turbulent viscosity in natural surf zones 1 waves breaking in the shallow surf zone near the shoreline inject turbulence into the water column that may reach the bed to suspend sediment breaking wave turbulence in the surf zone is however poorly understood which is one of the reasons why many process based coastal evolution models predict coastal change during severe storms inadequately here we use data collected in two natural surf zones to derive a new parameterization for the stability functionc that determines the magnitude of the eddy viscosity tin two equation turbulent viscosity models t c k2 e where k is turbulent kinetic energy and e is the turbulence dissipation rate in both data sets the ratio of turbulence production to dissipation is small 0 15 while vertical turbulence diffusion is significant this differs from assumptions underlying existing c parameterizations which we show to severely overpredict observed c for most conditions additionally we rewrite our new c parameterization into a formulation that accurately reproduces our reynolds stress based estimates of turbulence production this formulation is linear with strain consistent with earlier theoritical work for large strain rates also it does not depend oneand can therefore also be applied in one equation turbulent viscosity models we anticipate our work to improve turbulence modeling in natural surf zones and to eventually lead to more reliable predictions of coastal evolution in response to severe storms

the south american rainfall dipole a complex network analysis of extreme events intraseasonal rainfall variability of the south american monsoon system is characterized by a pronounced dipole between southeastern south america and southeastern brazil here we analyze the dynamical properties of extreme rainfall events associated with this dipole by combining a nonlinear synchronization measure with complex networks we make the following main observations i our approach reveals the dominant synchronization pathways of extreme events for the two dipole phases ii while extreme rainfall synchronization in the tropics is directly driven by the trade winds and their deflection by the andes mountains extreme rainfall propagation in the subtropics is mainly dictated by frontal systems and iii the well known rainfall dipole is in fact only the most prominent mode of an oscillatory pattern that extends over the entir ec ontinent this provides further evidence that the influence of rossby waves which cause frontal systems over south america and impact large scale circulation patterns extends beyond the equator

vertical fluxes of sediment in oscillatory sheet flow time series of vertical sediment fluxes are derived from concentration time series in sheet flow under waves while the concentrations c z t vary very little with time for z 10d50 the measured vertical sediment fluxes qzs z t vary strongly with time in this vertical band and their time variation follows to some extent the variation of the grain roughness shields parameter 2 5 t thus sediment distribution models based on the pickup function boundary condition are in some qualitative agreement with the measurements however the pickup function models are only able to model the upward bursts of sediment during the accelerating phases of the flow they are so far unable to model the following strong downward sediment fluxes which are observed during the periods of flow deceleration classical pickup functions which essentially depend on the shields parameter are also incapable of modelling the secondary entrainment fluxes which sometimes occur at free stream velocity reversal the measured vertical fluxes indicate that the effective sediment settling velocity in the high 0 3 c z t 0 4 concentration area is typically only a few percent of the clear water settling velocity while the measurements of richardson and jeronimo chem eng sci 34 1979 1419 from a different physical setting lead to estimates of the order 20 the data does not support gradient diffusion as a model for sediment entrainment from the bed that is detailed modelling of the observed near bed fluxes would require diffusivities that go negative during periods of flow deceleration an observed general trend for concentration variability to increase with elevation close to the bed is also irreconcilable with diffusion models driven by a bottom boundary condition

a suspended sediment stratification correction for combined wave and current flows a simple model for the near bottom combined wave and current flow over a moveable sediment bed is presented the model is an extension of the grant and madsen 1979 combined wave and current model with moveable bed effects on the physical bottom roughness included as by grant and madsen 1982 the unsteady conservation of fluid momentum and sediment mass equations which are coupled through an eddy diffusivity closure scheme are solved for the wave and current velocity profiles along with the suspended sediment concentration and transport profiles sample runs are presented to illustrate the effect of varying wave conditions on the current the mean sediment concentration and the mean sediment transport results show that for fine to medium sands self stratification of the flow can be important during storms owing to the large amount of sediment suspended by the waves and the enhanced turbulent mixing associated with the wave current interaction the theory easily can be generalized for inclusion in a full ekman layer model

field observations of turbulence sand suspension and cross shore transport under spilling and plunging breakers measurements of wave orbital velocity near bed turbulence levels and sediment suspension were obtained under plunging and spilling breakers in the outer surf zone on the beach at vejers denmark for the same range of relative wave heights and indicators of wave nonlinearity we observed significantly larger suspended sediment concentrations and onshore directed rates of suspended sediment transport under long period plunging breakers compared to short period spilling breakers this is consistent with the long held understanding that for a given beach slope onshore transport and beach accretion are associated with longer period waves and offshore transport and erosion are associated with shorter period waves an intra wave analysis of hydrodynamics and sediment suspension revealed that the main reason for the larger suspended sediment transport rates under plunging waves was i larger time averaged suspended sediment loads under plunging waves and ii a larger difference in cumulated sediment load under the wave crest phase compared to the wave trough phase for plunging breakers this latter difference was due to an earlier arrival at the seabed of higher levels of turbulent kinetic energy under plunging waves compared to spilling waves hence both magnitude and timing within the wave cycle of turbulent kinetic energy production are important in a quantification of sediment transport under breaking waves for ensemble averaged intense suspension events contributing roughly 50 of the total sediment suspension during individual records we found that instantaneous near bed sediment load was linearly related to instantaneous levels of froude scaled turbulent kinetic energy

observation of undertow and turbulence in a laboratory surf zone abstract undertow and turbulence in the surf zone have been studied in a wave flume for a spilling breaker and a plunging breaker fluid velocities across a 1 on 35 sloped false bottom were measured using a fiber optic laser doppler anemometer and wave decay and set up were measured using a capacitance wave gage the characteristics of mean flow and turbulence in spilling versus plunging breakers were studied the mean flow is the organized wave induced flow defined as the phase average of the instantaneous velocity while the turbulence is taken as the deviations from the phase average it was found that under the plunging breaker turbulence levels are much higher and vertical variations of undertow and turbulence intensity are much smaller in comparison with the spilling breaker it was also found that turbulent kinetic energy is transported seaward under the spilling breaker and landward under the plunging breaker by the mean flow the study indicates that there are fundamental differences in the dynamics of turbulence between spilling and plunging breakers which can be related to the processes of wave breaking and turbulence production it is suggested that the types of beach profile produced by storm and swell waves may be the results of different relationships between mean flow and turbulence in these waves

modeling cross shore sandbar behavior on the timescale of weeks we compare predictions of a coupled wave averaged cross shore waves currents bathymetric evolution model to observations of onshore and offshore nearshore sandbar migration the observations span a 10 and 44 day period with onshore offshore bar migration at duck north carolina and at hasaki kashima coast japan respectively a 3 5 month period of onshore bar migration at duck and a 22 day period of offshore bar migration at egmond netherlands with best fit parameter values the modeled temporal evolution of the cross shore bed profiles agrees well with the observations model skill defined as 1 minus the ratio of prediction to no change error variances ranges from 0 50 at egmond to 0 88 for the prolonged onshore bar migration at duck localized in time and space reductions in model skill coincide with alongshore variations in the observed morphology consistent with earlier observations simulated offshore bar migration takes place during storms when large waves break on the bar and is due to the feedback between waves undertow suspended sediment transport and the sandbar simulated onshore bar migration is predicted for energetic weakly to nonbreaking conditions and is due to the feedback between near bed wave skewness bedload transport and the sandbar with negligible to small effects of bound infragravity waves and near bed streaming under small waves and conditions when breaking and nonbreaking conditions alternate with the tide the sandbar is predicted to remain stationary the intersite differences in the optimum parameter values are at least partly induced by insensitivity to parameter variations parameter interdependence and errors in the offshore wave forcing

grain boundary hierarchy development in a quartz mylonite abstract orientation contrast imaging using forescatter detectors and backscattered electron diffraction techniques in the scanning electron microscope have been used to investigate the boundary hierarchy characteristics of a quartz mylonite shear zone from torridon nw scotland the boundary hierarchy is defined as the relationship between the boundary misorientations their enclosed domain size and their frequency distribution by measuring the misorientation across every grain and subgrain boundary the characteristics of the boundary hierarchy can be found two microstructural domains were studied one partially recrystallized low strain domain with large relict grains and one fully recrystallized high strain mylonitic domain our results indicate that the processes of recovery subgrain rotation and grain boundary migration recrystallization each produce identifiable boundary hierarchy signatures in the relict quartz grains we have identified the processes of recovery and subgrain rotation in the recrystallized quartz a cyclic steady state exists between these and other processes coupling these data with traditional microstructural observations allows a more rigorous investigation into the development of a high strain fine grained mylonite from a coarse grained undeformed protolith we suggest that this type of detailed crystallographic microstructural analysis can greatly further our understanding of microstructural development in shear zones and may have implications for the effective use of sub grain size palaeopiezometers

breaker turbulence and sediment suspension in the surf zone field measurements of fluid velocities and suspended sediment concentrations were used to investigate the relative role of coherent vortices related to wave breaking in suspended sediment dynamics the measurements were obtained from a barred intermediate type beach and the instrument rig was exposed to a range of wave types during the experiment including shoaling waves and both spilling and plunging breakers the time scale of the observed breaker vortices was 5 hz and thus in the frequency range of wave orbital motion coherent breaker vortices were separated from wave orbital motions and incoherent higher frequency turbulence using a threshold magnitude for the vertical velocity component plunging breakers displayed the largest root mean square rms and maximum vertical velocities the latter reaching approximately 1 m s 1 these measurements were made at an elevation of 0 15 m above the bed given the observed scale of the breaker vortices and the phase match between suspended sediment concentrations and fluid velocities the turbulence injected into the water column by the plunging breakers played a significant role in suspending bed sediment on the other hand the role of coherent vortex structures in suspending sediment under spilling breakers and shoaling waves is more limited rms vertical velocities under the spilling breakers and shoaling waves in this experiment were respectively a factor 2 and 4 smaller than for plunging breakers different phase relationships were observed between the horizontal fluid velocity and vortex induced sediment suspension for each of the wave types which may contribute to an explanation of net offshore and onshore sediment transport observed during episodes of beach erosion and recovery respectively

identification of intense intermittent coherent motions under shoaling and breaking waves laboratory measurements of the instantaneous horizontal and vertical turbulent velocities u and w induced by regular waves spilling on a rough impermeable slope were analyzed to elucidate the nature of turbulence generated in the bottom boundary layer and by wave breaking the analyses focused on the instantaneous turbulent events such as the absolute shear stress u w and turbulent kinetic energy k u 2 w 2 2 below trough level inside the surf zone the horizontal and vertical velocity records showed intense intermittent turbulent events that did not occur with the passing of each wave and the instantaneous quantities of and k could not be explained in terms of the phase averaged quantities the intermittent turbulent events extended into the bottom boundary layer inside the surf zone and in this region the infrequent but intense turbulence generated by wave breaking was an order of magnitude larger than the turbulence generated locally at the boundary two techniques were used to analyze the turbulent motions a quadrant analysis technique showed that although the large turbulent motions did not occur with each wave they were phase dependent near trough level and less so near the bottom a conditional sampling technique quantified the intensity and duration of the turbulent motions indicating that coherent events intense events occurred for 10 2 of the record and accounted for approximately 50 20 of the turbulent motion it is likely that the exactitude of these statistics will differ depending on breaker type nevertheless these statistics indicated that large turbulent motions are infrequent but contribute significantly to the turbulence intensity and possibly the suspension of bottom sediments

an energetics total load sediment transport model for a plane sloping beach bagnold s energetics based total load sediment transport model for streams is used as a basis for the development of a total load model of time varying sediment transport over a plane sloping bed in both the bedload and suspended load the transport rate vectors are found to be composed of a velocity induced component directed parallel to the instantaneous velocity vector and a gravity induced component directed down slope the model is applied to idealized surfzone conditions leading to estimates of the local longshore and onshore offshore sediment transport rates as well as the equilibrium beach slope as a function of the local wave and current conditions the model is combined with a nonlinear longshore current model and spatially integrated to obtain predictions of the total longshore transport rate as a function of the incident wave conditions the results support the general form of the wave power equation except that the wave power coefficient is no longer constant but is instead a complex function of the incident wave and beach characteristics

nearshore sandbar migration predicted by an eddy diffusive boundary layer model 1 we simulated the erosion and accretion of a natural beach using a wave resolving eddy diffusive model of water and suspended sediment motion in the bottom boundary layer nonlinear advection was included in this one dimensional vertical profile model by assuming that waves propagated almost without change of form flows were forced by fluctuating pressure gradients chosen to reproduce the velocity time series measured during the duck94 field experiment the cross shore flux of suspended sediment beneath each field deployed current meter was estimated and beach erosion accretion was calculated from the divergence convergence of this flux horizontal pressure forces on sediment particles were neglected the model successfully predicted two bar migration events one shoreward bar migration and one seaward but failed to predict a third seaward migration event simulated seaward sediment transport was due to seaward mean currents simulated shoreward sediment transport was due to covariance between wave frequency fluctuations in velocity and sediment concentration and was mostly confined to the wave boundary layer predicted seaward shoreward bar migration was driven by a maximum in the current generated wave generated flux over the sandbar a wave generated downward flux of shoreward momentum into the wave boundary layer contributed to shoreward sediment transport and often had a local maximum over the bar crest second order nonlinear advection of sediment mostly representing shoreward advection by the stokes drift also often had a local maximum over the bar crest together wave generated momentum fluxes and the stokes drift substantially increased shoreward transport and were essential to predictions of shoreward bar migration

cross shore sediment transport on natural beaches and its relation to sandbar migration patterns 2 application of the field transport parameterization 1 a cross shore sediment transport parameterization shape function based on data from intensive field experiments carried out on five european beaches is incorporated into a simple time dependent model to explore its capability for reproducing sandbar generation and evolution in the medium term o months model results are compared with bar crest migration patterns observed at duck north carolina the model comprises a simple wave transformation routine that accounts for linear shoaling and assumes a saturation law for wave decay inside the surf zone second order statistics derived from the cross shore distribution of wave heights are used to scale the sediment transport parameterizations which estimate the cross shore structure of the third and fourth velocity moments cross shore gradients in sediment fluxes calculated with an energetics approach produce bed elevation changes the updated morphology affects the wave propagation in the next time step forming a fully coupled model for predicting sandbar evolution bar generation close to shore and the details of the sandbar evolution are successfully reproduced r2 0 86 over the 77 day period of the observations using default values for drag coefficients and efficiency factors in accordance with the observations the model shows rapid offshore sandbar migration in response to individual storms and weak onshore bar movement for lower energy conditions owing to its simple nature the model is not capable of reproducing the whole profile morphology especially in the trough no trough generation and it is only valid for replicating bar crest position the results suggest that a convergence of sediment near the breakpoint breakpoint hypothesis combined with morphological feedback can successfully explain the evolution of bar crest over periods of months from the details of forcing incident waves and water levels

laboratory observations of flow and sediment transport induced by plunging regular waves 1 two parallel experiments involving the evolution and runup induced by plunging regular waves near the shoreline of a sloping bed are considered 1 a rigid bed experiment allowing direct hot film measurements of bed shear stresses and 2 a sediment bed experiment allowing for the measurement of pore water pressures as well as observation of sediment suspension and bed morphological changes both experiments utilize the same initial bed profile and wave forcing the experiments show that the mean bed shear stresses experienced onshore of incipient breaking are amplified by nearly a factor of 2 relative to prebreaking conditions whereas their corresponding turbulent fluctuations are amplified even more strongly by a factor of 5 6 the plunging processes lead to a series of vortices whose formation may be explained as the result of shear layer instability measurements show that these vortices can significantly enhance peaks in the offshore directed bed shear stresses moreover near bed pore pressure measurements indicate that these vortices cause large upward directed pressure gradients which in turn produce a corresponding series of suspended sediment plumes shoreward of the initial breaking event these findings are related to the induced morphological changes over both short and long time scales the present results are also compared and contrasted with previous experiments utilizing a similar methodology but involving plunging solitary waves

observations of turbulence within the surf and swash zone of a field scale sandy laboratory beach abstract current coastal evolution models generally lack the ability to accurately predict bed level change in shallow

berm formation and dynamics on a gently sloping beach the effect of water level and swash overtopping berm formation and morphological development of the beach face have been observed during a neap neap tidal cycle on the gently sloping and accreting beach at vejers denmark during the field campaign an intertidal bar migrated onshore and stabilized as a berm on the foreshore a new intertidal bar occurred on the lower beach face migrated onshore on the rising tide and finally merged with the pre existing berm as the tide continued to rise the new berm translated further onshore as an intertidal bar to the uppermost part of the foreshore the sediment transport during the berm transition was onshore directed in the upper swash and offshore directed in the lower swash this berm development can be described through both the neap berm ridge and runnel and berm ridge development concepts proposed by hine sedimentology 1979 26 333 351 and all three stages were observed during only three tidal cycles the main factors controlling this fast transformation were the gentle slope of the cross shore profile rapid water level translation rates substantial swash overtopping of the berm and low infiltration rates despite the onshore migration of intertidal bars and berm formation no net foreshore accretion took place during the field campaign this was largely due to the formation of rip channels with strong rip currents cutting through the intertidal bars and the berm which acted as a sediment drain in the profile

wave bottom boundary layer processes below irregular surfzone breaking waves with light weight sheet flow particle transport the present work investigates the structure of the near bed flow below irregular surfzone breaking waves inducing light weight sheet flow particle transport the experiments are carried out in the legi flume under steady equilibrium conditions between the wave forcing and the underlying bed morphology synchronized acvp and video images provide detailed information about the mean wave and current characteristics and the coupled flow regimes across the entire wave breaking region including the outer and the inner surfzones an analysis of the impact of breaking eddies in the wave boundary layer wbl is undertaken at the beginning of the inner surfzone subsequently the intrawave variation of several contributions of the total shearing force per unit area and the net values of the reynolds stress related to phase averaged velocities are analyzed it is found that the wave component is the dominant term the turbulent reynolds stress the low frequency and the mean terms are at least 1 order of magnitude lower due to the irregular wave forcing the net values are separated into the net wave by wave reynolds stress and the wave reynolds stress averaged over the entire irregular wave sequence all these measured bed shear stress terms are then compared to estimations obtained with two different parameterized models in order to evaluate their prediction performances the values of the model parameters are discussed in comparison to those found in the literature finally the vertical profile of net reynolds shear stress exhibits a nearly constant value across the sheet flow layer

observations of turbulence within a natural surf zone abstract here the reynolds stresses u w and w where u and w are the cross shore alongshore and vertical turbulence velocities respectively and the angle brackets represent time averaging are used to diagnose turbulence dynamics beneath natural breaking surf zone waves the data were collected at truc vert beach france during a 12 day period in 1 3 m water depth with strong cross shore and alongshore currents under high energy wave conditions offshore significant wave heights ranged between 2 and 8 m the u w term is predominantly negative increases with the ratio of wave height hs to water depth h degree of wave breaking and decreases in magnitude toward the bed this supports the view that the cross shore shear stress is due to breaking induced vortices that transport high speed cross shore flow downward and disintegrate close to the bed the occasional positive sign of u w within the lower 15 20 of the water column indicates that sometimes surface generated turbule

detailed measurements of velocities and suspended sand concentrations over full scale ripples in regular oscillatory flow the knowledge and modeling of wave induced sand transport over rippled beds still has significant shortcomings which is partly related to a lack of measurements of the detailed processes from controlled laboratory experiments we have carried out new measurements of the detailed time dependent velocity and suspended sand concentration field around vortex ripples for regular oscillatory flow conditions the fact that the ripples were mobile and the flow conditions were full scale makes these measurements unique we made velocity measurements for 14 different flows and concentration measurements for three of these flows the velocity and concentration field above ripples are dominated by the generation and ejection of vortices on the ripple flanks around the time of flow reversal vortex formation results in near ripple flow reversals ahead of free stream reversals and velocity maxima near the ripple crest that are much higher than the free stream maxima asymmetry in the free stream produces steady circulation cells with dominant offshore mean flow up the ripple lee slope balanced by weaker onshore streaming up the ripple stoss slope as well as higher up in the flow the time and bed averaged horizontal velocity profile comprises an offshore streaming near the bed and an onshore drift higher up in the flow the vortices are responsible for three main concentration peaks one just after on offshore flow reversal associated with the passage of a sand laden vortex followed by two smaller peaks due to advected suspension clouds generated by vortex action at the neighboring onshore ripples the sand flux field measured for one typical asymmetric flow condition is dominated by an offshore flux associated with the suspended sand cloud generated by vortex shedding from the ripple s lee slope around the time of on offshore flow reversal the net time averaged current related and wave related horizontal sand fluxes are generally offshore directed and mostly contained within 1 5 ripple heights above the ripple crest the wave related suspended transport component is larger but the contribution of the current related suspended sand transport cannot be neglected in addition to the measured offshore net transport of suspended sand there is an onshore directed transport very close to the ripple surface the total net transport is in the offshore direction for this specific asymmetric flow condition

onshore sandbar migration in the surf zone new insights into the wave induced sediment transport mechanisms we present a novel process based morphodynamic model which includes transport processes due to both velocity and acceleration skewness and a new formulation for intrawave motions that successfully simulates observations of onshore sandbar migration results confirm findings of previous studies in which each process was considered separately and in which sediment transport was computed from the observed water motion however our results indicate that accounting for the joint action of both velocity and acceleration skewnesses causes major improvement of the modeled onshore bar migration and is essential to accurately model the evolution of the entire cross shore bottom profile when compared with observations we also demonstrate that the morphodynamics in the shoaling zone are dominated by velocity skewness bed shear stresses while sediment transport induced by acceleration skewness pressure gradients controls the morphodynamics in the inner surf zone

principal bed states during sandyduck97 occurrence spectral anisotropy and the bed state storm cycle 1 results are presented from 70 days of nearly continuous in situ acoustic imagery of the nearshore sandy seabed in 3 m mean water depth at two locations separated by 40 m cross shore distance the bottom sediments were 150 m median diameter sand with nearly identical size distributions at the two locations five principal bed states were observed irregular ripples cross ripples linear transition ripples lunate megaripples and flat bed the linear transition and flat bed states were the most frequent together accounting for 68 of the total time bed state occurrence was a strong function of incident wave energy each bed state occurring within a relatively narrow range of sea and swell energies during the 12 major storm events spanned by the record the bed response was characterized by a repeatable bed state storm cycle involving four of the five principal states lunate megaripples did not appear repeatedly and thus may be a special case with no obvious dependence of bed state occurrence on prior bed state or on third moment measures of wave nonlinearity radial spectra from the rotary acoustic images indicate pronounced differences in the anisotropy of spatial scales for the different bed states and exhibit onshore offshore differences which are likely related to ripple migration

onshore sediment transport on a sandy beach under varied wave conditions flow velocity skewness wave asymmetry or bed ventilation abstract measurements of the cross shore suspended sediment flux obtained from a planar and barred beachface have been used to investigate the propensity for wave driven onshore sediment transport during medium energy conditions three processes capable of transporting sediments onshore flow velocity skewness wave asymmetry and bed ventilation were investigated to determine their relative importance onshore directed flow accelerations under the steep front face of asymmetric waves were significantly correlated with sediment suspension whilst the effects of flow skewness and bed ventilation were discounted an acceleration modified form of the meyer peter type formula is used as initial attempt at modelling the onshore transport using a temporal filter to modify the bed shear stresses

sediment concentration and vertical mixing under breaking waves abstract field measurements of near bed sediment concentrations and sediment diffusivity in the breaker zone and in the inner surf zone of natural beaches were obtained using stacks of optical and fiber optical backscatter sensors under conditions with strongly plunging breakers as well as with spilling surf bores the field data suggest that significant differences exist between these wave types in terms of near bed sediment concentration levels and vertical mixing of sediment from the bed upward into the water column when plotting mean sediment concentration profiles in log c z space profiles are upward concave for spilling surf bores and sediment diffusivity increases approximately linearly upward from the bed for plunging waves however mean sediment concentration profiles are linear in a log c z plot indicating vertically constant sediment diffusivity this suggests that under surf bores sediment suspension from the bed occurs through diffusion processes while vertical mixing is mainly a convective process under plunging waves under surf bores sediment is largely confined to the lower layers of the water column while it is lifted to significantly higher elevations under plunging breakers

structure and modeling of surf zone turbulence due to wave breaking the turbulence structure under breaking waves in the surf zone is investigated through reference to experimental measurements and turbulence closure modeling this includes a unique set of recent turbulence measurements that have extended into the roller area through the application of digital particle image velocimetry measurements highlight the surface roller as the primary agent for turbulence production from where it is transported downward principally because of turbulent diffusion reflecting the breaker transition process turbulence intensities are largest some distance shoreward of the breaker point where the roller is fully developed the temporal variation of turbulence at a fixed point below the wave trough level is generally found to be minimal supporting the present use of a time independent turbulence closure model production of turbulent kinetic energy in the two equation k e model is presumed to occur in the vicinity of the surface roller from where it is transported downward through the water column by diffusion this production which is estimated from the rate of energy dissipation in the wave roller is the principal input parameter for the k e model froude scaled turbulence measurements from laboratory and field experiments are found to be satisfactorily predicted within the limits of the developed surf zone with improved methods of incorporating wave breaker transition zone effects leading to further model refinement the turbulence closure model is further shown to be effective in predicting time mean suspended sediment concentration and undertow velocity profiles in the surf zone