction models are employed

shoreline evolution model from a dynamic equilibrium beach profile abstract although simpler than process based models state of the art shoreline evolution models based on the idea of cross shore equilibrium still depend on at least 4 free parameters these dynamic equilibrium models are generally based on a kinetic equation in which shoreline change rate is proportional to the existing disequilibrium therefore a link between the model driving forces and their corresponding equilibrium shoreline position is necessary for their implementation until now this correlation has been established only empirically adding calibration parameters to the model in this paper an analytical correlation between the wave energy and the equilibrium shoreline position equilibrium energy function eef is obtained from known invariant beach physical characteristics according to a theoretical bi parabolic equilibrium beach profile ebp a wave driven shoreline evolution model related to cross shore processes for the medium and long term is then developed with just one free parameter as the combination of a kinetic equation simply proportional to the wave energy disequilibrium and the proposed analytical eef it is remarkable that at the particular case of the beach of nova icaria where the model has been calibrated and validated by means of two years of video monitoring the proposed analytical eef obtained only as a function of the so called ebp invariants fits shoreline observations as well as a calibrated eef with precisely shoreline observation the results at nova icaria of the proposed model show the same skills with just one calibration parameter than state of the art models with over 4 free parameters nevertheless observations in different sites with diverse beach characteristics and wave conditions are needed to widely validate the analytical form of the eef and the shoreline evolution model proposed in this paper

the transient nature of the empty bucket model of reef sedimentation abstract the geometry of modern reefs has been likened to an empty bucket with the narrow reef rim comprising the container pail that encloses the water filled bucket while the analogy is valid the assumption that this constitutes a final geometry is not examples from the indian pacific and atlantic oceans individually and collectively demonstrate current filling of the lagoons by reef perimeter sand aprons since sea level only approximated its present position 3 to 6 ky ago it follows that the observed extent of modern highstand lagoon filling is minimal if the filling process was to continue unabated the result would be a flat topped bank but during the pleistocene low stands of sea level aborted the filling process extrapolating these relationships to the geologic record suggests that the empty bucket model of unfilled reef lagoon space is greatest during icehouse high frequency glacial fluctuations of sea level alternatively filled buckets in which cycle thickness approximates accommodation space are probably largely restricted to greenhouse time intervals the co occurrence of quaternary high amplitude frequency sea level changes with rapidly growing scleractinian corals probably enhanced the occurrence of empty bucket morphologies

nourishment evolution and impacts at four southern california beaches a sand volume analysis abstract four southern california beaches were nourished with offshore sand placed as subaerial pads several meters thick 50 m wide and spanning between 500 and 1500 m alongshore three nourishments constructed with coarser than native sand placed in 2012 at imperial cardiff and solana beaches elevated subaerial sand volumes for several years even when exposed to the energetic winter waves of the 2015 16 el nino followed by a stormy 2016 17 winter as these relatively resilient pads were overwashed landward tilted subaerial profiles accretionary crowns formed at the eroding front face of the originally flat topped pads and pooling occurred in the backbeach at imperial beach nourishment sand helped prevent waves from directly impacting riprap fronting houses while groundwater flooding behind the pad was observed at a location where the pad was elevated 1 6 m above the street as the nourishments retreated alongshore oriented spits grew downdrift from the eroding face the alongshore displacement of the subaerial center of mass of the 2012 nourishments is positively correlated with the seasonally varying s x y the alongshore radiation stress component after four years the net southward drift of the imperial beach nourishment contributed to the winter 2016 closure of the tijuana river mouth and the associated hyper polluted and anoxic estuary conditions nourishment impacts on sand levels on rocky reefs were not unambiguously detectable in the background of natural variability over several years gains or losses in the total sand volume integrated from the back beach to 8 m depth over the few km alongshore survey spans are sometimes comparable to nourishment volumes suggesting relatively large interannual sediment fluxes across the control volume boundaries the clearest trend in total volume is at torrey pines during 16 years since the 2001 nourishment about 300 000 m3 of sand has been lost if the trend continues the thinning veneer of sand will be removed more often from the subaerial winter beach exposing rocks and cobbles

on the interpretation of shallow shelf carbonate facies and habitats how much does water depth matter abstract many stratigraphic studies of ancient shallow water carbonate platforms focus interpretation on the primacy of changes in accommodation inferred by assuming a direct and deterministic link between depositional facies and water depth the purpose of this study is to test this assumption explicitly and quantitatively by exploring relations between substrate type classified on the basis of both habitats and facies and the water depth at which they occur on a modern well studied shallow rimmed shelf margin gis analysis of digital benthic habitat and bathymetry maps of the shallow 8 m south florida shelf illustrate that most substrate types occur across a range of water depths similarly at greater water depths habitats and facies are more constrained more dominance of one class more deterministic with generally decreasing dominance more diversity at shallower water depths at a scale of shelf to basin transects facies and habitats clearly are related to water depth yet on this narrower 10 km shallow shelf margin at the scale of this study water depth and habitats and facies are not uniquely related or linked this general lack of correspondence between bottom type and water depth may be a manifestation of landscape disequilibrium a state in which habitats and facies do not fully reflect ambient environmental conditions perhaps recording the influence of rapid change in sea level alternatively it may reflect the impact of variables other than water depth although more general consequences of these results for other depositional settings remains to be evaluated they do emphasize the fact that variables other than bathymetry may significantly influence the ecological and sedimentologic attributes of depositional surfaces they do allow for the quantification of some of the potential uncertainties inherent in the interpretation of analogous ancient platforms and can serve to focus future observations on the causes and consequences of vertical and lateral heterogeneity in ancient stratigraphic sequences

dynamic equilibrium planform of embayed beaches part 2 design procedure and engineering applications abstract the design of equilibrium beach systems employing beach nourishment techniques in conjunction with coastal support structures has received increased interest from coastal engineers in recent years one such solution to remedy coastal erosion problems is to design an equilibrium pocket beach in order to stabilize the shoreline such coastal landforms may exist in nature in static or dynamic equilibrium states the concept of the static equilibrium planform sep has received much more attention from coastal engineers than that paid to the dynamic equilibrium planform dep this paper presents a design procedure for embayed beaches in dynamic equilibrium which have a specific net littoral drift rate the proposed methodology employs the net sediment transport rate passing through the bay together with the time series of the wave climate impinging on the beach in order to compute the angle d this angle represents the difference in degrees between the direction of the mean wave energy flux at the diffraction point ef and the orientation of the dynamic equilibrium beach db to be utilized in a newly derived dep formula to predict the shoreline shape in the long term the procedure was applied and validated using prototype bays in dynamic equilibrium with different net sediment transport rates along the brazilian coast producing good results furthermore it was employed as a tool to investigate the influence of changes in the net annual littoral drift rate on the dep shape in a case study along the spanish coast taken together these confirm its utility as a valuable tool for coastal management and engineering practice

waves along the equator in the atlantic abstract spectra of two hundred days of data from five inverted echo sounders deployed along the equator in 1983 84 and a thousand days of 30 crossings of the equator by the topex poseidon altimeter in 1993 95 are both found to have enhanced variance of sea surface displacement in two frequency bands centered nominally about 50 1 and 25 1 cycles day complex empirical orthogonal function analysis of the two bands finds much of the variance being accounted for by eastward and westward propagating waves respectively that are coherent across the basin the eastward propagating wave is identifiable as a first mode kelvin wave with a period of 54 49 days in the sounder altimeter dataset a basinwide wavelength and a speed of 2 1 1 8 m s 1 it is suggested that the westward propagating wave is a surface expression of the meridional oscillation of the equatorial undercurrent about the equator presumably induced by a tropical instability wave with a period of 24 28 days a wavelength of 600 580 km

quantification of nearshore morphology based on video imaging abstract the argus network is a series of video cameras with aerial views of beaches around the world intensity contrasts in time exposure images reveal areas of preferential breaking which are closely tied to underlying bed morphology this relationship was further investigated including the effect of tidal elevation and wave height on the presence of wave breaking and its cross shore position over sand bars computerized methods of objectively extracting shoreline and sand bar locations were developed allowing the vast quantity of data generated by argus to be more effectively examined once features were identified in the images daily alongshore mean values were taken to create time series of shoreline and sand bar location which were analyzed for annual cycles and cross correlated with wave data to investigate environmental forcing and response these data extraction techniques were applied to images from four of the argus camera sites a relationship between wave height and shoreline location was found in which increased wave heights resulted in more landward shoreline positions given the short lag times over which this correlation was significant and that the strong annual signal in wave height was not replicated in the shoreline time series it is likely that this relationship is a result of set up during periods of large waves wave height was also found to have an effect on sand bar location whereby an increase in wave height resulted in offshore bar migration this correlation was significant over much longer time lags than the relationship between wave height and shoreline location and a strong annual signal was found in the location of almost all observed bars indicating that the sand bars are migrating with changes in wave height in the case of the site with multiple sand bars the offshore bars responded more significantly to changes in wave height whereas the innermost bar seemed to be shielded from incident wave energy by breaking over the other bars a relationship was also found between a site s mean wave height and inner sand bar location sites with the highest wave heights tended to have sand bars farther from shore than those with relatively low wave heights

a nearshore long term infragravity wave analysis for open harbours abstract this study presents a comprehensive methodology for the reanalysis characterization and propagation of wave bound infragravity waves 1 300 hz to 1 30 hz in the nearshore a deep water short wave reanalysis has been modified analytically to include the energy input associated with infragravity waves full spectrum through the decomposition and energy balance of the radiation stress of waves in deep water a hybrid clustering numerical wave propagation downscaling technique was used forced by the modified full wave spectra previously obtained resulting in hourly series of high spatial resolution nearshore ocean waves including short and bound long waves the methodology has been applied to the northern coast of spain and validated by comparing buoy and pressure gauge records in the coast for short wave agitation and infragravity wave resonance responses in open harbours with very satisfactory results

dynamics of single barred embayed beaches abstract the dynamics of single submerged sandbars of two artificial embayed beaches la barceloneta and bogatell barcelona nw mediterranean has been studied with a video recorded data set of 4 3 years the alongshore averaged cross shore migration the orientation with respect the shoreline and the sinuosity of the barlines have been analyzed and related to wave conditions alongshore sediment transport and shoreline variability in general the submerged bars follow the general cyclic morphological behaviour observed in natural beaches switching among the four intermediate morphodynamic states but the studied beaches can be arrested during long periods of low wave conditions the dominant up state transition in barcelona beaches during storms is the transition toward the rhythmic bar and beach state the complete morphodynamic reset longshore bar and trough state only occurring during extreme wave events the cross shore migration of bars is dominated by the weekly and interannual components the interannual component shows an onshore bar migration trend at both beaches in contrast with the net offshore migration observed in multibarred open beaches bar disposition is located progressively seaward in the dominant alongshore transport direction i e oblique with respect to the shoreline at la barceloneta beach shoreline and barline orientations change consistently and a significant correlation between the accumulated alongshore sediment transport and the associated change in bar orientation has been found suggesting that alongshore transport can play a significant role in barline orientation finally bar sinuosity increases during eastern storms in both beaches this indicates that the formation of crescentic bars occurs for approximately shore normal waves some of the differences observed in bar morphology and mobility in the two studied beaches are related to their different level of protection with respect to the incident waves beach indentation

the middle eocene seeb formation of oman an investigation of acyclicity stratigraphic completeness and accumulation rates in shallow marine carbonate settings abstract the middle eocene seeb formation represents deposition on one of the earliest modern style carbonate platforms i e influenced by seagrasses and mangroves and presents an opportunity to explore controls on the preservation of cenozoic carbonate lithofacies in the study area the seeb fm is dominated by an anomalously thick approximately 250 m and uniform package of shallow marine platform interior sediments these nodular indistinctly bedded shallow subtidal sediments display no evidence for relative sea level change such as subaerial exposure features and lack the shallowing upwards cyclothems that have characterized carbonate sediments deposited in platform interior settings throughout much of the rock record particularly during greenhouse periods we conclude that this is a consequence of thorough bio retexturing of the sediment by burrowing organisms and the roots of marine vegetation which destroyed primary fabrics facies diversity evidence for cyclicity and missing time horizons such as cycle bounding exposure surfaces it seems possible that the remarkable thickness of apparently acyclic seeb fm sediment that built up may reflect increased bio disturbance of the shallow marine environment following the late cretaceous expansion of seagrasses and mangroves a similar lack of peritidal cyclothems may be common to many cenozoic shallow marine carbonate deposits missing time horizons in limestones reflecting erosion or nondeposition have been identified by some authors to explain discrepancies between low calculated accumulation rates of ancient sediments and higher rates measured in comparable modern environments however our studies of the seeb fm suggest that the significance of such missing time horizons in ancient sediments may have been overstated and that apparent differences between modern and ancient accumulation rates are a consequence of the extrapolation of unrepresentative localized high rates of modern sediment production to large platform scale areas our study reinforces the idea that modern sediment production and accumulation rates may be much lower than previously thought because they are typically measured in highly productive areas such as seagrass beds and do not take into account the highly variable nature of carbonate production storage erosion and destruction across platforms therefore far less missing time needs to be inferred for ancient sediments to account for any imbalance between modern and ancient sediment accumulation rates

a hybrid efficient method to downscale wave climate to coastal areas long term time series of sea state parameters are required in different coastal engineering applications in order to obtain wave data at shallow water and due to the scarcity of instrumental data ocean wave reanalysis databases ought to be downscaled to increase the spatial resolution and simulate the wave transformation process in this paper a hybrid downscaling methodology to transfer wave climate to coastal areas has been developed combining a numerical wave model dynamical downscaling with mathematical tools statistical downscaling a maximum dissimilarity selection algorithm mda is applied in order to obtain a representative subset of sea states in deep water areas the reduced number of selected cases spans the marine climate variability guaranteeing that all possible sea states are represented and capturing even the extreme events these sea states are propagated using a state of the art wave propagation model the time series of the propagated sea state parameters at a particular location are reconstructed using a non linear interpolation technique based on radial basis functions rbfs providing excellent results in a high dimensional space with scattered data as occurs in the cases selected with mda the numerical validation of the results confirms the ability of the developed methodology to reconstruct sea state time series in shallow water at a particular location and to estimate different spatial wave climate parameters with a considerable reduction in the computational effort

the effects of callianassa bioturbation on the preservation of carbonate grains in davies reef lagoon great barrier reef australia abstract coring air life excavation and tracer sediment experiments in the lagoon floor sediments of davies reef revealed that callianassid shrimp had produced during their feeding a 5 60 cm thick surface layer of moderately to poorly sorted gravel free sediment above very poorly sorted gravelrich sediment the subsurface gravel is epilithic in origin close to reef framework but consists predominantly of infaunal molluscs through most of the lagoon these infaunal skeletons tend to be buried rapidly in a well preserved state escaping the microboring that attacks all grains on the surface two geologically significant points emerge first the surface layer will not get preserved in its present form and any analyses of surface samples can give a false impression of the accumulating sedimen pile and the prevailing hydraulic regime and second the combination of continuous fine sediment recycling and surface microboring can lead to a bias in the fossil reefal limestone record with epilithic organisms seemingly subordinate to infaunal molluscs

holocene reef accretion on the rodrigues carbonate platform an alternative to the classic bucket fill model carbonate platform evolution around the island of rodrigues southwestern indian ocean is reconstructed from cores recovered across the platform9s windward margin in contrast to the classic bucket fill model of carbonate platform evolution whereby platform filling occurs predominantly as a function of the lagoonward transport of sediment from the reef rim data from rodrigues demonstrate that the primary mode of platform filling was through reef progradation from the platform interior seaward indeed radiocarbon dates indicate that much of the platform interior had filled by 2000 cal calibrated yr b p data also indicate that the reef rim probably caught up with sea level only in the past 1000 yr and subsequent export of sediment from those areas into the lagoon has probably only become important during the final stages of the platform9s evolution we interpret this as a function of the platform margin reef9s catch up growth mode this would have allowed significant marine circulation within the platform interior thus promoting active reef growth prior to sea level being attained given that such catch up growth modes are widely recognized on many reef platform margins we suggest that this novel platform evolutionary model may have widespread applicability sounder resolution 10 cm were made at each core site and water depths were normalized to the tide curves and corrected to mean sea level msl is 1 872 m above chart datum all core depth measurements were uncompacted and were normalized to msl

assessing the suitability of video imaging for studying the dynamics of nearshore sandbars in tideless beaches nearshore sandbars an important natural defense mechanism of the beaches can be monitored using shore based video systems before studying bar dynamics with video images we must establish the relationship between the real bar positions and the videoed bar positions detected by the preferential wave breaking on the shallows this analysis becomes essential in the two studied tideless beaches of barcelona due to the critical differences with respect to the sites studied previously bogatell beach is terraced without a trough in more than 50 of the profiles there the videoed barlines are a good proxy of the terrace edge position in la barceloneta beach with dominance of barred profiles the videoed barlines better represent the bar crest position on average the obtained distances between real and videoed bar positions r are 10 15 m with the videoed barlines located shoreward changes in the bathymetric profile shape and the root mean squared wave height h rms induce a variability of r of 16 m in la barceloneta and 13 m in bogatell this apparent variability masks the real changes in bar position and should preferably be reduced before further analysis as a highly significant correlation between r and h rms is detected in the two beaches the proposed reduction method consists of sampling at a specific range of h rms this diminishes the variability by 10 to 14 m in la barceloneta and 11 m in bogatell this paper confirms the suitability of using video systems for monitoring bars and terraces in the barcelona beaches

ocean currents and sea surface heights estimated across the west florida shelf abstract the across shelf structures of the ocean circulation and the associated sea surface height ssh variability are examined on the west florida shelf wfs for the 3 yr interval from september 1998 to december 2001 five sets of characteristic circulation patterns are extracted from 2 day low pass filtered data using the self organizing map extreme upwelling and downwelling structures with strong currents asymmetric upwelling and downwelling structures with moderate currents and a set of transitional structures with weak currents the temporal variations of these structures are coherent with the local winds on synoptic weather time scales on seasonal time scales they are related to both the local winds and the water density variations the circulation is predominantly upwelling during autumn to spring months october april and downwelling during summer months june september coastal sea level fluctuations are related to both the dynamical responses of the inner shelf circulation to meteorol

drivers of alongshore variable dune erosion during a storm event observations and modelling abstract the ability to understand and predict alongshore variable sand dune erosion is key to better coastal management this study utilizes detailed observations immediately pre during and post storm topography waves and water levels collected over a 6 day period at the 3 6 km long narrabeen collaroy beach in south east australia to identify and explore drivers of the highly variable alongshore dune erosion caused by an east coast low storm in june 2011 key characteristics of the immediately pre storm subaerial morphology obtained by airborne lidar beach slope dune toe elevation dune height varied considerably alongshore daily airborne lidar surveys conducted at low tide indicated considerable temporal variability in the evolution of the subaerial beach profile despite considerable alongshore variability in the magnitude of modelled inshore wave heights during the storm it was instead observed that the predominant determinant of maximum dune erosion was the pre storm dune toe elevation a simple dune impact model forced with local alongshore variable inshore wave modelling was found to successfully predict up to 85 of the observed alongshore variability in dune erosion at this site with this erosion tidally modulated over the 6 days to time periods when the waves were directly impacting the dune importantly alongshore variation in wave height is shown to account for just 10 of the alongshore variability in dune erosion during this storm these results reconfirm that knowledge of the pre storm subaerial morphology in particular the elevation of the dune toe with respect to time varying water levels during a storm is a key driver of alongshore variability in the erosion response along dune backed sandy coastlines

modeling storms improves estimates of long term shoreline change 1 large storms make it difficult to extract the long term trend of erosion or accretion from shoreline position data here we make storms part of the shoreline change model by means of a storm function the data determine storm amplitudes and the rate at which the shoreline recovers from storms historical shoreline data are temporally sparse and inclusion of all storms in one model over fits the data but a probability weighted average model shows effects from all storms illustrating how model averaging incorporates information from good models that might otherwise have been discarded as un parsimonious data from cotton patch hill de yield a long term shoreline loss rate of 0 49 0 01 m yr about 16 less than published estimates a minimum loss rate of 0 34 0 01 m yr is given by a model containing the 1929 1962 and 1992 storms

altimeter derived variability of surface velocities in the california current system 1 evaluation of topex altimeter velocity resolution in this paper we evaluate the temporal and horizontal resolution of geostrophic surface velocities calculated from topex satellite altimeter heights moored velocities from vector averaging current meters and an acoustic doppler current profiler at depths below the ekman layer are used to estimate the temporal evolution and accuracy of altimeter geostrophic surface velocities at a point surface temperature gradients from satellite fields are used to determine the altimeter s horizontal resolution of features in the velocity field the results indicate that the altimeter resolves horizontal scales of 50 80 km in the along track direction the rms differences between the altimeter and current meters are 7 8 cm s 1 much of which comes from small scale variability in the oceanic currents we estimate the error in the altimeter velocities to have an rms magnitude of 3 5 cm s 1 or less uncertainties in the eddy momentum fluxes at crossovers are more difficult to evaluate and may be affected by aliasing of fluctuations with frequencies higher than the altimeter s nyquist frequency of 0 05 cycles d 1 as indicated by spectra from subsampled current meter data the eddy statistics that are in best agreement are the velocity variances eddy kinetic energy and the major axis of the variance ellipses spatial averaging of the current meter velocities produces greater agreement with all altimeter statistics and increases our confidence that the altimeter s momentum fluxes and the orientation of its variance ellipses the statistics differing the most with single moorings represent well the statistics of spatially averaged currents scales of 50 100 km in the ocean besides evaluating altimeter performance the study reveals several properties of the circulation in the california current system 1 velocity components are not isotropic but are polarized strongly so at some locations 2 there are instances of strong and persistent small scale variability in the velocity and 3 the energetic region of the california current is isolated and surrounded by a region of lower energy starting 500 700 km offshore this suggests that the source of the high eddy energy within 500 km of the coast is the seasonal jet that develops each spring and moves offshore to the central region of the california current rather than a deep ocean eddy field approaching the coast from farther offshore

dynamic equilibrium planform of embayed beaches part 1 a new model and its verification abstract equilibrium beach formulations are useful tools for diagnosing and managing coastal engineering problems providing solutions for beach erosion problems headland bay beaches hbbs can be used as equilibrium coastal systems for stabilizing coastlines and mitigating erosion problems these embayed beaches may exist in a state of static or dynamic equilibrium throughout the literature several equations can be found for obtaining the static equilibrium planform sep of headland bay beaches hbbs with almost negligible net littoral drift rates however the formulations used to define the dynamic equilibrium planform dep of embayed beaches with specific net sediment transport rates are scarce and based on a limited number of studies this paper proposes a new derived formula for obtaining the planform shape of hbbs in dynamic equilibrium conditions the formula represents a general form of the parabolic bay shape equation pbse with modified coefficients as a function of both the wave obliquity and the net littoral drift rate passing through the bay q the angular difference d between the direction of the mean wave energy flux at the diffraction point of the headland and the beach orientation down coast is also incorporated in the proposed formula the model was verified against natural hbbs in dynamic equilibrium with different net littoral drift rates along the brazilian coast producing good results

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

numerical modelling of erosion rates life span and maintenance volumes of mega nourishments mega nourishments aiming at providing long term coastal safety nature qualities and recreational space have been applied recently at the holland coast and are considered at various other places in the world methods to quickly evaluate the potential and lifetime of these coastal mega nourishments are therefore very much desired which is the main objective of this research two types of mega nourishments can be distinguished feeder type mega nourishments may erode freely to feed adjacent coasts for a more natural dynamic dune growth while permanent mega nourishments are designed to preserve safety levels and need to maintain their size and shape and thus needs to be nourished themselves the design and impact assessment studies for both types of mega nourishments require detailed morphological studies to determine the morphological evolution in this paper 2dh delft3d and 1d unibest cl and longmor numerical models were calibrated using data of the sand motor mega nourishment and were then applied to model a series of mega nourishments with various width over length ratios and volumes in order to derive relations and design graphs for erosion rates life span and maintenance volumes these relations and design graphs can be used in project initiation phases and feasibility studies the magnitude of the modelled wave driven longshore sediment transport rates in 1d coastline models depend on the representation of wave refraction on the lower shoreface since a distinction should be made between the non rotating lower shoreface and active surfzone it was shown that the life time of nourishments is mainly determined by the dimensions of the nourishment and incoming wave energy

modeling the effects of wave climate and sediment supply variability on large scale shoreline change abstract the application of an integrated data analysis and modeling scheme reveals that decadal scale shoreline evolution along a u s pacific northwest littoral cell is highly dependent on both sediment supply and wave climate variability in particular accurate estimates of columbia river sediment supply and sediment feeding from the lower shoreface are critical components of balancing the barrier beach sediment budget and are therefore essential to making sensible shoreline change hindcasts and forecasts a simple deterministic one line shoreline change model applied in a quasi probabilistic manner enables evaluation of the influence of sediment supply and wave climate variability through simulation of historical shoreline change through iteration a range of realistic scenarios are developed to constrain decadal scale shoreline change predictions modeled shoreline changes are significantly sensitive to directional changes in the incident waves and therefore sensitive to the occurrence of interannual climatic fluctuations such as major el nino events a predicted increase in the intensity of the east pacific wave climate 1 0 m increase in significant wave height in 20 yr affects forecast shoreline positions only when this increase occurs during the winter storm season however the effect of this increase in storm power during any given year is small relative to the impact of major el nino events the model has significant skill in decadal scale hindcasts suggesting that alongshore gradients in sediment transport dominate coastal change at this scale at this site however both data and model results suggest that net onshore feeding from the lower shoreface is responsible for approximately 20 of the decadal scale coastal change field measurements and poor model skill at annual scale indicate that cross shore processes likely dominate coastal change at shorter time scales

regional identification in the tropical atlantic ocean of residual tide errors from an empirical orthogonal function analysis of topex poseidon altimetric data two years october 1992 to september 1994 of topex poseidon data have been processed over the tropical atlantic ocean to produce monthly sea level anomalies four different oceanic tide corrections have been applied in order to quantify the effect of this correction on the large scale altimetrically determined sea level variability and to identify potential residual tide errors two tide corrections are drawn from the u s university of texas tide model and two others are drawn from the french grenoble tide model comparison of the altimetric sea level anomalies with tide gauge data gives rms differences of between 2 and 5 cm equivalent to those already observed by several authors during recent topex poseidon studies however this paper demonstrates that the 2 monthly oscillations which were previously identified in investigations using old versions of tide corrections still remain to some extent independently of the new tide models being used these 2 monthly oscillations are not only located along the western boundary and therefore cannot be attributed to 40 to 60 day oscillations observed in several mooring records in that area an empirical orthogonal function analysis of the altimetric data clearly shows that these oscillations are due to tide aliasing this approach also emphasizes the improvement finalized by the more recent versions of the university of texas and the grenoble tide models however the most convincing result of this analysis is that it allows regional quantification of the impact of tidal residual error aliasing which persists even when the more sophisticated tide models are used

oceanic tides from geosat altimetry direct tidal analysis of the altimetry from the geosat exact repeat mission s first year is used to derive estimates of the diurnal and semidiurnal oceanic tides the geoid is removed by collinear differences at 34 1 day separation and the orbit error is reduced by subtracting a slowly modulated 1 cycle revolution term a sequence of independent analyses at grid areas of 1 latitude 1 5 longitude using orthotide functions ensures complete definition of the diurnal and semidiurnal species global admittance maps for m2 and s2 within the latitudes 58 n and 59 s compare well with ground truth at 66 open ocean sites maps of differences between geosat and the naval surface weapons center model show important areas of the order of 10 15 cm the integral for the global power input from the moon gives 2 51 tw m2 0 44 tw s2 lower than many previous estimates but in agreement with figures deduced from a recent analysis of satellite orbits

a generalized equilibrium model for predicting daily to interannual shoreline response coastal zone management requires the ability to predict coastline response to storms and longer term seasonal to interannual variability in regional wave climate shoreline models typically rely on extensive historical observations to derive site specific calibration to circumvent the challenge that suitable data sets are rarely available this contribution utilizes twelve 5 year shoreline data sets from around the world to develop a generalized model for shoreline response the shared dependency of model coefficients on local wave and sediment characteristics is investigated enabling the model to be recast in terms of these more readily measurable quantities study sites range from microtidal to macrotidal coastlines spanning moderate to high energy beaches the equilibrium model adopted here includes time varying terms describing both the magnitude and direction of shoreline response as a result of onshore offshore sediment transport between the surf zone and the beach face the model contains two coefficients linked to wave driven processes 1 the response factor that describes the memory of a beach to antecedent conditions and 2 the rate parameter c that describes the efficiency with which sand is transported between the beach face and surf zone across all study sites these coefficients are shown to depend in a predictable manner on the dimensionless fall velocity that in turn is a simple function of local wave conditions and sediment grain size when tested on an unseen data set the new equilibrium model with generalized forms of and c exhibited high skill brier skills score bss 0 85

observations of inertia gravity waves in the atlantic from inverted echo sounders during fgge abstract the study is based on observations from inverted echo sounders anchored near the equator in the western atlantic ocean it appears to be a good method of detecting inertia gravity waves with large vertical scale the spectral analysis of the records shows variable spectral density levels in the band of 2 5 days three of the four inverted echo sounder ies records show an increase in the variance centered at 3 75 days in addition two sounders deployed during the latter half of the year stronger winds also show a peak in the variance at 2 14 and 2 31 days the most likely interpretation of the spectral peak at 3 75 days is an atmospherically forced vertically propagating inertia gravity wave with a meridional structure given by the n 3 mode the corresponding equivalent depth is h 0 7 m and the vertical wavelength is 730 m the energy density estimated from the variance in the ies records is e 0 7 103 j m 2

equilibrium shoreline modelling of a high energy meso macrotidal multiple barred beach abstract 8 year time series of incident wave energy and monthly alongshore averaged beach surveys at the high energy meso macrotidal multiple barred truc vert beach are analysed we apply two behaviour oriented equilibrium shoreline models that relate the rate of cross shore shoreline displacement to the wave energy and the wave energy disequilibrium between the wave energy and the equilibrium wave energy that would cause no change to the present shoreline location the two models show similar skill results show that the equilibrium shoreline model concept works on meso macrotidal multiple barred beaches with similar skill when applied to non barred and or micro mesotidal beaches provided that a relevant shoreline proxy is used simulations show that truc vert beach responds predominantly at seasonal timescales rather than at individual storm frequency the first winter storms drive the most pronounced erosion events because both the wave energy disequilibrium and erosion change potential are large the best shoreline proxy at truc vert beach is the mean high water level where the inner bar and berm dynamics have little influence on the shoreline cross shore displacement implications for shoreline monitoring through video imagery on this type of beach are discussed results also reveal that the equilibrium shoreline concept can be extended to an equilibrium beach profile concept pending further improvements