suspended sediment transport in the surf zone response to cross shore infragravity motion a field experiment to investigate the magnitude and temporal and spatial scales of suspended sediment transport in the inner surf zone was conducted at san marine oregon on october 7 13 1984 instrumentation consisted of five electromagnetic current meters three strain gauge type pressure transducers and 25 optical backscatter sensors to measure the concentrations of suspended sediment the instruments were deployed approximately 70 m x seaward of the mean high water line mean depth h 1 1 1 3 m in a closely spaced cross shaped pattern data were collected for 68 min periods spanning high tide during the 7 day experiment during the experiment waves varied in angle of approach from shore normal to southwesterly offshore significant swell heights were 3 5 m with periods of 12 14 s local sea conditions with wind waves of approximately 8 s also occurred a visual estimation of the width of the surf zone indicated it to be approximately 500 m and the breaker pattern suggested that there were two longshore bars at approximately 200 and 500 m offshore the data resulting from the experiment encompass a broad range of wave and current conditions which included periods of extreme infragravity motion 30 t 300 s and weak longshore currents and periods of low infragravity motion and strong longshore currents periods of incident wave dominance also occurred the field study section of this paper qualitatively describes the sediment response to strong 240 cm s 1 low frequency 0 01 hz cross shore fluid motions which dominated the inner surf zone during two of the data runs the infragravity band accounted for 85 of the cross shore velocity variance the peak 0 01 hz of which was associated with shore normal standing waves concentration gradients of suspended sediment appear to be associated with diffusive processes and develop and decay on time scales of the infragravity motions rather than those of incident waves suspension events during times of infragravity dominance often persisted for periods of 30 45 s and reached peak concentrations of 20 40 g l 1 at elevations in excess of 26 cm mean suspended load was 3 4 times larger than that associated with incident wave motions the modeling section of the paper attempts to quantitatively describe the observed time dependent vertical suspended sediment distribution with a one dimensional turbulent diffusion model formulations of eddy diffusion and erosion rate coefficients associated with peak cross shore flows are found to agree with or fall within the range of values from previous laboratory and field studies and are used in the model the model is evaluated by its ability to reproduce the time dependent vertical distribution of suspended sediment and to estimate the observed mean suspended load and the correct direction and magnitude of the mean longshore and cross shore flux level above the bed z 31 cm of suspended sediment

wave transformation and wave driven flow across a steep coral reef observations of waves setup and wave driven mean flows were made on a steep coral forereef and its associated lagoonal system on the north shore of moorea french polynesia despite the steep and complex geometry of the forereef and wave amplitudes that are nearly equal to the mean water depth linear wave theory showed very good agreement with data measurements across the reef illustrate the importance of including both wave transport owing tostokes drift as well as the eulerianmean transportwhen computing the fluxes over the reef finally the observed setup closely follows the theoretical relationship derived from classic radiation stress theory although the two parameters that appear in the model one reflecting wave breaking the other the effective depth over the reef crest must be chosen to match theory to data

numerical modeling of low frequency wave dynamics over a fringing coral reef abstract low frequency infragravity wave dynamics on a fringing coral reef were investigated using the numerical model xbeach roelvink et al 2009 first the skill of the model was evaluated in one and two dimensions based on its predictions of short waves 0 04 0 2 hz infragravity waves 0 004 0 04 hz and water level measurements tidal and wave setup obtained during a 2009 field study at ningaloo reef in western australia the model calibration was sensitive to friction coefficients for short waves and current infragravity bed friction which were assumed independent in this model study although the one dimensional cross shore model captured the gradients in the dominant hydrodynamic processes at the site a high current ig bed friction coefficient was required this resulted in an overestimation and a phase lag between the observed and predicted wave setup signal in the two dimensional model a lower more realistic current infragravity wave friction coefficient was required to achieve optimum performance due to the presence of significant reef and lagoon mean flows in the model which led to reduced setup across the reef the infragravity waves were found to propagate from the surf zone across the reef in a dominantly cross shore direction towards the shore but with substantial frictional damping the infragravity waves were strongly modulated also over the reef by tidal depth variations primarily due to the variability in frictional dissipation rates when the total water depth over the reef varied two mean wave driven circulation cells were observed in the study area with cross shore flow becoming more alongshore dominated before exiting the system via the two channels in the reef the results reveal that short waves dominated bottom stresses on the forereef and near the reef crest however inside the lagoon infragravity waves become increasingly dominant accounting up to 50 of the combined bottom stresses

forcing of resonant modes on a fringing reef during tropical storm man yi 1 open basin resonant modes have been observed at tidal frequencies on coastal shelves but their excitation on coral reef platforms has only been suggested the topography of and water depth over most fringing reefs correspond to resonant periods that are the order of tens of minutes and fall outside of the energetic part of the wave spectrum during tropical storm man yi low frequency near resonant oscillations dominated the variance of the sea surface elevation at the shoreline of ipan reef guam the excitation of the resonant modes resulted both from a large increase in water level over the reef due to wave setup which increased the resonant frequencies and the occurrence of wave group forcing with time scales commensurate with these increased resonant frequencies

distribution of chemical tracers in the eastern equatorial pacific during and after the 1982 1983 el nino southern oscillation event during april 1983 and march april 1984 two cruises were conducted in the central equatorial pacific to determine the effects of the el nino southern oscillation enso event on the sea air exchange of co2 measurements of total carbon dioxide pco2 total alkalinity freon 11 salinity temperature oxygen nutrients and wind and current velocities were made along three meridional transects 158 w april 1983 150 w march 1984 170 w april 1984 the cessation of upwelling during the enso event caused pco2 concentrations in surface waters to decrease to near saturation levels along the equator the calculated net flux of co2 across the sea air interface was essentially negligible in the eastern equatorial pacific during this period however when normal trade winds and consequent upwelling returned in late 1983 and early 1984 the equatorial region returned to a pco2 condition of highly supersaturated surface waters in the region between 8 n and 8 s along the 150 and 170 w transects the calculated post enso sea air flux of co2 exceeded 6 0 mmol co2 m 2d 1 the mean annual co2 flux in the equatorial pacific was estimated to be 0 02 gt of carbon during the 1982 1983 enso event as compared with 0 6 gt during 1984

wave transformation over coral reefs ocean wave attenuation on coral reefs is discussed using data obtained from a preliminary field experiment and from the seasat altimeter marked attenuation of the waves is observed the rate being consistent with existing theories of bottom friction and wave breaking decay in addition there is a significant broadening of the spectrum during propagation across reefs three dimensional effects such as refraction and defraction can also lead to substantial wave height reduction for significant distances adjacent to coral reefs as a result a matrix of such reefs provides significantly more wave attenuation than may initially be expected

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

infragravity response to variable wave forcing in the nearshore 1 analysis of field observations of sea surface elevation reveals the role of time varying incident forcing and bound wave release mechanisms on the generation of infragravity waves on a barred beach observations of infragravity response were obtained during sea breeze and swell periods with wave height varying from 0 2 to 1 2 m and wave period from 3 to 16 s the observations show a stronger infragravity response to longer period incident swell than to short period wind sea during the peak of the sea breeze short period wind sea is conducive to long wave generation by breakpoint forcing under swell dominated conditions the frequency and wave number of incoming bound waves associated with wave groups may satisfy the linear dispersion relationship leading to resonant forcing of a free wave that appears to be released from the wave group the transition between long wave generation due to bound wave release and time varying breakpoint forcing agrees with the surf beat similarity parameter

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

effects of wave rollers and bottom stress on wave setup 1 setup the increase in the mean water level associated with breaking waves observed between the shoreline and about 6 m water depth on an ocean beach is predicted well by a model that includes the effects of wave rollers and the bottom stress owing to the mean flow over the 90 day observational period the measured and modeled setups are correlated squared correlation above 0 59 and agree within about 30 although rollers may affect setup significantly on beaches with large amplitude several meters high sandbars and may be important in predicting the details of the cross shore profile of setup for the data discussed here rollers have only a small effect on the amount of setup conversely bottom stress calculated using eddy viscosity and undertow formulations based on the surface dissipation and assuming that the eddy viscosity is uniform throughout the water column significantly affects setup predictions neglecting bottom stress results in underprediction of the observed setup in all water depths with maximum underprediction near the shoreline where the observed setup is largest

fractional dispersion equation for sediment suspension this study proposes a stochastic approach to simulate sediment vertical dispersion in turbulent solid liquid flows by developing a fractional advection diffusion equation fade to characterize the dynamics of sediment suspension the fade is a generalization of the traditional advection diffusion equation ade where the first order spatial derivative is replaced with a fractional derivative of order alpha 0 alpha 1 many previous investigations of sediment suspension in steady sediment laden flows apply the classic or improved rouse equation which was derived from the traditional ade by assuming fick s first law for the sediment dispersive flux recent observations in field and laboratory studies however have indicated that large errors may arise from the traditional ade when applied to flows with coarse sediments instead the vertical dispersion of suspended sediment is most likely a space nonlocal transport process in flows with turbulent bursting because particle vertical jumps with ejection events are no longer constrained to a small distance defined by the representative elementary volume in other words the vertical random displacements of suspended particles follow levy motion instead of brownian motion after validating against field measurements in the las vegas wash as well as a set of published experimental data we find that the proposed fractional model can describe the real world vertical distribution of suspended sediment concentration in steady turbulent flows c 2013 elsevier b v all rights reserved

modulation of midtropospheric co2 by the south atlantic walker circulation abstractmidtropospheric co2 data from the atmospheric infrared sounder airs are used in this study to explore the variability of co2 over the south atlantic ocean it was found that the area averaged co2 over the south atlantic ocean is less than that over south america by about 1 ppm during december march this co2 contrast is due to the large scale vertical circulation over this region during december march there is sinking motion over the south atlantic ocean the sinking motion brings high altitude air with a slightly lower concentration of co2 to the midtroposphere meanwhile air rising over south america brings near surface air with a higher concentration of co2 to the midtroposphere as a result the airs midtropospheric co2 concentration is lower over the south atlantic ocean than over south america during december march the detrended airs midtropospheric co2 difference correlates well with the inverted and detrended 400 hpa vertical pressure velocity difference between the south atlantic an

episodic closure of the tidal inlet at the mouth of the russian river a small bar built estuary in california bar built estuaries with relatively small cross sectional area 100 m2 and shallow tidal inlets are widespread in mediterranean climates and along wave exposed coasts while similarly important to coastal sediment balances and estuarine ecosystems and more numerous than larger inlet systems they suffer from a relative lack of understanding this is especially true regarding the process of inlet closure when the channel is filled with sediment deposited by wave driven processes mouth closure is of growing concern owing to changes in inlet behavior in many systems in response to human influences the use of many existing conceptual and quantitative models for closure is precluded by rapid morphological change unsteady freshwater inputs and difficulties in scaling well established inlet relationships in these smaller systems in this paper over 60 years of daily closure records are analyzed for the russian river mouth a prototypical bar built system in northern california we show that the time dependent closure pattern can be explained by an interaction of processes that act to scour the inlet driven by tides and river with those that act to deposit sand in the inlet driven by waves tidal weather related seasonal and interannual cycles are observed we improve an existing parametric model to evaluate these separate influences and show that it works well for predicting closure events at both the tidal and seasonal scales finally we compare our data with closure records from the nineteenth and twentieth centuries to show that inlet closures have become shorter and more sporadic over time at this site and to identify anthropogenic drivers of this observed change

tide effects on wave attenuation and wave set up on a caribbean coral reef abstract the effects of tides on wave attenuation and wave set up were investigated at great pond bay a caribbean reef located in st croix u s virgin islands measurements of wave pressure fluctuations were made at three stations across the reef profile total wave set up was measured between the forereef and the reef crest or backreef lagoon wave spectra indicate significant filtering of energy at the peak frequencies as waves traveled across the reef the energy dissipation calculations imply an average energy reduction of 62 between the forereef and reef crest mean energy reduction between the forereef and lagoon was 90 energy dissipation between the forereef and reef crest increased 15 between high and low tide and 6 between forereef and lagoon tidal reduction of water depth at the reef crest intensified wave breaking and this condition increased energy dissipation measurements of wave set up ranged from 0 8 to 1 5 cm calculations of wave set up using tait s 1972 model showed good agreement with observations

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

wave setup a field study a new and efficient method is described for obtaining field measurements of surf zone mean water levels the method applies manometer tubes rather than the traditional pressure transducers and hence makes it unnecessary to survey the vertical positions of the sensors a substantial data base is obtained which apart from quantitative data for the field site and similar beaches gives clear general indications of where previous wave setup models need to be amended it is clear from the data that while traditional setup models work reasonably well seaward of the still water line the most landward part of the mean water surface on fairly steep beaches at least requires radically different models it is still possible however to obtain reasonable estimates of the shoreline setup by tying together the concepts of setup and runup and utilizing presently available empirical formulae for the maximum runup level

velocity and sediment concentration profiles in river flows an equation for the exponent in the power law velocity distribution is formulated by relating the rate of energy dissipation due to turbulent shear of the sediment bed layer to the increased rate of fluid shear energy dissipation produced by the moving sediment the suspended sediment concentration distribution corresponding to the power law velocity profile is calculated and simplified the relation derived for the power law exponent is found to be in good agreement with data from a large group of flume and river flows the powerlaw velocity profile and the corresponding concentration distribution are shown to be in excellent conformity with the distributions measured by vanoni and brooks

processes controlling morphodynamics of artificially breached barriers abstract naturally and artificially breached tidal inlets can promote fast morphological changes along the adjacent detrital barriers as they evolve in response to the contemporaneous wave regime inlet migration results in downdrift barrier erosion while updrift sand accumulation and concomitant barrier extension are commonly observed this study addresses the performance of placement of a sandfill designed to create an artificial dune along the updrift tip of a sand barrier aiming to constrain inlet migration stabilize its location and reduce sand transfers from the ocean into the lagoon induced by storm overtopping of the barrier herein we investigate the patterns of inlet drifting and processes regulating the progressive loss of efficiency of this soft engineering solution we show that besides updrift inlet migration which occurs with temporary reversal of the prevailing direction of drift currents meandering of the ebb channels that envelop the flood delta is quite effective in triggering or enhancing erosion of the updrift barrier tip in periods when the inlet main channel is migrating in the opposite direction this additional erosional process which acts along the back barrier facade is responsible for the increase of the erosion rate of the artificial dune and regardless of the direction of wave induced drift direction of the inlet this finding discloses the relevance of taking into account not only the oceanic processes waves but also processes operating on the lagoonal side of the barriers in future engineering operations designed for tidal inlet management

sediment suspension with rippled bed experiments on the suspension of sediment were performed in flume with and without sediment layer on the bottom for movable bed runs three dimensional sand ripples were found to affect seriously the features of suspended sediment the horseshoe vortices and the resulting bursts in the lee of the ripples entrain intermittently a large amount of sediment into the outer layer of flow details of the suspension process were studied using a sand ripple model made of plaster the result revealed that the vertical component of turbulent eddies is responsible for the suspension of sediment and the statistical distribution of the component was found to be the gaussian law the statistical distribution of the concentration fluctuation was observed to be highly skewed and the reason was determined to be the fact that the concentration increases with the power of eight against the vertical fluid velocity the period of the intermittent ejection of sediment agreed reasonably with those reported for natural geophysical flows thus the suspension of sediment in flows with rippled beds was proved to be significantly correlated with bursting phenomenon behind sand ripples

fortnightly tides in a lagoon with variable choking abstract modulation over the spring neap cycle of the frictional forces in a constricted choked channel connecting a lagoon to the open sea can induce a fortnightly period rise and fall of sea level in the lagoon a similar effect is also observed in the upper reaches of tidal rivers intuitively it might be expected that the fortnightly lagoon tide would be exactly in phase with the open sea spring neap cycle with maximum frictional set up of lagoon sea levels at springs a nonlinear model is used to demonstrate that this need not be the case however and that the fortnightly lagoon tide can lag the open sea spring neap cycle by up to 3 days the model is supported by observations from an artificial lagoon in north wales which is subject to two widely differing choking regimes as a result of the opening or closing of one inlet by a sluice gate

wave set up on coral reefs 2 set up on reefs with various profiles abstract all available laboratory data for wave set up on two dimensional reef profiles of various shapes have been compared with data from an idealised horizontal reef with a steep reef face gourlay 1996 the data is generally well represented by a relationship between the relative set up parameter gh r t o and the submergence parameter g h r h r h o and the relative set up on reef profiles of natural form is found to be less than that observed on the idealised horizontal reef the important influences of reef rim slope and variable water depths on the reef top have been investigated and some methods for allowing for them are suggested comparison of data for irregular waves with that for regular waves has led to the development of a simple method for estimating the effects of wave groups upon the magnitude of the steady state mean wave set up gh r the results of the analyses are applied to the determination of wave set up and its effects at three specific coral reef sites

wave setup over a pacific island fringing reef 1 measurements obtained across a shore attached fringing reef on the southeast coast of the island of guam are examined to determine the relationship between incident waves and wave driven setup during storm and nonstorm conditions wave setup on the reef flat correlates well r 0 95 and scales near the shore as approximately 35 of the incident root mean square wave height in 8 m water depth waves generated by tropical storm man yi result in a 1 3 m setup during the peak of the storm predictions based on traditional setup theory steady state inviscid cross shore momentum and depth limited wave breaking and an idealized model of localized wave breaking at the fore reef are in agreement with the observations the reef flat setup is used to estimate a similarity parameter at breaking that is in agreement with observations from a steeply sloping sandy beach a weak 10 increase in setup is observed across the reef flat during wave events the inclusion of bottom stress in the cross shore momentum balance may account for a portion of this signal but this assessment is inconclusive as the reef flat currents in some cases are in the wrong direction to account for the increase an independent check of fringing reef setup dynamics is carried out for measurements at the neighboring island of saipan with good agreement

suspended load transport of sediment mixtures careful experiments were conducted on alluvial beds of four sediment mixtures having different arithmetic mean diameters and standard deviations the suspended load transport rates of individual fractions were measured and compared with both einstein s and holtroff s methods of calculation of suspended load for individual fractions these methods were found to be unsatisfactory in the present range of sediment parameters a relationship is found to exist between the dimensionless shear stress and the suspended transport rate for uniform sediment to make this relation applicable to nonuniform sediments a corrective multiplying factor for shear stress is introduced the dimensionless parameters which govern this correction factor are identified and a relation for the same obtained in this manner the relation can be applied to individual size portions of a sediment mixture

wave generated flow on coral reefs an analysis for two dimensional horizontal reef tops with steep faces waves breaking on the seaward rim of a coral reef generate a flow of water from the exposed side of the reef to the sheltered side and or to either channels through the reef rim or lower sections of the latter this wave generated flow is driven by the water surface gradient resulting from the wave set up created by the breaking waves this paper reviews previous approaches to modelling wave generated flows across coral reefs and discusses the influence of reef morphology and roughness upon these flows laboratory measurements upon a two dimensional horizontal reef platform with a steep reef face provide the basis for extending a previous theoretical analysis for wave set up on a reef in the absence of a flow gourlay m r 1996b wave set up on coral reefs 2 set up on reefs with various profiles coastal engineering 28 1755 to include the interaction between a unidirectional flow and the wave set up the laboratory model results are then used to demonstrate that there are two basic reef top flow regimes reef top control and reef rim control using open channel flow theory analytical relationships are derived for the reef top current velocity in terms of the offreef wave conditions the reef top water depth and the physical characteristics of the reef top topography the wave set up and wave generated flow relationships are found to predict experimental values with reasonable accuracy in most cases the analytical relationships are used to investigate wave generated flows into a boat harbour channel on heron reef in the southern great barrier reef c 2005 elsevier b v all rights reserved

observations of infragravity waves infragravity wave periods of one half to a few minutes energy levels observed for about 1 year in 8 m water depth in the pacific and in 8 and 13 m depths in the atlantic are highly correlated with energy in the swell frequency band 7 to 20 s periods suggesting the infragravity waves were generated locally by the swell the amplification of infragravity wave energy between 13 and 8 m depth separated by 1 km in the cross shore is about 2 indicating that the observed infragravity motions are dominated by free waves not by group forced bound waves which in theory are amplified by an order of magnitude in energy between the two locations however bound waves are more important for the relatively few cases with very energetic swell when the observed amplification between 13 and 8 m depth of infragravity wave energy was sometimes 3 times greater than expected for free waves bispectra are consistent with increased coupling between infragravity waves and groups of swell and sea for high energy incident waves

wave driven flow over shallow reefs long term 1 month observations of waves and currents over a natural reef are presented which show a strong correlation between offshore rms incident wave height and cross reef currents at subtidal frequencies the energy spectrum of the cross reef currents shows a significant peak at twice the semidiurnal tidal frequency while the spectrum of sea surface elevation over the reef flat shows no corresponding peak furthermore experimental results reported by gourlay 1993 show setup over the reef occurs in the absence of a beach and the cross reef transport decreases with an increase in the sea surface slope across the reef flat due to an increase in setup at the top of the reef face analytic solutions for flow forced by wave breaking over an idealized reef explain the above features of cross reef flows in the absence of a beach through the surf zone on the reef face the cross reef gradient in the radiation stress due to wave breaking is partitioned between balancing an offshore pressure gradient associated with setup over the reef and forcing a mean flow across the reef over the reef flat where the depth is constant there is no forcing due to wave breaking and the flow is driven by a pressure gradient which results from the setup through the surf zone the magnitude of the setup through the surf zone is such that the transport across the reef flat matches the transport through the surf zone which is forced by the gradient in the radiation stress solutions are presented for general reef geometry defined by the reef width and slope of the seaward reef face and incident wave forcing defined by the depth at the breakpoint and the depth of water over the reef as the depth over the reef goes to zero the solutions converge to the plane beach solutions described by longuet higgins and stewart 1964 wave setup is maximized and the cross reef transport is zero in other cases the relative magnitudes of the setup and the cross reef transport depend on the geometry of the reef and the incident wave forcing

wave breaking hydrodynamics within coral reef systems and the effect of changing relative sea level this paper considers the hydrodynamics of wave driven flow across a coral reef and the resultant flushing of its lagoon current depth coefficients are introduced that describe the fractional change of across reef and lagoonal current with change in the relative local sea level i e the depth of water over the reef flat the coefficients are derived from an analytical hydrodynamic model and compared with data from two reefs the first is ningaloo reef in northwest australia which is a typical barrier reef with a narrow coastal lagoon and the second is kaneohe bay in oahu hawaii where the reef is both unusually deep and wide the current depth coefficients are shown to be sensitive to the form of the frictional law on the reef flat and can be deduced from measurements of the astronomical tidal currents in the lagoon both quadratic and linear friction laws are considered for the reef flat and good agreement obtained with a linear law based on the high frequency motion due to surface gravity waves

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

a hydrologic and geomorphic model of estuary breaching and closure abstract to better understand how the hydrology of bar built estuaries affects breaching and closing patterns a model is developed that incorporates an estuary hydrologic budget with a geomorphic model of the inlet system erosion of the inlet is caused by inlet flow whereas the only morphologic effect of waves is the deposition of sand into the inlet when calibrated the model is able to reproduce the initial seasonal breaching seasonal closure intermittent closures and breaches and the low streamflow closed state estuary hydrology of the carmel lagoon located in central california model performance was tested against three separate years of water level observations when open during these years the inlet was visually observed to drain directly across the beach berm in accordance with model assumptions the calibrated model predicts the observed 48 h estuary stage amplitude with root mean square errors of 0 45 m 0 39 m and 0 42 m for the three separate years for the calibrated model the probability that the estuary inlet is closed decreases exponentially with increasing inflow streamflow plus wave overtopping decreasing 10 fold in probability as mean daily inflow increases from 0 2 to 1 0 m 3 s seasonal patterns of inlet state reflect the seasonal pattern of streamflow though wave overtopping may become the main hydrologic flux during low streamflow conditions infrequently causing short lived breaches in a series of sensitivity analyses it is seen that the status of the inlet and storage of water are sensitive to factors that control the storage transmission and inflow of water by varying individual components of the berm system and estuary storage the amount of the time the estuary is open may increase by 57 or decrease by 44 compared to the amount of time the estuary is open during calibrated model conditions for the 18 2 year model period the individual components tested are berm height width length and hydraulic conductivity estuary hypsometry storage to stage relationship two factors that control wave swash sedimentation of the inlet and sea level rise the elevation of the berm determines the volume of water that must enter the estuary in order to breach and it modulates the wave overtopping flux and frequency by increasing estuary storage capacity the estuary will breach less frequently 27 change in time open for modeled excavation scenario and store water up to 3 months later into the summer altering beach aquifer hydraulic conductivity affects inlet state and patterns of breaching and water storage as a result of sea level rise of 1 67 m by 2100 and a beach berm that remains in its current location and accretes vertically the amount of time the estuary remains open may decrease by 44 such a change is an end member of likely scenarios given that the berm will translate landwards model results indicate that the amount of time the estuary is open is more sensitive to changes in wave run up than the amount of sand deposited in the inlet per each overtopping wave

episodic circulation and exchange in a wave driven coral reef and lagoon system we examined the role of wave driven circulation relative to wind and buoyancy forcing in a coral reef lagoon system circulation measurements in paopao bay moorea french polynesia during austral summer show the importance of waves in driving flows over the reef crest through the lagoon and out the reef pass tides were comparatively weak due to proximity to amphidromic points and exhibited an unusual spring neap cycle where the major lunar tide modulated the major solar tide and the overall tidal phase stayed approximately constant wind had only a secondary effect compared to surface waves a simple fluid mass balance indicated rapid flushing of the shallow back reef and export through the reef pass and a reef capture zone width of 2 3 km the reef pass circulation dynamics exhibited two layer baroclinic exchange flow when waves were small which was suppressed during large wave events the unusually weak tidal forcing provided an opportunity to more closely investigate wave driven circulation dynamics as expected theoretically there was a wave driven setup of the free surface across the shallow lagoon which drove a highly frictional flow evident by a large drag coefficient cp 0 1 diverging from extant theory the observed setup varied strongly with significant wave height and period overall the circulation and exchange between this coral reef system and the adjacent open ocean were largely determined by episodic remote forcing events and differed significantly from periodic tidal exchange mechanisms

a sediment record of barrier estuary behaviour at the mesoscale interpreting high resolution particle size analysis abstract at present limited understanding of mesoscale years decades centuries back barrier lagoon barrier estuary behaviour is a critical shortcoming for resource managers and decision makers in this paper high resolution particle size analysis of a sediment core from an intermittently open and closed barrier estuary is utilised to reconstruct a history of back barrier environmental change at mesoscale temporal resolution sediments from pescadero marsh california were analysed for their particle size distribution at consecutive 2 mm intervals down core site selection informed by a time series of maps and aerial photographs coupled with a robust core chronology ensured that the particle size data primarily reflect changing hydrodynamics of the back barrier area over the european american era 1850 to the present following more traditional plotting of particle size data and summary statistics and statistical analysis of particle size end members visual analysis and categorisation of particle size distribution curves psdcs provide an effective basis for the identification of recurring modal sizes and subpopulations these particle size windows psws are interpreted as reflecting different modes of sediment transport and deposition i e suspension and saltation loads the varying prominence of which is interpreted as being modified by barrier integrity when considered together the down core mean particle size mps trend and individual psdcs offer considerable insight into mesoscale system behaviour at subannual resolution over multiple years this behaviour is expressed in the recurrence of characteristic barrier estuarine environments closed lagoon tidal lagoon tidal marsh and open estuary and the overall barrier regime and their persistence over the last c 150 years subannual and multiannual fluctuations in back barrier environmental configuration are seen to be superimposed on a longer term quasi stable barrier regime demonstrating the value of the applied methodology with regard to bridging the estuarine evolution long term stratigraphic and process short term geomorphic knowledge bases the documented behaviour suggests a level of innate morphological resilience in the system over the long term despite episodic disturbance by high energy storms such empirical demonstrations of resilient behaviour in coastal environments are rare at the mesoscale

atlantic climate variability and its associated atmospheric circulation cells abstract phenomena important for atlantic climate variability include the atlantic zonal equatorial mode the tropical atlantic meridional gradient mode and the north atlantic oscillation nao these climate phenomena and their associated atmospheric circulation cells are described and discussed using the ncep ncar reanalysis field and the ncep sea surface temperature sst from january 1950 to december 1999 atmospheric divergent wind and vertical motion are used for the identification of atmospheric circulation cells during the peak phase of the atlantic equatorial mode the atlantic walker circulation weakens and extends eastward which results in surface westerly wind anomalies in the equatorial western atlantic these westerly wind anomalies are partly responsible for warming in the equatorial eastern atlantic that occurs in the second half of the year the atlantic equatorial mode involves a positive ocean atmosphere feedback associated with the atlantic walker circulation similar to the pacific

wave set up on coral reefs 1 set up and wave generated flow on an idealised two dimensional horizontal reef wave set up may be significant in determining water levels on coral reefs particularly in microtidal environments and hence is an important factor for the design of reef top structures and for the stability of reef top islands laboratory experiments have been made on a two dimensional model of an idealised horizontal reef under two different conditions corresponding to a fringing reef or closed lagoon situation and a platform reef or open lagoon situation both wave set up on the reef top and the wave generated flow across the reef were measured and related to wave and tide level conditions all other factors being the same wave set up is greatest at low tide levels whereas wave generated flow is greater at higher tide levels the magnitude of the set up on a platform reef with a wave generated flow is less than on a fringing reef without any net flow by an amount equal to the velocity head of the flow across the reef dimensionless parameters ghrt o and q gho3 are found to be functions of relative submergence parameters hrho or r hr ho for values of ghr hr ho 1 waves break on the reef top and radiation stress theory can be used to calculate set up for ghr hr ho 0 7 waves break on the reef face and set up is determined by broadcrested weir control at the reef edge the symbols are defined as follows g is gravitational acceleration hr is still water depth over horizontal reef top ho is offreef wave height equivalent deep water value q is discharge per unit length of reef edge t is wave period and ghr is maximum wave set up on reef top

hydrodynamics at a microtidal inlet analysis of propagation of the main wave components abstract the evolution of different wave components as they propagate within a microtidal inlet during a storm occurring from 24 26 january 2014 is analysed in order to improve knowledge on how microtidal river mouths typical of the adriatic sea behave for the first time the low pass filter mechanism previously ascertained at several macrotidal oceanic inlets around the world has been observed in the field with remarkably specific hydrodynamic conditions i e low tide excursion permanent connection with the sea and generally milder wave climate than in the ocean sea swell ss waves were strongly dissipated before entering the river mouth through the combined action of wave breaking due to reducing depths and opposing river currents enhanced by rainfall infragravity ig waves propagated upstream and significant ig wave heights of up to 0 4 m about 13 of the local water depth have been observed 400 m upriver about 10 times the local ss peak wavelength during storm climax the ig wave energy here represented over 4 of the maximum offshore storm energy ig wave components travelled upriver at estimated velocities between 3 6 m s and 5 5 m s comparable with speeds of nonlinear long waves during intense storm stages up to 600 m into the river channel about 15 times the local ss peak wavelength and are enhanced by tide induced increase in water depths it is estimated that tide induced excursion accounted for about 80 of the total mean water elevation at storm peak at about 400 m into the river finally tidal oscillations are detected up to 1 5 km upstream about 40 times the local ss peak wavelength this study highlights the dominance of astronomical tide over both wave setup and storm surge in controlling the upriver propagation of ig waves even in a microtidal environment

wave current interactions in a wave dominated tidal inlet 1 wave current interactions play a major role in the dynamics of shallow tidal inlets this study investigates these interactions at a natural inlet with a strong focus on current induced changes on wave propagation the analysis of hydrodynamic data collected at the albufeira lagoon portugal revealed spatiotemporal variations of water levels and wave heights along the inlet attributed to wave current interaction processes we compared the simulations of a coupled wave circulation modeling system computed with and without waves and propagated with and without current feedback the wave induced setup inside the lagoon represented 7 15 of the offshore significant wave height the accuracy of the wave s predictions improved when current feedback was included during ebb the currents increased the wave height at the mouth of the inlet up to 20 and decreased the wave height in the inlet up to 40 due to current induced refraction steepness dissipation and partial blocking during flood the currents decreased the wave height in the inlet up to 10 and increased the wave height at the exterior parts of the ebb shoal up to 10 due to current induced refraction these effects significantly attenuate seaward sediment fluxes during ebb and contribute to the sediment accretion in the inlet

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

infragravity currents in a small ria estuary amplified coastal edge waves abstract observations are presented of estuarine infragravity oscillations in a very small estuary the ria de santiuste northern spain that discharges into a bay time scale calculations and measurements indicate that the most likely source of amplified infragravity waves within the estuary are coastal edge waves which appear to be resonating between the headlands of the bay and onshore offshore seiching of waters that may be resonating between the beach and the bay s seaward limit infragravity waves in the estuary have a narrow power dominant periodicity range of 4 3 4 8 min generally only very weak waves and at other periodicities occur within the tidal river when it is unaffected by the tide although infragravity water level amplitudes are small in the tidal river typically 0 01 m during high water the corresponding velocity amplitudes are significant typically 0 1 m s 1 despite the occurrence of high runoff conditions during these measurements within the estuary and close to the mouth near bed salinity shows considerable variability that is a consequence of salt wedge oscillations with periodicities that are within the range of 4 3 4 8 min model results for simulated neap to spring high water water levels show that wave periodicities in the range 3 5 4 5 min correspond approximately to 3 4 resonances the model also indicates that an effect of low runoff is to greatly enhance resonant behaviour within the estuary such that water level amplitudes of 0 02 m at the mouth can produce wave currents as fast as 0 4 m s 1 within the estuary compared with 0 1 m s 1 during high runoff

modeling mixed sediment suspended load profiles potential errors in calculated vertical suspended sediment concentration profiles in river flows carrying mixed sediments are investigated these profiles are usually obtained through application of a standard diffusion dispersion model however such models are normally formulated on the basis of a unique grain size for the sediment accordingly in the case of sediment mixtures the grain size distribution is usually divided into several size ranges fractions which are then characterized by their respective geometric means numerical errors induced through this procedure are quantified in a parametric study while depthaveraged concentrations can be over esimated by a factor of 1 2 when the concentration gradient is weak they can be under estimated by a factor of 15 when the gradient is large estimates are found to be particularly sensitive when the chosen reference level is small and the fraction width is large fall velocity coefficients are introduced to correct the discrepancy between the a

undular tidal bore dynamics in the daly estuary northern australia measurements in the macro tidal daly estuary show that the presence of an undular tidal bore contributed negligibly to the dissipation of tidal energy no recirculation bubble was observed between a trough and the following wave crest in the lee waves following the undular bore this differs to stationary undular bores in laboratory experiments at larger froude numbers where a recirculation bubble exists secondary motions and the turbulence generated by the undular bore had no measurable influence on the sediment transport this situation contrasts with the intense sediment resuspension observed in breaking tidal bores the tidally averaged sediment budget in the daly estuary was controlled by the asymmetry of tidal currents the undular bore may widen the river by breaking along the banks that it undercuts leading to bank slippage a patch of river wide macro turbulence of 3 min duration occurred about 20 min after the passage of the bore during accelerating tidal currents

processes driving estuary infilling by marine sands on an embayed coast abstract detailed measurements of waves currents and sediment transport from an intertidal sandflat at the mouth of a partially filled new zealand estuary in an embayment with low littoral drift are presented with a view to establishing how marine sands are transported into the estuary waves mobilised sediments during episodic events early in events when waves were energetic sediments were in motion throughout the tidal cycle under abating waves sediment motion became intermittent finally becoming restricted to periods around low tide when wave orbital motions were able to penetrate to the bed three components of the total sediment flux were estimated from the data and analysed 1 a wind driven current which presumably has a complicated spatial expression in the vicinity of the estuary mouth controlled the net i e integrated over event direction of flux of suspended sediment entrained by waves and advected by currents there was no evidence of non symmetry over the tidal cycle in the suspension process that might drive a net sediment flux however there is some suggestion that lag in growth and decay of the estuary wave field over the tidal cycle systematically enhances offshore transport 2 net bedload transport by waves and currents was directed onshore which was guaranteed by two mechanisms firstly increasing wave orbital current skewness as the tide ebbed turned bedload transport onshore late in the ebb tide against the current and secondly bedload peaked early in the flood tide when skewed waves were reinforced by the flooding current 3 correlation between seaward directed forced mean flow and enhanced suspension under groups of high waves resulted in persistent offshore flux of suspended sediment at infragravity frequencies suspended sediment flux carried by gravity waves was directed seawards on flood tides and counter to the waves and onshore on ebb tides and with the waves which was explained in terms of a simple vortex ejection model we conclude that sediment transport on the sandflat at the mouth of this partially filled estuary is governed by subtle interactions between waves and currents that vary over the tidal cycle some interactions such as those that drive bedload transport promote estuary infilling by marine sands and others such as those that drive suspended sediment flux at infragravity frequencies do the opposite

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

tidally discontinuous ocean forcing in bar built estuaries the interaction of tides infragravity motions and frictional control shallow bar built estuaries on wave dominated coasts in mediterranean climates experience an intermittent connection to the ocean in the presence of low streamflow their inlets may completely close as a result of nearshore sand transport but even in the open condition these inlets remain constricted extensive field measurements in the highly salt stratified pescadero estuary in northern california show that the shallow mouth causes these estuaries to experience discontinuous tidal forcing while the ocean and estuary are fully connected with near equal water levels tidal velocities are slow but infragravity motions in the nearshore induce large velocity oscillations within the estuary as the ocean tide falls infragravity forcing is cut off because the estuarine mouth is perched above the low tide ocean water level and ebbing velocities are set by bed friction observations reveal this oscillation between ocean forced and frictionally controlled conditions characterizes and sets estuarine hydrodynamics additional wave setup of the lagoon emphasizes the dependence of these estuaries on nearshore ocean conditions but the diurnal or semidiurnal retreat of the ocean below the mouth cuts off this nearshore influence so it too is tidally varying here we present detailed observations and a framework for understanding hydrodynamics in small shallow bar built estuaries