meso scale transfer of sand during and after storms implications for prediction of shoreline movement abstract monitoring beach volume changes of the texas coast following a major hurricane reveals the impact of storms on sand dispersal and shoreline movement at spatial and temporal scales encompassing tens of kilometers and decades beach volume histories at profile sites show the interdependence of sand exchange among adjacent sites and the spatial autocorrelation of sand movement beach volume histories also indicate periods when either longshore or cross shore transport predominate and illustrate the long term effects of coastal structures on beach mobility this study confirms that net losses of sand from updrift barriers may not be directly linked with net gains of sand on adjacent downdrift barriers instead sand dispersal within a coastal compartment may depend partly on the dynamics of shoals and temporary sand storage at the intervening tidal inlet in our study sand eroded from the updrift barrier galveston island is deposited in a terminal sand flat of the barrier whereas sand accreted to the downdrift barrier follets island is derived from the intermediate ebb tidal delta san luis pass unlike continuous sand bypassing on some microtidal wave dominated coasts sand bypassing at san luis pass is episodic event driven and inefficient and sand is not transferred directly from one barrier to the next p because storms rapidly redistribute beach sediment they can be the most important factor controlling short term

circulation phenomena and frontal dynamics of the norwegian coastal current after a short general description of the norwegian coastal current some recent investigations concerning its variability are reviewed the variability caused by meteorological effects and fresh water fluxes is shown to be the dominant feature the coastal current not only responds to local wind forcing but is also a signal channel of sea level variations in the north sea as a whole the variability at times manifests itself as mesoscale waves and eddies the subsurface frontal region is characterized by interleaving of coastal and atlantic water and strong mixing lateral and longitudinal frontal motions are dealt with in relation to plumes of brackish water from the fjords and outbreaks of brackish and or warm water masses from the skagerrak the inflow of atlantic water through the norwegian trench and the formation of deep and bottom water in skagerrak are discussed

dune cliff erosion and beach width change at the northern and southern spits of sylt detected with multi temporal lidar abstract since the end of pleistocene the west coast of sylt germany has been a very dynamic geomorphic system at present especially the northern and southern spits ellenbogen and hornum odde are changing rapidly airborne lidar light detection and ranging has been used since 1999 to measure the coast inter and intra annually the aim of this study is to exploit the potential of the laser data to describe and explain the changes at the west coast of the northern and southern spits of sylt lidar accuracy verification approves the value of the data after offset correction a horizontal difference of 0 5 m and a maximal vertical difference of 0 12 m remain dune cliff changes are monitored by applying semi automatic breakline extraction procedures to multi temporal lidar data the breakline extraction is based on filter methods derived from digital image analysis furthermore beach width changes are analyzed at the hornum odde and at the ellenbogen a maximal dune retreat of 140 m and 70 m respectively was measured different annual as well as seasonal coastal change patterns could be revealed dunes are only eroded during winter due to storm surges while the beach width varies during all seasons due to generally high shoreline dynamics beach width influences dune cliff erosion differently at the two study sites at the west coast of the northern spit backshore dunes are eroded suddenly after an enduring period of general beach width decrease afterwards beach width increases and cliff position stabilizes again beach nourishment can protect the dunes due to beach width preservation at the west coast of the southern spit local interactions dominate expanded beach segments cause lee effects and hence dune erosion different beach nourishment projects could not avoid dune erosion

wave beach and dune interactions in southeastern australia abstract a morphodynamic classification of surfzones beaches and dunes of the microtidal low to high energy southeast australian coast is presented the first section a waves and beaches briefly deals with the transformation of deep water wave energy as it crosses the shelf nearshore and surfzone depending on the deep water wave characteristics and shelf and inshore morphology resultant breaker wave energy may be high moderate or low and the accompanying beach surfzone morphodynamic state in fine to medium sand beaches either dissipative intermediate or reflective dissipative beaches have wide surfzones with shore parallel bar s and channel s and predominantly shore normal circulation intermediate beaches are characterised by rip circulation crescentic transverse bars and megacusps and reflective beaches by a barless surfzone and steep cusped or bermed beach each beach form has a characteristic level of beach stability zone of sediment storage and mode of beach and dune erosion landward aeolian sediment transport of swash deposited sand section b is dependent on the subaerial beach topography and the aerodynamic flow regime across that topography characteristic profile shapes are ascribed to each beach type dissipative intermediate and reflective aeolian sand transport rates are potentially highest on dissipative beaches moderate on intermediate beaches and lowest on reflective beaches these rates determine the potential size of foredunes which are correspondingly largest on dissipative beaches and smallest on reflective beaches the combination of mode and frequency of beach dune erosion rates of aeolian sand transport and foredune volume and morphology provide an explanation of the nature and morphology of landward occurring large scale dune systems dissipative beaches are frequently characterised by large scale transgressive dune sheets intermediate by a trend from large scale parabolic dune systems high wave energy to small scale blowouts low wave energy and reflective beaches by minimal dune development

mainland influence on coastal transgression delmarva peninsula abstract the morphology of present day barrier beaches and lagoons along delmarva peninsula is controlled by wave climate tidal energy sediment texture and sand supply however morphology is also affected by coastal plain physiography largely the product of pleistocene sea level change over the last million years five distinct transgressive coastal systems have been identified on delmarva peninsula using geomorphic and subsurface data each was produced during interglacial high sea levels and range in age from over one million years to 60 000 yrs b p eroding pre holocene sediments represent major sand sources for present day beaches baymouth barriers that formed adjacent to eroding headlands such as bethany beach delaware are characterized by infrequent inlets and robust dune systems the mainland lagoonal shoreline follows the contours of the incised paleodrainage system to the south a long continuous barrier with infrequent inlets is present where littoral drift maintains a high sediment supply further south and away from this primary source of sand short drumstick islands exist this barrier chain is the result of the present transgression of a pre existing 60 000 yr old shoreface the mainland lagoonal shoreline follows the trend of pleistocene beaches which have experienced only minor stream dissection due to their young age along the southern part of the peninsula sea level rise will eventually cause holocene barriers to be welded onto the ancient barrier shore the mainland whereas to the north baymouth barriers will persist as the well developed paleo drainage system is flooded farther inland

persistent shoreline shape induced from offshore geologic framework effects of shoreface connected ridges mechanisms relating offshore geologic framework to shoreline evolution are determined through geologic investigations oceanographic deployments and numerical modeling analysis of shoreline positions from the past 50 years along fire island new york a 50 km long barrier island demonstrates a persistent undulating shape along the western half of the island the shelf offshore of these persistent undulations is characterized with shoreface connected sand ridges sfcr of a similar alongshore length scale leading to a hypothesis that the ridges control the shoreline shape through the modification of flow to evaluate this a hydrodynamic model was configured to start with the us east coast and scale down to resolve the fire island nearshore the model was validated using observations along western fire island and buoy data and used to compute waves currents and sediment fluxes to isolate the influence of the sfcr on the generation of the persistent shoreline shape simulations were performed with a linearized nearshore bathymetry to remove alongshore transport gradients associated with shoreline shape the model accurately predicts the scale and variation of the alongshore transport that would generate the persistent shoreline undulations in one location however the ridge crest connects to the nearshore and leads to an offshore directed transport that produces a difference in the shoreline shape this qualitatively supports the hypothesized effect of cross shore fluxes on coastal evolution alongshore flows in the nearshore during a representative storm are driven by wave breaking vortex force advection and pressure gradient all of which are affected by the sfcr

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

the importance of extratropical and tropical cyclones on the short term evolution of barrier islands along the northern gulf of mexico usa abstract data are presented indicating the complexity and highly variable response of beaches to cold front passages along the northern gulf of mexico in addition to the impacts of tropical cyclones and winter storms within the past decade an increase in the frequency of tropical storms and hurricanes impacting the northern gulf has dramatically altered the long term equilibrium of a large portion of this coast a time series of net sediment flux for subaerial and nearshore environments has been established for a section of this coast in florida and to a lesser extent mississippi the data incorporate the morphological signature of six tropical storms hurricanes and more than 200 frontal passages data indicate that 1 barrier islands can conserve mass during catastrophic hurricanes e g hurricane opal a strong category 4 hurricane near landfall 2 less severe hurricanes and tropical storms can promote rapid dune aggradation and can contribute sediment to the entire barrier system 3 cold fronts play a critical role in the poststorm adjustment of the barrier by deflating the subaerial portion of the overwash terrace and eroding its marginal lobe along the bayside beach through locally generated high frequency steep waves and 4 barrier systems along the northern gulf do not necessarily enter an immediate poststorm recovery phase although nested in sediment rich nearshore environments while high wave energy conditions associated with cold fronts play an integral role in the evolution and maintenance of barriers along the northern gulf these events are more effective in reworking sediment after the occurrence of extreme events such as hurricanes this relationship is even more apparent during the clustering of tropical cyclones it is anticipated that these findings will have important implications for the longer term evolution of barrier systems in midlatitude microtidal settings where the clustering of storms is apparent and winter storms are significant in intensity and frequency along the coast

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

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

the dynamic effects of moisture on the entrainment and transport of sand by wind abstract there is an increasing awareness of the influence of surface moisture on aeolian entrainment and transport of sediment existing wind tunnel studies have shown the impact of a limited range of moisture contents on entrainment thresholds but similar investigations are lacking in the field the research reported here investigated the influence of changes in surface moisture content on sand entrainment and transport on a meso tidal beach in anglesey north wales high frequency 1 hz wind velocities measured with hot wire anemometers were combined with grain impact data from a sensit monitor and mass flux measurements from a standard sand trap surface and near surface moisture contents were assessed gravimetrically from surface sand scrapes and also directly by using a thetaprobe critical threshold values for entrainment were specified using a modified form of the time fraction equivalence method stout j e zobeck t m 1996a establishing the threshold condition for soil movement in wind eroding fields proceedings of the international conference on air pollution from agricultural operations mwps c 3 kansas city 7 9 february 1996 pp 65 71 results indicate a time dependent change in dominant control of the sand transport system from moisture to wind speed dependent upon the moisture content of the surface sediment this interchange between controlling parameters on both entrainment and transport was very sensitive to prevailing moisture conditions and took place over a period of minutes to hours under conditions experienced in the experiments presented here the critical moisture threshold for sediment entrainment was determined to be between 4 and 6 higher than the 1 4 specified in previous wind tunnel experiments furthermore a moisture content of nearly 2 where moisture was adhered to transported sediment appeared to have little or no impact on the rate of sand flux

decoupling processes and scales of shoreline morphodynamics abstract behavior of coastal systems on time scales ranging from single storm events to years and decades is controlled by both small scale sediment transport processes and large scale geologic oceanographic and morphologic processes improved understanding of coastal behavior at multiple time scales is required for refining models that predict potential erosion hazards and for coastal management planning and decision making here we investigate the primary controls on shoreline response along a geologically variable barrier island on time scales resolving extreme storms and decadal variations over a period of nearly one century an empirical orthogonal function analysis is applied to a time series of shoreline positions at fire island ny to identify patterns of shoreline variance along the length of the island we establish that there are separable patterns of shoreline behavior that represent response to oceanographic forcing as well as patterns that are not explained by this forcing the dominant shoreline behavior occurs over large length scales in the form of alternating episodes of shoreline retreat and advance presumably in response to storms cycles two secondary responses include long term response that is correlated to known geologic variations of the island and the other reflects geomorphic patterns with medium length scale our study also includes the response to hurricane sandy and a period of post storm recovery it was expected that the impacts from hurricane sandy would disrupt long term trends and spatial patterns we found that the response to sandy at fire island is not notable or distinguishable from several other large storms of the prior decade

morphological changes beach inundation and overwash caused by an extreme storm on a low lying embayed beach bounded by a dune system nw mediterranean abstract the geomorphological evolution of a low lying micro tidal sandy beach in the western mediterranean pals beach was characterized using airborne light detection and ranging lidar data data were collected in prior to and six months after the impact of an extreme storm with a return period of approx 50 years with the aim of characterizing the beach s response to the storm the use of repeated high resolution topographic data to quantify beach geomorphic changes has allowed assessment of the accuracy of different proxies for estimating beach volume changes results revealed that changes in the shoreline position cannot accurately reproduce beach volume changes on low lying beaches where overwash processes are significant observations also suggested that volume estimations from beach profiles do not accurately represent subaerial volume changes at large profile distances on beaches with significant alongshore geomorphological variability accordingly the segmentation of the beach into regularly spaced bins is proposed to assess alongshore variations in the beach volume with the accuracy of the topographic data the morphological evolution of pals beach during the study period showed a net shoreline retreat 4 m and a significant sediment gain on the subaerial beach 7 5 m 3 m the net gain of sediment is mostly due to the impact of the extreme storm driving significant overwash processes that transport sediment landwards increasing volume on the backshore and dunes the increase of volume on the foreshore and the presence of cuspate morphologies along the shoreline also evidence post storm beach recovery observed morphological changes exhibit a high variability along the beach related to variations in beach morphology changes in the morphology and migration of megacusps result in a high variability in the shoreline position and foreshore volume changes on the other hand larger morphological changes on the backshore and larger inundation distances occur when the beach and the dunes are lower favouring the dominance of overwash the observed storm induced morphological changes differ from predicted beach storm impacts because of spatial and temporal variations in the beach morphology suggesting that detailed morphological parameters and indicators used for predicting beach vulnerability to storms should be regularly updated in order to represent the pre storm beach conditions finally observed morphological changes in pals bay evidenced a different behaviour between natural and urban areas with better post storm beach recovery on natural areas where the beach is not artificially narrowed

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

wave field modification by bathymetric anomalies and resulting shoreline changes a review with recent results this paper provides a review of available studies on wave transformation by bathymetric changes and the resulting shoreline impacts three case studies of beach nourishment projects with significant nearshore borrow areas are examined grand isle louisiana constructed in 1984 anna maria key florida in 1993 and martin county florida in 1996 a review is presented of field and laboratory scale studies that have examined the impact of offshore pits on the local wave field and sediment dynamics solutions for wave transformation by changes in bathymetry are outlined primarily in chronological order following the development from analytical solutions for long waves in one horizontal dimension 1 d through numerical models for arbitrary bathymetry that include many wave related nearshore processes modeling of shoreline responses due to wave field modification owing to changes in offshore bathymetry is examined with models that include both wave field and shoreline changes and by coupling models that evaluate these processes independently the wave transformation processes included in nearshore models are important factors in the capability to predict a salient leeward of a pit the shoreline responses observed in the limited laboratory experiments and at grand isle la

spatial characterization resolution and volumetric change of coastal dunes using airborne lidar cape hatteras north carolina the technological advancement in topographic mapping known as airborne light detection and ranging lidar allows researchers to gather highly accurate and densely sampled coastal elevation data at a rapid rate the problem is to determine the optimal resolutions at which to represent coastal dunes for volumetric change analysis this study uses digital elevation models dem generated from lidar data and spatial statistics to better understand dune characterization at a series of spatial resolutions the lidar data were collected jointly by the national aeronautics and space administration nasa the national oceanic and atmospheric administration noaa and the u s geological survey usgs dems of two study sites 100 200 m located in cape hatteras national seashore north carolina were generated using a raster based geographic information system gis changes in the dune volume were calculated for a 1 year period of time fall 1996 1997 at grid cell resolutions ranging from 1 1 to 20 20 m directional statistics algorithms were used to calculate local variance and characterize topographic complexity data processing was described in detail in order to provide an introduction to working with lidar data in a gis results from these study sites indicated that a 1 2 m resolution provided the most reliable representation of coastal dunes on cape hatteras and most accurate volumetric change measurements results may vary at other sites and at different spatial extents but the methods developed here can be applied to other locations to determine the optimum resolutions at which to represent and characterize topography using common gis and database software

is barrier island morphology a function of tidal and wave regime abstract classification of barrier island morphology stems from the seminal work of m o hayes and others which linked island shape to tidal range and wave height and defined coastal energy regimes i e wave dominated mixed energy tide dominated if true this general relationship represents a process based framework to link modern and ancient systems and is key for determining paleomorphodynamic relationships here we present a new semi global database of barrier islands and spits n 702 shape parameters aspect circularity and roundness are used to quantify island boundary shape and assess potential correlation with coastal energy regime using global wave and tide models in adopting the original energy classification as originally put forth i e wave dominated wave influenced mixed tide influenced mixed tide dominated results show that wave dominated islands have statistically different mean shape values from those in the mixed energy fields but the two mixed energy designations are not distinct from each other furthermore each energy regime field contains a wide range of island shapes with no clear trends present linear regression modeling shows that tidal range and wave height account for

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

foredune morphodynamics and sediment budgets at seasonal to decadal scales humboldt bay national wildlife refuge california usa abstract coastal foredunes are shore parallel ridges that form in the backshore and their morphodynamics are controlled partly by seasonal and spatial variations in the coastal onshore sediment budget that in turn are driven by oceanic and atmospheric processes and interactions including regional wave and wind regimes climatic variability events e g enso sediment availability beach characteristics e g width slope and vegetation type and cover in the backshore previous studies on shoreline change in northern california report only broad rates of erosion and accretion related to regional meteorological regimes this study presents a more detailed multi decadal to seasonal account of shoreline response and foredune morphodynamics along a 2 5 km stretch of coast in the humboldt bay national wildlife refuge hbnwr analysis of historical aerial photography 1939 2014 reveals trends in shoreline position that are coupled with more detailed assessments of foredune morphodynamics and seasonal scale volumetric changes from cross shore topographic profiles these findings set the historical context of foredune morphodynamics and allow exploration of the implications of seasonal meteorological variation on long term 75 year foredune evolution and development at the hbnwr dsas describes maximum foredune progradation in the north up to 0 51 m a 1 and maximum foredune retreat in the south up to 0 49 m a 1 aerial photograph analysis 2004 2014 shows statistically significant larger erosive features in the southern zone than in the northern and central zones seasonal volume calculations from cross shore profiles indicate statistically significant differences in alongshore transect elevation and foredune volume with larger elevations and volumes in the northern and central zones than in the southern combined with evidence of seasonal bidirectional littoral drift these data support a north to south gradient in sediment availability foredune position and resulting stages of established foredune development seasonal storm energies and climate forcing events introduce variability in erosive patterns but support the persistence of alongshore developmental stages future research should explore foredune morphodynamics on a smaller spatial scale and changes related to the presence absence of multiple vegetation assemblages

development of deflation lag surfaces a series of wind tunnel tests were carried out to investigate the development of deflation lags in relation to the non erodible roughness element concentration glass spheres 18 mm in diameter were placed along the complete length of the wind tunnel working section in regular staggered arrays using three different spacings d 18 30 and 60 mm and completely covered with a 0 27 mm erodible sand a pre selected free stream velocity above threshold 8m s 1 was established above the surface and the sediment transport measured at 2 s intervals using a wedge shaped trap in which an electronic balance is incorporated throughout each test the emerging lag surface was periodically photographed from above at two locations upwind of the trap the photographs were electronically scanned and analysed to calculate the lag element coverage and location as well as mean height and frontal area for each time period test results indicate that lag development has a profound effect on both the sediment flux and wind profile characteristics initially there is an increase in sediment flux above that for a rippled sand bed because of increased erosion around and reduced kinetic energy loss in highly elastic collisions with the emerging roughness elements with further emergence a dynamic threshold is reached whereupon the sediment flux decreases rapidly tending towards zero at this point the supply of grains to the air stream through fluid drag follows a reduction in aerodynamic roughness and therefore surface shearing stress at least as important is the lesser potential for grain ejection at impact because of reduced momentum imparted from the air stream during saltation although recent shear stress partitioning models indicate when particle movement may commence on varying surfaces our experimental results demonstrate that this partitioning has a further direct bearing upon the saltation flux ratio

assessing the impact of extreme storms on barrier beaches along the atlantic coastline application to the southern rhode island coast abstract in this work we use the 2d model xbeach to dynamically simulate coastal erosion due to a synthetic 100 year storm impacting a typical north atlantic barrier beach located in southern ri this storm was extracted from the north atlantic coast comprehensive study naccs database based on results of an extreme value analysis of more than 1000 naccs storms xbeach parameters are first calibrated validated by simulating hurricane irene august 2011 for which both nearshore wave data and pre and post storm beach profiles were available in the study area comparing results to observations allowed calibration of the wave asymmetry and skewness parameter u a 0 3 in the model resulting in a 6 mean relative error between the simulated and measured subaerial eroded volumes along 4 transects in the 100 year storm xbeach simulations that include overwash effects of land cover on beach erosion in particular vegetation are assessed by specifying a spatially varying bed friction function of high resolution land cover results show that healthy back dune vegetation is essential to prevent the dune crest from being fully eroded down to its toe level the predicted median 100 year eroded volume is 46 m3 m for the entire barrier beach in good agreement with fema s empirical value of 50 m3 m at the two official 1d transects within the study area mean post storm reductions in dune crest elevations are in similar agreement the model however predicts very large alongshore variations of these parameters with eroded volumes over 1000 m3 m where breaching and the opening of surge channels occurs overall dune segmentation simulated in the model for the 100 year storm appears to be realistic and consistent with dune topography and land cover xbeach thus provides an improved 2d methodology for assessing the impact of extreme storms on atlantic barrier beaches predicting changes in dune morphology and quantifying the protective role of vegetation and effects of land cover in general

relationship between beach profiles and waves at duck north carolina determined by canonical correlation analysis abstract an 11 year long measurement time series of waves and profiles from duck north carolina was analyzed using canonical correlation analysis cca in order to determine the covariability between waves and profile response the main objectives of this analysis were 1 to detect simultaneously occurring patterns in the wave and profile data and if possible give such patterns a physical interpretation to increase the insight into the governing processes and 2 to investigate the possibility to use cca in a predictive mode with the aim to calculate the profile response from the waves the profile shape itself and the change between consecutively surveyed profiles were correlated with both the offshore deep water and nearshore wave conditions in the offshore the waves were described by composite probability density functions pdf derived based on the measured wave conditions prior to a profile survey nearshore wave conditions were calculated using a random breaker decay model and averaged local wave properties were used as input to the cca the profile response displayed significantly higher correlation with the nearshore wave properties as compared to the offshore waves and the highest correlation was found between the profile shape and the mean ratio of breaking waves for the time period preceding the profile survey the cca using nearshore wave properties indicates a potential for predicting the profile response with an acceptable degree of accuracy once a regression matrix relating the profiles to the waves has been established that represents the typical variability at the site

coastal engineering applications of high resolution lidar bathymetry abstract in 1994 the us army corps of engineers completed development of the scanning hydrographic operational airborne lidar survey shoals system a state of the art hydrographic survey instrument using lidar light detection and ranging technology and operating from a bell 212 helicopter shoals remotely collects accurate high resolution bathymetry at a rate of 8 km2 h a nominal depth and position measurement spacing of 4 m yields high density bottom coverage of coastal projects producing soundings from the above water beach or coastal structure to depths of 40 m since becoming fully operational shoals surveyed over 2000 km2 along the atlantic ocean pacific ocean gulf of mexico great lakes and caribbean sea survey projects varied from tidal inlets and navigation channels to beach nourishment and monitoring these projects quantify current coastal structure condition navigation channel alignments and morphologic changes over time in addition to monitoring coastal projects sediment transport can be estimated with accurate high resolution bathymetry bathymetry can be translated into sediment transport through a combination of the sediment continuity equation a surf zone energetics based longshore transport formula and bathymetric data this paper presents the shoals system describing both lidar technology and the survey system several shoals data sets are presented to show today s benefits of high resolution lidar bathymetry to the coastal engineering community finally ongoing research using these unique data sets is presented to show the future benefits of lidar bathymetry to the coastal field

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

hydrodynamics and sediment transport within the inner surf zone of a lacustrine multiple barred nearshore abstract it has become increasingly recognized that the typically unexpected behavior of the nearshore profile over a sequence of storm events is a response to strong feedback between the antecedent morphology and the incident wave field this paper systematically examines the suspended sediment transport and morphodynamics within the surf zone of a lacustrine multiple barred upper shoreface a range of significant wave heights h s and local relative wave heights h s h 1 h water depth are considered in order to describe and identify the limits to the feedback mechanisms that can dominate the nearshore response data from collocated concentration and velocity sensors indicate that the direction and magnitude of suspended sediment transport varies with the degree of local wave energy dissipation and the cross shore variation in these relationships depends partly on the local bed slope this dependence indicates the presence of a strong self organization at the scale of the individual bar within the inner surf zone these bar scale relationships are constrained by the shoaling transformations which occur over the outermost bar for ranges of incident wave height defined locally e g intermediate waves h s 0 4 to 0 9 m storm waves 0 9 to 1 4 m the innermost and middle bars remain in a state of self organized equilibrium for intermediate range waves this equilibrium is a consequence of wave height reduction over the outer bar through breaking and the generation of secondary harmonic waves for the storm wave range the equilibrium is maintained through a resonant amplification of discrete edge wave modes with the bars forced to a position coincident with the surface elevation antinodes these upper shoreface scale feedback mechanisms are weakened particularly for intermediate wave heights following threshold storms capable of moving the outermost bar offshore and lower on the profile this allows the middle and inner bars to be forced directly by variations in the offshore incident waves thus the bars respond in a cyclic manner the bar cycle

palaeohurricane reconstructions from sedimentary archives along the gulf of mexico caribbean sea and western north atlantic ocean margins hurricanes annually threaten the atlantic ocean margins historical hurricane records are relatively short and palaeohurricane sedimentary archives provide a geological and climatic context that sheds light on future hurricane activity here we review palaeo trends in hurricane activity elucidated from sedimentary archives we discuss dating methods site selection and stat istics associated with previously published records these archives have been useful for under standing the long term evolution of coastal systems and the response of intense hurricane activity to climatic changes regional shifts in hurricane overwash on centennial to millennial timescales have been linked to various climatic modes of variability including el nino southern oscillation and the north atlantic oscillation but could also reflect regional scale controls on hurricane activity

effects of beach raking and sand fences on dune dimensions and morphology abstract raking beaches to remove wrack natural and human litter to enhance recreational use and using sand fences to build and stabilize dunes are common practices on developed shores but their effects on the landscape are not well understood managers in avalon nj ceased using sand fences and raking in a portion of beach in 1991 providing the opportunity to evaluate evolution of natural and managed dune systems over a 19 year period topographic and vegetation characteristics were evaluated on 15 transects within 5 sites in a managed area where raking and sand fences are still used and at 15 transects within 5 sites in a naturally evolving unmanaged area raking and deploying fences in the managed area restricted the size of the cross shore zone in which aeolian accretion occurred but resulted in greater dune crest heights than in the unmanaged area crest heights of the foredune in the managed area ranged from 4 45 m to 5 27 m crest heights in the unmanaged area ranged from 3 02 m to 4 27 m dune volume and beach volume were greater on average in the unmanaged area and the dune was wider mean of 72 m versus 40 m and had an additional ridge the unmanaged area had 35 more species and contained a greater percentage of all species encountered in the study area than the managed area 88 compared to 65 more species occurred in the swales than any other of the cross shore habitats and most of these species were observed in the deeper wider swales in the unmanaged area removing wrack from the beach prevents incipient dunes from forming thus reducing the number of dune crests and size of swales that create topographic variability and increase the number and types of habitats for flora and fauna suspension of raking can allow the dunes to build seaward while producing a greater variety and number of habitats but seaward growth does not mean that the height of the dune will increase substantially and fences may be needed to build an initial dune ridge for flood protection thereafter a policy of not raking in specially designated zones would be a good compromise between the need to accommodate nature and beach recreation

a comparison of two spectral wave models in the southern california bight abstract two models a spectral refraction model longuet higgins and a parabolic equation method pem refraction diffraction model kirby are used to simulate the propagation of surface gravity waves across the southern california bight the bight contains numerous offshore islands and shoals and is significantly larger 300 km by 300 km than regions typically studied with these models the effects of complex bathymetry on the transformation of incident wave directional spectra s0 f 0 which are very narrow in both frequency and direction are difficult to model accurately as s0 f 0 becomes broader in both dimensions agreement between the models improves and the spectra predicted at coastal sites become less sensitive to errors in the bathymetry grid to tidal changes in the mean water depth and to uncertainty in s0 f 0 itself the smoothing associated with even relatively narrow 0 01 hz 5 bandwidth s0 f 0 is usually sufficient to bring the model predictions of shallow water energy into at least qualitative agreement however neither model is accurate at highly sheltered sites the importance of diffraction degrades the predictions of the refraction model and a positive bias o 10 of the deep ocean energy in the refraction diffraction model estimates believed to stem from numerical noise kirby may be comparable to the low wave energy the best agreement between the predicted spectra generally occurs at moderately exposed locations in deeper waters within the bight away from shallow water diffractive effects and in the far field of the islands in these cases the differences between the models are small comparable to the errors caused by tidal fluctuations in water depth as waves propagate across the bight the accuracy of predicted energies at these sites is likely to be limited by the uncertainty in specifying s0 f 0

variations in the response of the dune coast of northern france to major storms as a function of available beach sediment volume a series of airborne topographic lidar data were obtained from may 2008 to january 2014 over two coastal sites of northern france bay of wissant and east of dunkirk these data were used with wind and tide gauge measurements to assess the impacts of storms on beaches and coastal dunes and particularly of the series of major storms that hit western europe during the fall and early winter of 2013 our results show a high variability in shoreline response from one site to the other but also within each coastal site coastal dune erosion and shoreline retreat occurred at both sites particularly on the coast of the bay of wissant where shoreline retreat up to about 40 m was measured however stability or even shoreline advance were also observed despite the occurrence of an extreme water level with a return period 100 years during the storm xaver in early december 2013 comparison of shoreline change with variations of coastal dune and upper beach volumes revealed only weak relationships our results nevertheless showed that shoreline behavior seems to strongly depend on the initial sediment volume on the upper beach before the occurrence of the storms according to our measurements an upper beach volume of about 30 m3 m 1 between the dune toe and the mean high water level is sufficient at these sites to protect the coastal dunes from storm waves associated with high water levels with return periods 10 years the identification of such thresholds in terms of upper beach width or sediment volume may represent valuable information for improving the management of shoreline change by providing an estimate of the minimum quantity of sand on the upper beach necessary to ensure shoreline stability in this region copyright 2016 john wiley sons ltd

a parameterisation for the threshold shear velocity to initiate deflation of dry and wet sediment abstract a new parameterisation for the threshold shear velocity to initiate deflation of dry and wet particles is presented it is based on the balance of moments acting on particles at the instant of particle motion the model hence includes a term for the aerodynamic forces including the drag force the lift force and the aerodynamic moment force and a term for the interparticle forces the effect of gravitation is incorporated in both terms rather than using an implicit function for the effect of the aerodynamic forces as reported earlier in literature a constant aerodynamic coefficient was introduced from consideration of the van der waals force between two particles it was further shown that the effect of the interparticle cohesion force between two dry particles on the deflation threshold should be inversely proportional to the particle diameter squared the interparticle force was further extended to include wet bonding forces the latter were considered as the sum of capillary forces and adhesive forces a model that expresses the capillary force as a function of particle diameter squared and the inverse of capillary potential was deduced from consideration of the well known model of fisher and the young laplace equation the adhesive force was assumed to be equal to tensile strength and a function which is proportional to particle diameter squared and the inverse of the potential due to adhesive forces was derived by combining the capillary force model and the adhesive force model the interparticle force due to wet bonding was simplified and written as a function of particle diameter squared and the inverse of matric potential the latter was loglinearly related to the gravimetric moisture content a relationship that is valid in the low moisture content range that is important in the light of deflation of sediment by wind by introducing a correction to force the relationship to converge to zero moisture content at oven dryness the matric potential moisture content relationship contained only one unknown model parameter viz moisture content at 1 5 mpa working out the model led to a rather simple parameterisation containing only three coefficients two parameters were incorporated in the term that applies to dry sediment and were determined by using experimental data as reported by iversen and white sedimentology 29 1982 111 the third parameter for the wet sediment part of the model was determined from wind tunnel experiments on prewetted sand and sandy loam aggregates the model was validated using data from wind tunnel experiments on the same but dry sediment and on data obtained from simulations with the model of chepil soil sci soc am proc 20 1956 288 the experiments showed that soil aggregates should be treated as individual particles with a density equal to their bulk density furthermore it was shown that the surface had to dry to a moisture content of about 75 of the moisture content at 1 5 mpa before deflation became sustained the threshold shear velocities simulated with our model were found to be in good agreement with own observations and with simulations using chepil s model

a general framework for modeling sediment supply to coastal dunes including wind angle beach geometry and fetch effects a series of spatially explicit equations are derived that form the foundation of a modeling framework that provides insight into how the interaction of the fetch effect and angle of wind approach leads to tradeoffs that govern the magnitude of aeolian sediment transport across beaches of different geometry the spatial distribution of sediment transport rate per unit width at any point on the beach is shown to vary predictably as a function of wind angle critical fetch and beach geometry and this has evident implications for the total volume and distribution of sediment transport into the dunes behind the beach as well as the proportion of sediment lost from the beach dune system at the downwind margin as the wind field shifts from onshore shore perpendicular to oblique shore parallel approach angle total sediment transport rate across a dune line segment will reflect a tradeoff between transport reduction because of the cosine effect and transport enhancement because of potentially longer fetch distances traversed by the wind prior to encountering the dune line this tradeoff is most evident on long narrow beaches when beach width is less than the critical fetch for such beaches and with onshore winds the total sediment transport rate across the dune line will be less than that predicted for a wide beach because of the constraint imposed by the fetch effect however as the angle of wind approach becomes oblique the available fetch becomes progressively longer transport limitations imposed by the fetch effect are negated and transport enhancement across the dune line is to be expected with very large angles of wind approach the cosine effect dominates the interaction and transport reductions across the dune line occur until the wind is shore parallel and sediment supply to the dunes ceases altogether this sequence of adjustments and tradeoffs were only partially understood prior to this study and yet they form the foundation of coastal dune modeling the framework proposed in this paper serves to place future studies of process form interaction in beach dune systems on a robust theoretical foundation it also facilitates the testing of various alternative hypotheses regarding the uneven spatial and temporal distribution of dune height and growth rate in coastal environments

geologic control in the nearshore shore oblique sandbars and shoreline erosional hotspots mid atlantic bight usa abstract beach and nearshore morphology defined primarily by slope and sandbar development is very dynamic and is largely controlled by waves currents and regional sediment characteristics results presented here challenge this long established concept and suggest that underlying framework geology may also exert a first order control on nearshore morphology by influencing the stability and or persistent re establishment of large scale sandbar morphology and position as well as surface sediment characteristics repeated sub bottom chirp and swath bathymetry surveys of the nearshore 2 10 m depths covering over 56 km of the north carolina outer banks and southeastern virginia indicate the following 1 development of shore oblique sandbars adjacent to large gravel outcrops that are surface exposures of the underlying geologic strata 2 identical re development or sustained maintenance of large scale sandbar morphology and position before and after very energetic conditions 3 vertical and horizontal heterogeneity of lithology and grain size and a minimum volume of sand ranging from 0 to 1 5 m thick and 4 close spatial alignment between the location of outcrops shore oblique bars and shoreline erosional hotspots a hypothesis is proposed from these findings that links framework geology to bar morphodynamics and sorted bedforms and ultimately erosional hotspots sediment transport and shoreline evolution models based solely on waves and currents and an assumption of unlimited and uniform sediment may be inadequate in similar heterogeneous sand limited regions

short communication multi scale topographic anisotropy patterns on a barrier island abstract barrier islands exhibit a range of landforms that reflect the complex and varied combination of coastal and aeolian processes realized over the evolution of the island a detailed analysis of the topography can be used to describe the evolution of a barrier island and provide insight on how it may be affected by a change in sea level storm activity and wind exposure patterns topographic anisotropy or the directional dependence of relief of landforms can be used to determine the relative importance of different processes to island evolution at a range of scales this short communication describes the use of scale dependent topographic anisotropy to characterize the structure of santa rosa island in northwest florida scale dependent topographic relief and asymmetry were assessed from a lidar derived dem from may 2004 a few months before the island experienced widespread erosion and overwash during hurricane ivan this application demonstrates how anisotropy can be used to identify unique scale dependent structures that can be used to interpret the evolution of this barrier island results of this preliminary study further highlight the potential of using topographic anisotropy to controls on barrier island response and recovery to storms as well as island resiliency with sea level rise and storm activity

an evolving research agenda for human coastal systems within the broad discourses of environmental change sustainability science and anthropogenic earth surface systems a focused body of work involves the coupled economic and physical dynamics of developed shorelines rapid rates of change in coastal environments from wetlands and deltas to inlets and dune systems help researchers recognize observe and investigate coupling in natural non human morphodynamics and biomorphodynamics this same intrinsic quality of fast paced change also makes developed coastal zones exemplars of observable coupling between physical processes and human activities in many coastal communities beach erosion is a natural hazard with economic costs that coastal management counters through a variety of mitigation strategies including beach replenishment groynes revetments and seawalls as cycles of erosion and mitigation iterate coastline change and economically driven interventions become mutually linked emergent dynamics of two way economic physical coupling is a recent research discovery having established a strong theoretical basis research into coupled human coastal systems has passed its early proof of concept phase this paper frames three major challenges that need resolving in order to advance theoretical and empirical treatments of human coastal systems 1 codifying salient individual and social behaviors of decision making in ways that capture societal actions across a range of scales thus engaging economics social science and policy disciplines 2 quantifying anthropogenic effects on alongshore and cross shore sediment pathways and long term landscape evolution in coastal zones through time including direct measurement of cumulative changes to sediment cells resulting from coastal development and management practices e g construction of buildings and artificial dunes bulldozer removal of overwash after major storms and 3 reciprocal knowledge and data exchange between researchers in coastal morphodynamics and practitioners of coastal management future research into human coastal systems can benefit from decades of interdisciplinary work on the complex dynamics of common pool resources from computational efficiency and new techniques in numerical modeling and from the growing catalog of high resolution geospatial data for natural and developed coastlines around the world

influence of inherited geologic framework on barrier shoreface morphology and dynamics abstract passive margin coastlines with limited sand supplies such as much of the u s atlantic margin are significantly influenced by the geologic framework of older stratigraphic units that occur beneath and seaward of the shoreface many u s east coast barrier islands are perched barriers in which the underlying pre modern sediments determine the morphology of the shoreface and strongly influence modern beach dynamics and composition perched barriers consist of varible layers of beach sand on top of older eroding stratigraphic units with highly variable compositions and geometries along many parts of the coastal system stratigraphically controlled bathymetric features on the inner shelf modify waves and currents and thereby effect patterns of sediment erosion transport and deposition on the adjacent shoreface it is essential to understand this geologic framework before attempting to model the large scale behavior of these types of coastal systems in north carolina most shoreline features are controlled by the pre holocene stratigraphic framework of the shoreface the beaches are perched on top of pre existing pleistocene tertiary and cretaceous sediments the surficial geology of the coastal zone is subdivided into two distinct provinces resulting in different stratigraphic controls of the shoreface north of cape lookout the geological framework consists of a quaternary sequence that fills a regional depositional basin called the albemarle embayment the coastal zone south of cape lookout is dominated by tertiary and cretaceous units that crop out across the coastal plain and continental shelf with very thin quaternary units only locally preserved superimposed upon this regional stratigraphy is an ancient drainage system resulting in a series of fluvial valleys filled with younger coastal sediments separated by large interfluve areas of older stratigraphic units this results in a coastal system in which the shoreface is either nonheadland or headland dominated respectively headland dominated shorefaces are further divided into subaerial and submarine categories nonheadland dominated shorefaces are further divided into those influenced primarily by transgressive or regressive processes or channel dominated depositional processes i e inlet migration or stream valley fill examples of each of these six types of shorefaces are presented to demonstrate the control that the geologic framework exhibits on shoreface morphologies and processes

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

deconstructing aeolian landscapes abstract semi stabilized dune systems are important indicators of quaternary drought variability across central north america the south texas sand sheet stss is the southernmost relict dune system on the great plains and is exposed to higher evapotranspiration and moisture variability than similar landscapes farther north in this study a combination of surface and sub surface remote sensing is used to analyze the semi stabilized dune landscapes of the stss in order to delineate distinct aeolian sediments that can represent generations of sedimentation or particular climate conditions the combination of multi resolution analysis of a lidar dataset electromagnetic conductivity surveys and xrf scans of soil cores are shown to be useful tools for deconstructing and modeling the environmental history of the stss optically stimulated luminescence osl dating of identified surfaces suggests that the stss is older than previously thought since dune systems are excellent repositories of climate and biophysical data for a landscape and are also sensitive to changes in climate and ecology the methodology employed in this study can be used to characterize the vulnerability of other similar environments to climate change through the holocene and over the next century

natural bathymetric change as a control on century scale shoreline behavior identification of the relevant forcing factors behind coastal change is a major societal demand in the face of rising sea level changes in the patterns of coastal erosion and accretion at a century scale in dundrum bay northern ireland are here attributed to natural changes in the nearshore bathymetry of sufficient magnitude to alter incident wave energy dispersal simulations of wave propagation across the nearshore reveal a marked change in the nearshore patterns of energy dispersal and related sediment transport pathways between 1861 and 1968 the 1861 bathymetry is associated with a simulated longshore drift divide in the middle of the bay and with sediment dispersal to the southeast and northeast whereas the 1968 bathymetry is associated with a consistent northeastward drift throughout the bay these changes are consistent with recorded shoreline changes sediment accumulation and foredune accretion in the northeast and northeastward spit elongation across a tidal inlet this study reveals a case in which purely natural changes in the seafloor at a century scale can be related to long term shoreline changes similar changes during relative sea level rise during the holocene were potentially capable of significant modification of shoreline morphology and dynamics near shore extraction of sand for beach nourishment purposes may have consequences of similar magnitude for adjacent beaches

linking framework geology and nearshore morphology correlation of paleo channels with shore oblique sandbars and gravel outcrops abstract this work describes a newly discovered spatial correlation between paleo channels and nearshore morphology along the barrier islands of northeastern north carolina and southeastern virginia u s mid atlantic coast these nearshore morphological features include regions of shore oblique sandbars and coincident gravel outcrops that previously have been linked to erosional hotspots at the shoreline these new findings have direct bearing on both nearshore morphodynamics and shoreline management paleo channels were identified in the chirp seismic record and compared to shore oblique sandbar locations discerned from bathymetric data and corroborated by gravel outcrops depicted in the side scan record both graphical correlation and statistical cross correlation analyses revealed a significant spatial relationship between these features with higher statistical correlation for channels 500 m wide seismic records also indicate that the gravel outcrops seen on the updrift flanks of the shore oblique bars are surface expressions of the underlying geology we hypothesize that these outcrops are composed of relict channel fill sediments that interact with the hydrodynamic regime to produce sorted bedforms the bathymetric anomalies then serve to alter incident wave energy and affect shoreline behavior the spatial and temporal stability of these features over several years and through a variety of wave conditions suggests some degree of underlying geologic control while the mechanisms responsible for this relationship remain speculative these results may bridge the gap between studies focusing on framework geology and its influence on shoreline change and those that investigate bar morphodynamics and the initiation of sorted bedforms

interdependence of geomorphic and ecologic resilience properties in a geographic context abstract ecology and geomorphology recognize the dynamic aspects of resistance and resilience however formal resilience theory in ecology has tended to deemphasize the geomorphic habitat template conversely landscape sensitivity and state and transition models in geomorphology downweight mechanisms of biotic adaptation operative in fluctuating spatially explicit environments adding to the interdisciplinary challenge of understanding complex biogeomorphic systems is that environmental heterogeneity and overlapping gradients of disturbance complicate inference of the geographic patterns of resistance and resilience we develop a conceptual model for comparing the resilience properties among barrier dunes the model illustrates how adaptive cycles and panarchies the formal building blocks of resilience recognized in ecology can be expressed as a set of hierarchically nested geomorphic and ecological metrics the variance structure of these data is proposed as a means to delineate different kinds and levels of resilience specifically it is the dimensionality of these data and how geomorphic and ecological variables load on the first and succeeding axes that facilitates the delineation of resistance and resilience the construction of dune topographic state space from observations among different barrier islands is proposed as a way to measure the interdependence of geomorphic and ecological resilience properties

multiple sediment sources and a cellular non integrated longshore drift system northwest florida and southeast alabama coast usa abstract the morphosedimentary maintenance of a 225 km stretch of coast along the northeast gulf of mexico from grayton beach florida to morgan point alabama has been interpreted previously within the framework of a unidirectional integrated monotonic longshore drift model with a single headland source of sediment located east of grayton beach net longshore transport and the granulometry and composition of some 2000 foredune beach and step samples indicate a cellular net drift system supplied by three independent sources of sediment one source is provided by the pleistocene barrier island complex along grayton mirimar beach the second at pensacola beach on santa rosa island and the third is onshore transport across the inner shelf between pensacola florida and morgan point alabama the pleistocene headland and pensacola beach supply two cells along santa rosa island whereas onshore transport from the low gradient inner shelf supplies sediment to three cells along the largely accretional beach ridge dominated coast from pensacola pass to morgan point drift cells along this coast experience negligible net sediment exchange these findings have significant implications for both the late holocene evolution and the morphodynamic maintenance of this coast

monitoring and comparison to predictive models of the perdido key beach nourishment project florida usa abstract this paper summarizes the results of over 8 years of data describing the performance of a large beach nourishment project on perdido key immediately adjacent to pensacola pass in escambia county fl usa as a result of a major excavation of the entrance channel to pensacola bay over 7 million m 3 of beach quality sand were placed along the easternmost 7 5 km of perdido key adjoining the entrance channel at pensacola pass the project included the placement of 4 1 million m 3 of sand directly upon the shoreline in 1989 1990 followed by the placement of an additional 3 million m 3 as an underwater berm just offshore of the beach nourishment project in water depths of roughly 6 m monitoring of the performance of the beach nourishment project and the offshore berm has been conducted since 1989 beginning with a pre construction survey of the project area monitoring surveys have been conducted on an annual or biennial basis since that time with the most recent survey occurring in july august 1998 over 8 years of monitoring data indicate that the beach nourishment project has retained approximately 56 of the original volume placed within the 7 5 km project length in addition according to the latest monitoring survey the dry beach width of the project initially constructed as 135 m on average is still 53 m wider than pre project conditions approximately 41 of the originally placed dry planform area remains as of july 1998 the most recent monitoring surveys in 1995 1997 and 1998 encompass the effects of two major storm systems hurricanes erin august 1995 and opal october 1995 monitoring of the offshore berm area indicates only a slight landward migration of the berm accompanied by a minor decrease in volume over the entire monitoring period the performance of both the beach nourishment project and the offshore berm appear to be significantly related to the two storm events particularly hurricane opal and the proximity of the project to the tidal entrance at pensacola pass comparison of the documented performance of the beach nourishment project to simple existing analytical models of beach fill evolution have yielded encouraging results in terms of preliminary design aids for future beach nourishment projects in the vicinity of deep tidal entrances

role of morphologic feedback in surf zone sandbar response several aspects of feedback mechanisms associated with surf zone sandbar response have been characterized using bathymetric surveys sampled approximately monthly over a 16 year period at the army corps of engineers field research facility north carolina the measured bathymetry was alongshore averaged and modeled by the superposition of two gaussian shaped sandbars on an underlying planar slope a third half gaussian shaped bar represented steepening at the shoreline the rms error between the measured bathymetry and the profile model was 0 10 m estimated over 322 different surveys the model explained 99 of the profile variance that remained after first removing the linear cross shore trend from each observed profile bar response which was extracted from the modeled profiles was compared to a local hydrodynamic forcing variable was defined as the ratio of the wave height to water depth evaluated at bar crest locations at low values of i e nonbreaking conditions bars migrated onshore and their amplitude tended to decay at high values of i e breaking conditions bars migrated offshore with relatively little change in amplitude the transition between onshore and offshore migration occurred at a value of that was consistent with the onset of wave breaking bar migration was associated with a stabilizing feedback mechanism which drove bar crests toward an equilibrium position at the wave breakpoint however we observed that the rate of bar response showed no reduction for any nonzero choice of indicating that bars never reached equilibrium systematic bar amplitude decay was observed under nonbreaking conditions bar amplitude decay could drive farther away from breaking conditions allowing further bar amplitude decay this is a destabilizing feedback mechanism potentially leading to bar destruction

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

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

particle transport and adjustments of the boundary layer over rough surfaces with an unrestricted upwind supply of sediment abstract most natural surfaces containing non erodible roughness elements are considerably more complex than those studied in modelling exercises and wind tunnel simulations unlike idealized roughness elements which are uniform in size shape i e spheres or cylinders and spacing natural elements are challenging to measure in 3 dimensional space similarly most deflation lag surfaces such those as found on sandar and beaches are spatially heterogeneous open systems in which sediment transport from an external supply is very likely the development of irregular deflation lag surfaces and the transport of sediment over these surfaces from an upwind source of sediment was studied in a series of wind tunnel simulations surfaces prepared with crushed gravel and natural beach shingle respond conservatively in terms of the adjustment to the deflation and deposition of sediment deflation lag surfaces prepared with no spacing between the roughness elements i e close packed demonstrate little to no change in coverage with the introduction of particles from an upwind source neither the element type nor the friction velocity affect this outcome as the center to center element spacing increases to 60 mm infilling of the lag surface eventually is observed with the element coverage reduced by a factor between 2 and 4 for a given threshold ratio r t the roughness density is smaller than observed in previous simulation studies based on idealized roughness elements

factors controlling the survival of coastal dunes during multiple hurricane impacts in 2004 and 2005 santa rosa barrier island florida abstract santa rosa island is an 85 km long wave dominated low lying barrier island situated along the northwestern florida coast facing the gulf of mexico the entire island was severely impacted by ivan a strong category 3 hurricane that made landfall about 45 km to the west in september of 2004 ten months later in july of 2005 dennis another category 3 hurricane made landfall about 30 km east of the western tip of the island santa rosa island is characterized by well developed but relatively low dunefields described in this paper as incipient and established dunes based on the presence of grassy and woody types of vegetation respectively the dunes were severely eroded by the two hurricanes this paper investigates the factors controlling the regional scale destruction and survival of the dunefields dune survival is controlled by 1 hurricane characteristics including intensity duration and frequency and 2 morphological parameters including width of the barrier island height and width of the dunefields vegetation type distance of the dunes to the ocean and continuity of the dunefields three processes of dune destruction are described including from most to least severe inundation overwash and scarping the interaction of all the above factors determines the different dune responses to the storm impacts in general the extensive and densely woody vegetated dunefields near the bay side shoreline survived the storms while the discontinuous dunes with grassy vegetation near the gulf shoreline were almost completely destroyed

wind blown sand on beaches an evaluation of models five models for predicting rates of aeolian sand transport were evaluated using empirical data obtained from field experiments conducted in april 1994 at a beach on inch spit co kerry republic of ireland measurements were made of vertical wind profiles to derive shear velocity estimates beach slope and rates of sand transport sediment samples were taken to assess characteristics of grain size and surface moisture content estimates of threshold shear velocity were derived using grain size data after parsing the field data on the basis of the quality of shear velocity estimation and the occurrence of blowing sand 51 data sets describing rates of sand transport and environmental conditions were retained mean grain diameter was 0 17 mm surface slopes ranged from 0 02 on the foreshore to about 0 11 near the dune toe mean shear velocities ranged from 0 23 m s 1 just above the observed transport threshold to 0 65 m s 1 rates of transport ranged from 0 02 kg m 1 h 1 to more than 80 kg m 1 h 1 these data were used as input to the models of bagnold bagnold r a 1936 the movement of desert sand proc r soc london a157 594 620 kawamura kawamura r 1951 study of sand movement by wind translated 1965 as university of california hydraulics engineering laboratory report hel 2 8 berkeley zingg zingg a w 1953 wind tunnel studies of the movement of sedimentary material proc 5th hydraulics conf bull 34 iowa city inst of hydraulics pp 111 135 kadib kadib a a 1965 a function for sand movement by wind university of california hydraulics engineering laboratory report hel 2 8 berkeley and lettau and lettau lettau k and lettau h 1977 experimental and micrometeorological field studies of dune migration in k lettau and h lettau eds exploring the world s driest climate university of wisconsin madison ies report 101 pp 110 147 correction factors to adjust predictions of the rate of transport to account for the effects of slope and moisture content were calculated using the models of bagnold bagnold r a 1973 the nature of saltation and bed load transport in water proc r soc london ser a 332 473 504 and belly belly p y 1964 sand movement by wind u s army corps eng cerc tech mem 1 washington d c 38 pp respectively none of the models was able to produce a strong correspondence between measured and predicted rates of transport best results were obtained using the bagnold and zingg models and the kadib model was the least viable of this group the influence of sediment moisture content appeared to be the critical factor in degrading model viability overall none of the models is adequate for general applications to coastal aeolian environments where moisture content complications tend to override the predictive competence of the simple transport formulations c 1998 elsevier science b v

an automated approach for extracting barrier island morphology from digital elevation models abstract the response and recovery of a barrier island to extreme storms depends on the elevation of the dune base and crest both of which can vary considerably alongshore and through time quantifying the response to and recovery from storms requires that we can first identify and differentiate the dune s from the beach and back barrier which in turn depends on accurate identification and delineation of the dune toe crest and heel the purpose of this paper is to introduce a multi scale automated approach for extracting beach dune dune toe dune crest and dune heel and barrier island morphology the automated approach introduced here extracts the shoreline and back barrier shoreline based on elevation thresholds and extracts the dune toe dune crest and dune heel based on the average relative relief rr across multiple spatial scales of analysis the multi scale automated rr approach to extracting dune toe dune crest and dune heel based upon relative relief is more objective than traditional approaches because every pixel is analyzed across multiple computational scales and the identification of features is based on the calculated rr values the rr approach out performed contemporary approaches and represents a fast objective means to define important beach and dune features for predicting barrier island response to storms the rr method also does not require that the dune toe crest or heel are spatially continuous which is important because dune morphology is likely naturally variable alongshore