hurricanes and climate in the caribbean during the past 3700 years bp a multiproxy analysis of lacustrine sediments cored in grand case pond at saint martin north of the lesser antilles archipelago reveals three distinct climatic periods for the last 3700 years from 3700 to 2500 yr cal bp and from 1150 yr cal bp to the present carbonate mud deposition occurred in connection with pond lowstands these periods were also punctuated by severe drought events marked by gypsum laminae and hurricane landfalls leading to marine sand inputs into the pond the intermediate time interval from 2500 to 1150 yr cal bp is typified by black organic mud deposition suggesting that hypoxic to anoxic conditions prevailed at the pond bottom these were probably linked with a perennial pond highstand and reflect more uniform and wetter climatic conditions than today the carbon isotopic composition of the ostracod perissocytheridea bisulcata shows that the lowest 13c values are recorded during the hypoxic periods as a consequence of bacterial recycling of isotopically depleted org

coarse clastic barrier environments evolution and implications for quaternary sea level interpretation abstract this paper reviews recent work particularly from eastern canada on the dynamics and evolution of coarse clastic barriers it is argued that an understanding of quaternary coastal changes on paraglacial glacially influenced coasts can only be achieved with a knowledge of gravel barrier morphodynamics and sedimentation gravel barriers are distinctive coastal forms in which morphological inheritance and sediment sorting provide major behavioral controls spatially adjacent gravel barriers may display different depositional tendencies prograde seawards migrate landward or aggrade vertically such inconsistent spatial behaviour must be considered in terms of an erosional front advancing landward under stationary or rising sea level redistribution of sediment across or along the erosional front supplies sediment for the development of gravel barriers which in turn provides environments for fine grained deposition which is favourable for further barrier migration an example of an erosional front is given from chezzetcook inlet nova scotia three stages are recognized in the development of gravel barriers starting with the initiation of small drift aligned forms at the leading edge of the erosional front as sea level rises this is followed by a period of consolidation and stabilization when drift aligned forms may become swash aligned conditions for this transition are discussed under rising sea levels it is difficult to explain the conditions leading to the formation of multiple parallel swash aligned ridges although three hypotheses are advanced all of which may operate in different locations the third stage is associated with the breakdown of barriers as sediment supply fails and or sea level rises drift aligned forms are inherently unstable and show signs of pre breakdown stress in the form of reworking and remobilization of proximal sediments into cells swash aligned barriers may be breached revert to drift alignment become segmented or be overstepped some gravel is re incoporated in barriers farther landward while other material is passed seaward of the erosional front and becomes abandoned on the shoreface gravel barriers may exert a major influence on estuary and back barrier environments especially where they control the depositional record the implications for the reconstruction and interpretation of quaternary environments are summarized

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

alexander the great s tombolos at tyre and alexandria eastern mediterranean tyre and alexandria s coastlines are today characterised by wave dominated tombolos peculiar sand isthmuses that link former islands to the adjacent continent paradoxically despite a long history of inquiry into spit and barrier formation understanding of the dynamics and sedimentary history of tombolos over the holocene timescale is poor at tyre and alexandria we demonstrate that these rare coastal features are the heritage of a long history of natural morphodynamic forcing and human impacts in 332 bc following a protracted seven month siege of the city alexander the great s engineers cleverly exploited a shallow sublittoral sand bank to seize the island fortress tyre s causeway served as a prototype for alexandria s heptastadium built a few months later we report stratigraphic and geomorphological data from the two sand spits proposing a chronostratigraphic model of tombolo evolution

geomorphic and temporal evolution of a mississippi delta flanking barrier island grand isle la abstract barrier islands throughout the world are increasingly stressed due to accelerating sea level rise slr increasing storminess and diminishing sediment supplies this condition is particularly evident along the louisiana coast because it has one of the highest rates of relative slr in the world and very limited sand sources one of the keys in predicting how barrier islands will change in the future is to understand how they have evolved since their formation historical shoreline changes are usually insufficient because those records only provide a glimpse of a barrier s history moreover the data needed to decipher barrier evolution at an intermediate scale 101 103 years is lacking for many coastal louisiana barrier systems one method for tracking barrier island development through time makes use of optically stimulated luminescence osl dating of beach ridge sediments this study combines osl and the analysis of aerial imagery and previous core logs to document the timing of beach ridge formation rates of progradation and geologic framework of the only developed barrier island in louisiana grand isle is composed of prograding beach ridges organized in distinct unconformable sets ridges increase in spacing from west to east due to increased rates of shoreline progradation caused by decreased accommodation space proto grand isle began forming approximately 750 years ago prograded northeastward until approximately 620 years ago when sediment supply slowed and or major storms impacted the island during that time much the seaward portion of the existing ridges were eroded following truncation of the first set of beach ridges group 1 the island once again began to prograde in a slightly more eastward direction group 2 ridge sets osl dates indicate the island s central ridges group 2 ridge sets 7 9 formed between 370 30 and 170 10 years ago at an average rate of one ridge every 14 8 years or progradation rate of 14 9 m yr the island s sediment source comes from an eroding beach ridge plain of the caminada headland to the west the volume of grand isle s barrier lithosome is 9 26 107 m3 which computes to an average northeasterly longshore transport rate of 128 625 m3 yr this is a high longshore transport rate for the relatively low wave energy of this coast hs 0 6 m but is explained by hurricane impacts that substantially increase average sand transport conditions the substantial thickness of the grand isle barrier lithosome 10 m and its steady supply of sediment contribute to the island s stability in contrast to other barrier systems along the louisiana coast

relationship between fluvial bounding surfaces and the permeability correlation structure results of three meter scale outcrop studies suggest a quantifiable relationship between fluvial bounding surfaces and the permeability correlation structure mapping of bounding surfaces and in situ measurements of permeability were obtained in three types of deposits a low energy channel deposit a paleosol and a high energy channel deposit for the low energy channel deposit only second order surfaces separating lithofacies were mapped the variogram exhibits anisotropic exponential behavior and an analysis of variance anova suggests that the within facies variation dominates over between facies variation the paleosol contained no internal bounding surfaces and exhibited a bellshaped variogram consistent with a smoothly varying style of heterogeneity both firstand second order bounding surfaces were mapped in the high energy channel deposit results of the anova suggest that the between facies variation dominates over the within facies variation a model of spatial correlation using superposition of independent processes acting over different scales provides a good fit to the data these three studies suggest that fluvial bounding surfaces provide a geological basis for conceptualizing and modeling heterogeneity in alluvial deposits

progradational gravel beach sequences in a moderate to high energy microtidal marine environment the anatomy of progradational gravel beaches was analysed in two different tectonic settings the strongly subsiding messinian foreland basin of the eastern southern alps and the rising pleistocene marine terraces of the outer margin of the apenninic chain progradation took place near the mouths of fan delta or braid delta distributaries debouching in microtidal landlocked basins palaeo adriatic and palaeo ionian seas a wind wave climate comparable to that of the present day was characterized by periodic intense storm activity most of the beachface progradation is thought to have taken place during the post storm recovery and fair weather stages whereas the impact of storms is mostly recorded by the cutting of erosional surfaces on the beachface and by emplacement of poorly sorted and coarse grained gravels on the shoreface by storm intensified seaward trending flows and behind the highest berms by washover processes analysis of the sequences led to the identification of a number of typical divisions which are differently developed in the two settings compared here the characteristics of the apenninic sequences suggest a strongly variable wind wave climate with periodic changes from a relatively dissipative barred morphology during storms accompanied by strong longshore currents and rip development to a more reflective state typical of recovery and fair weather stages the southern alpine sequences on the other hand are characterized by poor evidence of barred morphology and of longshore currents and widespread effects of shear and gravity sorting in the lower beachface gravels these features indicate a comparatively more reflective average state due to location of beaches along the deeply embayed head of the palaeo adriatic and the very narrow directional width of the incoming wave spectrum which was almost shore normal most of the time in addition to well developed shape zonation of gravels the common presence of wave generated gravel megaripples in the southern alpine sequences indicates the greater influence of long period waves due to the greater available fetch distances in both settings the cyclicity is thought to be genetically related to minor changes of sea level

sensitivity of post hurricane beach and dune recovery to event frequency the recovery of santa rosa island in northwest florida is characterized following hurricane katrina september 2005 which was preceded by hurricanes ivan 2004 and dennis 2005 beach and dune recovery were quantified to the east and west of pensacola beach through a comparison of lidar data collected immediately following hurricane katrina and in july 2006 after almost a year of recovery east of pensacola beach the santa rosa unit the shoreline retreated by an average of 64 m during the 2004 2005 hurricane season and recovered by an average of 19 m to the west of pensacola beach the fort pickens unit the shoreline retreated by an average of 30 m and while no significant shoreface recovery was observed the presence of vegetation on low profile dunes promoted backshore accretion it is found that beachface recovery in the santa rosa unit and backshore accretion in the fort pickens unit occurred at the widest sections of the island where the pre storm profile volume had been relatively large and overwash penetration was at a minimum the narrow sections of the island between cuspate headlands had a smaller profile volume before the storms leading to greater overwash penetration and in some cases island breaching in both sections which limited the volume of sediment available for shoreface recovery the alongshore variation in recovery is not only related to the island width but also the offshore bathymetry height of the pre storm dunes and the overwash penetration if sufficient time is allowed for the return of vegetation and the recovery of the dunes the variations in storm impact observed during hurricane ivan will be reinforced during subsequent storms in this respect the level of impact during subsequent storms and the ability of the island to recover will depend on the frequency of storm events copyright 2009 john wiley sons ltd

post storm beach and dune recovery implications for barrier island resilience abstract the ability of beaches and dunes to recover following an extreme storm is a primary control of barrier island response to sea level rise and changes in the frequency and or magnitude of storm surges whereas erosion of the beach and dune occurs over hours and days it can be years to decades before the beach and dune are able to recover to their pre storm state as a consequence there are numerous descriptions of near instantaneous beach and dune erosion due to storms the immediate onshore transport of sand and the initial phases of beach and dune recovery following a storm but a paucity of data on long term beach and dune recovery a combination of previously published data from galveston island texas and new remotely sensed data from santa rosa island florida is used in the present study to quantify the rate of dune recovery for dissipative and intermediate beach types respectively recovery of the dune height and volume on galveston island was observed within two years following hurricane alicia 1983 and was largely complete within six years of the storm despite extensive washover in contrast the dunes on santa rosa island in northwest florida began to recover four years after hurricane ivan 2004 and only after the profile approached its pre storm level and the rate of vegetation recovery regrowth was at a maximum results show that complete recovery of the largest dunes in height and volume will take approximately 10 years on santa rosa island which suggests that these sections of the island are particularly vulnerable to significant change in island morphology if there is also a change in the frequency and magnitude of storm events in contrast the areas of the island with the smallest dunes before hurricane ivan exhibited a rapid recovery but no further growth in profile volume and dune height beyond the pre storm volume and height despite continued recovery of the largest dunes to their pre storm height a change in storm magnitude and or frequency is a potential threat to barrier island resilience particularly for those sections of the island where dune recovery has historically taken the longest time further study is required to determine how and why dune recovery varies for the dissipative and intermediate beaches of galveston island and santa rosa island respectively

headlands and offshore islands as dominant controlling factors during late quaternary barrier formation in the forster tuncurry area new south wales australia abstract pleistocene and holocene barrier systems along the coast of southeast australia differ from those of the coastline of the eastern u s a and elsewhere there are no continuous barrier island chains along the coast of new south wales such chains developed only in eastern victoria in new south wales pleistocene and holocene barriers were built within rocky embayments along the coastline the forster tuncurry coastal zone of central new south wales is an excellent example of such embayment it is a mosaic of sedimentary environments that covers about 270 km 2 and includes late pleistocene bay barriers holocene beach ridges tide dominated channels mudflat islands peripheral tidal flats lake sediments and nine beaches of various types headlands and offshore islands played a dominant role in the sedimentary process marine sediment washed into the embayment by refracted waves formed the following type of bay barriers a bay barrier between mid bay headland and an offshore island b between two opposing mid bay headlands and c two barrier types between the outer headlands of the bay mouth and the large centrally located offshore island these barriers are seen as beach ridges in the northern half of the embayment and a lagoon barrier in the southern half the large centrally located cape hawke was an island and the most significant of these features dividing the bay into two compartments through time laterally accreting barriers were generated in the northern compartment and a lagoon barrier was created to the south

spatial and temporal variability of coastal storms in the north atlantic basin over the past three to four decades there has been a growing awareness of the important controls exerted by large scale meteorological events on coastal systems for example definitive links are being established between short term timescales of 5 10 years beach dynamics and storm frequency this paper assesses temporal variability of coastal storms both tropical and extratropical and the wave climatology in the north atlantic basin nab including the gulf of mexico with both storm types the empirical record shows decadal scale variability but neither demonstrates highly significant trends that can be linked conclusively to natural or anthropogenic factors tropical storm frequencies have declined over the past two or three decades which is perhaps related to recent intense and prolonged el ninos some forecasts predict higher frequencies of tropical storms like that experienced from the 1920s to the 1960s to occur in coming decades results from general circulation models gcms suggest that overall frequencies of tropical storms could decrease slightly but that there is potential for the generation of more intense hurricanes these data have important implications for the short term evolution of coastal systems there is strong suggestion that extratropical systems have declined overall over the past 50 100 years but that there is an increase in frequency of very powerful storms especially at higher latitudes both enso and the north atlantic oscillation nao are shown to have associations with frequencies and tracking of these systems these empirical results are in general agreement with gcm forecasts under global warming scenarios analyses of wave climatology in the nab show that the last two to three decades have been rougher at high latitudes than several decades prior but this more recent sea state is similar to conditions from about 100 years ago the recent roughness at sea seems to be related to high nao index values which are also expected to increase with global warming thus when coupled to an anticipated continued rise in global sea level this trend will likely result in increasing loss of sediment from the beach nearshore system resulting in widespread coastal erosion

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

response of a vulnerable barrier island to multi year storm impacts lidar data inferred morphodynamic changes on ship island mississippi usa barrier systems around the world are experiencing accelerated sea level rise reduced sediment supply and frequent hurricane impacts however detailed quantitative field based studies concerning the response to these external forcing mechanisms are scarce particularly on the scale of entire islands the mississippi alabama barrier island chain located along the u s gulf of mexico coastline has lost land on the order of hectares per year since records began in the 1840s putting mainland coastal communities and important ecosystems at risk here we present an analysis of light detection and ranging lidar digital elevation models revealing erosional depositional patterns and geomorphologic changes around the most vulnerable of these islands ship island four lidar datasets 2004 2007 2010 and 2012 capturing the complete topography of the island and some bathymetry in the inlet and surrounding shallows to depths of up to 8 m are used to investigate subaerial and subaqueous sediment volume changes between these years the impact of hurricane katrina which produced the highest storm surge ever recorded in the united states is captured in the 2004 2007 dataset during this time sediment comparable to 1 5 times the 2004 subaerial island volume was lost from the area included in the topographic bathymetric dataset only 1 5 of this volume was recovered to this area between 2007 and 2010 the island returned to a state of sediment loss between 2010 and 2012 albeit within the error bounds while the areal extent of the islands continued to increase this study examines the impact severe storm events can have on vulnerable barrier islands it highlights the importance of utilizing 3d datasets that include both topographic and bathymetric data for morphodynamic analyses of barrier island systems

delineation of arsenic contaminated zones in bengal delta india a geographic information system and fractal approach groundwater extracted from shallow aquifers in the bengal delta is contaminated with arsenic the fluviodeltaic process that creates aquifers ironically extends its role to also contaminating them with arsenic the arsenic distribution maps show a spatial association of arsenic contaminated wells with palaeo cut off abandoned channels weight on evidences analysis indicates that the zones of contamination occur around palaeo channels within a corridor of 500 700 m that contains most of the contaminated wells these corridors are interpreted to be the zone of channel shifting contaminated wells represent point fractal geometry that can be separated into isolated points and clusters clusters occur within the zone of channel shifting as obtained by weight on evidences analysis isolated points occur within floodplain or back swamp areas clusters and isolated point fractals are interpreted to reflect the process of arsenic release into groundwater the migration of biomass within the permeable sandy domain of channel deposits is proposed to be the predominant process in generating clusters the isolated points represent restricted biomass spreading in less permeable clay silt dominated floodplains

arsenic toxicity of groundwater in parts of the bengal basin in india and bangladesh the role of quaternary stratigraphy and holocene sea level fluctuation arsenic toxicity in groundwater in the ganges delta and some low lying areas in the bengal basin is confined to middle holocene sediments dissected terraces and highlands of pleistocene and early holocene deposits are free of such problems arsenic rich pyrite or other arsenic minerals are rare or absent in the affected sediments arsenic appears to occur adsorbed on iron hydroxide coated sand grains and clay minerals and is transported in soluble form and co precipitated with or is scavenged by fe iii and mn iv in the sediments it became preferentially entrapped in fine grained and organic rich sediments during mid holocene sea level rises in deltaic and some low lying areas of the bengal basin it was liberated subsequently under reducing conditions and mediated further by microbial action intensive extraction of groundwater for irrigation and application of phosphate fertilizer possibly triggered the recent release of arsenic to groundwater this practice has induced groundwater flow mobilizing phosphate derived from fertilizer as well as from decayed organic matter which has promoted the growth of sediment biota and aided the further release of arsenic however the environment is not sufficiently reducing to mobilize iron and arsenic in groundwater in the ganges floodplains upstream of rajmahal thus arsenic toxicity in the groundwater of the bengal basin is caused by its natural setting but also appears to be triggered by recent anthropogenic activities

exploring typhoon variability over the mid to late holocene evidence of extreme coastal flooding from kamikoshiki japan sediment cores from two coastal lakes located on the island of kamikoshiki in southwestern japan lake namakoike and lake kaiike provide evidence for the response of a backbarrier beach system to episodic coastal inundation over the last 6400 years sub bottom seismic surveys exhibit acoustically laminated parallel to subparallel seismic reflectors intermittently truncated by erosional unconformities sediment cores collected from targeted depocenters in both lakes contain finely laminated organic mud interbedded with coarse grained units with depths of coarse deposits concurrent with prominent seismic reflectors the timing of the youngest deposit at kamikoshiki correlates to the most recently documented breach in the barrier during a typhoon in 1951 ad assuming that this modern deposit provides an analog for identifying past events paleo typhoons may be reconstructed from layers exhibiting an increase in grain size a break in fine scale stratigraphy and elevated sr concentrations

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

measurements of morphodynamic and hydrodynamic overwash processes in a large scale wave flume overwash is an important process that controls short term barrier dynamics as well as long term barrier migration but this process is difficult to study in the field due to its rare occurrence and the challenging conditions under which it occurs this paper uses data collected during the bardex ii experiment in the delta flume the netherlands where a proto type barrier was subjected to a range of wave and water level conditions the objectives of this research are to 1 compare the morphologic response to overwash on a gravel barrier bardex 2008 experiment with that on a sandy barrier bardex ii 2 understand the influence of wave period on overwash characteristics and sediment transport and 3 improve current knowledge of overwash hydrodynamics the comparative analysis shows that barrier overwash can be affected by negative feedback that stabilises the barrier through barrier crest accretion on gravel barriers and by submerged bar development on sandy barriers an increase in the wave period induced a reduction in overwash frequency over the crest but no significant relation was found between wave peak period and overwash discharge nevertheless overall water discharge during an overwash episode significantly correlates with overall overwash sediment transport rate overwash flow depths during the experiment were relatively shallow and velocities were similar compared to those measured during previous studies and reported in the literature despite the controlled laboratory conditions collection of reliable and accurate measurements of overwash velocities remains challenging

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

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

ground penetrating radar study of north padre island implications for barrier island internal architecture model for growth of progradational microtidal barrier islands and gulf of mexico sea level cyclicity abstract padre island is the widest and longest barrier island in the world it is 200 km long up to 3 km wide and 10 15 m thick this 2 000 year old barrier island was formed predominantly from northward longshore drifted sediments from the rio grande river delta a 3 km long shore normal 50 mhz ground penetrating radar gpr profile was collected across padre island from the gulf of mexico to laguna madre at the northern end of the padre island national seashore a 1 km long shore parallel gpr profile was also collected and intersects the shore parallel profile approximately 1 km landward of the gulf of mexico vibracores taken along the shore normal profile at the beach foreshore in the center of the island at the lagoon margin and at a recent washover fan were used in conjunction with the description of a deep rotary core taken through the northern part of the island to constrain the gpr interpretations in the shore normal profile gpr reflectors indicate both seaward and landward dipping clinoforms as well as concave upward scour and fill features seaward dipping reflectors indicate approximately 2 km of progradation of the barrier island suggesting an average progradation rate of 1 m year landward dipping reflectors in the landward 1 km of the gpr profile indicate approximately 1 km of landward growth suggesting an average landward growth rate of 0 5 m year nested concave upward scour and fill features in the central part of the island are interpreted as tidal and washover channels 3 8 m deep in strike cross section these scours are channel form in outline and contain nearly horizontal to slightly inclined radar reflectors the presence of channel form scours supports the interpretation that landward growth was dominantly due to deposition by short lived tidal deltas and storm washovers even though there was periodic landward island growth north padre island has been progradational throughout its history due to a high sediment supply the understanding of the architecture and growth history of padre island provides much needed information about the internal geometry and the evolution of modern barrier island systems in addition systematic variations in scour depths across the island suggest that storm frequency and intensity varied during the island s history and provides a proxy for estimating sea level fluctuations

response and recovery of horn and petit bois islands mississippi usa to tropical cyclone impacts 2004 2016 abstract horn and petit bois islands are two of five mississippi ms barrier islands that provide physical protection from tropical cyclones threatening the ms gulf coast in addition to critical habitat for the northern gulf of mexico gom in september 2004 hurricane ivan removed a large volume of sediment from the eastern ends of horn and petit bois islands with its 1 to 2 m storm surge and 194 kph wind speeds then in august 2005 hurricane katrina severely impacted the two islands again with its 3 5 to 5 5 m storm surge on horn and petit bois islands and estimated maximum sustained wind speeds of 204 kph at landfall in southeast louisiana using topographic light detection and ranging lidar datasets from 2004 to 2016 spatial and temporal changes of the islands area sediment volumes and shorelines were measured to ascertain their geomorphic responses and recovery rates following the impacts of these devastating tropical cyclones during the 2004 05 hurricane seasons horn island lost 13 3 of its pre hurricane ivan land area lost 35 9 sediment volume and had a total average shoreline change rate of 10 m yr petit bois island also lost 13 3 of its pre ivan land area lost 27 sediment volume and had a shoreline change rate of 33 m yr between 2005 post katrina and 2016 horn island recouped 6 6 of its pre ivan land area and 4 3 sediment volume whereas petit bois island recovered 4 of its pre ivan land area and 22 9 sediment volume the overall averaged shoreline change rates between 2004 and 2016 were 2 m yr for horn island and 3 m yr for petit bois island these changes reflect that horn island is no longer stable as its sediment supply cannot keep pace with the current rate of sediment loss and that because petit bois island s narrow central shoreline is retreating at a rate of 10 m yr the island is at risk of breaching during the next storm highlighting complex island response the relationship between area and shoreline changes to that of volume changes was inconsistent

overwash processes along a gravel beach in south east ireland recent overwashing and to a more limited extent overtopping has occurred on a gravel dominated beach just west of carnsore point in south east ireland at relatively low points swash excursions have breached the duneline and extensive gravel fans have formed on landward facing slopes also at interbreach positions swash ramps have been built up in front of previously eroding dune cliffs allowing overtopping at heights of up to 5 m above mhwost spreading a veneer of sediment over the adjacent dune ridge in both cases events appear to be preceded by erosion and backbeach sand and gravel deposition stratigraphic textural and fabric analyses assist in identifying environmental conditions that prevailed during overwash throat and fan and overtopping ramp sedimentation

coastal barriers northern gulf last eustatic cycle genetic categories and development contrasts a review abstract a large body of chronologically well constrained and detailed quaternary data accumulated in the last decades from the coastal shelf region of the northern gulf of mexico consequently a preliminary synthesis of major aspects of the late quaternary barrier and mainland coastal development on the northern gulf of mexico is timely several major factors account for the striking differences between barrier size and development styles in the three northern gulf coast regions barriers are nearly continuous in the nw where they dominate by the greatest dimensions and continuity sand supply from shelf and mainland sources continued at variable rates throughout six stages of the last eustatic cycle lec differences in antecedent topography in fluvial runoff volumes and relative sea level rise including rapid overstepping flooding events were critical in the regional distinctions leaving fewer and smaller relict fluvial delta behind drowned shore and nearshore landforms on the shelf only two large fluvial systems impacted the ne the nw shelf and nearshore received abundant sediment supply from the mississippi and lesser streams indirectly by ravinement erosion of relict landforms and landward directed cross shelf sediment transfer sands originated mainly in relict deltas fluvial tidal channel and inlet fill as well as from submerged shore ridge remnants on the continental shelf shelf margin deltas represented major secondary sources barrier formation categories and their respective importance in specific areas represent critical aspects of coastal development the authorship of various formation concepts e g penck gilbert mcgee haage ganong and keilhack often is still miscredited or remains unrecognized in the literature recognition of the stratigraphic and sedimentological diagnostic characteristics of the basic genetic barrier categories plays a key role in testing the validity of barrier evolution models closely knit process form relationships prevail between hydrodynamic sea level change storm tidal current overwash sedimentary shoal and island aggradation rollover and eolian accumulation processes and the resulting landform morphology the most detailed accounts that deal with the development of the alabama louisiana and apalachicola barrier chains are particularly instructive almost all modern gulf barriers with identifiable genetic background formed by shoal aggradation between 5 5 and 2 0 ka during a marked deceleration in sea level rise concurrently a sizable mainland strand plain complex extended the ne coastal plain tide and storm driven sediment transport to the large mobile bay ebb delta the focal role of composite east dauphin island in establishing the ms la island chain and the island blocking role of mississippi delta advance were prime factors in a complex barrier history migration paradoxically may also occur by transgressive rollover concurrently with regressive landward progradation of island strand plains stream discharge and sand reworked from relict lithosomes on the shelf were insufficient in compensating for wave and tide related sediment loss gulf levels stayed below the present throughout the mid and late holocene

modes of cross shore sediment transport on the shoreface of the middle atlantic bight the mechanisms responsible for onshore and offshore sediment fluxes across the shoreface zone seaward of the surf zone were examined in a 3 year field study the study was conducted in the southern part of the middle atlantic bight in the depth region 7 17 m using instrumented tripods supporting electromagnetic current meters pressure sensors suspended sediment concentration sensors and sonar altimeters the observations embraced fairweather moderate energy swell dominated and storm conditions cross shore mean flows ranged from near zero during fairweather to 20 cm s 1 during the storm oscillatory flows were on the order of 10 cm s 1 during fairweather and 100 cm s 1 during the storm suspended sediment concentrations at about 10 cm above the bed were 5 kg m 3 during the storm three methods were applied to evaluate the relative importance of incident waves long period oscillations mean flows and gravity in effecting shoreward or seaward sediment flux 1 an energetics transport model was applied to instantaneous near bottom velocity data 2 higher moments of near bottom flows were estimated and compared and 3 suspended sediment fluxes were estimated directly from the instantaneous products of cross shore velocity and suspended sediment concentration the results show that measurable contributions were made by all four of the processes most significantly mean flows were seen to dominate and cause offshore fluxes during the storm and to contribute significantly to onshore and offshore flux during fairweather and moderate energy incident waves were in all cases the major source of bed shear stress but also caused shoreward as well as seaward net sediment advection low frequency effects involving wave groups and long period waves made secondary contributions to cross shore sediment flux contrary to expectations low frequency fluxes were just as often shoreward as seaward whereas cross correlations between suspended sediment concentration and the instantaneous near bottom current speed were high and in phase under storm conditions they were weak and out of phase during fairweather conditions this suggests that simple energetics models are probably inadequate for predicting fairweather transport of suspended sediment

storm driven cyclic beach morphodynamics of a mixed sand and gravel beach along the mid atlantic coast usa abstract the morphodynamics of a mixed sand and gravel beach in delaware were investigated based on 18 almost monthly beach profile surveys at 46 locations from 2009 to 2011 60 sediment cores and 550 surface sediment samples collected at various alongshore and cross shore transects three different atmospheric disturbances occurred within a 3 month window during the study period 1 a distal hurricane 2 an energetic winter storm and 3 nor ida a long lasting and extremely energetic event resulting from the collision of a hurricane and winter storm the storm induced beach changes and post storm recovery following each of the three storms are evaluated a distinctive beach cycle was identified consisting of a built up berm profile and depleted nearly planar storm profile the time scale of the beach cycle relates to the frequency and intensity of storm impact and duration of inter storm recovery instead of simple seasonality the initiation of post storm recovery occurs during the subsiding phase of the storm attributable to the reduction in wave height and steepness transitioning to accretionary swells the sediment characteristics of the storm deposit associated with nor ida demonstrated substantial cross shore variation ranging from sandy gravel and gravelly sand within the storm swash zone near the pre storm dune edge to well sorted medium to coarse sand seaward of the storm swash zone storm deposits along mixed sand and gravel beaches demonstrate a variety of sedimentological characteristics in addition the studied beaches lacked a sandbar under all wave conditions a new beach cycle model is proposed for the non barred mixed sand and gravel beach

hurricane signatures and landforms toward improved interpretations and global storm climate chronology abstract the correct understanding of the geological and geomorphic evolution of paralic basins and coastal barriers is a prerequisite for establishing holocene hurricane archives worldwide detection and documentation of hurricane signatures in coastal deposits are becoming instrumental in attempts to reconstruct mid and late holocene storm climate history subsurface exploration and field studies on the ne gulf coast and data gleaned from the literature suggest the need for a complex approach that provides well documented details of coastal landscape evolution until recently prehistoric hurricanes and their intensity levels have been automatically interpreted from the frequency and thickness of sand layers in muddy paralic deposits however in addition to wind velocity several hydro aerodynamic and other factors a wide range of stratigraphic conditions topographic setting and sand sources also determine variations in the extent and intensity of storm flooding erosion transfer and deposition of sand layers in small paralic basins inherent limitations in these sedimentary records and their interpretation must be overcome in order to improve local hurricane chronologies and establish interregional correlations before sedimentary and chemical signatures are accepted as diagnostic indicators of overwash especially by catastrophic hurricanes alternative causes must also be considered a parallel scale of storm flood level stages should supplement the saffir simpson hurricane categories the relationship between storm intensities and flooding elevations is highly complex changes in sea level shore positions formation and extinction of preexisting incised valley networks the impact of transgression and regression processes on estuaries and their deposits play determining roles in setting the stage for overwash processes strandplain progradation followed by erosive shore retreat played a key role in framing certain paralic lakes without overwash sand layers and marine microfossils may be also emplaced by storm driven currents that enter unobstructed estuaries inlets and storm breaches bioturbation also distorts the storm record significant lateral variations in the number and thickness of intercalated sand layers at closely adjacent sites suggest the importance of local differences in sources transport and preservation processes in the dimensions relative positions and accessibility of sand resources inside and adjacent to coastal basins variations in the number thickness and ages of sand laminae may not be related to the number of storms and their intensities this may impair correlations between regionally interpreted calm and intensive phases in partial overlap with an assumed quiescent storm phase stable isotope ratios in lacustrine muds impacted by salt water influx reveal frequent hurricane activity during the last 1 5 ka as well by mimicking effects of reduced storminess the fewer and thinner sand laminae deposited between 7 0 and 3 4 ka b p may be attributed to greater distances of estuarine landward transport by storm tidal currents at times of lower sea levels

barrier and lagoon coast evolution under differing relative sea level regimes examples from ireland and nova scotia abstract although the coasts of southern ireland and eastern nova scotia possess many basic similarities especially in terms of geology glacial history sediment character resistance to erosion and wave and tide regimes there is a fundamental contrast in holocene sea level history in ireland recent the past 4000 years sea level rise has been limited to less than 1 mm year by contrast the atlantic coast of nova scotia has been experiencing sea level rises up to three to five times greater over the same period under these markedly differing relative sea level rise regimes barrier and lagoon evolution has varied considerably in ireland barrier lagoon form is controlled by local basement expression particularly through the emergence of headlands creating largely closed sediment systems and the requirement to maintain cross shore drainage it is this latter factor that leads to a simple four fold categorization of the irish barriers and lagoons from freshwater seepage to open tidal environments the nova scotian examples are associated with rapidly moving erosional fronts with local basement control relegated to a subordinate role at the expense of rapid changes in sediment supply barriers can both grow and decay under these conditions subject to certain critical but as yet ill defined thresholds simultaneously forcing development and destruction of adjoining lagoons these major differences also find expression in sedimentary sequences

sea level changes in the holocene over the last 30 years the emphasis in studies of the recovery from low last glaciation sea levels has changed significantly the search for a eustatic sea level curve having global relevance has ended studies into the rheology of the earth s crust and recognition that the geoid has not remained stable over time have resulted in the recognition that there must have been regional differences in eustatic response to deglaciation as a part of this re appraisal there has been a growing appreciation that crustal isostatic response to the removal of the weight of ice sheets has been accompanied by a consequential hydro isostatic response particularly in the areas of the shelf seas in the later part of the post war period attention has additionally been focussed on the much greater potential for error over the whole field of palaeoenvironmental reconstruction in the holocene including not only errors in dating but also a large number of possible sources of errors in heighting as a result of this an increasing number of scientists are withholding judgement on the nature of sea level rise and more particularly on the problem of higher than present late holocene eustatic sea levels the problems outstanding in the early 1960s have not yet been resolved but the bases of uncertainty have changed

morphosedimentary development of drumlin flank barriers with rapidly rising sea level story head nova scotia abstract the morphodynamic and morphosedimentary development of drift aligned and swash aligned coarse clastic barriers plays an important role in the evolution of paraglacial coasts this paper discusses the development of two contrasting barriers attached to a drumlin headland at story head on the atlantic coast of nova scotia southeastern canada a 3 4 mm a 1 sea level rise is forcing rapid barrier changes including landward migration rollover of the swash aligned barrier at 5 8 m a 1 and barrier thinning elongation and breaching morphological development reflects the highly variable longshore distribution of wave power imposed initially by the topography of the drumlin and its position in the incident wave field and later by morphosedimentary feedback resulting from such gradients gradual reduction of an inherently intermittent sediment supply leads to reworking cannibalization of the barrier ultimately finding expression in a series of distinct wave formed sediment cells further diminution of the sediment supply coupled to cell development results in the drift aligned system decaying into a series of high water residuals separated by breach depressions with splayed spit recurves at the margins although the swash aligned barrier is stretched within the predominant overwash regime and may eventually separate from the headland it has remained intact until very recently when an initial breach occurred the evolutionary sequence of the headland barrier system has an important effect on adjacent sedimentary environments

refining the link between the holocene development of the mississippi river delta and the geologic evolution of cat island ms implications for delta associated barrier islands abstract the geologic evolution of barrier islands is profoundly influenced by the nature of the deposits underlying them many researchers have speculated on the origin and evolution of cat island in mississippi but uncertainty remains about whether or not the island is underlain completely or in part by deposits associated with the past growth of the mississippi river delta in part this is due to a lack of comprehensive geological information offshore of the island that could augment previous stratigraphic interpretations based on terrestrial borings an extensive survey of cat island and its surrounding waters was conducted including shallow water geophysics e g high resolution chirp seismic side scan sonar and swath and single beam bathymetry and both terrestrial and marine vibracoring high resolution seismic data and vibracores from south and east of the island show two horizontally laminated silt units marine radiocarbon dates indicate that they are st bernard delta complex sbdc deposits furthermore seismic data reveal that the sbdc deposits taper off toward the southern shoreline of cat island and to the west morphology consistent with the distal edge of a delta complex the sedimentology and extent of each unit suggest that the lower unit may have been deposited during an earlier period of continuous river flow while the upper unit may represent reduced or sporadic river flow osl dates from the island platform beneath beach ridge complexes indicate three stages of terrestrial evolution island emergence resulting from relative sea level rise 5400 ybp island aggradation via littoral transport 2500 4000 ybp and island degradation due to delta mediated changes in wave direction present 3600 ybp finally the combination of terrestrial and marine data shows that portions of cat island that are lower in elevation than the central part of the island are younger and are likely underlain by a thin layer of deltaic sediments this underscores the potential for increased future vulnerability of barrier islands that develop adjacent to major river delta complexes

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

mechanisms to account for the longshore spacing of overwash throats on a coarse clastic barrier in southeast ireland abstract the longshore spacing of overwash throats on two contrasting sections of a coarse clastic reflective barrier beach in southeast ireland is examined for evidence of spatial periodicity a fixed barrier section carnsore with an irregular barrier top dune field exhibits random longshore throat positions related to pre existing irregularities in the seaward dune boundary a free barrier section tacumshin without a barrier top dune field shows regular longshore throat positions with a peak throat to throat periodicity of between 30 40 m similar longshore periodicity is found in persistent high level beach cusps above mhws though not always spatially in phase there is no consistent near shore rhythmic morphology that can account for this spacing the storm event which generated the tacumshin overwash appears to have dominant longer incident wave periods than normal in celtic sea storms on weight of circumstantial evidence it is reasoned that this dominant wave period range 9 11 s can be related to a zero mode sub harmonic edge wave whose longshore wavelength matches the peak periodicity of overwash spacing overwash sites on this reflective barrier may be determined by an edge wave controlled extension of run up which generates high level cusps and thereby creates washover routeways the presence or absence of a barrier top dune field is a secondary control on whether washover is successful in reaching the back barrier usually only where surge penetration and pre existing dune irregularities coincide does washover occur

storm induced damages along the catalan coast nw mediterranean during the period 1958 2008 abstract the temporal and spatial patterns of storm induced damage along the catalan coast nw mediterranean during the last 50 years have been analyzed to identify main climatic and non climatic forcings in the absence of systematic data a storm induced damage database compiled from press news has been built which together with an intensity scale has allowed us to characterize the frequency and intensity of damage although no temporal trend has been detected in storm induced hazards coastal damage has increased at a rate of about 40 per decade during the last 50 years along the catalan coast the main non climatic factors identified controlling this trend were the urban growth along the coastal fringe and the generalized erosive behavior of beaches the first one increased values at risk and the second one increased their exposure to storm induced hazards in spite of the importance of non climatic factors to modulate coastal damage an exponential dependence of damages on storm induced inundation and erosion was detected in addition to this storm induced geomorphic changes along the ebro delta coast have also been analyzed during the period analyzed harmful storms seem to be clustered with most of the events being present in the late 1990s and especially from 2001 to 2004 resulting in frequent events of intense beach barrier breaching massive overwash and flooding they are mainly expressed in sensitive areas which are subject to long term erosional processes and comprise a low lying profile and a narrow beach this reflects the role of coastal morphology in controlling the intensity of storm induced hazards along the deltaic coast shoreline evolution rates calculated during this period were significantly larger than the previously recorded ones reflecting a pulsating erosion behavior where large pulses occur during stormy periods and are reduced during post storm periods under the present scenario of maximum coastal development storm induced damage has been reported almost every year which could indicate that the present overall beach configuration status along the catalan coast has reached its limit for protecting the hinterland against storms

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

geochemical study of arsenic release mechanisms in the bengal basin groundwater 1 to investigate arsenic mobility in the bengal basin groundwater we sampled water wells and sediments throughout the region there are strong correlations among high levels of dissolved arsenic and iron ammonia and methane especially in samples from a single site laxmipur no linkage is seen between as and agricultural tracers such as phosphate the association of as and fe occurs because arsenic strongly adsorbs onto feooh particles in river water they flocculate with other fine grained particles at the freshwater saltwater transition zone subsequent bacterially mediated reduction of feooh in the clay releases the adsorbed arsenic weathering of as bearing mica plays a significant role in the as budget the correlated presence of as ch4 and nh4 in water supply wells is the result of diffusion out of organic rich clay into the more permeable zones arsenic is mainly released from recent sediments at 50 m depth deposited in the gbr floodplain as sea level rose throughout the holocene

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

nature and origin of arsenic carriers in shallow aquifer sediments of bengal delta india sediments from shallow aquifers in bengal delta india have been found to contain arsenic rivers of ganga brahmaputra system responsible for depositing these sediments in the delta have created a store of arsenic geomorphological domains with different depositional styles regulate the pattern of distribution of zones with widely different content of groundwater arsenic the high arsenic zones occur as narrow sinuous strips confined to channel deposits a few iron bearing clastic minerals and two post depositional secondary products are arsenic carriers secondary siderite concretions have grown on the surface of the clastic carriers in variable intensity the quantity of arsenic in all clastic carriers is in excess of what is generally expected excess arsenic is contributed by the element adsorbed on the concretion grown on the surface of the carriers which adds up to the arsenic in the structure of the minerals variable abundance of concretions is responsible for the variable quantity of arsenic in the carriers and the sediment samples fe2 for the growth of siderite concretions is obtained from the iron bearing clastic carriers the reaction involves reduction of trivalent iron to bivalent and the required electron is obtained by transformation of as3 to as5 it is suggested that oxidation of as3 to as5 is microbially mediated in the safe zone arsenic is retained in the carriers and groundwater arsenic is maintained below 0 05 mg l in the unsafe zone sorbed arsenic is released from the carriers in the water through desorption and dissolution of concretion thereby elevating the groundwater arsenic level to above 0 05 mg l

600 year sedimentary archive of hurricane strikes in a prograding beach ridge plain southwestern louisiana abstract this study tests a novel approach to paleotempestology substituting the lateral time depth of a prograding beach ridge plain for the vertical time depth of an aggrading coastal lake pond lagoon swamp or marsh trenching and coring of a beach ridge plain in southwestern louisiana revealed six sand beds and one shell bed interpreted as hurricane washover deposits the sand beds are readily distinguished from enclosing marsh sediments by their higher sand content lower organic content and contrasting microfossil assemblages based on the modern analogs of hurricanes audrey 1957 rita 2005 and ike 2008 and consideration of nearby landfalling hurricanes in the historical record it was determined that the storm intensity threshold of the study site is equivalent to a category 3 hurricane there is a wide variation in hurricane strike frequency between this site and other sites bordering the gulf of mexico this variation results from differences in site sensitivity and the nature of geologic or geochemical proxies used to derive hurricane strike records the approach demonstrated by this study could have applicability at other sites around the world where beach ridge plains are subject to tropical cyclone strikes

particle size and shape in pebble beach sedimentation an in depth investigation was made of beach gravel fabrics at two beach sites located on the glamorgan heritage coast wales u k granulometric data from 31 080 pebbles were obtained and analysis confirmed the existence of a basic shape differentiation structure when the b axis was used at gileston beach a low energy location and nash beach a high energy location the use of the b axis in size and shape analysis seems to have led some workers to incorrect rejection of size as a factor in determining the transportational and depositional potential of a particle an inferred energy model can be constructed where the influence of particle size on sorting is predominant when energy conditions are high and particle shape factors predominate when energy conditions are low the c axis standard deviation value was the most effective discriminator of variation in shore parallel sedimentation structures at both beaches for shore normal structural discrimination the c axis mean and standard deviation values were the most effective

detailed investigation of overwash on a gravel barrier abstract this paper uses results obtained from a prototype scale experiment barrier dynamics experiment bardex undertaken in the delta flume the netherlands to investigate overwash hydraulics and morphodynamics of a prototype gravel barrier gravel barrier behaviour depends upon a number of factors including sediment properties porosity permeability grain size and wave climate since overwash processes are known to control short term gravel barrier dynamics and long term barrier migration a detailed quantification of overwash flow properties and induced bed changes is crucial overwash hydrodynamics of the prototype gravel barrier focused on the flow velocity depth and discharge over the barrier crest and the overwash flow progression across and the infiltration through the barrier during the bardex experiment overwash peak depth 0 77 m velocity 5 m s 1 and discharge max 6 m 3 m 1 were high especially considering the relatively modest wave energy significant wave height 0 8 m conversely to schemes found in the literature average flow depth did not linearly decrease across the barrier rather it was characterised by a sudden decrease at the crest a milder decrease at the barrier top and then propagation as a shallow water lens over the backbarrier the barrier morphological evolution was analysed over a series of 15 min experimental runs and at the timescale of individual overwash events overall the morphological variation did not result from an accumulation of many small consistently erosive or accretionary events but rather the mean bed elevation change per event was quite large 10 mm and the overall morphology change occurred due to a small imbalance in the number of erosive and accretionary events at each location two relationships between overwash hydrodynamic variables were deduced from results 1 between overwash flow depth and velocity a power type relation was obtained and 2 a linear relation was observed between overwash flow depth and maximum overwash intrusion distance across the barrier top i e overwash intrusion findings from this study are useful to enhance the knowledge of overwash processes and also have practical applications on the one hand results shown here can be use for the validation of overwash predictive models and additionally the simple empirical relations deduced from the dataset can be used by coastal managers to estimate overwash intrusion distance which in turn can assist in the location of areas under risk of overwash and breaching

morphology and stratigraphy of small barrier lagoon systems in maine abstract the coast of maine contains over 200 individual barrier lagoon systems most quite small with an aggregate length of nearly 100 km although they represent less than 5 of the tidally influenced coastline of maine they are widely distributed and occur in a variety of dynamic regimes and physiographic regions their morphology and backbarrier stratigraphy are different from better studied coastal plain systems and provide important clues to the holocene evolution of the maine coast in a study of geomorphic form and backbarrier stratigraphy inlet processes and holocene sea level rise have been identified as the principal controls on coarse grained barrier stratigraphy barriers in maine are found in five distinct geomorphic forms identified herein as barrier spits pocket barriers double tombolos cuspate barriers and looped barriers the few long sandy beaches in southwestern maine are mostly barrier spits the remainder of the barrier types is composed primarily of gravel or mixed sand and gravel the barriers protect a variety of backbarrier environments fresh and brackish ponds lagoons and fresh and saltwater marshes the barriers may or may not have inlets normal wave action coarse grain size and a deeply embayed coast result in barriers with steep reflective profiles several meters above mhw occasional storm events completely wash over the barriers building steep lobate gravel fans along their landward margin few if any extensive storm layers are recognized as extending into the distal backbarrier environments however during sea level rise and landward barrier retreat this abrupt storm generated transition zone inters the backbarrier sediments statistical comparisons of barrier morphology location and backbarrier environment type with backbarrier stratigraphy show that holocene backbarrier stratigraphy is best predicted by the modern backbarrier environment type this in turn is influenced most by the absence or presence and long term stability or instability of a tidal inlet geomorphic barrier form and location in coastal geomorphic compartments show little or no correlation with backbarrier stratigraphy in contrast to previous classifications of barrier lagoon systems based primarily on sandy coastal plain examples in maine the shape or origin of the backbarrier system is relatively unimportant the presence or absence of a tidal inlet is of paramount importance in shaping the holocene stratigraphy of the backbarrier region

characterizing storm response and recovery using the beach change envelope fire island new york abstract hurricane sandy at fire island new york presented unique challenges in the quantification of storm impacts using traditional metrics of coastal change wherein measured changes shoreline dune crest and volume change did not fully reflect the substantial changes in sediment redistribution following the storm we used a time series of beach profile data at fire island new york to define a new contour based morphologic change metric the beach change envelope bce the bce quantifies changes to the upper portion of the beach likely to sustain measurable impacts from storm waves and capture a variety of storm and post storm beach states we evaluated the ability of the bce to characterize cycles of beach change by relating it to a conceptual beach recovery regime and demonstrated that bce width and bce height from the profile time series correlate well with established stages of recovery we also investigated additional applications of this metric to capture impacts from storms and human modification by applying it to several post storm historical datasets in which impacts varied considerably nor ida 2009 hurricane irene 2011 hurricane sandy 2012 and a 2009 community replenishment in each case the bce captured distinctive upper beach morphologic change characteristic of these different beach building and erosional events analysis of the beach state at multiple profile locations showed spatial trends in recovery consistent with recent morphologic island evolution which other studies have linked with sediment availability and the geologic framework ultimately we demonstrate a new way of more effectively characterizing beach response and recovery cycles to evaluate change along sandy coasts

crestal overtop and washover sedimentation on a fringing sandy gravel barrier coast carnsore point southeast ireland abstract storm sedimentation on a fringing sandy gravel barrier system in southeast ireland is examined recent wave overtopping and overwashing during severe onshore storms have resulted in a distinctive pattern of crest and backbarrier sedimentation this is not easily matched with available models of washover sedimentation drawn from the barrier islands of the eastern united states beach crest overtopping occurs at heights up to 6 m mhws and is related to the development of upper beach swash ramps that are plastered against storm wave eroded dune scarps located at the barrier crest ramp sediments comprise coarse basal beach gravels overlain by coarsening upward units and finally topped by distinctive seawarddipping fine grit coarse sand couplets in places where ramps reach the dune cre t overtopping swash has deposited a fine marine gravel veneer

short term morphodynamics of non storm overwash abstract overwash is an important process in barrier island evolution and its effects on the barrier morphology and sedimentology have been widely studied however the short term sediment dynamics of overwash processes are not well known due to the lack of specific field studies this paper presents field data that clarify the sedimentary dynamics of overwash processes on different washover morphologies and determine the factors leading to non storm overwash occurrence two fieldwork campaigns were undertaken during overwash events go 1 winter of 2001 and go 3 winter of 2003 on western barreta island algarve portugal the fieldwork included measurements of oceanographic conditions overwash flows morphology variations mixing depth and sediment transport paths using tracers the sediment dynamics induced by overwash varied according to the washover morphology washover plain versus washover lobe the sediment transport inside the washover plain was different for the two fieldwork campaigns average mixing depth of 13 cm for go 1 and 6 cm for go 3 however it had similar main stages stage 1 crest accretion stage 2 onshore transport and stage 3 dynamic equilibrium the sediment transport inside the washover lobe can be characterised by one onshore flow stage with erosion of the mouth and channel and accretion on the washover fan the main factors governing the occurrence of non storm overwash in the study area were the combined occurrence of 1 typical winter waves 2 spring high tides 3 washover crest below the high tide level 2 m and 4 absence of prominent beach berm this study proved that when the proper conditions are generated non storm overwash has sediment transport comparable to storm overwash and therefore may be significant for barrier evolution further field studies of overwash are needed principally for more detailed overwash flow velocity measurements high frequency morphologic surveys and barrier groundwater measurements

barrier island evolution middle atlantic shelf u s a part i shoreface dynamics abstract in part i of this paper near bottom fluid velocity and sediment concentration measurements from the shoreface of a middle atlantic barrier long island coast are analyzed to provide insight into the dynamics of erosional shoreface retreat in part ii these data are combined with observations of coastal stratigraphy in order to construct a model for the evolution and behavior of middle atlantic barriers wave motions on the long island shoreface tend to drive sediment onshore calculations of the onshore sediment flux driven by asymmetrical shoaling waves show that for the wave states commonly encountered on the middle atlantic shelf values become strongly positive landward of approximately 10 m water depth upper shoreface but drop to very low values shortly seaward of that isobath on the lower shoreface and inner shelf floor fair weather wave current interaction tends to cause a landward creep of sediment even though the wave orbital component of the near bottom velocity field is nearly symmetrical this movement occurs because the wave approach direction generally lies within 90 of the direction up coast or down coast of the alongshore wind driven current therefore fluid shear stress acting on the sediments tends to be reinforced during the shoreward stroke of the wave orbital motion and partially cancelled during the seaward stroke during major storms the rate of sediment transport increases by at least an order of magnitude and the role of wind driven currents becomes important much more sediment is resuspended by the wave orbital current component because storm waves are more powerful than fair weather swells but the wind driven flow component is also much stronger and is now available for transporting the resuspended sediment storm flows over the shoreface occur in distinct dynamic zones surf zone friction dominated zone transition zone geostrophic zone the zones are defined by dynamical considerations and expand or contract with the intensity of the causative wind stress during peak flow events the characteristic length scales of the friction dominated and geostrophic zones tend to correspond with the morphologic zones of the shoreface and inner shelf the storm intensified wind driven alongshore flows of the lower shoreface are frequently jet like in nature and may be upwelling or downwelling wind driven coastal flows with a strong downwelling component occur during most storms on the long island coast and are particularly important to the coastal sand budget during these events sand is entrained by the storm intensified upper shoreface circulation system of wave driven alongshore currents and rip currents and is fed into the main wind driven coastal current because of the offshore component of bottom flow sand is swept down the lower shoreface and onto the adjacent inner shelf fair weather processes may be unable to return storm deposited sand to the beach from such an offshore position the shoreface transport regime of the long island barrier coast thus consists of long periods of time months during which sand moves slowly toward the beach punctuated by short intense periods hours or days during which sand is transferred from the shoreface to the adjacent inner shelf the long term sense of movement of the shoreface whether retreating the long island case or prograding must depend on the loss or gain of sand by shoreface with respect to the inner shelf the data shows that the coastal sand budget is controlled not only by the upper shoreface cycle withdrawl of sand from the beach prism storage in the breakpoint bar and its subsequent return to the beach but by a cycle of larger spatial and temporal scale in which sand is exchanged between the shoreface as a whole and the adjacent inner shelf

response of wave dominated and mixed energy barriers to storms wave dominated and mixed energy barriers are extremely dynamic landforms responding to processes operating over a spectrum of time scales ranging from daily to monthly fluctuations related to storm and post storm conditions to century to millennium scale evolution driven by relative sea level change two types of storms are of particular relevance warm core tropical and cold core extratropical cyclones both are responsible for generating very large waves highly energetic surf zone dynamics and sediment transport elevated inshore water levels and extensive morphological responses all cyclones are affected by climate change which governs their frequency intensity and tracks barrier storm response is primarily governed by maximum storm runup and barrier morphology as conceptualised in abby sallenger s storm impact scale model sallenger 2000 this model defines four storm impact regimes and includes erosive as well as accretionary responses on the erosion side the swash regime drives bar and berm flattening the collision regime is marked by dune scarping and beach lowe the overwash regime leads to dune scouring and channel incision and the inundation regime may result in barrier destruction on the deposition side storm berms and beach ridges may form and accrete in the swash and collision regimes localised vertical beach and barrier accretion are associated with the collision and overwash regimes and washover deposition takes place in the overwash and inundation regimes site specific factors play a key role in moderating the morphological response and include storm characteristics type duration and track longshore sediment supply upwelling downwelling currents coastal setting and inner shelf topography the response of a barrier to a tropical or extratropical cyclone can however not be considered in isolation and has to be appreciated in a longer temporal context involving morphological preconditioning due to antecedent wave and water level conditions additionally a simple process response approach of the cause and effect type is inappropriate and a more complex conceptual framework involving thresholds feedbacks resilience and vulnerability will need to be adopted a useful way to visualise and conceptualise more complex storm behaviours and the longer term vulnerability of barriers is the resilience trajectory which maps out the changes in barrier geometry elevation and width over various time scales from weeks to years or even longer and under varying forcing conditions including changes in storminess and sea level rise an increased understanding of barrier response to storms and sequences of storms is required to better quantify long term barrier response to climate change high resolution and comprehensive decadal records of barrier response to storms are a prerequisite to achieve this ambition linking site specific coastal settings hydrodynamic drivers and morphological responses and allowing the recognition of recovery and impact dominated phases the enhanced insights in barrier response to extreme events must then be incorporated into improved coastal response models to help predict the impacts of future climate change on wave dominated and mixed energy barriers around the world 2013 elsevier b v

geomorphic response type model for barrier coastlines a regional perspective based on quantitative documentation of historical changes in shoreline position between 1847 and 1991 eight geomorphic response types were established for classifying megascale changes along barrier coastlines 1 lateral movement 2 advance 3 dynamic equilibrium 4 retreat 5 in place narrowing 6 landward rollover 7 breakup and 8 rotational instability long term decades to centuries monitoring of shoreline position over a spatial scale of 10 to 100 km provides a scientific basis for documenting process response relationships that shape regional coastal morphodynamics although megascale shoreline change studies often are lacking this type of information is critical for developing realistic research and management strategies regarding form process relationships in coastal depositional systems the spatial distribution of geomorphic response types is delineated along the barrier coastlines of louisiana mississippi and southern georgia northern florida at megascale the rate of relative sea level rise along these barrier coastlines appears to be one of the major factors controlling the occurrence of geomorphic response types however sediment supply exerts significant influence on shoreline response as well

transition of a regressive to a transgressive barrier island due to back barrier erosion increased storminess and low sediment supply bogue banks north carolina usa abstract although back barrier erosion is a prevalent process of island narrowing it is often overlooked in conceptual models of barrier island evolution in many wave dominated barrier island settings the absence of overwash precludes landward movement of the back barrier shoreline and hence the island as a whole from sustaining its width typically regressive barriers are wide and exhibit high elevations with the most seaward dune ridge possessing the highest elevation this morphology may prevent overwash and inlets from breaching the barrier and therefore the associated sediment from reaching the back barrier shoreline for millennia back barrier shoreline erosion from sea level rise and storms can be permanent in the absence of sediment supply from rivers overwash and inlet processes with continued narrowing and lowering of the island regressive barriers may reach a critical state making overwash and inlet formation imminent and transitioning the island to a transgressive barrier the modern day morphologic variability along the 40 km long island of bogue banks north carolina includes both regressive and transgressive segments making this setting ideal for examining whether the transition between these barrier island types is gradual or threshold driven bogue banks consists of two discrete segments characterized by high elevation beach ridges large island widths and stratigraphy consistent with regressive barrier islands these regressive island segments are separated by a broad narrow section of the island devoid of any washover fans flood tide deltas or other transgressive elements analyses of seismic data from the inner continental shelf reveal paleochannels intersecting the wide sections of the island while the narrow central part of the island occupies an inter fluvial area reworking of fluvial sediment from paleochannels was an important sediment source for the barrier during regression optically stimulated luminescence osl dates from the most landward beach ridges constrained initiation of island regression at 3000 cal yr bp close to when there was a significant decrease in the rate of relative sea level rise from 5 mm yr to 0 8 mm yr transects of cores seismic data ground penetrating radar data and radiocarbon and osl dates show that prior to 1500 cal yr bp the central narrow section of the island was wide and progradational similar to adjacent areas back barrier erosion of the central part of the barrier primarily caused island narrowing as a result of increased storminess which occurred around the medieval climate anomaly 1100 cal yr bp this part of the island was more vulnerable to erosion than adjacent areas due to increased bay ravinement bogue sound is widest there and its lower elevation farther away from paleochannel sediment source relict inlet channels exist along the central portion of the island formed within the last 250 yr and likely closed shortly after formation the presence of historical inlets along the narrow central section of the island indicates bogue banks may be nearing a critical width threshold and will subsequently transition to a transgressive barrier because the change in barrier morphology associated with back barrier erosion occurred over a period of time when the rate of sea level rise was relatively low low sediment supply and increased storm frequency are shown to be the main forcing mechanisms of island narrowing these impacts in addition to a predicted increase in sea level rise rates and human modifications e g maintenance of a high elevation foredune closing of inlets prevention of island overwash and associated sediment delivery to the back barrier shoreline will likely promote rapid transition of regressive barrier islands to those dominated by transgressive processes

distribution of arsenic iii arsenic v and total inorganic arsenic in porewaters from a thick till and clay rich aquitard sequence saskatchewan canada abstract inorganic arsenic species were measured in the porewaters collected from eighteen piezometers installed between 3 and 91 4 m below ground in a thick till and clay rich aquitard sequence located in southern saskatchewan to investigate the distribution of and controls on arsenic speciation in the sequence aqueous concentrations of as v as iii and total as are in the range of 0 31 97 0 71 21 and 3 2 98 ppb respectively profiles of as iii and as v concentration distribution with depth broadly track that of total as erratic increases to 15 2 m then more uniform concentrations to 88 m aqueous arsenic is accumulated at the upper redox transition zone 6 14 m the alkaline porewater at 91 4 m contains the highest concentrations of as v and total as which might result from the facilitated desorption of arsenate from the host solid due to decrease of positive surface charge of the oxides in alkaline solution the ratio of as v as iii is greater than unity in the uppermost oxidized porewater 3 m less than unity from 4 6 to 71 6 m and greater than unity in the lowest four porewaters 76 2 to 91 4 m in the 3 m porewater low as iii but high as v as iii is due to the oxidized nature of the near surface weathered till the high as v as iii in the deepest porewater at 91 4 m likely results from the enhanced and heterogeneous oxidation of as iii to as v on clay mineral surfaces in the alkaline solution total as and arsenic speciation may not be controlled by as fe or mn concentrations in the host till or clay dissolved as v and total as positively covary with aqueous chloride whereas dissolved as iii is independent of aqueous chloride aqueous as iii and to a less extent as v and total as are positively correlated with dissolved mn in the till in the clay aqueous as v and total as show strong negative covariation with mn however aqueous as iii as v and total as exhibit almost no correlation with total dissolved fe in the till the as v as iii ratio has strong negative correlation with dissolved mn but positive covaration with dissolved chloride generally good agreement between the redox potentials eh calculated from aqueous as v and as iii concentrations and those measured by a pt electrode throughout most of the unoxidized till suggests the suitability of using as v as iii redox couple as a redox indicator for the studied aquitard system however large negative bias of the calculated eh from the measured eh in the oxidized till upper unoxidized till and the clay is attributed to errors associated with the field measurements of eh

gravel barrier migration and overstepping abstract despite the widespread occurrence of gravel barriers on mid to high latitude coasts understanding of their stability and relationship to gravel deposits on the inner continental shelf remains rudimentary on sand dominated coasts subject to rising relative sea level barrier overstepping has been postulated as a mechanism for preservation of beach deposits on the shelf but direct observation of overstepping events has been lacking observations at a site on the atlantic coast of canada reveal migration of a gravel barrier at 8 m a 1 landward over back barrier mud following abandonment of part of the barrier volume on the shoreface this provides clear evidence for overstepping and suggests that it may play a role in the formation of inner shelf gravel deposits integrity of the migrating stretching barrier depends on continued sediment supply from the headland source to a connecting ridge which must become progressively longer as the landward displacement of the barrier increases

role of quaternary stratigraphy on arsenic contaminated groundwater from parts of barak valley assam north east india groundwater arsenic survey in cachar and karimganj districts of barak valley assam shows that people in these two districts are drinking arsenic contaminated max 350 g l groundwater 66 of tubewells in these two districts have arsenic concentration above the who guideline value of 10 g l and 26 tubewells have arsenic above 50 g l the indian standards for arsenic in drinking water 90 of installed tubewells in these two districts are shallow depth 14 40 m shallow tubewells were installed in holocene newer alluvium aquifers are characterised by grey to black coloured fine grained organic rich argillaceous sediments and are mostly arsenic contamination in groundwater plio pleistocene older alluvium aquifers composed of shale ferruginous sandstone mottle clay pebble and boulder beds which at higher location or with thin cover of newer alluvium sediments are safe in arsenic contamination in groundwater 91 of tubewell water samples show significantly higher concentrations of iron beyond its permissible limit of 1 mg l the iron content in these two districts varies from 0 5 to as much as 48 mg l most of the arsenic contaminated villages of cachar and karimganj districts are located in entrenched channels and flood plains of newer alluvium sediments in barak surma langai rivers system however deeper tubewells 60 m in plio pleistocene older alluvium aquifers would be a better option for arsenic safe groundwater the arsenic in groundwater is getting released from associated holocene sediments which were likely deposited from the surrounding tertiary barail hill range

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

impacts of hurricane ike on the beaches of the bolivar peninsula tx usa abstract hurricane ike caused substantial beach erosion along the coast of the bolivar peninsula tx much of the erosion was caused by the offshore ebb flow of the ca 5 m storm surge that formed spatially discrete scour features using aerial photography and repeat lidar data we identify five types of scour features and describe the alongshore distribution in four flow environments type 1 scours are relatively small and compact features associated mainly with flow off a wide vegetated grasses shrubs trees surface across a wide beach type 2 scours are large and branching forms associated mainly with flow that was channeled by streets or gaps between structures type 3 scours are large and blocky features associated with flow off a marsh surface across a highway which removed almost all beach sands from the surface type 4 scours are elongated shore perpendicular channels associated with the same flow characteristics as type 3 scours type 5 scours are elongated shore perpendicular features sometimes branching associated with flow through gaps in a destroyed shore protection structure repeat imagery indicates that many of the features persisted for at least seven months recent aerial photography indicates that aspects of some features remained evident more than three years after ike s landfall

morphological barrier island changes and recovery of dunes after hurricane dennis st george island florida abstract during the summer of 2005 hurricane dennis overwashed the eastern portion of st george island part of the northwest barrier island chain located along the florida panhandle in this paper lidar based morphological changes of the barrier island are analyzed along with the short term post storm recovery of secondary dunes results show that overwash from the storm surge removed nearly the entire foredune complex and the initial breaching probably occurred where the complex was either low or discontinuous in these locations beach widening was less in contrast approximately 10 m of beach widening occurred where foredunes were higher and continuous implying that more sediment was available for seaward transport during storm conditions the secondary dunes recovered at an average linear rate of 3 4 cm per month in the presence of vegetation although monthly averages varied from 1 5 to 1 4 m3 m and total volume changes varied from 17 9 to 16 4 m3 m for the duration of the study furthermore vegetation deterred dune migration thus favoring dune growth and reducing erosion due to wind in contrast the absence of vegetation inhibited dune growth insignificant changes in elevation occurred in areas of storm debris or lag deposit finally distributions of topographic gradients and curvature calculated numerically from pre and post storm lidar data are introduced as a potential tool in determining the relative post storm recovery of the dune field

erosional and depositional characteristics of regional overwash deposits caused by multiple hurricanes regional scale washover deposits along the florida gulf and atlantic coasts induced by multiple hurricanes in 2004 and 2005 were studied through coring trenching ground penetrating radar imaging aerial photography and prestorm and poststorm beach profile surveys erosional and depositional characteristics in different barrier island sub environments including dune field interior wetland and back barrier bay were examined over the eroded dune fields the washover deposits are characterized by an extensive horizontal basal erosional surface truncating the old dune deposits and horizontal to slightly landward dipping stratification over the marshes in the barrier island interior the washover deposits are characterized by steep tabular bedding with no erosion at the bottom overwash into the back barrier bay produced the thickest deposits characterized by steep prograding sigmoidal bedding no significant erosional feature was observed at the bottom washover deposits within the dense interior mangrove swamp demonstrate both normal and reversed graded bedding the washover deposits caused by hurricanes frances 2004 and jeanne 2004 along the southern florida atlantic coast barrier islands are substantially different from those along the northern florida barrier islands caused by ivan 2004 and dennis 2005 in terms of regional extension erosional features and sedimentary structures these differences are controlled by different overall barrier island morphology vegetation type and density and sediment properties the homogeneity of sediment along the northern florida coast makes distinguishing between washover deposits from ivan and dennis difficult in contrast along the atlantic coast barrier islands the two overwash events as demonstrated by two phases of graded bedding of the bimodal sediments are easily distinguishable

variations in storm response along a microtidal transgressive barrier island arc abstract storm response along the transgressive chandeleur barrier island arc southeast of the mississippi delta plain is variable because of local differences in sediment supply shoreline orientation and barrier morphology a study of the morphological impact of hurricane frederic 1979 affirmed that tropical storms are the primary agents causing erosion and migration of this barrier arc frederic s greatest impact was in the duneless southern chandeleurs where sheet flow overwash caused flattening of the barrier profile destruction of a strip of marsh 50 100 m wide and shoreline retreat of approximately 30 m in contrast overwash in the northern chandeleurs was confined between dunes in channels established by previous storms this channelized overwash breached the northern chandeleur barriers in nineteen places as frederic passed return flow through these channels transported overwashed sediment back to the nearshore zone these ebb deposits were a source for longshore drift sediments which quickly sealed storm channels reestablishing a coherent northern chandeleur barrier arc these storm response patterns may help explain long term changes in barrier morphology during an 84 yr period 1885 1969 the southern chandeleurs decreased 41 in area with an average retreat rate of 9 1 m yr 1 compared to a 15 increase in area and an average shoreline retreat rate of 7 2 m yr 1 for the northern chandeleurs

hydrodynamic and sedimentary responses to two contrasting winter storms on the inner shelf of the northern gulf of mexico abstract results are presented from the deployment of three bottom mounted instrumentation systems in water depths of 6 9 m on the sandy inner shelf of louisiana usa the 61 day deployment included nine cold front passages that were associated with large increases in wind speed two of the most energetic cold front passages were characterized by distinct meteorological hydrodynamic bottom boundary layer and sedimentary responses and may potentially be treated as end member types on a continuum of regional cold front passages arctic surges ac storms have a very weak pre frontal phase followed by a fairly powerful post frontal phase when northeasterly winds dominate migrating cyclones mc storms are dominated by a strong low pressure cell and have fairly strong southerly winds prior to the frontal passage followed by strong northwesterly winds on the basis of measurements taken during this study ac storms are expected to have a lower average significant wave height than mc storms and are dominated by short period southerly waves subsequent to the frontal passage currents are weak and northerly during the pre frontal phase but become very strong and southwesterly following the passage sediment transport rate during as storms was not as high as during mc storms and the mean and overall direction tended to be southwesterly to westerly with low frequency flows producing easterly transport and wind wave flows producing southeasterly transport mc storms had the most energetic waves of any storm type with peaks in significant wave height occurring during both the pre and post frontal phases the wave field during mc storms tended to be more complex than during as storms with an energetic northerly swell band gradually giving way to a southerly sea band as the post frontal phase progressed currents during mc storms were moderate and northerly during the pre frontal phase but became much stronger and southeasterly during the post frontal phase shear velocity was high during both the pre and post frontal phases of the storm although sediment transport was highest following the frontal passage mean and overall sediment transport was directed southeasterly during mc storms with low frequency and wind wave flows producing northerly transport in summary the data sets presented here are unique and offer insight into the morphosedimentary dynamics of mid latitude micro tidal coasts during extratropical storms

sand spit dynamics in a large tidal range environment insight from multiple lidar uav and hydrodynamic measurements on multiple spit hook development breaching reconstruction and shoreline changes

contrasting styles of hurricane irene washover sedimentation on three east coast barrier islands cape lookout north carolina assateague island virginia and fire island new york abstract storm surge and wind driven waves generated by hurricane irene which made landfall on the u s east coast on august 27 2011 resulted in overwash of sandy barrier islands from north carolina to new york state overwash has significant impacts on barrier island geomorphology it represents a sediment pathway into island interiors a component of island sediment budgets and can cause considerable aggradation of backshore surfaces important for potentially offsetting the effects of rising sea level this study describes the morphology texture and microfossil content of hurricane irene washover deposits at three contrasting barrier island sites cape lookout north carolina assateague island virginia and fire island new york at all three sites run up overwash occurred wherein waves were sufficient to overtop parts of the beach system and transport sediment inland however at fire island overwash was restricted by a higher elevational threshold to low spots in the beach system coinciding with pre existing breaches in foredunes the result was the formation of isolated thinner low volume washover fans at assateague island and cape lookout lower elevational thresholds allowed waves to overtop longer continuous sections of beach systems resulting in the formation of laterally continuous thicker larger volume washover terraces overall the deposits lacked consistent trends in thickness and texture such as thinning and fining inland reflecting a progressive reduction in overwash competence thickness and texture of the deposits were both spatially variable and probably reflect infilling of low points on the former surface and the influence of beach and foredune sediment sources all the washover deposits were essentially barren of foraminiferal microfossils supporting the textural evidence that the adjacent beach and foredunes were the predominant sediment sources

contamination of shallow aquifers by arsenic in upper reaches of tista river at siliguri jalpaiguri area of west bengal india arsenic is present in groundwater at siliguri jalpaiguri area west bengal india this is the place where tista river descending from the himalayas meets the alluvial plain the area represents alluvial fan and floodplains of tista mahananda balasan jaladhaka and its tributaries in the river sediment samples para and ferro magnetic minerals within 0 3 0 05 mm fraction contain 9 80 ppm of arsenic the study indicates that iron bearing minerals viz biotite hornblende as well as iron coated grains of the sediment are major contributors towards arsenic budget though magnetite as a mineral shows maximum arsenic content 22 ppm it is volumetrically not of much significance measurement of groundwater collected from tube wells shows up to 0 05 ppm of arsenic these arsenic contaminated tube wells occur in a linear fashion along the course of the rivers moreover localization of contaminated tube wells coincides with the change of channel gradient as observed in longitudinal section the study enumerates a cause effect relationship of arsenic occurrence with river gradient and fluvial sedimentation

simulating cross shore material exchange at decadal scale theory and model component validation a model is developed to simulate the cross shore cs exchange of sand and the resulting profile response at decadal scale to be used in regional coastal evolution models the cs model consists of modules for calculating dune erosion and overwash wind blown sand transport and bar berm material exchange the sand transport equations included in these modules are formulated based on relevant physics in combination with empirical observations and then validated towards laboratory and field data in order to couple the transport equations to the evolution of key morphological features describing the profile a set of sand volume conservation equations are employed and solved together with the transport equations the features that are modeled include dune height from dune foot to crest the locations of the landward dune foot seaward dune foot berm crest and shoreline as well as the longshore bar volume the cs model is employed and tested at three different field sites in a companion paper palalane et al 2016 whereas in the present paper the properties of the model are demonstrated by simulating the evolution of the dune berm and shoreline in connection with accretion and erosion of sand in a groin compartment this case derives from a study at westhampton beach that focused on shortening the length of a number of groins in order to release accumulated sand in the groin field to eroding downdrift beaches

a late pleistocene coarse grained spit platform sequence in northern jylland denmark several well preserved late pleistocene spit systems occur uplifted in northern jylland denmark their present day morphological expression allows detailed study of spit growth patterns while the internal sedimentological organisation can be examined in a series of pits distributed along the length of the spits two characteristic vertical sequences are recognized in the systems the first sequence i consists of a giant scale cross bedded foreset unit overlain by topset and beach units while the second sequence ii consists of the foreset unit overlain by bar trough and beach units the two sequence types pass laterally into each other with a short overlap zone they can be interpreted in terms of meistrell s 1966 1972 model for spit platform growth based on scaled wave tank experiments the giant scale cross bedded unit corresponds to prograding of a coarse grained subaqueous spit platform while the topset bar trough and beach units reflect the growth of the subaerial spit the alternation between sequence i and ii reflects the inversely related growth of the spit and platform structures when the rate of subaqueous platform progradation declines the subaerial spit grows uniformly and when the platform progrades uniformly spit growth declines the model is probably only valid for relatively coarse grained systems because only these deposits would have a relatively steep front the water depth in which the spit system progrades and thus bottom topography determines the thickness of the giant scale cross bedded foreset unit because the water depth over the top of the platform is relatively constant if the water is less than a few metres deep the spit platform is not developed as seen where the late pleistocene spit systems prograded over elevations of the sea bottom conversely the correct recognition of spit platform sequences allows precise determination of sea level and water depth at the time of formation finally the model adds one further mode of formation of giant scale cross bedding to those already known from fluvial transverse lateral and point bars subtidal sand waves and gilbert deltas

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

lidar time series analysis of a rapidly transgressing low lying mainland barrier caminada headlands louisiana usa abstract coastal barriers are the first line of defense against storm surge and wind wave induced hazards their response to such events therefore require continual assessment airborne lidar surveying is a valuable remote sensing technique used to assess the dynamics of coastal dunes driven by the impacts of storms and the subsequent recovery processes different from previous research conducted on this topic where pre and post storm surveys are employed to analyze the effects of isolated extreme events this study makes use of a 15 year lidar survey time series of the caminada moreau headlands the caminada moreau headlands located in louisiana usa on the gulf of mexico s northern coast is a low gradient low elevation mainland barrier which is rapidly eroding due to sediment deprivation alongshore sediment transport relative sea level rise and cumulative storm impacts the time period analyzed from 1998 to 2013 was notable for the number and intensity of hurricanes and tropical storms making landfall in the region the analyses of the lidar data show that while storms have frequently overwashed and destroyed the dunes natural dune recovery has managed to maintain a nearly stable alongshore averaged dune volume on the other hand change in dune crest elevation in the most vulnerable stretches of the coastline has not kept pace with sea level rise the analyses herein further suggest that for low elevation dunes which rapidly transition into backbarrier wetlands the relative quantity of subaerial land surface area to open water directly landward of the duneline is an influential parameter affecting barrier shoreline morphodynamics

relict progradational beach ridge complex on cat island in mississippi sound abstract comparative field and aerial photographic studies of the mississippi alabama gulf coast barrier islands reveal that cat island the westernmost barrier island in the series is unique in having a large number of prominent forested beach ridges the cat island ridge complex is composed of three distinct sets of sub parallel east west trending ridges the ridge set on the south side of the island is younger and less well developed than the older two sets there is considerable evidence that the barrier island system predates the eastward progradation of the st bernard lobe of the mississippi delta complex which began its eastward progradation about 3 000 years before present and continued until its abandonment approximately 1 500 years ago the low poorly developed ridges along the southern shore of cat island and the low ridges and broad swales of middle spit mark the transition to a more protected energy reduced environment that accompanied the eastward progradation of the st bernard delta into the area to the immediate south and southeast of cat island the development of the st bernard delta complex not only modified the previously existing longshore current and littoral sediment transport it also protected cat island from the erosional effects of waves and swell of the open gulf of mexico with the exception of a narrow window to the southeast the window lies between ship island the barrier island east of cat island and the chandeleur islands which are reworked distributary sands of the st bernard delta this restriction in the direction of wave approach has resulted in the partial reworking of the eastern end of the progradational ridge complex into a large northeast southwest trending spit thus giving cat island its unique t shape it is likely that during the pre st bernard delta period of robust sedimentation the other islands in the barrier chain also exhibited progradational ridges similar to those now found only on cat island unlike cat island which has been protected and preserved by the st bernard delta the other barrier islands have subsequently suffered a general reduction of sediment supply due to the weakening and eastward displacement of the littoral currents and have been modified and reworked during the past 1 500 years by processes of island and inlet migration and storm wave washover

mesoscale air sea interactions related to tropical and extratropical storms in the gulf of mexico data indicate that the climatological vorticity of the lower atmosphere of the northwestern gulf of mexico is relatively strong with monthly means exceeding a rossby number of 3 from october through march with a maximum of 4 6 in december it has been hypothesized that wintertime cyclogenesis over the northwestern gulf is enhanced by this lower level atmospheric vorticity field when it occurs simultaneously with appropriate upper level venting observations from november 1982 to mid february 1983 were studied in which seven significant cyclones were generated in the northwestern gulf it was found that all seven storms occurred when the vorticity correlate of horizontal air temperature difference was 3 5 c above the climatological mean difference although these results corroborate the postulate that such lower level vorticity is related to cyclogenesis the data from mid february through march 1983 were less supportive during those months only two of the six significant storms developed when the horizontal air temperature difference was above the climatological mean surprisingly the location of the most unstable air within the atmospheric boundary layer is not found in the northwestern gulf of mexico but instead along the shelf break relatively strong free convection in the atmospheric boundary layer is found over the loop current and the deep western gulf as expected the unstable regions of the deep gulf can enhance the potential for frontogenesis and cyclogenesis but it is likely that the linear character of the strong shelf break free convection does not enhance cyclogenesis it is shown that a maximum in the frequency of tropical storms within the gulf of mexico exists some 275 km south of the mississippi delta at 27 n 90 w this maximum is a result of only those storms which originate within the gulf two plausible effects of the loop current and its rings on tropical storms are discussed one is that these ocean features are large and consolidated heat and moisture sources from which a nearby slowly moving atmospheric disturbance can extract energy the second is that of the cyclonic vorticity that can be generated in the lower atmosphere by such oceanographic features