numerical assessment of infragravity swash response to offshore wave frequency spread variability this work has been funded under 1 the retos investigacion 2014 grant bia2014 59718 r program of the spanish ministry of economy and competitiveness and 2 the neptune 2 project l r 7 2007 by regione autonoma della sardegna

infragravity swash parameterization on beaches the role of the profile shape and the morphodynamic beach state abstract a field campaign was undertaken at somo beach in northern spain with the aim of understanding the processes involved in the generation of low frequency swash taking the parameterization presented in earlier studies as a starting point a novel empirical model was defined based on a database which included datasets from somo beach and from 9 other experiments this new parameterization was obtained by relating the horizontal cross shore component of the infragravity swash to the foreshore slope and the morphodynamic beach state through the non dimensional fall velocity parameter the role of previous sea states when determining the morphodynamic beach state was also assessed a strong correlation between low frequency oscillations and the morphology of the beach was verified resulting in a substantial improvement over existing infragravity swash predictions proposed in the literature

runup setup and the coastal watertable the three related phenomena of wave runup wave setup and the dynamics of the coastal watertable are considered and their inter relations are investigated via a comprehensive field study the measured runup distributions confirm the expectation that the rayleigh distribution is a reasonable model and that the vertical scale of the distributions is proportional to v horm8 l0 as in hunt s 1959 formula but that the proportionality to the beach slope also prescribed by this formula only applies for fairly steep beaches the measured setup profiles are quite different from the ones predicted on the basis of h 7h and linear wave theory in the surf zone the measured profiles are flatter in the outer surf zone and steeper close to the beach the shoreline setup is generally about 0 4 horms which is somewhat higher than the previously suggested values this is because the previous values of the shoreline setup were rarely measured but generally extrapolated with insufficient recognition of the steepening of the profile near the shoreline the watertable data show that the inclined beach face acts as a strongly non linear filter which makes the watertable variation at a point inside the beach far from sinusoidal when the tide is approximately sinusoidal and elevates the average position of the watertable considerably compared to the mean sea level

coastal gravel barrier hydrology observations from a prototype scale laboratory experiment bardex abstract a prototype scale laboratory study bardex barrier dynamics experiment was conducted within the 250 m long and 7 m deep delta wave flume the netherlands a 4 m high and 50 m long gravel barrier d50 11 mm was constructed within the central region of the flume enabling a back barrier lagoon to be located at its landward side by the installation of a multi stage pump system the water levels at the sea and lagoon sides of the barrier could be manipulated independently a series of experiments were undertaken to examine the groundwater fluctuations and flow within the barrier system subject to varying lagoon levels and wave conditions in accordance with previous sand experiments the wave induced watertable over height at the beachface was confirmed to be independent of sediment characteristics varying back barrier lagoon levels were observed to have significant effect on both the maximum watertable over height within the barrier and shoreline set up vertical position of the point of intersection between mean water surface through the swash zone and beachface as well as the direction and magnitude of though barrier groundwater flux the effective hydraulic conductivity of the d50 11 mm gravel barrier was determined to be k 0 16 m s 1 at higher reynolds numbers re 40 associated with local watertable gradients exceeding 0 025 and resulting turbulent losses the transition from laminar to turbulent through barrier flow was indicated by a reduction in local k however for the parameter range encountered this effect was modest only

storm induced response of a nearshore bar system abstract a nearshore bar system was surveyed periodically through a storm and the following recovery period the data showed a very rapid response of morphology to changing wave conditions and allowed various models on bar formation to be tested under low energy conditions prior to the storm a small bar was surveyed 13 m offshore both the high reflectivity of the beach and the cross shore distance to the bar are consistent with a model of sediment convergence at the node or antinode of a standing wave of incident period such a small scale bar may be a common feature on beaches with steep foreshores and more gentle offshore slopes with the increase in wave height during the storm the bar became better developed and migrated offshore at rates up to 2 2 m h 1 the bar maintained its form in that the ratio of trough depth to crest depth h t h c remained roughly constant the bar was in no way related to processes which would cause the convergence of sediment in the breaker zone through most of the storm the bar crest distance offshore was typically only 10 of the surf zone width analysis of the bar distance offshore in terms of a standing wave motion showed that the causative wave period must have been much longer than that of incident waves probably on the order of a minute surf zone wave data showed significant energy in the infragravity band at these periods although no definite link has been made after the height of the storm the bar had a crescentic morphology the development of this morphology occurred very rapidly with parts of the bar migrating onshore at rates up to 1 2 m h 1 in contrast to the storm during the recovery period h t h c varied by nearly a factor of three analysis of the offshore and longshore length scales showed the bar to be similar to one which would be generated by a standing mode 1 edge wave of period on the order of one minute

surf zone currents over irregular bathymetry drifter observations and numerical simulations 1 surf zone currents over irregular bathymetry were observed with gps tracked drifters and modeled with the depth integrated nonlinear shallow water equations trajectories of drifters released in 1 2 m depth sometimes defined rip currents and surf zone eddies features that have been difficult to resolve with fixed instruments the drifter delineated surf zone circulation evolved as the tidal level changed during each 4 6 hour deployment in one case as the tide dropped a shore normal rip current present for the first 2 hours evolved to a more shore parallel flow in a second case on a rising tide a well developed bifurcated rip current was replaced by a weak amorphous circulation rip current velocities were strongest near the surf zone edge and decayed by an order of magnitude within 2 surf zone widths from the shoreline an eddy was observed to persist over a bathymetric depression within the surf zone for at least 1 hour observed and numerically simulated drifter trajectories define similar flow features but the observed and modeled velocities differed by roughly a factor of 2 and flow evolution observed during roughly 0 5 m changes in tidal level were reproduced only if the simulated water levels varied by about 1 m the alongshore momentum balance was spatially variable with wave forcing balanced by pressure gradient friction and advective terms the cross shore momentum balance was everywhere dominated by wave forcing and pressure gradient terms of about equal magnitude in the vicinity of a simulated rip current the residual of the cross shore wave forcing and pressure gradient increased and was balanced by advection terms

processes of selective grain transport and the formation of placers on beaches placers are found on many beaches of the oregon coast in the beach that is the focus of this study the principal placer minerals are ilmenite 22 0 epidote 20 0 garnet 18 7 augite 15 5 hypersthene 8 1 hornblende 5 8 and zircon 2 0 the ilmenite fraction actually being partly chromite a series of beach face sand samples was obtained along a profile when sand was being eroded from the upper beach and transported to offshore bars since the processes of grain selective sorting leading to placer formation were probably most active at such a time the landward most sample contained 96 heavy minerals being part of the placer this concentration systematically decreased offshore to a 6 heavy mineral content in the seaward most sample 54 m offshore determinations of individual heavy mineral concentrations revealed that although they all tended to become concentrated within the placer with light quartz and feldspar dominating the offshore transport the sorting processes were m

simulating wave setup and runup during storm conditions on a complex barred beach abstract the purpose of this study is to assess the ability of the swash model to reproduce wave setup and runup in highly dissipative stormy conditions to proceed we use data collected during the ecors truc vert 08 experiment especially during the johanna storm in the winter of 2007 008 wave setup under hs 8 2 m and tp 18 3 s and runup under 6 4 m and peak period up to 16 4 s we test different model settings 1d and 2d mode and model forcing spectral and parametric to reproduce sensor measured wave setup at several locations in the nearshore area and video measured runup on two beach profiles for the whole tested configurations the wave setup is reproduced accurately results considering all the sensor locations in the near shore area in 1d and 2d are significantly correlated to the observations with respectively 0 66 and 0 81 rmse 0 13 m and 0 08 m without any significant bias observations and simulations of runup are investigated in terms of spectra and statistic component 1d simulations produces an overall overestimation and no significant improvement is obtained by modifying the breaking parameters the results for 2d simulations are fairly satisfactory reproducing significant swash height s but are significantly improved with spectral forcing than parametric with respectively 0 73 and 0 71 rmse 0 19 m and 0 43 m generally the model reproduces accurately the infragravity component but tends to overestimate the incident component leading to an overestimation of the energy density for moderate wave conditions and more accurate results for higher energy wave conditions results in 2d with spectral forcing show a saturation of the infragravity component with a threshold around hs 4 to 5 m which is comparable to the observations collected at truc vert beach as regards the conventional statistical parameter for runup estimation r2 three methods are applied to derive the 2 exceedence value for runup from observed and simulated shoreline vertical elevation time series when r2 is based on the sum of wave setup and half of the significant swash height results provided by the model are close or even better than estimations provided by empirical formulas from the bibliography defining r2 as the exceeded 2 values of the time derived considering the cumulative distribution function of the entire water level time series also provide fairly good results results using only runup maxima time series are less satisfactory in the two last cases r2 is slightly underestimated for moderate wave conditions hs

field observations of swash zone infragravity motions and beach cusp evolution 1 fluid flows consistent with low mode edge waves were evident in video observations of swash motions during a field experiment in which beach cusps developed on an initially smooth beach as beach cusps grew energy lying along low mode dispersion curves increased the most energetic edge wave propagation direction changed from upcoast to downcoast as the orientation of the cusp horns rotated these observations suggest a coupling between morphodynamics and hydrodynamics and are evidence that beach cusp evolution might control low mode edge wave dynamics

exchange between long island sound and adjacent waters 1 we exploit archived salinity data averaged by month for the years 1995 2001 to evaluate exchange of salt between long island sound and shelf waters and treat long island sound as a control volume with eastern and western boundaries at the race and the east river respectively the use of inverse methods to solve a system of equations expressing conservation of salt and water provides estimates of model parameters together with uncertainty estimates and measures of model performance we explore the use of a single exchange coefficient acting on an axial salinity gradient to represent exchange at the race and find that it is necessary to allow the coefficient to depend weakly on variability of freshwater discharge r into the sound i e 0 2 1 600 200 m2 s using established estimates of the mean circulation at the western boundary of the sound we determine a dispersion coefficient in the upper east river of 300 200 m2 s explicitly modeling the advective exchange flow gravitational circulation at the race using a coefficient that varies as the one third power of the normalized discharge indicates that gravitational circulation accounts for less than 10 of the up estuary salt flux in eastern long island sound

wave energy saturation on a natural beach of variable slope time series of flow were measured across the inner surf zone during a storm these data were used to quantify the dependence of wave height transformed from measured flow and velocity on local slope and depth similar to previous studies as incident waves broke and propagated into the surf zone wave energy became saturated and wave height was strongly dependent on depth however the ratio of rms wave height to local depth rms was found not to be constant but to vary between 0 29 and 0 55 rms increased with local slope and was independent of deepwater wave steepness thus the surf zone similarity parameter the ratio of slope to the square root of steepness did not adequately parameterize rms

advances in swash zone research small scale hydrodynamic and sediment transport processes abstract extensive research efforts in the last decade have improved knowledge of swash zone processes this paper reviews and synthesizes from 2004 onward the research advances of small scale hydrodynamics and sediment transport processes considering field laboratory and numerical modeling efforts swash zone hydrodynamics are examined by means of shoreline motions fluid velocities pressure gradients flow structure bed shear stress friction coefficients and turbulence subsequently advances related to sediment transport mechanisms and morphological changes are described detailed descriptions of measuring techniques novel findings and the strengths and weaknesses of the different approaches are discussed the review also acknowledges the major advances in the development of instrumentation to collect highly resolved flow and sediment concentration measurements in direct proximity of the bed and the experimental framework for analyzing local dynamics on a wave by wave time scale e g dam break

swash oscillations on a natural beach run up swash oscillations were measured on a gently sloping beach face for a variety of incident wave conditions run up energy spectra at wind wave frequencies show an 3 dependence and energy levels that are independent of incident wave height this suggests saturation in contrast run up energy at surf beat periods increase approximately linearly with increasing incident wave energy thus in the inner surf zone where wave breaking limits the energy at wind wave frequencies the principal manifestation of large incident wind waves is energetic surf beat

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

static wave setup with emphasis on damping effects by vegetation and bottom friction abstract wave setup can contribute significantly to elevated water levels during severe storms in florida we have found that wave setup can be 30 to 60 of the total 100 year storm surge in areas with relatively narrow continental shelves such as many locations along the pacific coast of the united states wave setup can be an even larger proportionate contributor of anomalous water levels during major storms wave setup can be considered as comprising two components with the first being the well known static wave setup resulting from the transfer of breaking wave momentum to the water column the second oscillating component is a result of nonlinear transfer of energy and momentum from the primary linear spectrum to waves with length and time scales on the order of the wave groups static wave setup is the focus of this paper with emphasis on effects due to internal or surface forces that act on the wave system and cause both dissipation of wave energy and transfer of momentum in particular the effects of wave damping by vegetation and bottom friction are considered linear wave theory is applied to illustrate these effects and for shallow water waves the setup is reduced by two thirds the amount that would occur if the same amount of energy dissipation occurred in the absence of forces effects of nonlinear waves are then considered and it is found for a shallow water wave of approximately one half breaking height that a wave setdown rather than setup occurs due to damping by vegetation and bottom friction the problem of wave setup as waves propagate through vegetation was stimulated by studies to establish hazard zones associated with 100 year storm events along the shorelines of the united states these storms can generate elevated water levels exceeding 4 to 6 m and can result in overland wave propagation as these waves propagate through vegetation and damp the question arose as to the contribution of this process to elevated mean water levels through additional wave setup

morphodynamic evolution of a coastal lagoon entrance during swash overwash new field observations of beach berm growth resulting in the sub aerial closure of an intermittently closed and open lake or lagoon are presented these perched estuarine systems frequently exhibit ephemeral entrances that respond to process forcing almost instantaneously on a geomorphic timescale with closure by a supra tidal berm of depositional origin the observations were made following a mechanical opening of the entrance and show very rapid vertical growth of an initially low beach berm as a result of swash overtopping and sediment overwash very little simultaneous seaward progradation was observed sediment overwash volumes were obtained from survey data over a period of 12 days either side of spring tide and the observations also provide an accurate measure of swash sediment transport at the berm crest a process based parametric model is developed through robust parameterisations of wave run up wave run up distributions and sediment transport and is applied to predict the total overwash transport into and infilling the estuary entrance the model is tested against the field data and compares well with the observations while the field data are site specific the proposed modelling framework represents a first step in modelling the complex growth and recovery of natural beach berms in broad scale morphodynamic models

wave set up wave run up and beach water table interaction between surf zone hydraulics and groundwater hydraulics the relationship between wave set up wave run up and beach water table is reviewed starting from the work and ideas of nielsen and using laboratory observations of wave set up and beach water table in beaches formed from various beach materials under similar wave conditions a new more extensive analysis of wave set up on impermeable fixed plane beaches has been made using all available experimental data scaling parameters for set up and water depth based upon both deep water and breaking wave conditions and incorporating appropriate forms of the surf similarity parameter are developed the dimensionless set up parameters are of the form n long right leg n long right leg b h0 0 n where 0 3 n 0 5 for deep water wave parameters and n long right leg n long right leg b hb tan ib n where n 0 4 for breaking wave conditions 0 tan ho lo and ib hb 1 2 g 1 2 t tan

microwave radar cross sections and doppler velocities measured in the surf zone 1 the relationship between microwave imaging radar measurements of fluid velocities in the surf zone and shoaling breaking and broken waves is studied with field observations normalized radar cross section nrcs and doppler velocity are estimated from microwave measurements at near grazing angles and in situ fluid velocities are measured with acoustic doppler velocimeters advs joint histograms of radar cross section and doppler velocity cluster into identifiable distributions the nrcs values from pixels with large nrcs and high doppler velocities 2 m s decrease with decreasing bore height to the shoreline similar to scattering from a cylinder with decreasing radius the doppler velocities associated with these regions in the histograms agree well with theoretical wave phase velocities radar and adv measurements of fluid velocities between bore crests have similarly shaped energy density spectra for frequencies above about 0 1 hz but energy levels from the radar are an order of magnitude higher than those of the adv data instantaneous interbore doppler velocities are correlated with adv measured fluid velocities but are offset by 0 8 m s this offset may be due to bragg wave phase velocities wind drift range and azimuth sidelobes the finite spatial resolution of the radar and differences between mean flows measured at the surface with radar and flows measured below the surface with advs shoaling and breaking waves measured through radar grating lobes significantly affect both the doppler velocities near the edges of the images and the scattering from the rear faces of waves causing large doppler velocities to be observed in these regions

hydrodynamics and sediment transport in the swash zone a review and perspectives the dominant hydrodynamic forcing and resulting sediment transport mechanisms in the swash zone are reviewed combined with a discussion of future measurement and modelling requirements the importance of swash zone processes in the overall behaviour of the nearshore littoral zone are identified with the paper subsequently focusing on aspects that directly relate to sediment transport on beaches the review considers analytical and numerical modelling work and both field and laboratory data the hydrodynamics of the swash zone are first discussed with reference to the surf zone boundary swash characteristics forcing mechanisms and shoreline oscillations subsequent sections consider more micro scale processes such as the internal flow kinematics turbulence the bed boundary layer and infiltration exfiltration through permeable beds the second part of the paper outlines the fundamental mechanics of sediment transport in the swash zone followed by a more detailed discussion of sediment transport modes induced by the dominant hydrodynamic conditions modelling concepts are reviewed and the strengths and weaknesses of different approaches identified a final summary and future modelling perspectives conclude the paper

beach steps an evolutionary perspective abstract field observation of contrasting beach step behavior at canaveral national seashore on two subsequent days when incident wave conditions in the inner surf zone were similar prompted this re examination of our conceptual and quantitative understanding of beach steps these lower foreshore features are more complex than previously assumed evolving through erosional as well as accretional phases and displaying equifinality in geometric form but not necessarily internal sedimentary structure past and recent evidence is reviewed that links beach steps to incident waves at the surging plunging transition and to the action of a backwash vortex tides and low frequency waves likely play no direct role in beach step initiation although their presence can have pronounced influences on modulating nearshore hydrodynamics and thus on beach step maintenance and evolution a generalized conceptual model capturing these aspects of beach step dynamics is presented beach step initiation proceeds via step carving excavation or building depending on the erosional accretional character of the beach foreshore system subsequent evolution of the step form may take one of several alternative morphodynamic pathways including stepface retreat step drag down or step infilling elimination depending on tidal stage range or wave set up setdown additional data on equilibrium beach step forms and associated morphodynamic and hydrodynamic conditions in the field are necessary before quantitative models of beach step existence and evolution can be formulated with realistic results

simulating the influence of groundwater seepage on sediment transported by the sweep of the swash zone across macro tidal beaches abstract a numerical model is developed to simulate the influence of groundwater seepage on swash zone sediment transport across macro tidal beaches the emergence of equilibrium profile morphology is examined in response to varying tide sediment and initial profile characteristics due to the unresolved complexities of boundary layer flow and corresponding shear stresses in the swash zone sediment transport across the beach face is modelled by incorporating an uprush phase described by the shallow water wave equations within an heuristic model of equilibrium beach face slope a new parameter termed the m net transport parameter is defined to parameterize the net flux of sediment per uprush backrush cycle the definition of differing equilibrium gradients across saturated versus unsaturated regions of the intertidal profile permits the saturation characteristics of the bed to be incorporated the dynamics of the watertable exit point on the beach face is central to the scheme as this defines the time varying extent of saturated and unsaturated regions of the intertidal profile the sensitivity of coastal seepage face development to tide profile and sediment characteristics is highlighted through the derivation of a new seepage face parameter the simulation model is found to successfully reproduce key aspects of observed profile adjustment and resulting equilibrium morphology complex morphodynamic feedback is observed between the tidal stage net transport per uprush backrush cycle profile slope and the dynamics of the watertable outcrop net upper profile steepening and lower profile lowering is simulated on beaches composed of medium to coarse sand this results in the emergence of a distinctive break in slope within the intertidal profile such morphology is commonly observed on macro tidal coasts

a video based technique for mapping intertidal beach bathymetry abstract measuring the location of the shoreline and monitoring foreshore changes through time are core tasks carried out by coastal engineers for a wide range of research monitoring and design applications with the advent of digital imaging technology shore based video systems provide continuous and automated data collection encompassing a much greater range of time and spatial scales than were previously possible using field survey methods a new video based technique is presented that utilises full colour image information which overcomes problems associated with previous grey scale methods which work well at steep reflective sites but are less successful at flatter dissipative sites identification of the shoreline feature is achieved by the automated clustering of sub aqueous and sub aerial pixels in hue saturation value hsv colour space and applying an objective discriminator function to define their boundary i e shoreline within a time series of consecutive geo referenced images the elevation corresponding to the detected shoreline features is calculated on the basis of concurrent tide and wave information which is incorporated in a model that combines the effects of wave set up and swash at both incident and infragravity frequencies validation of the technique is achieved by comparison with dgps survey results to assess the accuracy of the detection and elevation methods both separately and together the uncertainties associated with the two sub components of the model tend to compensate for each other the mean difference between image based and surveyed shoreline elevations was less than 15 cm along 85 of the 2 km study region which corresponded to an horizontal offset of 6 m the application of the intertidal bathymetry mapping technique in support of czm objectives is briefly illustrated at two sites in the netherlands and australia

infragravity waves over a natural barred profile measurements of cross shore flow were made across the surf zone during a storm as a nearshore bar became better developed and migrated offshore measured infragravity band spectra were compared to synthetic spectra calculated numerically over the natural barred profile assuming a white run up spectrum of leaky mode or high mode edge waves as in earlier studies the spectra compared closely however for some frequencies the energy of the measured spectrum exceeded the energy of the synthetic spectrum suggesting that the run up spectrum was not white but had dominating frequencies utilizing cross shore flow data and synthetic spectra from a number of cross shore locations an equivalent run up spectrum was calculated for each day on the first day of the storm the equivalent run up spectrum indicated a dominant wave that had a node in velocity reasonably close to the bar crest later during the storm when the bar had migrated farther offshore there was no evidence for a dominant motion having a velocity node at the bar crest the structure of the equivalent run up spectrum compared well with spectra of direct measurements of run up obtained several hundred meters away we have no clear evidence in support of the theory that infragravity waves might form or force the offshore migration of a bar to confirm this finding longer records obtained synoptically over a developing bar are required the dominant wave observed early in the storm was consistent with symond and bowen s 1984 theoretical prediction of resonant amplification of discrete frequencies over a barred profile

wave setup and setdown generated by obliquely incident waves an analytical theory is developed for the wave setup and setdown induced by obliquely incident waves on an impermeable swell built beach profile the wave setup and setdown are found to decrease as wave obliquity increases the incorporation of wave obliquity in wave setup and setdown formulation offers the physical reality in engineering applications the general solutions presented in this paper yield the limiting case of normal wave incidence and the result is consistent with the classical theories published the present theory is primarily applicable to the spilling and plunging breaker across the surf zone within which wave amplitude is assumed to be linearly related to the local water depth experiments were conducted in a large scale wave basin to compare with theoretical results and especially to investigate the applicability of this assumption to the case of obliquely incident waves the dimensionless setup versus the distance offshore within the surf zone is found to depend on wave breaking angle and the shape of the beach profile and it has a non zero value at the original shoreline position this implies that the original shoreline will advance landwards and that the extent of this movement can be related to wave angle at breaking and the beach profile under consideration the results of the present theory are in good agreement with experimental data and field measurements available

importance of infragravity waves for the generation of washover deposits abstract washover deposits are among the most remarkable sedimentary signatures of dune breaching and coastal inundation overwash of the barrier leading to washover development can be related either to storms or tsunamis but the distinction between these two processes based on the depositional record is still a matter of debate hence studying recent well documented washover deposits combining sedimentological and hydrodynamic investigations is a key approach to identify the processes governing the washover deposition and to analyze their sediment record within the washover during the winter of 2013 2014 the coasts of the bay of biscay experienced an exceptional wave climate leading to dune breaching and washover deposition at many locations including the gatseau spit south of oleron island france field observations aerial photographs topographic measurements gpr investigations trenches and cores grain size analysis and magnetic fabric measurements were carried out and complemented with hydrodynamic modeling of tides storm surges short waves and infra gravity waves in order to compute maximum runup during the winter of 2013 2014 such an interdisciplinary approach led to propose that 1 large overwash events occurring during the winter of 2013 2014 were mainly driven by infra gravity ig waves combined with high tides 2 the washover elongated outer shape was strongly controlled by the antecedent morphology of the back barrier area 3 one overwash flow driven by one ig wave is recorded by one normally graded lamina composed of quartz sand at base and heavy minerals enriched sand at top 4 dominant settling of the particles from a suspension during sedimentation occurred in the end of each overwash flow in response to flow velocity decrease 5 laminae can be grouped in laminasets generally composed of thinning upward laminae related to overwash flow depth decrease during falling tide and to erosion of basal laminae by highest overwash flows occurring more likely around the high tide 6 the number of laminasets in a proximal position is in the same order of magnitude as the number of modeled highest runup events offering an almost complete record of overwash events that occurred during the winter 2013 2014

observations of swash under highly dissipative conditions video measurements of swash were made at the low sloping beach of the multiple bar system at terschelling netherlands the majority of the measurements were conducted under highly dissipative conditions with iribarren numbers 0 the ratio of beach slope to the square root of offshore wave steepness less than 0 2 infragravity 0 004 0 05 hz waves dominated the swash with an average ratio of infragravity and total swash height rig r of 0 85 using linear regression we investigated the dependence of swash parameters on environmental conditions such as short wave height period and local beach slope on average rig was about 30 of the offshore wave height h0 the slope in the linear h0 dependence of rig amounted to only 0 18 considerably smaller than that observed on steeper beaches the data set shows evidence for saturation of the higher infragravity frequencies for 0 less than roughly 0 27 in our opinion this saturation caused the constant of proportionality in the linear relationship between rig h0 and 0 to be significantly larger than that observed under higher iribarren number regimes the saturated tails of the swash spectra had an approximate f 3 roll off where f is frequency whereas in general the nonsaturated parts were white this lack of significant peaks casts doubt on the causality between infragravity waves and nearshore bars

swash groundwater dynamics in a sandy beach laboratory experiment abstract experiments are carried out in a wave basin in order to study the swash groundwater interaction a set of wave gages and pressure sensors are used to monitor the free surface and groundwater dynamics the study is based on the comparison of two selected cases which differ by the gravity and infragravity forcing conditions the features of wave breaking in the surf zone the presence of a standing wave attached to the beach face and the wave setup at the shoreline significant differences are observed in the response of the swash groundwater system the water table overheight appears to be controlled by the amount of infragravity energy available at the shore cyclic beach drainage processes can be observed when the water table is low significant time averaged and time resolved flows are observed into the sand depending on the swash hydrodynamics the presence of a gravity standing wave modulation attached to the shore is shown to affect swash and groundwater dynamics most of the pressure gradients observed under the swash zone are related to infiltration flows and are thus related to moderate increase of the sediment relative weight

an empirical model for infragravity swash on barred beaches abstract idealized computational simulations with the nearshore model xbeach were carried out for a series of barred beach configurations in order to quantify the impact of nearshore bars on infragravity swash results show that nearshore bar systems reduce infragravity swash energy at the shoreline the amount of swash reduction was found to correlate with both bar depth and rip width when a rip channel is present in order to develop a generalized empirical model for significant infragravity swash for barred beaches the simulations were used to extend the empirical swash model of stockdon et al 2006 to include bar characteristics the developed empirical model relates significant infragravity swash to incident wave conditions and nearshore bar depth with respect to stockdon et al 2006 this new model improves predictive skill by reducing root mean square error by 50 for the computational simulations and by 15 when applied to a range of field data

corrigendum to on the edge of camp geology and volcanology of the jurassic north mountain basalt nova scotia lithos 101 2008 74 101

the effects of tides on swash statistics on an intermediate beach 1 swash hydrodynamics were investigated on an intermediate beach using runup data obtained from video images under mild near constant offshore wave conditions the presence of a sandbar and the tidally controlled water depth over its crest determined whether most of the incoming waves broke before reaching the shoreline this forced a change in the pattern of wave energy dissipation across the surf zone between low and high tide which was reflected by changes to swash on time scales of a few hours significant runup height rs defined as 4 times the standard deviation of the waterline time series was found to vary by a factor of 2 between low tide when most of the waves were breaking over the sandbar rs hs 1 5 where hs is the offshore significant wave height and high tide when the waves were barely breaking rs hs 2 7 the increase in wave energy dissipation during low tide was also associated with changes in swash maxima distribution a decrease in mean swash period and increasing energy at infragravity frequencies bispectral analysis suggested that this infragravity modulation might have been connected with the presence of secondary waves

nonhydrostatic and surfbeat model predictions of extreme wave run up in fringing reef environments abstract the accurate prediction of extreme wave run up is important for effective coastal engineering design and coastal hazard management while run up processes on open sandy coasts have been reasonably well studied very few studies have focused on understanding and predicting wave run up at coral reef fronted coastlines this paper applies the short wave resolving nonhydrostatic xb nh and short wave averaged surfbeat xb sb modes of the xbeach numerical model to validate run up using data from two 1d alongshore uniform fringing reef profiles without roughness elements with two objectives i to provide insight into the physical processes governing run up in such environments and ii to evaluate the performance of both modes in accurately predicting run up over a wide range of conditions xbeach was calibrated by optimizing the maximum wave steepness parameter maxbrsteep in xb nh and the dissipation coefficient alpha in xb sb using the first dataset and then applied to the second dataset for validation xb nh and xb sb predictions of extreme wave run up rmax and r2 and its components infragravity and sea swell band swash sig and sss and shoreline setup were compared to observations xb nh more accurately simulated wave transformation but under predicted shoreline setup due to its exclusion of parameterized wave roller dynamics xb sb under predicted sea swell band swash but overestimated shoreline setup due to an over prediction of wave heights on the reef flat run up swash spectra were dominated by infragravity motions allowing the short wave but not wave group averaged model xb sb to perform comparably well to its more complete short wave resolving xb nh counterpart despite their respective limitations both modes were able to accurately predict rmax and r2

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

swash overtopping and sediment overwash on a truncated beach new experimental laboratory data are presented on swash overtopping and sediment overwash on a truncated beach approximating the conditions at the crest of a beach berm or inter tidal ridge runnel the experiments provide a measure of the uprush sediment transport rate in the swash zone that is unaffected by the difficulties inherent in deploying instrumentation or sediment trapping techniques at laboratory scale overtopping flow volumes are compared with an analytical solution for swash flows as well as a simple numerical model both of which are restricted to individual swash events the analytical solution underestimates the overtopping volume by an order of magnitude while the model provides good overall agreement with the data and the reason for this difference is discussed modelled flow velocities are input to simple sediment transport formulae appropriate to the swash zone in order to predict the overwash sediment transport rates calculations performed with traditional expressions for the wave friction factor tend to underestimate the measured transport additional sediment transport calculations using standard total load equations are used to derive an optimum constant wave friction factor of f w 0 024 this is in good agreement with a broad range of published field and laboratory data however the influence of long waves and irregular wave run up on the overtopping and overwash remains to be assessed the good agreement between modelled and measured sediment transport rates suggests that the model provides accurate predictions of the uprush sediment transport rates in the swash zone which has application in predicting the growth and height of beach berms c 2005 elsevier b v all rights reserved

edge wave trapping and amplification on barred beaches theoretical predictions show that edge waves may be trapped on bars providing a possible mechanism for bar growth simple solutions to the linear shallow water equations reveal that bar trapping is controlled by the depth of the water over the bar hbar and the geometry of the inshore trough relative to the bar for specific geometries amplification over the bar approaches an order of magnitude or more as the phase speed approaches where amplification is defined as the surface displacement over the bar relative to the surface displacement at the shoreline the amplification increases with the cross shore length scales of the profiles the amplification is somewhat frequency dependent generating stronger currents at the location of the bar in specific frequency ranges previous work showed that particular edge wave modes have the correct length scales to generate beach features such as bars and beach cusps but field observations notably shoreline run up data frequently show no evidence of edge wave energy being concentrated at the appropriate frequencies however for bar trapped modes edge wave energy is concentrated at the location of the bar therefore this edge wave energy will not necessarily be evident in shoreline measurements strong correlation exists between the energy distribution of the longshore component of the orbital velocity observed in data collected at superduck october 11 1986 and the distribution expected for a white edge wave spectrum at the shoreline this suggests that bar trapped edge waves exist in particular at incident wave frequencies

wave runup and overwash on a prototype scale sand barrier abstract accurate methods to predict wave runup are of critical importance to coastal engineers extreme runup during storm conditions can present a danger to coastal infrastructure and lead to dune overtopping and erosion overwash of barrier beaches and is an essential design parameter for certain coastal protection works this paper uses data obtained during the unique bardex ii prototype scale laboratory experiment on a reflective sand barrier to investigate wave runup and overwash runup measurements were acquired using ultrasonic altimeters 2d scanning lidar and camera systems under controlled wave and water level conditions it was found that extreme runup r 2 scaled well with the deepwater irribarren number where the beach slope was taken to be the beach face gradient the lower limit of the swash zone defined by the 2 wave rundown limit was also found to be a function of the irribarren number and was consistently below the swl in all tests the high resolution free surface measurements obtained using the ultrasonic altimeters and lidar enabled an analysis of the dynamics of individual swash events it was found that the vertical runup excursion of each swash correlated strongly with the height of the bore at collapse and could be predicted based on the assumption of a conversion of potential to kinetic energy at bore collapse

low frequency swash motion induced by wave grouping abstract this paper concerns the low frequency motion of swash directly induced by wave grouping on a steep beach a new experimental investigation is presented which considers the hydrodynamics of the inner surf zone and swash zone using vertical wave gauges and a run up wire results for regular waves wave groups and random waves are discussed with particular reference to low frequency motions the inner surf zone and swash zone are found to be unsaturated at incident short wave frequencies and as a result significant wave grouping is apparent at the shoreline the low frequency motion in the surf zone is found to be in phase with the incident wave grouping and may therefore be regarded as a time varying set up watson and peregrine 1992 the low frequency motion of the swash is shown to be an order of magnitude greater than that in the inner surf zone inconsistent with cross shore standing long waves for which no evidence is found we demonstrate that the low frequency motion of the shoreline provides an excellent approximation to the run up of individual bores and therefore describes the run up envelope spectral analysis shows that the low frequency motion of the swash is directly linked to the modulations in offshore wave height i e the low frequency energy in the incident wave envelope in addition the random wave run up spectra show an f 4 high frequency roll off as found by huntley et al 1977 the accumulated data show that unless the surf zone is totally saturated a significant proportion of the low frequency swash motion may be directly due to incident wave grouping and not standing long waves

influence of el nino southern oscillation enso events on the evolution of central california s shoreline significant sea cliff erosion and storm damage occurred along the central coast of california during the 1982 1983 and 1997 1998 el nino winters this generated interest among scientists and land use planners in how historic el nino southern oscillation enso winters have affected the coastal climate of central california a relative enso intensity index based on oceanographic and meteorologic data defines the timing and magnitude of enso events over the past century the index suggests that five higher intensity relative values 4 6 and 17 lower intensity relative values 1 3 enso events took place between 1910 and 1995 the enso intensity index correlates with fluctuations in the time series of cyclone activity precipitation detrended sea level wave height sea surface temperature and sea level barometric pressure wave height sea level and precipitation which are the primary external forcing parameters in sea cliff erosion increase nonlinearly with increasing relative enso event intensity the number of storms that caused coastal erosion or storm damage and the historic occurrence of largescale sea cliff erosion along the central coast also increase nonlinearly with increasing relative event intensity these correlations and the frequency distribution of relative enso event intensities indicate that moderate to high intensity enso events cause the most sea cliff erosion and shoreline recession over the course of a century

wave set up on a natural beach wave set up the superelevation of mean water level owing to the presence of breaking incident waves was measured at the shoreline of a natural beach offshore pressure sensors monitored incident wave conditions the set up of the shoreline was found to be about 0 17hs where hs is the significant wave height in deep water

wave variance partitioning in the trough of a barred beach the wave induced velocity field in the nearshore is composed of contributions from incident wind waves f 0 05 hz surface infragravity waves f 2 g where fis the frequency 2 f c is the radial alongshore wavenumber 2re l l being the alongshore wavelength is the beach slope and g is the acceleration due to gravity using an alongshore array of current meters located in the trough of a nearshore bar mean depth 1 5 m we investigate the bulk statistical behaviors of these wave bands over a wide range of incident wave conditions the behavior of each contributing wave type is parameterized in terms of commonly measured or easily predicted variables describing the beach profile wind waves and current field over the 10 day period the mean contributions to the total variance of the incident infragravity and shear wave bands were 71 5 14 3 and 13 6 for the alongshore component of flow mean rms oscillations of 44 20 and 19 cm s 1 respectively and 81 9 10 9 and 6 6 for the cross shore component mean rms oscillations of 92 32 and 25 cm s 1 respectively however the values varied considerably the contribution to the alongshore cross shore component of flow ranged from 44 888 4 58 5 95 8 for the incident band to 6 2 26 6 2 5 32 4 for the infragravity band and 3 433 1 0 6 14 3 for the shear wave band incident wave oscillations were limited by depth dependent saturation over the adjacent bar crest and varied only with the fide the infragravity wave rms oscillations on this barred beach are best parameterized by the offshore wave height consistent with previous studies on planar beaches comparison with data from four other beaches of widely differing geometries shows the shoreline infragravity amplitude to be a near constant ratio of the offshore wave height the magnitude of the ratio is found to be dependent on the iribarren number 0 h lo 1 2 shear waves are as previous observation and theory suggest oltman shay et al 1989 bowen and holman 1989 significantly correlated with a prediction of the seaward facing shear of the longshore current

the unsteady nature of sea cliff retreat due to mechanical abrasion failure and comminution feedbacks sea cliff retreat is often linked to large waves heavy precipitation and seismic events but the specific operative mechanics have not been well constrained in particular what is the role of mechanical abrasion by beach sediments in cliff platform evolution and how does it relate to the episodic nature of cliff retreat observed at certain locations here we present a simple numerical model of sea cliff retreat that incorporates mechanical abrasion of a basal notch threshold controlled failure of the cantilevered block and a feedback mechanism wherein retreat is dependent on the rate of sediment comminution within the surf zone using shore platform and cliff characteristics found in two coastal settings the central california coast and the english north sea coast the model produces retreat rates comparable to those observed via field measurements the highest retreat rates coincide with the steepest shore platforms and increasing wave height steeper platforms promote wave access to the cliff toe and correspondingly the receding cliff face produces additional accommodation space for the platform beach preserving the erosive efficacy of the beach sediments when exposed to energetic wave forcing the slope of the inner platform segment controls retreat rates for concave platforms whereas the slope of the outer platform segment exerts greater control for convex platforms platform beaches approached a long term dynamic equilibrium on the concave profiles leading to more consistent and steady retreat platform beaches were ephemeral on convex profiles mirroring observed sand wave ord migration on the holderness coast uk these findings agree with previous field observations and support mechanical abrasion as a viable cause of temporal heterogeneity in cliff retreat rate for both coastlines

spectral signatures for swash on reflective intermediate and dissipative beaches in this paper we synthesise a large data set gathered from a wide variety of field deployments and integrate it with previously published results to identify the spectral signatures of swash from contrasting beach types the field data set includes the full range of micro tidal beach types reflective intermediate and dissipative with beach gradients ranging from approximately 1 6 to 1 60 exposed to offshore significant wave heights of 0 5 3 0 m the ratio of swash energy in the short wave f 0 05 hz to long wave f 0 05 hz frequency bands is found to be significantly different between the three beach types swash energy at short wave frequencies is dominant on reflective and intermediate beaches and swash at long wave frequencies is dominant on dissipative beaches consistent with previously reported spectral signatures for the surf zone on these beach types the available swash spectra were classified using an automated algorithm clara into five different classes the ordered classes represent an evolution in the spectrum shape described by a frequency downshifting of the energy peak from the short wave into the long wave frequency band and an increase in the long wave swash energy level compared to a relatively minor variation in the short wave swash energy level a universally common feature of spectra from all beach states was an f 4energy roll off in the short wave frequency band in contrast to the broadly uniform appearance of the short wave frequency band the appearance of the long wave frequency band was highly variable across the beach states we incorporate the results presented here and previously published observations into the morphodynamic beach state model and propose an ordered sequence of swash spectra under increasing and decreasing incident wave energy level this extension of the beach state model to include the swash zone leads to the following propositions for morphodynamic controls on the nature of the swash spectrum 1 the short wave part of the swash spectrum is relatively constant in form across all beach states f 4 energy roll off and the energy density per unit frequency is controlled by the beach face gradient alone 2 the spectral bandwidth of the energy roll off varies directly with offshore wave energy level and inversely with beach face gradient or beach state in a manner consistent with the non linear wave breaking criterion 3 the infragravity part of the swash spectrum is highly variable in form across all beach states and the energy level is related to the offshore wave energy level and surf zone morphology

field observations of surf beat 1 progressive edge waves nineteen biaxial electromagnetic current meters have been used to determine the longshore and on offshore structure of currents at surf beat periods 1 4 min the sensors formed two linear arrays a long shore array within the surf zone and an on offshore array stretching from the shoreline to well beyond the breaker line analysis of the longshore current components yields a clear picture of progressive low mode edge waves with frequency wave number dispersion relations which are in remarkably good agreement with predictions some separation of edge wave modes is found with mode zero energy dominating in the frequency band 0 006 and 0 011 hz and mode one between 0 015 and 0 025 hz on offshore currents present a rather different picture which while not inconsistent with the longshore currents suggests that other sources of energy are also important to the on offshore currents these include standing edge waves probably formed by reflections at nearby scripps canyon and motions which are nonresonantly forced by incoming wave groups

obliquely incident irregular waves in surf and swash zones a time dependent numerical model is developed for predicting the free surface elevation and depth averaged cross shore and alongshore velocities in the swash and surf zones under obliquely incident irregular waves the assumption of small incident angles is made to simplify the finite amplitude shallow water equations and allow the computation of the cross shore fluid motion using the existing one dimensional model for normally incident waves the developed numerical model is compared with available field data the time dependent model is shown to be capable of predicting the cross shore variations of the root mean square wave height and longshore current in the surf zone the numerical model predicts large cross shore and alongshore velocities near the shoreline the causes of these large velocities are examined but cannot be ascertained for lack of velocity data near the shoreline

water level effects on breaking wave setup for pacific island fringing reefs the effects of water level variations on breaking wave setup over fringing reefs are assessed using field measurements obtained at three study sites in the republic of the marshall islands and the mariana islands in the western tropical pacific ocean at each site reef flat setup varies over the tidal range with weaker setup at high tide and stronger setup at low tide for a given incident wave height the observed water level dependence is interpreted in the context of radiation stress gradients specified by an idealized point break model generalized for nonnormally incident waves the tidally varying setup is due in part to depth limited wave heights on the reef flat as anticipated from previous reef studies but also to tidally dependent breaking on the reef face the tidal dependence of the breaking is interpreted in the context of the point break model in terms of a tidally varying wave height to water depth ratio at breaking implications for predictions of wave driven setup at reef fringed island shorelines are discussed

setup and swash on a natural beach wave setup and swash statistics were calculated from 154 runup time series measured on a moderately steep beach under incident waves varying from 0 4 to 4 0 m significant wave height when scaled by the incident wave height setup swash height and total runup the sum of setup and half the swash height were found to vary linearly with the surf zone similarity parameter 0 h0 l0 1 2 the foreshore slope appeared the appropriate value for the calculation of 0 although the setup data showed some influence of an offshore bar at low tide for low irribaren numbers the swash height in the incident frequency band becomes saturated while for high irribaren numbers no such signs of saturations were seen thus the infragravity band appears to become dominant in the swash below some value of 0 for these data that value is approximately 1 75 although there is considerable scatter associated with that estimate

wave runup during extreme storm conditions 1 video measurements of wave runup were collected during extreme storm conditions characterized by energetic long swells peak period of 16 4 s and offshore height up to 6 4 m impinging on steep foreshore beach slopes 0 05 0 08 these conditions induced highly dissipative and saturated conditions over the low sloping surf zone while the swash zone was associated with moderately reflective conditions iribarren parameters up to 0 87 our data support previous observations on highly dissipative beaches showing that runup elevation estimated from the variance of the energy spectrum can be scaled using offshore wave height alone the data is consistent with the hypothesis of runup saturation at low frequencies down to 0 035 hz and a hyperbolic tangent fit provides the best statistical predictor of runup elevations

bars bumps and holes models for the generation of complex beach topography in shallow water any two waves of the same frequency are shown to produce complex patterns of drift velocity above the sea bed if the longshore components hi h of the wave numbers of the two waves are different these steady flow patterns exhibit a longshore periodicity of wave number hi h irrespective of whether the waves propagate in the same direction say hi he positive or in opposite directions he negative the interaction of two edge wave modes is examined in detail the drift velocities are calculated and a simple sediment transport model is used to predict the beach topography that would be in equilibrium with these flow patterns as expected crescentic sand bars are produced by the special case of standing edge waves hi h intriguingly for all other cases a combination of complex transverse bars plus meandering or straight offshore bars result patterns that are surprisingly reminiscent of many published descriptions of complex rhythmic topography the extension of the model to three or more waves produces topography that appears to be very irregular although the pattern should repeat over sufficiently long distances along the beach even with only three waves these distances may be very large compared to the scale of the bars