laboratory investigation of dune erosion using stereo video abstract simple parameterizations of dune erosion are necessary for forecasting erosion potential prior to an oncoming storm dune erosion may be parameterized in terms of the elevation of the total water level composed of surge tide and wave runup above the dune base and period of exposure of the dune to waves in this work we test several versions of this model using observations from a large wave tank experiment designed to model a storm hydrograph and we develop a new method for acquiring the appropriate data with confidence intervals using stereo video techniques the stereo method results in observations of dune morphology at higher spatial and temporal resolutions than traditional survey methods allow resolution of the stereo technique was 0 1 m in the horizontal and 0 04 m in the vertical and errors in stereo observations were on the order of 0 02 to 0 08 m 1 to 2 pixels when compared with surveys a new method was developed to estimate confidence intervals on stereo observations when the unchanging dune top was repeatedly sampled the new confidence intervals encompassed 2 standard deviations of scatter about the mean dune surface 98 of the time observations from the stereo method were used to quantify wave runup and dune erosion we tested a variety of runup statistics based on a gaussian distribution of swash properties and found that the most predictive statistic for dune erosion was the 16 exceedance elevation above the dune base lower than the often used 2 exceedance value we found that the parameterization of runup was sensitive to the definition of beach slope and that the most accurate beach slope for predicting runup was through the region of the beach profile defined by the mean water level plus one standard deviation of swash the dune base retreated along a relatively constant trajectory that was a half of the initial beach slope finally a simple model for dune erosion was tested and found to reproduce 64 of the observed variance in dune erosion rate given known forcing at the dune and 49 of the observed variance in dune erosion rate given parameterized forcing integrating the simple model over time 93 of the observed dune retreat distance was reproduced given offshore forcing

the extreme 2013 2014 winter storms hydrodynamic forcing and coastal response along the southwest coast of england the southwest coast of england was subjected to an unusually energetic sequence of atlantic storms during the 2013 2014 winter with the 8 week period from mid december to mid february representing the most energetic period since at least 1953 a regional analysis of the hydrodynamic forcing and morphological response of these storms along the sw coast of england highlighted the importance of both storm and site specific conditions the key factor that controls the atlantic storm wave conditions along the south coast of southwest england is the storm track energetic inshore wave conditions along this coast require a relatively southward storm track which enables offshore waves to propagate up the english channel relatively unimpeded the timing of the storm in relation to the tidal stage is also important and coastal impacts along the macro tidal southwest coast of england are maximised when the peak storm waves coincide with spring high tide the role of storm surge is limited and rarely exceeds 1 m the geomorphic storm response along the southwest coast of england displayed considerable spatial variability this is mainly attributed to the embayed nature of the coastline and the associated variability in coastal orientation on west facing beaches typical of the north coast the westerly atlantic storm waves approached the coastline shore parallel and the prevailing storm response was offshore sediment transport many of these north coast beaches experienced extensive beach and dune erosion and some of the beaches were completely stripped of sediment exposing a rocky shore platform on the south coast the westerly atlantic storm waves refract and diffract to become southerly inshore storm waves and for the southeast facing beaches this results in large incident wave angles and strong eastward littoral drift many south coast beaches exhibited rotation with the western part of the beaches eroding and the eastern part accreting 2015 the authors earth surface processes and landforms published by john wiley sons ltd

an analytical model to predict dune erosion due to wave impact an analytical model is developed to calculate recession distance and eroded volume for coastal dunes during severe storms the transport relationship used in the model is based on wave impact theory where individual swash waves hitting the dune face induce the erosion combining this relationship with the sediment volume conservation equation describes the response of the dune to high waves and water levels four different data sets on dune erosion originating from the laboratory and the field were employed to validate the model and to determine the value of an empirical transport coefficient appearing in the analytical solutions the time evolution of dune recession observed in the different data sets was well described by the model but the empirical coefficient showed some variation between cases especially for the field data in practical applications of the model it is recommended to use a range of coefficient values to include an uncertainty estimate of calculated quantities such as recession distance and eroded volume

decadal scale variation in dune erosion and accretion rates an investigation of the significance of changing storm tide frequency and magnitude on the sefton coast uk abstract monitoring of frontal dune erosion and accretion on the sefton coast in northwest england over the past 50 years has revealed significant spatial and temporal variations previous work has shown that the spatial variations primarily reflect longshore differences in beach and nearshore morphology energy regime and sediment budget but the causes of temporal variations have not previously been studied in detail this paper presents the results of work carried out to test the hypothesis that a major cause of temporal variation is changes in the frequency and magnitude of storms surges and resulting high tides dune toe erosion accretion records dating from 1958 have been compared with tide gauge records at liverpool and heysham relatively high dune erosion rates at formby point 1958 1968 were associated with a relatively large number of storm tides slower erosion at formby and relatively rapid accretion in areas to the north and south occurred during the 1970 s and 1980 s when there were relatively few major storm tides after 1990 rates of dune erosion at formby increased again and dunes to the north and south experienced slower accretion during this period high storm tides have been more frequent and the annual number of hours with water levels above the critical level for dune erosion has increased significantly an increase in the rate of mean sea level rise at both liverpool and heysham is evident since 1990 but we conclude that this factor is of less importance than the occurrence of extreme high tides and wave action associated with storms the incidence of extreme high tides shows an identifiable relationship with the lunar nodal tidal cycle but the evidence indicates that meteorological forcing has also had a significant effect storms and surges in the eastern irish sea are associated with atlantic depressions whose direction and rate of movement have a strong influence on wind speeds wave energy and the height of surge tides however preliminary analysis has indicated only a modest relationship between dune erosion accretion rates and the north atlantic oscillation index

feedback between ridge and swale bathymetry and barrier island storm response and transgression abstract the shoreface of santa rosa island in northwest florida is characterized by a ridge and swale bathymetry that forces an alongshore variation in beach and dune morphology the alongshore variation in dune morphology in turn controls the modern island response to and recovery from tropical storms and hurricanes and is therefore an important control on island transgression with relative sea level rise field sampling and remote sensing are used in the present study to describe the geologic framework of santa rosa island and to elucidate on the origins of the shore attached ridge and swale bathymetry vibracores and seismic and gpr surveys were completed along 42 cross shore transects and 3 shore parallel transects to examine the structure of the 21 ridge and swale structures found along santa rosa island the shore parallel seismic surveys reveal strong near horizontal reflectors through the ridges at depths consistent with thick back barrier muds extracted from vibracores taken across and along the ridges near horizontal reflectors are identified in ground penetrating radar gpr surveys between the ridges and cuspate spits along the back barrier shoreline but are not present in the narrow sections of the island landward of the swales continuation of the seismic surveys in the back barrier also reveals near horizontal reflectors at the cuspate spits that are characterized by seagrass beds salt marsh and maritime forest consistent with the gpr survey there is an absence of horizontal reflectors between cuspate spits where the washover deposits extend to the back barrier shoreline it is argued that the ridge and swale bathymetry is a transgressive surface and the remnants of cuspate spits that are present along the back barrier shoreline in this respect the cuspate spits had to first develop along the back barrier shoreline and eventually evolve into the mud cored ridges as the island transgressed with relative sea level rise once the ridge and swale bathymetry emerged on the gulf of mexico shoreface it was able to reinforce the alongshore variation in dune height and storm response it is further argued that the cuspate spits are reinforced by the shoreface ridges through alongshore transport of sediment from adjacent washover fans although the ridge orientation suggests that the spits have migrated westward by 750 m in this respect the alongshore variation in beach and dune morphology on this island is the expression of this large scale feedback and suggests a top down model in which meso scale processes and landforms depend on the geologic context

modelling storm impacts on beaches dunes and barrier islands a new nearshore numerical model approach to assess the natural coastal response during time varying storm and hurricane conditions including dune erosion overwash and breaching is validated with a series of analytical laboratory and field test cases innovations include a non stationary wave driver with directional spreading to account for wave group generated surf and swash motions and an avalanching mechanism providing a smooth and robust solution for slumping of sand during dune erosion the model performs well in different situations including dune erosion overwash and breaching with specific emphasis on swash dynamics avalanching and 2dh effects these situations are all modelled using a standard set of parameter settings the results show the importance of infragravity waves in extending the reach of the resolved processes to the dune front the simple approach to account for slumping of the dune face by avalanching makes the model easily applicable in two dimensions and applying the same settings good results are obtained both for dune erosion and breaching

extreme erosion on high energy embayed beaches influence of megarips and storm grouping abstract megarips have long been recognised as an important yet poorly documented mechanism of beach erosion on high energy embayed beaches the persistence and cumulative effect of megarips during storm groups are described from three embayed beaches arrifana mt clerigo and amoreira exposed to high energy wave conditions in the mesotidal bedrock dominated southwestern coast of portugal morphological changes determined by topographic monitoring and supplemented by interpretation of digital imagery over two years revealed the development of storm induced megarips which exerted a major influence on beach erosion differences in megarip influence within and between beaches are related to embayment geometry and orientation which significantly influence the nearshore wave field rip location is topographically controlled being determined by alongshore variations in breaking wave height and obliquity along with interaction of wave driven circulation patterns and embayment nearshore topography moderate beach sand loss during individual storms was linked to the development of megarips with associated rip neck and feeder channels extreme erosion however occurred when megarips and feeder channels persisted during successive storms promoting continued erosion and seaward sediment export observations show that once initiated megarip channels persist for several months and continue to act as conduits for offshore sediment transport under non storm conditions the maintenance of such rip circulation systems driven by morphodynamic feedback reduces beach recovery ability until the rip neck and feeder channels are infilled

rip currents mega cusps and eroding dunes abstract dune erosion is shown to occur at the embayment of beach mega cusps o 200 m alongshore that are associated with rip currents the beach is the narrowest at the embayment of the mega cusps allowing the swash of large storm waves coincident with high tides to reach the toe of the dune to undercut the dune and to cause dune erosion field measurements of dune beach and rip current morphology are acquired along an 18 km shoreline in southern monterey bay california this section of the bay consists of a sandy shoreline backed by extensive dunes rising to heights exceeding 40 m there is a large increase in wave height going from small wave heights in the shadow of a headland to the center of the bay where convergence of waves owing to refraction over the monterey bay submarine canyon results in larger wave heights the large alongshore gradient in wave height results in a concomitant alongshore gradient in morphodynamic scale the strongly refracted waves and narrow bay aperture result in near normal wave incidence resulting in well developed persistent rip currents along the entire shoreline the alongshore variations of the cuspate shoreline are found significantly correlated with the alongshore variations in rip spacing at 95 confidence the alongshore variations of the volume of dune erosion are found significantly correlated with alongshore variations of the cuspate shoreline at 95 confidence therefore it is concluded the mega cusps are associated with rip currents and that the location of dune erosion is associated with the embayment of the mega cusp

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

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

morphology and facies of the alluvial fan sedimentation in the kangra valley himachal himalaya abstract a number of alluvial fans having an average width e w of 10 15 km and length n s of 8 15 km have been mapped using the landsat tm imageries on 1 250 000 scale in the kangra valley of himachal himalaya this important geomorphic zone of alluvial fans is confined between the foot of the dhauladhar range and the siwalik ridges these fans are gently sloping from north to south and are slightly dissected having distinct horizons of glacial glacio fluvial fluvial lacustrine and loessic sediments derived from the dhauladhar granitic complex dharamsala and siwalik formations during the glacial and interglacial climatic stages of the quaternary period the vertical lithological profiles of these fans show a dominance of gravelly nearly 60 facies along with other lithofacies associations representing a braided river depositional environment in general the thickness of fan sediments ranges between 90 and 120 m the vertical facies are subdivided into three main facies i e lower middle and upper fan facies showing distinct sediment characteristics the presence of glacial moraines and clay rich debris flow deposits is significant in the upper fan facies the middle fan facies is gravel dominated along with some interbedded sandy channel fill deposits whereas the lower fan facies is composed of sand silt and mud the genesis of these three fan facies is closely related with the uplift of the source area and climatic changes during the pleistocene period

controls on coastal dune morphology shoreline erosion and barrier island response to extreme storms abstract the response of a barrier island to an extreme storm depends in part on the surge elevation relative to the height and extent of the foredunes which can exhibit considerable variability alongshore while it is recognized that alongshore variations in dune height and width direct barrier island response to storm surge the underlying causes of the alongshore variation remain poorly understood this study examines the alongshore variation in dune morphology along a 11 km stretch of santa rosa island in northwest florida and relates the variation in morphology to the response of the island during hurricane ivan and historic and storm related rates of shoreline erosion the morphology of the foredune and backbarrier dunes was characterized before and after hurricane ivan using empirical orthogonal function eof analysis and related through canonical correlation analysis cca the height and extent of the foredune and the presence and relative location of the backbarrier dunes varied alongshore at discrete length scales of 750 1450 and 4550 m that are statistically significant at the 95 confidence level cospectral analysis suggests that the variation in dune morphology is correlated with transverse ridges on the inner shelf the backbarrier cuspate headlands and the historical and storm related trends in shoreline change sections of the coast with little to no dune development before hurricane ivan were observed in the narrowest portions of the island between headlands west of the transverse ridges overwash penetration tended to be larger in these areas and island breaching was common leaving the surface close to the watertable and covered by a lag of shell and gravel in contrast large foredunes and the backbarrier dunes were observed at the widest sections of the island the cuspate headlands and at crest of the transverse ridges due to the large dunes and the presence of the backbarrier dunes these areas experienced less overwash penetration and most of the sediment from the beachface and dunes was deposited within the upper shoreface it is argued that this sediment is returned to the beachface through nearshore bar migration following the storm and that the areas with larger foredunes and backbarrier dunes have smaller rates of historical shoreline erosion compared to areas with smaller dunes and greater transfer of sediment to the washover terrace since the recovery of the dunes will vary depending on the availability of sediment from the washover and beachface it is further argued that the alongshore pattern of dune morphology and the response of the island to the next extreme storm is forced by the transverse ridges and island width through alongshore variations in storm surge and overwash gradients respectively these findings may be particularly important for coastal managers involved in the repair and rebuilding of coastal infrastructure that was damaged or destroyed during hurricane ivan

beach response to a sequence of extreme storms abstract a sequence of daily beach surveys acquired over one month covering an area larger than 100 000 m 2 was analyzed to study morphological changes resulting from a cluster of storms the beach response was highly variable in both the cross and alongshore a cumulative storm effect was not observed despite one storm being characterized by a 10 year return period that had significant wave height h s of 8 1 m and a peak wave period t p of 17 s instead storms that can potentially cause significant erosion in terms of h s had a limited effect on the morphology because the large wave height was coupled to either neap tides normally incident short waves f 0 04 hz or low levels of infragravity 0 004 f

variability of shore and shoreline evolution shore and shoreline evolution both due to natural and human induced causes or factors can be variable over a wide range of different temporal and or spatial scales our capability to understand and especially predict this variability is still limited this can lead to misinterpretation of coastal change information which hampers informed decision making and the subsequent design and implementation of soft engineering interventions collecting and describing example observations of shore and shoreline variability is one way to support and improve such human intervention this paper describes causes and factors for the variability and the resulting possible evolutions of wave dominated shores and shorelines which are illustrated by a number of case studies the new element of this work is that the variability is described in terms of a range of different time and space scales which helps to structure such analysis however it is difficult to generalise the results for arbitrary situations especially on decadal time scales scientific and engineering improvements require more quantitative insight into the physical mechanisms behind the free and forced shore behaviour responsible for the variability

storm impact on the seasonal shoreline dynamics of a meso to macrotidal open sandy beach biscarrosse france abstract a three year dataset 2007 2010 of shoreline and sandbar positions derived from video observations of an open sandy beach biscarrosse france is analyzed to explore the impact of storms on the seasonal shoreline dynamics the results indicate that a clear seasonality is observed in the offshore significant wave height and in the occurrence of winter storm events that are defined as periods with significant wave height greater than 4 m lasting at least 12 h data indicate that the range of variation of the inner sandbar positions 120 m is two and a half times larger than the range of variation of the shoreline position correlation analyses suggest that the offshore conditions do not conclusively explain the position of the inner bar shoreline positions show a clear seasonal pattern displaying a stable position occurring in february and july providing evidence of seasonal recovery although analysis of storm activity indicates that the number and intensity of storms is highly variable over the three years the biscarrosse data show that rapid erosion can be observed also under moderate conditions and that beach recovery after the storm season can be relatively rapid

the impact of the 2009 10 el nino modoki on u s west coast beaches 1 high resolution beach morphology data collected along much of the u s west coast are synthesized to evaluate the coastal impacts of the 2009 10 el nino coastal change observations were collected as part of five beach monitoring programs that span between 5 and 13 years in duration in california regional wave and water level data show that the environmental forcing during the 2009 10 winter was similar to the last significant el nino of 1997 98 producing the largest seasonal shoreline retreat and or most landward shoreline position since monitoring began in contrast the 2009 10 el nino did not produce anomalously high mean winter wave energy in the pacific northwest oregon and washington although the highest 5 of the winter wave energy measurements were comparable to 1997 98 and two significant non el nino winters the increase in extreme waves in the 2009 10 winter was coupled with elevated water levels and a more southerly wave approach than the long term mean resulting in greater shoreline retreat than during 1997 98 including anomalously high shoreline retreat immediately north of jetties tidal inlets and rocky headlands the morphodynamic response observed throughout the u s west coast during the 2009 10 el nino is principally linked to the el nino modoki phenomena where the warm sea surface temperature sst anomaly is focused in the central equatorial pacific as opposed to the eastern pacific during a classic el nino featuring a more temporally persistent sst anomaly that results in longer periods of elevated wave energy but lower coastal water levels

alongshore variation in the morphology of coastal dunes implications for storm response abstract the geomorphological impact of an extreme storm on a barrier island tends to be modeled using a single cross shore transect and dependent only on the elevation of the storm surge relative to the height of the dune the foredune line however is rarely uniform and can exhibit considerable variation in height and width alongshore at a range of length scales the purpose of this modeling study is to determine how alongshore variations in dune height affect barrier island response to extreme storms the mike21 wave and current model is used to predict the morphological response of matagorda peninsula texas in response to storm surges associated with dune scarping washover and inundation the extent and degree of dune scarping washover and shoreline erosion is predicted for each storm scenario with respect to the base morphology of the island and low pass filtered forms in which small scale topographic variance is removed results suggest that small variations in the height of an otherwise alongshore uniform foredune act as overwash conduits and are unstable leading to a more variable duneline that is more susceptible to change by subsequent storms the vertical development of the washover gaps in the duneline is limited and eventually replaced by a lateral expansion that erodes adjacent dunes and leads to a more uniform island elevation the loss of island elevation is greater for the original unfiltered alongshore profile but relatively uniform duneline is the most unstable and exhibits the greatest morphological change the different alongshore profile responses suggest that the impact of an extreme storm is sensitive to initial conditions and specifically the pre storm variability of the crest elevation alongshore this in turn suggests that the evolution of barrier islands is dependent on storm history until the variability in the duneline elevation reaches a maximum further study of barrier island response to storm sequencing with and without post storm recovery however is required to understand the evolution and form for the prototype island

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

impact of the winter 2013 2014 series of severe western europe storms on a double barred sandy coast beach and dune erosion and megacusp embayments abstract the winter of 2013 2014 was characterized by a striking pattern of temporal and spatial extreme storm wave clustering in western europe the 110 km long gironde coast sw france was exposed to the most energetic wave conditions over the last 18 years the period was outstanding in terms of the available energy to move sediment and cause large scale erosion with the 2 month average significant wave height hs exceeding 3 6 m just below the 0 95 quantile and 4 distinct 10 year return period storms with hs 9 m these storm waves caused unprecedented beach and dune erosion along the gironde coast including severely damaged sea defences at the coastal towns at the end of the winter dune erosion scarp height was highly variable alongshore and often exceeded 10 m megacusp embayments were observed along the gironde coast with an average alongshore spacing of 1000 m in the south progressively decreasing to 500 m in the north with an average cross shore amplitude of 20 m while beach megacusps were previously observed to systematically couple to the inner bar along the gironde coast during low to moderate energy wave conditions severe storm driven megacusp embayments cutting the dune were found to be enforced and coupled to the outer crescentic bar a detailed inspection of the 1500 m long bimonthly topographic surveys of truc vert beach shows that in early january 2014 the outstanding shore normal incident storm swell hercules with hs and peak wave period tp peaking at 9 6 m and 22 s respectively triggered the formation of a localized megacusp embayment with the erosion scarp height exceeding 6 m in its centre where the dune retreat reached 30 m the subsequent storms progressively smoothed the megacusp by the end of the winter mostly through severe erosion of the megacusp horns because of the very long period 16 s

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

beach dune morphological relationships and erosion accretion an investigation at five sites in england and wales using lidar data abstract the critical relationships between beach and nearshore parameters and the erosion accretion status of frontal dunes have been investigated using lidar data complemented by data obtained from conventional topographic and bathymetric surveys at five dune systems in england and wales morphometric parameters calculated from the lidar data demonstrate the presence of a general relationship between beach morphology dune morphology and erosion accretion eroding dunes were found to be associated with narrower steeper beaches whilst accreting dunes were associated with wider low angle beaches however the critical beach width mean slope angle separating eroding dunes from stable or accreting dunes was found to vary between sites at any given site changes in beach width slope over time can be used to provide an early warning of changes in frontal dune erosion accretion behaviour

seasonal accretion and erosion patterns of a microtidal sandy beach monthly elevation surveys of a 1 5 km stretch of coast at noordwijk the netherlands were made 1 to quantify seasonal variability in the cross shore position of high mean and low tide contours beach width and beach volume and 2 to examine the dependence of the variability on the offshore wave characteristics additionally daily cross shore positions of contours obtained from video images were used to examine daily beach response to wave characteristics between successive surveys the more intense and frequent storm events in winter than in summer resulted in a seasonal change from a wide beach with a small volume at the end of winter to a narrow large volume beach in summer the seasonal pattern in beach width resulted from the cross shore sediment exchange between the supratidal and lower intertidal part of the beach in contrast to the coupling between beach behaviour and wave characteristics on a seasonal scale beach variability between successive surveys was unrelated to day to week averages of the preceding offshore wave conditions partly due to the precise timing of a storm relative to the two survey moments moreover daily variability determined from the video images showed that differing antecedent morphology to storms and alongshore variations in beach morphology contributed to spatially and temporally variable beach response

extreme wave activity during 2013 2014 winter and morphological impacts along the atlantic coast of europe studies of coastal vulnerability due to climate change tend to focus on the consequences of sea level rise rather than the complex coastal responses resulting from changes to the extreme wave climate here we investigate the 2013 2014 winter wave conditions that severely impacted the atlantic coast of europe and demonstrate that this winter was the most energetic along most of the atlantic coast of europe since at least 1948 along exposed open coast sites extensive beach and dune erosion occurred due to offshore sediment transport more sheltered sites experienced less erosion and one of the sites even experienced accretion due to beach rotation induced by alongshore sediment transport storm wave conditions such as were encountered during the 2013 2014 winter have the potential to dramatically change the equilibrium state beach gradient coastal alignment and nearshore bar position of beaches along the atlantic coast of europe

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

nearshore shore oblique bars gravel outcrops and their correlation to shoreline change abstract this study demonstrates the physical concurrence of shore oblique bars and gravel outcrops in the surf zone along the northern outer banks of north carolina these subaqueous features are spatially correlated with shoreline change at a range of temporal and spatial scales previous studies have noted the existence of beach surf zone interactions but in general relationships between nearshore geological features and coastal change are poorly understood these new findings should be considered when exploring coastal zone dynamics and developing predictive engineering models the surf zone and nearshore region of the outer banks is predominantly planar and sandy but there are several discrete regions with shore oblique bars and interspersed gravel outcrops these bar fields have relief up to 3 m are several kilometers wide and were relatively stationary over a 1 5 year survey period however the shoreward component of the bar field does exhibit change during this time frame all gravel outcrops observed in the study region a 40 km longshore length were located adjacent to a shore oblique bar in a trough that had width and length similar to that of the associated bar seismic surveys show that the outcrops are part of a gravel stratum underlying the active surface sand layer cross correlation analyses demonstrate high correlation of monthly and multi decadal shoreline change rates with the adjacent surf zone bathymetry and sediment distribution regionally areas with shore oblique bars and gravel outcrops are correlated with on shore areas of high short term shoreline variability and high long term shoreline change rates the major peaks in long term shoreline erosion are onshore of shore oblique bars but not all areas with high rates of long term shoreline change are associated with shore oblique bars and troughs

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

a simple model for the spatially variable coastal response to hurricanes abstract the vulnerability of a beach to extreme coastal change during a hurricane can be estimated by comparing the relative elevations of storm induced water levels to those of the dune or berm a simple model that defines the coastal response based on these elevations was used to hindcast the potential impact regime along a 50 km stretch of the north carolina coast to the landfalls of hurricane bonnie on august 27 1998 and hurricane floyd on september 16 1999 maximum total water levels at the shoreline were calculated as the sum of modeled storm surge astronomical tide and wave runup estimated from offshore wave conditions and the local beach slope using an empirical parameterization storm surge and wave runup each accounted for 48 of the signal the remaining 4 is attributed to astronomical tides indicating that wave driven process are a significant contributor to hurricane induced water levels expected water levels and lidar derived measures of pre storm dune and berm elevation were used to predict the spatially varying storm impact regime swash collision or overwash predictions were compared to the observed response quantified using a lidar topography survey collected following hurricane landfall the storm averaged mean accuracy of the model in predicting the observed impact regime was 55 4 a significant improvement over the 33 3 accuracy associated with random chance model sensitivity varied between regimes and was highest within the overwash regime where the accuracies were 84 2 and 89 7 for hurricanes bonnie and floyd respectively the model not only allows for prediction of the general coastal response to storms but also provides a framework for examining the longshore variable magnitudes of observed coastal change for hurricane bonnie shoreline and beach volume changes within locations that experienced overwash or dune erosion were two times greater than locations where wave runup was confined to the foreshore swash regime during hurricane floyd this pattern became more pronounced as magnitudes of change were four times greater within the overwash regime than in the swash regime comparisons of pre storm topography to a calm weather survey collected one year after hurricane floyd s landfall show long term beach volume loss at overwash locations here the volume of sand eroded from the beach was balanced by the volume of overwash deposits indicating that the majority of the sand removed from the beach was transported landward across the island rather than being transported offshore in overwash locations sand was removed from the nearshore system and unavailable for later beach recovery resulting in a more permanent response than observed within the other regimes these results support the predictive capabilities of the storm scaling model and illustrate that the impact regimes provide a framework for explaining the longshore variable coastal response to hurricanes

tourmaline bearing rocks in the singhbhum shear zone eastern india evidence of boron infiltration during regional metamorphism frozen in reaction textures combined with mineral chemistry of tourmaline bearing metamorphic assemblages provide valuable information about fluid rock interaction during orogenesis tourmaline occurs in four distinct mineralogical associations in the singhbhum shear zone ssz of the precambrian east indian craton the tourmaline bearing rocks are associated intimately with pelitic to psammopelitic and quartzofeldspasthic rocks including meta granite the rocks were affected by two sets of folding f1 and f2 and ductile shearing associated with f1 during ca 1 6 1 8 ga tectonic activity in this belt quantitative geothermobarometry and the stability relations of the metamorphic assemblages developed in the pelitic rocks establish the presence of two episodes of metamorphism a prograde m1 event that culminated at 480 40 c 6 4 0 4 kbar and an m2 event that caused retrogression of the m1 assemblages field and petrographic observations in combination with data on chemical composition of tourmaline indicate three stages of tourmaline growth the earliest stage is represented by pretectonic pre metamorphic greenish yellow tourmaline cores in the tourmalinite from the surda area association a the textural relations demonstrate that in the second stage greenish yellow cores of oscillatory zoned tourmaline in the metagranite albite quartz biotite chlorite muscovite apatite magnetite association c very fine tourmaline grains in muscovite schist muscovite quartz association b and greenish yellow cores of tourmaline in biotite muscovite schist biotite muscovite magnetite chlorite apatite quartz association d crystallized during the f1 m1 events post tectonic greenish blue tourmaline belonging to the third stage replaces the earlier tourmaline grains along their margins and cracks compositionally tourmalines of all four associations fall in the alkali group most of the data fall in the dravite field with a few analyses straddling the boundary between schorl and dravite an abrupt compositional change was noted across the different color zones in the tourmaline grains this change is explained by one or more of the coupled substitutions al nar 1 car naal 1 and mg fe 1 where r mg fe2 mn integrating the field petrographic and phase compositional data it has been demonstrated that tourmaline growth in the second and third stages was induced by infiltration driven b metasomatism during prograde metamorphism of the rocks deep seated magma was the source of the b bearing hydrothermal fluid

new insights into embayed beach rotation the importance of wave exposure and cross shore processes although embayed beach rotation has been viewed and modeled as an alongshore sediment transport process acting on a uniform beach profile recent research suggests a more complex response whereby alongshore variability in cross shore sediment fluxes may be more significant this study utilizes 5 years of fully three dimensional beach surveys at narrabeen collaroy beach se australia to quantify the control of alongshore nonuniform wave exposure and cross shore processes on embayed beach rotation empirical orthogonal function analysis of the alongshore variability in subaerial beach volume width and berm slope confirms that the dominant mode of subaerial beach variability is an onshore offshore sediment exchange that is strongly controlled r 0 8 by the alongshore gradient in breaker wave height and coincides with a uniform flattening steepening of the berm slope a secondary rotation like signal is observed in both the subaerial beach volume width data and significantly the berm slope this inverse flattening steepening of the berm slope between beach extremities is most likely a proxy for differing cross shore processes within the surf zone between the exposed and sheltered ends of the embayment particularly with regards to dissipation of storm wave energy by offshore sandbars and beach recovery following storms analysis of the corresponding wave data reveals two distinct time scales of wave forcing characteristic of short term erosion and longer term recovery processes a new conceptual model is presented of three differing modes of embayed beach rotation with the newly identified beach rotation mode controlled by offshore sandbars considered of particular importance at embayments where headland sheltering of oblique waves is pronounced