morphological change and sediment dynamics of the beach step on a macrotidal gravel beach abstract the morpho sedimentary evolution of a pure gravel beach step over a tidal cycle is examined during fairweather conditions using detailed measurements of nearshore hydrodynamics morphological and sedimentary change and nearshore sediment transport the characteristics of the beach step are analysed with specific reference to the concurrent dynamics of the beachface a departure from previous studies which have treated the step as a feature isolated from the nearshore region as a whole the step and berm are both accretionary features strongly linked to tidal stage yet their temporal evolution is independent the relaxation time of the berm being linked to the spring neap tidal cycle and that of the more transient step linked to the semi diurnal tide over this time scale the beachface is a closed sedimentary unit although the beach step may be differentiated from the beachface using sedimentary moments indeed despite the location of the step in the region of wave breaking it has relatively stable sedimentology remaining characteristically coarser and more leptokurtic than the swash zone co spectral analysis between nearshore bed motion and cross shore current velocity reveals that significant nearshore sediment transport occurs at sub incident frequencies in response to wave groups motion of the nearshore bed is not a linear function of velocity magnitude or direction so it is likely that there is a role for the various mechanical properties of the bed therefore a better description of nearshore sediment transport in the region of the beach step would require instantaneous sediment size information allowing the use of a time variant friction factor

nearshore hydrodynamics beachface cobble transport and morphodynamics on a pacific atoll motu abstract measurements of wave transformation beachface cobble transport and shoreline morphology change were undertaken over a 14 month period at fatato island a cobble and sand motu on the southeast rim of funafuti atoll tuvalu results document significant cobble transport and beach profile change on fatato during a year in the absence of any significant high energy wave events changes in beachface volume were measured on 11 across shore beach profiles and show marked variations of 7 1 and 7 01 m3 between profiles and between survey periods net volumetric beachface change over the 14 month experiment was approximately zero indicating a balance between erosion and deposition and net conservation of sediment volume on the ocean shoreline cobble movement was measured using passive integrated transponder pit tags inserted in 300 randomly selected clasts mean b axis 75 mm on the mid beachface tagged particles were re surveyed after 6 and 14 months achieving 76 recovery and identify large excursions of clasts on the beachface and dominant southwest alongshore transport with an average net movement of 68 m after 14 months a simple agent based probabilistic model was developed to simulate cobble movement and explore the coupling between hydrodynamic and shoreline processes model simulations reveal predominant south westerly cobble transport is driven by mean wave conditions associated with easterly trade winds and long period swell events that approach the reef from the south drive episodic north easterly transport reversals and significant onshore transport that can strand particles on the upper beach results present the first observations of morphodynamic behaviour of an atoll motu and highlight the highly dynamic nature of motu shorelines under mean energy conditions such results challenge conventional perspectives that motu are storm adjusted landforms that require extreme events to stimulate geomorphic change and inform future projections of island change

intertidal beach profile estimation using video images abstract in this paper we present a technique suitable for measurement of intertidal bathymetry over a broad range of length scales 10 1 to 10 3 m and time scales days to decades a series of time averaged images of the swash zone are used to map contour lines of the beach surface in each image contours are identified using bands of maximum brightness associated with breaking waves at the shoreline by mapping the location of these bands in a sequence of images collected over one tidal cycle contour maps of the intertidal bathymetry are generated we expect this technique to work best smallest absolute error under waves which are nearly reflective at the shoreline but break enough to be observed visually this is typical of a barred beach since the wave height at the shoreline is limited by wave breaking over the bar crest the ability of the measurements made with this technique to resolve actual beach elevation variation depends on the ratio of the measurement error variance to the true beach elevation variance thus large measurement errors may be compensated by either large tidal ranges or large temporal changes of the beach itself in a comparison to bathymetry surveyed using a differential global positioning system dgps during the duck94 experiment in duck n c the image based elevation estimates were well correlated with the actual bathymetry the deviations imagebased vs dgps measurements may be partially attributed to effects scaled by wave height at the shoreline wave induced setup and wave height saturation over the sand bar in particular setup was important during dissipative conditions the rms deviation vertical between the dgps and image based bathymetry was reduced from 0 24 m to 0 06 m by correcting for the systematic deviations due to variations in setup and wave height saturation further improvement of the elevation estimates resulted from parameterizing the actual bathymetry with a simple plane beach surface which reduced random or unresolvable measurement errors this led to estimates of the beach slope that were accurate to within 10 of the actual slope and estimates of the cross shore location of the mean sea level line accurate to about 0 50 m

a field based classification scheme for gravel beaches a tripartite classification of gravel beaches based upon morphodynamic properties is proposed and demonstrated for 42 new zealand beaches the main advantage of this scheme is that it is based on simple visual classification that can be applied globally in the field and is underpinned by morphodynamic differences between the beach types the three types identified from the results are 1 pure gravel beach 2 mixed sand and gravel beach 3 composite gravel beach pure gravel beaches have steep slopes tan 0 08 0 24 and gravels extending from the storm berm to below mean low water spring tide level mixed sand and gravel beaches have moderate slopes tan 0 04 0 13 with sand and gravel entirely mixed both cross shore and at depth composite gravel beaches have a steep gravel berm fronted by a low angle intertidal terrace with overall beach slopes of tan 0 05 0 14 on composite beaches there is distinct hydrodynamic cross shore sorting of the sand and gravel component these broad types are tested using discriminant analysis and the three classes are shown to be highly significant f 16 24 df 8 p 0 00005 the key discriminating variables are iribarren number beach width average grain size and storm berm height

observations of gravel beach dynamics during high energy wave conditions using a laser scanner the work described in this publication was supported by the epsrc project arcoes adaptation and resilience of the uk energy system to climate change epsrc reference ep 1035390 1 and by epsrc grant ep h040056 1 in partnership with the channel coastal observatory cco the full text is under embargo until 01 01 16

net sediment transport and morphological change in the swash zone of a high energy sandy beach from swash event to tidal cycle time scales abstract a field experiment was conducted on a high energy sandy beach truc vert france to examine swash zone processes and shoreline erosion accretion in response to changing wave and tide conditions beachface morphological changes were measured at the swash by swash timescale using an array of ultrasonic bed level sensors and at the tidal timescale through total station surveys hydrodynamic and sediment dynamic data were collected using arrays of pressure transducers electromagnetic current meters optical backscatter sensors and total load sediment traps data were collected for 16 consecutive days 33 tides over a spring neap spring tidal cycle with offshore significant wave heights of 1 4 m and periods of 5 12 s the swash motion was predominantly at infragravity wave frequencies over the measurement period the upper beach experienced phases of accretion erosion and stability trapped sediment loads for the uprush and backwash were predicted reasonably well by cross shore velocity skewness but the prediction of net transport over individual swash events by velocity based models was more problematic particularly lower in the swash zone where swash interactions were more prevalent net sediment fluxes over individual swash events often exceeded 100 kg per unit meter beach width and such rates were only one order of magnitude less than the net transport typically experienced across the high tide swash zone over complete tidal cycles upper beach erosion accretion at the tidal timescale was reasonably well predicted by the dean criterion based on offshore wave steepness and dimensionless fall velocity but the beach gradient also played a significant role in controlling the occurrence of erosion and accretion

wave reflection on natural beaches an equilibrium beach profile model waves are the most energetic phenomena that control beach morphology the beach profile mostly depends on the way in which the incident wave energy distributes along the profile dissipation and reflection being the main mechanisms while the dissipation phenomena have been widely studied the effect of wave reflection on the beach profile has attracted much less attention and is still poorly known in order to evaluate its importance a new equilibrium profile model that includes reflection is proposed the model is based on a two section profile scheme largely corresponding to the surf and shoaling dominated zones of the beach profile the obtained formulations are represented by the expression of two terms one of the terms accounts for the dissipation effect and coincides with the dean profile the other term integrates the reflection process the model and its coefficients have been calibrated using measured profiles along the spanish coast the validation shows a significant improvement of the fitting parameters with respect to the most popular equilibrium profiles model moreover additional empirical expressions that relate morphology and hydrodynamic in the equilibrium profile model are also presented in this study as a novel contribution to this topic

application of marine radar to monitoring seasonal and event based changes in intertidal morphology this paper demonstrates the application of marine radar and a newly developed waterline mapping technique to the continued surveillance and monitoring of inter and intra annual intertidal morphological change thus capturing new detail on coastal system behaviours marine radar data from 2006 to 2009 are used to create a sequence of waterline elevation surveys that show clear morphological evolution of two different sites in the dee estuary uk an estimate of volumetric change was made at two locations west hoyle sandbank and the nw wirral beach both sites exhibited a similar cyclic pattern of volumetric change with lowest volumes in autumn and winter respectively the average beach elevations above admiralty chart datum clearly reflect the observed change in sediment volume with reduced elevations in winter and increased elevations in summer suggesting a trend of high energy storm waves in autumn and winter that remove sediment and simultaneously moderate the vertical dimension of bedforms in the intertidal area data at this temporal and spatial scale are not easily obtainable by other current remote sensing techniques the use of marine radar as a tool for quantifying coastal change over seasonal and event timescales in complex hydrodynamic settings is illustrated specifically its unique application to monitoring areas with dynamic morphology or that is vulnerable to erosion and or degradation by storm events is exemplified

wave reflection and saturation on natural beaches the role of the morphodynamic beach state in incident swash abstract in this work we present an analysis of the effect of the processes related to beach morphodynamic state on high frequency incident band swash oscillations the effect of wave reflection and saturation on swash oscillations was assessed based on new field data measured under different morphodynamic conditions on the northern coast of spain data measured under more reflective conditions indicated the occurrence of a cross shore partial standing structure a process which was observed earlier using laboratory and numerical data part of the dataset data showed saturation in accordance to limits between reflection and saturation established in previous works the new measured data was added to a large database compiled from previous works and assuming the hypothesis that the reflection and saturation processes are related to the beach state a new parameterization was established to calculate the incident swash under different morphodynamic conditions our results indicate that the role of the foreshore slope and wave steepness varies according to the morphodynamic beach state the proposed formula showed a reasonable correlation with measured data 2 0 56 and rmse 0 41 m and improvements in s i n c predictions were observed for all beach types when compared to existing formulas

sediment transport associated with morphological beach changes forced by irregular asymmetric skewed waves 1 the waveshape effects on sediment transport are investigated for cross shore beach profile changes this study is based on experiments performed in the laboratoire des ecoulements geophysiques et industriels wave flume for irregular waves the interest of such experiments resides in presenting complex combinations of wave skewness and asymmetry in bed load ripple and sheet flow regimes net sediment transport rates on typical beach morphodynamics are analyzed in regard to wave skewness and asymmetry undertow and ripple occurrence onshore bar migration is mainly associated with onshore directed sediment transport whereas terrace profile and offshore bar formation correspond to offshore sediment transport as for natural beaches energetic moderate wave climates mostly induce offshore onshore sediment fluxes for a given significant wave height an increase decrease in the wave climate peak period is associated with an increase decrease in wave skewness and leads mostly to offshore onshore sediment fluxes the experiments are fully characterized by unsteady behavior consequently several conditions exhibit phase lag effects where the sediment is mobilized by the wave crest and transported by the following trough which produces a net offshore transport even for a weak undertow the presence of ripples clearly contributes to enhance this behavior an original concept due to its application to skewed asymmetric irregular waves presents the important interaction between wave nonlinearities driving the sediment fluxes the net sediment transport rate under strongly skewed waves is either offshore directed due to phase lag effects or onshore directed when the wave asymmetry is large enough both these mechanisms probably largely contribute to bar formation and migration

swash on steep and shallow beaches extensive field observations of swash on natural beaches are used to relate the magnitudes of swash oscillations to incident wave conditions and the beach slope swash fluctuations at wind wave frequencies defined here as f 05 hz appear to be saturated as in laboratory experiments with monochromatic waves wave breaking prevents the magnitudes of swash oscillations at incident wave frequencies from increasing past a certain level which depends on the beach slope all data sets considered support this conclusion in contrast the magnitude of swash oscillations at surf beat frequencies defined as f 05 hz varies between data sets possible reasons for the discrepancy are discussed despite their differences all data sets show that motions at surf beat frequencies dominate the swash spectrum on dissipative beaches as in previous studies the frequencies of spectral hills and valleys in the spectra of surf zone sensors suggests that a significant fraction of the surf beat energy is contained in motions which are standing in the cross shore direction preliminary analysis indicates that shoreward propagating surf beat is coupled to incident wave groups

test of sediment initial motion theories using irregular wave field data sediment initial motion theories predict the flow conditions that coincide with onset of sediment motion but usually the most that can be determined from burst sampled field data is whether or not sediment was in motion furthermore initial motion theories are usually based on regular wave laboratory data with little or no guidance given on how such theories are to be transferred to the real world of irregular waves a field dataset obtained from the zone of wave shoaling beyond the surfzone is used to compare the performance of three initial motion theories in a way that takes explicit account of wave irregularity and the limitations of burst sampling the dataset comprises video images of the seabed and measurements of waves currents and suspended sediment the initial motion theories tested were komar miller s 1975 j sedim petrol 45 362 367 wave orbital speed theory a wave stress theory and a wave plus current stress theory fourteen transitions from no sediment motion to sediment motion were observed but not all of those represented a challenging test of theory using the criterion that the best theory is the one that minimizes errors in classifying bursts as no sediment motion or sediment in motion komar miller s 1975 theory was found to perform the best when waves were characterized by significant wave height and mean spectral period both of which can be estimated directly from pressure data alone komar and miller s theory was better at predicting the onset of extended transport events which occurred during confused seas rather than the transition back to moribund seabed under clean swell at the end of such events the conclusion regarding best theory is dependent on the choice of scales used to characterize wave motion the way forward therefore is to standardize and define terms precisely

sand transport processes and bed level changes induced by two alternating laboratory swash events abstract sand transport processes and net transport rates are studied in a large scale laboratory swash zone bichromatic waves with a phase modulation were generated producing two continuously alternating swash events that have similar offshore wave statistics but which differ in terms of wave swash interactions measured sand suspension and sheet flow dynamics show strong temporal and spatial variability related to variations in flow velocity and locations of wave capture and wave backwash interactions suspended and sheet flow layer transport rates in the lower swash zone are generally of same magnitude but sheet flow exceeds the suspended load transport by up to a factor four during the early uprush the bed level near the inner surf zone is relatively steady during a swash cycle but changes of o cm s are measured near the mid swash zone where wave swash interactions lead to strongly non uniform flows the two alternating swash events produce a dynamic equilibrium with bed level changes up to a few mm induced by single swash events but with net morphodynamic change over multiple events that is two orders of magnitude lower most of the intra swash and the single event averaged bed level changes in the swash zone are caused by a redistribution of sediment within the swash the transport of sediment across the surf swash boundary is minor at intra swash time scale but becomes increasingly significant at swash averaged time scales or longer i e averaged over multiple swash events

extreme value statistics for wave run up on a natural beach abstract statistics of wave run up maxima have been calculated for 149 35 minutes data runs from a natural beach during the experiment incident wave height varied from 0 4 to 4 0 m incident wave period from 6 to 16 s and beach face slope from 0 07 to 0 20 four extreme statistics were calculated the maximum run up height during each run the 2 exceedence level of shoreline elevation the 2 exceedence height for individual run up peaks and the 2 exceedence level for swash height as determined by the zero upcrossing method these statistics were best parameterized when normalized by the incident significant wave height and plotted against the iribarren number h l 0 1 2 the swash data with set up removed showed less scatter than total run up with set up included for iribarren number greater than 1 5 the run up was dominated by the incident frequencies for lower iribarren number longer period motions dominated the swash a reasonable value of wave steepness for a fully developed storm sea is 0 025 so that a storm iribarren number can be estimated as 6 3 times the beach slope using this and an offshore design wave height the included graphs may provide guidance in determining a design run up height

observations of morphological change and sediment transport on a steep gravel beach abstract observations of morphological change and swash sediment loads concurrent with measurements of water level waves and currents were obtained during a spring to spring tidal cycle on a steep macrotidal gravel beach in southwest england the wave conditions experienced during the field experiment were relatively calm and the significant inshore wave height and period averaged 0 4 m and 6 s respectively incident frequency water motions dominated the hydrodynamics and the phasing between water surface elevation and cross shore and alongshore currents was inconsistent with standing edge wave motion morphological change was directly related to maxima in shoreline elevation and four modes of berm adjustment identified regression and rollover in response to falling and rising water levels respectively and removal and reformation during and after storms respectively swash processes transported substantial amounts of sediment at rates comparable to sand beaches and the net transport under modal wave conditions was estimated to be 1 kg per swash onshore per unit metre beach width steep hydrodynamic gradients induced by the abrupt slope breaks of the step and berm are one of the main causes of the large morphological variability characteristic of gravel beaches

hydrodynamics and morphological adjustment of a mixed sand and gravel beach torere bay of plenty new zealand detailed measurements of cross shore wave energy transformation swash sediment transport and beach profile change under low energy conditions are reported from a mixed sand and gravel beach at torere bay bay of plenty new zealand measurements were undertaken during a 10 day period following a storm event and document post storm recovery of the beach nearshore wave spectra identify periods in which incident wave energy is dominated by swell and wind wave energy results show that wind wave energy observed in the nearshore is effectively removed from beachface spectra at the break point step under lower tidal stages swash is driven by longer period swell energy although dissipation of short period wave energy is critical in entraining sediments on the lower beach at higher tidal stages wind wave energy is able to propagate across the break point step shoal and break on the lower beachface tidal modulation of wave processes across the lower beachface under low incident wave conditions is found to stimulate active sediment reworking migration of the break point step and shoreward sediment flux to promote beach accretion

high resolution monitoring of wave transformation in the surf zone using a lidar scanner array understanding of breaking and broken waves is key for the prediction of nearshore sediment transport and coastal hazards however the difficulty of obtaining measurements of highly unsteady nearshore waves has limited the availability of field data this paper reports on a novel field experiment designed to capture the time varying free surface throughout the surf and swash zones was conducted on a dissipative sandy beach using an array of 2d lidar scanners three scanners were deployed from the pier at saltburn by the sea uk for a 6 day period to monitor the surface elevation of nearshore waves from the break point to the runup limit at temporal and spatial resolutions order of centimetres rarely achieved in field conditions the experimental setup and the procedure to obtain a continuous time series of surface elevation and wave geometry is described a new method to accurately determine the break point location is presented and compared to existing methodologies

the rare earth element chemistry of estuarine surface sediments in the chesapeake bay abstract concentrations of rare earth elements ree were measured in the fine fraction of shallow surface sediments from the lower chesapeake bay as studies suggest that coagulation of colloids dominates the removal of ree from the dissolved load in low salinity regions of estuaries ree in sediments showed spatial heterogeneity both laterally and longitudinally we observed the influence of salinity on the spatial and temporal variability in total ree content and on eu anomalies lower total ree was found in sediments deposited along the eastern shore the chemistry of the mid bay islands was distinct with higher overall ree content and slightly more positive ce anomaly values positive ce ce in the mid bay are attributed to coriolis acceleration restricting freshwater flow towards the west away from the islands leading to oxidative removal of ce from the pore waters to the sediments the presence of positive eu eu in sediments deposited along the eastern shore is linked to salinity we suggest that unique local conditions along the eastern shore possibly including submarine groundwater discharge of nutrient rich reducing waters combined with organic matter decay and the predominance of oceanic water flow toward this region leads to the development of a strong localized salinity gradient this study demonstrates the utility of ree sediment chemistry in identifying and resolving local and estuarine wide geochemical processes

the influence of wave groups and wave swash interactions on sediment transport and bed evolution in the swash zone abstract large scale laboratory measurements of sediment dynamics in the swash zone are presented two bichromatic wave group conditions were generated having the same energy content but different wave group period t g 15 0 s and 27 7 s for the shortest wave group due to bore focusing the shoreline fluctuates predominantly at the t g time scale showing a large runup and the presence of wave swash interactions with strong momentum exchange in contrast for the longer wave groups the swash excursion is dominated by the individual waves the uprush generally promotes onshore sediment advection with consequent erosion at the rundown location but accretion close to the runup on the contrary the backwash promotes seaward sediment advection and accretion at the rundown location the presence of repeated wave swash interactions modifies these patterns slightly a wave overrunning a previous uprush promotes a reduction in onshore sediment advection while weak wave backwash interactions reduce seaward advection consequently the measured sediment dynamics shows stronger intra swash cross shore sediment advection for the swash events produced by the short wave groups measurements of the sheet flow layer near the shoreline show that for the shortest wave groups the vertical structure of the concentration is influenced by horizontal advection leading to large sheet flow layer thickness however for the longer wave groups the local vertical exchange of sediment in the sheet flow layer is dominant with the presence of a pick up and mirroring upper layer similar to oscillatory sheet flow measurements these results reaffirm the important effects of the wave group structure and the wave swash interactions on the swash zone sediment dynamics and beach face evolution

recent advances in modeling swash zone dynamics influence of surf swash interaction on nearshore hydrodynamics and morphodynamics the role of the swash zone in influencing the whole nearshore dynamics is reviewed with a focus on the interaction between surf and swash zone processes local and global hydromorphodynamic phenomena are discussed in detail and a description of the overall swash zone operation is given the effects of swash zone boundary conditions are highlighted together with the importance of surf zone boundary conditions major emphasis is placed on illustrating the interactions of various hydrodynamic modes which in turn control the swash and surf zone morphology finally methods to account for swash zone processes in coastal models with different temporal and spatial resolutions are proposed

near shore hypoxia in the chesapeake bay patterns and relationships among physical factors near shore shallow waters in the chesapeake bay periodically experience episodes of anoxia or severe hypoxia during summer in order to examine the severity and temporal pattern of hypoxia and environmental factors that may lead to such episodes dissolved oxygen salinity and temperature were measured at 15 min intervals during the summers of 1987 and 1988 in a western shore oyster bed bottom dissolved oxygen concentrations averaged lower at a 4 m site than at a 2 m site at the 4 m site dissolved oxygen concentrations dropped below 2 mg l 1 during approximately 40 of days and below 1 mg l 1 during approximately 10 of days each summer however diel fluctuations in oxygen concentrations were sufficiently large that even on days of the most severe oxygen minima dissolved oxygen concentrations always reached or exceeded a level tolerable by most estuarine organisms during some part of the day during episodes of severe hypoxia on the western shore of the chesapeake bay oxygen minima 1 coincided with increased salinities and ebb tides 2 were preceded by winds from the s sse minima of 0 5 1 mg l 1 or sw minima of 0 6 1 1 mg l 1 and 3 were reached during 22 00 06 00 hours severe hypoxia at the study site therefore appeared to result from intrusions of bottom water which were most effectively driven by southerly winds tidal currents were required to provide the final force that brought deep water close to shore the diel pattern of intrusions is most likely caused by winds which were often either too strong or had too weak a southerly component to permit intrusions without near shore mixing and reaeration to occur during afternoon early evening hours and the diel periodicity of tides short term fluctuations in temperature and salinity were not as great as fluctuations in dissolved oxygen when compared to seasonal fluctuations of each parameter for many organisms short term fluctuations in temperature and salinity may therefore be less likely to influence the habitability of areas such as the near shore chesapeake bay than are similar duration fluctuations in dissolved oxygen concentrations

storm overwash of a gravel barrier field measurements and xbeach g modelling abstract gravel barriers provide a natural form of coastal protection and flood defence for many sites around the uk and worldwide predicting their vulnerability to different storm impact regimes that cause overtopping and overwash is crucial as these processes can lead to hazardous consequences such as inundation of the back of the barrier or breaching this paper presents the first field measurements of storm overwash events on a gravel beach loe bar cornwall england high frequency in situ observations 2 hz were performed using a 2d laser scanner and allowed a complete characterization of the overwash flows velocity and depth and morphological response along a cross shore section of the barrier these novel measurements are used to validate the numerical model xbeach g to forecast overwash discharge several simulations were performed with xbeach g to investigate the thresholds for the different storm impact regimes given a variety of water levels and wave heights wave period and wave spectral shape are found to significantly affect these thresholds while short period waves dissipate most of their energy by breaking before reaching the swash zone and produce short runup excursions long period waves due to their low steepness arrive at the swash zone unbroken with enhanced heights due to shoaling thus promoting large runup excursions when the offshore wave spectrum has a bimodal shape wave transformation in shallow water causes the long period peak to dominate the swash giving large runup excursions long period waves or strongly bimodal waves result in enhanced runup thereby reducing the thresholds for barrier overtopping or overwashing

the influence of swash based reflection on surf zone hydrodynamics a wave by wave approach abstract a detailed understanding of the behaviour of waves in the nearshore is essential for coastal engineers as these waves cause beach erosion coastal flooding and damage to coastal structures significantly the influence of reflected waves is often neglected in surf zone studies although they are known to influence wave properties and circulation in the nearshore in this paper a phase resolving model is rigorously applied to model conditions from the prototype scale bardexii experiment in order to examine and assess the influence of swash based reflection on surf zone hydrodynamics at both the individual wave and time averaged timescales surface elevation is separated into incoming and outgoing signals using the radon transform and a crest tracking algorithm is used to extract incident and reflected wave properties it is found that on steep beaches tan 1 9 the swash based reflection the reflection generated in the swash during the backwash contributes significantly to the intrawave variability of individual wave properties such as the wave height to water depth ratio through the generation of quasi nodes antinodes system for expressed with individual wave heights variations up to 25 and 40 are obtained for the modelled regular and irregular wave tests whereas it reaches 15 when it is based on the significant wave height the outgoing wave field induced hydrodynamics is also found to affect time averaged parameters undertow and horizontal velocity skewness the undertow is mainly strengthened particularly in the shoaling region where the outgoing component dominates over the contribution from the incoming wave field offshore of the bar an onshore directed flow streaming close to the bed is also generated under the outgoing wave field and is suspected to help in stabilising the bar position this along with the influence of the outgoing wave field on the horizontal velocity skewness and the presence of quasi standing waves suggests a complex contribution of the hydrodynamics induced by swash based reflection into sediment transport rates and nearshore bar generation migration

observations and predictions of fluid velocities in the surf and swash zones 1 surfzone and swashzone water level fluctuations and cross shore fluid velocities observed at seven cross shore locations for 139 51 min periods on a low sloped fine grained sandy beach are shown to be modeled well by the depth averaged nonlinear shallow water equations the model initialized with observations about 150 m from the shoreline in 300 cm water depth accurately predicts the observed decrease in sea swell wave heights and orbital velocities with decreasing water depth across the surf zone and the observed maxima in infragravity orbital velocities and offshore directed mean flows near the outer edge of the swash zone in the surf zone both the observed and predicted velocity fluctuations are dominated by sawtoothed shaped pitched forward asymmetrical sea swell waves in the swash zone infragravity waves contribute substantially to the total velocity variance and asymmetry shoreward of the outer swash zone observed and predicted total and infragravity velocity asymmetry decrease onshore changing sign from positive to negative in the upper swash

wave setup and runup an integrated approach abstract by extending and sharpening the usual definitions of water depth and mean water level throughout the swash zone it is shown that the elevation of the shore line on an impermeable beach is logically at the runup limit not at the average water line level thus the runup limit becomes a point on the setup profile and this leads to a significant expansion of the experimental information on setup which can be extracted from the existing literature from the experimental data base thus extended a first approximation to a universal description of setup profiles is derived i e the most appropriate vertical and horizontal scaling parameters are suggested for the shape of the mean water surface in the inner surf zone existing setup data show that traditional simplistic setup models are inadequate for modelling the shape of the most landward part of the mean water surface and hence for predicting the shoreline setup instead it is suggested to base estimates of the shoreline setup on the relation between this quantity and the maximum runup height together with well proven runup formulae the validity of this approach needs to be established quantitatively however through simultaneous measurements of runup and mean water surface on in natural beaches

extreme coastal responses using focused wave groups overtopping and horizontal forces exerted on an inclined seawall abstract total wave group overtopping and maximum horizontal force responses are investigated for an idealised seawall dike on a plane beach subject to compact focused wave attack using both laboratory and numerical wave flumes the wave group interactions have very short durations such that extraneous reflections from the wavemaker arrive long after the main interaction these short test durations facilitate the use of large ensembles of tests to explore the sensitivity of overtopping and force responses to variations in focus location phase angle at focus and linear focus wave amplitude the scope of the laboratory wave flume tests is broadened by accurate numerical simulation based on a 1dh hybrid boussinesq nlsw model for a given focus location and linear focused wave amplitude variations in phase lead to an order of magnitude change in the group overtopping volume substantial increases in overtopping volume owing to the use of linear wavemaker theory compared to second order theory are also observed these observations have implications for phase independent empirical relationships derived using linear paddle signals in physical experiments examination of the incidence of wave groups parametrically optimised for maximum and minimum overtopping volumes indicates that the overtopping volume may be optimised by minimising reflections of pre overtopping waves within the group while maximising the amplitude of the first overtopping bore numerical predictions of horizontal seawall forces are obtained using fluid impulse derivatives and hydrostatic pressures obtained from the shallow water model within the shallow water model framework hydrodynamic force contributions included in the fluid impulse method are observed to be small relative to the hydrostatic pressure force the parametric dependence of the horizontal non impulsive forces on the seawall is very similar to that of the overtopping volumes with clear bands of large values observed as a function of phase and focus location for a given amplitude this suggests that the parametric optimisation of focused wave groups is a robust method for the investigation of multiple coastal responses such as overtopping forces and runup

swash zone sediment fluxes field observations abstract this paper describes newly obtained high frequency observations of beach face morphological change over numerous tidal cycles on a macrotidal sandy beach made using a large array of ultrasonic altimeters these measurements enable the net cross shore sediment fluxes associated with many thousands of individual swash events to be quantified it is revealed that regardless of the direction of net morphological change on a tidal time scale measured net fluxes per event are essentially normally distributed with nearly equal numbers of onshore and offshore directed events the majority of swash events cause net cross shore sediment fluxes smaller than 50 kg m 1 and the mean sediment flux per swash event is only o 1 kg m 1 leading to limited overall morphological change however much larger events which deposit or remove hundreds of kilograms of sand per meter width of beach occur at irregular intervals throughout the course of a tide it was found that swash swash interactions tend to increase the transport potential of a swash event and the majority of the swash events that cause these larger values of sediment flux include one or more interactions the majority of the larger sediment fluxes were therefore measured in the lower swash zone close to the surf swash boundary where swash swash interactions are most common despite the existence of individual swash events that can cause fluxes of sediment that are comparable to those observed on a tidal time scale frequent reversals in transport direction act to limit net transport such that the beach face volume remains in a state of dynamic equilibrium and does not rapidly erode or accrete

nearshore sandbar migration field observations suggest that onshore sandbar migration observed when breaking wave driven mean flows are weak may be related to the skewed fluid accelerations associated with the orbital velocities of nonlinear surface waves large accelerations both increases and decreases in velocity magnitudes previously suggested to increase sediment suspension occur under the steep wave faces that immediately precede the maximum onshore directed orbital velocities weaker accelerations occur under the gently sloping rear wave faces that precede the maximum offshore directed velocities the timing of strong accelerations relative to onshore flow is hypothesized to produce net onshore sediment transport the observed acceleration skewness a measure of the difference in the magnitudes of accelerations under the front and rear wave faces is maximum near the sandbar crest the corresponding cross shore gradients of an acceleration related onshore sediment transport would cause erosion offshore and accretion onshore of the bar crest consistent with the observed onshore migration of the bar crest furthermore the observations and numerical simulations of nonlinear shallow water waves show that the region of strongly skewed accelerations moves shoreward with the bar suggesting that feedback between waves and evolving morphology can result in continuing onshore bar migration

beach face and berm morphodynamics fronting a coastal lagoon this study documents two different modes of berm development i vertical growth at spring tides or following significant beach cut due to substantial swash overtopping and 2 horizontal progradation at neap tides through the formation of a proto berm located lower and further seaward of the principal berm concurrent high frequency measurements of bed elevation and the associated wave runup distribution reveal the details of each of these berm growth modes in mode i sediment is eroded from the inner surf and lower swash zone where swash interactions are prevalent the net transport of this sediment is landward only resulting in accretion onto the upper beach face and over the berm crest the final outcome is a steepening of the beach face gradient a change in the profile shape towards concave and rapid vertical and horizontal growth of the berm in mode 2 sediment is eroded from the lower two thirds of the active swash zone during the rising tide and is transported both landward and seaward on the falling tide sediment is eroded from the inner surf and transported landward to backfill the zone eroded on the rising tide the net result is relatively slow steepening of the beach face a change of the profile shape towards convex and horizontal progradation through the formation of a neap berm the primary factor determining which mode of berm growth occurs is the presence or absence of swash overtopping at the time of sediment accumulation on the beach face this depends on the current phase of the spring neap tide cycle the wave runup height and indirectly offshore wave conditions and the height of the pre existing berm a conceptual model for berm morphodynamics is presented based on sediment transport shape functions measured during the two modes of berm growth c 2006 elsevier b v all rights reserved

parameterization of velocity skewness under waves and its effect on cross shore sediment transport skewness of the near bed cross shore orbital velocity plays a central part in many beach equilibrium and sediment transport models although boussinesq models can be used to predict the velocity skewness of shoaling and breaking waves these models are computationally quite intensive herein a large collection of data from a number of field environments are used to derive via genetic programming an analytical expression for velocity skewness under shoaling and breaking waves the resulting expression provides a good fit to the data the inclusion of skewness in a sediment transport model demonstrates its importance in predicting the shoreward transport of sediment during periods of beach recovery

measurement of wave by wave bed levels in the swash zone abstract a technique is described to observe and quantify wave by wave bed level changes in the swash zone the ultrasonic instrument system is non contact with the beach face surface being measured and the sensors remain outside of the fluid flows causing sediment movement sensor resolution combined with the electronic noise inherent within a digital network data logging system results in a conservative measurement accuracy of 1 mm equating to a couple of sand grain diameters in height illustrative field results demonstrate the practical use of the instrumentation and a simple data pre processing method to separate swashes and intervening bed level events is discussed these example data reveal rather complex fluctuations of the bed observed over time periods of minutes to hours rather strikingly gross bed level changes per wave are revealed to be up to many orders of magnitude larger than the observed net rate of beach face evolution it is outlined how observations of successive bed level changes at multiple locations within a dense grid combined with a consideration of sediment continuity will now enable the total net sediment transported per uprush backwash to be quantified

the hydrology of the upper swan river estuary with focus on an artificial destratification trial a trial to artificially destratify part of the water column of the swan canning estuary took place over four weeks in 1997 destratification was attempted with bubble plumes created by pumping compressed air through a porous pipe near the bed at a location in the upper estuary the purpose of the trial was to determine whether the resultant bubble curtain could mix the water column thereby altering the extent of upstream and downstream mixing and the vertical structures of salinity temperature dissolved oxygen and turbidity the destratification trial was monitored using three techniques vertical profiles taken on several days at selected stations along the estuary fine scale profiles in the vicinity of the bubble curtain on one day and continuous water column profiles taken 1 km upstream of the curtain the seasonal upstream propagation of brackish water underneath a residual freshwater discharge was affected by the magnitude of freshwater discharge and tidal elevations superimposed upon diurnal and semi diurnal tides were non tidal water level changes induced mostly by variations in barometric pressure these caused large changes in the salt wedge position destratification by the bubble curtain was compromised by these large oscillations which limited the exposure of the salt wedge region to the mixing action of the bubble curtain complete vertical mixing of the water column was observed up to 30 m either side of the curtain on 30 october disruptions to the density stratification were not evident beyond 350 m of the curtain in the immediate vicinity 30 m of the curtain deficits of dissolved oxygen in bottom waters were generally reduced or obliterated and a naturally turbid plume of water near the bottom of the estuary was mixed through the water column the effects of the bubble curtain on dissolved oxygen turbidity and temperature were however similar to those for salinity with mixing confined to around 30 m from the curtain and no effect observed further than 350 m away the upper swan river estuary although relatively narrow and strongly vertically stratified is unsuited to destratification using bubble plumes cycling of spring and neap tides and non tidal water level changes together with freshwater inflows to the estuary strongly limit the longitudinal extent of mixing by bubble curtains copyright 2001 john wiley sons ltd

bar trough generation on a natural beach mechanisms for bar trough generation are examined using velocities measured in the field applied to the bowen 1980 bailard 1981 energetics based sediment transport model measurements consist of a cross shore array of nine electromagnetic current meters spanning the surf zone and daily bathymetric surveys during a 10 day period during which two storms occurred when the bathymetry evolved from a three dimensional terrace to a well developed linear bar the model predicts bed and suspended load transport separately based on various velocity moments the velocities are partitioned into mean currents low frequency infragravity and shear instabilities 0 05 hz to determine the relative importance of various mechanisms to the total transport velocity moments are computed over 90 min intervals to resolve tidal fluctuations tidal signatures were apparent in all modes of transport predicted transport rates are integrated and compared with daily cross shore bathymetric profiles averaged over a 400 m length of beach the suspended load terms were an order of magnitude greater than bed load terms owing to the low fall velocity of the fine grain sand within the surf zone model results for this experiment indicate the dominant mechanism for bar development was sediments mobilized by the strong longshore current and incident short waves within the surf zone and transported offshore by the mean undertow and shoreward transport onshore due to short wave velocity skewness using standard coefficients the model correctly predicted the first order movement of the bar during storms but underpredicted trough development and did not always perform well during mild wave conditions

broadband waveform modelling of anomalous strong ground motion in the 1989 loma prieta earthquake using three dimensional geologic structures strong motion recordings of the 1989 loma prieta earthquake show a large coherent sh wave displacement pulse across much of the san francisco bay area this distinctive ground motion has been modelled using approximate broadband synthetics for a double couple centroid source in a 3 d crustal model for the region the synthetics indicate that 1 horizontal bending and focusing of sh waves by the lateral crustal velocity contrast across the san andreas fault and 2 the source radiation pattern contribute significantly to the observed azimuthal variation of the sh pulse and hence to the regional variations of strong ground shaking in the period range of 1 to 8 sec in addition the scattering of surface reflected shear waves by deep basins under the santa clara valley may contribute to increased coda amplitude and duration observed for sites around oakland the wave modelling also supports the earlier conclusion that an increase in intensity in portions of san francisco and oakland is in part the result of energy reflected from the base of the crust somerville and yoshimura 1990

swash zone sediment transport step dynamics and morphological response on a gravel beach abstract state of the art morphodynamic field data were collected from slapton sands uk a fine gravel beach d50 2 10 mm over a 10 day period under a range of wave tide conditions comprising a mixture of southerly swell and easterly wind waves hs 0 5 1 m ts 4 8 s tide range 3 4 m over the field period the upper beach experienced accretion and berm formation during tides with low steepness swell dominated wave conditions h l 0 01 surprisingly the intertidal beach showed an opposite trend with sediment losses under swell conditions and an increase in sediment volume due to wind waves and suggests that upper beach morphological change can be decoupled from the overall sediment budget a submerged accretionary feature the beach step grew and migrated onshore on the rising tide typically reaching a maximum relief of around 0 5 m then gradually decreased in prominence while migrating offshore as the tide fell resulting in little net morphological change the step was better developed during the falling tide than the rising tide and through its control on the swash hydro and sediment dynamics the step had a significant effect on the development of the berm swash flow velocities under the conditions measured were often in excess of 2 m s 1 for both the uprush and the backwash onshore mean flows occurred in the upper swash region 40 inundation was characterised by offshore mean flows swash infiltration losses in the swash zone increased from 40 in the lower swash region to 100 in the upper swash region the most energetic swash flows and the strongest offshore mean flows occurred at the transition between swash zone and surf zone 90 100 inundation

storm response and beach rotation on a gravel beach slapton sands u k abstract continuous argus video data and fortnightly measurements of subaerial morphology were obtained over a 3 year period from a steep macrotidal gravel beach on the southwest coast of the u k concurrent wave and water level data were also collected enabling the correlation of the observed morphological changes to the hydrodynamic forcing wave conditions are generally low h s 0 5 1 m but the beach is affected by frequent storm wave activity c 15 storms per year with h s 2 4 m with waves either approaching from the south swell waves or from the east wind waves an assessment of the three dimensional morphological response of the beach to the two typical storm types was carried out by analysing the impact of 27 storms that occurred from april 2007 to april 2009 southerly storms cause accretion of the supratidal zone and erosion of the intertidal zone and a significant loss in overall beach volume easterly storms on the other hand induce supratidal erosion and intertidal accretion and a significant gain in overall beach volume during the intervening calm periods a small supratidal berm is constructed and a modest gain in overall beach volume occurs wave modelling indicated that opposing longshore energy fluxes occur for the different storm types with a northerly energy flux during southerly storms and a southerly flux during easterly storms weekly shorelines derived from the argus images revealed that the northern end of the beach widened by c 30 m and the middle beach receded by c 40 m over a relatively brief period a few months the occurrence of this beach rotation event is attributed to a higher frequency of southerly storms and or a lower frequency of easterly storms over this period thus the development and stability of the beach on annual time scales depend on the relative contributions of the two storm types and their sequencing longshore sediment transport lst rates derived from the data on beach morphological change were compared with several littoral drift formulae previously applied to gravel beaches the cerc equation with a proportionality factor k between littoral drift rate i l and longshore wave energy flux p l of k 0 054 yielded the best results

field observations of wave driven setdown and setup wave driven setdown and setup observed for 3 months on a cross shore transect between the shoreline and 5 m water depth on a barred beach are compared with a theoretical balance between cross shore gradients of the mean water level and the wave radiation stress the observed setdown the depression of the mean water level seaward of the surf zone is predicted well when radiation stress gradients are estimated from the observations using linear theory at each location along the transect the observed setdown also agrees with analytical predictions based on offshore wave observations and the assumption of linear dissipationless normally incident waves shoaling on alongshore homogeneous bathymetry the observed setup the superelevation of the mean water level owing to wave breaking is predicted accurately in the outer and middle surf zone but is increasingly underpredicted as the shoreline is approached similar to previous field studies setup at a fixed cross shore location increases with increasing offshore wave height and is sensitive to tidal fluctuations in the local water depth and to bathymetric changes numerical simulations and the observations suggest that setup near the shoreline depends on the bathymetry of the entire surf zone and increases with decreasing surf zone beach slope defined as the ratio of the surf zone averaged water depth to the surf zone width a new empirical formula for shoreline setup on nonplanar beaches incorporates this dependence

iron rich carbonate tidal deposits angepena formation south australia a redox stratified cryogenian basin abstract the cryogenian angepena formation ca 650 ma of south australia records deposition in a peritidal environment equivalent to and landward of the balcanoona reef complex and offers valuable insights into shallow marine chemistry during the nonglacial interlude between two global ice ages the sedimentary facies comprise an iron rich marine red bed succession and include red mudcracked dolomitic shales tepee dolostone crossbedded intraclastic ooid grainstone and tepee related sheet cavities with marine cements these facies are interpreted to have been deposited in a cryogenian tidal flat to subtidal setting that is laterally equivalent to the reefal and back reef environments of the balcanoona formation marine cements from this environment are characterized by well preserved non and bright cathodoluminescent zoning and strong negative to slightly positive cerium ce anomalies ce ce we suggest that the angepena formation is indicative of intermittent synsedimentary iron oxide precipitation in an oxidized peritidal environment in an otherwise strongly ferruginous and anoxic oceanic setting large negative ce anomalies develop over a narrower depth range when compared to modern oxic marine settings highlighting the importance of dissolved mn and fe concentrations in controlling the magnitude of the negative ce anomalies overall coupled sedimentological and geochemical evidence suggest a neoproterozoic shallow marine system at the interface of an oxidizing atmosphere and an anoxic ferruginous marine system

quantification of sand bar morphology a video technique based on wave dissipation a technique is presented to remotely measure the scales and morphology of natural sand bars based on the preferential dissipation of wind waves and swell over the crests of the bar photographic or video images are recorded and statistical uncertainties associated with incident wave height modulations removed by averaging time exposures ground truth testing of the technique was carried out as part of the superduck experiment in october 1986 the time exposures generally provided a good mapping of underlying morphology allowing detection of the bar and determination of cross shore and longshore length scales however during high waves persistent surface foam obscures the relationship of image intensity to local dissipation modeled theoretically by dissipation of a random wave field and an enhancement technique of image differencing must be done to remove the bias errors in the estimate of bar crest distance from the shoreline are generally less than 35 but this value depends on the geometry of the particular bar logistic simplicity and quantitative capabilities make this technique very attractive

remote sensing of surf zone waves using stereo imaging abstract the measurement of water wave characteristics such as wavelength and wave height in the surf zone is important for monitoring prediction of erosion and numerical model calibration traditional methods of measuring wave heights have either been limited to a small number of points or have required contact with the water an experimental study of the remote sensing of water wave elevations through the application of stereo photogrammetry is presented this method uses two spatially offset cameras with overlapping fields of view to determine water surface elevation this remote sensing approach provides data with excellent spatial coverage and spatial and temporal resolution additionally the hardware needs are minimal and the system is quickly deployed calibrated and operational in the present study a phased approach was taken with medium scale domain 50 m 2 laboratory experiments being followed by a large scale domain 10 3 10 4 m 2 field test of the method in the laboratory reconstructed surface elevations were validated using a pressure sensor and demonstrated excellent agreement in the field measured wave heights and periods were found to agree well with available buoy data

coupling terrestrial lidar and video imagery to perform 3d intertidal beach topography abstract this study investigates the possibility of combining two shore based remote sensing techniques 2d lidar and video imagery to measure 3d intertidal beach topography the shoreline elevation measured on a single cross shore section of the beach by a 2d lidar was combined with the video derived shoreline contour to finally obtain intertidal beach topography vertical root mean square error between differential gps and remotely derived intertidal beach profiles had an average value of 0 12 m with maximum disparities of 0 14 m two 3d digital elevation models dems of the beach produced over two tidal cycles demonstrated the feasibility of shore based lidar video system of describing in detail the short term morphological evolution of the intertidal area results suggest that the lidar video system can improve the capability of remotely surveying intertidal beach topography providing high quality measurements

application of lidar technology for measurement of time varying free surface profiles in a laboratory wave flume abstract an experimental study was completed to investigate the ability of a fixed two dimensional lidar instrument to obtain detailed measurements of propagating waves within a laboratory wave flume the results show that this technology can be used to obtain synchronous free surface measurements at a horizontal spatial resolution o 10 mm with comparable vertical accuracy to that of more conventional high precision capacitance wave probes the principal advantage of using the lidar is that a single non intrusive instrument can be utilised to measure the entire wave field at high resolution allowing detailed evaluation of wave transformation throughout the experimental domain

measurements of the time varying free surface profile across the swash zone obtained using an industrial lidar the use of an industrial lidar instrument to measure time varying water surface elevations within the swash zone is investigated the propagation of the swash lens across the beach face was measured simultaneously by a lidar instrument and a network of precision ultrasonic altimeters at a sandy beach comparison of the two datasets indicates that the time varying swash free surface profile obtained using a lidar compare favourably with point measurements obtained using ultrasonic altimeters significantly the use of a continuously scanning laser beam enables a single lidar instrument to obtain measurements of free surface elevation near synchronously at several hundred points throughout the swash zone this high spatial resolution permits small scale flow features such as the swash front gradient and the presence of secondary bores to be detailed and negates the need for the deployment of a large multi sensor array

numerical modelling of short and long wave transformation on a barred beach abstract this work aims to demonstrate an advancement towards the integrated modelling of surf zone hydrodynamics by means of a vof type numerical model cobras uc based on the reynolds averaged navier stokes equations in this paper the numerical model is adapted and validated for the study of nearshore processes on a mildly sloping beach the model prediction of wave energy transformation and higher order statistics skewness and asymmetry are in good agreement with detailed laboratory observations from a barred beach boers m 1996 simulation of a surf zone with a barred beach report 1 wave heights and wave breaking tech rep 96 5 comm on hydrol and geol eng dept of civil engineering delft university of technology moreover the numerical model allows us to study the low frequency motions inside the surf zone it is found that in order to achieve a satisfactory simulation of both short and long wave transformation the numerical model must achieve i the simultaneous second order wave generation and absorption ii the energy transfer between triad of components iii the short and long wave energy dissipation inside the surf zone and iv the wave reflection at the shoreline comparisons between numerical and experimental results demonstrate the model capability to satisfactorily simulate all the aforementioned processes

large scale laboratory investigation into the effect of varying back barrier lagoon water levels on gravel beach morphology and swash zone sediment transport abstract it is generally accepted that the effect on beach morphology of the interactions between swash motion and the beach groundwater table depends on the elevation of the latter relative to that of the sea specifically a low beach groundwater table is considered to enhance onshore sediment transport and beach accretion while the reverse is thought to hold for a high beach groundwater table here we use the results of a carefully designed series of tests conducted in the delta flume the netherlands as part of the barrier dynamics experiment bardex to unequivocally demonstrate the validity of this assertion during the experiment a 4 m high and 50 m long gravel barrier d 50 11 mm was constructed within the central region of the 250 m long and 7 m deep wave flume enabling a back barrier lagoon to be located at its landward side the groundwater table in the beach was manipulated by lowering and raising the lagoon level and the gravel beach was subjected to variable wave conditions and sea lagoon levels using as the initial beach profile the morphology resulting from 90 min of wave forcing with the sea and lagoon at the same level the identical wave forcing with a low lagoon level consistently resulted in onshore sediment transport in the swash zone and beach accretion whereas the identical wave forcing with a high lagoon level consistently caused offshore sediment transport in the swash zone and beach erosion the divergent beach morphological responses for the low and high lagoon levels could not be attributed to changes in the bulk swash hydrodynamics i e based on single point velocity measurements arising from a difference in the amount of swash infiltration into the unsaturated beach instead application of a sediment transport model that accounts for the effects of in exfiltration suggested that the onshore sediment transport and beach accretion for the low lagoon tests mainly resulted from enhanced bed shear stresses during the wave uprush due to infiltration into the saturated part of the beachface due to the large hydraulic conductivity of gravel k o 0 1 m s 1 the effect of altered shear stresses due to in exfiltration may be an important factor in sediment transport in the swash zone of gravel beaches

wave runup and wave overtopping measurements using a laser scanner abstract the use of a standard laser scanner to measure several hydraulic responses of coastal structures is examined to this end measurements of full scale wave runup on a dike slope in the old delta flume are described and analyzed measurements of the wave runup height with a laser scanner are compared to measurements based on visual observation the signal intensity of the laser reflection is additionally used in the determination of the wave runup height virtual wave overtopping volumes and mean overtopping discharge are determined by considering the maximum water volume above a certain virtual crest level on the dike slope for each runup event the mean wave overtopping discharge that is determined in this manner compares well to accepted formulas for overtopping the technological applicability of the technique is described including postprocessing methods and estimates are made of the accuracy that can be achieved

wave transformation across the inner surf zone sea and swell wave heights observed on transects crossing the mid and inner surf zone on three beaches a steep concave up beach a gently sloped approximately planar beach and a beach with an approximately flat terrace adjacent to a steep foreshore were depth limited i e approximately independent of the offshore wave height consistent with previous observations the wave evolution is well predicted by a numerical model based on the one dimensional nonlinear shallow water equations with bore dissipation the model is initialized with the time series of sea surface elevation and cross shore current observed at the most offshore sensors located about 50 to 120 m from the mean shoreline in mean water depths 0 80 to 2 10 m the model accurately predicts the cross shore variation of energy at both infragravity nominally 0 004 f 0 05 hz and sea swell here 0 05 f 0 18 hz frequencies in models of surf zone hydrodynamics wave energy dissipation is frequently parameterized in terms of s the ratio of the sea swell significant wave height to the local mean water depth the observed and predicted values of s increase with increasing beach slope and decreasing normalized by a characteristic wavenumber k water depth kh and are well correlated with kh a measure of the fractional change in water depth over a wavelength errors in the predicted individual values of s are typically less than 20 it has been suggested that infragravity motions affect waves in the sea swell band and hence s but this speculation is difficult to test with field observations numerical simulations suggest that for the range of conditions considered here s is insensitive to infragravity energy levels

the impact of temperate reefs on 34years of shoreline and vegetation line stability at yanchep southwestern australia and implications for coastal setback coastal setbacks are used to protect populations and infrastructure and involve determining baselines and historic trends in shoreline movements assessing these movements can be difficult on coasts with especially complex geomorphology such as due to rock and coral reefs reefs are often assumed to provide coastal protection and stability however little is known about the spatial variability of beach dynamics on beaches with reefs over inter annual and decadal time scales spatial variability in inter annual vegetation line and shoreline stability was assessed on three adjacent beaches at yanchep southwestern australia using 34 years 1974 2008 of aerial photographs over 96 of the study area beach width narrowed over the 34 years this trend was statistically significant on 83 of the middle beach 43 of the northern beach and only 29 of the southern beach the maximum mean annual change in beach width was 1 7 m yr 1 at the south end of the southern beach the first mode of the empirical orthogonal function eof explained 45 of the variability alongshore and correlated significantly p 0 05 with the 90th percentile of annual wave height and annual mean sea level beach rotation and reef controlled currents resulted in cellular beach morphodynamics and vegetation line and shoreline movements varied greatly alongshore on one occasion the beach widened by more than 50 m inter annually while other areas eroded by 50 m the southern beach that was fronted by the most continuous and highest supratidal section of reef was the most temporally variable even the vegetation line here moved by up to 20 m inter annually so cannot be assumed to be a stable baseline for setback the impact of reefs on inter annual shoreline and vegetation line stability should be considered in future guidelines for determining coastal setback

concepts in gravel beach dynamics abstract the dominant processes in gravel beach dynamics are reviewed highlighting some common themes which unify the various components of the gravel beach system the repercussions of which impart on how gravel beach dynamics might be understood conceptually in particular gravel beach dynamics are thought to be highly dependent on the temporal and spatial variation in grain size and the continual adjustments made by an active beach step both of which act not only as the expression of changing morphodynamic conditions but also as a controlling influence morphodynamics the notion that the exchanges on beaches between the hydrodynamics sediment transport and morphological change takes the form of reciprocal relationships which are mediated through feedback mechanisms in such a way that they cannot be thought of or studied independently is not a new one yet it appears that for the gravel beach morphodynamics must be re defined to describe conditions where variations in sediment size are thought to deserve parity rather than as merely a sequent entity or boundary condition morpho sedimentary dynamics is a phrase coined to intuit such cause and effect detailing the co evolution of morphology hydro hydraulics and sediment properties whilst acknowledging causative pluralism feedbacks and multiplier effects this is the recommended conceptual framework within which to crystallise thought and organise further research for the gravel beach essentially it increases the minimum number of parameters needed to describe the state of the gravel beach as a physical system therefore it is advised that simplicity will be most expedient in our future modelling efforts if complexity is to be adequately encapsulated

energy dissipation in the inner surf zone new insights from lidar based roller geometry measurements the spatial and temporal variation of energy dissipation rates in breaking waves controls the mean circulation of the surf zone as this circulation plays an important role in the morphodynamics of beaches it is vital to develop better understanding of the energy dissipation processes in breaking and broken waves in this paper we present the first direct field measurements of roller geometry extracted from a lidar data set of broken waves to obtain new insights into wave energy dissipation in the inner surf zone we use a roller model to show that most existing roller area formulations in the literature lead to considerable overestimation of the wave energy dissipation which is found to be close to but smaller than the energy dissipation in a hydraulic jump of the same height the role of the roller density is also investigated and we propose that it should be incorporated into modified roller area formulations until better knowledge of the roller area and its link with the mean roller density is acquired finally using previously published results from deepwater wave breaking studies we propose a scaling law for energy dissipation in the inner surf zone which achieves satisfactory results at both the time averaged and wave by wave scales

sediment transport patterns in front of reflective structures under wind wave dominated conditions abstract this article presents a field study of the bed response near linear reflective structures under wind wave dominated conditions at the motril harbor spain on the mediterranean coast in 1999 the harbor breakwater was enlarged 600 m by adding vertical caissons before this enlargement took place no significant bed features had been observed in the area however at the end of 2004 high resolution bathymetry showed the existence of 3 4 bars parallel to the structure with lengths between crests of 0 70 m in the cross shore direction and heights of 0 25 cm toe erosion with an amplitude up to 25 cm was also observed along the structure the necessary conditions for the appearance of the bar system are 1 a standing wave pattern in front of the structure 2 local satisfaction of the wave height and wave period threshold limits for sediment mobility using an energy based approach we analyze the time series of sea states with sediment transport capacity after breakwater construction the cumulative distributions of the shear velocities related to wsw sw sea states show that all the bars have a greater probability of being n type features predominant bed load under generalized sediment transport conditions these conclusions were verified by matching nodal lines of standing wsw sw wave patterns with the bar locations the results suggest that the motril bar system of motril is possibly generated by the standing wave patterns induced by several sea states with peak periods of o 10 s and significant sediment transport capacity resulting from wsw sw severe storm events that occurred in motril after breakwater construction this article highlights the need to verify in field conditions the present threshold limits for sediment transport mobility

inflow of oceanic water into tokyo bay and generation of a subsurface hypoxic water mass 1 temporal and spatial variations in the inflow of oceanic water into tokyo bay and the accompanying changes in circulation within the bay have been studied by repeated measurement of the longitudinal distributions of hydrographic parameters and oxygen concentration from the bay head to off the bay mouth data collection took place in summer 1998 with the particular aim of tracking the movement of a hypoxic water mass density changes in the upper ocean induce inflow and outflow of oceanic water in the bay so that when water density increased in the upper ocean heavy saline water intruded into the lower layer of the bay this inflow forced a bottom hypoxic water mass to the bay head and finally lifted it up to form a subsurface hypoxic water mass which then moved out as a thin layer just under the pycnocline reaching beyond the bay mouth when the intruding heavier deep water retreated and an intrusion of oceanic water at intermediate depth occurred the hypoxic water mass was displaced from the center to the mouth of the bay the bottom hypoxic water mass dominates in the northern half of the bay while the subsurface oxygen minimum appears frequently in the southern half

on the use of the radon transform in studying nearshore wave dynamics in the nearshore describing the complex individual wave dynamics remains a key challenge in this paper we test the ability of the radon transform to produce estimates of individual wave celerities and to separate incoming and outgoing waves conserving the temporal characteristics the radon transform is a projection of a two dimensional field into polar space oblique features such as propagating crests in a spatio temporal space are identified with density peaks in the polar space in this paper the radon transform is applied to synthetic test cases including a wide range of beach slopes and wave conditions the radon transform shows good skills at estimating individual celerity and separating incoming and outgoing components with a relative rms error lower than 10 even a standing wave node the accuracy is fairly insensitive to wave characteristics whereas the main limitations rise from the sampling scheme and are the number and density of wave gauges the distance between gauges should be less than one third of the shortest wavelength while the set of gauges should cover more than one third of the longest wavelength

sediment resuspension on beaches response to breaking waves field data of time averaged suspended sediment concentration ssc are presented from three different uk beaches and a variety of wave conditions the data are collated into a single analysis to examine the mechanisms associated with sand resuspension in the surf zone emphasis is placed upon the relative contribution of bottom and surface generated turbulence in controlling suspended sediment concentration distribution inside the surf zone vortices induced by breaking waves and bores are the main mechanism for sediment resuspension this process dominates over bottom boundary layer processes time averaged reference concentration defined as the ssc at 3 5 cm above the bed does not correlate with bottom induced shear stress or predicted ripple steepness both reference concentration and vertical distribution of sediment are controlled by the breaking wave plunging spilling characteristics within the inner surf zone hydraulic jumps associated with strong offshore flows are responsible for sediment resuspension vertical distribution of sediment is parameterised using a convective type time averaged suspended sediment concentration profile reference concentration is highly correlated with wave breaking type as defined by the local breaker parameter the mixing parameter depends also on the wave breaking type and may be expressed as a fraction of the local water depth

seismic evidence for small scale heterogeneity throughout the earth s mantle details in the amplitude structure of short period precursors to the seismic core phase pkp can be used to constrain the depth extent of mantle scattering the simplest model consistent with the observations invokes small 8 km weak r m s velocity perturbations of 1 random heterogeneities uniformly distributed throughout the mantle the data do not support previously proposed models that place an increase in the concentration of scattering sites near the base of the mantle and instead place an upper limit on the amplitude of any short wavelength topography at the core mantle boundary

nearshore wave height variation in unsaturated surf the nearshore evolution of wave height is presented from field observations during unsaturated surf conditions from 10 different beaches characterized by microtidal conditions and predominantly swell dominated wave climates wave evolution is presented in terms of wave height to water depth ratio gamma for comparison with previous data from saturated surf both conventional time averaged gamma rms and a new wave by wave analysis gamma w are performed values of gamma increase with increasing offshore wave height indicating unsaturated surf the observations show a variation in gamma values from near constant values in the mid surf zone to rapidly and asymptotically increasing gamma values in the inner surf zone in contrast to previous data from saturated surf gamma shows no dependence on either the absolute beach slope or the relative beach slope beta k h over bar the skewness of the distributions of gamma w is consistent with waves that are not depth limited the inner surf zone wave heights are approximately equally dependent on the water depth and offshore wave height the previous observations of gamma from saturated surf are shown to be consistent with a terminal bore height at the shoreline which is in excellent agreement with a previously derived value for the miche parameter in contrast for the present unsaturated surf conditions the terminal bore height at the shoreline can be approximated by h b approximate to 0 12h o which is consistent with recent laboratory data sets

the role of combined laser scanning and video techniques in monitoring wave by wave swash zone processes abstract simulating swash zone morphodynamics remains one of the major weaknesses of beach evolution models one of the reasons is the limited availability of data on morphological changes at the temporal scales of individual swash events this paper sets out to present a new hybrid system consisting of 2d 3d laser scanners and several video cameras which was designed to monitor swash zone topographic change on a wave by wave basis a methodology is proposed consisting of sensor calibration and several data processing steps allowing a fusion of different sensors such an approach can improve the performance of several field laboratory optical technique applications for nearshore hydro and morpho dynamic measurements digital elevation models from a 3d scanner were used in the extrinsic camera calibration procedure and reduced the geo rectification errors from 0 035 m dz 10 cm the sediment transport direction and intensity of the monitored swash events was relatively balanced and sediment transport rates ranged between 3 5 kg m 1 s 1 q t 3 5 kg m 1 s 1 extreme transport swash events became rarer as the morphology was reaching equilibrium

overwash threshold for gravel barriers abstract this paper uses results obtained from the large scale bardex experiments undertaken in the delta flume to investigate the morphological response of a prototype gravel barrier to wave and tidal forcing during overwash conditions gravel barrier behaviour depends upon a number of factors such as sediment properties porosity permeability grainsize geological setting and wave climate since overwash processes are known to control short term gravel barrier dynamics and long term barrier migration the development of a robust quantitative method to define the critical conditions leading to gravel barrier overwashing is important both for scientific and practical management purposes it is known that when wave runup exceeds the barrier crest elevation three outcomes are possible 1 insignificant morphological change when wave runup just overtops the barrier crest and flow velocities are very weak 2 overtopping resulting in accretion on the barrier crest region and barrier stabilisation and 3 overwashing resulting in erosion lowering of the crest region and ultimately to barrier inundation this study provides an insight into the critical conditions that distinguish these two possible outcomes and to the different mechanisms that provide the required positive and negative feedbacks to the sediment dynamics in order to define the overwash threshold condition and to predict the morphological outcome of particular overwash events use is made here of the overwash potential op defined as the difference between the wave runup and the barrier crest elevation to make effective use of op it is necessary to identify a reliable runup predictor following tests using 12 runup equations the stockdon et al stockdon h f holman r a howd p a sallenger a h 2006 empirical parameterization of setup swash and runup coast eng 53 573 588 approach has been identified as the best predictor of runup conditions necessary to generate positive values of op with overtopping and overwashing predicted to occur for average op values of 0 2 m and 0 5 m respectively the use of op values provides a practical means by which to identify potential coastal hazards associated with gravel barrier overwash processes and is considered to have a range of practical coastal management applications

modelling gravel barrier response to storms and sudden relative sea level change using xbeach g abstract this paper investigates the response of a mixed sand and gravel msg barrier coastline to storms and sudden relative sea level change using the numerical model xbeach g the barrier beaches of southern hawke s bay new zealand provide a natural laboratory for the work owing to spatial variability in instantaneous land deformation that occurred during the 1931 hawke s bay earthquake historic 1931 and contemporary 2017 morphodynamics of one tectonically uplifted 1 5 m and one subsided 0 78 m barrier were modelled under energetic waves hs 1 6 m xbeach g was designed to simulate pure gravel beach morphodynamics but despite this the model demonstrated high quantitative skill when calibrated for the msg coast results reveal the storm impact regimes of each profile and potential linkages to decadal scale barrier development observed in historical beach profile data storm swash processes at the uplifted profile indicate long term barrier stability due to a lack of change at the barrier crest and ridge building observed in model simulations provides a potential formative mechanism for decadal scale beach progradation at the subsided barrier modelled historic crest build up up to 0 3 m and narrowing over 5 m indicate an overtopping mode of response to sudden relative sea level rise simulation results are consistent with historical beach profile observations that also show chronic narrowing of the subsided barrier through time simulations of the modern barrier draw attention to the possibility that it may be on a trajectory toward catastrophic breakdown under extreme conditions but further work is needed to distinguish the relative importance of historical sudden sea level rise versus deficits in sediment supply to this shoreline

high frequency in situ field measurements of morphological response on a fine gravel beach during energetic wave conditions this paper presents novel data collected over four weeks at loe bar a fine gravel barrier d50 3 5 mm exposed to energetic wave conditions hs10 2 4 m combined remote and in situ measurements were used to identify 3d morphological response profile change and runup behaviour during successive energetic periods hs 2 5 m small intertidal beach volume losses occurred under high steepness waves h0 l0 0 01 but in general the overall beach volume was remarkably stable in fact the greatest morphological response was evident not in cross shore sediment exchanges but due to the alongshore redistribution related to the three dimensional beach cusp system specifically during energetic wave conditions the cusp morphology underwent horn growth and embayment deepening leading to increased cusp definition an additional explanation for the stability of the cross shore beach profile is related to the development of the beach step during energetic conditions and long period waves significant deposition c 1 m occurred at the top of the beach step above the still water line the enhanced step provided a focal point for wave breaking considerably curtailing the swash motion and reducing the runup limit thereby providing protection to the upper beach this study provides much needed insight into complex morphological response and runup characteristics on gravel beaches fundamental for improved model development and leading towards better predictive tools

swash zone boundary conditions derived from optical remote sensing of swash zone flow patterns 1 optical remote sensing is used to measure flow patterns in the swash zone timestack images are analyzed to measure the asymmetry and the relative duration of the inflow into the swash zone this varies significantly between individual swashes contrary to the classical analytical swash model for runup induced by bores which predicts a similar flow pattern for all events for swash forced by breaking bores the gradient of the x t locus of flow reversal varies over a wide range and flow reversal can occur simultaneously across the whole swash zone this variation of the gradient of the locus of flow reversal in x t space can be parameterized in terms of a single free variable in recent solutions to the nonlinear shallow water equations which fully defines the swash boundary inflow condition consistent with the theory the horizontal runup the swash period and the swash similarity parameter were observed to be independent of the swash inflow conditions but the flow asymmetry is not only a weak correlation was observed between the swash boundary condition and the iribarren number and beach slope conversely the analysis suggests that the degree of swash swash interaction does influence the swash boundary condition and the resulting internal flow kinematics the variation in inflow conditions is expected to influence the magnitudes of the velocity moments within the swash zone and therefore sediment transport rates

surface groundwater flow numerical model for barrier beach with exfiltration incorporated bottom boundary layer model abstract a surface groundwater flow model is developed for the swash flow on a barrier beach the non linear shallow water equations are used to simulate the surface flow laplace s equation is used to describe the groundwater flow and is solved using the boundary integral equation method to provide potential heads and normal potential derivatives at and within the boundaries of the barrier an exfiltration incorporated bottom boundary layer sub model is used to obtain bed shear stress the groundwater model is verified against the numerical test results in kazemzadeh parsi and daneshmand 2012 for the groundwater flow through a rectangular dam the coupled surface groundwater model is validated against the prototype scale bardex ii experimental results turner et al 2016 the steady state groundwater flow comparisons show excellent agreement in phreatic surfaces the comparisons of groundwater flow under the action of waves show reasonably good agreement with experimental results in phreatic surfaces the simulated time averaged pore velocities for the runs with and without waves are in satisfactory agreement with experimental results in general and certain discrepancies are observed near the beach side the bed shear stress variation due to exfiltration is investigated by incorporating the modified logarithmic bottom boundary layer model of cheng and chiew 1998 in the coupled surface groundwater flow model the results confirm that as exfiltration increases bed shear stress decreases as a result of thickening of the bottom boundary layer

cross shore sediment transport on natural beaches and its relation to sandbar migration patterns 1 field observations and derivation of a transport parameterization 1 cross shore sediment transport processes are investigated with measurements of horizontal velocity and sediment suspension obtained with electromagnetic current meters and optical backscatter sensors on five different beaches across europe data were gathered under a wide variety of hydrodynamic and morphological conditions spanning the swash surf and shoaling zones results show that the near bed velocity moments normalized by the local energy level ut2 n have consistent shapes shape functions when plotted against normalized cross shore depth h hb according to the energetics approach near bed velocity moments are good descriptors of sediment transport processes consequently the shape functions describe and quantify the cross shore distribution of the most relevant cross shore sediment transport processes the pattern consists of net onshore transport in the swash zone offshore transport in the surf zone and onshore transport in the shoaling zone thereby producing divergence of sediment in the inner surf swash zone and convergence in the breaker zone in consequence the shape function supports the breakpoint hypothesis for sandbar generation this behavior is a product of the balance between multiple opposing mechanisms including undertow coupling between mean flows and short long wave stirring short long wave skewness and long wave coupling with short wave variance the cross shore structure of the measured and normalized cross shore sediment fluxes is consistent with the velocity moment shape functions showing the robustness of the approach apart from the shortcomings bound to the energetics approach the present parameterization is also limited due to the difficulty of defining with confidence a breaker depth hb in bar trough systems

wave runup video motion detection using the radon transform abstract a new method of runup detection from video imagery is introduced and validated at an energetic dissipative beach the instantaneous waterline is detected from uprush and backwash by using the radon transform rt the method is compared to conventional color contrast method from rgb images and lidar measurements in our observations the rt shows better detection skill even for adverse conditions such as those present on flat dissipative swash zones where contrast is reduced because the rt is a proxy of deeper waterline 0 1 m it is less sensitive to lack of contrast due to sand saturation moreover since it is based on motion detection it is less sensitive to changes in lighting conditions overall the rt offers an attractive alternative for long term automated detection of the runup

effects of cross channel bathymetry and wind direction on destratification and hypoxia reduction in the chesapeake bay abstract a coupled estuarine hydrodynamic model and water quality model were used to analyze differences in destratification and anoxia hypoxia reduction by wind directions in the north south oriented chesapeake estuary usa the predominant cross channel bathymetry in the bay s anoxic center is asymmetric with a steeper and narrower shoal on the eastern shore than on the western shore which modifies wind induced circulation differently for two opposite wind directions model experiments of winds for 2 day at 8 m s indicated that for a stratified water over the aforementioned asymmetric bottom topography the easterly wind caused greater destratification and hypoxia reduction than the westerly wind this is a result of differential modulations on the two wind induced cross channel circulations by the asymmetric cross channel bathymetry the downwelling along the gentle slope in the easterly wind was characterized with stronger baroclinicity than the downwelling along the steep slope nearly perpendicular to surfaces of constant density in the westerly wind on the broad slope there undergo greater contrasting density readjustments to the vorticity changes around the bottom boundary layer bbl during upslope and downslope motions during the upslope condition the flow in bbl tends to decelerate under adverse pressure gradient which leads to a stable condition in the outer layer whereas during the downslope condition the bbl tends to accelerate under favourable pressure gradient which leads to unstable condition in the outer layer of the large scale flow overall the easterly wind caused greater anoxia reduction than the westerly wind during the entire wind period a similar case was found for northerly versus southerly winds in the early stages of the wind period modulated by the aforementioned bathymetry on the wind induced cross channel circulation the northerly wind caused greater anoxia reduction than the southerly wind however as wind continues the wind induced along channel circulation influences a larger area of greater hypoxia in the mid bay by which the southerly wind causes a greater destratification and anoxia reduction than the northerly wind this can supersede the greater destratification and anoxia reduction by the northerly wind under the bathymetry affected cross channel circulation

an experimental study on sediment transport and bed evolution under different swash zone morphological conditions in this study new large scale experimental data are presented showing evidences of a link between the swash zone dynamics and the surf zone morphodynamics two sets of large scale experiments are presented the first set of experiments investigates the swash and surf dynamics under the same hydrodynamic forcing but with two different swash zone morphological conditions one of which was created by manual reshaping of the sub aerial beach face it is shown that more dissipative swash zone conditions a more mildly sloping beach face significantly reduce the rate of seaward sandbar migration such that it almost ceases during the performed experimentation time this behavior is compared to a second set of experiments which shows the natural sand bar offshore migration under almost identical hydrodynamic forcing the changes in the sandbar migration are investigated in terms of the differences in the swash zone dynamics the more reflective swash zone is characterized by more intense backwashes that in turn promote significant quantities of sediment suspension during the interaction of the backwash with the subsequent bore the dissipative swash zone leads to a larger number of wave swash interactions reducing the backwash magnitudes and the magnitude of suspended sediment concentration events in the swash zone with a corresponding reduction in the offshore suspended sediment transport the total offshore sediment transport rates are also shown to reduce leading to the observed modification of the sandbar migration

distributions for wave overtopping parameters for stress strength analyses on flood embankments a process based assessment of the probability of failure of a flood embankment as well as an assessment of the consequences of failure of an embankment require insights into the stresses on the landside slope of an embankment these assessments are hindered by the empirical nature of the wave overtopping parameters failure initiation is often linked to an allowable mean overtopping discharge which forms the input for the overtopping volumes distribution the high level of uncertainty associated with predicting the mean overtopping discharge therefore leads to high levels of uncertainty in predicting wave overtopping volumes the mean overtopping discharge is thereby not directly related to run up parameters this paper addresses these issues by presenting new distributions for the velocity discharge depth volume and shear stresses at the crest for those waves that overtop which have been derived from the wave run up parameters the proposed distributions are independent on the mean wave overtopping discharge and the large inaccuracies associated with predicting this the proposed method has the added benefit of being able to express overtopping parameters in terms of each other the paper also provides a method for determining the change in these random overtopping values along the landside slope thereby facilitating a direct comparison between wave overtopping events and overflow events

a novel method for tracking individual waves in the surf zone a new method to obtain information on individual waves as they travel shoreward is described the wave tracking method involves analysis of synchronous water level records obtained from a shore normal transect of pressure transducers pts the method is illustrated here using data from field deployments inside the surf zone although the method could equally be applied outside the surf zone as a wave travels shoreward along the instrument transect it appears in the pt records at a progressively later time serial cross correlation techniques are used to shift each record in time so that each wave in the first record aligns approximately with the corresponding wave if it exists in subsequent records from along the transect a local minima analysis power et al 2010 is used to delimit individual waves in each record and then parameters of interest can be determined for each wave at each pt location the wave tracking method provides the evolution of these parameters for a single wave as it travels to shore and they can be analysed as a function of distance or local water depth the utility of the method is illustrated with case studies including the evolution of wave height and the evolution of the ratio of wave height to water depth for surf zone waves

estimation of wave phase speed and nearshore bathymetry from video imagery a new remote sensing technique based on video image processing has been developed for the estimation of nearshore bathymetry the shoreward propagation of waves is measured using pixel intensity time series collected at a cross shore array of locations using remotely operated video cameras the incident band is identified and the cross spectral matrix is calculated for this band the cross shore component of wavenumber is found as the gradient in phase of the first complex empirical orthogonal function of this matrix water depth is then inferred from linear wave theory s dispersion relationship full bathymetry maps may be measured by collecting data in a large array composed of both cross shore and longshore lines data are collected hourly throughout the day and a stable daily estimate of bathymetry is calculated from the median of the hourly estimates the technique was tested using 30 days of hourly data collected at the sandyduck experiment in duck north carolina in october 1997 errors calculated as the difference between estimated depth and ground truth data show a mean bias of 35 cm rms error 91 cm expressed as a fraction of the true water depth the mean percent error was 13 rms error 34 excluding the region of known wave nonlinearities over the bar crest the accuracy of the technique improved and the mean rms error was 20 cm 75 cm additionally under low amplitude swells wave height h 1 m the performance of the technique across the entire profile improved to 6 29 of the true water depth with a mean rms error of 12 cm 71 cm

measurements and modelling of the advection of suspended sediment in the swash zone by solitary waves novel laboratory experiments and numerical modelling have been performed to study the advection scales of suspended sediment in the swash zone an experiment was designed specifically to measure only the sediment picked up seaward of the swash zone and during bore collapse the advection scales and settling of this sediment were measured during the uprush along a rigid sediment free beach face by a sediment trap located at varying cross shore positions measurements were made using a number of repeated solitary broken waves or bores approximately 25 of the pre suspended sediment picked up by the bores reaches the mid swash zone 50 of the horizontal run up distance indicating the importance of the sediment advection in the lower swash zone the pre suspended sediment is sourced from a region seaward of the shoreline still water line which has a width of about 20 of the run up distance an eulerian lagrangian numerical model is used to model the advection scales of the suspended sediment the model resolves the hydrodynamics by solving the non linear shallow water equations in an eulerian framework and then solves the advection diffusion equation for turbulence and suspended sediment in a lagrangian framework the model provides good estimates of the measured mass and distribution of sediment advected up the beach face the results suggest that the correct modelling of turbulence generation prior to and during bore collapse and the advection of the turbulent kinetic energy into the lower swash is important in resolving the contribution of pre suspended sediment to the net sediment transport in the swash zone c 2009 elsevier b v all rights reserved

a novel machine learning algorithm for tracking remotely sensed waves in the surf zone abstract this paper describes a novel image processing technique that detects wave breaking and tracks waves in the surf zone using machine learning procedures using time space images timestacks the algorithm detects white pixel intensity peaks generated by breaking waves confirms these peaks as true wave breaking events by learning from the data s true colour representation clusters individual waves and obtains optimal wave paths the method was developed and tested using data from four sandy australian beaches under different incident wave and light conditions results are a representation of the position of the wave front through time i e space time data which when shown overlaid on the original timestack shows the high degree of accuracy of the method developed here the utility of the method is demonstrated in two ways 1 through a comparison between the instantaneous wave speed calculated from the wave paths with the theoretical shallow water wave speed and 2 by obtaining optical intensities that could be translated into wave roller lengths the algorithm developed here has the potential to improve understanding numerous nearshore process such as bore propagation and capture in the surf zone surf zone energy dissipation surf beat and infragravity waves and as a direct speed input for depth inversion methods

wave reflection from coastal structures in design conditions based on an extensive database of more than 4000 data this paper analyses wave reflection for various types of coastal structures in design conditions such as smooth rock and armour unit slopes a new simple formula has been developed that relates the reflection coefficient to the breaker parameter and seems to fit all kinds of revetment materials by changing two coefficients these coefficients depend only on the correct roughness factor provided by recent research on overtopping discharges the effects on reflection due to composite slopes and to low crests are also examined and proper extensions of the formula are provided 2008 elsevier b v all rights reserved

vertical structure of the undertow outside the surf zone the vertical structure of the undertow in the shoaling region outside the surf zone is quite different from that inside the surf zone inside the surf zone the undertow typically has a large seaward directed velocity near the bottom and either a shoreward directed or a small seaward directed velocity at trough level measurements show that outside the surf zone the undertow has a small seaward directed velocity near the bed and a large seaward directed velocity at trough level in this paper we develop theoretical expressions for the undertow outside the surf zone and show that the steady streaming from the bottom boundary layer which was earlier found to have a negligible effect in the surf zone svendsen et al 1987 does have a significant influence on the vertical structure of the undertow in that region

formation and development of a breaker bar under regular waves part 1 model description and hydrodynamics abstract in this work a detailed hydrodynamic model is presented which is used for the study of cross shore sediment transport and morphodynamics in two dimensions the model is described in the framework of the generally unstructured finite volume method considerable emphasis is put on those subtleties in the morphological formulation which are required to achieve mass conservation for the amount of sediment in the bed and in suspension in this first part of two the hydrodynamic description over the cross shore profile is presented the model is validated against an experiment with detailed measurements of the free surface and turbulence over a fixed breaker bar profile a test matrix covering a large interval of the surf similarity parameter is simulated and the phase lag between the breakpoint and the initiation of the setup is described the relation of this phase lag to a cross shore delay in dissipation of organised energy into turbulence is described the relation of this phase lag to the distribution of the location of maxima in bed shear stresses and magnitude of the undertow is also described furthermore processes in the hydrodynamics which will have a smoothing effect on the mean cross shore sediment transport and morphodynamic response are considered all simulations are presented for regular waves and for values of the deep water surf similarity parameter 0 in the range from 0 08 to 1 19 i e covering both spilling and plunging breakers