organic geochemistry in a sequence stratigraphic framework the siliciclastic shelf environment of cretaceous series se france for a better understanding of siliciclastic shelf environments correlation between sequence stratigraphy and organic geochemistry is used our study is focused on the cretaceous deposits of marcoule gard france particularly on a close packed siltites layer 200 400 m thick which is well characterized as a marine flooding facies of a single trangressive regressive cycle during the uppermost albian and the lower cenomanian the stratigraphic data indicate a change in the depositional environment from offshore to shoreface organic geochemistry is used in order to characterize origin and variability of the organic matter in relation to the stratigraphic data the study is carried out on core samples from 2 drill holes mar 203 and mar 501 analyses of the aliphatic and aromatic hydrocarbons were performed using gc ms and focused on biomarker distributions the biomarkers indicate a contribution of mixed terrestrial and marine organic matter the changes in molecular signatures are related to variations in the source of organic matter marine versus terrestrial preservation conditions largely influenced by clay and early diagenesis environmental oxidation reduction and acidic conditions as well as bioturbation various environmental zones characterized by different molecular signatures can be distinguished resin derived biomarkers can be assigned to higher plant material input and may reflect the evolution and diversity of gymnospermae versus angiospermae during the transgressive regressive cycle the relative sea level variations are clearly correlated with the nature and the preservation of the organic matter for example the pr ph and pr n c 17 ratios as well as the regular steranes distributions underline the maximum flooding surface evidenced by other studies we observe a good correlation between the organic data and sequence stratigraphy changes in geochemical signatures reflect the 3rd order depositional cycles

an experimental model of episodic gas release through fracture of fluid confined within a pressurized elastic reservoir we present new experiments that identify a mechanism for episodic release of gas from a pressurized deformable reservoir confined by a clay seal as a result of the transition from bulk deformation to channel growth through the clay air is injected into the center of a thin cylindrical cell initially filled with a mixture of bentonite clay and water for sufficiently dry mixtures the pressure initially increases with little volume change on reaching the yield stress of the clay water mixture the lid of the cell then deforms elastically and an air filled void forms in the center of the cell as the clay is driven radially outward with continued supply of air the pressure continues to increase until reaching the fracture strength of the clay a fracture like channel then forms and migrates to the outer edge of the cell enabling the air to escape the pressure then falls and the clay flows back toward the center of the cell and seals the channel so the cycle can repeat the phenomena may be relevant at mud volcanoes

pollen taphonomy of cave sediments what does the pollen record in caves tell us about external environments and how do we assess its reliability cave sediments may contain important long term records of past environments and human activity pollen provides key evidence since it disperses widely and is relatively durable we still know relatively little about the dispersal of pollen into caves and its preservation within cave sediments compared with our relatively detailed knowledge of pollen taphonomy in other sedimentary environments pollen taphonomy in caves is dependent on a variety of transport pathways and seems to be very contingent on local circumstance the airfall component of cave pollen assemblages often seems comparable with airfall spectra in the landscape outside the cave but bees birds and bats may transport considerable quantities of pollen into caves and the entrance flora may also be significant cave sediments are rarely waterlogged and pollen within them can be subject tomicrobial and chemical degradation sedimentation in caves is often episodic with episodes of storage and deposition sometimes redeposition of sediment which means that biostratinomic preservational factors become very significant comparison with sequences outside caves is difficult because few caves are found in landscapes where there are comparable pollen records from lakes and bogs here we review the factors affecting cave pollen taphonomy and hence the reliability of palynological analysis of sediments from caves with suggestions for future investigation

reconstructing past climates using carbon isotopes from fulvic acids in cave sediments little is known about the potential of organic substances found within cave sediments to provide useful reconstructions of past climatic changes here we present a study of the carbon isotopes of fulvic acids extracted from sediments from a cave in west central florida fulvic acids are the most contemporaneous representation of soil humic substances derived from vegetation growing above the cave radiocarbon dating of these sediments constrains their depositional period to be late holocene the range of the fulvic acid 13c record shows the dominance of c3 vegetation during this period but with changes in abundance and the shifting presence of c4 plants the 13c values record both the little ice age and medieval climate anomaly which produce drier and wetter conditions for florida respectively our conclusion that the stable carbon isotopic values of the cave sediment record as a proxy for vegetation change as driven by variability in precipitation is strongly supported by a comparison with the 13c and 18o values of two uranium series dated speleothems from this part of florida with both being proxies for precipitation change

stress dependent permeability of a de mineralised fracture in shale abstract the paper presents the results of laboratory direct shear tests on the hydro mechanical behaviour of an extensional fracture in shale the tests were conducted on fracture specimens obtained by mechanically splitting blocks of a naturally fractured shale along the cemented fracture and dissolving the calcite fracture filling with a strong acid the experiments consisted of radial fluid flow tests from a single fluid source along the fracture surface fracture samples were tested under different levels of effective normal stress and shear displacement the experimental results show significant reduction of fracture permeability during increasing contact normal stress across the fracture and after shearing of the fracture under constant high normal stress however the tested fractures never completely closed even under normal stresses close to or higher than the unconfined compressive strength of the intact shale the fracture permeability remained much higher than the intact shale or matrix permeability even when the fracture surface has undergone some gouge formation from local asperity failure during shearing the results indicate that fractures once created are difficult to close by mechanical loading in tight formations like shales fractures will always be conduits for fluid flow unless closed by cementation currently it is widely assumed that fractures in sedimentary basins stay open only when there is an overpressure which could keep the fractures hydraulically parted however the results presented here indicate that given a sufficient hydraulic gradient fluid can still flow along a fracture even in the absence of large overpressures

modelling of localised gas preferential pathways in claystone a long term injection gas test on initially saturated claystone samples under isotropic confining pressure is modelled in a 2d hydro mechanical framework which includes the hydraulic anisotropy evidences of localised pathways through the sample have been observed experimentally which are difficult to reconcile with standard two phase flow models the presence of an embedded pre existing fracture is included in a continuum finite element model a hydro mechanical coupling between the fracture aperture permeability and the retention properties along the fracture is included in the model due to the increase in permeability and the decrease of the air entry pressure induced by the rise in fluid pressure at constant mean total stress the model provides good agreement with the experimental observations the discussion offers additional insight into the fluid flow mechanisms into the sample and the processes involved in the development of localised gas pathways this study allows conclusions to be drawn regarding the performance of the model and its practical limitations

seismic investigation of the excavation damaged zone in opalinus clay a mini sonic borehole probe was used to investigate the excavation damaged zone edz around an underground opening in the opalinus clay in the mont terri rock laboratory in switzerland the edz could be determined by using seismic parameters as interval velocities and amplitudes of first arrivals derived from measurements in eight radial drilled boreholes the extent of the edz is about 1 m but varies between 0 6 and 2 2 m

sediment distribution dispersal and budget in the yellow sea abstract information on the surface sediment distribution in the yellow sea is newly compiled based on all available data produced by chinese and korean workers and is used to refine the dispersal patterns and budget of sediments derived from the adjoining landmass the central yellow sea is largely covered with fine grained sediments originating from the huanghe river 2 2 10 8 t yr about 20 of the total discharge thick sediment accumulation exceeding 5 mm yr occurs in the gulf of bohai and around the shandong peninsula about two thirds of the total huanghe river discharge the old huanghe delta suffers from reworking by strong tides and waves and forms a mud patch southwest of cheju island accumulation rate 2 10 7 t yr more than half of the sediments derived from the changjiang river are deposited along the coast of the east china sea the remainder accumulate on the inner shelf off the river mouth in the southeastern yellow sea the keum river dominates sediment discharge forming a holocene mud belt along the southwestern coast of korea accumulation rate 5 10 6 t yr turbid water plumes occur nearshore throughout the year and their suspended sediments are transported along the tip of the peninsula to the western coastal embayments in the south sea the nakdong river discharge of 1 10 7 t yr is responsible for the eastern nearshore mud of the south sea relict sands occur in the northern part of the yellow sea in the northern east china sea and in the korea strait

monitoring of helium and carbon isotopes in the western eger rift area czech republic relationships with the 2014 seismic activity and indications for recent 2000 2016 magmatic unrest abstract we report new data of the regional distribution pattern of total gas compositions as well as he and co2 isotopic compositions from 25 gas exhalations in the western eger rift and its surroundings additionally the first time series data from gas exhalations in a clay pit within the cheb basin cb are given at 21 degassing locations the first data were obtained 20 years ago from 7 locations within the degassing center cb and from 3 degassing sites belonging to the marianske lazn ml degassing center neon and argon isotope compositions were determined also co2 is the major component at all degassing sites the 13c values display a small range 1 7 to 5 1 and the 3he 4he ratios vary from 1 9 to 5 9 ra the highest 3he 4he ratios are found at locations along the pocatky plesna fault zone followed by the degassing site in the clay pit on the nova ves fault and the locations on the ml fault at the edge of the cb although gas flow and co2 concentrations in all degassing centers are very high the fractions of mantle derived helium are different with presently up to 94 in relation to the sclm 3he 4he of 6 32 ra in the cb up to 73 in the ml and up to 35 in the karlovy vary degassing center at the locations in the eastern part of the cb a clear progressive increase of the 3he 4he ratio has been observed since the first sampling campaigns there in 1993 and 1994 whereas at the other degassing sites the helium isotope ratio remained essentially the same the progressive increase of the 3he 4he ratio in the eastern part of the cb together with further short time increases up to 6 3 ra at one location bublak before both the 2000 and 2008 earthquake swarms indicate an ongoing magmatic process beneath this area which seems to be associated with the occurrence of seismicity the cb is located close to the nov kostel focal zone where since the beginning of our investigations four strong periods of seismicity with magnitudes 3 occurred the latest gas data confirm our earlier findings time series studies showed that in relation with seismic events decreased 3he 4he ratios were repeatedly observed due to admixed seismically released crustal helium presently the eastern part of the cb is the most active non volcanic region in the european cenozoic rift system with gas signatures similar to those found in free mantle derived gases from the east african rift system

gas transport properties through intact and fractured callovo oxfordian mudstones a series of controlled water and gas experiments was undertaken on samples of callovo oxfordian cox mudstone using a synthetic fluid and helium gas data from this study demonstrate that the advective movement of gas through cox is accompanied by dilation of the original fabric i e the formation of pressure induced microfissures at gas pressures significantly below that of the minimum principal stress flow occurs through a local network of unstable pathways the properties of which vary temporally and spatially within the mudstone the coupling of variables results in the development of significant time dependent effects affecting many aspects of cox behaviour from the gas breakthrough time to the control of deformation processes variations in gas entry breakthrough and steady state pressures may result from the arbitrary nature of the flow pathways and or microstructural heterogeneity under these conditions the data suggest that gas flow is along pressure induced preferential pathways where permeability is a dependent variable related to the number width and aperture distributions of these features this has important implications for modelling gas migration through low permeability clay rich materials

the fate of repository gases forge project understanding the behaviour of gases in the context of radioactive waste disposal is a fundamental requirement and was the focus of the forge fate of repository gases project of particular importance is the long term performance of the bentonite buffers and the cement based backfill materials that may be used to encapsulate and surround the waste in a repository for the geological disposal of radioactive waste and plastic clays indurated mudrocks and the crystalline formations that may be the host rocks of a repository forge did not study salt host rocks or salt based backfill materials forge has provided new insights into the processes and mechanisms governing gas generation and migration with the aim of reducing uncertainty relating to the quantitative treatment of gas in performance assessment this has been achieved by the acquisition of new experimental data coupled with modelling through a series of laboratory and field scale experiments performed at a number of underground research laboratories throughout europe and modelling new methods were developed for upscaling from laboratory to field conditions allowing the optimization of disposal concepts through detailed scenario analysis understanding a repository system to an adequate level of detail is required to demonstrate confidence in the assessment of site performance recognizing that a robust treatment of uncertainty is desirable throughout this process

gas migration through water saturated bentonite sand mixtures cox argillite and their interfaces france s deep seated nuclear waste repository consists of a natural barrier located at a depth of 500 m in a callovo oxfordian clayey formation this repository has artificial barriers that include

hydrologic issues associated with nuclear waste repositories significant progress in hydrology especially in subsurface flow and solute transport has been made over the last 35 years because of sustained interest in underground nuclear waste repositories the present paper provides an overview of the key hydrologic issues involved and to highlight advances in their understanding and treatment because of these efforts the focus is not on the development of radioactive waste repositories and their safety assessment but instead on the advances in hydrologic science that have emerged from such studies work and results associated with three rock types which are being considered to host the repositories are reviewed with a different emphasis for each rock type the first rock type is fractured crystalline rock for which the discussion will be mainly on flow and transport in saturated fractured rock the second rock type is unsaturated tuff for which the emphasis will be on flow from the shallow subsurface through the unsaturated zone to the repository the third rock type is clay rich formations whose permeability is very low in an undisturbed state in this case the emphasis will be on hydrologic issues that arise from mechanical and thermal disturbances i e on the relevant coupled thermo hydro mechanical processes the extensive research results especially those from multiyear large scale underground research laboratory investigations represent a rich body of information and data that can form the basis for further development in the related areas of hydrologic research

an unsaturated hydro mechanical modelling of two in situ experiments in callovo oxfordian argillite abstract the unsaturated behaviour of callovo oxfordian argillite is investigated through the modelling of 2 in situ experiments the first test studies the influence of ventilation in a gallery on the hydro mechanical behaviour of the rock mass the second test consists in a gas injection in the rock mass from an experimental borehole a hydro mechanical model is described and used in the modelling of the experiments a review of the main hydro mechanical parameters of argillite is presented the numerical results highlight the need of a flow boundary condition reproducing the fluid transfers between the surroundings and the rock mass the influence of dissolved gas on the compressibility of the liquid phase is also emphasised

tracing of variabilities within a geological barrier by molecular organic geochemistry case of the callovo oxfordian sedimentary series in the east of the paris basin france abstract the callovo oxfordian claystones located at 500 m depth at bure meuse france are currently being investigated by andra the french national radioactive waste management agency for testing the feasibility of long term and deep geological nuclear waste disposal in order to evaluate its potential as a geological barrier it is very important to study assess and describe its physico chemical variability the molecular biomarker composition of 150 samples of these claystones and their surrounding limestones carry diverse information on the sources of the sedimentary organic matter the chemistry of the depositional environment the preservation and diagenesis conditions it also allows assessing the degree of lateral and vertical variability of the organic matter within these sedimentary series the abundance of unsaturated biomarkers the distribution of steroids and hopanoids and cpi values 2 prove the thermal immaturity of the organic matter the co occurrence of plankton bacteria and land plant biomarkers indicate that the organic matter is a mixture of marine and continental contributions the data also reveal that the organic matter was deposited under oxic and open sea conditions except for a brief event of photic zone anoxia at the beginning of the middle callovian in the claystones the geosynthesis of diasterenes is favored to the detriment of the formation of steranes especially in smectite rich levels and the organic matter is rapidly isolated from oxidizing then reducing conditions after the deposition due to the protective effect of clays on the scale investigated the claystones are characterized by a unique molecular facies and are thus homogenous from their organic content point of view yet detailed investigation of specific molecular families indicates changes related to major claystone limestone transitions the homogeneity of these claystones can be explained by the paleogeographic position of their depositional setting and the plane and sub horizontal paleotopography on which they were deposited this study demonstrates the efficiency of organic geochemistry in the assessment of the variability of geological barriers

determination of permeability for hydrocarbon release due to excavation induced stress redistribution in rock salt abstract due to a stress redistribution after the excavation of an underground tunnel for radioactive waste disposal an ed dz excavation disturbed damaged zone will be generated in the near field of the opening resulting in significant changes in the hydraulic and mechanical properties of the rock mass in the zone initially more or less randomly distributed hydrocarbons at grain boundaries in rock salt which sometimes can only be observed with ultraviolet light can then be mobilised and migrate at a potentially significant rate towards the excavation within the international cooperative project decovalex 2019 the migration mechanism of such fluid inclusions in rock salt is being studied intensively a multi scale modelling strategy has been developed a macroscale coupled hydro mechanical modelling of an underground excavation was performed to determine hydraulic and time dependent deviatoric stress conditions by taking into account the rock salt creep behaviour under the obtained macro scale constraints micro scale modelling of a pathway dilation along halite grain boundaries was performed using different model strategies a coupled hydromechanical modelling with a consideration of hydraulic pressure induced dilatant deformation b nonlinear dynamic model taking account of fluid migration stress dependent grain boundary wetting and shear induced dilatancy of salt and c phase field modelling of flow pathway propagation the permeability increase resulting from the pathway dilation is estimated to be as high as two orders of magnitude based on the permeability determined a series of pressure build ups measured from a borehole with a high hydrocarbon release rate a total of 430 build ups within a monitoring time of 938 days can be simulated with a macro scale compressible flow model accounting for different zones around the opening

gas flow through clay barriers a model for the simulation of gas flow in clayey rocks and clays is described gas migration is associated with the development of preferential paths along existing or pressure dependent discontinu

quantitative estimation of intertidal sediment characteristics using remote sensing and gis abstract high spatial resolution satellite data ikonos combined with in situ data was used to quantitatively estimate the spatial distribution of tidal flat characteristics for the hwangdo tidal flat cheonsu bay korea the classification result was accurate in terms of a comparison with the in situ data and the overall accuracy was 90 7 which confirmed the validity of the classification gis analysis based on a probabilistic model was applied to a quantitative estimation of the relationship between each surface sediment facies and the spectral reflectance mud flat facies showed a high positive correlation r 2 0 91 and sand flat facies showed a high negative correlation r 2 1 00 which was a good reflection of the sedimentary characteristics of hwangdo tidal flat relationships between each sediment facies and dem also showed good agreement with the topographic characteristics in the study area the study revealed that intertidal surface sediment classification using high resolution remote sensing imagery and in situ data successfully shows spectral and topographic characteristics of the study area it was noted that spectral reflectance was affected by a combination of environmental factors including grain size topography and remnant surface water it is possible to determine the type of tidal flat through quantitative estimates of the spatial distribution of surface sediments according to their spectral reflectance

a preliminary sediment budget for the winyah bay estuary south carolina usa abstract winyah bay a 65 km2 coastal plain estuary in south carolina has an average freshwater input of 557 m3 s 1 and presently receives 0 43 106 t yr 1 of suspended sediments from its watershed corresponding to a yield of 12 7 t km 2 yr 1 however 20 dams have been constructed on the upper rivers primarily on the yadkin and pee dee rivers which serve to capture an additional 0 40 106 t yr 1 of sediment implying a gross sediment yield of 24 5 t km2 yr 1 for the watershed although almost 50 never reaches the coast continuous dredging in the estuarine channels removes 0 107 106 t yr 1 of silt and clay from the estuary sediment coring and 210 pb analysis indicate that the sedimentation rate in mud bay a high accretion area in the lower estuary is 5 5 mm yr 1 which together with previous estimates of marsh sedimentation rates of 2 7 mm yr 1 in the tidal marshes surrounding the estuary leads to a total estuarine mud sedimentation estimate of 0 24 106 t yr 1 thus 80 of the fine grained sediment reaching winyah bay is either accumulating in adjacent marshes or on estuarine mud flats or is being dredged and deposited offshore although these budget calculations need further confirmation by direct measurements and additional coring winyah bay apparently delivers only a minimal amount of suspended fine grained sediments to the coastal ocean

filling the gaps late upper palaeolithic settlement in gvardjilas klde georgia abstract the paper presents the newly established radiocarbon dates of the late upper palaeolithic lup settlement in gvardjilas klde in the imereti region in georgia the analysed samples were collected by stefan krukowski in 1916 during his fieldwork in the cave krukowski identified two separate up cultural horizons the older one was connected with what he called layer 10 and the younger one with layer 11 the obtained radiocarbon dates confirm the results obtained by krukowski the older settlement phase can be dated to 19 7 18 8 ky cal bp while the younger one to 15 8 14 7 ky cal bp the end of human occupation can be linked to the beginning of the holocene interestingly the presented probability density models show that gvardjilas klde was occupied interchangeably with other sites in the region there is no other site in the imereti region with chronology similar to any of the settlement phases in gvardjilas klde the only chronologically corresponding sites are mezmaiskaya cave and badynoko rockshelter in the northern caucasus

semi automated procedures for shoreline extraction using single radarsat 1 sar image coastline identification is important for surveying and mapping reasons coastline serves as the basic point of reference and is used on nautical charts for navigation purposes its delineation has become crucial and more important in the wake of the many recent earthquakes and tsunamis resulting in complete change and redraw of some shorelines in a tropical country like malaysia presence of cloud cover hinders the application of optical remote sensing data in this study a semi automated technique and procedures are presented for shoreline delineation from radarsat 1 image a scene of radarsat 1 satellite image was processed using enhanced filtering technique to identify and extract the shoreline coast of kuala terengganu malaysia radsarsat image has many advantages over the optical data because of its ability to penetrate cloud cover and its night sensing capabilities at first speckles were removed from the image by using lee sigma filter which was used to reduce random noise and to enhance the image and discriminate the boundary between land and water the results showed an accurate and improved extraction and delineation of the entire coastline of kuala terrenganu the study demonstrated the reliability of the image averaging filter in reducing random noise over the sea surface especially near the shoreline it enhanced land water boundary differentiation enabling better delineation of the shoreline overall the developed techniques showed the potential of radar imagery for accurate shoreline mapping and will be useful for monitoring shoreline changes during high and low tides as well as shoreline erosion in a tropical country like malaysia

preparation and characterization of bone and tooth collagen for isotopic analysis abstract criteria are presented for the identification of diagenetic alteration of carbon and nitrogen isotope ratios of bone and tooth collagen prepared by a widely used method measurements of collagen concentrations in tooth and bone atomic c n ratios and carbon and nitrogen concentrations in collagen of 359 historic and prehistoric african humans and modern and prehistoric east african non human mammals are described carbon isotope ratios of collagen lipids from four bones are also presented compared to bone whole teeth have significantly lower collagen concentrations lower carbon and nitrogen concentrations in collagen and similar c n ratios carbon and nitrogen concentrations and c n ratios are relatively constant over a wide range of collagen concentrations however prehistoric specimens with very low collagen concentrations have highly variable c n ratios very low carbon and nitrogen concentrations in collagen and stable carbon and nitrogen isotope ratios unlike collagen at the transition from well preserved to poorly preserved collagen the most reliable indicator of collagen preservation is the concentration of carbon and nitrogen in collagen concentrations of c and n drop abruptly by an order of magnitude at this transition point these attributes provide simple criteria for assessing sample quality since collagen preservation can vary greatly within prehistoric sites these attributes should be reported for each specimen use of purification procedures that remove acid and base soluble contaminants and particulate matter carbonates fulvic acids lipids humic acids sediments and rootlets are recommended wider adoption of these procedures would insure comparability of results between laboratories and permit independent and objective evaluation of sample preservation and more precise dietary climatic and habitat interpretations of collagen isotopic analyses

comparative investigation of the spatial distribution of past weathering impacts on sandstone masonry abstract inspection of the deterioration of both natural outcrops and historical built stone facades reveals that patterns of disruption are not uniform indicating the influence of material and environmental properties sandstones have a spatial variability in weathering response for this reason geostatistical techniques have been applied to studies of sandstone properties mineralogical and structural that influence susceptibility to decay for this study a comparative analysis of permeability data acquired from a quarry fresh stone and a weathered sample is undertaken the depositional processes that resulted in the formation of sandstone also create structures of spatial variation such as laminations or larger bedding planes within the material using geostatistical techniques the permeability variance observed within quarry fresh blocks of sandstone indicates the subsampling of larger geological structures when cut from the quarry face once blocks have been emplaced within a building they will be subjected to the increased stress of the urban environment these conditions result in exacerbated weathering through processes such as salt and chemical weathering weathering can alter material properties such as permeability with the creation of a secondary permeability produced by the opening pores and alteration of pore connectivity through the application of geostatistics in the analysis of permeability data observed from the weathered block variography reveals the presence of smaller scale structures this suggests that alteration of the sandstone s permeability has led to the creation of new weathering structures within the stone overwriting the initial sedimentary structures these weathering related structures will affect both the magnitude and spatial distribution of permeability within the weathered block the interconnected pathways of permeability created by past weathering facilitate the migration of moisture and salts in solution through the substrate this work has demonstrated that through a geostatistical approach with the application of co kriging these potential moisture pathways can be identified and visualised

geographical information system approach for environmental management in coastal area hardelot plage france the use of geographic information system gis minimizes the effort and improves the efficiency of numerical models the gis provides a platform for high capacity collection management manipulation analysis modeling and display of spatial data the conceptual model is created using gis objects including points arcs and polygons so that it can accurately represent real world condition according to the research problem the geographical model is based on hypergraph based data structure method and a conceptual data model has been created from which a physical data model was elaborated in arcgis9 3 platform the groundwater modeling system gms provides a powerful tool for hydrodynamics modeling and it is able to solve complex problems such as the groundwater flow and seawater intrusion the sand dune system of hardelot plage north of france suffers from a lack of well developed foredune this problem is linked to the almost constant saturation of beach sand which is the potential source of dune nourishment in the south of hardelot the coastline is slowly but constantly retreating to remedy this situation a coupling between a gis and gms was adopted in order to find the possible scenarios which could lower the piezometric surface in the concerned area and allow dune nourishment again the gms used supports the modflow 2000 code a direct approach to designing modflow finite difference model is tedious and less intuitive specifically for complex boundary and initial conditions therefore a modflow model can be developed either using a grid or conceptual model approach the preparation of input data modeling is tedious and takes a long time the model created in gms was calibrated against the historical and observed water level data for 1995 2006 then a hydrodispersive model mt3d code in gms was launched for evaluating sea water intrusion the model was run to generate groundwater and salt concentration scenario during pumping tests

chlorine transport processes through a 2000 m aquifer aquitard system abstract in the paris basin in france the callovo oxfordian cox is currently studied over a 250 km2 surface area by the french national radioactive waste management agency in order to assess the feasibility of long term underground nuclear waste repository the cox is a 140 m thick clay rich layer which is part of the 2000 m aquitard aquifer system constituting the sedimentary cover in such sedimentary context the transport processes of potential contaminants can be represented by both vertical diffusion and horizontal advection through the most permeable layers chloride is used as a natural conservative tracer and is monitored in term of concentrations and isotopic composition 37cl for both pore and groundwater during this study the samples were collected from three boreholes located in the center of the studied zone one of them est433 going down to 2000 m depth the main solute transport process is shown to be vertical diffusion from the massive keuper halite level to the rest of the sedimentary pile this global diffusive system can be occasionally disturbed by horizontal circulation of groundwater occurring in the oxfordian and dogger limestone formations therefore these circulations cut the global diffusive system in a succession of independent diffusive systems in this study the data set was implemented in a simplified 2d solute transport model and scenarii reproducing known history in term of paleo circulations inside the system were applied and allowed to obtained a good fit of the data model results showed that paleo circulations occurring between 145 ma and 110 ma still have an impact on current distribution of chloride in the system especially for 37cl the model highlights the need of the presence of a circulation spatially limited at the base of the liassic formation to fit the data the best fit obtained indicated current residence time of 500 ka in the dogger and oxfordian with respective onset of the circulations at 20 ma and 5 ma

tidal flat sequence controlled by holocene sea level rise in gomso bay west coast of korea intertidal deposits of gomso bay western coast of korea eastern yellow sea consist of a basement pre holocene oxidized unit and a holocene tidal unit in ascending order the pre holocene oxidized unit a yellowish stiff mud belonging to the last stadial or glacial stage before 12 000 yr b p contains plant roots plant fragments and vertical and horizontal microfractures indicating soil formation however it contains no marine shells or microfossils the holocene tidal unit is composed of lower mud facies upper flat mud and upper sand muddy sand facies middle to lower flat sand and generally shows a coarsening upward retrograding trend thus reflecting a holocene relative sea level rise 14c age depth plot for dated samples peats and shells shows that the relative sea level of 7000 yr b p stood at about 6 5 m from the present mean sea level and the relative sea levels of 4000 yr b p and 2000 yr b p stood at 3 m and 2 5 m respectively

detecting the intertidal morphologic change using satellite data abstract the objectives of this study were a to generate an intertidal digital elevation model dem using waterlines extracted from landsat tm and in situ ground levelling data b to quantitatively estimate morphologic change from the generated dems for the years 1991 and 2000 and c to evaluate the chenier migration in the tidal flats of gomso bay korea on extracting the waterlines we considered the tidal flat environments such as tidal conditions remnant surface water suspended sediment and exposure time ground levelling was carried out along one line in 1991 and two lines in 2000 from the extracted waterlines and ground levelling data we succeeded in generating intertidal dems with an accuracy of 10 9 cm r m s overall and 7 3 cm r m s in the lower tidal flats the morphologic changes estimated by subtracting the two dems showed an erosion rate of 9 0 cm over 9 yr that corresponds to an annual mean morphologic change budget of 309 865 m 3 yr overall the gomso tidal flats can be defined as an erosion dominant environment the changes with respect to the sedimentary facies were also evaluated as a the sandy silt flat had a sedimentation rate of 3 4 cm over 9 yr that corresponds to an annual mean budget of 52 552 m 3 yr b the silty sand flat had a sedimentation rate of 14 3 cm over 9 yr that corresponds to a mean erosion of 197 927 m 3 yr and c the sand flat had a sedimentation rate of 11 8 cm over 9 yr that corresponds to a mean change of 58 808 m 3 yr the results comply with the general rules of sedimentology we also investigated the chenier migration which is the most dynamic geomorphologic change in the tidal flats chenier is usually composed by sand and shell as a result of coastal progradation in sand and it is dominantly fed by sediments transported by long shore currents the chenier was found to have migrated about 148 m landward over 6 yr the results demonstrate that satellite remote sensing is an efficient and effective tool for a long term morphologic change estimation in tidal flats

numerical simulation on undrained triaxial behavior of saturated soil by a fluid coupled dem model a fluid coupled dem model is developed in this paper based on particle flow methods in the model soil grain is represented by using a sphere particle and the motion of soil grain is depicted by newton s laws of motion and the force displacement law at contact point the flow of fluid obeys darcy s law and fluid particle interactions are depicted by multi physics coupled formulation a numerical scheme for this model is developed to consider the mechanism for pore pressure generation and volume change induced by deformation undrained triaxial compression tests of saturated soil are simulated by using the coupled method the calculated results are compared with that from constant volume methods and experiments of beijing clayey silt the results show that the deviatoric stress and pore pressure obtained by coupled method are comparable with that of constant volume methods and experiments a series of drained and undrained triaxial compression tests for saturated soil under different confining pressures are also simulated deviatoric stress increases with the increase of confining pressure in both drained and undrained tests the results of undrained test show that stress ratio decreases with increasing confining pressure the decrease of pore pressure drives effective mean stress path to move right upward a loss of soil strength can be found in undrained test by comparing with the strength in drained test and this may be caused by reduction of effective stress

coupled multiphase flow and elasto plastic modelling of in situ gas injection experiments in saturated claystone mont terri rock laboratory abstract understanding gas migration in host rock is one of the most important issues to consider in the final disposal of radioactive waste in deep geological formations in order to investigate gas transport in water saturated argillaceous rock constant gas pressure injection tests on the samples from the mont terri rock laboratory switzerland as well as pulse injection tests with a stepwise increasing of gas pressure were carried out during gas migration desaturation and hydraulic mechanical interaction can be observed to simulate gas migration in water saturated porous media a coupled multiphase flow and mechanical method within the fem code family opengeosys ogs was developed including the van genuchten function for the relationship between capillary pressure and water saturation the approach of mualem for the relative permeability of both gas and water phases and an elasto plastic deformation model two approaches were applied taking into consideration the permeability change by pore gas pressure and by deformation respectively both permeability approaches are based on experimental observations and allow for the significant increase in permeability when gas pressure exceeds the minimal stress the material parameters for the multiphase model are determined using the measured data from laboratory experiments under well defined test conditions with the calibrated model parameters the in situ experiment was simulated good agreement between the numerical results and the experimental data is achieved

chlorine transfer out of a very low permeability clay sequence paris basin france 35cl and 37cl evidence abstract the marine callovo oxfordian clay formation is found at a depth around 410m in the eastern part of the paris basin france it is a very low permeability formation investigated by the french agency for nuclear waste management andra to study the feasibility of a radioactive waste disposal examining hydrogeological and geochemical characteristics of the clay sequence may test confinement properties of this formation this study uses chlorine isotopes to investigate long term transport processes which may carry chemical elements out of the clay layer to the surrounding rocks detailed chlorine concentration and 37cl depth profiles are examined using pore waters and aquifer waters sampled in the clay formation and its surrounding aquifers the dogger at the bottom and the oxfordian kimmeridgian tithonian unit at the top they are discussed in terms of chlorine budget and hydrogeological processes clay pore waters and aquifer waters show strong chlorine concentration depletion a steep cl concentration gradient from the dogger at 500m in depth 2500 mg l to the oxfordian kimmeridgian tithonian aquifer near the surface 10 mg l is associated to a v shaped profile of the 37cl values modelling cl transport shows that a hydrodynamic dispersion process explains cl concentration and 37cl profiles in oxfordian limestone this process implies a mean upward flux of chloride in the 2 6 10 8 8 2 10 8 mole m2 yr range from the clay formation towards upper limestones where a westward advective flow disperses the chloride the modelling and knowledge of underground water transfer suggest a maximum effective cl hydrodynamic vertical dispersion coefficient vertical cl transport coefficient of 7 6 10 10 m2 s chlorine transfer through the callovo oxfordian clay since deposition 160my ago can be mainly described by the interplay of an early dilution and a later hydrodynamic dispersion event which has apparently erased most of the isotopic effects of diagenetic events such as early diffusion ion filtration etc

establishing constraints on groundwater ages with 36cl 14c 3h and noble gases a case study in the eastern paris basin france abstract groundwaters from the tithonian kimmeridgian oxfordian and upper dogger aquifers within the eastern part of the paris basin france were characterised using 3 h 14 c and 36 cl and noble gases tracers to evaluate their residence times and determine their recharge period this information is an important prerequisite to evaluating the confinement properties of the callovo oxfordian clay formation sandwiched between the oxfordian aquifer and the dogger aquifer currently being investigated by the french nuclear waste management agency andra for radioactive waste disposal data presented in this paper are used to test 4 hypotheses 1 the oxfordian limestone is isolated from the overlying tithonian kimmeridgian surface aquifer this first hypothesis is supported by the presence of measurable 3 h activities in groundwaters from the surface aquifer 6 11 tu and by its absence in groundwaters derived from deeper aquifers 2 the callovo oxfordian clay sequence in the vicinity of the url serves as an effective barrier to advective flow and transport between the underlying upper dogger aquifer and the overlying oxfordian limestone aquifer this second hypothesis is supported by relatively low concentrations of cl 3 5 78 mg l 1 na 15 145 mg l 1 br 0 08 0 4 mg l 1 and 4 he rad 0 2 2 3 ccstp g 1 and slightly higher 36 cl cl ratios 2 7 59 10 15 at at 1 in groundwaters from the oxfordian aquifer compared to those from the upper dogger aquifer 345 4027 mgcl l 1 402 2390 mgna l 1 1 8 22 2 mgbr l 1 1 6 37 2 ccstp he g 1 1 5 10 15 at 36 cl at 1 cl 3 groundwaters from the oxfordian aquifer in the vicinity of url are pre holocene with residence times exceeding 10 ka geochemical and isotopic lines of evidence for this hypothesis include a 13 c values measured on oxfordian aquifer waters that are close to 13 c of the aquifer matrix reflecting strong isotopic exchange over several thousand years b noble gas temperatures that indicate recharge temperatures between 3 and 8 6 c lower by 2 7 c than the modern average temperature in this area c radiogenic 4 he concentrations between 0 16 10 5 and 2 3 10 5 ccstp g 1 of water about 2 3 orders of magnitude greater than the 4 he concentration of air equilibrated water 4 groundwater residence time for the upper dogger aquifer in the vicinity of the url probably exceed several hundred thousand years such long residence times are indicated by the accumulation of radiogenic he up to 37 10 5 ccstp g 1 assuming a closed system primary contributors to uncertainties in interpretation of the data presented in this paper are the lack of well defined 36 cl cl input ratio knowledge about the 4 he rad sources for oxfordian and dogger aquifers knowledge about transport processes occurring through the dogger aquifer and the extensive dilution of initial 14 c activities by dissolution exchange with aquifer matrix overall however although the data presented in this paper remain semi quantitative due to inevitable intrinsic limitations of the methods none contradict the hypotheses of long residence times and aquifer isolation in the vicinity of the url

analysis of flow path around the sealing section hg a experiment in the mont terri rock laboratory as part of the hg a experiment in the mont terri rock laboratory large scale in situ water gas injection experiments was conducted in a microtunnel this research work focuses on the numerical analysis of the experimental data and the in situ observations concerning a temporary change of the hydromechanical properties of opalinus clay during experimental operations three phases were numerically interpreted these included the generation of excavation damaged zone during tunnel excavation in which highly permeable flow paths around the tunnel have been formed the self sealing effect during water tests and the pressure evolution during a long term gas injection test a coupled two phase flow and mechanics model taking into account the strong anisotropic properties of opalinus clay was developed to interpret the measured data the hydraulic anisotropy was described by a transversely isotropic permeability tensor an elasto plastic model was established to consider both stiffness anisotropy and strength anisotropy anisotropic plasticity was studied using the microstructure tensor method

landslide susceptibility mapping by neuro fuzzy approach in a landslide prone area cameron highlands malaysia this paper presents the results of the neuro fuzzy model using remote sensing data and geographic information system for landslide susceptibility analysis in a part of the cameron highlands areas in malaysia landslide locations in the study area were identified by interpreting aerial photographs and satellite images supported by extensive field surveys landsat tm satellite imagery was used to map the vegetation index maps of the topography lineaments normalized difference vegetation index ndvi and land cover were constructed from the spatial data sets eight landslide conditioning factors such as altitude slope gradient curvature distance from the drainage distance from the road lithology distance from the faults and ndvi were extracted from the spatial database these factors were analyzed using a neuro fuzzy model adaptive neuro fuzzy inference system to produce the landslide susceptibility maps during the model development works a total of five landslide susceptibility models were constructed for verification the results of the analyses were then compared with the field verified landslide locations additionally the receiver operating characteristic curves for all landslide susceptibility models were drawn and the area under curve values were calculated landslide locations were used to validate the results of the landslide susceptibility map and the verification results showed a 97 accuracy for model 5 employing all parameters produced in the present study as the landslide conditioning factors the validation results showed a sufficient agreement between the obtained susceptibility map and the existing data on the landslide areas qualitatively the model yields reasonable results which can be used for preliminary land use planning purposes

long term experimental evidences of saturation of compacted bentonite under repository conditions abstract this paper summarises the information gathered in the last 15 years on the saturation of compacted bentonite obtained from different laboratory scale tests a large scale mock up test and a real scale in situ test that were performed to simulate the conditions of the bentonite barrier in a high level radioactive waste repository and to better understand the hydration heating processes in all the tests the bentonite used was the spanish febex bentonite the maximum temperature in the system was 100 c and the water used was of the granitic type with low salinity some of the tests were running for more than thirteen years the migration of water vapour in areas affected by the high temperature induced by the radioactive waste decay is very rapid its extent depending on the actual temperature and bentonite porosity the water vapour condensates in cooler areas and this causes water content increases in internal zones of the barrier where the liquid water coming from the host rock has not yet arrived the hydration kinetics is initially quicker when the temperature is high provided no vapour phase is formed nevertheless the major effect of the thermal gradient on saturation is a delaying of it in the inner parts of the barrier which can be very persistent and depends on the actual thermal gradient and consequently on the barrier thickness and boundary conditions during the transient period in which the barrier is saturating important changes in the water content and dry density of the bentonite are generated which induce bentonite density and water content gradients along its thickness these gradients could eventually disappear once the barrier is fully saturated depending on the irreversibility of the deformations the average density of the water in the saturated barrier will be higher than 1 g cm3 due to the predominance of high density interlayer water in the compacted bentonite and consequently more water than expected according to calculations made considering the density of free water would fit in the bentonite pores the rate of hydration of the barrier depends on the bentonite and surrounding media hydraulic properties that is water availability waste temperature and buffer thickness and geometry

neandertal and denisovan dna from pleistocene sediments although a rich record of pleistocene human associated archaeological assemblages exists the scarcity of hominin fossils often impedes the understanding of which hominins occupied a site using targeted enrichment of mitochondrial dna we show that cave sediments represent a rich source of ancient mammalian dna that often includes traces of hominin dna even at sites and in layers where no hominin remains have been discovered by automation assisted screening of numerous sediment samples we detected neandertal dna in eight archaeological layers from four caves in eurasia in denisova cave we retrieved denisovan dna in a middle pleistocene layer near the bottom of the stratigraphy our work opens the possibility of detecting the presence of hominin groups at sites and in areas where no skeletal remains are found

simulation of shoreline change using airsar and polsar c band data this paper presents a new approach for modeling shoreline change due to wave energy effects from remotely sensed data the airborne airsar and polsar data were employed to extract wave spectra information and integrate them with historical remotely sensed data such as aerial photography data to model the rate of change of the shoreline a partial differential equation pde of the wave conversion model was applied to investigate the wave refraction patterns the volume of sediment transport at several locations was estimated based on the wave refraction patterns the shoreline change model developed was designed to cover a 14 km stretch of shoreline of kuala terengganu in peninsular malaysia the model utilized data from aerial photographs airsar polsar ers 2 and in situ wave data the results show that the shoreline rate of change modeled from the quasi linear wave spectra algorithm has a significant relationship with one estimated from historical vector layers of aerial photography airsar and polsar data with the quasi linear algorithm an error of 0 18 m year in shoreline rate of change determination was obtained with c vv band

measurement of in situ stress in weak rocks at mont terri rock laboratory switzerland in situ stress measurements in weak rocks such as clay shales that respond strongly to environmental changes are particularly difficult an extensive in situ stress measurement program has been conducted at the mont terri rock laboratory in northwestern switzerland hydraulic fracturing undercoring around a 600 mm diameter borehole using csiro triaxial strain cells and the borehole slotter were used to establish the state of stress for the opalinus clay at this location conflicting orientations and magnitudes resulted from the measurement programs three dimensional elastic modelling was used in conjunction with tunnel and borehole observations to establish the most likely stress tensor a stress measurement program using a borehole deformation gauge is currently underway to check the stress tensor resulting from the observational modelling

waterline extraction from landsat tm data in a tidal flat a case study in gomso bay korea waterline extraction is potentially one of the most effective satellite remote sensing tools for studying changes in tidal flat environment and coastlines however its application to the study of tidal flats has not been investigated in detail the waterline in a tidal flat in gomso bay korea is characterized and evaluated using 27 sets of landsat thematic mapper tm and earth observing system terra eos terra advanced spaceborne thermal emission and radiometer aster data ground truth data including grain size soil moisture content ground levelling and waterline tracking have been obtained the choice of spectral bands in terms of tidal conditions turned out to play a key role in locating the waterline while the waterlines extracted from near infrared nir short wavelength infrared swir and thermal infrared tir data are commonly reliable on the flood tide the discrepancies between different bands become large on the ebb tide the bands tir nir and swir are in that order decreasingly effective in extracting the waterline while ebb tides are in progress the effect of turbid water on nir can be reduced by a ratioing of nir and the visible band the location of the waterline is also an important factor to consider the discrepancy is largest on the middle tidal flat selection of the proper band for waterline extraction under various conditions is suggested however no single band can accommodate all aspects of the tidal flat environment a schematic model associated with the spectral reflectance of the tidal flat is proposed in which the remnant water scattered on the surface after exposure is emphasized as an additional factor

knowledge of the three french underground laboratory sites abstract from march 1994 to august 1996 andra conducted a large reconnaissance work on three sites for possible underground research laboratories these surveys highlighted for each site the presence of a geological formation the properties of which meet the requirements of the french fundamental safety rules on the east site the selected formation is a 130 m thick argillite layer on the gard site the layer is composed of close packed siltites which are 200 400 m thick on the vienne site a hercynian granodiorite batholith was found under a 160 m thick jurassic overdurden

bondi cave and the middle upper palaeolithic transition in western georgia south caucasus abstract the late pleistocene expansion of anatomically modern humans amhs into eurasia and the concurrent demise of the neanderthals appears to be a complex and regionally variable process the southern caucasus region with its rich cave sites has recently provided important results regarding this process in this paper we report on the results of fieldwork in bondi cave western georgia providing a new radiocarbon chronology stratigraphic observations analyses of lithic technology and provenance faunal and floral remains as well as paleoenvironmental data the cave includes middle palaeolithic ca 45 000 ka cal bp cultural horizons and a long upper palaeolithic sequence ca 40 000 27 000 cal bp from layer v to iv a modern human tooth was found in layer vb we estimate its age at 39 000 35 800 cal bp 95 4 based on the bayesian age model we built if the context of the tooth is reliable as we think it is this would make it the oldest morphologically modern human in the caucasus upper palaeolithic hunting of tur and bison as well as the collection of various plants including flax is attested mobile upper palaeolithic foragers inhabited the cave in generally cold and dry periods but a mosaic of environments including forests and meadows was nonetheless available to them the archaeological sequence of bondi and adjacent sites indicates a substantial time gap between the middle and upper palaeolithic occupations thus disproving neanderthal amh interaction in this area and lending support to a replacement scenario in the southern caucasus assuming of course that the early upper palaeolithic eup is related to the arrival of amhs

monitoring changing position of coastlines using thematic mapper imagery an example from the nile delta coastline movement due to erosion and deposition is a major concern for coastal zone management very dynamic coastlines such as sections of the nile delta coast pose considerable hazards to human use and development and rapid replicable techniques are required to update coastline maps of these areas and monitor rates of movement the synoptic capability of landsat thematic mapper imagery enables monitoring of large sections of coastline at relatively coarse 30 m spatial resolution by comparing positions of the nile delta coast in 1984 1987 and 1990 1991 mapped using a region growing image segmentation technique areas of rapid change can be identified and targeted for more detailed monitoring in the field or using higher resolution images rates of erosion and deposition can be estimated crudely and areas where change appears to be accelerating can also be identified areas of severe erosion along the nile delta coast are found to be confined to the promontories of the present day mouths of the nile at rosetta and damietta eroding shorelines are mostly flanked by accreting shorelines showing that some of the eroded material is redistributed along the coast the technique outlined here has potential to augment conventional field based surveying for monitoring shoreline changes over short timescales

study of the polarimetric characteristics of mud flats in an intertidal zone using c and x band spaceborne sar data abstract the polarimetric characteristics of a mud flat area in the intertidal zone near jiangsu china are analyzed under different environmental conditions using x band and c band spaceborne synthetic aperture radar sar data from the terrasar x tsx and radarsat 2 r2 satellites the dominant scattering mechanisms of different objects including mud flats and aquaculture facilities in the intertidal zone are studied based on the polarimetric target decomposition of fully polarimetric r2 data the polarimetric characteristics of different objects in the intertidal zone are quantitatively compared using the depolarization parameters derived from the r2 data which indicate that tides have different effects on the dominant scattering mechanisms of the mud flats and aquaculture farms furthermore comparisons of the c band and x band polarimetric characteristics of the mud flats and aquaculture farms in the intertidal zone are analyzed by combining the tsx and r2 data the results show that surface scattering is the dominant mechanism of the mud flats whereas different dominant mechanisms occur in the aquaculture areas present during different tides interestingly strikingly similar polarimetric characteristics of mud flats and aquaculture in x band and c band sar are observed and these novel results were achieved through a depolarization analysis based on the tsx and r2 data in synergy

accurate and efficient determination of the shoreline in ers 1 sar images extraction of the shoreline in sar images is a difficult task to perform using simple image processing operations such as grey value thresholding due to the presence of speckle and because the signal returned from the sea surface may be similar to that from the land a semiautomatic method for detecting the shoreline accurately and efficiently in ers 1 sar images is presented this is aimed primarily at a particular application namely the construction of a digital elevation model of an intertidal zone using sar images and hydrodynamic model output but could be carried over to other applications a coarse fine resolution processing approach is employed in which sea regions are first detected as regions of low edge density in a low resolution image then image areas near the shoreline are subjected to more elaborate processing at high resolution using an active contour model over 90 of the shoreline detected by the automatic delineation process appear visually correct

shoreline change of chongming dongtan and response to river sediment load a remote sensing assessment summary chongming dongtan located in the center of the yangtze estuary is a ramsar wetland of international importance and national nature reserve the dramatic decrease in river sediment load has attracted considerable scientific interest to this area but few studies have paid attention to the shoreline dynamics this study uses landsat images spanning from 1987 to 2010 and an orthogonal transect method which was previously developed by the authors to model the spatial and temporal characteristics of shoreline change and explore its relationship to reduced river sediment load by use of regression analysis on three different spatial scales results show a general decrease in the average rates of shoreline change throughout the entire study period the maximum average shoreline change rate of 115 5 m year occurred in the 1987 1990 interval and the minimum rate of 20 4 m year occurred from 2006 to 2008 based on average rates of shoreline change the coast of dongtan was divided into three segments the erosion segment eastern accretion segment and northern accretion segment the temporal pattern of the northern accretion segment is almost completely opposite to that of the eastern accretion segment the strongest correlation transects are located on the northern side of the eastern tip of dongtan and the next strongest transects are located on the south side other transects have a very low correlation transect 19 near the easternmost tip of dongtan has a near zero correlation r2 0 0045 but has the fastest accretion rate and in general an increase in the shoreline change rate the average rate of shoreline change and the net accretion area in dongtan as a whole are significantly associated with sediment discharge at datong station r2 0 69 and 0 75 respectively this implies that shoreline accretion in dongtan will probably slow down gradually if the river sediment load continues to decrease in the future the shoreline change rates achieved using our approach are consistent with previous studies but the relationship with the river sediment load is different from results in a previous study on intertidal wetland based on bathymetric maps the results and methods may be helpful in coastal management and understanding the evolution of the entire delta from the perspective of shoreline change