dune recovery after storm erosion on a high energy beach vougot beach brittany france abstract on 10th march 2008 the high energy storm johanna hit the french atlantic coast generating severe dune erosion on vougot beach brittany france in this paper the recovery of the dune of vougot beach is analysed through a survey of morphological changes and hydrodynamic conditions data collection focused on the period immediately following storm johanna until july 2010 i e over two and a half years results showed that the dune retreated by a maximum of almost 6 m where storm surge and wave attack were the most energetic dune retreat led to the creation of accommodation space for the storage of sediment by widening and elevating space between the pre and post storm dune toe and reducing impacts of the storm surge dune recovery started in the month following the storm event and is still ongoing it is characterised by the construction of secondary embryo dunes which recovered at an average rate of 4 4 5 cm per month although average monthly volume changes varied from 1 to 2 m 3 m 1 these embryo dunes accreted due to a large aeolian sand supply from the upper tidal beach to the existing foredune these dune construction processes were facilitated by growth of vegetation on low profile embryo dunes promoting backshore accretion after more than two years of survey the sediment budget of the beach dune system showed that more than 10 000 m 3 has been lost by the upper tidal beach we suggest that seaward return currents generated during the storm of 10th march 2008 are responsible for offshore sediment transport reconstitution of the equilibrium beach profile following the storm event may therefore have generated cross shore sediment redistribution inducing net erosion in the tidal zone

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

relationship between beach morphodynamics and equilibrium profiles in this paper a new beach equilibrium formulation that treats the shoaling portion of the profile independently from that of the breaking portion is proposed the two portions are matched at the breaking point the formulation considers wave reflection from the beach and the tidal variation of the sea level both profiles are represented by a similar expression that depends on two parameters a and c which account for wave dissipation and b and d which account for beach reflection the parameters are then calibrated using over 50 profiles from 13 beaches along the spanish coast

geochemical characterization of selected western canada oils by c5 c8 compound specific isotope correlation csic abstract forty two oils condensates from the western canada sedimentary basin wcsb ranging in reservoir age from devonian to cretaceous are compared using the stable carbon isotopic ratio of individual hydrocarbons in the gasoline range fraction c 5 c 8 of these oils continuous flow isotope ratio mass spectrometry cf irms using a modified solid dilution purge and trap inletting system can provide reproducible isotopic ratios for the ca 26 dominant n iso and cyclo alkanes and aromatics in the gasoline range the resulting isotopic signatures or gasoline isotopograms for oils condensates provide a diagnostic geochemical technique for oil oil and oil source correlations in many instances the non straight chained hydrocarbons are more diagnostic than n alkanes hierarchical cluster analysis provides a non subjective approach to the treatment of individual isotopic information this study confirms that oils from similar or the same sources produce isotopic signatures that are highly correlated clear carbon isotopic relationships between individual hydrocarbon compounds in the oils suggest a steady state kinetic relationship for the generation of oil and gas as opposed to a thermodynamic equilibrium relationship this mechanism explains the consistent shift in isotopic ratios between similar compounds such as the methylalkanes and dimethylalkanes

coupled barrier island resort model 1 emergent instabilities induced by strong human landscape interactions 1 as humans increasingly occupy and modify marginal landscapes previously unobserved long timescale emergent behaviors related to interactions between natural processes and human agency are possible barrier islands which are low lying strips of sand separated from a coast by lagoons cut by inlets and topped by sand dunes have been significantly modified through the development of tourist resorts resorts and barrier islands are dynamically coupled through storm damage and beach erosion and measures taken to prevent or mitigate them in response to rising sea level a natural barrier island migrates steadily up the continental shelf in contrast we show that in a novel numerical model coupling barrier island processes with resort development storm damage and hazard mitigation policy decisions driven by market dynamics destabilize barrier island response to rising sea level giving rise to emergent episodic boom and bust cycles which alternate in phase alongshore and less frequent regionally extensive resort destruction events developed barrier islands are precariously maintained at lower elevations and further offshore than their natural counterparts a situation exacerbated by insurance which can lead to island inundation our results suggest that coastal areas that have recently instituted protection measures eventually will experience a widespread upsurge in damage if these practices are sustained even in the absence of climate change induced increased storminess

prediction of cross shore sediment transport at different spatial and temporal scales abstract coastal sediment transport and associated morphological change can be examined at many spatial and temporal scales these scales range from instantaneous movement of single grains on a time scale of the local turbulence to seasonal and long term movement of large sand bodies such as longshore bars and tidal deltas researchers have begun to recognize that a first principles microscale approach to calculating long term and large scale megascale coastal change may not be possible or even adequate therefore new approaches are being sought to advance quantitative understanding and prediction of large scale coastal behavior the present paper opens with a discussion of compatible spatial and temporal scales for calculating sediment transport and morphology change motivation is given for the need to calculate morphologic change at scales greater than the typical one of microscale example calculations are made at different scales showing the assumptions and approximations of each the main conclusion is that calculations at different scales can be related and reconciled if limitations in prediction of initial and boundary conditions and in the fluid forcing are recognized

evaluation of depth of closure using data from duck nc usa using 12 years of frequent high precision profiles collected on a wave dominated sandy oceanic beach to 8 m depth the characteristics and interpretation of depth of closure or the seaward limit of significant profile change is critically examined this includes evaluation of the predictive capability of d1 the seaward boundary of the littoral zone as originally defined by hallermeier 1981 hallermeier r j 1981 a profile zonation for seasonal sand beaches from wave climate coastal eng 4 253 277 depth of closure during major erosional events is usually produced by the seaward limit of offshore bar movement following the original recommendation of hallermeier 1981 d1 based on 12 h exceeded wave height and a reference depth of mean low water provides a robust limit to the observations using a 6 cm change criterion empirically the observed depth of closure is 69 of d1 although the scatter is large this scatter is partly controlled by pre event profile shape most particularly bar configuration depth of closure under accretional conditions can also be measured but it is time scale dependent as accretion is a slow steady process d1 underpredicts closure for accretional situations time interval e g annual depth of closure represents the integral effect of erosional and accretional events an important observation of the data is that depth of closure increases with time scale however the full population of time interval observations is not resolved at duck due to the measurement limit 8 m depth as time interval increases from 1 year to 8 years less cases close most non closing time interval cases coincide with the periods influenced by the most energetic wave events however time interval closures are generally deeper than the biggest event closure in the period showing that it represents more than the largest event the frequency distribution of the data suggests that most if not all of these missing data simply represent closures deeper than 8 m depth up to a 4 year time interval d1 t appears to provide a reasonable limit to the quantified observations it is an interesting result that d1 an event based approach might provide a limit to closure over periods up to 4 years as these time interval closures are generally larger than those produced by single storms therefore the general applicability of this result for more complete data sets or on rapidly evolving i e eroding or accreting coasts is uncertain the present data also suggest that on swell dominated coastlines where accretional processes are dominant d1 may underpredict closure suggesting an important limitation to this approach but as sediment would be moving onshore this may not be a practical problem therefore within the limits of the data set hallermeier s 1981 approach is found to define robust estimates of depth of closure particularly for individual erosional events this useful result is expected to find widespread application in coastal geology and engineering

decadal scale variation in dune erosion and accretion rates an investigation of the significance of changing storm tide frequency and magnitude on the sefton coast uk abstract monitoring of frontal dune erosion and accretion on the sefton coast in northwest england over the past 50 years has revealed significant spatial and temporal variations previous work has shown that the spatial variations primarily reflect longshore differences in beach and nearshore morphology energy regime and sediment budget but the causes of temporal variations have not previously been studied in detail this paper presents the results of work carried out to test the hypothesis that a major cause of temporal variation is changes in the frequency and magnitude of storms surges and resulting high tides dune toe erosion accretion records dating from 1958 have been compared with tide gauge records at liverpool and heysham relatively high dune erosion rates at formby point 1958 1968 were associated with a relatively large number of storm tides slower erosion at formby and relatively rapid accretion in areas to the north and south occurred during the 1970 s and 1980 s when there were relatively few major storm tides after 1990 rates of dune erosion at formby increased again and dunes to the north and south experienced slower accretion during this period high storm tides have been more frequent and the annual number of hours with water levels above the critical level for dune erosion has increased significantly an increase in the rate of mean sea level rise at both liverpool and heysham is evident since 1990 but we conclude that this factor is of less importance than the occurrence of extreme high tides and wave action associated with storms the incidence of extreme high tides shows an identifiable relationship with the lunar nodal tidal cycle but the evidence indicates that meteorological forcing has also had a significant effect storms and surges in the eastern irish sea are associated with atlantic depressions whose direction and rate of movement have a strong influence on wind speeds wave energy and the height of surge tides however preliminary analysis has indicated only a modest relationship between dune erosion accretion rates and the north atlantic oscillation index

beach and dune erosion during storm surges this paper presents the set up and results of an extensive research programme concerning the erosion of coastal dunes during storm surges a large number of two dimensional and three dimensional mobile bed model tests has been carried out to investigate the process of dune erosion the state of art after a series of small scale tests is summarized attention is focussed on large scale tests carried out in the delta flume with random waves up to 2 m significant height sediment concentration and orbital velocity measurements are discussed the large scale tests have confirmed the validity of a modelling technique based on the dimensionless fall velocity parameter h tw the model results are being applied to check the safety of existing coastal dunes as a water retaining structure that has to protect the major part of the netherlands from inundation during storm surges

an analytical model to predict dune erosion due to wave impact an analytical model is developed to calculate recession distance and eroded volume for coastal dunes during severe storms the transport relationship used in the model is based on wave impact theory where individual swash waves hitting the dune face induce the erosion combining this relationship with the sediment volume conservation equation describes the response of the dune to high waves and water levels four different data sets on dune erosion originating from the laboratory and the field were employed to validate the model and to determine the value of an empirical transport coefficient appearing in the analytical solutions the time evolution of dune recession observed in the different data sets was well described by the model but the empirical coefficient showed some variation between cases especially for the field data in practical applications of the model it is recommended to use a range of coefficient values to include an uncertainty estimate of calculated quantities such as recession distance and eroded volume

quantifying thresholds for significant dune erosion along the sefton coast northwest england abstract field and model hindcast data are used to establish a critical dune erosion threshold for the sefton coast nw england events are classified as causing significant erosion if they result in a a mean dune retreat along the entire study area of 2 m b a dune retreat of 5 m along a coastal segment 2 km in length and c an eroded area 20 000 m2 for the period 1996 to 2008 individual storms were characterised using hindcast results from a polcoms wam model and measured data from the liverpool bay coastal observatory results show that combined extreme surge levels 1 5 m and wave heights 4 m or tidal water levels above 9 0 m chart datum cd do not always result in significant dune erosion evidence suggests that erosion is more likely to occur when wave heights are 2 6 m peak water level is 10 2 m cd at liverpool and when consecutive tidal cycles provide 10 h or more of water levels above 9 4 m cd however lower water levels and wave heights and shorter events of sustained water levels can cause significant erosion in the summer while the return period for events giving rise to the most severe erosion in the winter is 50 years significant erosion in the summer can be caused by events with return periods

swash zone sediment transport and foreshore evolution field experiments and mathematical modeling data from field experiments carried out in the swash zone on two pacific beaches in japan were analyzed to determine net sediment transport rates and the resulting foreshore response the experiments involved artificial modification of the foreshore slope with a bulldozer either making the slope steeper or milder after which a wide range of measurements were performed as the slope evolved back towards its equilibrium value under the action of the incident waves a sediment transport formula was developed to predict the net transport rate over many swash cycles and compared with the derived transport rates from the surveys of the foreshore this formula was then combined with the conservation equation for sediment volume to yield a mathematical model for simulating the foreshore evolution under varying waves and water level predictions by the model were compared to measurements yielding satisfactory agreement although the optimum values on the main calibration coefficient displayed some variation between experiments further analysis of a limited number of cases indicated that this coefficient may be dependent upon the ratio between the incident wave period and the swash period which characterizes the interaction between individual waves in the swash zone a simple analytical solution was also derived for a schematized foreshore shape to estimate the typical time scale of the morphological response

stratification produced by surface cooling in lakes with significant shallow regions a reservoir with distinct shallow and deep regions can produce stratification in response to uniform surface heat loss the shallow region cools more rapidly and a cold dense gravity current forms that results in stratification at the base of the deep region and an upwelling of cold water the surface mixed layer deepens by convective entrainment and a steady mixed layer depth can result when the cold upwelling balances the rate at which the mixed layer deepens the steady depth of the mixed layer depends on the ratio of the area of the shallow region to the area of the deep region significant stratification only results when the reservoir has shallow regions that account for more than 50 of the surface area the depth of the surface mixed layer also depends on the ratio of the depths of the shallow and deep regions and no significant stratification can form if this ratio is greater than 0 5 for a wedge shaped geometry these observations can be generalized by considering the ratio of the average depth to the maximum depth in a reservoir the gravity current can produce stratification in more than 50 of the depth when this ratio is less than 0 5 results from a laboratory study and field data from chaffey reservoir australia are presented on the surface mixed layer depth along with estimates of the time scales needed for atmospheric forcing to lead to the development of stratification

observations of sand bar evolution on a natural beach waves currents and the location of the seafloor were measured on a barred beach for about 2 months at nine locations along a cross shore transect extending 255 m from 1 to 4 m water depth the seafloor location was measured nearly continuously even in the surf zone during storms with sonar altimeters mounted on fixed frames the crest of a sand bar initially located about 60 m from the shoreline moved 130 m offshore primarily when the offshore significant wave height exceeded about 2 m with 1 5 m of erosion near the initial location and 1 m of accretion at the final location an energetics type sediment transport model driven by locally measured near bottom currents predicts the observed offshore bar migration but not the slow onshore migration observed during low energy wave conditions the predicted offshore bar migration is driven primarily by cross shore gradients in predicted suspended sediment transport associated with quasi steady near bottom offshore flows these strong 50 cm s currents intensified near the bar crest by wave breaking are predicted to cause erosion on the shoreward slope of the bar and deposition on the seaward side the feedback amoung morphology waves circulation and sediment transport thus forces offshore bar migration during storms

modeling dune response to an east coast low coastal dunes can act as a method of soft coastal protection against inundation and direct impact of waves during storms if they are substantially large enough in volume to withstand erosion without breaching however the time evolution of sand dunes under direct wave impact is not well understood and many available models require site specific calibration and have had limited verification at field scales here we test three models of varying complexity in their ability to predict both dry beach erosion volumes and dune to a retreat for an east coast low storm event that occurred on the gold coast australia the process based model xbeach which models the entire profile was able to reproduce both dune toe retreat and dry beach volume however was sensitive to calibration parameters the two parametric models that only modeled erosion above the initial dune toe position were capable of accurately predicting dune toe retreat however under estimated dry beach erosion volumes with no calibration the parametric model proposed by palmsten and holman 2012 produced the smallest errors of dune toe retreat with mean error in final dune position of 6 6 m or 18 of the total measured dune retreat with minimal calibration estimated absolute error in average dune toe retreat was less than 13 of observed retreat for all three models

development of a medium long term beach evolution model abstract a new medium long term beach evolution model is proposed this model is based on an analytically integrated sediment conservation equation and on a beach profile evolution model the sediment conservation equation provides the sediment supplies or losses the beach profile evolution model redistributes the sediment supplies or losses along the beach profile in the beach profile evolution model the definition of the complete profile is incorporated breaking zone transition zone exterior zone and geological zone the proposed model has been applied to several theoretical cases and to field data showing the advantages of this model compared to classical one line models

evolution of a beach dune system following a catastrophic storm overwash event greenwich dunes prince edward island 1936 2005 greenwich dunes prince edward island national park is a sandy mainland and barrier spit beach dune complex stretching for about 10 km along the northeast shore of prince edward island canada in october 1923 surge associated with an intense storm produced catastrophic overwash along the whole length of the study area subsequent evolution of the system was quantified from historic aerial photographs taken in 1936 1953 1971 1997 and 2005 orthophoto mosaics were generated for each photo set using pci geomatica orthoengine a digital photogrammetric software linear changes in shoreline position and areal changes in geomorphic units were evaluated for each photo set in addition digital elevation models dems were extracted from the 1953 1971 and 1997 aerial photos enabling analysis of topographic and volumetric changes the 1936 photos show complete destruction of all foredunes with overwash and transgressive dunes extending 300 to 600 m inland a descriptive model of the stages of evolution

littoral sediment transport and shoreline changes along ennore on the southeast coast of india field observations and numerical modeling abstract the newly constructed port in 2001 at ennore on the southeast coast of india near chennai with breakwaters on either side north and south has been causing large scale changes in nearshore morphology beach profiles and shoreline positions along 25 km coastline of ennore were measured at regular intervals during 2001 06 to understand the sediment transport patterns in the region at the same time the results of wave hind casting and wave transformation modeling were incorporated in litdrift model to compute the sediment transport rates along ennore coast the model results are compared with the sediment transport values obtained from beach profile measurements the performance of the model at different locations within the study area with variable wave conditions has been examined the annual net sediment loss versus accumulation were estimated for two smaller study areas cells containing ten regularly spaced beach profiles numbered from north to south bp1 5 in cell i and bp6 10 in cell ii for the cell i region which is protected by the ennore shoals and where human interference is minimum the annual net sediment supply is 0 02 106 m3 as obtained from beach profile measurements while the model gave a value of 0 014 106 m3 for the cell ii region where there is large human intervention by way of ennore port development and breakwater construction the annual net sediment movement as obtained by the beach measurements is 0 14 106 m3 while the model gave a value of 0 154 106 m3 it is found that the performance of the model is satisfactory and the model may be used successfully to study sediment dynamics along any coastline provided one has detailed understanding of the coastline orientation nearshore topography cross shore bathymetry and prevailing annual wave climate based on the sediment transport data and beach profile measurements the beach and shoreline changes for transect locations bp 1 to bp 10 are also critically examined in this paper

an equilibrium model to predict shoreline rotation of pocket beaches a novel and simple beach evolution model for estimating shoreline rotation at sandy pocket beaches is presented the model is based on the assumption that the instantaneous changes to the planview shape of the shoreline depend on the long term equilibrium planview shape two years of shoreline observations extracted from video images of three artificially embayed beaches of barcelona and hourly wave timeseries are used to validate the model numerical model results and field observations show an excellent agreement with an rmse less than 1 5 m the model successfully reproduced the shoreline response over a range of scales months and years because of its simplicity and its computational efficiency the model provides a powerful tool to understand the dynamics regulating the evolution of pocket beaches and predict temporal patterns in beach rotation

morphological hysteresis in the evolution of beach profiles under sequences of wave climates part 1 observations abstract novel series of experiments are presented that demonstrate morphological hysteresis in the evolution to equilibrium of beach profiles under sequences of different wave climates the experiments were conducted in a wave flume at medium scale using both monochromatic and random waves representing 2d conditions beach profiles were obtained with high spatial resolution at frequent intervals with a laser profiler from which shoreline location bar position and sediment transport rates were derived experiments were conducted for sequences of wave climates where a sequence comprised of 6 13 sequential tests each commencing with the beach profile from the preceding test each test was run until equilibrium conditions were obtained and had a constant wave height increased or decreased relative to the preceding test cyclical conditions were also included with erosive and accretive wave conditions of short durations alternating through multiple cycles so that equilibrium conditions were not reached during a test with a sequence of increasing wave heights the relationship between the shoreline position and the bulk cross shore sediment transport at equilibrium was non monotonic indicating a maximum in the landward sediment transport rate for test series comprised of a sequence of increasing wave heights followed by a sequence of decreasing wave heights morphological hysteresis was observed in the equilibrium shoreline position and bulk cross shore sediment transport such that shoreline recession or offshore transport continued in some instances after reductions in wave height this is inconsistent with classical equilibrium type shoreline evolution models however when equilibrium conditions were not reached in the cyclic sequences no such morphological hysteresis was observed and a dynamic equilibrium is reached the morphological hysteresis occurs because of the decay stranding or increased relative depth of the breaker bar following a reduction in wave height often in conjunction with a new breaker bar generated by further offshore transport in the inner surf zone similar sequences of morphological response are evident in field data and larger scale tests in the literature finally it is shown that the morphological hysteresis can be explained using the classical equilibrium beach state model of wright et al 1985 by introducing the concept of a subsequent alternate active beach state which may occur following a change in wave conditions

empirical model of morphodynamic beachface behaviour for low energy mesotidal environments abstract four years of monthly monitoring were carried out on a south atlantic beach in spain in a low energy mesotidal environment where beaches change slowly from reflective to dissipative states following a typical seasonal behaviour in this work a two dimensional study of beach morphological variations has been made related to the incident wave variations after applying several morphodynamic parameters to the field data poor or null representative results were obtained it was then necessary to design other type of characterisation of the incident wave energy in this sense the intertidal normalised beach slope was compared with the erosive potential of the incident waves expressed as a combination of the dimensionless grain fall velocity parameter and the energy density of waves median grain size did not vary significantly during the surveys for this reason a new parameter named wave erosivity factor was introduced by considering the fall velocity of grains as a constant in the parameter the resulting ratio between normalised beach slope and wave erosivity expresses the equilibrium state of the beach for any given energy level the departure from the equilibrium curve is largest in the intermediate situations while at the extremes the points are better adjusted to asymptotic tendencies towards equilibrium on reflective states small increases in the wave erosivity will produce important beach changes on dissipative beaches important increases in the wave erosivity will not produce significant morphological modifications the resulting equilibrium curve is presented as a function of the natural range of morphological variation of this beach

relationship between beach profiles and waves at duck north carolina determined by canonical correlation analysis abstract an 11 year long measurement time series of waves and profiles from duck north carolina was analyzed using canonical correlation analysis cca in order to determine the covariability between waves and profile response the main objectives of this analysis were 1 to detect simultaneously occurring patterns in the wave and profile data and if possible give such patterns a physical interpretation to increase the insight into the governing processes and 2 to investigate the possibility to use cca in a predictive mode with the aim to calculate the profile response from the waves the profile shape itself and the change between consecutively surveyed profiles were correlated with both the offshore deep water and nearshore wave conditions in the offshore the waves were described by composite probability density functions pdf derived based on the measured wave conditions prior to a profile survey nearshore wave conditions were calculated using a random breaker decay model and averaged local wave properties were used as input to the cca the profile response displayed significantly higher correlation with the nearshore wave properties as compared to the offshore waves and the highest correlation was found between the profile shape and the mean ratio of breaking waves for the time period preceding the profile survey the cca using nearshore wave properties indicates a potential for predicting the profile response with an acceptable degree of accuracy once a regression matrix relating the profiles to the waves has been established that represents the typical variability at the site

sedimentary balances land and sea with special reference to the icelandic south coast from torlakshofn to dyrholaey river nourishment of shores practical analogies on artificial nourishment abstract the sedimentary balances between land and sea are discussed with particular reference to the 140 km long pocket beach between two major headlands on the sandy icelandic south coast rivers supply large quantities of material to the coast comparing the known transport of material by the rivers to the area of the continental shelf and using the recorded sea level rise at the port of reykjavik a balance was found the development of equilibrium profiles in relation to profile geometry grain sizes and outer boundaries for material movement by wave action is discussed and practical suggestions on future nourishment procedures are presented profile nourishment will be more practical and economical than beach nourishment

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

numerical simulation of time dependent beach and dune erosion a computational procedure is developed for predicting the time dependent two dimensional beach and dune erosion during severe storms due to elevated water levels and waves the model employs the equation of sediment continuity and a dynamic equation governing the cross shore sediment transport due to a disequilibrium of wave energy dissipation levels these equations are solved numerically by an implicit double sweep procedure to determine the change in position of elevation contours in the profile given sufficient time the profile will evolve to a form where the depth h in the surf zone is related to the distance seaward of the waterline by the relationship h ax23 which is consistent with many natural profiles and in which a depends on sediment characteristics the model is verified qualitatively and quantitatively through application to several idealized cases and through a preliminary simulation of erosion during hurricane eloise in general the time scales for shoreline response were found to be quite long relative to natural storm systems and erosion in the early response stages was found to be sensitive to storm surge height but much less sensitive to wave height the model response characteristics for simulation of erosion due to time varying storm conditions show a lag between the maximum storm surge elevation and maximum erosion with the maximum erosion rate occurring at the time of the peak surge for the simulated erosion due to hurricane eloise reasonable agreement was found between the post hurricane dune profiles and those calculated however the eroded volumes were in better agreement than the profile forms as the steepening of the natural dune profiles was not reproduced in the model

annual to decadal morphodynamics of the foredune system at greenwich dunes prince edward island canada the purpose of this study was to quantify relationships between season sediment availability sediment transport pathways and beach foredune morphology at greenwich dunes pei this was done for periods ranging from a few days to multiple decades using erosion pins bedframe measurements annual surveys and digital photogrammetry using historical aerial photographs the relative significance of seasonal annual processes versus response of the foredune system to broader geomorphic controls e g relative sea level rise storms etc was also assessed the data show that there are clear seasonal differences in the patterns of sand supply from the beach to the foredune at greenwich and that there are differences in sediment supply to the foredune between the east and west reaches of the study area resulting in ongoing differences in foredune morphology they also demonstrate that models that incorporate wind climate alone or even models that include other factors like beach moisture would not be able to predict the amount of sediment movement from the beach to the foredune in this environment unless there were some way to parameterize system morphology especially the presence or absence of a dune ramp finally the data suggest that the foredune can migrate landward while maintaining its form via transfers of sediment from the stoss slope over the crest and onto the lee slope although the rate of foredune development or recovery after disturbance changes over time due to morphological feedback the overall decadal evolution of the foredune system at greenwich is consistent with and supports the davidson arnott 2005 conceptual model of dune transgression under rising sea level copyright 2012 john wiley sons ltd

problems in characterizing dynamics of mud shore profiles the relationship between profile shape and wave forcing at shores composed of soft mud is examined at a given still water level the modality of change in profile shape under wave action depends on the fluidization potential of mud which in turn is contingent on the wave characteristics and the dissipative properties of mud an important determinant of profile shape in areas where mud can be fluidized is the wave attenuation coefficient comparatively large values of this coefficient tend to correlate with erosional concave upward profiles and low values with accretionary convex upward shapes assuming that the rate of energy dissipation per unit area of nonbreaking normally incident waves is constant in the nearshore shallow zone an equation to simulate soft mud shore profiles has been developed this equation is shown to be applicable to profile data obtained from a variety of mud shore environments however it is noted that realistic simulations of the accretionary and erosional characteristics

aeolus ii an interactive program for the simulation of aeolian sedimentation abstract a computer program has been developed to simulate two or three dimensional topographic change associated with aeolian sediment transport because predictions generated by available models of aeolian transport can vary by about an order of magnitude for a given set of environmental conditions selection of an appropriate model is problematic this program includes a number of models and provides for interactive selection of a desired model combination s to allow for comparison between model predictions topography represented by a set of coordinates in two or three dimensions is defined by bins of sediment differential rates of transport between adjacent bins resulting from variations in grain size slope and surface moisture content are used to determine mass flux and to adjust the topography in an iterative fashion sub routines allow the simulation of temporally varying levels of surface moisture resulting from evaporation and periodic restoration of upwind boundary conditions the wind field can be represented by a constant shear velocity by a spatial cross shore distribution of shear velocities or by a time series of values representing multiple wind events output is in the form of a graphic display or tabulated results written to disk example results are presented which qualitatively suggest that simulated topographic changes are reasonable areas where further refinement is needed to improve correspondence with reality are identified and discussed

equilibrium beach profile model for perched beaches abstract a beach profile equilibrium model for perched beaches is presented the model assumes that wave reflection at the seaward and leeward sides of the breakwater is the most important process that modifies dean s equilibrium profile model for non perched beaches the influence of wave breaking over the submerged structure is also discussed several laboratory data sets are used to analyze the merit of the proposed model for describing the equilibrium condition of a perched beach a good comparison is obtained results show that if the ratio between the water depth above the submerged structure d and the water depth at the toe of the structure h e is large d h e 0 5 only minor advance of the shoreline is achieved with the construction of a toe structure a considerable advance is obtained for d h e less that 0 1 in these situations however resonant effects may result in an inefficient structure the proposed model is used to provide an estimation for the required sand volume and the associated beach advance for the case of narrow breakwaters

laboratory investigation of dune erosion as a function of sand grain size and dune density abstract the relationship between swash force sand grain size dune density and dune erosion was investigated in a series of laboratory experiments the sands selected for the experiments were a coarse grain sand from north carolina and a fine grain sand from oregon small scale dunes were built and characterized as either high or low density the swash was modeled as a bore which was generated using a head tank the data consisted of bore height bore velocity specific volume eroded and dune density for ninety seven individual tests these data were analyzed using maximum likelihood estimation mle and likelihood ratio lr test methods the conclusions are 1 swash force and dune erosion are related linearly 2 decreasing the sand grain size of the dune decreases the amount of dune erosion for the same swash force and 3 increasing dune density decreases the amount of dune erosion for the same swash force in addition for these test data the difference in sand grain size influences the amount of dune erosion for a given swash force more than that due to the increase in dune density

mathematical modeling of the fate of beach fill abstract this paper describes mathematical approaches for calculating the fate of beach fill under wave action general properties of the spatial and temporal behavior of fills under average longshore sand transport conditions are first reviewed through use of simple closed form solutions of the sediment continuity equation this well known solution procedure is then extended to describe the collective movement of sediment or longshore sand waves because of the increasing use of beach fills as storm protection barriers the paper focuses on prediction of storm induced beach erosion an empirically based model is described and tested with a high quality field data set of storm induced beach erosion one synthetic tropical storm and one synthetic extratropical storm representing typical mid atlantic storms with approximate 2 5 year return period are then used to simulate the erosion of two hypothetical beach fill configurations and the subsequent post storm recovery process eroded volume and contour movement are evaluated as a function of storm type fill cross section grain size and time quantitative and qualitative features of storm erosion are reasonably well reproduced and calculated changes in beach fills impacted by the synthetic storms indicate that little erosion protection benefit is gained for moderate storms 2 5 year return period by placing fills with grain sizes greater than 0 4 mm simulation of post storm beach recovery is presently limited to qualitative reproduction of observed trends

reduction of sand demand for shore protection beach nourishment is an environmentally preferred method of shore protection but the annual sand requirement may lead to substantial maintenance costs the shoreline processes involving the surf zone beach and dune are reviewed with the aim of reducing the annual sand requirement of eroding shorelines it is shown that surf zones with equilibrium profiles on which the wave energy conversion is evenly distributed across the surf zone from experience for given conditions indicate least loss of sand on steep eroding shorelines it may be difficult to establish an equilibrium profile for such cases the use of perched surf zones is recommended which are supported at the seaward limit by an underwater sill for reduction of littoral transport the use of pervious pile groynes is recommended these are arguably more efficient than impervious groynes the sand loss from a usually dry beach by raised water levels is shown to be a function of the beach slope and is least when the storm waves at raised water levels do not cut an erosion escarpment the loss of sand from a dune by infrequent severe storm tides can be prevented with the aid of a built in membrane these sand losses are usually large and constitute an uneconomic use of this sand resource the proposed concepts and measures are linked to existing knowledge augmented by data from the large wave flume lwf in germany and field data from the north and baltic sea coasts

infiltration and instability in dune erosion 1 forecasting dune erosion prior to a storm or over longer periods requires knowledge of the fluid forces on the dune sediments to improve our predictive capability for this process we propose a new model in which dune slumping occurs when water which infiltrates horizontally into the dune increases the overburden sufficiently to destabilize the dune horizontal infiltration is driven by suction of water from swash into the dune via capillary action and is a surprisingly strong process with rapid time scales because the elevated pore water concentrations increase the apparent cohesion of the wetted sediments we also propose that the entire volume of wetted sand slumps as a unit when the dune becomes unstable and erosion can be modeled based on the force balance on a sliding block several versions of this model were tested including a numerical infiltration model a simplified infiltration equation and an equation based on offshore wave forcing rather than known forcing at the dune the model was tested using data from a large scale laboratory experiment with a storm hydrograph to investigate the time dependence of dune erosion predicting slope stability using a numerical infiltration model with known forcing explained 72 of the observed variance in erosion rate while a simplified stability and infiltration model explained 58 error statistics suggest that we captured the majority of the physics controlling dune erosion in this laboratory experiment and that the simplified model will be useful as a forecasting tool

novel particle method for modelling the episodic collapse of soft coastal bluffs abstract this paper presents a new novel particle based bluff morphology model bmm and with it investigates the stability collapse and equilibrium position of soft coastal bluffs cliffs this model combines a multiple wedge displacement method with an adapted weakly compressible smoothed particle hydrodynamics wcsph method at first the wedge method is applied to compute the stability of the bluff once the critical failure mechanism of the bluff slope has been identified and if the factor of safety for the mechanism is less than 1 the adapted wcsph method is used to predict the failure movement and residual shape of the slope the model is validated against benchmark test cases of bluff stability for purely frictional purely cohesive and mixed strength bluff materials including 2d static water tables the model predictions give a good correlation with the expected values with medium resolution models producing errors of typically less than 2 0 in addition the prediction of lateral movement of a surveyed cliff and the dynamic collapse of a vertical bluff are computed and compare well with published literature

a behavior oriented dynamic model for sandbar migration and 2dh evolution 1 a nonlinear model is developed to study the time dependent relationship between the alongshore variability of a sandbar a t and alongshore averaged sandbar position xc t sediment transport equations are derived from energetics based formulations a link between this continuous physical representation and a parametric form describing the migration of sandbars of constant shape is established through a simple transformation of variables the model is driven by offshore wave conditions the parametric equations are dynamically coupled such that changes in one term i e xc drive changes in the other i e a t the model is tested on 566 days of data from palm beach new south wales australia using weighted nonlinear least squares to estimate best fit model coefficients the model explained 49 and 41 of the variance in measured xc and a t respectively comparisons against a 1 d horizontal 1dh version of the model showed significant improvements when the 2dh terms were included 1dh and 2dh brier skill scores were 0 12 and 0 42 respectively onshore bar migration was not predicted in the 1dh model while the 2dh model correctly predicted onshore migration in the presence of 2dh morphology and allowed the bar to remain closer to shore for a given amount of breaking providing an important hysteresis to the system the model is consistent with observations that active bar migration occurs under breaking waves with onshore migration occurring at timescales of days to weeks and increasing 2dh morphology while offshore migration occurs rapidly under high waves and coincides with a reduction in 2dh morphology citation splinter k d r a holman and n g plant 2011 abehavior orienteddynamicmodelforsandbarmigrationand2dh evolution j geophys res 116 c01020 doi 10 1029 2010jc006382

field evidence of beach profile evolution toward equilibrium an equilibrium framework is used to describe the evolution of the cross shore profile of five beaches medium grain size sand in southern california elevations were observed quarterly on cross shore transects extending from the back beach to 8 m depth for 3 10 years transects spaced 100 m in the alongshore direction are alongshore averaged into nineteen 700 900 m long sections consistent with previous observations changes about the time average profile in many sections are captured by the first mode empirical orthogonal function eof the first eof poorly describes sections with hard substrate less than roughly 80 sandy bottom and also fails near the head of a submarine canyon and adjacent to an inlet at the 12 well described sections the time varying amplitude of the first eof the beach state a describes the well known seasonal sand exchange between the shoreline and offshore roughly between 4 and 7 m depth we show that the beach state change rate da dt depends on the disequilibrium between the present state a and wave conditions consistent with the equilibrium concepts of wright and short 1984 and wright et al 1985 empirically determined optimal model coefficients using the framework of yates et al 2009a 2011 vary between sections but a single set of globally optimized values performs almost as well the model implements equilibrium concepts using ad hoc assumptions and empirical parameter values the similarity with observed profile change at five southern california beaches supports the underlying model equilibrium hypotheses but for unknown reasons the model fails at duck nc

behaviour of beach profiles during accretion and erosion dominated periods beach profiles have been surveyed at monthly intervals between 1972 and 1988 at moruya on the south coast of new south wales australia four profile sites have been used as a data set to provide an understanding of changes to beach volume width and shape moruya beach represents a moderately high energy microtidal environment which responds in a dramatic way to major storm events such as those experienced in the mid 1970s this study distinguishes between profile characteristics associated with such a period erosion dominated or edp compared with periods when accretion dominated adp accompanied by foredune expansion in both height and width