ground penetrating radar assisted saturation and permeability estimation in bimodal systems near surface investigations often require characterization of vadose zone hydraulic parameters conventional sampling or borehole techniques for estimating these parameters are costly time consuming and invasive all of which limit collection of hydrogeological data at a spacing needed for detailed site characterization incorporation of two or three dimensional densely sampled geophysical data with conventional hydrological data increases the amount of data available for the characterization and thus has the potential to significantly improve the hydraulic parameter estimates over those obtained from borehole data alone the hydraulic estimation procedure can be greatly improved by incorporating dielectric information potentially available from ground penetrating radar gpr a noninvasive high resolution geophysical method the procedures for collecting and processing gpr data in the format needed for the proposed estimation technique are relatively new and still a topic of research our method requires as a starting point the ability to estimate dielectric constants from gpr data numerical experiments were performed to investigate the general utility of the gpr assisted estimation technique under a range of conditions three bimodal systems were investigated each system being composed of a sand facies together with another facies with a larger clay volume fraction each facies was defined using characteristic values of clay content porosity and permeability using dielectric information and petrophysical relations degree of saturation and intrinsic permeability values at each location within the three systems were identified for bimodal systems a dielectric constant measurement corresponds to two possible values of saturation and intrinsic permeability at each location single values of saturation and intrinsic permeability were estimated from these values using the principle of maximum likelihood results from case studies demonstrate that a combination of gpr data with conventional borehole data significantly improves the estimates of saturation and has the potential to improve the estimates of permeability over those obtained from well bore data alone the proposed method should be especially advantageous for vadose zone characterization in areas favorable for gpr data acquisition where detailed hydraulic parameter information is required but the drilling of numerous boreholes is prohibited

lamination of swampy rivulets rivularia haematites stromatolites in a temperate climate abstract swampy rivulets rivularia haematites d c agardh stromatolites were collected from the same site on the plateau de langres chaugey france over a seven year period specimens were studied in thin sections in culture media under varying conditions of temperature and illumination and by scanning electron microscope sem in order to investigate the processes of calcification and lamination new sem observations confirm the polycrystalline structure of the lamellae reported by the authors and show that the crystals composing these lamellae are elongate and aligned in the same direction as the filaments linked by them the lamellae were also isolated in transverse sections under sem and found to correspond to what under the light microscope appear to be honeycomb structures the diameter of alveoli can be the same as that of a false branching their walls formed by the outer sheath have a dense network of microfibrils these observations confirm the formation of calcitic lamellae at the false branching points and in contact with the microfibrils of the outer sheath confirmation of earlier hypotheses was sought through observation in thin section of the stromatolites collected over seven years micritic dark laminae are thought to form in three stages i formation of a dark lamina by formation of a false branching zone in the wet season ii initial calcification in this zone as microsparitic and sparitic lamellae during even a short dry spell and iii subsequent bacterial micritization of the lamellae during an extended warm dry season the sparitic light laminae form around the hair bearing regions lamination was first considered with regard to the annual radial growth rate of r haematites the thin section may display either a single dark lamina for two years growth or a dark lamina thicker than the annual growth rate examination of local meteorological data accounts for the first phenomenon by a wet spell of more than 13 months and the second by a warm dry period of one month it may therefore take several years for a couplet to form as growth of the cyanobacterial colony is influenced by climatic variations the different calcification phenomena were also correlated with dry spells these interpretations are consistent with results obtained by experiments

sea cliff erosion as a function of beach changes and extreme wave runup during the 1997 1998 el nino abstract over time scales of hundreds to thousands of years the net longshore sand transport direction along the central california coast has been driven to the south by north pacific winter swell in contrast during the el nino winter of 1997 1998 comparisons of before and after airborne lidar surveys showed sand was transported from south to north and accumulated on the south sides of resistant headlands bordering pocket beaches this resulted in significant beach erosion at the south ends of pocket beaches and deposition in the north ends coincident with the south to north redistribution of sand shoreline morphology became prominently cuspate with longshore wavelengths of 400 700 m the width and elevation of beaches were least where maximum shoreline erosion occurred preferentially exposing cliffs to wave attack the resulting erosional hotspots typically were located in the embayments of giant cusps in the southern end of the pocket beaches the observed magnitude of sea cliff retreat which reached 14 m varied with the number of hours that extreme wave runup exceeded certain thresholds representing the protective capacity of the beach during the el nino winter a threshold representing the width of the beach performed better than a threshold representing the elevation of the beach the magnitude of cliff erosion can be scaled using a simple model based on the cross shore distance that extreme wave runup exceeded the pre winter cliff position cliff erosion appears to be a balance between terrestrial mass wasting processes which tend to decrease the cliff slope and wave attack which removes debris and erodes the cliff base increasing the cliff slope

high energy ephemeral stream deltas an example from the upper silurian holmestrand formation of the oslo region norway abstract the late orogenic deposits of the upper silurian holmestrand formation of the oslo region norway comprises sharply alternating ephemeral stream and sandy beach face deposits the formation is divided into three units reflecting the down slope change on an extensive ephemeral stream delta system the lower unit of the formation comprises ephemeral stream sediments as stacked sheet sandstone bodies deposited on a broad coastal floodplain each sheet is bounded by a lower intraclast strewn scoured surface overlain by massive horizontally stratified low angle and trough cross bedded sandstones in the medial and upper units of the formation the ephemeral stream sediments alternate with beach face deposits forming ephemeral stream deltas the ephemeral stream deltas are marked by intraclast strewn scoured surfaces and dominated by trough cross bedded sandstones they may contain escapement burrows marine bioturbation and wave working of the delta surfaces the beach face deposits are composed of alternating irregular horizontally stratified sandstones with current and wave ripple cross lamination and tabular cross bedded sandstones deposition took place in a coastal non to micro tidal shallow water environment influenced by longshore currents and low palaeo wave energy seven ichnotaxa are recognized and support the sedimentary record of a transitional environment between a broad coastal floodplain and a shallow marine environment the presence of calcretes indicate an arid to semi arid palaeo climate

sequential approach to joint flow seismic inversion for improved characterization of fractured media seismic interpretation of subsurface structures is traditionally performed without any account of flow behavior here we present a methodology for characterizing fractured geologic reservoirs by integrating flow and seismic data the key element of the proposed approach is the identification within the inversion of the intimate relation between fracture compliance and fracture transmissivity which determine the acoustic and flow responses of a fractured reservoir respectively owing to the strong but highly uncertain dependence of fracture transmissivity on fracture compliance the modeled flow response in a fractured reservoir is highly sensitive to the geophysical interpretation by means of synthetic models we show that by incorporating flow data well pressures and tracer breakthrough curves into the inversion workflow we can simultaneously reduce the error in the seismic interpretation and improve predictions of the reservoir flow dynamics while the inversion results are robust with respect to noise in the data for this synthetic example the applicability of the methodology remains to be tested for more complex synthetic models and field cases

dunefoot dynamics along the dutch coast the dynamics of the dunefoot along a 160 km portion of the dutch coast has been investigated based on a data set of annual surveys dating back to as early as 1850 the linearly detrended or residual dunefoot positions comprise an alongshore uniform and an alongshore non uniform component the former is expressed as 10 to 15 m of landward retreat along extensive 10 km stretches of coast during years with severe storm surges and as up to 5 m of seaward advance during years without significant storm activity the latter alongshore non uniform component is organized in sandwave like patterns which may have a longevity of decades to up to the duration of the entire data set 150 years their wavelengths vary along the coast from 3 5 to 10 km migration rates are 0 200 m a 1 dunefoot sandwaves are shown to be the shoreward extensions of similar sandwave patterns in the beach position the non uniform dunefoot behaviour constitutes at least 80 per cent of the total residual dunefoot dynamics implying that along the dutch coast residual dunefoot variability is controlled by temporal and spatial variability in beach characteristics and not by storm induced uniform erosion various potential mechanisms causing beach sandwaves are discussed copyright 2002 john wiley sons ltd

inversion of tracer test data using tomographic constraints 1 we have developed a methodology for inverting tracer test data using zonation information obtained from two dimensional radar tomograms to improve the typically overly smooth hydraulic conductivity fields obtained from conventional inversion of tracer test data the method simultaneously yields two dimensional estimates of hydraulic conductivity as well as petrophysical relationships that relate hydraulic conductivity to radar velocity these relationships can be assumed to be stationary throughout the area of investigation or to vary as a function of zonation using a synthetic three dimensional hydraulic conductivity field we apply the developed inversion methodology and explore the impact of the strength and stationarity of the petrophysical relationship as well as the impact of errors that are often associated with radar data acquisition such as unknown borehole deviation we find that adding radar tomographic data to tracer test data improves hydrogeological site characterization even in the presence of minor radar data errors the results are contingent on the assumption that a relationship between radar velocity and hydraulic conductivity exists therefore the applicability of the proposed method may be limited to field sites where this condition is partially or fully satisfied

migration and sedimentology of longshore sandwaves long point lake erie canada this paper describes the formation migration and sedimentology of sandwaves along the distal end of long point a 40 km long spit in lake erie some seven to nine sandwaves occur in a zone over the last 14 km of the spit they are characteristically 50 100 m wide at the downdrift end range in length from 350 m to 1500 m and migrate alongshore at rates that are typically 100 300 m year 1 measurements over a 7 year period show two forms of alongshore sandwave migration 1 a migratory jump and 2 downdrift accretion the migratory jump is commonly 200 500 m year 1 and results from the onshore migration and welding of an inner nearshore bar to the downdrift end of the sandwave this in turn leads to emergence of the bar over a distance of several hundred metres downdrift of the sandwave and isolation of the trough landward of the bar infilling of the trough abstracts large volumes of sediment from the local sediment transport system and may affect movement of the sandwave in the following year or movement of the next sandwave downdrift downdrift accretion commonly results in migration of 50 150 m year 1 and results from the refraction of waves around the distal end of the sandwave and episodic accretion of small swash bars this mechanism occurs less frequently and appears to reflect a local condition of lower sediment abundance often triggered by a large migratory jump in the previous year the process of bar emergence and infilling produces a distinct suite of sedimentary structures associated with the infilling of the landward trough and building of the sandwave berm the initial shoreline perturbation that generates the sandwave results from onshore migration and welding of inner nearshore bars and the development and growth of the sandwaves is promoted by refraction of highly oblique waves

porosity prediction from seismic data the inversion of seismic traces allows the estimation of reservoir porosity from an analysis of transit times derived from the pseudo velocity logs a four step computational procedure is illustrated consisting of i inversion of seismic traces and calculation of interval velocities ii accurate stratigraphic interpretation iii determination of the petrophysical parameters for the porosity evaluation iv analysis of the reliability of the results and final corrections both the possibilities and the limits of the method are discussed one of the causes of error is the fact that impedances and not velocities are readily obtainable from seismic data moreover the porosity due to fracturation contributes only slightly to velocity while it often contributes most importantly to the permeability results are shown for two of the most significant reservoir types i e carbonatic and clastic two cases belonging to the latter type will be examined in the first case the primary porosity is dominant the second case is very complex and both primary and secondary porosity are present

mapping permeability in heterogeneous aquifers using hydrologic and seismic data a new method is presented for identification of the permeability distribution in near surface aquifers in addition to using the usual sparsely sampled pressure and permeability data the method incorporates densely sampled seismic data as obtained from a reflection or tomography survey along with empirical relationships between seismic and hydraulic properties the procedure is to first estimate by hydrologic inversion a pressure field then the velocity permeability pressure relationship is used to map the inverted pressure and measured seismic data to multivalued estimates of the permeability of those the most probable value based on the hydrologic inversion is selected in synthetic case studies the tremendous increase in coverage offered by the seismic data leads to dramatically better results in terms of both accuracy and resolution an appealing feature is the use of relatively easy to acquire pressure data a second is the incorporation of geophysical data which can sample an entire aquifer remotely without the need for an expensive and invasive drilling program

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

large scale dam removal on the elwha river washington usa coastal geomorphic change abstract two dams on the elwha river washington state usa trapped over 20 million m3 of mud sand and gravel since 1927 reducing downstream sediment fluxes and contributing to erosion of the river s coastal delta the removal of the elwha and glines canyon dams initiated in september 2011 induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the geomorphic response of a coastal delta to these increases detailed measurements of beach topography and nearshore bathymetry show that 2 5 million m3 of sediment was deposited during the first two years of dam removal which is 100 times greater than deposition rates measured prior to dam removal the majority of the deposit was located in the intertidal and shallow subtidal region immediately offshore of the river mouth and was composed of sand and gravel additional areas of deposition include a secondary sandy deposit to the east of the river mouth and a muddy deposit west of the mouth a comparison with fluvial sediment fluxes suggests that 70 of the sand and gravel and 6 of the mud supplied by the river was found in the survey area within about 2 km of the mouth a hydrodynamic and sediment transport model validated with in situ measurements shows that tidal currents interacting with the larger relict submarine delta help disperse fine sediment large distances east and west of the river mouth the model also suggests that waves and currents erode the primary deposit located near the river mouth and transport sandy sediment eastward to form the secondary deposit though most of the substrate of the larger relict submarine delta was unchanged during the first two years of dam removal portions of the seafloor close to the river mouth became finer modifying habitats for biological communities these results show that river restoration like natural changes in river sediment supply can result in rapid and substantial coastal geomorphological responses

the offshore export of sand during exceptional discharge from california rivers littoral cells along active tectonic margins receive large inputs of sand and gravel from coastal watersheds and commonly lose this sediment to submarine canyons one hypothesis is that the majority of coarse sand and gravel river sediment discharge will be emplaced within and immediately resupply local littoral cells a competing hypothesis is that the infrequent large floods that supply the majority of littoral sediment may discharge water sediment mixtures within negatively buoyant hyperpycnal plumes that transport sediment offshore of the littoral cell here we summarize pre and post flood surveys of two wave dominated california united states river deltas during record to near record floods to help evaluate these hypotheses the 1982 1983 delta at the san lorenzo river mouth and the 2005 delta at the santa clara river mouth flood sedimentation at both deltas resulted in several meters of aggradation and hundreds of meters of offshore displacement of isobaths one substantial difference between these deltas was the thick 2 m aggradation of sand on the inner shelf of the santa clara river delta that contained substantial amounts 50 of littoral grade sediment once deposited on the inner shelf only a fraction 20 of this river sand was observed to migrate toward the beach over the following 5 yr furthermore simple hypopycnal plume behavior could not explain deposition of this sand on the inner shelf thus during an exceptional flood a substantial amount of littoral grade sand was exported offshore of the littoral system at the santa clara river mouth likely from hyperpycnal plume processes and was deposited on the inner shelf

reversing storm hotspots on sandy beaches spatial and temporal characteristics coastal erosion hotspots are defined as sections of coast that exhibit significantly higher rates of erosion than adjacent areas this paper describes the spatial and temporal characteristics of a recently identified type of coastal erosion hotspot which forms in response to storms on uninterrupted sandy coasts largely free from human intervention these are referred to here as reversing storm hotspots because the erosion is reversed by accretion of a similar magnitude to the storm induced erosion the accretion occurs within a few days or weeks of fair weather after the storm reversing storm hotspots observed here on two us east coast beaches have a longshore length averaging 3 86 km a cross shore excursion magnitude of erosion or accretion averaging 15 4 m and a time scale of days to weeks associated with individual storm events these spatial and temporal scales clearly distinguish reversing storm hotspots from previously described forms of longshore variability in erosion including those attributed to several types of shoreline undulations and hotspots associated with long term shoreline change

longshore sand waves at southampton beach new york observation and numerical simulation of their movement abstract this paper describes measurements and numerical simulations of the movement of longshore sand waves observed at southampton beach long island new york these large morphologic features are created by periodic opening of a small inlet and subsequent welding of its ebb shoal to the beach longshore sand waves are wave like forms that maintain identity while moving along the shore and represent a simple type of collective sediment movement or largescale coastal behavior despite being described as early as 1939 few measurements of longshore sand waves have been made and their dynamic behavior is not well understood eleven longshore sand waves were identified along southampton beach and have an average length of 0 75 km and an amplitude of 40 m migration speed was greatest under winter wave action and reached an average 1 09 km year 1 and yearly average speed including summer calms was a much lower 0 35 km year 1 during a 16 month observation period the longshore sand waves did not disperse during their steady migration westward in the direction of predominant wave incidence and longer waves moved faster than those with smaller wavelengths a numerical model of shoreline change including both standard particulate longshore sand transport and a component describing migration of a longshore sand wave is developed in which the velocity of the wave is related to the calculated longshore discharge of water the model shows wave refraction to be an important mechanism contributing to the longevity of longshore sand waves acting to retard the otherwise expected diffusion model calculations of the migration of a single longshore sand wave agree quantitatively with the observations

alongshore sediment bypassing as a control on river mouth morphodynamics river mouths shoreline locations where fluvial and coastal sediments are partitioned via erosion trapping and redistribution are responsible for the ultimate sedimentary architecture of deltas and because of their dynamic nature also pose great management and engineering challenges to investigate the interaction between fluvial and littoral processes at wave dominated river mouths we modeled their morphologic evolution using the coupled hydrodynamic and morphodynamic model delft3d swan model experiments replicate alongshore migration of river mouths river mouth spit development and eventual spit breaching suggesting that these are emergent phenomena that can develop even under constant fluvial and wave conditions furthermore we find that sediment bypassing of a river mouth develops though feedbacks between waves and river mouth morphology resulting in either continuous bypassing pathways or episodic bar bypassing pathways model results demonstrate that waves refracting into the river mouth bar create a zone of low alongshore sediment transport updrift of the river mouth which reduces sediment bypassing sediment bypassing in turn controls the river mouth migration rate and the size of the river mouth spit as a result an intermediate amount of river discharge maximizes river mouth migration the fraction of alongshore sediment bypassing can be predicted from the balance between the jet and the wave momentum flux quantitative comparisons show a match between our modeled predictions of river mouth bypassing and migration rates observed in natural settings

a numerical three dimensional conditioned unconditioned stochastic facies type model applied to a remediation well system in this study a three dimensional stochastic facies based aquifer model was developed the model can be used to numerically simulate flow and solute transport in heterogeneous groundwater aquifers the stochastic generation process can be conditioned by using available facies information in one vertical plane or two orthogonal vertical ones in this study the information was obtained from a facies interpretation of a vertical georadar profile in a natural gravel formation in switzerland in the domain outside the known profile unconditioned lenses and layers were generated at random according to statistical information on coherent sedimentary structures based on observations in adjacent gravel pits jussel et al 1994a the method was applied to a single extraction well designed to capture an initially block shaped contaminant plume a total of 80 conditioned and unconditioned synthetic aquifers was generated the flow and transport simulations were performed using a finite element flow model and a random walk transport model the results are presented as the ensemble of integral solute mass recovery curves of single realizations one would expect conditioning to reduce the bandwidth of the recovery curves representing the uncertainty but the results show that the bandwidth even increased this effect was attributed to a discrepancy in the mean volumetric fraction of the different facies types in the conditioned and the unconditioned cases moreover a simulation using a homogeneous model with constant equivalent flow and transport parameters overestimated the remediation efficiency the influence of a linear reversible equilibrium sorption on the remediation well efficiency was taken into account by an uncorrelated random field of the retardation factor based on values from the literature however the impact of the variability in hydraulic conductivity clearly exceeded the effect of the variability in the retardation factor

beach morphology and change along the mixed grain size delta of the dammed elwha river washington abstract sediment supply provides a fundamental control on the morphology of river deltas and humans have significantly modified these supplies for centuries here we examine the effects of almost a century of sediment supply reduction from the damming of the elwha river in washington on shoreline position and beach morphology of its wave dominated delta the mean rate of shoreline erosion during 1939 2006 is 0 6 m yr which is equivalent to 24 000 m3 yr of sediment divergence in the littoral cell a rate approximately equal to 25 50 of the littoral grade sediment trapped by the dams semi annual surveys between 2004 and 2007 show that most erosion occurs during the winter with lower rates of change in the summer shoreline change and morphology also differ spatially negligible shoreline change has occurred updrift west of the river mouth where the beach is mixed sand to cobble cuspate and reflective the beach downdrift east of the river mouth has had significant and persistent erosion but this beach differs in that it has a reflective foreshore with a dissipative low tide terrace downdrift beach erosion results from foreshore retreat which broadens the low tide terrace with time and the rate of this kind of erosion has increased significantly from 0 8 m yr during 1939 1990 to 1 4 m yr during 1990 2006 erosion rates for the downdrift beach derived from the 2004 2007 topographic surveys vary between 0 and 13 m yr with an average of 3 8 m yr we note that the low tide terrace is significantly coarser mean grain size 100 mm than the foreshore mean grain size 30 mm a pattern contrary to the typical observation of fining low tide terraces in the region and worldwide because this cobble low tide terrace is created by foreshore erosion has been steady over intervals of at least years is predicted to have negligible longshore transport compared to the foreshore portion of the beach and is inconsistent with oral history of abundant shellfish collections from the low tide beach we suggest that it is an armored layer of cobble clasts that are not generally competent in the physical setting of the delta thus the cobble low tide terrace is very likely a geomorphological feature caused by coastal erosion of a coastal plain and delta which in turn is related to the impacts of the dams on the elwha river to sediment fluxes to the coast

a stochastic approach to the characterization of lithofacies from surface seismic and well data heterogeneity of natural geologic formations strongly influences groundwater flow and contaminant migration this study presents a formal stochastic approach for the integration of surface seismic data and well data into the identification of the spatial arrangement location geometry and interconnectedness of lithofacies and incorporating this information in the estimation of the log permeability probability density function pdf to achieve this goal normal move out nmo corrections are applied to the seismic reflection data to estimate interval seismic velocities calibration curves constructed from the well logs transform these velocity estimates into a lithology indicator prior probability field from the well data and the indicator prior probability field the indicator covariance function and its associated confidence limits are computed neighboring lithology logs and the indicator covariance function are then combined to update the indicator probability field the conditional log permeability pdf is finally computed by weighting the log permeability distribution of each lithology with respect to its indicator probability field the effectiveness of the proposed procedure is shown to depend on the quality of the seismic data and the degree of correlation between seismic and hydrogeologic soil properties a synthetic case study is performed which shows that the surface seismic and well data complement each other with optimal results achieved when both types of data are incorporated into a joint identification procedure

variations in sediment texture on the northern monterey bay national marine sanctuary continental shelf abstract the storm protected continental shelf of monterey bay part of the monterey bay national marine sanctuary north central california is subject to abundant episodic sediment input from fluvial sources north of monterey bay conditions of reduced sediment supply combined with the exposed nature of the shelf provide an effective laboratory for studying the contrasting effects of storm versus fluvial dominated conditions on modern sedimentation textural analyses performed on surface sediment samples collected from more than 380 box cores and multicores document the existence of a clearly defined mud belt occupying the mid shelf throughout the region inshore sands combined with these mid shelf muds represent deposits from modern sedimentation processes in monterey bay where episodic fluvial input from winter storms dominates sedimentation the mid shelf mud belt extends across the shelf to the shelf break north of monterey bay where sediment loads are reduced and both oceanographic and storm processes dominate the mid shelf mud belt is bordered by relict sediments occupying the outer shelf in the study area mass accumulation rates established by radiochemical studies support the contention that storm induced along shelf processes result in northward transport of sediment within the mud belt the continuity of transport however is interrupted by topographic highs which are barriers or inhibitors to sediment transport created by wrench style tectonics associated with the san andreas fault system

sand dynamics at the mouth of a rock bound tide dominated estuary abstract the lowermost kennebec river is a relatively narrow deep bedrock cut estuary situated along the highly indented central coast of maine a large tidal prism and strong tidal currents control bedload sediment transport at the estuary mouth riverine sediment is introduced to the estuary during spring freshets when freshwater discharge may increase by an order of magnitude during the same time some of the existing estuarine sediment is exported to the nearshore a barrier adjacent to the estuary is the product of an abundant riverine sand supply and numerous bedrock ridges which anchor this sand deposit a variety of sedimentologic geomorphic and hydraulic data collected over a 14 year period document a clockwise sand circulation cell that involves the exchange of bedload among the entrance channel to the estuary adjacent beaches nearshore and offshore region tidal currents transport sand from the estuary through a subsidiary channel bordered on both sides by bedrock islands to an offshore subtidal bar northeast storm waves breaking along this outer bar move sand westward and landward toward the beach leading to the development of large bar complexes the welding of a bar complex to the western end of hunnewell beach occurs every 6 9 years and adds 2 300 000 m3 of sand to the shoreline sediment transport calculations along the outer bar are consistent with this volume of sand the sediment gyre is completed as beach sands are moved eastward along the beach and dumped into the estuarine channel this movement of sand is produced by wave action and tidal currents that enter the estuary peripherally during the flooding tide during the ebb cycle strong tidal currents flowing seaward through the subsidiary channel advect water from along the beach which enhances sand transport into the estuary thirteen years of beach profile surveys demonstrate a good correspondence between bar welding events and short term 1 4 years accretionary shoreline changes however the volumetric changes of hunnewell beach cannot be accounted for by bar welding alone the apparent movement of sand between hunnewell beach and other sand is further evidenced by the 135 year record of historical shoreline changes that reveal up to 200 m of shoreline excursions over a 26 year period these data suggest that erosional depositional trends along hunnewell beach are complex and the result of the exchange of sand among the adjacent beaches nearshore zone fox and wood island tombolos kennebec river channel and offshore region the effects of major spring floods and strong bedrock influences produce patterns of sedimentation and a distribution of sand bodies at the mouth of kennebec river that differ markedly from accepted estuarine models that are based on the relative importance of wave and tidal energy this study demonstrates the need to consider structural controls when using these models

geophysical hydrological identification of field permeabilities through bayesian updating a new bayesian method is developed to identify the spatial distribution of permeabilities in addition to sparsely sampled permeability and pressure data this approach incorporates densely sampled seismic velocity data along with semiempirical relationships between seismic and hydraulic soil properties the procedure consists first of performing a hydrological inversion based solely on the permeability and pressure data in light of the available seismic data the velocity permeability pressure relationships are then used to update in a bayesian sense the image of the permeability field to investigate the usefulness of this approach synthetic case studies are performed these studies demonstrate that even when the seismic data are corrupted by a significant level of error a joint geophysical hydrological inversion can produce improved images of permeability moreover this paper derives rigorously the bounds on the error that can be tolerated in seismic velocities such that they are still useful for hydrological purposes

towards a sediment budget for the santa cruz shelf a conceptual model is presented for the northern monterey bay continental shelf in which coarse sediment moves southward along the coast in the littoral zone while fine sediment moves to the north by advection and diffusion along the midshelf data from measurements and estimates of various sediment sources and sinks show that the midshelf mudbelt is the dominant sink for fine grained sediment introduced into monterey bay the principal sources of the fine sediment are the three rivers that enter monterey bay the san lorenzo pajaro and salinas rivers accumulation rates in the midshelf mudbelt are high relative to documented yields of rivers and cliff erosion and also are high relative to other documented mud accumulations of the west coast continental shelves

dramatic beach and nearshore morphological changes due to extreme flooding at a wave dominated river mouth abstract record flooding on the santa clara river of california usa during january 2005 injected 5 million m3 of littoral grade sediment into the santa barbara littoral cell approximately an order of magnitude more than both the average annual river loads and the average annual alongshore littoral transport in this portion of the cell this event appears to be the largest sediment transport event on record for a southern california river over 170 m of local shoreline mean high water mhw progradation was observed as a result of the flood followed by 3 years of rapid local shoreline recession during this post flood stage linear regression determined shoreline change rates are up to 45 m a 1 on the subaerial beach mhw and 114 m a 1 on the submarine delta 6 m isobath starting approximately 1 km downdrift of the river mouth shoreline progradation persisted throughout the 3 year post flood monitoring period with rates up to 19 m a 1 post flood bathymetric surveys show nearshore 0 to 12 m depth erosion on the delta exceeding 400 m3 m a 1 more than an order of magnitude higher than mean seasonal cross shore sediment transport rates in the region changes were not constant with depth however sediment accumulation and subsequent erosion on the delta were greatest at 5 to 8 m and accretion in downdrift areas was greatest above 2 m thus this research shows that the topographic bulge or wave of sediment exhibited both advective and diffusive changes with time although there were significant variations in the rates of change with depth the advection and diffusion of the shoreline position was adequately reproduced with a simple one line model although these modeling techniques miss the important cross shore variations observed in this area this study illustrates the importance of understanding low frequency high volume coastal discharge events for understanding short and long term sediment supply littoral transport and beach and nearshore evolution in coastal systems adjacent to river mouths

reductions in fluvial sediment discharge by coastal dams in california and implications for beach sustainability abstract the long term sustainability of california s beaches depends on periodic deliveries of sand and gravel from coastal rivers and streams to assess the long term health of california s beaches this study characterized the current state of fluvial sediment delivery and quantified on a littoral cell basis the cumulative impacts of dams in decreasing annual discharge presently more than 500 dams impound more than 42 000 km2 or 38 of california s coastal watershed area flow modeling suggests that by diminishing flood hydrographs these dams have reduced the average annual sand and gravel flux to 20 major littoral cells by 2 8 million m3 yr or 25 in 70 of the streams considered in this study suspended sediment loads during equivalent discharge events have declined over the past three decades which indicates that dams have also significantly reduced downstream sediment supplies approximately 23 or 274 km of the 1193 km of beaches in california are downcoast from rivers that have had s

sand dispersion from an ephemeral river delta on the central california coast abstract an ephemeral river delta on the wave dominated central california coast was studied to determine how and when river sand was incorporated into the longshore transport regime the delta at the mouth of the san lorenzo river was built in january 1982 by a 30 year flood records of river flow sediment load and channel volume were used to estimate the river sediment yield repeated topographic surveys of the delta and surrounding beaches confirmed the estimates of river yield and traced sand movement from the river mouth directional wave data confirmed the direction of longshore sand movement and identified sites of erosion and accretion due to divergence in the longshore transport most sand delivered to the delta in flood was deposited seaward of the surfzone about a quarter of this sand was returned shoreward each summer by swell for a time wave refraction across the submerged delta trapped the river sand and littoral drift from upcoast on the delta limiting the sand supply to the beaches downcoast as storm waves broadened the delta refraction lessened and the river sand began to disperse alongshore longshore dispersion was assisted by seasonal cross shore movements directly through a net longshore creep and indirectly through the return of sand from offshore to the surfzone transport the overall pattern of river sand dispersion was that of a low amplitude sandwave

interpretation of drill core and georadar data of coarse gravel deposits abstract pollution in the shallow subsurface has led to an increasing need of understanding how to quantitatively characterize both the heterogeneity of gravel aquifers and the influence of heterogeneity on groundwater flow and solute transport models play an important role in decision making processes especially in the context of better characterizing and in forecasting the behavior of a given geological system the objective of the present paper is the derivation of a gradual lithofacies based interpretation of outcrop drill core and ground penetrating radar gpr or georadar data of different quality the presented method allows a probability estimation of drill core layer descriptions and radarfacies types representing defined sedimentary structure types the method includes a determination of initial structure type probabilities for grain size categories and combinations thereof described in drill core layer descriptions as well as a subsequent differentiation of these structure type probabilities in an iterative process considering additional information like main constituent quantity fraction and sorting of single grain size categories color chemical precipitation layer thickness and adjacent layer the radarfacies types are calibrated with drill cores located in the vicinity of georadar sections the calibration process consists of the assignment of the calculated structure type probabilities from the drill core layer descriptions to the corresponding radarfacies types considering the proportion in thickness between drill core layers and georadar structures the structure type probabilities can be given for points along boreholes and a grid with arbitrary mesh size along georadar sections the method is applied to field examples from the rhine wiese aquifer near basel in switzerland the resulting structure type probabilities can be used for conditioning stochastic simulations of geological models however the conditioned stochastic simulation of the rhine wiese aquifer is the topic of another paper the results show the importance of a detailed sedimentological analysis of outcrops and drill cores as well as its significance on the distinction of sedimentary structure types

spatial correlation structure estimation using geophysical and hydrogeological data the large spatial variability of hydraulic properties in natural geologic systems over a wide range of scales and the difficulty of collecting representative and sufficient hydraulic property measurements using conventional sampling techniques render estimation of spatial correlation parameters difficult further compounding the estimation problem is the observation that the integral scale estimate is a function of the measurement support scale to mitigate these problems we investigate the use of tomographic geophysical data in combination with hydrogeological data in the spatial correlation estimation procedure two synthetic case studies were investigated where the scale of the geophysical measurements were varied relative to the scale of the hydrogeological properties the spatial correlation structure parameter estimation procedure was performed in the spectral domain where analysis of data having different support scales and spatial sampling windows was facilitated comparison of the spatial correlation structure parameters estimated from measured data with those of the synthetic aquifers revealed which type of data tomographic hydrogeological or a combination of both was most effective for recovering spatial correlation statistics under different sampling heterogeneity conditions these synthetic case studies suggest that collection of a few tomographic profiles and interpretation of these profiles together with limited well bore data can yield correlation structure information that is otherwise obtainable only from extensive hydrological sampling

time lapse inversion of crosswell radar data the combination of differential radar tomography with conventional tracer and or hydraulic tests facilitates high resolution characterization of subsurface heterogeneity and enables the identification of preferential flow paths in dynamic imaging each tomogram is typically inverted independently under the assumption that data sets are collected quickly relative to changes in the imaged property e g attenuation or velocity however such snapshot tomograms may contain large errors if the imaged property changes significantly during data collection acquisition of less data over a shorter time interval could ameliorate the problem but the resulting decrease in ray density and angular coverage could degrade model resolution to address these problems we propose a new sequential approach for time lapse tomographic inversion the method uses space time parameterization and regularization to combine data collected at multiple times and to account for temporal variation the inverse algorithm minimizes the sum of weighted squared residuals and a measure of solution complexity based on an a priori space time covariance function and a spatiotemporally variable mean we demonstrate our approach using a synthetic 2 d time lapse x z t data set based loosely on a field experiment in which difference attenuation radar tomography was used to monitor the migration of a saline tracer in fractured rock we quantitatively show the benefits of space time inversion by comparing results for snapshot and time lapse inversion schemes inversion over both space and time results in superior estimation error model resolution and data reproduction compared to conventional snapshot inversion finally we suggest strategies to improve time lapse cross hole inversions using ray based inversion constraints and a modified survey design in which different sets of rays are collected in alternating time steps

compressional velocity and porosity in sand clay mixtures laboratory measurements of porosity and compressional velocity were conducted on unconsolidated brine saturated clean ottawa sand pure kaolinite and their mixtures at various confining pressures a peak in p velocity versus clay content in unconsolidated sand clay mixtures at 40 percent clay by weight was found the peak in velocity is 20 30 percent higher than for either pure clay or clean sand a minimum in porosity versus clay content at 20 40 percent clay by weight is also observed such behavior is explained using a micro geometrical model for mixtures of sand and clay in which two classes of sediments are considered 1 sands and shaley sands in which clay is dispersed in the pore space of load bearing sand and thus reduces porosity and increases the elastic moduli of the pore filling material and 2 shales and sandy shales in which sand grains are dispersed in a clay matrix for these sediments the model reproduces the extrema in velocity and porosity and accounts for much of the scatter in