land sea interaction and morphogenesis of coastal foredunes a modeling case study from the southern baltic sea coast abstract coastal foredunes are developed as a result of the interplay of multi scale land sea processes basic driving mechanisms of coastal foredune morphogenesis as well as natural processes and factors involved in shaping the foredune geometry are quantitatively studied in this paper by a numerical model aeolian sediment transport and vegetation growth on the subaerial part of a beach is simulated by a cellular automata ca approach while the sediment budget in the subaqueous zone serving as a sediment source sink for the foredune ridges is estimated in a process based model the coupled model is applied to a 1 km long section of a barrier coast swina gate in the southern baltic sea for a 61 year 1951 2012 hindcast of its foredune development general consistency is shown between the observational data and simulation results indicating that the formation of an established coastal foredune results from a balance between wind wave impacts and vegetation growth driven by an effective onshore wind and a boundary sediment supply small scale dunes develop on the backshore and migrate landward they are then trapped in a narrow strip characterized by a large density gradient of vegetation cover which separates the hydrodynamically active zone and the vegetated zone continuous accumulation of sediment in this strip induces the development of a foredune ridge according to the simulations the formation of an established coastal foredune has to meet three preconditions 1 an effective onshore aeolian transport 2 a net onshore or lateral sediment supply and 3 a climate favoring vegetation growth the formation of a new foredune ridge in front of an already existing foredune is determined by a combination of the sediment supply rate the extreme wind wave event frequency and the vegetation growth rate simulation results demonstrate a remarkable variability in foredune development even along a small 1 km coast section implying that the medium to long term land sea interaction and foredune morphogenesis is quite sensitive to boundary conditions and various processes acting on multi temporal and spatial scales

optically stimulated luminescence osl dating of coastal aeolian sand accumulation in sanday orkney islands scotland optically stimulated luminescence osl dating of sand has been used to identify periods of enhanced aeolian activity at two coastal archaeological sites in orkney that coincide with periods of holocene climatic deterioration recorded elsewhere in both scotland and w europe areas of tofts ness sanday were settled from the neolithic abandoned in the late neolithic early bronze age reoccupied and permanently abandoned in the iron age sand layers above the neolithic soils have been osl dated to about 4000 bp correlating well with a period of increased aeolian activity elsewhere in w europe osl dating of aeolian sands above midden deposits and a bronze age burial at lopness on sanday suggest dune development by 3000 bp although both sites also contain sand that was deposited during the little ice age several possible mechanisms may have contributed to an increase in aeolian activity during the holocene that led to the abandonment of these sites although volcanic eruptions in iceland cannot be disc

late holocene erosion in upland britain climatic deterioration or human influence the evidence for enhanced erosion in upland britain during the late holocene is evaluated though there is widespread evidence for recent soil erosion on high plateaux this has not been precisely dated radiocarbon dating confirms the occurrence of late holocene solifluction on high ground but at only one site has evidence been found for recent accelerated activity several areas however have yielded evidence of late holocene debris cone accumulation and parts of the scottish highlands experienced a drastic increase in debris flow activity over the past few centuries climatic deterioration and vegetation degradation resulting from overgrazing or burning are frequently cited as the causes of enhanced erosion but cause and effect are often related only by coincidence of timing in consequence only circumstantial evidence links erosion with climatic deterioration though anthropogenic influences have been more firmly established at a few sites the role of extreme events in initiating phases of uplan

luminescence dating of recent dunes on inch spit dingle bay southwest ireland fifteen samples of dune sand and three samples from a core taken in the beach face were collected from a sand spit which protrudes into dingle bay in southwest ireland the potassium rich feldspar grains from the samples were dated using a single aliquot luminescence protocol for infrared stimulated luminescence irsl signals no ages over 600 years were obtained which demonstrates the youth of the dune forms currently observed the youngest ages were about 150 years old but for these samples the scatter in the equivalent dose obtained as the mean of 18 measurements was higher than for the older samples

lithological anomalies in a relict coastal dune geophysical and paleoenvironmental markers 1 ground exposures of migration surfaces slipfaces of a relict holocene coastal dune along the southeastern baltic sea coast provide an ideal opportunity for establishing the causes of prominent reflections on geophysical profiles high amplitude reflections on high resolution ground penetrating radar gpr images correlate well with two major lithological anomalies 1 paleosols developed on dune slipfaces and 2 slipfaces consisting of heavy mineral concentrations hmcs paleosols serve as indicators of dune stability represent datable chronostratigraphic surfaces and help reconstruct dune paleo morphology hmcs have substantially higher magnetic susceptibility values than background quartz rich sands and where they are well developed can be also used for spatial correlation based on their occurrence at the study site these enriched horizons likely represent periods of increased wind activity storminess multiple hmcs upwind of paleosol p1 800 670 cal years bp likely reflect periods of intensified wind activity along the southeast baltic region during the medieval warm period

sand spit rhythmic development a potential record of wave climate variations arcay spit western coast of france abstract this study aims at showing the sedimentary and geomorphological records of wave climate variations by spits the studied spit arcay spit is located on the french atlantic coast and has displayed a rapid elongation since the beginning of the 19th century that potentially represents a two century long wave climate record wave climate and spit growth relationships are studied from two complementary methods 1 numerical modelling of wave and longshore transport temporal and spatial variabilities and 2 morphological monitoring based on the analysis of 4 historical maps 1811 1945 8 aerial photographs 1945 2000 and 17 satellite spot images 1987 2005 results at seasonal to interannual time scales show that the sand spit area gain variations are the result of variations in longshore transport themselves modulated mainly by wave height moreover energetic swells seem to cause massive sand accumulation and spit elongation whereas less energetic swells appear to be responsible for small sand accumulation and spit curvature at longer time scale decades to centuries increasing spit growth phases are also synchronised with periods of energetic swells or high storm surge frequency these results suggest that wave climate variations are the main factor controlling spit morphological evolutions

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

late holocene post 4000 years bp coastal dune development in northumberland northeast england the recent environmental history of coastal dune systems in northumberland northeast england has been examined using geomorphological stratigraphical and sedimentological techniques linked to radiocarbon and infrared stimulated luminescence irsl dating stratigraphies were determined from 22 vibracores and three sections and dune chronology was based on 28 14 c dates from peat and soil organic horizons and 26 irsl dates on k feldspar grains from within sand layers almost all dune systems are associated with regressive shorelines consequent upon a fall in relative sea level rsl from its holocene peak and indicate rsl functioned as a macroscale control on dune development where dunes are anchored on terrestrial sediment dune expansion may have been either transgressive or regressive in nature where near shore marine sediments form the dune substrate a regressive prograding dune model seems most likely most dune building occurred during the little ice age lia probably in a

sand invasion along the portuguese coast forced by westerly shifts during cold climate events phases of higher aeolian activity are responsible for the formation and movement of large transgressive dunefields well reported phases of aeolian activity in northwest europe are coincident with global cooling events and were related to enhanced westerly winds and storminess however the extent to which these climatic episodes influenced dunefield dynamics in southwest europe remains an open question ground penetrating radar gpr was used to image the stratigraphy of a cliff top coastal transgressive dunefield in portugal and reconstruct former windfield regimes using optically stimulated luminescence osl five major phases of aeolian activity were dated at 12 6 5 6 1 2 0 4 and 0 3 ka and related to coastal instability and enhanced westerlies these phases were later reconciled to favorable patterns of atmospheric circulation simulated by global and regional climate models at both synoptic and local scales respectively the results prove that major phases of aeolian activity in southwest europe are associated with the onset of cold climate events of global distribution coinciding with aeolian accumulation in northwest europe this implies the dominance of zonal westerlies along the western coast of europe from denmark to portugal during the onset of cold climate events model simulations suggest that the pattern of atmospheric circulation during periods of enhanced aeolian activity is compatible with prolonged negative phases of the north atlantic oscillation nao

optically stimulated luminescence dating of large storm events in northern scotland climate changes over the holocene have directly impacted on both coastal processes and human use of coastal areas this paper presents results from the dating of wind blown sand deposits collected from coastal and archaeological sites in northern scotland archaeological remains are frequently found interspersed with sand deposits and represent distinct periods of occupation of settlement sites within the local landscapes in some cases storm events sufficiently inundate the sites with sand to result in periodic abandonment storm events can also have dramatic results on adjacent rock coastlines with storm boulder ridges emplaced by large waves burying sand deposits on cliff top sites work has been undertaken using a quartz sar protocol to date sand deposition at two archaeological sites in orkney and a cliff top site in shetland these dates provide chronological information which help to construct regional chronologies of climatic instability and environmental change and allow the sar osl method to be assessed as an accurate sediment dating tool in this context

late holocene aeolian sedimentation in the tottori coastal dune field japan sea affected by the east asian winter monsoon many dune fields that have formed along the southern coast of the japan sea are influenced by the north westerly winter monsoon which transports beach sand landwards the tottori coastal dune field of the japan sea has not been disturbed much by human activities until the 20th century and thus is expected to provide a continuous record of the relationships between the winter monsoon and aeolian sedimentation we examined new ground penetrating radar profiles and optically stimulated luminescence osl ages of quartz sand from transverse dune ridges in the western part of the dune field in addition to existing data in the eastern part this allowed us to extend the study period to cover the past 1000 years and to effectively compare the sedimentary record with other coastal dune fields in east asia and other palaeoenvironmental proxies osl ages from older dune sediments suggest considerable aeolian activity from the 10th to 12th century ad whereas a hiatus of dune sediment record between the 12th and 15th centuries was detected these results suggest that during the medieval period aeolian activity was low or that extensive erosion removed most of the deposits since the late 15th century dune sedimentation has apparently been broadly continuous though with periods of higher and lower activity in both of the eastern and western parts most of the dune ridges accreted landwards but clear seaward accretion occurred during the 18th century possibly reflecting a decrease in wind strength that restricted sand transport in contrast two significant landward accretion events are inferred to have occurred from the late 15th to 17th centuries and around 1840 corresponding to periods of increased dust fall in china which suggests an enhanced winter monsoon and to cold periods suggested by the decline of the sunspot number the timing of periods of inactive and active dune sedimentation inferred from alternations of organic soil and aeolian sand in other coastal dune fields of east asia appears to be concordant with corresponding periods in the tottori dune field we thus propose that other japan sea dune fields may also provide a valuable record of east asian winter monsoon fluctuations

sand drift and soil formation along an exposed north atlantic coastline 14 000 years of diverse geomorphological climatic and human impacts this paper sets out the history of aeolian deposition and soil formation over the last 14 15 000 calendar years along the exposed and gale prone atlantic coastlines of the southern isles of the outer hebrides of scotland detailed palaeoenvironmental interpretation and chronological control have been provided by field mapping soil micromorphological analyses and radiocarbon and optically stimulated luminescence osl dating programmes two dominant types of aeolian sands are described in this region quartzose sands are shown to originate mainly as periglacial wind blown sands derived from glacial and periglacial deposits of late devensian age which were formerly exposed on the present continental shelf this aeolian deposition did however continue into the early holocene with re working perhaps by slope wash taking place as recently as the 4th millenniumbp quartzose sands mantle valley floors and hillslopes by the end of the devensian and early holocene a variety of soil types with extensive horizonation had developed upon them including podzolic brown earths peaty gleys and peat soils radiocarbon and osl dating demonstrate that the carbonate sands of the machair sand sheets which characterize the present atlantic shorelines began to accumulate very early for a european shoreline from approximately 8700 calendar years ago on benbecula and north uist whereas further south deposition began later osl dating suggests that non sequences and diastems are common in greater part these machair sand sheets are best interpreted as a composite of separate slivers of sand reflecting small scale and local episodes of sand drift rather than distinct layers of region wide distribution which might reflect past major storms or significant palaeoclimatic fluctuations the new evidence presented here provides little support for the following explanatory geomorphic or stratigraphic models which have previously sought to explain the development of these coastal machair landscapes continuous development layer cake or step wise prograding coastal barrier qualified support is given for the explanations that emphasize i the long term spasmodic input and re cycling of sands and ii that the present smoothed landscapes and distinctive machair grassland vegetation are essentially recent in age and reflect the interactions of natural and human processes in a stormy environment characterized by re working widespread layers of thick organic materials within the carbonate sands in the study area which have previously been regarded as dune palaeosols dating to the bronze age and iron age are suggested by soil micromorphological analysis to be in significant part anthropogenic in origin they are organically enriched layers or midden soils the consequence of human activities notably the disposal of organic wastes and other forms of soil modification during times of significant settlement in these coastal sands these periods of relatively intense human activity are therefore shown to be associated at least locally with periods of soil formation and stability not universal instability and dune drift along these shorelines in general these extensive layers of midden soil do not necessarily imply periods of decreased storminess relatively widespread soil formation in these coastal dunes did however take place in the period between 400 and 100 years ago essentially within the period of increased storminess associated with the little ice age it is suggested that at some point s within the following periods of time broadly defined in calendar yearsbp notable sand drift affecting the quartzose sands the carbonate sands or both took place within the study area 13 700 13 000 11 000 10 500 9000 8300 7500 7000 6900 6400 5800 4200 one of the most notable episodes of drift in the outer hebrides as well as elsewhere on the coast of north west europe 3800 3300 1700 1300 600 200 with individual great storms being recorded in the 17th and 18th centuries and 100 present day limited drift associated with machair stratification

theoretical constraints and chronological evidence of holocene coastal development in central and southern new south wales australia abstract holocene coastal evolution in new south wales has been interpreted essentially as the unfolding of the impact of marine transgression sea level on this coast supposedly reached its present height at 6 6 5 ka and varied

three dimensional numerical model for flow and bed deformation around river hydraulic structures this paper describes a numerical model developed to simulate flow and bed deformation around river hydraulic structures the model solved the fully three dimensional reynolds averaged navier stokes equation expressed in a moving boundary fitted coordinate system to calculate the flow field with water and bed surfaces varying in time a nonlinear k e turbulence model was employed in order to predict flow near the structure where three dimensional flow is dominant the temporal change in bed topography was calculated by coupling a stochastic model for sediment pickup and deposition using a momentum equation of sediment particles in order to account for the effect of nonequilibrium sediment transport in validating the numerical model a spur dike and a bridge pier which are considered to be typical river engineering structures were selected by comparing the numerical results with observed laboratory experimental data the model was found to reproduce flow and scour geometry around these structures with

three dimensional simulation of scour inducing flow at bridge piers presently available formulas for estimating the maximum depth of scour near bridge piers often lead to unreliable results a fully three dimensional hydrodynamic model is therefore used in this study to simulate the flow occurring at the base of a cylindrical bridge pier within a scour hole the results of the numerical simulation are compared with laboratory observations by melville and raudkivi 1977 quantitative and qualitative agreement between the studies is quite good discrepancies between the results of the two studies are of an order that may be attributed to choices in numerical model parameters the simulations may be supplemented by lagrangian particle tracking to estimate the depth of the equilibrium scour condition

optical dating of young coastal dunes on a decadal time scale we explore the use of quartz optically stimulated luminescence osl dating for reconstructing coastal evolution on a time scale of decades to a few hundred years samples are taken from the accretionary south west coast of texel a barrier island just offshore of the northern netherlands the ages of dune ridges are known from historical sources an excellent chronology with a decadal accuracy exists for the past 260 years osl ages of less than 10 years on the youngest samples indicate that the osl signal of the quartz grains is very well zeroed prior to deposition and burial osl ages of five samples from a 250 year old dune ridge are indistinguishable and the osl ages on 17 out of 20 samples are in excellent agreement with the well known independent age controls our results highlight the potential of osl dating for high resolution reconstruction of coastal evolution over the past few centuries

late holocene inland dune activity in the uk a case study from breckland east anglia inland dune fields found in breckland east anglia uk have previously been correlated with the widespread late devensian coversands of the region and a seventeenth century sandflood which is known to have inundated the village of santon downham a programme of optically stimulated luminescence and radiocarbon dating undertaken on the dunes at wangford warren and santon downham reveals that episodic aeolian activity has taken place during the last 7000 years five sand depositional phases on breckland dunes are identified c 6500 c 1600 1100 c 500 c 400 335 and from c 200 30 years before present between c 2120 1840 years ago and within the period 1100 300 years ago quiescent periods allowed the development of fen peat and soils local controlling factors on aeolian activity in breckland appear to be related to anthropogenic activities and livestock sheep and rabbits reducing vegetation cover and decreased precipitation and sea levels which led to lowering of water tables breckland aeolian activity when compared to the national and sub continental holocene aeolian activity record shows a high level of concordance the underlying forcing factor for late holocene dune activity in the uk and elsewhere in europe appears to be climatic instability in the north atlantic associated with both the little ice age and previous similar events which led to increased storminess climatic variability and lower temperatures

sea level controls on carbonate beaches and coastal dunes eolianite lessons from pleistocene bermuda 2015 geological society of america coastal dune accumulations at locations around the world have formed during sea level highstands rising sea levels falling sea levels and fluctuating sea levels initially episodes of maximum pleistocene dune activity in bermuda which is the type location for eolianite were correlated with glacio eustatic regressions this model had been abandoned by the 1970s in favor of a rising sea level model for bermuda s north shore and autogenic sediment supply model for the south shore we report the results of a detailed investigation of the intercalated mid late pleistocene beach and coastal dune deposits on the islands of bermuda and we test the existing models for these deposits we contend that the north shore model is invalidated by past misidentification of eoliandeposits as transgressive beach deposits on the south shore facies analysis of the marine isotope stage 7 mis 7 belmont formation reveals that coastal deposition was divided into two phases s1 which includes foreshore and shoreface progradation is predominantly marine and coincided with rising relative sea level s2 which commenced with protosol development on top of the marine section prior to burial by advancing dunes is nonmarine we conclude that the two successions s1 and s2 resulted from forcing by glacio hydro isostatic relative sea level change spanning a highstand rising and then falling rather than from transgressive or autogenic processes the finding that in bermuda the construction of protective coastal dunes depends on a falling relative sea level has potential implications for many vulnerable shorelines that face rising relative sea levels associated with climate change

numerical modeling of abutment scour with the focus on the incipient motion on sloping beds a three dimensional computational fluid dynamics model is applied to predict local scour around an abutment in a rectangular laboratory flume when modeling local scour steep bed slopes up to the angle of repose occur to predict the depth and the shape of the local scour correctly the reduction of the critical shear stress due to the sloping bed must be taken into account the focus of this study is to investigate different formulas for the threshold of noncohesive sediment motion on sloping beds some formulas only take the transversal angle perpendicular to the flow direction into account but others also consider the longitudinal angle streamwise direction the numerical model solves the transient reynolds averaged navier stokes equations in all three dimensions to compute the water flow sediment continuity in combination with an empirical formula is used to capture the bed load transport and the resulting bed changes when the sloping bed exceeds the angle of repose the bed slope is corrected with a sand slide algorithm the results from the numerical simulations are compared with data from physical experiments the reduction of the bed shear stress on the sloping bed improves the results of the numerical simulation distinctly the best results are obtained with the formulas that use both the transversal and the longitudinal angle for the reduction of the critical bed shear stress

numerical investigation of flow and scour around a vertical circular cylinder flow and scour around a vertical cylinder exposed to current are investigated by using a three dimensional numerical model based on incompressible reynolds averaged navier stokes equations the mod

quantification and implications of change in organic carbon bearing coastal dune cliffs a multiscale analysis from the northumberland coast uk eroding coastlines composed of sequences of till carbon rich peat and sand layers are characteristic of many formerly glaciated coastlines due to the interplay of relative land and sea levels dune cliffs cut into these materials represent one of the most sensitive systems to the processes of coastal change establishing appropriate scales for the quantification and analysis of change in coastal dune cliffs remains limited by the speed and nature of change the intensity of environmental processes and the challenges of achieving adequate survey control this paper presents the results from multi scale analyses into the behaviour of dune cliffs on the northeast coast uk over a 118 year period repeat unmanned aerial vehicle uav survey differences have been used to identify and quantify system behaviour set in context with historic map comparisons at the landform scale monthly dune cliff dynamics have been analysed over the course of a year with terrestrial laser scanning tls in order to gain insights into the drivers of contemporary dune cliff behaviour finally pseudo three dimensional ground penetrating radar gpr data are used to trace subsurface stratigraphy from which the potential extent of stored carbon in excess of 100 t over 50 m of monitored dune cliff at risk of release by coastal erosion over the next 50 years can be calculated the consideration of multi scale changes over time periods relevant to well constrained sea level change has revealed a complex combination of failure mechanisms that have resulted in an acceleration in dune cliff recession particularly over the last decade and a form change to shallower divergent profiles this potential acceleration in contemporary dune cliff response holds significant implications for both coastal management and the contribution of this poorly quantified input to the coastal carbon flux

the late holocene coastal dunefield at vejers denmark characteristics sand budget and depositional dynamics abstract the coastal dunefield at vejers west coast of jutland which is now stabilized by vegetation covers an area of approximately 120 km 2 and occurs in a very high energy wind regime along the coastline a narrow belt of 5 15 m high dune ridges occur the dune ridges are gradually replaced inland by 10 20 m high parabolic or irregular dune forms in the central part of the dunefield a large aeolian sand plain ca 50 km 2 occurs at the windward side of a large and up to 20 m high parabolic dune the 3d structure of the dunefield deposits have been studied by geomorphological analysis sedimentological facies analysis of borings trenches and natural exposures and most importantly by georadar mapping the aeolian deposits which overlie a middle to late holocene barrier spit depositional system can be divided into a lower unit that drapes the underlying barrier system topography and an upper unit that includes the present dunes the boundary between the two aeolian units is a well developed phragmites peat the lower aeolian unit is composed of two aeolian subunits separated by an organic rich horizon also the upper unit is composite and composed of a basal aeolian sand cover and overlying dune or sand plain deposits the dune deposits locally are composed of up to four depositional subunits separated by immature soils the base of the lower aeolian unit formed around 300 a d whereas the phragmites peat at the base of the upper aeolian unit has been dated to ca 1000 a d from historical sources we know that the present dunefield primarily formed between 1550 and 1850 a d the sand content in the upper unit is estimated to 550 10 6 m 3 which yields sand transport rates between 25 m 3 m width 1 yr 1 accumulation in 1000 years and 83 m 3 m width 1 yr 1 accumulation in 300 years the sand in the dunefield originated from beach deposits a large but pulsating supply of sand was supplied to the beaches by southwards running coastal currents the composition of the vejers dunefield deposits indicate that periods of dunefield growth alternated with periods of dunefield stabilization during the last ca 1700 years the final and most important phase of dunefield growth took place during the little ice age this period was characterized by an overall cold and stormy climate and a relative low sea level and resulted in an increased availability of sand in the shorezone and a high influx of sand into the dunefield short periods of decreased storminess are recorded by the immature soils dunefield growth prior to 1000 a d was also linked to cold and stormy climatic intervals

evolution of a large baltic beach ridge plain neudarss ne germany a continuous record of sea level and wind field variation since the homeric minimum

three dimensional numerical modelling of wave induced scour around piles in a side by side arrangement abstract the paper presents the numerical modelling of wave induced scour around piles in a side by side arrangement using the open source cfd model reef3d the model solves the reynolds averaged navier stokes equations to calculate wave hydrodynamics the turbulence under the wave action is calculated using the k model the free surface is captured with the level set method the simulated flow field is coupled with the morphological module in reef3d to simulate the scouring process the morphological evolution of the sediment bed is based on the exner formula for a more realistic calculation of bed scouring and deposition the modified critical bed shear stress on a sloping bed together with a sand slide algorithm is implemented in the morphological model first the model is tested for numerical modelling of wave induced scour around a single pile the study presents wave generation and the scouring process in a full sized and a reduced length numerical wave tank nwt using the relaxation and the active wave absorption method furthermore a discussion on the partial temporal decoupling for the time scales of the morphological and the hydrodynamic models is made the simulated result shows that the fully developed waves and resulting scouring can be modelled in a reduced length nwt with the same quality as seen for a full sized nwt the validated model is then used to simulate the wave induced scour around piles in a side by side arrangement the capacity of the model to simulate wave induced scour in the gap between two piles along with the free surface is demonstrated the results show the variation of the normalised maximum scour depth s d with the gap ratios g d and the keulegan carpenter number the formation of the jet effect between the piles with different g d values is also discussed

holocene shoreline displacement on the gungnam plain buyeo near the central west coast of south korea inferred from diatom assemblages abstract diatom analyses of core gn 2 and trench tr 1 taken from gungnam plain on the lower reach of geum river are conducted to verify the holocene shoreline displacement near the central west coast of south korea age controlled diatom profiles of gn 2 and tr 1 record the history in responses of depositional environments to changes in sea level four diatom zones in gn 2 and two in tr 1 were established during zone i ca 8400 6500 bp in tr 1 and ca 7100 6800 bp in gn 1 the depositional environment was an inner bay to a mud tidal flat from 6800 to 4300 bp zone ii of gn 1 and tr 1 the former environments were replaced by brackish conditions with sediments deposited under a sea level high stand zone ii also contains reworked sediments resulting from a temporary drop in sea level between 4300 bp and 400 bp middle to upper part of zone iii of gn 1 there were stable freshwater environments with few diatoms after sea level fluctuations finally during zone iv 400 bp present the depositional environments changed to freshwater marshlands the multi proxy data reflect the tendency of sea level variations in the gungnam plain from 8410 to 4330 bp around 8400 bp the sea level reached an elevation of 1 14 m a s l due to an early holocene transgression overall the sea level around the gungnam plain continued to rise from ca 8400 to 6500 bp although there was a temporary drop between 6800 bp and 6500 bp at present the spring tide has a range of 6 64 m mean tide level 3 32 m in kunsan harbor and local flood tides the mean sea level in the gungnam plain about 6500 bp may have reached an elevation of 3 40 m a s l corresponding to or slightly higher than the present sea level

three dimensional calculation of scour around cylinders the flow of water around a cylinder was calculated by a numerical model the model used a finite volume method to solve the nontransient navier stokes equations for three dimensions on a general nonorthogonal grid the k e turbulence model was used to solve the reynolds stress term the flow field gave the shear stress on the boundaries which was used to calculate sediment concentration for the bed elements the diffusion convection equation for the sediment concentration was solved and continuity for the sediment concentration gave changes in the bed elevation using the modified bed a new flow field was calculated and also a new sediment concentration this sequence was repeated until the depth of the calculated scour hole was identical to the depth of the scour hole from a physical model study the rest of the geometry of the resulting scour hole compared well with the measured scour hole from the experimental study also other flow characteristics given by the numerical model were found to be in ag

numerical simulation of contraction scour in an open laboratory channel a finite volume computer code developed at the institute for hydromechanics university of karlsruhe has been used to calculate the flow and sediment transport in a laboratory channel with constriction and movable bed the flow is calculated by solving the fully three dimensional reynolds averaged navier stokes equations with k e turbulence model the bed deformation is obtained from an overall mass balance equation for sediment transport and the bed load transport is simulated with a nonequilibrium model the calculated results for flow and scour development in the laboratory channel are compared with experimental measurements the sensitivity of the simulated results to the nonequilibrian adaptation length parameter in the nonequilibrium bed load transport model is investigated systematically which represents the main contribution of this paper

numerical simulation of scour and backfilling processes around a circular pile in waves abstract this study continues the investigation of flow and scour around a vertical pile reported by roulund et al 2005 flow and scour backfilling around a vertical pile exposed to waves are investigated by using a three dimensional numerical model based on incompressible reynolds averaged navier stokes equations the model incorporates 1 k turbulence closure 2 vortex shedding processes 3 sediment transport both bed and suspended load as well as 4 bed morphology the numerical simulations are carried out for a selected set of test conditions of the laboratory experiments of sumer et al 1997 2013a and the numerical results are compared with those of the latter experiments the simulations are carried out for two kinds of beds rigid bed and sediment bed the rigid bed simulations indicate that the vortex shedding for waves around the pile occurs in a one cell fashion with a uniform shedding frequency over the height of the cylinder unlike the case for steady current where a two cell structure prevails the rigid bed simulations further show that the horseshoe vortex flow also undergoes substantial changes in waves the amplification of the bed shear stress around the pile including the areas under the horseshoe vortex and the lee wake region is obtained for various values of the keulegan carpenter number the principal parameter governing the flow around the pile in waves the present model incorporated with the morphology component is applied to several scenarios of scour and backfilling around a pile exposed to waves in the backfilling simulations the initial scour hole is generated either by a steady current or by waves the present simulations indicate that the scour and backfilling in waves are solely governed by the lee wake flow in agreement with observations the numerical model has proven successful in predicting the backfilling of scour holes exposed to waves the results of the numerical tests indicate that the equilibrium depth of scour holes is the same for both the scour and the backfilling for a given keulegan carpenter number in full agreement with observations

holocene sea level and climate interactions on wet dune slack evolution in sw portugal a model for future scenarios we examine the holocene environmental changes in a wet dune slack of the portuguese coast poco do barbarroxa de baixo lithology organic matter biological proxies and high resolution chronology

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

late holocene sand invasion and north atlantic storminess along the aquitaine coast southwest france holocene forested coastal dunes of different morphology fringe the atlantic coast of southwest aquitaine infra red stimulated luminescence irsl dating has been applied to sands from these dunes in the aquitaine region in order to test the validity of dune classification theories the ages obtained from the dunes show three phases of sand invasion and dune development during the late holocene 3000 4000 years ago 900 1300 years ago 250 550 years ago the timing of the most recent phase of sand mobilization as dated by irsl is supported by historical maps and records from the fifteenth to the eighteenth centuries ad showing problems for human settlement in the region and village abandonment due to dune drift sand invasion is driven by an increase in frequency of severe storms in the north atlantic associated with the cooler periods of the little ice age and early mediaeval warm period the dunes emplaced 900 1300 years ago were naturally fixed by a mixed deciduous and maritime pine forest durin

conceptualization and scale in hydrology abstract it is argued that the levels of scale at which a meaningful conceptualization of physical processes is possible are not arbitrary and their range is not continuous formulations appropriate at a given level usually are not applicable at the immediately adjoining levels this is seen as one of the important reasons for the slow progress of hydrological science on basin scale since it is dominated by different effects than those observed at the immediately lower level of channel reaches and hillslopes which represent the focus of current hydrological research the search for an appropriate level of conceptualization can proceed either upward or downward along the hierarchy of scales both possibilities are discussed and an example of the downward route is given

sand incursion into temperate lithuania and tropical the bahamas maritime vegetation georadar visualization of target rich aeolian lithosomes abstract interaction of windblown sand with maritime vegetation either as dune migration or episodic grain transport is a common phenomenon along many sandy coasts vegetation introduces antecedent surface roughness especially when scaled to the landform height but its role may be concealed if overwhelmed by aeolian incursion and burial where field observations and cores lack detail for characterizing this complex process ground penetrating radar gpr offers continuous visualization of aeolian sequences along the curonian spit lithuania dune reactivation phases resulted in massive invasion of siliciclastic sand triggered by natural perturbations and land clearance massive 30 m high dunes entombed mature pine oak and alder stands and this process is ongoing mid frequency 200 mhz georadar surveys reveal landward dipping lateral accretion surfaces interrupted by high amplitude point source anomalies produced by recently buried trees in tropical regions dense vegetation and potential for rapid lithification of carbonate sand results in more complex internal structures along the windward coast of san salvador island the bahamas a massive dune has buried several generations of maritime scrubland resulting in highly chaotic reflection pattern and high target density on a nearby little exuma island numerous reentrants in aeolianites promoted formation of blowouts and incursion of windblown sand 10 25 m into a silver thatch palm forest high frequency 800 mhz gpr images resolve diffractions from trunks and roots buried by 2 m of oolitic sand basal refection morphology helps differentiate the irregular dune beachrock surface from a smooth palm frond mat aside from detecting and mapping buried vegetation geophysical images capture its effect on sediment accumulation this has the potential for differentiating its effect from other discordant structures within dunes clasts dissolution voids trunk molds burrows and cultural remains

living with sand a record of landscape change and storminess during the bronze and iron ages orkney scotland abstract palaeoenvironmental analyses of an exposed sequence of interbedded sand and peat overlying glacial till on stronsay orkney has revealed evidence of dynamic landscape change during the holocene ams radiocarbon and osl dating are used to identify periods of minerogenic and organic sediment accumulation a lengthy period of stability during the early holocene is inferred from the development of a deeply weathered till surface with pollen and soil micromorphological evidence suggesting prolonged woodland cover during the mid to late holocene phases of wind blown sand that inundated the landscape are defined from the sedimentary record and are interpreted as periods of increased storminess between c 3400 3100 cal bp and c 2800 2260 cal bp the palaeoecological evidence points to continuity of human exploitation despite the phases of increased storminess during the bronze age and into the iron age rising sea levels and a severe storm event at c 650 years bp inundated the site with massive sands and truncated the record these storm events recorded on stronsay are part of a regionally synchronous record for periods of increased storminess across the north atlantic region during the holocene

on the generation of delayed peaks in stream discharge abstract where deep permeable soils overlie impermeable bedrock and where steep hillslopes border a narrow floodplain subsurface stormflow dominates the hydrograph in such cases delayed peaks in stream discharge may occur several days after rainfall providing the major volumetric response and possibly also the highest peak discharge the general occurrence of such delayed peaks is considered making reference to field data from two small drainage basins in southwest england and to the results of computer simulations using a distributed hillslope model the importance of soil water convergence into hillslope hollows is stressed the relative roles of rainfall and antecedent soil moisture in controlling the size and timing of the delayed peak is discussed the implications of the results for hillslope runoff modelling are briefly considered

lumped hysteretic model for subsurface stormflow developed using downward approach the terms downward and upward synonymous with top down and bottom up respectively are sometimes used when describing methods for developing hydrological models a downward approach is used here to develop a lumped catchment scale model for subsurface stormflow at the 0 94 km2 slapton wood catchment during the development as few assumptions as possible are made about the behaviour of subsurface stormflow at the catchment scale and no assumptions are made about its behaviour at smaller scales in an upward approach in contrast the modelling would be based on assumptions about and data for the behaviour at smaller scales such as the hillslope plot and point scales the model has a single store with a relatively simple relationship between discharge and storage based on equations describing hysteretic patterns seen in a graph of discharge against storage double peaked hydrographs have been observed at the catchment outlet rainfall on the channel and infiltration excess and saturation excess runoff give a rapid response and shallow subsurface stormflow gives a delayed response hydrographs are successfully simulated for the large delayed responses observed in 1971 1980 and 1989 1991 then a lumped model for the rapid response is coupled to the lumped hysteretic model and some double peaked hydrographs simulated a physical interpretation is developed for the lumped hysteretic model making use of information on patterns of perched saturation observed in 1982 on a hillslope at the slapton wood catchment downward and upward approaches are complementary and the most robust way to develop and improve lumped catchment models is to iterate between downward and upward steps possible next steps are described copyright 2006 john wiley sons ltd

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

application of luminescence dating and geomorphological analysis to the study of landscape evolution settlement and climate change on the channel island of herm abstract the optically stimulated luminescence osl dating of sands and palaeosol horizons sampled as part of an archaeological investigation and supported by geomorphological analysis has been applied to identify critical stages in the development of the landscape on herm one of the channel islands that lies off the coast of guernsey on which megalithic monuments were constructed during the neolithic period in particular there were three phases of significant aeolian activity during the prehistoric period the onsets dated by osl in this study to ca 4 3 and 2 3 ka ago where the first phase marked a significant change in the long term trend of aggradation of soils that persisted during the next two millennia osl ages were also obtained for palaeosols in which there was evidence of ploughing placing this activity in the late 2nd millennium bc and the 4th and 13th centuries ad the osl ages for basal deposits of dune sands that cover the northern part of the island indicate that they were formed by phases of intense aeolian activity during the medieval period commencing in the 13th century ad and continuing for several hundred years which can be correlated with documented high intensity storms in the north atlantic within the period 13th 15th centuries ad the phases of significant aeolian activity dated by osl to ca 4 and 2 ka ago can be linked with those detected in different regions of the north atlantic coastal areas the availability of chronologies for aeolian horizons provides a valuable tool in the study of the evolution of coastal landscape and how past coastal communities responded to climate change

controlling mechanism of local scouring experimental study of clear water scouring around a circular cylinder shows that the scour mechanism is coupled to the three dimensional separation of the upstream boundary layer and the periodic vortex shedding in the wake of the cylinder the first scour appears in the wake of the cylinder the main scouring agent in the upstream region is a system of horseshoe vortices the vortices have a periodical character that causes a triple scour profile to develop in the upstream region during scouring the number and periods of horseshoe vortex shedding undergo no appreciable change despite the clear water stage the transport phenomenon is periodical transport of sediment takes place through turbulent scales of comparable size to macro length scales the size of horseshoe vortices are representative for the macroscale wake scouring is caused by the primary wake vortices and the accelerated side flow the process is characterized by a strong periodical transport and the formation of ripples the periodicity is controlled by the shedding frequency of the wake vortices collars attached to the cylinder cannot prevent the formation of the vortices

building of shore oblique transverse dune ridges revealed by ground penetrating radar and optical dating over the last 500 years on tottori coast japan sea abstract coastal dunes provide valuable information on the past aeolian activity better characterization of internal dune structures and their chronology potentially can greatly improve the interpretation of past environmental changes ground penetrating radar gpr and optically stimulated luminescence osl dating was applied to two transverse dune ridges which are arranged obliquely to the shoreline on the tottori coast japan sea data shows that the inner ridge has a core of pleistocene dune draped with holocene sand while the outer ridge consists only of holocene sand the holocene dune is generally dominated by landward migration but the outer ridge shows a clear seaward accretion during the 18th century ad osl dating showed concordant results with radar stratigraphy and topographic changes since ad 1932 revealed by maps from this we were able to present the first detailed report of the multi decadal to centennial scale dune formation for the last 500 years in east asia contemporaneous with the little ice age during which many european coastal and inland dunes were activated in east asia it is thought that the winter monsoon plays an important role for aeolian processes the seaward migration during the 18th century reflects a decrease in wind capacity which restricted sand transport nearshore being related to decline in winter monsoon revealed by chinese historical documents in contrast two remarkable events of landward accretion occurred in ad 1580 1640 and around ad 1840 respectively corresponding to periods of increased dust fall in china which suggest enhanced winter monsoon the zone of maximum sedimentation shifted through time from the inner to outer ridges and also towards the seaward end of the shore oblique dune ridge reflecting an expansion of the dune field caused by shoreline progradation these suggest that the effective combination of gpr and osl dating was critical in detailed characterization of the complicated depositional pattern of the transverse dune ridge and thus in reconstruction of the past aeolian activity

storminess variation during the last 6500 years as reconstructed from an ombrotrophic peat bog in halland southwest sweden cores taken from an ombrotrophic peat bog in the coastal zone of halland southwest sweden were examined for wind transported mineral grains pollen and humidity indicators the core covers the period from 6500 cal yr bp to present ombrotrophic conditions existed from ca 4200 cal yr bp onwards bog surface wetness fluctuated strongly until ca 3700 cal yr bp with an apparent dominance of dry summer conditions from 4800 4500 cal yr bp local wet shifts occurred around 4300 2800 2400 and 1500 cal yr bp whereas the most recent 600 years of the record show increasingly dry conditions mineral grain content interpreted as aeolian sand influx asi was used as a proxy for winter storm frequency and intensity until ca 1500 cal yr bp after which increasing human impact as reconstructed by pollen analysis became a second important potential cause for increased sand drift strongly increased storminess occurred at 4800 4200 2800 2200 1500 1100 and 400 50 cal yr bp indicating a dominance of cold and stormy winters during these periods many of these storm periods apparently coincide with storm events in other sites in southwestern scandinavia suggesting that our asi record reflects a regional scale climatic signal furthermore these stormy periods correlate to well known cold phases in the north atlantic region suggesting a link to large scale fluctuations in atmospheric circulation patterns less

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

development and age structure of holocene coastal sand dunes at horn head near dunfanaghy co donegal ireland two areas of holocene coastal sand dunes on the western side of the horn head peninsula extend from low ground immediately inland of their respective source beaches onto flanking higher ground 100 m od stratigraphic investigations supported by 14c dating of buried organic rich horizons and shells demonstrate several phases of sand accumulation in the pollaguill croaghadara system in contrast to the larger tramore anloge hill system where the available evidence points to relatively recent dune emplacement a broadly synchronous phase of dune development occurred during the thirteenth to fourteenth centuries ad and is viewed as part of a regional northwestern europe dune building episode resulting from climatic deterio ration earlier phases pre 3300 2800 14c years bp of aeolian sand deposition at pollaguill croaghadara have no apparent equivalents at tramore anloge hill and repeated fluvial incision and sand reworking during the last 2000 14c years is also evident at the former site dated organi

flow pathways in the slapton wood catchment using temperature as a tracer summary this study investigates the potential of temperature as a tracer to provide insights into flow pathways the approach couples fieldwork and modelling experiments for the eastergrounds hollow within the slapton wood catchment south devon uk measurements in the eastergrounds hollow were carried out for soil temperature spring temperature and the stream temperature and use was made of an existing 1989 1991 data set for the entire slapton wood catchment the predominant flow in this hollow is a result of subsurface stormflow and previous work has suggested that the water flows vertically down through the soil and then subsurface stormflow occurs at the soil bedrock interface where the water is deflected laterally the depth of the subsurface stormflow was previously thought to be around 2 2 m however analysis of the new spring stream and soil temperature data suggests a deeper pathway for the subsurface stormflow modelling of water flow and heat transport was carried out using shetran and this was calibrated to reproduce the water flow in the entire slapton wood catchment and soil temperatures in the eastergrounds hollow the model was tested for the entire eastergrounds hollow with two different soil depths a depth of 2 2 m based on previous knowledge was unable to reproduce the eastergrounds spring temperature a depth of 3 7 m produced an excellent comparison between measured and simulated stream and spring temperatures in the eastergrounds hollow this work suggests that the depth of the flow pathways that produce the subsurface stormflow are deeper than previously thought it also provides a demonstration on the use of temperature as a tracer to understand flow pathways

negatively skewed aeolian sands from a humid tropical coastal dunefield northern australia abstract this paper describes the nature and environmental significance of variations in textural parameters within a large coastal dunefield in tropical northern australia grain size parameters of modern beaches and foredunes are very similar but are distinct from those of parabolic dune and sandplain environments on average beach and foredune sands have a normal grain size distribution but parabolic dune sands are predominantly negatively skewed negative skewness is interpreted as primarily reflecting sorting of dune sediments by winnowing at dune crests and by avalanching on slip faces a general relationship between mean size and skewness is supported with finer sediments showing increased negative skewness positive skewness can therefore not be used as a diagnostic property of aeolian sediments

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

baseflow recession and recharge as nonlinear storage processes discharge in many rivers is often fed by outflow from a shallow groundwater reservoir it is becoming clear that the outflow from this aquifer is not linearly proportional to storage as is commonly assumed in many algorithms numerical analysis of flow recession curves from about 100 river gauging stations instead reveals a nonlinear relationship between baseflow q and storage s for which the equation s aqb was adopted values of the exponent b are found by calibration to be between 0 and 1 but with a high concentration around 0 5 which is in accordance with the findings of other studies and theoretical approaches yielding b 0 5 for unconfined aquifers and relating the coefficient a to catchment properties primarily area and shape of basin pore volume and transmissivity this non linear reservoir function is proposed as a more realistic alternative to the linear reservoir function the relatively fast response of groundwater flow to rainfall is mainly a result of the increase of hydraulic head of the groundwater reservoir accelerating the exfiltration of old pre event water into the river bed as fissure and pore volumes communicate hydraulically it appears physically reasonable to model the system by one non linear reservoir for catchments or parts of them instead of applying independent parallel linear reservoirs the non linear reservoir algorithms are supported by an analytical derivation they are extended for the automatic separation of baseflow from a time series of daily discharge in rivers and the computation of storage and effective recharge of groundwater in river basins by inverse nonlinear reservoir routing the time series obtained allow the identification and quantification of long term changes to the water balance relationships between computed groundwater storage and observed groundwater level can also be established copyright 1999 john wiley sons ltd

aeolian sand movement and relative sea level rise in ho bugt western denmark during the little ice age this study documents an extensive aeolian sand sheet buried in the salt marshes of the ho bugt embayment in western denmark the extent of the sand sheet was mapped from c 60 cores and sections which were also used to reconstruct late holocene changes in relative sea level based on diatom analyses chronology was provided by optically stimulated luminescence osl and radiocarbon dating our study shows that since 2000 cal yr bp relative sea level in ho bugt has risen by approximately 1 5 m the overall rise was punctuated by two periods with higher than average rates of sea level rise the first between 2000 and 1400 cal yr bp and the second commencing c 500 cal yr bp around 700 cal yr bp the evolution of the skallingen spit may have been responsible for a reduction in the local tidal range and the formation of an extensive black layer in the western part of the embayment osl analyses date the sand sheet to between ad 1460 40 and ad 1550 30 490 40 and 400 30 cal yr bp consistent wi

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

mid to late holocene coastal dune event stratigraphy for the north coast of northern ireland an event stratigraphy of dune stability instability phases has been reconstructed using 22 radiocarbon and 13 luminescence dates for six dunefields along the north coast of northern ireland there is no evidence for dune development prior to 7000 cal years bp during the early holocene rapid rise in rsl and only limited evidence for sand accumulation in association with the rsl maximum dunefield dates correspond to either the subsequent regressive phase or later the gradual transgressive phase of rsl history in the mid and late holocene at these times accommodation space for dune development and sediment supply were maximized episodes of climatic deterioration particularly at 3100 2400 cal years bp and 650 50 cal years bp the little ice age were marked by widespread dune instability a similar coincidence in timing has been recorded for dune systems elsewhere in northwestern europe and is generally attributed to an increased frequency of storms and storm surges associated with the climat

experimental and numerical investigation of local scour around a submerged vertical circular cylinder in steady currents abstract local scour around a submerged vertical circular cylinder in steady currents was studied both experimentally and numerically the physical experiments were conducted for two different cylinder diameters with a range of cylinder height to diameter ratios transient scour depth at the stagnation point upstream edge of the cylinder was measured using the so called conductivity scour probes three dimensional 3d seabed topography around each model cylinder was measured using a laser profiler the effect of the height to diameter ratio on the scour depth was investigated the experimental results show that the scour depth at the stagnation point is independent on cylinder height to diameter ratio when the later is smaller than 2 the increase rate of equilibrium scour depth with cylinder height increases with an increase in shields parameter a three dimensional finite element numerical model is developed for simulating local scour around submerged vertical cylinders steady flow around the cylinder is simulated by solving the reynolds averaged navier stokes rans equations with a k turbulence closure both suspended load and bed load sediment transport rates were included in the model efforts are made to reduce the computational time associated with three dimensional morphological modelling including the use of wall function to avoid resolving the near wall boundary layers large morphological time step and parallel computing techniques scour around a submerged vertical circular cylinder founded on the seabed is simulated and the numerical results are validated against the test data the scour mechanisms around the submerged cylinder are investigated using the numerical model

osl based lateral progradation and aeolian sediment accumulation rates for the apalachicola barrier island complex north gulf of mexico florida article i nfo vertical sediment cores in five separate beach ridge complexes along the north east gulf of mexico coast were recovered and dated using optically stimulated luminescence osl dating of quartz these are located on cape san blas csb little st george island lsgi richardson s hammock rh st joseph peninsula sjp and saint vincent island svi all of these landforms are coastal barrier systems situated along a 100 km stretch of the florida panhandle u s a two samples were collected for dating from each core ridge accumulation rates rar associated with lateral progradation were calculated from the dated samples we also determined average sediment accumulation rates asar for two intervals within each sediment core all osl ages within the sediment cores were found to be in stratigraphic order or in a few cases statistically indistinguishable moreover all dated ridges were found to be in correct temporal sequence based on their geomorphic positions rapidly accreted sequences were found to be backed by st joseph bay in the western region of the study area more slowly accreted sequences were associated with the more eastern stretches of the study area backed by st vincent sound and apalachicola bay our asar results are in accord with an australian study of modern dune accumulation perhaps our most important finding is that in the barrier island environments of this north eastern gulf coast region aeolian sedimentation continues well after full vegetative cover develops and stranding of landward ridges takes place this confirms our similar earlier observation on svi lopez and rink 2008 we find that up to approximately one order of magnitude lower sedimentation rates occur after an initial period of more rapid aeolian accumulation for the vertical intervals studied in foredune ridges lateral progradation rates of ridge sequences were highly variable within the study area ranging from 92 to 848 m 100 years but we did find agreement between some of our slower ridge accumulation rates and those in other areas of florida and around the world determined using osl and 14 c dating we conclude that osl may be used in a regional context to establish variation in progradation rates and aeolian accumulation that varies among systems

luminescence dating of holocene sedimentary deposits on romo a barrier island in the wadden sea denmark this study presents an optically stimulated luminescence osl based chronology for the evolution of the barrier island romo and related back barrier lagoon deposits in the danish wadden sea the chronology is constructed using 78 quartz osl ages obtained using a single aliquot regenerative dose sar protocol samples were retrieved from seven sediment cores each up to 25 m long taken from locations on the island and within the back barrier lagoon the reliability of the osl results is assessed using preheat plateaus thermal transfer tests and dose recovery measurements and by comparison with independent age control the osl ages compare favourably with three 14c age estimates and range between 220 20 and 15 800 1200 years romo appears to have developed as a progradational barrier system and the island appeared for the first time approximately 8000 years ago it then gradually expanded towards the west north and south as a result of an abundant sediment supply luminescence dating is concluded t

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

episodic coastal dune development in the taean peninsula and anmyeon island korea during the mid to late holocene the episodic nature of coastal dune development has been widely identified in many dune areas over the world what causes such episodicity is still hotly debated sea level change climatic change and human impact have widely been reported as the main forcings though there is no agreement yet upon which factors are critical this research provides some evidence that sea level fluctuation and climatic factors controlled the episodic dune building together based upon optically stimulated luminescence osl dune ages on the west coast of korea the newly obtained and published osl dune ages on the west coast of the taean peninsula and anmyeon island korea indicate the six main periods of dune building 5 5 4 3 1 5 1 3 1 1 and 0 7 ka they correlate with evidence of colder climate in east asia that imply stronger dune forming winds during the winter under the influence of a more intense siberian high they also correlate with periods of higher sea level over the present one with fluctuations thus episodic dune activity along the west coast of the korean peninsula during the mid to late holocene appears to be linked to stronger winter winds capable of moving sand from the beach to the foredune ridges with short term fluctuations during the high stands copyright 2009 john wiley sons ltd

the termination of the last major phase of aeolian sand movement coastal dunefields denmark optically stimulated luminescence osl dating of sand samples from stabilized or inactive coastal dunes in denmark provides information on the age of the termination phase of the last major aeolian activity period a total of 26 sand samples were taken from four different coastal dunefields around the north sea skagerrak and kattegat coasts of denmark the osl dates indicate that the last major phase of aeolian activity terminated between ad 1860 and 1905 most of the dunes examined in this study were active around 1820 during a period documented to have been very stormy a dune management scheme started around 1792 and this no doubt was a major cause of dunefield stabilization but an overall decline of storminess particularly spring and summer storminess around the end of the 19th century must also have contributed to the increasing inactivity of coastal dunes the new osl dates on aeolian sand movement agree well with historical data and data from topographic maps on dune movement this agreement supports the observation from earlier work that osl dating of recent aeolian sand movement is accurate over the last few decades to centuries copyright 2005 john wiley sons ltd

complexity of holocene climate as reconstructed from a greenland ice core glaciochemical time series developed from summit greenland indicate that the chemical composition of the atmosphere was dynamic during the holocene epoch concentrations of sea salt and terrestrial dusts increased in summit snow during the periods 0 to 600 2400 to 3100 5000 to 6100 7800 to 8800 and more than 11 300 years ago the most recent increase and also the most abrupt coincides with the little ice age these changes imply that either the north polar vortex expanded or the meridional air flow intensified during these periods and that temperatures in the mid to high northern latitudes were potentially the coldest since the younger dryas event

luminescence dating applications in geomorphological research abstract chronological control remains critical to the interpretation of environmental change and to establishing long term rates of geomorphological processes radiocarbon dating will continue to be the central technique for age assessment of carbon bearing sediments deposited in the last ca 40 ka but alternative absolute dating strategies are required for older or non carbon bearing sediments they include uranium series dating of precipitated sediments k ar and ar ar dating of primary volcanic materials and cosmogenic isotopic dating of surface exposure ages an additional family of methods collectively termed luminescence techniques is increasingly providing a basis for the age assessment of detrital sedimentary deposits these methods directly date the deposition of detrital mineral grains typically quartz and feldspar and have been demonstrated to provide accurate deposition chronologies for up to 800 ka although 150 ka is more typical in the past decade a subset of luminescence techniques which employ optical sample stimulation methods called optical dating has made it possible to date samples from a much wider range of depositional systems given that the methods directly date sedimentation they allow direct assessment of depositional dynamism in numerous terrestrial and subaqueous including marine sedimentary systems and have demonstrated particular potential in the elucidation of chronologies from aeolian dune and loess fluvial colluvial coastal and volcaniclastic environments this paper provides a summary of the principles of the luminescence especially optical dating methods and shows how recent developments specifically single aliquot dating procedures have dramatically enhanced the scope and potential of the method the luminescence techniques are increasingly being incorporated into a wide range of geomorphological studies which seek to establish the nature of landscape changes over the past interglacial glacial cycle and beyond

storage outflow modelling of streamflow recessions with application to a shallow soil forested catchment abstract the objectives of this study were to introduce an alternative to the matching strip correlation and parameter averaging methods for deriving master recession characteristics from a set of recession segments and to apply the method to streamflow recession segments for a small forested catchment in which baseflow is provided by drainage of the saturated zone in the shallow permeable soil the method involves fitting conceptual storage outflow models using an iterative algorithm diagnostic plots revealed that the recessions were non linear and that the recessions did not follow a common single valued storage outflow relation a model involving two linear reservoirs provided substantially better fit than three single reservoir models indicating that the form of the recession curve probably depends not just on the volume of subsurface storage but also on its initial distribution amongst reservoirs

numerical and experimental investigation of flow and scour around a half buried sphere abstract the paper describes the results of a numerical and experimental investigation of flow and scour around a half buried sphere exposed to a steady current hot film bed shear stress and laser doppler anemometer measurements were made with a half sphere mounted on the smooth bed in an open channel the hydrodynamic model is a 3 d general purpose n s flow solver the k omega sst turbulence model was used for closure the flow model was used to study the horseshoe vortex and lee wake vortex flow processes around the sphere the flow model was coupled with a morphologic model to calculate scour around the half buried sphere in currents the morphologic model includes a sediment transport description and a description of surface layer sand slides for bed slopes exceeding the angle of repose the sediment transport description includes for the first time the effect of externally generated turbulence induced by the horseshoe vortex flow and the lee wake flow processes on sediment transport the results show that the scour depth increases and time scale decreases when the effect of externally generated turbulence is incorporated in the calculations empirical expressions representing the numerically obtained data on the equilibrium scour depth and the time scale are presented the results show that the equilibrium maximum scour depth in the live bed regime can be approximated by 0 5 d in which d is the sphere diameter

flow field complexity and design estimation of pier scour depth sixty years since laursen and toch abstractthis paper written to celebrate the 60th anniversary of the journal of hydraulic engineering presents a structured contemporary approach to scour depth estimation that matches design met

effects of storminess sand supply and the north atlantic oscillation on sand invasion and coastal dune accretion in western portugal holocene forested coastal dunes fringe the atlantic coast of western portugal mapping of dunes in the field and using air photographs shows a range of forms reflecting dominant northwest and westerly onshore wind regimes planting of maritime pine forests in the thirteenth and twentieth centuries was initiated because of sand invasion causing problems for human settlement and agriculture early holocene dunes have a well developed podsol and date to 9 7 and 8 2 ka suggesting at least some of these sands may have been emplaced during a global cooling event significant transgressive dune accretion at 2 2 and 1 5 ka implies abundant sand supply and strong onshore winds the most recent dune building period dates to ad 1770 1905 and coincides with a predominantly negative winter north atlantic oscillation index naoi accretion of dunes along the portuguese coast appears out of phase with dune development in southwest france which may reflect different atlantic storm tracks driven by changes in the domin

holocene coastal change and geoarchaeology at howick northumberland uk the recent discovery of one of the earliest mesolithic occupation sites in northern britain at howick on the northumberland coast in association with multiperiod archaeological evidence nearby highlights the importance of uk coastal settings as focii of human occupation through the holocene environmental evidence from a nearby river valley 8 15 m of sediment ranging in age from about 12 000 cal bp to the present records local and regional environmental change twenty four radiocarbon dates based on plant macrofossils provide a strong chronological framework calcareous microfossil assemblages foraminifera ostracods have been recovered from the fine grained sediments recording a change from marine through to brackish and eventually freshwater conditions between about 8200 and 6500 cal bp a preliminary pollen study of the core has permitted a reconstruction of the regional vegetation as it responded to climatic amelioration and human influence upon the landscape radiocarbon dating and sedimentological evidence indicates a major hiatus between approximately 11 000 and 8000 years bp including the period of mesolithic occupation represented by a 30 cm layer of coarse sands and sandstone pebbles probably the result of a significant high energy event dated to about 8300 cal bp although not a typical tsunami deposit the age and context suggests that this may be associated with the storegga slide event already well documented along the eastern coast of scotland the sedimentary and biological remains at howick record environmental change over much of the holocene and are compared with other environmental change records from the region to provide an environmental framework for the archaeology of this coastline

decadal changes in north atlantic atmospheric circulation patterns recorded by sand spits since 1800 ce abstract present day coastal barriers represent around 15 of the world s oceanic shorelines and play an important role as early warning indicators of environmental change among them wave dominated barriers are dynamic landforms that tend to migrate landward in response to storms and sea level change high rates of sediment supply can locally offset the global retrogradation trend providing valuable records of past environmental change occurring on transgressive coasts however geochronological control limits the temporal resolution of such records to millennial or centennial timescales and the decadal or even faster response of wave built barriers to historical climate changes is therefore poorly understood in this study we show that shoreline dynamics of sand spits reconstructed from old cartographic documents has been synchronous on both margins of the north atlantic ocean since about 1800 ce spit growth accelerated drastically during three periods lasting about 15 years characterised by positive north atlantic oscillation nao and negative east atlantic west russia ea wr atmospheric circulation patterns these changes are in phase with periods of increased volcanic activity we use a high resolution wave hindcast 1948 2014 ce in a reference area to confirm the association between nao and ea wr as a proxy for offshore and nearshore wave height and for associated longshore sediment transport lst involved in spit growth a 24 month lagged correlation between sediment transport and volcanic aerosol optical thickness concentration of ashes in the atmosphere is observed suggesting that spit shoreline dynamics at the decadal timescale is partially forced by external climate drivers via cascading effects on atmospheric circulation patterns and wave climate our results imply that nao variability alone is not sufficient to understand the evolution of wave built coastal environments the associated sediment record can be used to reconstruct multi decadal variability of other climate patterns

vortex shedding and morphodynamic response of bed surfaces containing non erodible roughness elements abstract a series of wind tunnel experiments was carried out to investigate particle entrainment from surfaces in which one or more roughness elements were embedded thin sand strips were employed to eliminate impact and ejection and thus isolate entrainment by fluid drag the pattern of erosion is consistent with the presence of coherent vortices inclusive of trailing vortices in the wake flow the shape and orientation of the roughness element strongly influence this pattern when an upwind supply of saltators is introduced the majority of particles within the bed are entrained through impact with the exception of a sand tail to the lee of the roughness element that is the effect of coherent structures within the airflow as related to spatial variation in the fluid drag exerted on the bed surface is completely overprinted by the saltation cloud and the blocking of particle trajectories by the upwind face of the roughness element in a repeated set of experiments the bed was allowed to fully adjust its morphology to the transport system in this case particle entrainment did not selectively occur within the zone of wake flow and by inference the fluid stress across the test surface appeared to be uniform these experiments support the hypothesis that vortex annihilation occurs on morphodynamically adjusted surfaces in summary the system response to the emergence of non erodible roughness elements on surfaces affected by wind erosion involves a suite of geophysical processes each of which attains varied levels of dominance within a given morphodynamic domain

scour around coastal structures a summary of recent research abstract this paper summarizes the results of the european union marine science and technology eu mast iii project scour around coastal structures scarcost the summary is presented under three headings 1 introduction 2 flow and scour processes with the subheadings flow and scour processes around vertical cylinders flow and scour processes at detached breakwaters flow and scour processes at submerged breakwaters and the effect of turbulence on sediment transport and 3 sediment behaviour close to the structure with the subheadings field measurement and analysis of wave induced pore pressures and effective stresses around a bottom seated cylinder non linear soil modelling with respect to wave induced pore pressures and gradients wave induced pressures on the bottom for non linear coastal waves including also wave kinematics development of a numerical model linear soil modelling to calculate wave induced pore pressures the effect of liquefaction on sediment transport penetration of blocks in non consolidated fine soil and cyclic stiffness of loose sand the paper also includes a discussion of the role of scale effects in laboratory testing and the applicability of the results obtained in supporting engineering design

assessment of temporal changes in coastal sand dune environments using the log hyperbolic grain size method three cores 9 m long recovered from late holocene coastal sand dunes in northumberland north eastern england were examined stratigraphically and dated by the infrared stimulated luminescence irsl method to the time period between the medieval warm period mwp 900 1200 ad and little ice age lia 1550 1800 ad grain size variability and caco 3 content were determined at 10 mm intervals throughout parts of the cores the sahara computer program was used to plot the log hyperbolic distribution lhd of grain size spectra from different stratigraphic levels and estimate the lhd s statistical components core samples plot variously in the depositional and erosional domains of the hyperbolic chi vs xi shape triangle which describes components of sediment sorting depositional and erosional phases discriminated within the lhd s shape triangle cannot readily be resolved from core stratigraphies or correlated between cores irsl dates from single cores show a clustering about the period 1430 1540 between the dated horizons dunes accreted at 0 02 0 05 m year 1 enabling the timing of excursions in and to be estimated these excursions which can be resolved to the subannual level between the dated horizons may be related to deposition by episodic storms or storm surges in the north sea region which is supported by historical documentary evidence this innovative use of the lhd method and its derived statistics can be used successfully to describe temporal trends in coastal depositional environments and identify likely storm events in dune sediment records

reconstruction of holocene coastal foredune progradation using luminescence dating an example from the świna barrier southern baltic sea nw poland abstract two sandy spits on the wina barrier wolin and uznam provide a very detailed succession of holocene coastal foredunes and dunes and are regarded as key sites along the southern baltic sea coast optically stimulated luminescence osl dating is proven to be a powerful tool for the reconstruction of holocene coastal spit evolution and foredune accretion quartz extracted from the coastal sediments in the study area provides excellent properties for osl dating the osl age from the innermost dune indicates that spit development of the wina barrier started immediately after rapid sea level rise of the littorina transgression decelerated at 6 6 ka a significant change in the foredune progradation rate occurred during the late subatlantic transgression at 1 2 ka 800 ad when migration rates decreased from 2 6 0 7 m a 1 to 1 3 0 4 m a 1 progradation accelerated again during the little ice age between 1550 and 1850 ad the systematic dating of 28 samples reveals six hiatuses during foredune succession at 2100 bc 900 bc 200 bc 200 ad 600 ad 1000 ad and 1600 ad the timing of these hiatuses correlates with the phases of transgressive dune development in the surrounding area troszyn and wina and with phases of increased aeolian activity in other parts of north and west europe we conclude that four of these phases of foredune erosion instability and aeolian sediment mobilisation were caused by general climate shifts to cooler and stormier conditions at 2200 bc 900 bc 600 ad and at 1600 ad the latter corresponding to the little ice age the period of increased aeolian activity around 1000 ad is probably to a phase of intensive forest clearance in central europe in contrast the systematic foredune accretion and foredune plain growth correlates to periods of positive sediment budget milder and calmer climate and an intact vegetation cover

a new windstorm proxy from lake sediments a comparison of geological and meteorological data from western germany for the period 1965 2001 1 the feasibility of detecting windstorm layers in lake sediments is explored by comparing quartz grain size data from a freeze core obtained from the schalkenmehrener maar eifel region western germany to recent meteorological wind data the schalkenmehrener maar is appropriate for such a calibration study because the morphological settings of the lake allow the conservation of windstorm layers in particular there is no fluvial sediment inflow and long term wind measurements are available from nearby stations the age model for the uppermost 30 cm of the sediment core is based on measurements of 137cs and 210pb concentrations an ultra high resolution grain size analysis is performed digitally on thin sections and reveals distinct 1 mm thick layers with increased quartz grain content and sharp gaussian grain size distributions which are shifted to larger grain sizes compared to the normal lake sediment in order to compare the occurrence of these layers with meteorological wind data a windstorm index is developed combining data from meteorological stations in the eifel region and reanalyses from the european centre for medium range weather forecast a statistical evaluation of matches between the windstorm index and the core s silt fraction data indicates that the sediment layers very likely coincide with the major windstorm events in the eifel region during the last decades six historical storm are identified this pilot study identifies the main requirements and proposes a novel methodological approach for using sediment data from lakes with similar settings as the schalkenmehrener maar as a new proxy to reconstruct the windstorm record of the geological past

optically stimulated luminescence dating of late holocene raised strandplain sequences adjacent to lakes michigan and superior upper peninsula michigan usa this study evaluates the accuracy of optically stimulated luminescence to date well preserved strandline sequences at manistique thompson bay lake michigan and tahquamenon and grand traverse bays lake superior that span the past 4500 yr the single aliquot regeneration sar method is applied to produce absolute ages for littoral and eolian sediments sar ages are compared against ams and conventional 14 c ages on swale organics modern littoral and eolian sediments yield sar ages b100 yr indicating near if not complete solar resetting of luminescence prior to deposition beach ridges that yield sar ages b2000 yr show general agreement with corresponding 14 c ages on swale organics significant variability in 14 c ages n2000 cal yr b p complicates comparison to sar ages at all sites however a sar age of 4280 f 390 yr uic913 on ridge77 at tahquamenon bay is consistent with regional regression from the high lake level of the nipissing ii phase ca 4500 cal yr b p sar ages indicate a decrease in ridge formation rate after 1500 yr ago likely reflecting separation of lake superior from lakes huron and michigan this study shows that sar is a credible alternative to 14 c methods for dating littoral and eolian landforms in great lakes and other coastal strandplains where 14 c methods prove problematic

mid holocene sea level highstand along the southeast coast of china various sea level curves have been proposed for the coast of china in the past two decades these sea level curves indicate a complex history of holocene sea level and so the debate on whether or not a higher mid holocene sea level highstand exists in the coast of china has continued this paper aims to re examine the holocene sea level history for the low latitude part of the china coast between 18 n and 32 n by re assessing all the sea level data available from the east to south coasts and separating them according to geological settings in order to examine the influences of global and local factors the reconstructed sea level histories from different coastal sectors of the china coast reveal a certain degree of variability in the timing and height of mid holocene sea level highstand within large river deltas the mid holocene sea level highstand occurred earlier by almost 1000 years than that from other coastal sites the highstand from large river deltas appears also lower in altitude a few metres below the present day sea level due probably to the local factors of subsidence and sediment consolidation in geologically stable coastal sites the highstand is recorded at the same altitude as the present day sea level a 1 2 m higher highstand is found from sites where tectonic uplift is observed

late holocene coastal sand movements in the outer hebrides n w scotland lithostratigraphical and biostratigraphical investigation of coastal marshes along the atlantic coast of the outer hebrides from lewis in the north to barra in the south discloses inland tapering sand units within marshland areas the inland extent of each sand unit has been radiometrically dated and the units have been collectively interpreted as a proxy for past coastal storminess the data appear to indicate that for the study sites investigated the majority of the sand units were produced during episodes of climate deterioration both prior to and after the well known period of medieval warmth mwp many were produced after ca ad 1400 it is argued that the episodes of sand blow indicated by the deposits may reflect periods of increased cyclogenesis in the atlantic associated with increased sea ice cover and an increase in the thermal gradient across the north atlantic region

numerical modeling of flow and scour at pipelines a numerical model for the description of fluid flow and suspended and bed load sediment transport is presented density effects are included in the momentum reynolds equations and in the turbulence kappa and epsilon equations changes in bed levels are calculated from sediment continuity and the finite element grid is adapted to the geometry the reynolds equations and the transport equation for suspended sediment are solved numerically using a taylor galerkin finite element method the flow at a surface mounted cylinder in a steady flow is predicted in good agreement with experiments periodic vortex shedding from a cylinder placed above a rigid bed is predicted in good agreement with laboratory experiments provided that sufficiently detailed grids approximately 5 000 nodes are used scour calculations are performed for a cylinder in a steady flow with its underside placed at the level of the original flat bed predicted scour at a pipeline in steady flow is in good agreement with laboratory measurements reported in the literature

intense storm activity during the little ice age on the french mediterranean coast understanding long term variability in the frequency of intense storm activity is important for assessing whether changes are controlled by climate evolution understanding this variability is also important for predicting present and future community vulnerability and economic loss our ability to make these assessments has been limited by the short less than 50 years instrument record of storm activity storm induced deposits preserved in the sediments of coastal lagoons offer the opportunity to study the links between climatic conditions and storm activity on longer timescales in this study we present a record of these extreme climatic events that have occurred in the french mediterrannean coast over the past 1500 years the identification of these extreme events is based on the analysis of sediment cores from gulf of aigues mortes lagoons that contain a specific sedimentary and geochemical signature associated with intense storms overwash deposits do not show any evidence of intense storm landfalls in the region for several hundred years prior to the late 17th century a d the apparent increase in intense storms around 250 years ago occurs during the latter half of the little ice age a time of lower continental surface temperatures comparison of the sediment record with palaeoclimate records indicates that this variability was probably modulated by atmospheric dynamics the apparent increase of the superstorm activity during the latter half of the little ice age was probably due to the thermal gradient increase leading to enhanced lower tropospheric baroclinicity over a large central atlantic european domain and leading to a modification of the occurrence of extreme wind events along the french mediterranean coast a complete understanding of the relationship between climate fluctuations storm activity and the coastal response will be crucial to predicting the impacts of future climate change