influence of cell size on volume calculation using digital terrain models a case of coastal dune fields abstract in this work we analyze how variation in cell size influences the volume calculated from digital terrain models dtms derived from a lidar light detection and ranging survey in two coastal late holocene dune fields in southern brazil cell size varied from 1 to 100 m rmse root mean square error of the resampled dtms from the original lidar with 0 5 m resolution increases linearly with cell size while r 2 coefficient of determination decreases following a second order trend the volume does not show simple linear or exponential behavior but fluctuates with positive and negative deviations from the original dtm this can be explained by a random factor in the position of the cell with regard to landforms and a relationship between cell and landform size wherein a small change in cell size can lead to an under or overestimation of volume the aster gdem global digital elevation model and x sar srtm shuttle radar topography mission 1 digital elevation models dems were not considered viable volume sources due to large deviations from the reference data either as a consequence of noise in the srtm x sar data or lack of bias elevation correction to a common reference base in the gdem processing chain volumes from a 3 arcsec sir c srtm deviated around 5 from the reference data and are considered suitable input for numerical simulations of quaternary dune field evolution models because these values should be within the expected range of sediment volume changes over hundreds to millions of years

high angle wave instability and emergent shoreline shapes 2 wave climate analysis and comparisons to nature 1 recent research has revealed that the plan view evolution of a coast due to gradients in alongshore sediment transport is highly dependant upon the angles at which waves approach the shore giving rise to an instability in shoreline shape that can generate different types of naturally occurring coastal landforms including capes flying spits and alongshore sand waves this instability merely requires that alongshore sediment flux is maximized for a given deepwater wave angle a maximum that occurs between 35 and 50 for several common alongshore sediment transport formulae here we introduce metrics that sum over records of wave data to quantify the long term stability of wave climates and to investigate how wave climates change along a coast for long point a flying spit on the north shore of lake erie canada wave climate metrics suggest that unstable waves have shaped the spit and furthermore that smaller scale alongshore sand waves occur along the spit at the same locations where the wave climate becomes unstable a shoreline aligned along the trend of the carolina capes united states would be dominated by high angle waves numerical simulations driven by a comparable wave climate develop a similarly shaped cuspate coast local wave climates along these simulated capes and the carolina capes show similar trends shoreline reorientation and shadowing from neighboring capes causes most of the coast to experience locally stable wave climates despite regional instability

frequency and magnitude biases in the fryberger model with implications for characterizing geomorphically effective winds abstract the fryberger model uses standardized wind data to estimate regional aeolian sediment drift potential dp which allows for interpretation and classification of aeolian dune landscapes this paper identifies systematic frequency and magnitude biases in the model that result from i variations in wind direction sector range which affects frequency bin size for determining percent occurrence of transporting winds and ii use of wind speed class mid point values over more statistically representative values e g mean median or minimally classified whole knot wind speeds in the magnitude weighting factor for dp calculations the significance of these biases is tested using unclassified data from stanhope prince edward island canada frequency bias resulting from wind data aggregation into direction sectors of varying size produces statistically significant discrepancies in dp and rdp estimates for this dataset when 36 point 10 s of degree data are reduced to 16 sectors cardinal directions receive one extra direction class and the magnitude of dp and rdp values decreases by 1 4 and 2 8 respectively compared to 16 equal 22 5 sectors derived from original data this results from under representation of intermediate direction classes for this dataset the effects on rdd less than 1 and directional variability ratio rdp dp are insignificant magnitude biases result from the use of the wind speed class mid point values instead of other statistically representative measures of wind speed in dp calculations in that wind speed distributions are often positively skewed mid point values yield an over estimate of total dp by as much as 34 and rdp by up to 22 for this dataset over those derived using mean median and whole knot minimally classified values this difference is statistically significantly at both the individual wind speed direction category level and at the aggregate directionally summed level and causes rdp vectors to shift 3 5 to the south though the impacts of these frequency magnitude biases are site specific and modest the effects on rdp estimation may be more significant in complex i e multi modal wind regimes and or in environments with more frequent high magnitude winds from the cardinal directions given the increased availability of more precise unclassified wind data most of these systematic frequency magnitude biases can be avoided recommendations on reducing inaccuracies imposed by these biases include i using to the degree wind data where available and categorizing into 16 equal 22 5 direction sectors ii using either wind speed class statistical mean values or minimally classified whole knot values in dp calculations and iii recognizing that converting 36 point 10 s of degrees data to 16 direction classes may introduce a frequency bias toward the cardinal directions and will cause inaccuracies in dp and rdp estimates of an amount that depends on the wind regime further research is needed to assess the implications of such biases in different wind regimes and into the influence of localized supply and transport limiting factors on regional scale assessments of dune morphodynamics and mobility these findings are also relevant for other applications that use categorized wind speed direction data such as dust or contaminant plume dispersion modelling

beach ridges and prograded beach deposits as palaeoenvironment records abstract beach ridges are landforms commonly developed on prograded coasts with beach shorelines a sequence of beach ridges coupled with their subsurface deposits can be regarded as a time series of coastal evolution methodological advances in field surveying and chronology applicable to beach ridges have led to detailed palaeoenvironmental reconstructions to be derived from such sequences this paper reconsiders the basic aspects of beach ridges and deposits which need to be properly understood for their comprehensive interpretation in a palaeo environmental context it also reviews case studies in which beach ridge sequences have been used to unveil past sea level history catastrophic events and climate changes proposed formative processes of beach ridges include 1 progradation of sandy beach and berm formations in relation to fairweather waves coupled with aeolian foredune accumulation 2 building of gravel ridges by storm waves 3 welding of longshore bars beach ridge formation through sea level oscillation is thought to be questionable and caution is suggested for this process when undertaking palaeoenvironmental reconstruction beach deposit stratification is known to dip either landwards or seawards but landward dips are uncommon seaward dipping stratification is formed in relation to beachface progradation and is usually dissected in places by erosion surfaces resulting from episodic beach retreat the boundary between the foreshore and the underlying shoreface is well defined only in the case that longshore bars lead to complex bedding structure relative to that of the foreshore reliable chronology of beach ridges can be determined by radiocarbon and optically stimulated luminescence osl dating radiocarbon dating of articulated shells which are considered not to be extensively reworked provides robust results but osl dating is more useful as it enables direct dating of sediment grains it is noted that there are restrictions in chronological resolution and continuity inherent to beach ridge and beach deposits the plan view geomorphic expression of beach ridges typically consists of ridge sets with multi decadal intervals whereas their internal sedimentary structures define shorter time scales records of beach sedimentation and erosion are likely to be reworked by episodic high magnitude beach retreat and the resultant record of the net progradation is likely to be sporadic and discontinuous the height of sandy beach ridges is often variable due to differing degrees of aeolian sand accumulation and they are thus not used as sea level indicators unless purely wave built gravel ridge height is a relatively reliable indicator of sea level but can vary in response to storminess fluctuations subsurface sediment facies boundaries are preferred as sea level indicators and those proposed include boundaries of aeolian beach foreshore shoreface and upper lower shorefaces catastrophic events are expressed in both erosional and depositional records erosion surfaces or scarp imprints revealed in a cross section of beach deposits indicate storm or tsunami events however erosional events are likely to rework previous records of sedimentation and even other erosional events and thus the apparent history decoded from the resultant deposits tends to be biased several attempts for estimating the frequency and intensity of prehistoric cyclones rely on assumed relationships between the level of coarse sand beach ridges and cyclone inundation the formative process of coarse sand ridges remains uncertain and needs to be clarified as it constitutes the fundamental basis of these attempts the growth rates of beach ridge systems are expected to reflect fluctuations in river sediment discharge to the coast and in aeolian sand flux due to onshore winds both of which are affected by climate change assessment of the growth rate is potentially improved by ground penetrating radar survey of subsurface structure and by detailed chronology orientation of beach ridges reflects long term trends in wave direction inferred relationships between beach ridges and cyclic fluctuations of sea level and climate rely on weak assumptions and are not substantiated by rigid chronological evidence and thus remain highly questionable correlation between the inherently decadal signal of beach ridge intervals and possible climate cycles such as sunspot activity is probably coincidental as it lacks causal explanations

formation of coastline features by large scale instabilities induced by high angle waves along shore sediment transport that is driven by waves is generally assumed to smooth a coastline this assumption is valid for small angles between the wave crest lines and the shore as has been demonstrated in shoreline models but when the angle between the waves and the shoreline is sufficiently large small perturbations to a straight shoreline will grow here we use a numerical model to investigate the implications of this instability mechanism for large scale morphology over long timescales our simulations show growth of coastline perturbations that interact with each other to produce large scale features that resemble various kinds of natural landforms including the capes and cuspate forelands observed along the carolina coast of southeastern north america wind and wave data from this area support our hypothesis that such an instability mechanism could be responsible for the formation of shoreline features at spatial scales up to hundreds of kilometres and temporal scales up to millennia

the morphodynamics of beach ridge formation magilligan northern ireland abstract magilligan foreland is a holocene beach ridge plain comprising three principal sets of sand ridges sets i and ii are related to the mid holocene progradation of the plain while set iii represents recent deposition at the distal margin at present two types of beach ridge are being formed in both cases as part of the general recovery sequence following storm erosion of the dune cliffs mode i beach ridge development is associated with shore normal sediment transport under dissipative wave conditions these ridges form around the high water mark of spring tides through the migration of coalescence of swash bars within 30 to 55 days of a storm mode ii formation is more complex sediment initially stored in nearshore bars is moved alongshore causing bar elongation the bar moves into the intermediate and even reflective wave domains eventually narrowing of the bar leads to severance of a downdrift portion usually at or near the major drift pulse to the north west of the foreland normally this sediment starved remnant welds progressively onto the beach face in the direction of the dominant process gradient east to west but occasionally locally generated counteractive seas move sediment onshore employing the bar as a traverse conduit mode ii beach ridges emerge onto the upper beach around 90 150 days after a storm the beach ridges have distinctive structures depending on their mode of formation and both constitute important sources for dune building sand

late holocene formation of lake michigan beach ridges correlated with a 70 yr oscillation in global climate abstract a radiocarbon dated series of 75 beach ridges formed at regular intervals averaging 72 yr over the past 5400 yr provides further support for the existence of a 70 yr oscillation in northern hemisphere climate postulated recently from instrument data representing less than two cycles of this climate oscillation results from this study lend support to the interpretation that internal variations in the ocean atmosphere system are an important factor in climate fluctuations on a decadal centennial time scale a temperature oscillation with a period of about 70 yr has been a previously unrecognized but fundamental part of the global climate system since at least the middle holocene

quantifying rates of coastal progradation from sediment volume using gpr and osl the holocene fill of guichen bay south east south australia guichen bay on the south east coast of south australia faces west towards the prevailing westerly winds of the southern ocean the bay is backed by a 4 km wide holocene beach ridge plain with more than 100 beach ridges the morphology of the guichen bay strandplain complex shows changes in the width length height and orientation of beach ridges a combination of geomorphological interpretation shallow geophysics and existing geochronology is used to interpret the holocene fill of guichen bay six sets of beach ridges are identified from the interpretation of orthorectified aerial photographs the ridge sets are distinguished on the basis of beach ridge orientation and continuity a 2 25 km ground penetrating radar gpr profile across the beach ridges reveals the sedimentary structures and stratigraphic units the beach ridges visible in the surface topography are a succession of stabilized foredunes that overlie progradational foreshore and upper shoreface sediments the beach progrades show multiple truncation surfaces interpreted as storm events the gpr profile shows that there are many more erosion surfaces in the subsurface than beach ridges on the surface the width and dip of preserved beach progrades imaged by gpr shows that the shoreface has steepened from around 2 9 to around 7 5 the changes in beach slope are attributed to increasing wave energy associated with beach progradation into deeper water as guichen bay was infilled at the same time the thickness of the preserved beach progrades increases slightly as the beach prograded into deeper water using the surface area of the ridge sets measured from the orthophotography and the average thickness of upper shoreface foreshore and coastal dune sands interpreted from the gpr profile the volume of holocene sediments within three of the six sets of beach ridge accretion has been calculated combining optically stimulated luminescence osl ages and volume calculations rates of sediment accumulation for ridge sets 3 4 and 5 have been estimated linear rates of beach ridge progradation appear to decrease in the mid holocene however the rates of sediment accumulation calculated from beach volumes have remained remarkably consistent through the mid to late holocene this suggests that sediment supply to the beach has been constant and that the decrease in the rate of progradation is due to increasing accommodation space as the beach progrades into deeper water changes in beach ridge morphology and orientation reflect environmental factors such as changes in wave climate and wind regime

high angle wave instability and emergent shoreline shapes 1 modeling of sand waves flying spits and capes 1 contrary to traditional findings the deepwater angle of wave approach strongly affects plan view coastal evolution giving rise to an antidiffusional high wave angle instability for sufficiently oblique deepwater waves with angles between wave crests and the shoreline trend larger than the value that maximizes alongshore sediment transport 45 a one contour line numerical model shows that a predominance of high angle waves can cause a shoreline to self organize into regular quasiperiodic shapes similar to those found along many natural coasts at scales ranging from kilometers to hundreds of kilometers the numerical model has been updated from a previous version to include a formulation for the widening of an overly thin barrier by the process of barrier overwash which is assumed to maintain a minimum barrier width systematic analysis shows that the wave climate determines the form of coastal response for nearly symmetric wave climates small net alongshore sediment transport cuspate coasts develop that exhibit increasing relative cross shore amplitude and pointier tips as the proportion of high angle waves is increased for asymmetrical wave climates shoreline features migrate in the downdrift direction either as subtle alongshore sand waves or as offshore extending flying spits depending on the proportion of high angle waves numerical analyses further show that the rate that the alongshore scale of model features increases through merging follows a diffusional temporal scale over several orders of magnitude a rate that is insensitive to the proportion of high angle waves the proportion of high angle waves determines the offshore versus alongshore aspect ratio of self organized shoreline undulations

sedimentation on intertidal mudflats in the lower part of macrotidal estuaries sedimentation rhythms and their preservation the objective of this study is to propose an original approach to the analysis of the formation of intertidal rhythmites their preservation and the evaluation of sedimentation rates on estuarine mudflats three mudflats one from each of three estuaries were analysed using a combination of long term a year high frequency 1 burst 10 or 20 min and high resolution 0 2 cm altimeter datasets and x ray images of sediment cores collected during topographic surveys the results highlight the roles played by sediment supply hydrodynamics and morphology of the lower estuaries on the sedimentation rhythms while the sediment starved medway estuary kent uk remains stable at different time scales the annual sedimentation rates on the sheltered authie mudflat pas decalais france and the open seine mudflat normandy france are relatively high at 18 and 15 cm yr 1 respectively on the authie mudflat sedimentation rhythms correspond to the semi lunar cycle with a good correlation between tidal range and deposit thickness sedimentation occurs at the beginning of the recovery mean value of 0 25 cm per semi diurnal cycle and is not disturbed by wind induced waves in the lower seine estuary semi diurnal mechanisms of deposition occur mainly when the mudflat is covered by a minimal water height tidal range threshold value 7 1 m sedimentation rhythms are discontinuous and deposition occurs only during the highest spring tides mean deposit thickness is 0 6 cm per semi diurnal cycle controlled by the turbidity maximum and the long high tide slack 2 3 h the fluid mud is sensitive to wind waves in this open funnel shaped estuary which undergoes wind induced erosion 0 2 to 2 cm about 10 times per year comparison of altimeter datasets and lithology of the sediments cored at the same points provided improved understanding of the sediment record rhythms and the sedimentation events on the sediment starved medway mudflat the result of sediment processes is a single superficial lamina the elementary deposit in the authie bay corresponds to a semi lunar linked layer typical of sheltered environments on the lower seine mudflat sedimentation rhythms are linked to the highest spring tides i e the lunar cycle resulting from increased sediment availability related to the high suspended matter concentration in the turbidity maximum these results underline the complex response of intertidal mudflats to hydrodynamics and sediment supply conditions from the semi diurnal to the annual scales

some considerations of the 210pb constant rate of supply crs dating model one of the most widely used radionuclides in the study of recent sedimentation processes is 210pb its depth profile in sediments is used as input for various dating models which provide chronologies mass fluxes and sedimentation rates in this work we revisited the crs constant rate of supply model widely used for dating sediments through 210pb a more general hypothesis periodic flux pf was proposed and although it confirmed the validity of crs chronology a detailed analysis of the mass sedimentation formula pointed out an inconsistency of the cited model a new mass sedimentation formula was proposed and validated with a lake sediment core and four marine sediment cores

sea level markers identified in ground penetrating radar data collected across a modern beach ridge system in a microtidal regime sea level rise has been related to global warming the modern system on the northern coast of anholt denmark may well be analogous to other beach ridge systems formed in microtidal regimes and our results should have impact on estimation of past sea level variation ground penetrating radar data collected across the modern 30 years old berm beach ridge and swale deposits resolve downlapping reflections interpreted to mark sea level at the time of deposition existing time series of sea level data constrain actual sea level variation nineteen readings of sea level markers made along our profile fluctuate within 0 42 and 0 57 m above present mean sea level consistent with 95 of the sea level data these fluctuations reflect tidal effects and meteorological conditions main data uncertainties are well known and the sea level markers may be identified with a high degree of confidence

beach ridge development and lake level variation in southern lake michigan abstract the most accurate source of information on lake level fluctuations in the great lakes is the historical record from lake level gauges although it can be semiquantitatively extended back into the late 1700 s the historical record is too short to recognize long term patterns of lake level behavior to extend the historical record information must be obtained from the great lakes geologic record such information includes the elevation and age of geomorphic features and stratigraphic sequences one of the longest geologic records of late holocene lake level variation is preserved in a beach ridge complex along the southern shore of lake michigan called the toleston beach this strandplain contains over 150 beach ridges that arc across northwestern indiana and fan out into northeastern illinois each ridge was formed during the fall from a high lake level and the elevation of the foreshore deposits in each ridge provides information on the upper physical limit of lake level over the past 4000 years three scales of quasi periodic lake level variation were determined by radiocarbon dating basal peats of wetlands between the ridges and by measuring the elevation of foreshore swash deposits within ridges these three scales are 1 a short term and small scale fluctuation of 25 to 35 years with a range of about 0 5 to 0 6 m 2 an intermediate term and meso scale fluctuation of 140 to 160 years and a range of about 0 8 to 0 9 m and 3 a long term and large scale fluctuation of 500 to 600 years and a range of 1 8 to 3 7 m the short term and intermediate term fluctuations are reflected in the historical record an increase in the rate of shoreline progradation from east to west across indiana s shoreline causes differential preservation of the lake level fluctuations that is groups of four to six ridges in the western part of the strandplain that formed in response to the small scale fluctuations combine eastward into single ridges and groups of ridges representing the meso scale fluctuations the large scale fluctuations produced the most dramatic response in the western part of the toleston beach here following each high stand individual spits prograded southward off of a bedrock headland the successive spit extensions created several small lakes landward of the spits and started the 20 km eastward stream mouth deflection of the grand calumet river across indiana s western lakeshore

holocene depositional history of a microtidal cuspate foreland cape cape lookout north carolina abstract the holocene stratigraphy of cape lookout north carolina and the connecting barrier limb core banks displays sharply contrasting depositional histories beneath the core banks barrier chain a transgressive sequence of overwash storm deposits rests on back barrier silty sands and salt marsh peats evidence of the island s erosive landward migration however core holes drilled at cape lookout reveal a regressive vertical stacking of sediments that marks a major holocene facies change here fine grained burrowed shoreface deposits are overlain by coarse grained horizontally bedded barrier washover sands cape lookout has evolved during the late holocene as a prograding cuspate spit type of headland this accretion is a result of the combined effects of oceanic washover deposition with sand accumulated from a dominant southerly longshore transport during the past 4000 years the rate of sea level rise slowed markedly in the area resulting in a decreased rate of landward migration for core banks as the island became relatively stable with respect to sea level rise large volumes of sand were being transported along shore to cape lookout and offshore to its subaqueous shoals the slower landward retreat of the island probably allowed for a rapid southerly extension of core banks along with a buildup of the cape lookout shoals the sedimentation and growth of cape lookout over the past 4000 years probably reflects a similar history of development for other capes and shoals along the southeastern coast of the united states the large scale cuspate morphology present today may therefore be a relatively recent phenomenon

foredunes and blowouts initiation geomorphology and dynamics this paper reviews the initiation dynamics geomorphology and evolution of incipient foredunes established foredunes and blowouts incipient foredunes may be initiated in a variety of ways leading to the formation of ramps terraces or ridges depending on progradation rates vegetation type and cover sediment transport rates and scale of erosional processes vegetation cover morphology growth rates and types combine with aerodynamic processes to determine dune and swale morphology established foredunes are classified into five morpho ecological types and the flow behaviour over two types is detailed a new model of foredune evolutionary paths at various possible time scales is presented blowout initiation dynamics and sediment transport and evolution is examined throughout the review the gaps in present understanding of dune processes and a range of ideas for new research possibilities are provided

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

storm generated morphological change and longshore sand transport in the intertidal zone of a multi barred macrotidal beach abstract the morphology hydrodynamics and sediment transport processes of a multi barred macrotidal beach were surveyed over 21 semi diurnal tides the first eight of which were dominated by storm conditions with offshore wave heights ranging from 1 2 to nearly 3 5 m the hydrodynamic conditions prevailing over the intertidal beach showed a rapid response to these storm conditions notably through strong longshore currents that attained peak velocities of 1 6 m s 1 i e over three times the peak spring tide velocities of tide generated longshore currents during calm conditions the bars showed no cross shore migration during the storm events morphological mapping of the beach tracer dispersal patterns and calculations of potential sand transport rates using the energetics based model of bailard bailard j a 1981 an energetics total load sediment transport model for a plane sloping beach j geophys res 86 10938 10954 showed significant longshore sand transport as well as longshore migration of an intertidal drainage channel these longshore movements were bi directional responded to changes in incident wind and wave directions and involved wave stirring coupled with longshore advection of sand along the bar crests in particular strong trough and cross shore channel flows also led to the longshore migration of crescentic dunes the longshore sediment movements were embedded in a cross shore gradient associated with increasing overall profile mobility from the lower to the upper beach in response to wave shoaling and post breaking processes assessed through examination of the relative wave height hs h 1 based on the relationship between significant wave height hs and water depth h longshore sediment transport is a characteristic feature of the long term evolution of wissant bay which is dominated by a net northeastward residual sand transport within a bay sediment cell characterised by significant updrift erosion and downdrift accumulation longshore transport should be considered as an essential element of the morphodynamics of bar trough beaches subject to large tidal ranges and significant wind stress but there is a need for a better understanding of the role of wind stress on longshore currents in the shallow intertidal zone of these beaches

regional variation of coastal morphology in southwestern australia a synthesis abstract the morphology of landforms on the south coast of western australia is determined predominantly by wave refraction around discrete headlands and islands wherever offshore structures protect the shore from the direct effects of swell sheltered sandy beaches have developed in association with cuspate forelands and tombolos in contrast to this open coast setting the nearshore waters of the west coast are protected by semi continuous reef systems which significantly modify the morphology of large scale accretionary landforms beaches and foredune sequences on the south coast foredune plains occur primarily as fill in sheltered embayments and storm built ridges do not occur foredunes on the west coast include washover ridges and low aeolian dunes on the backshore of embayment and inset beaches the form of high wave energy beaches of the south coast fluctuates between reflective and dissipative morphodynamic states and most commonly between transitional and dissipative states sediments are mainly fine grained siliceous sands in contrast the low energy west coast beaches are composed of medium to coarse grained calcareous sands the beaches are planar in section characterised by lines of debris deposited by tidal and longer term fluctuations in sea level and their form does not alter with short term changes in the wave regime despite the very low energy micro tidal conditions experienced by the coasts of southwestern australia systematic variation in the morphology of coastal landforms does occur as protection to the coast increases from the open fetch south coast environment to the reef protected west coast setting swell energy decreases there is an increase in the relative importance of locally generated wind waves wave set up and tidal forcing of currents and forelands become increasingly asymmetric due to the strength of longshore sediment transport

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

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

a note on the use of the fryberger method for evaluating potential sand transport by wind the fryberger method provides a useful and accessible way of evaluating potential sediment transport by wind in this method an equation is used to estimate relative rates of sand transport expressed as drift potential from measurements of wind velocity however the values of drift potential obtained through the calculations are dependent upon the units in which wind velocities are expressed this paper highlights some of the confusion this dependence can cause and aims to clarify the ways in which values of drift potential can be interpreted

short term 2 yrs estuarine mudflat and saltmarsh sedimentation high resolution data from ultrasonic altimetery rod surface elevation table and filter traps rates of short term up to 2 years bed elevation change and sedimentation from mudflats to salt marshes were measured in a rapidly infilling macrotidal estuary using an original combination of three high resolution techniques an ultrasonic altimeter the rod surface elevation table rset method and filter traps the authie estuary is located on a straight sand rich coast and is undergoing rapid infill under the influence of flood dominant tides reinforced by wave action the estuarine sediment suite consists of both mud and sand derived from the sea of sand derived from storm wave erosion of dunes lining the north bank of the estuary and to a much smaller extent of mud from the river catchment bed elevation change and sedimentation rates show an expected increase with the duration of tidal flooding hydroperiod in both space and time the estuarine bed sediment suite changes from sandy at the mouth to muddy within the low energy inner estuary where mudflats are rapidly accreting paving the way for the formation of increasingly denser and mature salt marshes from the high sedimentation pioneer zone to the upper marsh where annual sedimentation is very low recorded variability in rates of bed elevation change and sedimentation reflect the influence of estuarine macro scale and local sediment transport and depositional processes in a macrotidal context dominated by high inputs of allochthonous sediments

coal petrographical characterization of the mecsek bituminous coal basin with special reference to the contact metamorphism of coal seams abstract the bituminous coals of the mecsek mountains were formed during the early lias and are of paralic origin the limnic complex of the layers consists of sandstone aleurite and coal and the upper layer contains marl of marine origin the 9 15 minable coal seams have a thickness of 1 2 14 0 m the mecsek coal field and the coal complex within it show a folded and fractured structure and with regard to their mechanical behaviour are strongly stressed 75 90 of the coal material is vitrinite and 1 14 is inertinite the quantity of liptinite is smaller than 9 the coal rank is that of gas coal and fat coal with a reflectivity of 0 85 1 5 respectively the coal rank differences and variations according to zones are the consequence of forces of various magnitude that occurred in the course of orogenic movements during the early cretaceous there was some under sea bed volcanic activity in this field the diabasic material of which appeared in the form of a bed vein along the coal seams and this has exerted a strong metamorphic influence on the coal it has resulted in thermo contact alteration i e in the appearance of natural coke and semicoke of various degrees of metamorphism this alteration badly affected the quality and technological characteristics especially the cokability of the coal

properties of a lacustrine subbituminous k1 seam with special reference to the contact metamorphism soma turkey abstract the subbituminous k1 seam in the middle miocene soma formation of western turkey reaches a thickness of 24 m typical samples on an air dried basis have 9 5 14 2 moisture 4 3 13 8 ash and 0 57 2 54 total sulphur the coal rank parameters and non agglomerating behaviour show that the coals are of subbituminous a rank the k1 seam is huminite rich coal with a mean random ulminite reflectance rr between 0 46 and 0 49 fluorescence emission measurements show that the sporinite cutinite resinite and alginite present have typical fluorescence spectra between 460 and 700 nm the soma formation was intruded by an olivine basalt during the pliocene pleistocene which caused local contact metamorphism at the top of the k1 seam on the basis of proximate ultimate and petrographic analyses the intruded seam can be divided into normal coal transition zone and natural coke intervals each differing in their degree of metamorphism moisture volatile matter hydrogen and oxygen contents very rapidly decrease close to the contact point with the intrusion whilst calorific value carbon content and mean random reflectance value increase a diagram ofo c versus h c also shows a distinct increase in rank caused by the intrusion minor illite siderite and plagioclase feldspar are present in the natural coke samples butpyrrhotite is not observed mineralogical geochemical and reflectance studies indicate that the general temperature during formation of natural coke was probably relatively low

formation temperatures of natural coke in the lower silesian coal basin poland evidence from pyrite and clays by sem edx abstract the purpose of this paper is to show how sem edx can be applied in a study of coals altered to coke by a magnetic intrusion sem photographs reveal some textural features of a natural coke which would not be detectable using optical microscopy the similarity between images of natural and artificial coke is proof that temperatures over 350 c were experienced during contact metamorphosis crystal shapes of minerals are presented as evidence of hydrothermal activity in the contact zone and an average temperature level below 575 c pyrite is used as a geological thermometer its shape and composition showing the occurrence of incidental hot spots 750 c in contact with the dyke

aeolian dynamics over a coastal foredune prince edward island canada near surface airflow over a morphologically simple vegetated 8 m high foredune with a small wave cut scarp was measured for onshore to oblique onshore conditions during a low moderate 5 6 m s 1 wind event and a high velocity 11 18 m s 1 sand transporting gale event flow across the foredune was characterized by significant flow compression and acceleration up and across the foredune during both events during the gale a pronounced jet speed bulge developed at the foredune crest which increased in magnitude with increasing wind speed the vertical w velocity component of the 3d flow field was positive upwards across the stoss slope under low wind conditions but negative downwards during gale wind conditions with upslope acceleration during the low velocity event there was speed down within the vegetation canopy as would be expected for a porous roughness cover during the strong wind event there was speed up in the lower portion of the vegetation canopy and this was found up the entire stoss slope sediment transport during the gale force event was substantial across the beach and foredune despite the moderate vegetation cover and minimum fetch aeolian suspension was evident in the lee of the dune crest the observations presented herein show that strong storm winds are an effective mechanism for translating sediment landwards across a high vegetated foredune contributing sediment to the stoss slope crest and leeward slopes of the foredune and backing dunes copyright 2013 john wiley sons ltd

coastline orientation aeolian sediment transport and foredune and dunefield dynamics of mocambique beach southern brazil abstract this paper examines the role of coastline orientation on foredune and dunefield development at mocambique beach southern brazil the beach displays significant alongshore variations in exposure to the prevailing winds and waves grain size beach surfzone morphodynamic type foredune volume and type and dimensions of the holocene dune systems two wind analyses and calculation of aeolian drift potentials were carried out one based on 1 year of wind record and another based on a record of 34 years monthly topographic surveys of beach and foredunes on 5 profiles along mocambique beach were conducted over one year to obtain data on beach mobility and width aeolian sediment transport and foredune development southerly winds dominate and aeolian sediment supply is minimal in the south moderate in the central portion and high in the northern portion of the embayment the relationship between actual sediment supply foredune building and potential sediment supply is relatively poor over one year due to factors such as beach type and mobility beach moisture levels rainfall storm surge and wave scarping the intermediate term 34 year record indicates a strong relationship between foredune size and volume winds and shoreline orientation foredune volume is minimum in the southern part of the beach and greatest in the northern part of the beach the holocene barrier and dunefield development also reflects the long term control of shoreline orientation and increasing longshore gradient in exposure to southerly winds for the last 6000 7000 years a small foredune developed in the southern portion parabolics and small transgressive dunes in the central portion and a large scale transgressive dunefield in the northern portion

geochemical and mineralogical changes in a coal seam due to contact metamorphism sydney basin new south wales australia abstract the mineralogical changes in a bituminous coal seam thermally altered by a small basaltic intrusion have been investigated using electronic low temperature oxygen plasma ashing x ray diffraction and other laboratory techniques an assemblage dominated by montmorillonite and well crystallized kaolinite in the area away from the intrusion passes laterally to one dominated by illite and poorly crystallized kaolinite along with abundant dolomite and calcite at the actual contact point geochemical considerations of both the mineral matter and the igneous rock suggest that the changes in the clay fraction were produced by heating to temperatures of between 400 and 650 c for a relatively short period coupled with migration of potassium from the intrusive body into the coal seam heating at lower temperatures although causing an increase in vitrinite reflectance does not appear to have had a particularly significant effect at all on the clay minerals in the coal seam

lake michigan beach ridge and dune development lake level and variability in regional water balance abstract a sequence of northern lake michigan beach ridges records lake level fluctuations that are probably related to changes in late holocene climate historically episodes of falling and low lake level associated with regional drought led to the formation of dune capped beach ridges the timing of prehistoric ridge formation estimated by radiocarbon dating of plant macrofossils from early successional dune species shows that return periods of inferred drought averaged for time intervals of 100 to 480 yr ranged between 17 and 135 yr per drought during the last 2400 yr in five of ten of these time intervals the average return period ranged between 17 and 22 yr per drought these intervals of frequent ridge formation and drought were associated with the development of parabolic dunes which is indicative of high lake level and moist climate this seeming paradox suggests that unusually moist decades alternated with unusually dry decades during these time intervals regional water balance probably varied less during the time intervals when ridges formed less often and the lake produced no evidence of high level

optically stimulated luminescence dating of holocene relict foredunes guichen bay south australia abstract optically stimulated luminescence osl dating of quartz sand 106 150 or 150 200 m in bioclastic carbonate quartz sediments sampled from coastal relict foredunes beach ridges was undertaken to evaluate the utility of the osl method for studies of dune dynamics and to quantify rates of coastal progradation twelve sediment samples from a 4 km transect across a holocene embayment fill at guichen bay south australia were measured for their luminescence characteristics apart from one age inversion attributed to recent disturbance associated with mining the osl ages are in sequential order when considered in the context of their associated error terms the osl ages indicate an extremely rapid initial phase of sedimentation i e 1600 m within a few hundred years approximately 5 ka ago followed by a constant rate of progradation for the past 4 ka of 0 39 m a with a high level of association between distance across the embayment fill and luminescence age for this time interval an average rate of dune development of one dune every 80 yr from 3900 yr ago to the present day is apparent the osl ages for the late holocene indicate that the present beach state is largely in equilibrium with sediment supply

geomorphology and dynamics of a traveling cuspate foreland authie estuary france abstract cuspate forelands or salients occur all over the world in lakes estuaries and on ocean shores yet there have been few studies conducted on traveling cuspate forelands or salients that is forelands that migrate or travel alongshore this paper presents a study of a traveling foreland in the authie estuary france termed the bec du perroquet historical shoreline changes may be traced from the 1200 s ad and the region has experienced both marked intertidal subtidal accretion extending from the south and massive erosion in the north since this period an analysis of aerial photographs from 1947 until the present shows that the original bec foreland was established at the mouth of the authie estuary but gradually disappeared by the 1960 s and a new foreland developed in the middle of the northern central portion of the bay this foreland was composed of a suite of foredune ridges which have been successively eroded on the northern margin and initiated on the southern margin as the foreland traveled or migrated southwards as the foreland traveled south from 1947 to 2009 the northern part of the bay retreated more than 350 m while mid bay the coastline retreated 215 m as the foreland evolves and migrates incipient foredunes can develop rapidly e g 18 ridges formed in an 11 week period while at other times the ridges form slowly and may be eroded and disappear two or more foredune ridges may blend into a single ridge over time depending on the initial degree of vegetation cover on the ridge and swale set aeolian processes in dune swales are much more important in this system than in typical prograding foredune plain systems due to the sometimes marked lack of vegetation colonization in the swales following foredune ridge development and aeolian deflation of the swales along with blowout development is important particularly when they become open conduits to the beach as erosion of the nw foreland proceeds the ages of each of the surviving ridges on the foreland in 2009 have been determined and the evolutionary path of the ridges ascertained formerly intact relatively stable continuous ridges evolve to erosional knobs turrets and nebkha over time foredune ridges and swales can be extremely arcuate to semi circular in form where the foreland and especially the spit extension are exposed to a wide range of wind directions and where the shoreline trends through an arc of at least 270 this study illustrates a remarkable cycling of the formation destruction and reformation travel of a cuspate foreland over a 50 year period

beach ridges definitions and significance abstract beach ridges frequent components of quaternary coastal plains and other coastal landforms have been cited as indicators of the positions of ancient seashores and associated sea levels numerous authors utilized the term beach ridge for active and relict usually wave built supratidal and or intertidal forms wind built ridges have been only occasionally included in the definition the term was applied also to submerged landward shifting eventually stranded bars a consistent redefinition of the term is highly desirable beach ridges should include all relict strandplain ridges whether dominated by wave swash built or by eolian lithosomes all active ridge like shore features regardless of dimensions morphology and origin are excluded because of the resistance of coarse clastic ridges to wave and wind erosion swash built gravel or coarse shell storm ridges may build several meters above the level of high tide swash built high berms even on pure sandy beaches exceed the highest tides during episodes of wind induced record water levels frequently but not always burying underlying low relief berm ridges of berm lithosomes sequences of relatively steep multiple foredunes are commonly named beach ridge plains the narrow subparallel relict foredunes that form these strandplains presently are designated as eolian beach ridges beach ridges thus are defined as relict semiparallel multiple wave and wind built landforms that originated in the inter and supratidal zones until separated from the shoreline by progradation sandy pebbly or shell enriched backshore berm ridges behind an active foreshore should not be considered beach ridges strandplain progradation is either continuous or with the inclusion of subtidal cat s eye ponds discontinuous contrary to claims transgressive cheniers do not represent true cheniers alone within their overall progradational context cheniers a special category of beach ridges bracketed by subtidal intertidal mudflats may be transgressive or regressive in character landward driven transgressive ridges should be designated beach ridges only after they are stabilized on intertidal flats when recognizable between clearly identifiable intertidal and overlying eolian intervals the horizontal interface between these lithosomes in beach ridges may help the reconstruction of ancient tide lake levels diagnostic sedimentary textures structures and fossils however often may be unavailable in the deposits along with various types of elevated terraces composed of raised marine deposits and certain coastal landforms of erosional origin that occur worldwide beach ridges of clearly proven wave built origin may also serve as indicators of ancient higher than present sea levels

coarse clast ridge sequences as suitable archives for past storm events case study on the houtman abrolhos western australia prehistoric storm records are relatively scarce in most parts of the world this article presents storm records derived from coral rubble based geological archives of the houtman abrolhos archipelago located off the west coast of australia where the southernmost coral reefs of the indian ocean are found winter storm swell from the circum antarctic brave westerlies as well as tropical cyclone waves have left numerous ridge systems on dozens of islands of the archipelago all composed of coral rubble from adjacent reefs at three islands seven ridge systems were dated by three different methods u series 68 dates radiocarbon 64 dates electron spin resonance 7 dates 139 radiometric dates span the last 5500 years of the holocene in contrast to the geomorphological interpretation the age sequences show inversions hiatuses and different ages for the same ridge all pointing to complicated ridge formation processes time gaps some exceeding 1000 years are interpreted as phases of erosion and not as phases without storm activity

internal architecture of a raised beach ridge system anholt denmark resolved by ground penetrating radar investigations abstract the internal architecture of raised beach ridge and associated swale deposits on anholt records an ancient sea level the holocene beach ridges form part of a progradational beach ridge plain which has been interpreted to have formed during an isostatic uplift and a relative fall in the sea level over the past 7700 years the ridges are covered by pebbles and cobbles and commonly show evidence of deflation material presumably removed from the beach ridges and adjacent swales form the present dune forms on anholt ground penetrating radar gpr reflection lines have been collected with 250 mhz shielded antennae across the fossil ridge and swale structures the signals penetrate the subsurface to a maximum depth of 10 m below the fossil features the gpr data resolve the internal architecture of the beach ridges and swales with a vertical resolution of about 0 1 m gpr mapping indicates that the holocene beach ridges are composed of seaward dipping beachface deposits as well as minor amounts of inland dipping deposits of wash over origin the beachface deposits downlap on underlying shoreface deposits and we use these surfaces as markers of a relative palaeo sea level the new data indicate that the highest relative sea level at about 8 5 m was reached 6500 years ago 700 years later the relative sea level had dropped 0 7 m indicating a change in the relative sea level around 1 mm year this fall in the relative sea level most likely records the influence of an isostatic rebound causing younger beach ridge deposits to indicate lower sea levels

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

sandy berm and beach ridge formation in relation to extreme sea levels a danish example in a micro tidal environment abstract the formation of berms and their transformation into beach ridges in a micro tidal environment is coupled to wave run up and overtopping during extreme sea levels a straight forward comparison between extreme sea levels due to storm surges and active berm levels is impossible in the semi enclosed bays along the baltic sea quite often the maximum water levels do not coincide with the maximum intensity of the wave driven processes because of seiches in the baltic in this paper we look into the joined distribution of extreme water levels and high energetic wave conditions at feddet a sandy prograding spit on the south eastern baltic shores of zealand denmark the modern sandy beach at this location consists of a beachface with a shallow incipient berm a mature berm and a dune covered beach ridge it borders a beach ridge plain to the west where more than 20 n s oriented beach ridges and swales are present measured water level data from 1991 to 2012 and topographical observations carried out during fair weather period and during a storm event provided the basis for a conceptual model exhibiting berm formation and transformation into the local beach ridge system the character of extreme sea level events is identified using thirty three well described extreme events throughout a period of 15 years analysis of the meteorological conditions during these events revealed that berm formation only occurred during 20 of all extreme events when onshore winds high energy wave action and elevated water coincided these berm forming events had a mean return period of once every three years the average age between successive beach ridges on the beach ridge plain was about 180 years which means that the transformation of a berm into a single beach ridge is the result of a large number of storm episodes with high energy waves and extreme water levels

internal structure of mixed sand and gravel beach deposits revealed using ground penetrating radar mixed sand and gravel beaches are a distinctive type of coarse clastic beach ground penetrating radar gpr and photographic records of previous excavations are used to investigate the stratigraphy and internal sedimentary structure of mixed beach deposits at aldeburgh in suffolk south east england the principles of radar stratigraphy are used to describe and interpret migrated radar reflection profiles obtained from the study site the application of radar stratigraphy allows the delineation of both bounding surfaces radar surfaces and the intervening beds or bed sets radar facies the deposits of the main backshore berm ridge consist of seaward dipping bounding surfaces that are gently onlapped by seaward dipping bed sets good correspondence is observed between a sequence of beach profiles which record development of the berm ridge on the backshore and the berm ridge s internal structure the beach profile data also indicate that backshore berm ridges at aldeburgh owe their origin to discrete depositional episodes related to storm wave activity beach ridge plain deposits at the study site consist of a complex progradational sequence of foreshore berm ridge overtop and overwash deposits relict berm ridge deposits separated by seaward dipping bounding surfaces form the main depositional element beneath the beach ridge plain however the beach ridges themselves are formed predominantly of vertically stacked overtop overwash units which lie above the berm ridge deposits consequently beach ridge development in this progradational mixed beach setting must have occurred when conditions favoured overtopping and overwashing of the upper beachface interannual to decadal variations in wave climate antecedent beach morphology shoreline progradation rate and sea level are identified as the likely controlling factors in the development of such suitable conditions