modelling shoreface profile evolution current knowledge of hydro sediment and morpho dynamics in the shoreface environment is insufficient to undertake shoreface profile evolution modelling on the basis of first physical principles we propose a simple panel type model to map observed behaviour the internal dynamics are determined by slope dependent wave induced cross shoreface transports while the external driving factors are lateral sediment supply and sea level rise this model concept is tested with reasonable success against the observed behaviour of the central holland coast considering two hindcast periods one covering the evolution over the last century the other the subboreal subatlantic evolution a limitation of this model is that the cross shoreface dynamics are solely steered by the variations of shoaling short waves since a variety of other wave and current dynamics may be expected to be present in the coastal boundary layer it may well be that the effects of the mechanisms and conditions which are not represented are hidden in the coefficients of the sediment transport formula this limits the accuracy of the coefficients as used and our findings should be considered as an order of magnitude estimate only indeed behaviour oriented modelling implies that generalization of results to arbitrary situations and conditions is not straightforward yet we expect that some of the conclusions are more generally applicable this concerns the substantiation of the assumption that the upper shoreface responds on a much smaller time scale than the lower shoreface and the idea that the shoreface profile is not always and everywhere in equilibrium with its forcing a worthwhile observation from the holland coast application is that the bottom slope effect on the transport is only important at geological time scales the profile evolution at the engineering time scales say 10 to 100 years is effectively quasi static in that there is no feedback between the long term averaged transport and the state of the profile this implies that at these smaller scales the profile changes can be predicted on the basis of a static sediment balance this does not mean that the gravitational downslope transport is unimportant as a physical phenomenon in coastal profile evolution it is only unimportant if a highly aggregated model like this is applied at relatively short time scales

modelled nearshore sediment transport in open water conditions central north shore of prince edward island canada the central north shore of prince edward island comprises embayments separated by subtle headlands that may constrain nearshore sediment transport the study area includes two such embayments informally known as brackley and tracadie bights both of which are sand rich onshore and sand starved between 20 and 50 m water depth storm winds and waves from the northwest and northeast are common in autumn and winter the hydrodynamic model delft3d is used to simulate waves currents water levels and sediment transport in brackley and tracadie bights during 23 autumn seasons between 1955 and 2005 when compared with wave and current measurements from a field experiment in the autumn of 1999 the model successfully simulates conditions during storms and fair weather periods results from the simulations show that in autumn the weighted mean direction of transport is to the southeast 133 bedload transport is directed onshore to the south 170 and suspended load is directed offshore to the northeast 67

mass flux and undertow in a surf zone abstract the mass of water carried shoreward by the breaking waves in a surf zone will in a two dimensional situation be compensated by a seaward return flow the undertow it is shown that the undertow is driven by the local difference between radiation stress and the set up pressure gradient which only balance each other in average over the depth turbulent shear stresses are required to maintain a steady situation comparison with measurements confirms the theoretical results

suspended sediment transport and nearshore bar formation on a shallow intermediate state beach abstract estimates of cross shore suspended sediment flux were obtained during a 3 day storm event on the north sea coast of denmark the suspended sediment flux estimates were correlated with volumetric beach change as registered at 28 permanently deployed survey rods crossing the intertidal beach and inner surf zones during this storm a nearshore bar initially migrated onshore and welded to the beach face at its updrift end subsequently a new bar formed on the seaward slope of the former suspended sediment transport recorded using optical backscatter sensors and electromagnetic current meters corresponded well qualitatively with the morphological evolution indications are that such measurements may account for a significant fraction of the actual cross shore sediment transport the onshore migration of the nearshore bar was the result of onshore directed mean currents associated with a cell circulation renewed bar formation took place when this circulation was locally replaced by an offshore directed mean current undertow suspended sediment transport due to oscillatory waves at incident and infragravity frequencies was generally subordinate to the mean transport

spatial analysis of sand dunes with a new global topographic dataset new approaches and opportunities on june 29 2009 version 1 of the aster gdem advanced spaceborne thermal emission and reflection radiometer global digital elevation model was made available at no cost or restrictions to users worldwide via electronic download the aster gdem provides expanded spatial coverage and better resolution than other global digital elevation models dems in this paper we demonstrate how the aster gdem provides new opportunities for investigating large aeolian sand dunes in three dimensions two dune specific spatial analysis methods are presented to illustrate potential applications of these data for discriminating dune generations and quantifying spatial variations of sediment supply moreover we review how existing and emerging fields of dune pattern analysis and simulation modeling will be able to make significant advances through application of these data potentially leading to future progress in studies of dune morphodynamics environmental controls and paleoenvironmental reconstructions copyright 2010 john wiley sons ltd

problems of scale in the modeling and interpretation of coastal dunes abstract coastal dune systems are studied at time scales from seconds to millennia and space scales from millimeters to kilometers present approaches to the study of coastal dunes make it difficult to integrate models and interpretations of these systems over these scale ranges and arrive at reasonable conclusions it is argued that identification of key controls on dune development measurement of those controls and synthesis of data describing past and present conditions and used as calibration points will improve the viability of coastal dune models theoretical and empirical advances are necessary to improve the reliability of predictions across a range of geomorphological scales attempts at linking theoretical systematic models process synoptic measurement and historical or paleoenvironmental synthetic approaches make explicit the recognition that at time scales of more than a few hours and space scales greater than a few hundred meters deterministic models become unstable vis a vis prototype environments process climatologies provide one means to link process based work with broader scaled analysis as scales increase such climatologies will become less appropriate as the data become less reliable or as the systems change or as the scales become too large relative to the process record lengths in these conditions specific data i e samples representing points in time and space become check points for calibrating models it should be possible ideally to integrate both up and down time and space scales this is not yet possible

controls on the formation of coastal ventifacts abstract ventifacted boulders are present within the intertidal zone of a mixed sand and boulder beach in gweebarra bay northwest ireland the boulders show features typical of wind abrasion by sand including polished surfaces pits and grooves orientation of ventifact keels was measured and direction of prevailing winds responsible for ventifaction was inferred from a sample of 50 boulders in each of two adjoining locations on the beach 30 m apart the keel orientations and inferred wind direction are both strongly clustered but results from each location differ by 90 from one another and neither corresponds closely to the present day regional wind regime since wind flow patterns were not significantly different during the little ice age when the ventifacts were likely formed the orientation of ventifact keels cannot be used uncritically as in many studies as a proxy record of prevailing wind direction it is likely that ventifact development in gweebarra bay was controlled by sediment availability rather than by wind direction

biogeomorphology and landscape evolution the problem of scale abstract vegetation may vary continuously and rapidly while landforms sometimes vary episodically and relatively slowly this disparity in temporal scales creates scale linkage problems in dealing with landform vegetation interactions four theoretical approaches for coping with these issues are outlined and illustrated via applications to problems arising from fieldwork on the coastal plain of north carolina the first approach the transient form ratio is used to determine whether ecosystems and geomorphic environments preserved in pleistocene stratigraphy represent stable landform ecosystem combinations which should reflect landform and vegetation responses to sea level rise the second the information criterion is applied to estimate the appropriate time steps for simulation modelling and appropriate spatial resolutions for field studies of vegetation effects on soil thickness in coastal plain uplands the abstracted systems argument the third approach is used to show that alluvial sedimentation and floodplain ecological dynamics cannot be considered independently in studies of floodplain system response to post european settlement finally ratios of relaxation times and durations suggest that changes in upland erosion regimes associated with historical devegetation are best treated as a singular perturbation in the context of quaternary landscape evolution

simulation of large scale coastal change using a morphological behaviour model abstract quantitative simulation of large scale coastal behaviour lscb is possible using a model based only on principles of sand mass conservation and geometric rules for shoreface and active sand body morphology dynamic processes are subsumed into a set of parameters that define the geometry of the active cross shore profile which in turn can represent an entire coastal cell the parameters together with a set of local behaviour rules governing adjustments at discrete points along the profile provide a simple formulation that is constrained by sediment mass balance to yield emergent numerical solutions for profile kinematics the emergent qualities of this shoreface translation model are exemplified in simulation experiments on changes to sand deposits on the southeastern australian coast and shelf during the post glacial marine transgression in another example the model is used to simulate lscb over engineering time scales at an idiosyncratic site both examples illustrate the over riding importance of small residual sand movements that accumulate through time to cause lscb in comparison to gross sand movements the residuals are too small to measure directly or predict on the basis of available theory exploratory inverse simulation provides a quantitative method for side stepping these limitations the shoreface translation model therefore is used as a tool to explore possible forms of coastal behaviour through an approach that incorporates available data along with theoretical considerations validation is not strictly possible for this type of inverse approach so the degree to which a simulation reproduces observed features in nature is a measure of its success

decadal and seasonal development of embryo dunes on an accreting macrotidal beach north lincolnshire uk embryo dunes are often ephemeral but can develop to become established coastal foredunes in 2001 a patch of embryo dunes 13 11 m2 appeared on a beach in north lincolnshire uk and had expanded to over 3600 m2 by 2011 the rate of expansion is linked to storm occurrence where expansion is slowed during years with a higher incidence of storm surges from july 2009 october 2010 seasonal changes in dune field topography were determined using terrestrial laser scanning tls data vegetation is important in the development of embryo dunes but can cause errors in tls data tests evaluating the impact of vegetation on the tls data suggest the minimum elevation value from the tls point cloud within a 0 05 m grid cell gives a good approximation of the ground surface digital elevation models dems of the dunes constructed using filtered data showed the embryo dunes underwent a classic seasonal cycle of erosion during the winter and accretion during the summer for example from october 2009 to april 2010 over 375 m3 of sediment was eroded from the dunes whereas during spring and summer 2010 the dune field gained over 600 m3 of sand the overall magnitude of change in dune height and volume from season to season exceeded the errors associated with the construction of the dem from the tls data and the vegetation filtering process which suggests tls can be useful for documenting topographic change in vegetated dunes after 10 years the patch of embryo dunes is still expanding but has not yet merged with more established foredunes to landward aeolian process measurements indicate that at present the embryo dunes do not prevent sand from reaching the foredunes however the rate of foredune progradation has slowed concurrently with the expansion of the embryo dune field copyright 2013 john wiley sons ltd

wave driven sediment transport and beach dune dynamics in a headland bay beach abstract this paper presents a comprehensive study of wave refraction wave and wind driven sediment transport foredune development and holocene barrier evolution over a variety of time scales at mocambique beach santa catarina state southern brazil the motivation for this study was to examine the relationships between estimated wave driven sediment transport medium and long term aeolian transport foredune development and holocene barrier volumes and morphology an analysis of 2 years of wave rider data for the region shows two well defined peaks of frequencies one of swell waves from the south with a period of 12 s and another peak of sea waves from east northeast with a period of 7 s longshore sediment transport rates were calculated using high resolution hindcast wave data for the south atlantic ocean which was calibrated by the measured buoy data the dominant southerly waves drive a longshore gradient in wave energy from south to north and nearshore surf zone sediment transport increases from south to north beach grain size is fine in both the south and north and medium in the center the combination of grain size and wave energy variations creates a marked alongshore variation in surf zone beach types ranging from low energy dissipative in the south moderate energy intermediate in the central area to moderate to high energy dissipative in the north estimates of aeolian sediment transport volumetric changes in foredune deposition and total holocene dunefield volumes were also calculated results indicate that the morphological behavior of the foredune profiles reflects the gradients of longshore sediment transport and the exposure to wind energy and aeolian sediment delivery with a maximum of sediment volume and transport towards and in the central part and northern end of the barrier holocene 0 7000 years barrier volumes vary along the embayment mimicking the trends in both calculated wave and wind driven sediment transport the short and hesp 1982 model was more suitable in predicting the long term holocene barrier evolution than the size and volume of the foredune the combination of wide beach high energy dissipation maximum sediment supply and high exposure to strong onshore winds is found in the northern end of the embayment where holocene subaerial barrier volumes are at a maximum overall this study proves that foredune development is closely related to wind exposure wave energy and gradients of longshore sediment transport and that dunefield development reflects the increase downdrift in potential sediment supply from the southern to the northern end of the beach and the change alongshore from low energy dissipative through intermediate to high energy dissipative beach surf zone environments this paper significantly extends previous models of beach and dune interactions in that it i actually determines wave driven sediment transport for various sections of a long embayment ii relates those transport patterns to surf zone beach morphodynamic types and variations in alongshore sediment patterns and iii correlates foredune volumes and holocene barrier volumes which reflect proxy holocene onshore transport rates with wave driven sediment transport rates

sediment transport on dissipative intermediate and reflective beaches abstract in this paper we review and synthesize field measurements of suspended sediment transport on the shoreface of dissipative intermediate and reflective beach states the morphodynamic beach state continuum was originally established in the 1970s but at the time only hydrodynamic processes and morphologies in these various states were described since the early 1980s when sensors capable of resolving suspended sediment concentration at intra wave time scale became available many studies have examined suspended sediment transport by waves and currents on the shoreface the synthesis of this work shows that the two end states in the morphodynamic continuum which are the dissipative and reflective states exhibit relatively small rates of cross shore sediment transport and weak gradients in that transport which both ensure that the nearshore morphology is relatively stable the intervening intermediate beach states typically exhibit prominent bar topographies and in these states strong morphodynamic feedbacks between hydrodynamic processes and morphology create locally large transport rates and sharp transport gradients which is the reason for the dynamic nature of these beach states transport processes driving sediment onshore and offshore within beach states are discussed as well as the transport processes responsible for state transitions

divergent response of an intertidal swash bar this paper examines the processes responsible for the morphodynamics of an intertidal swash bar at skallingen denmark during seven successive storms one with a large surge of 3 02 m dnn during this period a subtidal bar migrated landward onto the foreshore and continued to migrate across the intertidal zone as a swash bar the onshore migration of the inner subtidal bar resulted from the erosion of sediment from the upper foreshore and dune ramp during the large storm surge that was transported seaward causing the landward displacement of the bar through accretion on the landward slope the magnitude and direction of suspended sediment transport within the intertidal zone and more specifically at and close to the crest of the swash bar varied with the ratio of both the significant hs and average havg wave heights to the water depth hcr at the swash bar crest the local depth minimum the transition between onshore and offshore suspended sediment transport was associated with the average wave of the incident distribution breaking on the swash bar crest havgh 0 33 while the onshore directed transport was largest at infragravity frequencies sediment resuspension was best explained by the skewed accelerations under the surf bores offshore transport was dominated by the cross shore mean currents undertow that developed when the significant wave of the distribution broke on the swash bar crest hsh 0 33 and weakened as the average wave of the distribution started to break at the crest havgh 0 33 and the surf zone approached saturation in contrast to subtidal bars the swash bar at skallingen exhibited a divergent behaviour with respect to the cross shore position of the breaker zone migrating onshore when the average wave broke seaward of the crest and migrating offshore when the average wave broke landward of the crest copyright 2006 john wiley sons ltd

field observations on the morphodynamic evolution of a low energy rip current system abstract a field experiment was conducted at palm beach nsw australia to investigate morphodynamic relationships operating within a rip current system during a near complete sequence of beach state evolution under decreasing energy conditions observations and measurements were obtained from nearshore surveys multiple dye releases oblique photographs and the deployment of various combinations of nine ducted impellor flow meters and five pressure sensors over a seven day period in rip and feeder channels the dataset provides a unique opportunity to assess and quantify aspects of the accretionary model of wright and short mar geol 56 1984 93 118 for intermediate beaches the morphology of the main rip channel exhibited distinct sequential adjustments with a narrowing of channel width an increase in channel depth a reduction in the cross sectional area available for rip flow and an increase in morphological relief rip flow velocity increased during the observed evolution and was also modulated by the tide experiencing maximums at low tide and minimums at high tide morphologic and kinematic adjustments of the rip system were most pronounced during the transition to a transverse bar and rip state the existence of a dominant feeder in a twin feeder and rip system contributed to the migration and establishment of a rip head over the seaward slope of the opposite longshore bar net erosion in the rip channel was balanced by net deposition in the feeder channels and bar crests and qualitative observations suggest that this rip head bar both receives transported sediments from the rip channel and contributes sediments to the ongoing accretion of the beach system a direct relationship was found to exist between rip morphology and flow with rip velocity increasing as cross sectional rip channel area decreases and these results are incorporated in a conceptual modification of the model of wright and short the results of this study are restricted to a subset of commonly occurring beaches but show that accretionary beach state evolution on intermediate beaches is indeed characterised by an increase in rip current velocity the nature of which can be linked to morphologic control in addition the rip head bar is identified as a potentially key component of low energy rip system evolution

aeolian sediment transport and morphologic change on a managed and an unmanaged foredune sediment transport and short term morphologic change were evaluated at a site where sand fences are deployed and the beach is raked managed site and a site where these human adjustments are not practiced unmanaged site data were gathered across the seaward portion of a low foredune when winds blew nearly shore normal at mean speeds 8 9 to 9 3 m s 1 data from traps revealed sediment transport rates at unvegetated portions of the foredune crest 40 2 to 43 5 kg m 1 h 1 were greater than on the backshore 4 9 to 11 2 kg m 1 h 1 due to onshore decreases in surface moisture and speed up of the wind passing over the foredune data from erosion pins indicate sediment input to the dune was 1 48 m3 m 1 alongshore at the managed site and 1 25 m3 m 1 at the unmanaged site the unmanaged site had deposition at the dune toe erosion at mid slope and deposition at the crest deposition occurred at mid slope on the managed site near a partially buried 0 58 m high fence with a porosity of about 65 deposition at partially buried wrack on the upper backshore and dune toe at the unmanaged site was about twice as great as deposition in this zone at the managed site results indicate that 1 the seaward slope of the foredune can be a more important source of sand to the lee of the crest than the beach 2 wrack near the toe can decrease transport into the foredune 3 a scour zone can occur on the foredune slope above the wrack line 4 a fence placed in this location can promote deposition and offset scour but fences can restrict delivery of sediment farther inland evaluation of alternative configurations of fences and strategies for managing wrack is required to better determine the ways that humans modify foredunes copyright 2012 john wiley sons ltd

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

process based one dimensional model for cyclic longshore bar evolution abstract a wave averaged process based one dimensional model for beach profile change was developed to predict the cyclic evolution of longshore bars the cross shore sediment transport was assumed to be composed of suspended load due to wave breaking and bed load due to velocity skewness acceleration skewness and beach slope the model s performance was investigated using the beach profile data obtained every weekday during a 12 year period from 1989 to 2000 along a 400 m long pier at the hazaki oceanographical research station located on the hasaki coast of japan where the mean duration of bar evolution is approximately 1 year the model was unable to reproduce bar development from a rather flat profile possibly because some sediment movement process was missing in the model however the model calibrated with a 1 year data set including the bar evolution cycle consisting of bar generation seaward migration decay and new bar generation can be used to predict the first cycles of bar evolution at hasaki

alongshore variation in foredune height in response to transport potential and sediment supply south padre island texas abstract the height and extent of coastal dune development can exhibit considerable variability over short distances leading to variable storm impact alongshore the source of this variation is not well understood in general and in many cases is not easily explained by models that ascribe dune height and development to regional variations in sediment availability and foreshore slope in this paper lidar data collected in 2000 and 2005 from south padre island texas are used to characterize the alongshore variation in dune morphology and to identify how the variation is related to foreshore morphology and nearshore state results of cross wavelet analysis suggest that foredune height exhibits a statistically significant coherence with the surf similarity parameter at length scales of 1300 of 2300 m the resulting variation in beach state alongshore from intermediate to dissipative is the consequence of wave refraction and focusing by transverse ridges on the inner shelf dune height reaches a local maximum approximately halfway between the more intermediate and dissipative sections of the coast where the volume of sediment in the backshore and in the foreshore bars are also at a maximum the greater elevation of the foreshore and backshore also provides a wider fetch and potential for aeolian transport during the storm surge that tends to accompany storm winds it is argued that the variation in dune morphology is not strictly the result of transport limitations as suggested by the fetch model but rather depends on the alongshore coincidence of transport potential with an available supply of sediment in the backshore and on the foreshore

shoreface sand supply to beaches the possibility of sand supply from the shoreface to beaches was evaluated based on a variety of methods involving field data and modeling results obtained from five coasts on three continents representing a wide range of coastal environments the field data include wave current measurements historical seabed soundings and geological surveys cross shore transport estimates from modeling on the annual time scale were compared against scaled down inferences from the seabed change and geological data the results are all consistent with there being net onshore transport over the long term from the lower shoreface to beaches in each of the environments these environments typify settings that occur commonly probably predominantly along the world s coasts so net shoreface sand supply to beaches may be a widespread and common but little appreciated factor in coastal stability the effect of this net supply is to offset other factors causing shoreline recession such as positive gradients in littoral transport moreover shoreline progradation occurs if sand supply from the shoreface dominates over littoral sediment losses implications are clearly significant for coastal engineering and coastal management despite the processes not being immediately apparent long term shoreface sand supply to beaches is masked by more rapid cyclical changes rates of shoreface sand supply to beaches indicated from various lines of evidence are typically on the order of 10 0 m 3 a 1 per meter of shoreline this volume corresponds to a lowering of the shoreface by only a few grain diameters per year

storms shoreface morphodynamics sand supply and the accretion and erosion of coastal dune barriers in the southern north sea abstract the coast of the southern north sea is bound by dune barriers that have developed adjacent to a shallow storm and tide dominated shoreface comprising numerous shore parallel to sub shore parallel tidal sand banks the banks evolve under the joint control of tide wave and wind induced shore parallel currents which tend to stretch them eventually leading to bank division and to shoaling and breaking storm waves which tend to drive them ashore the banks thus modulate the delivery of storm wave energy to the coast redirect currents alongshore and are the sand sources for the accretion of coastal dunes foredune accretion occurs where major sand banks have migrated shoreward over the last centuries to be finally driven ashore and weld under the impact of storm waves morphological changes in the bank field can impact on shoreline stability through dissipation or enhanced shoreward transmission of storm wave energy and effects on radiation stress particularly when waves are breaking over the banks where banks are close to the shore mitigation of offshore sediment transport especially during storms can occur because of gradients in radiation stress generated by the complex 3d bank structure these macro scale mechanisms involve embedded meso scale interactions that revolve around the mobility of sand waves mobility of beach bars and troughs and foredune mobility and micro scale processes of bedform mobility in the subaqueous and intertidal domains and of swash and aeolian beach dune sand transport these embedded interactions and the morphodynamic feedback loops illustrate the importance of synchroneity of sand transport from shoreface to dune on this coast large stretches of the foredunes show either signs of stability or mild but chronic erosion furthermore a demonstrated lack of a clear relationship occurs between storminess and coastal response over the second half of the 20th century the present situation may be indicative of conditions of rather limited sand supply from offshore notwithstanding the abundance of sand on the nearby shallow shoreface except in areas where a nearshore storm driven tidal sand bank has become shore attached apart from the important influence of shoreface sand banks and of wave bank interactions foredune accretion and erosion also depend on various context controls that include individual storm characteristics wind speed and incidence relative to the shore tidal stage during storms and direct human intervention on the shore through foredune and beach management the bewildering variability inherent in these intricately related parameters may also explain the poor relationship between storminess and barrier shoreline change and will still continue to render unpredictable the response of shores to individual storms

geomorphologic characteristics and evolution of managed dunes on the south west coast of france abstract the calibrated foredunes of the aquitaine coast sw france constitute an example of secular extensive application of nature based solution being one of the longest and largest dune systems in europe this iconic landscape offers considerable services to coastal societies since the mid half of the 18th century human work on sediment flows has resulted in the emergence of large sets of foredunes currently constituting an almost 230 km long managed barrier against inland sand invasion coastline erosion coastal flooding and also a major reserve of biodiversity last massive mechanic shaping of the foredunes following a so called ideal profile date back to the 1970s 80s and aimed to limit erosion dynamics and sediment mobility since they have been facing multiples disruptions over the years which have considerably modified their morphology especially during the last decades calibrated foredunes are currently exhibiting impressive dimensions with a mean dune height of about 16 6 m peaking at 30 m in some locations and a dune width mean along the coast of 187 m today 55 5 of them meet the ideal profile shape standards or surpass the in terms of dimensions whereas 21 5 of the calibrated foredunes are considered narrowed and need specific attention this regional analysis based on extensive airborne lidar datasets from 2011 to 2018 includes i a dune morphology classification based on several basic geomorphological indicators dune width height crest position back dune elevation compared to a calibrated idealised shaped profile ii a quantification of marine beach dune and aeolian sediments flows in m year and m m2 year and forms on dunes scarps blowouts depositional lobes as an indicator of the recent dynamics affecting dune morphology and iii a study of management control of calibrated foredunes 4613 interventions including actions taken after the outstanding winter of 2013 2014 as expected intensive dune management are mainly focused where assets are directly threatened the study highlights the importance and the efficiency of human management on dune evolutions long term dune form stability control of gullies and incipient frontal blowout after marine erosion protection of human issues however today management actions wind fence branch cover planting and reshaping are not conditioned by foredune morphology or last decade s beach dune dynamic sediment availability chronic coastline erosion considering long term erosion projections and expected impact of climate change the analysis shows the need of more global and extensive strategies in order to preserve the protection role of foredunes in the coming decades

morphologic properties derived from a simple cross shore sediment transport model this paper builds on the now classical discussions by bowen 1980 and bailard 1981 on the applicability and implications of bagnold s 1963 sediment transport model to nearshore profile modeling we focus on the morphologic implications of both the strengths and weaknesses of bagnold s model isolating the transport terms that are well predicted i e mean flow terms from those that are not well predicted i e transport due to correlations between flow and sediment load we factor bagnold s model into a dimensional transport magnitude and a nondimensional term the nondimensional term describes the relative importance of transport due to undertow gravity and correlations between flow and sediment load the transport magnitude largely determines the response time of nearshore profiles for typical nearshore environments this response time was estimated to vary as a function of incident rms wave height hrms from 500 years hrms 0 5 m to 2 years hrms 3 m the relative importance of competing transport mechanisms is shown to depend strongly on the relative wave height defined as the ratio of the rms wave height to the local depth simplified nearshore transport parameterizations that are a function of this variable were derived and were interrogated for the existence and form of equilibrium profiles several differences from previously computed equilibrium profiles were noted first because the relative wave height saturates in natural surf zones equilibrium profiles converge to a relatively flat profile near the shoreline second under some situations a seaward sloping equilibrium profile may not exist third the long response times combined with unknown stability of an equilibrium profile make it difficult to assess the physical connection between theoretical equilibrium profiles and profiles observed in nature

geomorphological contributions to palaeolimnology on the african continent abstract article history received 19 december 2007received in revised form 5 july 2008accepted 22 july 2008available online 3 august 2008keywords quaternarybeach ridgeshorelinelakemultiproxyosl lakes are highly informative repositories of information of the terrestrial response to regional and global climatedrivers in quaternary studies lake oor records are now frequently used to establish the magnitude timing andgeographicalextentofhumid aridtransitionsovertimescalesof10 2 10 4 years whiletheresolutionof thisrecordisunparalleled much of the geochemical and sedimentary da ta is challenging to interpret and highly basin speci c geomorphologicalproxies particularlyshorelines offeranadditionaloralternativerecordoflakehistory withrecenttechnological advances facilitating both access to and the utility of this proxy record recent advances in opticallystimulated luminescence osl dating allow the determination of the age of beach ridge emplacement in theabsence of organic material while the availabilityof shuttle radar topography mission srtm data in conjunctionwith digital elevation models dem aids in the identi cation of shoreline features and the topographicreconstruction of the former extent of palaeolakes here we highlight and illustrate the use of lacustrine shorelinefeatures for unravelling a quaternary climate signal wit hin africa from otherwise inaccessible and undatablepalaeolake records in the semi arid and arid subtropics an d identify their contribution towards high resolutionmultiproxy reconstructions of tropical low latitude quaternary environments and climates 2008 elsevier b v all rights reserved

application of multivariate statistical techniques in alongshore differentiation of coastal barriers abstract this paper investigates the existence of statistical correlations and relationships between geological and oceanographic parameters along a coastal barrier system in southern brazil the existence of few statistical studies on coastal barriers motivated the use of multivariate statistical techniques that take environmental parameters such as coastal morphological sedimentary features and their morphometric measurements into account the hierarchical cluster analysis hca and principal component analysis pca were used to assess the spatial variations of fourteen parameters driving the current and past behavior of this coastal barrier system at fourteen locations through the application of hca these locations were divided into four groups groups 1 2 3 and 4 the hca results were analyzed using pca the first pc1 and the second pc2 principal components together explained at least 76 4 of the variability of all four groups the most important geological and oceanographic parameters that were correlated to pc1 and pc2 were different in each group in general the shoreface slope and shoreface dimensions were common to all groups as pc1 correlated parameters being the most important ones regarding data variability in addition for the progradational groups 1 and 4 retrogradational group 2 and aggradational barriers group 3 pca indicated that shoreline orientation wave exposure and beach type are secondary but relevant factors controlling the past and current behavior of coastal barriers in southern brazil

conceptualising and mapping coupled estuary coast and inner shelf sediment systems whilst understanding and predicting the effects of coastal change are primarily modelling problems it is essential that we have appropriate conceptual frameworks for 1 the formalisation of existing knowledge 2 the formulation of relevant scientific questions and management issues 3 the implementation and deployment of predictive models and 4 meaningful engagement involvement of stakeholders important progress continues to be made on the modelling front but our conceptual frameworks have not evolved at a similar pace accordingly this paper presents a new approach that re engages with formal systems analysis and provides a mesoscale geomorphological context within which the coastal management challenges of the 21st century can be more effectively addressed coastal and estuarine system mapping cesm is founded on an ontology of landforms and human interventions that is partly inspired by the coastal tract concept and its temporal hierarchy of sediment sharing systems but places greater emphasis on a hierarchy of spatial scales this extends from coastal regions through landform complexes to landforms the morphological adjustment of which is constrained by diverse forms of human intervention crucially cesm integrates open coastal environments with estuaries and relevant portions of the inner shelf that have previously been treated separately in contrast to the nesting of littoral cells that has hitherto framed shoreline management planning cesm charts a complex web of interactions of which a sub set of mass transfer pathways defines the sediment budget and a multitude of human interventions constrains natural landform behaviour conducted within a geospatial framework cesm constitutes a form of knowledge formalisation in which disparate sources of information published research imagery mapping raw data etc are generalised into usable knowledge the resulting system maps provide a framework for the development and application of predictive models and a repository for the outputs they generate not least flux estimates for the major sediment system pathways they also permit comparative analyses of the relative abundance of landforms and the multi scale interactions between them finally they articulate scientific understanding of the structure and function of complex geomorphological systems in a way that is transparent and accessible to diverse stakeholder audiences as our models of mesoscale landform evolution increase in sophistication cesm provides a platform for a more participatory approach to their application to coastal and estuarine management

bar trough generation on a natural beach mechanisms for bar trough generation are examined using velocities measured in the field applied to the bowen 1980 bailard 1981 energetics based sediment transport model measurements consist of a cross shore array of nine electromagnetic current meters spanning the surf zone and daily bathymetric surveys during a 10 day period during which two storms occurred when the bathymetry evolved from a three dimensional terrace to a well developed linear bar the model predicts bed and suspended load transport separately based on various velocity moments the velocities are partitioned into mean currents low frequency infragravity and shear instabilities 0 05 hz to determine the relative importance of various mechanisms to the total transport velocity moments are computed over 90 min intervals to resolve tidal fluctuations tidal signatures were apparent in all modes of transport predicted transport rates are integrated and compared with daily cross shore bathymetric profiles averaged over a 400 m length of beach the suspended load terms were an order of magnitude greater than bed load terms owing to the low fall velocity of the fine grain sand within the surf zone model results for this experiment indicate the dominant mechanism for bar development was sediments mobilized by the strong longshore current and incident short waves within the surf zone and transported offshore by the mean undertow and shoreward transport onshore due to short wave velocity skewness using standard coefficients the model correctly predicted the first order movement of the bar during storms but underpredicted trough development and did not always perform well during mild wave conditions

assessing significant geomorphic changes and effectiveness of dynamic restoration in a coastal dune ecosystem article i nfo a shift from restoring coastal dunes as stabilized landscapes toward more morphodynamic ecosystems is un derway this paper uses results from a recent case study where invasive vegetation was removed from a coastal dune complex in western canada as a first step in a dynamic ecosystem restoration project spatial statistical methods used in the natural sciences to quantify patterns of significant spatial temporal changes are reviewed and the local moran s ii spatial autocorrelation statistic is explored for detecting and assessing significant changes cluster maps of positive depositional and negative erosional changes were used to derive statistically significant volumetric changes within discrete geomorphic units beach foredune trans gressive dune over one year following vegetation removal all units experienced net increases in sediment budgets compared to a pre restoration surface the beach experienced the highest episodic erosion and vol umetric change and greatest net annual sediment budget compared to the beach the annual sediment budget of the foredune was 19 whereas the transgressive dune was 33 the foredune recovered rapidly to initial erosion during restoration and subsequent natural events with consistently positive sediment volumes and attained a form similar to that pre restoration aeolian deflation and sand bypassing through the foredune was greatest in the two months following vegetation removal and peak accretion in the transgressive dune resulted from depositional lobes extending from the foredune smaller dunes migrating within the complex and growth of a precipitation ridge along the eastern margin several methodological and logistical considerations for detecting significant change in dynamic dune land scapes are discussed including sampling strategy design data normalization and control measures and incorpo rating uncertainty and inherent spatial relations within acquired datasets to ensure accuracy and comparability ofresults generally underutilizedincoastalgeomorphology spatialautocorrelation methods e g localmoran s ii are recommended over spatially uniform threshold approaches for the ability to detect local change processes and explore hypotheses on spatial temporal dynamics finally several key geomorphic indicators that are believed to aid in re establishing ecological conditions and processes that favor more resilient and natural dune ecosystems are identified for assessing the effective ness of dynamic restoration projects including increased aeolian activity enlarged active sand surface area positive sediment budgets increased dune morphodynamics improved geomorphic diversity and enhanced geomorphic resilience although limited in temporal scope the case study results show that the initial phase of the restoration treatment was effective in enhancing all indicators except for increasing sand surface area given decadal scale observations of climatic changes and longer term eco geomorphic trajectory toward stabi lization in the region however it is unlikely that the geomorphic effectiveness of this restoration effort will con tinue without continued frequent treatment interventions

undertow over a barred beach the spatial distribution of the mean cross shore flow undertow over a barred beach is examined with field data obtained on three energetic wave days during the duck94 experiment the vertical structure of the undertow is modeled using a turbulent eddy viscosity closure and includes the important effects of wave breaking described using the roller concept and convective acceleration of the current other than a more realistic description of observed turbulence variations a depth dependent eddy viscosity compared with a constant does not improve the agreement between predicted and observed undertow profiles the effect of using different boundary conditions is investigated by extending the formulations of stive and wind 1986 and svendsen et al 1987 to include random waves by ensemble averaging over the wave height distribution the contribution of breaking wave rollers to the surface mass flux can be of the same order or greater than the contribution associated with the organized wave motion the largest discrepancies between model predictions and observations occur over the sandbar where the mass transport of the breaking waves appears to be underestimated

development and setting of the alcudia bay beach dune system mallorca spain abstract the beach dune system of alcudia bay is located in the north of the island of mallorca the system includes both simple and compound parabolic dunes formed by n to nne winds and is made up of two dune areas with different dynamics 1 the northern area where despite the fact that the source of beach sediment is from the south dunes are formed by northerly winds and develop a narrow and linear barrier which separates a marsh from the bay and 2 the southern area where complex parabolic dunes formed by north northeasterly winds prograde south southwest landward extending several kilometers inland the broad pattern of the dunefield size is limited to the southeast by a mountain range and to the west by the effects of a topographic corridor oriented north south which channels the prevailing northerly wind causing a southward dune progression and limiting the westward extension of the dunefield

swash overtopping and sediment overwash on a truncated beach new experimental laboratory data are presented on swash overtopping and sediment overwash on a truncated beach approximating the conditions at the crest of a beach berm or inter tidal ridge runnel the experiments provide a measure of the uprush sediment transport rate in the swash zone that is unaffected by the difficulties inherent in deploying instrumentation or sediment trapping techniques at laboratory scale overtopping flow volumes are compared with an analytical solution for swash flows as well as a simple numerical model both of which are restricted to individual swash events the analytical solution underestimates the overtopping volume by an order of magnitude while the model provides good overall agreement with the data and the reason for this difference is discussed modelled flow velocities are input to simple sediment transport formulae appropriate to the swash zone in order to predict the overwash sediment transport rates calculations performed with traditional expressions for the wave friction factor tend to underestimate the measured transport additional sediment transport calculations using standard total load equations are used to derive an optimum constant wave friction factor of f w 0 024 this is in good agreement with a broad range of published field and laboratory data however the influence of long waves and irregular wave run up on the overtopping and overwash remains to be assessed the good agreement between modelled and measured sediment transport rates suggests that the model provides accurate predictions of the uprush sediment transport rates in the swash zone which has application in predicting the growth and height of beach berms c 2005 elsevier b v all rights reserved

storm impacts and shoreline recovery mechanisms and controls in the southern north sea abstract storm impacts play a significant role in shoreline dynamics on barrier coastlines furthermore inter storm recovery is a key parameter determining long term coastal resilience to climate change storminess variability and sea level rise over the last decade four extreme storms with strong energetic waves and high still water levels resulting from high spring tides and large skew surge residuals have impacted the shoreline of the southern north sea the 5th december 2013 storm with the highest run up levels recorded in the last 60 years resulted in large sections of the frontline of the north norfolk coast being translated inland by over 10 m storms in march and november 2007 also generated barrier scarping and shoreline retreat although not on the scale of 2013 between 2008 and 2013 a calm period recovery dominated barrier position and elevation but was spatially differentiated alongshore for one study area scolt head island no recovery was seen this section of the coast is being reset episodically landwards during storms by contrast the study area at holkham bay showed considerable recovery between 2008 and 2013 with barrier sections developing seaward through foredune recovery the third study area brancaster bay showed partial recovery in barrier location and elevation results suggest that recovery is promoted by high sediment supply and onshore intertidal bar migration at rates of 40 m a 1 these processes bring sand to elevations where substrate drying enables aeolian processes to entrain and transport sand from upper foreshores to foredunes we identify three potential sediment transport pathways that create a region of positive diffusivity at holkham bay during calm periods a general westward movement of sediment from the drift divide at sheringham sources the intertidal bar and foredune development at holkham bay however during and following storms the drift switches to eastward not only on the beach itself but also below the 7 m isobath sediment from the eroding barrier at brancaster bay and especially scolt head island also sources the sediment sink of holkham bay knowledge of foredune growth and barrier recovery in natural systems are vital aspects of future coastal management planning with accelerated sea level rise and storminess variability

morphodynamics of prograding beaches a synthesis of seasonal to century scale observations of the columbia river littoral cell abstract findings from nearly two decades of research focused on the columbia river littoral cell crlc a set of rapidly prograding coastal barriers and strand plains in the u s pacific northwest are synthesized to investigate the morphodynamics associated with prograding beaches due to a large sediment supply from the columbia river the crlc is the only extensive stretch of shoreline on the u s west coast to have advanced significantly seaward during the late holocene since the last cascadia subduction zone csz earthquake in 1700 with associated co seismic subsidence and tsunami much of the crlc has prograded hundreds of meters however the rates of progradation and the processes most responsible for sediment accumulation vary depending on time scale and the morphological unit in question remarkably the 20th and early 21st century shoreline change rates were more than double the late prehistoric rates that include recovery from the last major csz event most likely due to an increase in sediment supply resulting from inlet jetty construction in some locations detailed beach morphology monitoring reveals that at interannual to decadal scale the upper shoreface aggraded about 2 cm yr subtidal sandbars migrated offshore and decayed while intertidal bars migrated onshore and welded to the shoreline the shoreline prograded about 4 m yr and 1 to 2 new foredune ridges were generated a detailed meso scale sediment budget analysis in one location within the littoral cell shows that approximately 100 m3 m yr accumulated between 12 m seaward limit of data and 9 m crest of landward most foredune gradients in alongshore sediment transport net onshore directed cross shore sediment transport within the surf zone and cross shore feeding from a shoreface out of equilibrium with forcing conditions are each partially responsible for the significant rates of sediment supplied to the beaches and dunes of the crlc during the observational period direct observations of beach progradation at seasonal to decadal scale are put in context of measured or inferred changes over time scales of decades to centuries

the systematic contribution of transporting mechanisms to the cross shore sediment transport in water depths of 3 to 9 m the systematic contributions of short waves infragravity waves and mean flows to the cross shore sediment transport were studied with direct measurements of instantaneous near bed sediment concentrations and velocities as well as with an energetics based sediment transport model using measured time series of near bed cross shore flow as input the study was conducted at four cross shore positions in the multiple bar system of terschelling netherlands during three field campaigns each with a five week duration the data were collected in 3 to 9 m water depth during a wide range of conditions from low energy non breaking conditions to almost fully saturated breakers the height over depth ratio hs h was applied at all four measuring stations as a local conditional parameter all model predictions were grouped into hs h classes with a width of 0 02 to highlight the generality of the data the energetics approach predicted that the suspended load dominated over the bedload at all four stations both the sediment flux measurements as well as the model predictions showed that the largest contributors to the gross suspended sediment transport were made by the short waves and the undertow inducing an onshore and offshore transport respectively their contributions to the gross suspended transport were about 40 to 50 under surf zone conditions bound infragravity waves were observed and predicted to result in an offshore directed transport that was of subordinate magnitude compared to the observed and estimated magnitudes by the short waves and the undertow however as these transports almost cancelled out because of their about equal magnitude but opposite sign the suspended transport by bound infragravity waves may not be ignored and may rather paradoxically have a relatively large influence on the net suspended sediment transport hydrodynamical processes that do not seem to be of importance to the onshore and offshore sediment transport in 3 to 9 m water depth in the long run are mean flows under non breaking conditions and free infragravity motions a direct comparison between measured sediment fluxes and the model predictions suggests that simple energetics models are suitable for predicting cross shore sediment transport in 3 to 9 m water depth

shoreface morphodynamics of a high energy steep and geologically constrained shoreline segment in northern ireland abstract the shoreface a complex and poorly understood part of the coastal zone plays a critical role in sediment transport processes between the beach and the inner shelf this two year study examined the surface and subsurface architecture and the process response mechanisms of a high energy steep and geologically constrained shoreface segment 1 20 m depth in northern ireland fourteen sequential bathymetric surveys covering an area of 2 km2 were compared and analysed in order to investigate seabed changes and their relationship to wave and wind forcing results reveal that the shoreface is highly dynamic and complex an examination of high energy conditions and lower than average energy conditions revealed significant periods of both accretion and erosion these complex morphodynamic responses are attributed mainly to a combination of antecedent pre survey morphology differences in wind forcing and coastal surges a comparison of seabed changes over 2 yr reveals net shoreface accretion which is attributed to inner shelf to shoreface sediment transport over the same period the adjacent west strand beach showed moderate erosion the study provides information on the morphodynamics of a steep high energy embayment shoreface a coastal environment which has received little previous attention

sediment supply from shoreface to dunes linking sediment transport measurements and long term morphological evolution a significant problem in current coastal research is the understanding of linkages between morphological phenomena occurring on different temporal and spatial scales morphodynamic processes in the nearshore typically exhibit nonlinear behaviour and consequently phenomena which occur on short temporal event scales as e g observed during field experiments have generally been difficult to upscale to provide an understanding of the long term behaviour of the coast on the time scale of seasons or decades this paper documents a persistent onshore migration of nearshore bar features over a period of 3 decades using a set of cross shore profile surveys from a barrier on the danish north sea coast the observed behaviour is consistent with experimental data obtained during weeklong field campaigns when sediment transport and bar migration were found to be landward directed during high energy dissipative conditions hydrodynamic and sediment transport processes leading to onshore bar migration and eventually welding of the bars are documented to provide an explanation for the observed long term evolutionary trends in addition bar welding and the resulting intertidal bar formation represent an onshore sediment storage which is subsequently available for aeolian transport observations on aeolian sediment transport indicate that transport rates and sediment supply to the foredunes critically depend on the presence of dry sand sources as represented by well drained intertidal bars measurements of long term accretion rates in foredunes indicate that volumes deposited on the crest and lee slope of the dunes are in reasonable correspondence with volumes supplied to the subaerial beach through the process of bar welding hence the data suggest that a persistent onshore directed sediment supply occurs from the shoreface across the surf and intertidal zones and into the dunes of the investigated barrier

vertical structure of mean cross shore currents across a barred surf zone mean cross shore currents observed across a barred surf zone are compared to model predictions the model is based on a simplified momentum balance with a turbulent boundary layer at the bed turbulent exchange is parameterized by an eddy viscosity formulation with the eddy viscosity a independent of time and the vertical coordinate mean currents result from gradients due to wave breaking and shoaling and the presence of a mean setup of the free surface descriptions of the wave field are provided by the wave transformation model of thornton and guza 1983 the wave transformation model adequately reproduces the observed wave heights across the surf zone the mean current model successfully reproduces the observed cross shore flows both observations and predictions show predominantly offshore flow with onshore flow restricted to a relatively thin surface layer successful application of the mean flow model requires an eddy viscosity which varies horizontally across the surf zone attempts are made to parameterize this variation with some success the data does not discriminate between alternative parameterizations proposed the overall variability in eddy viscosity suggested by the model fitting should be resolvable by field measurements of the turbulent stresses consistent shortcomings of the parameterizations and the overall modeling effort suggest avenues for further development and data collection

barrier islands on bedrock a new landform type demonstrating the role of antecedent topography on barrier form and evolution barrier islands commonly occur in coastal plain and deltaic settings and a variety of behavioral and stratigraphic models exist in this paper a 90 km long barrier island system in the outer hebrides of scotland is identified for the first time uniquely among barrier islands the system rests directly on a planar bedrock gneiss surface a strandflat this bedrock surface has a profound influence on the morphology of the barrier island chain and exerts the dominant influence on barrier island form and evolution during transgression topographical irregularities on the bedrock surface control both plan and profile morphology of the barrier islands under sea level rise by barrier migration sediment is redistributed onshore and alongshore in a strongly three dimensional manner determined by topographic variability in the bedrock the barrier islands represent an endpoint in transgressive barrier island geomorphology that is controlled by the bedrock surface they are at the upper end of the recognized tidal amplitude for barrier islands the offshore wave regime is very high energy they lack a shoreface and neither ravinement surface nor transgressive sand sheet are developed sediment supply is dominated by offshore derived skeletal carbonate

tracing sea level changes during the mid holocene in the southern mediterranean coast an example from the gulf of gabes abstract mid holocene sea level emergence was recorded along a mid latitude coastal site in the gulf of gabes tunisia in beach rock deposits however the post emergence sea level curve and associated hydro sedimentary processes have rarely been documented this study presents new records of sea level changes along the tunisian coast since the mid holocene each phase of the sea level curve was evidenced and supported by lithostratigraphic morphological and archaeologic markers post emergence sea level fall due to postglacial isostatic rebound was recognized in regressive sequences which vary depending on available accommodation space from a small pocket beach to a well developed dune system sea level stabilization following isostatic rebound has promoted the end phase deposits of the regressive sequences however this stability was interrupted during the late holocene by a high energy storm event that accumulated a transgressive boulder unit at 2 m above present shape and disposition of the boulder ridge behind a prograding modern shoreline suggests that sea level has not changed during the late holocene the existence of a roman fish pond on the upper foreshore confirms stability of sea level during the last two millennia the combination of lithostratigraphic morphological and archaeologic markers represents a tool for improving the accuracy of dating of erosional and depositional periods in mid coastal sections

barrier formation on an actively prograding delta system the red river delta vietnam abstract an extensive barrier spit system 20 to 30 km long developed on the delta front platform of the ba lat delta within a relatively short period 10 20 years however it was not evident whether the formation was related to river floods typhoons or calm weather conditions or to cross shore or alongshore sediment transport mechanisms therefore a process based numerical model that simulates sediment transport and morphologic changes by waves tides wind and river flow is used to analyze the processes that govern this barrier formation the mechanism that initiates the barrier formation is concluded to be onshore transport by wave asymmetry of sediment previously transported seaward in the buoyant river plume the main mechanism that counteracts the barrier formation is probably destruction of the barrier by river flow during the subsequent transformation from a subaqueous barrier into a sub aerial barrier spit system overwashes and alongshore sediment transport become increasingly important this spit system therefore appears to be dominated by alongshore processes even though its initial formation is more strongly regulated by cross shore processes the importance of cross shore processes results in a minor contribution of typhoons to the initial formation of these barriers typhoons are not very important to destruction of barriers as well because wave energy is gradually dissipated over the gentle offshore profile which in turn results from river plume sedimentation

a warming tropical central pacific dries the lower stratosphere the amount of water vapor in the tropical lower stratosphere tls which has an important influence on the radiative energy budget of the climate system is modulated by the temperature variability of the tropical tropopause layer ttl the ttl temperature variability is caused by a complex combination of the stratospheric quasi biennial oscillation qbo tropospheric convective processes in the tropics and the brewer dobson circulation bdc driven by mid latitude and subtropical atmospheric waves in 2000 the tls water vapor amount exhibited a stepwise transition to a dry phase apparently caused by a change in the bdc in this study we present observational and modeling evidence that the epochal change of water vapor between the periods of 1992 2000 and 2001 2005 was also partly caused by a concurrent sea surface temperature sst warming in the tropical central pacific this sst warming cools the ttl above by enhancing the equatorial wave induced upward motion near the tropopause which consequently reduces the amount of water vapor entering the stratosphere the qbo affects the tls water vapor primarily on inter annual timescales whereas a classical el nino southern oscillation enso event has small effect on tropical mean tls water vapor because its responses are longitudinally out of phase this study suggests that the tropical central pacific sst is another driver of tls water vapor variability on inter decadal timescales and the tropical sst changes could contribute to about 30 of the step wise drop of the lower stratospheric water vapor from 1992 2000 to 2001 2005

sediment transport under wave and current combined flows on a tide dominated shoreface northern coast of france abstract hydrodynamic circulation and sediment transport patterns were investigated on a macrotidal shoreface off the southern north sea coast of france from in situ directional wave and current measurements and through numerical modeling of sediment flux current meters equipped with wave gauges were deployed at two sites on the mid upper shoreface in approximately 5 6 m water depth during 6 and 15 days sediment flux was estimated using the sedtrans96 numerical model li m z amos c l 2001 sedtrans96 the upgraded and better calibrated sediment transport model for continental shelves comp geosc 27 619 645 based on grant and madsen s grant w d madsen o s 1986 the continental shelf bottom boundary layer ann rev fluid mech 18 265 305 combined flow boundary layer theory the hydrodynamic measurements and modeling results show that sediment on the shoreface is essentially transported alongshore in response to shore parallel tidal currents the direction of the net sediment transport is largely determined by the asymmetry of the tidal flows which can be flood or ebb dominated but during important wind speed events winds blowing in the same direction as tidal flow can significantly reinforce tidal currents or conversely can limit tidal current speeds when acting in the opposite direction although sediment transport on this macrotidal shoreface is strongly controlled by tidal processes waves can significantly enhance bed shear stresses resulting in increased sediment remobilization and hence higher sediment flux wave induced onshore sediment transport may occasionally occur but is several orders of magnitude lower than longshore transport this macrotidal shoreface is thus characterized by a hydraulic regime strongly dominated by shore parallel tidal flows that favour longshore sediment dispersal rather than shore normal transport our results imply that the water depths from which sediment may be transported shoreward to beaches is certainly much more restricted on a macrotidal shoreface such as the one bordering the northern coast of france than on micro and mesotidal shoreface environments where weaker tidal currents do not significantly limit cross shore sediment movements

transgressive and regressive stratigraphies of coastal sand barriers in southeast australia abstract in recent years attempts have been made in southeast australia to document the stratigraphic characteristics of coastal sand barriers two basic arrangements of facies are distinguished those associated with transgressive depositional sequences and those associated with regressive sequences transgressive sequences either are formed during the postglacial marine transgression or are related to receding or transgressive barriers at present sea level in the former case complex interfingering of nearshore washover and lagoonal facies are evident in many areas these facies underlie those associated with regressive sequences which have formed since sea level has reached its present position ca 6000 6500 yrs ago examples of regressive sequences associated with both prograded and stationary barrier types occur in southeast australia here the thickness of nearshore facies in particular is commonly greater than equivalent units beneath barriers on coasts of lower energy and for less steep inner shelf gradients in the northern hemisphere the interplay of various factors within embayments has led to the development of several barrier types such as prograded stationary receded and episodic dune with some sedimentary characteristics in common with similar types recognized in other parts of the world e g texas delaware the netherlands barriers formed as a result of migrating spits and tidal inlets are not common in southeast australia

wave transformation across the inner surf zone sea and swell wave heights observed on transects crossing the mid and inner surf zone on three beaches a steep concave up beach a gently sloped approximately planar beach and a beach with an approximately flat terrace adjacent to a steep foreshore were depth limited i e approximately independent of the offshore wave height consistent with previous observations the wave evolution is well predicted by a numerical model based on the one dimensional nonlinear shallow water equations with bore dissipation the model is initialized with the time series of sea surface elevation and cross shore current observed at the most offshore sensors located about 50 to 120 m from the mean shoreline in mean water depths 0 80 to 2 10 m the model accurately predicts the cross shore variation of energy at both infragravity nominally 0 004 f 0 05 hz and sea swell here 0 05 f 0 18 hz frequencies in models of surf zone hydrodynamics wave energy dissipation is frequently parameterized in terms of s the ratio of the sea swell significant wave height to the local mean water depth the observed and predicted values of s increase with increasing beach slope and decreasing normalized by a characteristic wavenumber k water depth kh and are well correlated with kh a measure of the fractional change in water depth over a wavelength errors in the predicted individual values of s are typically less than 20 it has been suggested that infragravity motions affect waves in the sea swell band and hence s but this speculation is difficult to test with field observations numerical simulations suggest that for the range of conditions considered here s is insensitive to infragravity energy levels

the behaviour of a multiple bar system in the nearshore zone of terschelling the netherlands 1965 1993 abstract the behaviour of a multiple bar system in the nearshore zone of the island of terschelling the netherlands is investigated on the time scale of years using a data set of soundings the data set covers the period from 1965 to 1993 the behaviour is analysed in terms of bar crest position and in terms of morphometric parameters such as bar crest depth height width and volume two or three breaker bars are permanently present in the study area each individual bar passes through three stages during its existence 1 generation close to the shore 2 seaward migration and 3 degeneration at the outer margin of the nearshore bar zone the key factor controlling the behaviour of the inner bars is the crest depth of the outer bar three different couplings between the behaviour of the individual bars have been observed 1 bar stage changes due to the degeneration of the outer bar 2 prevention of the transition of an inner bar from the first to the second stage caused by the appearance from alongshore of a new outer bar having a small crest depth and 3 difference in mean annual seaward migration rate caused by the possible presence of a more seaward positioned bar it is hypothesized that the crest depth of the outer bar governs the relative importance of processes inducing shoreward and seaward migration in the inner nearshore bar zone and therefore controls the behaviour of the nearshore bar zone on the time scale of years

environmental controls on coastal dune formation skallingen spit denmark abstract many coastal dune systems in western europe were emplaced during the little ice age lia the formation of such dune fields has generally been ascribed to a combination of low sea level and strong winds during that time period providing a supply of sand from the exposed shoreface and sufficient wind energy to transport this sand landward however little information exists on the processes that controlled sediment supply to the beach and why this onshore supply was initiated at all in this contribution we consider the origin and development of older dune fields on a barrier spit complex skallingen located in the northern part of the danish wadden sea maps and new data on dune litho and chrono stratigraphy the latter based on osl dating allow a precise estimate of the initiation and termination of dune emplacement dune formation at skallingen started at a relatively late stage of the lia and it can be temporally correlated with a phase of relative sea level rise in north western europe and with a high frequency of storm surges along the danish west coast these are the conditions during which nearshore bars currently migrate onshore across the shoreface off skallingen the bars eventually merge with the beach and constitute a source of sand for modern foredune accretion it is probable that the onshore bar migration occurred under similar conditions in the past and the migration was triggered or enhanced by the sea level recovery from the mid lia low stand and the associated frequent storm surge activity consequently at skallingen onshore sand supply was caused by marine rather than aeolian agents this supply provided the basis for subsequent dune formation indications are however that the sediment supply to the beach dunes was a factor of 2 3 larger in the past dune aggradation eventually ceased around 1900ad because of dyke construction hence the association between dune formation and sea level surge variation at skallingen is somewhat contrary to other statements of coastal dune development during the lia in north western europe

extracting decadal morphological behaviour from high resolution long term bathymetric surveys along the holland coast using eigenfunction analysis abstract the understanding and prediction of coastal behaviour over a time span of decades and alongshore stretches of tens of kilometres is important in coastal management the controlling variables for coastal behaviour on these scales are yet unknown it is hypothesised that regions exhibiting different large scale coastal behaviour lscb regions are controlled by different hydrodynamic forcings or by different sedimentological or morphological constraints or by some combination of these factors the objective of this study is to elaborate a method that effectively quantifies large scale morphological changes from a large bathymetric data set large temporal and spatial extent combined with a high resolution such to define lscb regions the method of analysis consists of a combination of the empirical eigenfunction technique and a moving window approach the method has been applied on a data set of over 14 000 nearshore profiles the data set consists of yearly soundings of the nearshore profile along a coastal stretch of 115 km length the holland coast the alongshore profile spacing is generally 250 m all profiles surveyed in the period 1963 1990 are included in the analysis application of the method on the dutch data set reveals that lscb regions indeed can be identified the sizes of the lscb regions are 5 km 15 km 20 km 32 km and 42 km differences in behaviour of the secondary morphology i e morphology other than the mean profile shape e g nearshore bars are most pronounced the change in behaviour between lscb regions generally occurs over distances as short as about 2 km the boundaries between the regions are therefore surprisingly sharp in general no clear long term trends in the development of the shape of the sub aqueous profile have been observed along the holland coast along certain stretches trends in cross shore shifting of the sub aqueous profile occurred the average shape of the sub aqueous profile seems to have no relation with the trend in cross shore shifting of the shoreline the 1 m contour the sub decadal shoreline fluctuations however are possibly related to the largescale dynamics of multiple bar systems

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

the effect of wind gusts moisture content and fetch length on sand transport on a beach this paper reports on an analysis of instantaneous sediment transport in relation to wind gusts moisture content and fetch length from a field study carried out at skallingen denmark wind speeds were measured with cup anemometers and instantaneous sediment transport with vertical traps coupled to electronic balances moisture content was measured gravimetrically using samples taken along a beach profile at intervals of 1 to 2 h sediment transport and wind speeds were sampled at 1 hz and a 5 s running mean was used to smooth the data from the trap because of limitations of the balance resolution three measures of the threshold of sediment motion the intermittency threshold minimum threshold and maximum threshold were explored using data from five runs carried out on october 26 2000 the intermittency threshold and maximum threshold were largely insensitive to wind speed but varied spatially along the fetch distance the minimum threshold increased significantly with increasing mean wind speed as a result of reduced time for drying of the surface layer examination of time series for instantaneous wind speed and sediment transport for a number of runs on october 26 and november 6 2000 showed close agreement between fluctuations in wind speed and fluctuations in sediment transport cross spectral analysis of instantaneous wind speed and sediment transport for one run on each day where there was continuous transport showed high coherence between the two variables over a range of frequencies from 0 2 hz to 0 01 hz plots of all non zero instantaneous sediment transport values versus wind speed show considerable scatter in general transport rates are highest for traps located further from the upwind non erodible boundary i e along the fetch best fit power relationships show r2 values generally ranging from 0 4 to 0 6 and exponents ranging from 4 5 to 6 94 i e much higher than the traditional value of 3 found in most transport equations traps located close to the upwind boundary had lower r2 values and exponents 2 5

origins of holocene coastal strandplains in southeast australia shoreface sand supply driven by disequilibrium morphology abstract coastal barriers store depositional records of past environmental conditions such as sea level wave climate and sedimentary regime the embayed highstand coast of southeast australia features a diverse range of coastal sand barriers suggesting varying depositional responses to holocene environmental conditions in particular the varying chronologies of prograded barrier strandplains along a passive margin with a predominantly autochthonous sedimentary regime raises questions about relative sea level change and sediment sharing within and between compartments during the holocene here we apply detailed geological data and geochronology from the holocene prograded barrier system at tuncurry within a morphodynamic modelling approach to investigate the depositional response of the coastal system to possible drivers of strandplain growth including 1 forced regression driven by mid to late holocene relative sea level fall 2 time varying external sand supply via the alongshore transport system and 3 shoreface sand supply in response to disequilibrium morphology and stable sea level comparison between the simulated depositional response of the coastal system and the geological records suggests that progressively weakening and depth decaying shoreface sand supply in response to disequilibrium morphology was the primary driver of holocene strandplain growth alongshore sand transport into the tuncurry compartment via a headland attached shelf sand body may have provided a secondary sand source although the simulated barrier shoreface evolution precludes a dominant external sand supply mid to late holocene sea level fall from a highstand level within the range of uncertainty in available indicators 1 5 m above present could only have contributed a minor portion of strandplain growth by process of forced regression the simulations demonstrate the potential sensitivity of strandplain chronologies to the sampling location i e shoreface or dune facies which emerges from coupled barrier shoreface evolution that may support time decaying volumetric growth and steady shoreline progradation simultaneously shoreface sand supply driven by the ongoing relaxation of disequilibrium morphology may persist at subtle rates 1 2 m3 m yr today on some southeast australian beaches promoting shoreline stability and potentially moderating initial shoreline response to sea level rise

aeolian transport rates across raked and unraked beaches on a developed coast wind characteristics and aeolian transport were measured on a naturally evolving beach and dune and a nearby site where the beach is raked and sand trapping fences are deployed the beaches were composed of moderately well sorted to very well sorted fine to medium sand the backshore at the raked site was wider and the foredune was more densely vegetated and about 1 m higher than at the unraked site wind speeds were monitored using anemometers placed at 1 m elevation and sand transport was monitored using vertical traps during oblique onshore alongshore and offshore winds occurring in march and april 2009 inundation of the low backshore through isolated swash channels prevented formation of a continuously decreasing cross shore moisture gradient the surface of the berm crest was dryer than the backshore making the berm crest the greatest source of offshore losses during offshore winds the lack of storm wrack on the raked beach reduced the potential for sediment accumulation seaward of the dune crest during onshore winds and the higher dune crest reduced wind speeds and sediment transport from the dune to the backshore during offshore winds accretion at wrack seaward of the dune toe on the unraked beach resulted in a wider dune field and higher narrower backshore although fresh wrack is an effective local trap for aeolian transport wrack that becomes buried appears to have little effect as a barrier and can supply dry sand for subsequent transport aeolian transport rates were greater on the narrower but dryer backshore of the unraked site vegetation growth may be necessary to trap sand within zones of buried wrack in order to allow new incipient foredunes to evolve copyright 2010 john wiley sons ltd

a near inertial internal wave spectrum for the sargasso sea in late summer abstract independent estimates of the frequency wavenumber spectrum of near inertial waves for the sargasso sea in late summer were made using 8 time series of horizontal velocity from a single moored vertical array and 58 vertical profiles of horizontal velocity from a horizontal array of expendable velocity profilers the profiler data were analyzed to produce an internal wave frequency wavenumber spectrum with sufficient resolution to resolve the details of the inertial peak and compute the vertical energy flux comparison with the lower resolution spectrum from the moored array shows qualitative agreement the differences are most likely due to biases in both techniques and to intermittency of the internal wave field these data reveal a marked asymmetry of the near inertial internal wave field with a net downward enemy flux of 0 12 0 12 ergs cm 2 s 1 the downward propagating waves have more energy a larger horizontal scale and a lower frequency than the upward propagating waves the magnitude of t

depositional controls on a hypertidal barrier spit system architecture and evolution pointe du banc spit north western france physical stratigraphy architecture and evolution of barrier systems in hypertidal environments tidal range above 6 m are understudied and depositional controls are poorly understood compared with wave dominated barrier systems and barrier spits in microtidal mesotidal and macrotidal settings based on vibracores ground penetrating radar radiocarbon and optically stimulated luminescence age data the formation and evolution of the hypertidal barrier system of pointe du banc north western france has been reconstructed the study shows that the barrier spit has a complex composite sedimentary architecture consisting of wave dominated and tide dominated sedimentary bodies a morpho sedimentary model is presented that demonstrates how barrier spit progradation resulting from littoral drift was the main manner of spit elongation whereas sediment convergence caused by landward migration of swash bars and seaward migration of tidal dunes caused the spit terminus to grow in height and width these results suggest that long term accretion rates varied considerably in response to changes in sediment supply variations in storminess together with the large scale topography of the coast controlled the sediment supply and thus the evolution of the barrier system during latest holocene despite architectural complexity hypertidal barrier systems preserve records of past climate changes

impact of atmospheric circulation patterns on coastal dune dynamics nw spain article i nfo dunes in temperate latitudes have experienced a significant stabilization in recent times essentially as a conse quence of the expansion of dense vegetation cover yet the causes for this gradual stabilization as well as the causes promoting antecedent aeolian mobilization remainpoorlyunderstood the traba coastal dune field located in nw spain was examined to explore the causes inducing aeolian activity and subsequent stabilization since 1940 morphological changes were identified through the combination of aerial photographs and geophysical techniques local wind field regimes were simulated using a regional climate model to obtain the variability of the most relevant modes of atmospheric circulation in the north atlantic and european regions north atlantic oscillation nao eastern atlantic ea and scandinavian scand this allows us to identify the impact of these circulation modes over dune dynamics results document an episode of aeolian activity during the 1950s followed by a gradual stabilization and fixation of the dune coincident with a decrease on storm and wind inten sity yet aeolian sand movement remained active insmall areas blowouts occurring mainly during the summer ne winds associated with a negative phase of the ea explain the movement of sand within the dune field under favorable conditions of sand supply on the other hand sand supply to the dune field from the beach was promoted by nw winds coincident with the summer negative phase of nao during winter the negative nao favored frequent sw winds associated with the passage of intense storms which in turn explain sand remobilization from the beach making sediment available for the nw winds to blow inland with this work it is proven that to understand past and future aeolian activity requires critical consideration of the variability and impact of the two principal modes of atmospheric circulation in the north atlantic nao and ea the scand mode explaining alowerpercentageofthelocalwind fieldvariabilitywasalsoincludedtoachievehigher significance levels of explained variance

contrasting geomorphological storm response from two adjacent shorefaces shorefaces play a critical role in cross shore sediment transport between the beach and inner shelf particularly during storm conditions a comparison and examination of storm driven sedimentary changes on two adjacent shorefaces in northern ireland located only 5 km apart revealed significantly different geomorphological responses the steeper shoreface at west strand responded with extensive sediment deposition across almost the entire shoreface in contrast with the more dissipative and quasi linear shoreface at portstewart which mostly showed nearshore bar changes results from the two sites which have similar wave wind characteristics and seabed sediments suggest that i cross shore morphology ii immediately previous antecedent shoreface morphodynamic behaviour and iii the presence or lack of offshore sand appear to be the primary controls on storm driven sedimentary changes attributed to the high energy event copyright 2015 john wiley sons ltd

the geomorphology and evolution of a large barrier spit farewell spit new zealand farewell spit is a 25 km long barrier spit that marks the end of a littoral drift system almost 1000 km in length that runs along south island new zealand the spit is composed of barchan dunes over 20 m high sand sheets over 1 km wide and vegetated linear dunes analysis of aerial photography indicates a rapid colonization of the spit by vegetation which has expanded in area by 75 since 1950 vegetation colonization preferentially occurs on the southern side of the spit with its northern margin characterized by barchan dunes which migrate at rates of up to 64 m yr sand sourced from longshore drift appears to be the primary source of beach sediment which is then transported into the dune field by the persistent westerly winds of the roaring 40s while there has been significant dune roll over on the surface of the spit its overall area has remained much the same for the past 54 years occasional cyclone events cause erosion but this is balanced by aeolian sediment transport it would appear that extension of the subaerial portion of the spit is related to the development of shells banks at its downdrift end which are periodically welded to the main spit by dune extension farewell spit therefore provides an ideal example of a barrier environment where longshore sediment supply and aeolian transport dominates geomorphic evolution this differentiates the study site from other barrier environments where overwash or tidal inlet development often characterizes recent landform evolution copyright 2010 john wiley sons ltd

shoreface sand supply and mid to late holocene aeolian dune formation on the storm dominated macrotidal coast of the southern north sea abstract although pulses of coastal dune development in the course of the holocene have been attributed to variations in the availability of sand to modulation of sand supply by sea level change and to changes in wind conditions identifying the processes driving such pulses has been rather elusive the shore deposits bordering the tide and storm wave dominated southern north sea evince complex mid to late holocene stratigraphy and sediment heterogeneity these deposits include a unique 7 km long 0 3 0 6 km wide and up to 7 m high aeolian sand unit the ghyvelde dune occurring astride the french belgian border in an apparently anomalous inland location the dune overlies and is surrounded by tidal sandy and muddy deposits incorporating freshwater peat data from four mechanical cores and eight auger holes and three radiocarbon ages and one osl age suggest that this inland dune was part of an ancestral north sea sand flat and mudflat environment confronting the dune stratigraphy with the prevailing tide and storm controlled dynamics of shoreline progradation in this area indicates that dune formation occurred under a pulse of abundant sand supply resulting from the attachment to a mid holocene north sea tidal flat shore of a shoreface tidal bank under repeated storms this mode of onshore sand supply generates extremely rapid progradation up to 1 km over a century of the sand flat shore the surface of which serves as a large aeolian fetch zone for active backshore dune accumulation while parts of this surface trap locally significant amounts of mud that are subsequently fossilised by aeolian sand the potential influence of sea level and storminess in modulating the timing of shoreface sand supply and late holocene coastal dune development in the southern north sea reported in studies from other areas remains to be established

beach dune interactions on the dry temperate danube delta coast abstract beach dune seasonal elevation changes aeolian sand transport measurements bathymetric surveys and shoreline evolution assessments were used to investigate annual and seasonal patterns of dune development on sf ntu gheorghe beach the danube delta coast from 1997 to 2004 dune volume increased consistently 1 96 m 3 m 1 y 1 to 5 1 m 3 m 1 y 1 over this 7 year period with higher rates in the southward downdrift direction dune aggradation is periodically limited by storms each of which marks a new evolutionary phase of the beach dune system as a consequence of the variable beach morphology and vegetation density during a year foredune growth occurs during the april december interval while between december and april a slightly erosive tendency is present the pattern of erosion and deposition shown by the topographical surveys is in good agreement with the sand transport measurements and demonstrates the presence of a vigorous sand flux over the foredunes which is 20 50 smaller than on the beach this high sand flux due to low precipitation and sparse vegetation cover creates an aerodynamically efficient morphology on the seaward dune slope the seaward dune face accretes during low to medium onshore winds 5 5 12 m s 1 and erodes during high winds 12 m s 1

aeolian sediment supply at a mega nourishment abstract mega nourishments are intended to enhance growth and resilience of coastal dunes on medium to long time scales by stimulation of natural sediment transport processes the growth and resilience of coastal dunes largely depends on the presence of a continuous supply of aeolian sediment a recent example of a mega nourishment is the 21 mm 3 mega nourishment known as the sand motor the sand motor is intended to nourish the entire holland coast over a period of two decades four years of bi monthly topographic measurements of the sand motor domain provide an opportunity to analyze spatiotemporal variations in aeolian sediment supply using an aeolian sediment budget analysis it appears that more than 58 of all aeolian sediment deposits originate from the low lying beaches that are regularly reworked by waves aeolian sediment supply from higher beaches diminished after half a year after construction of the sand motor likely due to the formation of deflation lag deposits that constitute a beach armor layer the compartmentalization of the sand motor in armored and unarmored surfaces suggests that the construction height is an important design criterion that influences the lifetime and region of influence for any mega nourishment

cross shore suspended sediment transport in the surf zone a field based parameterization existing cross shore sediment transport models for two dimensional surf zone bathymetries almost invariably predict offshore directed sand transports and bar migrations during storm conditions however onshore directed suspended sediment fluxes and associated nearshore bar migration were observed during recent field experiments on a gently sloping beach on the danish north sea coast field measurements of suspended sediment flux obtained during three experiments on two different beaches are used to parameterize the observed fluxes this parameterization predicts suspended sediment transport due to incident waves and undertow across bars in two dimensional surf zones first a non dimensional sediment flux index is formulated which describes the tendency towards net onshore or offshore transport and the strength of that tendency the non dimensional formulation circumvents the problem of measurement inconsistencies due to varying elevations of sediment concentration sensors relative to the bed the index is found to depend upon the undertow velocity the incident wave skewness and the cross correlation between orbital velocity and sediment concentration however some of these parameters are difficult to predict particularly in barred surf zones and therefore the independent variables are recast in terms of a set of more easily obtainable parameters the sediment flux index depends on a combination of the following non dimensional bed shear stress the shields parameter relative water depth wave orbital velocity relative wave height and bed slope finally a formulation of suspended sediment transport across bars is obtained by linking the flux index with a parameterization of the sediment concentration distribution in the water column these concentrations are found to depend on non dimensional bed shear stress relative wave height and water depth the formulation predicts a tendency for onshore directed sediment transport due to incident waves on gently sloping beaches and or with large bed shear stresses on steeply sloping beaches and or in the inner part of the surf zone there is a tendency towards offshore sediment transports due to the undertow

sandbar dynamics in microtidal environments migration patterns in unprotected and bounded beaches abstract novel observations of bar features and migration patterns at three italian sandy beaches in senigallia central adriatic sea and terracina central tyrrhenian sea are presented while two of these beaches are unprotected one is artificially embayed through the presence of a concrete jetty bar locations and motions are analysed with video imagery data sets from coastal monitoring stations wave climate from the copernicus oceanographic model is used to correlate hydrodynamics and beach morphology clear net offshore migration nom patterns are identified at all beaches although exhibiting different response scales at the low slope beach of senigallia mean surf zone slope of 0 009 bars are more sensitive to seasonal changes in wave climate with offshore shifts in winter and inactivity in summer mean annual migration rates of up to 0 26 m day and 0 09 m day are observed for outer and inner bars respectively no significant response to single storms is observed except during a single nne storm no distinct erosive or accretive trend for the shoreline is evidenced at the steep beach of terracina mean surf zone slope of 0 018 conversely bars are strongly responsive to single storm events with displacements of up to 25 50 m across a single storm the mean inter annual migration rate is 0 08 m day for the single outer bar whereas a slight onshore trend 0 02 m day for the newborn inner bar is established the presence of an artificial jetty at the misa river mouth in senigallia finally leaves the bar system typically oscillating around an equilibrium position susceptible to larger seasonal oscillations and strong offshore migration due to two ese storm events numerical simulations of nearshore circulation for two storms from different directions predict the birth of longshore currents higher ratios of significant wave height to water depth and stronger bottom orbital velocities over bars in case of the ese storm suggesting a greater tendency for offshore directed sediment transport

bars bumps and holes models for the generation of complex beach topography in shallow water any two waves of the same frequency are shown to produce complex patterns of drift velocity above the sea bed if the longshore components hi h of the wave numbers of the two waves are different these steady flow patterns exhibit a longshore periodicity of wave number hi h irrespective of whether the waves propagate in the same direction say hi he positive or in opposite directions he negative the interaction of two edge wave modes is examined in detail the drift velocities are calculated and a simple sediment transport model is used to predict the beach topography that would be in equilibrium with these flow patterns as expected crescentic sand bars are produced by the special case of standing edge waves hi h intriguingly for all other cases a combination of complex transverse bars plus meandering or straight offshore bars result patterns that are surprisingly reminiscent of many published descriptions of complex rhythmic topography the extension of the model to three or more waves produces topography that appears to be very irregular although the pattern should repeat over sufficiently long distances along the beach even with only three waves these distances may be very large compared to the scale of the bars

the behaviour of nearshore bars on the time scale of years a conceptual model abstract soundings of the sandy dutch coast have demonstrated the presence of a multiple bar system that exhibits cyclic offshore directed migration on the time scale of years medium term a cycle comprises bar generation interannual offshore migration and decay in this paper we propose a conceptual model in which we qualitatively outline the relationships between short term hourly process knowledge waves currents sediment transport based on a 15 week data set of near bed hydrodynamics obtained in the multiple bar system of terschelling the netherlands and medium term bar behaviour the short term process knowledge is aggregated to the medium term by combining probabilistic characterisations of medium term wave conditions and sediment transports estimated from the short term field measurements essential to the conceptual model is the observed cross shore change in short term conditions that dominate medium term onshore and offshore sediment transport q on and q off respectively in the cross shore direction the conditions contributing most to q on change from predominantly breaking situations outside the bar zone to mainly non breaking conditions on the beach in contrast q off remains restricted to breaking conditions over the entire profile in the model we qualitatively describe how this cross shore change in the forcing conditions results in interannual offshore bar migration bar decay and the onset of the next cycle as such our model may serve as a first step towards a more coherent quantitative model on medium term periodic bar behaviour

short term morphodynamics of an intertidal bar on megatidal ebb delta the morphodynamics of an intertidal bar located on an ebb delta of a megatidal inlet system in normandy france was examined during four short experiments under low to high energy wave conditions and spring or neap tide contexts although there have been numerous studies on ebb tidal bar morphology and on the processes affecting such bars these concern only microtidal or mesotidal settings and are mainly based on observations no detailed work involving hydrodynamic conditions embracing the whole tidal cycle has been carried out so far on the mechanisms of onshore migration of these coastal accumulation features especially along macro and megatidal coasts in this study the morphological response of the bar was coupled with the residence times and intensities of each hydrodynamic process swash surf shoaling waves over a representative bar cross shore profile and sediment transport patterns deduced from fluorescent tracer the results show that the bar migrated exclusively shoreward during moderate to storm conditions hs 0 7 m at the bottom of the bar seaward slope during low energy wave conditions no bar movement was observed swash action was not the dominant process mainly due to its duration which did not exceed 8 min in the course of a semi diurnal tidal cycle the movement of sediments and the bar morphology is induced mainly by surf processes and their associated currents the increase in the significant wave height disturbed the general mean current behaviour which was parallel to the bar crest during low energy conditions under surf conditions mean flows are directed onshore with an absence of bed return flow this allows sediment to be transported towards the bar crest causing a landward bar migration an offshore directed cross shore current not favourable for bar migration is recorded with larger water depths and no breaking waves shoaling conditions this study also highlights the influence of the tidal water level fluctuations in such a large tidal range setting which induce a rapid shift in processes such as bed shear and sediment re working across the shore normal profile these conditions explain the relative low rate of migration of the bar over the delta platform about 33 m year this rate is much less than those reported from micro mesotidal environments calculations of bed shear stress also show that the mean currents alone are not responsible for onshore bar movement notwithstanding the megatidal character of the field site

airflow and sand transport variations within a backshore parabolic dune plain complex ne graham island british columbia canada onshore aeolian sand transport beyond the beach and foredune is often overlooked in the morphodynamics and sediment budgets of sandy coastal systems this study provides detailed measurements of airflow sand transport via saltation and modified suspension vegetation density and surface elevation changes over an extensive 325 30 m swath of a backshore foredune parabolic dune plain complex near surface 30 cm wind speeds on the backshore ranged from 4 3 to 7 3 m s 1 gusting to 14 0 m s 1 oblique onshore flow is steered alongshore near the incipient foredune then landward into a trough blowout where streamline compression flow acceleration to 1 8 times the incident speed and increasing steadiness occur highest saltation rates occur in steady topographically accelerated flow within the blowout as such the blowout acts as a conduit to channel flow and sand through the foredune into the foredune plain beyond the blowout flow expands vegetation roughness increases and flow decelerates over the foredune plain localized flow steering and acceleration to 1 6 times the incident speed occurs followed by a drop to 40 of incident flow speed in a densely vegetated zone upwind of an active parabolic dune at 250 m from the foredune sediment properties reflect variations in near surface flow and transport processes well sorted fine skewed backshore sands become more poorly sorted and coarse skewed in the blowout due to winnowing of fines sorting improves and sands become fine skewed over the foredune plain toward the parabolic dune due to grainfall of finer sands winnowed from the beach and foredune during the fall winter season significant amounts of sand up to 110 kg m 2 are transported via modified suspension and deposited as grainfall up to 300 m landward of the foredune no distinct trend in grainfall was found although most fell on the depositional lobe of the blowout and at 200 m near an isolated active parabolic dune grainfall amounts may reflect several transporting events over the measurement period and the transport process is likely via localized modified suspension from the crest of the foredune and other compound dune features in the foredune plain this evidence suggests that the process of grainfall delivery though often overlooked in coastal research may be a key process in maintaining active dunes hundreds of metres from the shoreline in a densely vegetated foredune plain the effectiveness of this process is controlled by seasonal changes in vegetation cover and wind strength as well as shorter term e g tidally controlled variations in sand availability from the beach

effective timescales of coupling within fluvial systems this paper presents a review of the coupling concept in fluvial geomorphology based mainly on previously published work coupling mechanisms link the components of the fluvial system controlling sediment transport down the system and the propagation of the effects of base level change up the system they can be viewed at several scales at the local scale involving within hillslope coupling hillslope to channel coupling and within channels tributary junction and reach to reach coupling at larger scales coupling can be considered as zonal coupling between major zones of the system or as regional coupling relating to complete drainage basins these trends are illustrated particularly by the examples of hillslope to channel coupling in the howgill fells northwest england badland systems in southeast spain alluvial fans in spain usa and uae and base level induced dissection of neogene sedimentary basins in southeast spain as the spatial scales increase so do the timescales involved effective temporal scales relate to magnitude and frequency characteristics recovery time and propagation time the relative importance changing with the spatial scale for downsystem coupling at the local scale the first two are important with propagation time increasing in importance in larger systems especially in those involving upsystem coupling related to base level change the effective timescales range from the individual event with a return period of decades through decadal to century timescales for downsystem coupling to tens to hundreds of thousands of years for the basinwide response to base level change the effective timescales influence the relative importance of factors controlling landform development

morphometric characterization of foredunes along the coast of northern spain abstract foredunes are defined as the first shore parallel dune ridges adjacent to stable and prograding beaches formed on the backshore by aeolian sand deposition influenced by vegetation foredunes have the important functions for mitigating impacts caused by extreme events providing sediment to the beaches during storm and accumulating sediment again under fair weather wave conditions mainly for this reason there is currently great interest in preserving building or recovering foredunes on a long term timescale decades foredunes are recognized as exhibiting possible equilibrium conditions the identification of this condition is of interest to projects involving the recovery and creation of foredune beach systems therefore the main objective of this work is to identify the morphometric characteristics of equilibrium foredunes and the interrelations between the morphometric parameters of height width volume and maximum slope allometric relationships to reach this objective 193 foredune subaerial beach profiles from along the northern coast of spain that have characteristics close to equilibrium conditions were evaluated the results indicate that foredune size can vary significantly however strong correlations between morphometric parameters have been verified and allometric relationships between foredune volume height width and maximum slope are proposed

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

short term morphological change and sediment dynamics in the intertidal zone of a macrotidal beach abstract this paper describes the morphological and sedimentological evolution of amacrotidal beach over a 20 day period under varying hydrodynamicconditions signi cant breaker heights of 0ae3 2 m and tidal ranges of 2 5 m during the eld campaign an intertidal bar developed around the mid tidelevel migrated onshore welded to the upper beach and was then attenedunder energetic wave conditions the bar had a wave breakpoint origin and itsformation was triggered by a reduction in tidal range causing more stationarywater level conditions rather than an increase in wave height most of theonshore bar migration took place while the bar was positioned in the inner tomid surf zone position such that the bar moved away from the breakpoint andexhibited divergent behaviour the depth of disturbance over individual tidalcycles was 10 20 of the breaker height such values are more typical of steepre ective beaches than gently sloping dissipative beaches and are consideredto re ect the maximum height of wave generated ripples the grain sizedistribution of sur cial sediments did not vary consistently across the beachpro le and temporal changes in the sedimentology were mostly unrelated tothe morphological response the lack of clear links between beach morphologyand sedimentology may be in part due to shortcomings in the samplingmethodology which ignored the vertical variability in the sediment sizecharacteristics across the active layer keywords beach sediment depth of disturbance intertidal bar macrotidalbeach morphology introductionbeaches respond rapidly to changing wave andtide conditions through the redistribution of theirsediments by oscillatory and quasi steady cur rents resulting in spatial patterns of erosion sediment divergence and accretion sedimentconvergence given suf cient time these bed level changes modify the beach shape by theformation modi cation destruction and ormigration of secondary morphological features such as berms beach cusps swash bars ripchannels and nearshore bars the dynamics ofthese secondary morphological features and theirrole in affecting beach stability has been a majorfocus of beach research over the last few decades e g komar 1998 short 1999 most short term days to weeks eld investi gations addressing the morphological response ofsandy beaches to wave and tide forcing have beenconducted in microtidal or mesotidal settings beaches in macrotidal settings have on the otherhand only received limited attention despitetheir common occurrence short 1991 a mainreason for this imbalance is that macrotidalbeaches are often planar and lack pronouncedsecondary morphological features indeed theonly type of macrotidal beach that does featureprominently in the coastal literature is the ridgeand runnel beach which is characterized bysedimentology 2007 54 39 53

mean currents and sediment transport in a rip channel measurements of hydrodynamics and suspended sediment transport were carried out along a cross shore transect in a rip channel a tidally induced threshold for rip flow initiation was found this threshold depended upon the degree of wave energy dissipation and could be identified through a critical value of the ratio of significant wave height to water depth s in the rip neck with normally incident waves rip current velocities were well correlated with velocities predicted from a simple model involving the onshore mass transport in asymmetric breaking waves crossing the bar hydrodynamics and sediment transport were tidally modulated with strong offshore directed rip currents and associated offshore sediment transport due to the mean flow at low tide at high tide when the rip was inactive the tendency was for weak onshore directed mean flows and or oscillatory incident waves transporting smaller amounts of sediment landward the net result was a gradual lowering of the topographic relief along the rip channel with net deposition seaward of the rip outside the surf zone transport was mainly landward due to oscillatory incident waves

proxy records of holocene storm events in coastal barrier systems storm wave induced markers abstract extreme storm events in the coastal zone are one of the main forcing agents of short term coastal system behavior as such storms represent a major threat to human activities concentrated along the coasts worldwide in order to better understand the frequency of extreme events like storms climate science must rely on longer time records than the century scale records of instrumental weather data proxy records of storm wave or storm wind induced activity in coastal barrier systems deposits have been widely used worldwide in recent years to document past storm events during the last millennia this review provides a detailed state of the art compilation of the proxies available from coastal barrier systems to reconstruct holocene storm chronologies paleotempestology the present paper aims i to describe the erosional and depositional processes caused by storm wave action in barrier and back barrier systems i e beach ridges storm scarps and washover deposits ii to understand how storm records can be extracted from barrier and back barrier sedimentary bodies using stratigraphical sedimentological micro paleontological and geochemical proxies and iii to show how to obtain chronological control on past storm events recorded in the sedimentary successions the challenges that paleotempestology studies still face in the reconstruction of representative and reliable storm chronologies using these various proxies are discussed and future research prospects are outlined