mass flux and undertow in a surf zone abstract the mass of water carried shoreward by the breaking waves in a surf zone will in a two dimensional situation be compensated by a seaward return flow the undertow it is shown that the undertow is driven by the local difference between radiation stress and the set up pressure gradient which only balance each other in average over the depth turbulent shear stresses are required to maintain a steady situation comparison with measurements confirms the theoretical results

laboratory observation of boundary layer flow under spilling breakers in surf zone using particle image velocimetry abstract a boundary layer flow under spilling breakers in a laboratory surf zone with a smooth bottom is investigated using a high resolution particle image velocimetry piv technique by cross correlating the images oscillatory velocity profiles within a viscous boundary layer of o 1 mm in thickness are resolved over ten points using piv measurements taken for an earlier study and the present study flow properties in the wave bottom boundary layer wbbl over the laboratory surf zone are obtained including the mean velocities turbulence intensity reynolds stresses and intermittency of coherent events the data are then used to estimate the boundary layer thickness phase variation and bottom shear stress it is found that while the time averaged mass transport inside the wbbl is onshore in the outer surf zone it changes to offshore in the inner surf zone the zero eulerian mass transport occurs at h hb 0 92 in the outer surf zone the maximum overshoot of the streamwise velocity and boundary layer thickness are not constant across the surf zone the bottom shear stress is mainly contributed by the viscous stress through mean velocity gradient while the reynolds stress is small and negligible the turbulence level is higher in the inner surf zone than that in the outer surf zone although only a slight increase of turbulent intensity is observed inside the wbbl from the outer surf zone to the inner surf zone the variation of phase inside and outside the wbbl was examined through the spatial velocity distribution it is found the phase lead is not constant and its value is significantly smaller than previous thought by analyzing instantaneous velocity and vorticity fields a remarkable number of intermittent turbulent eddies are observed to penetrate into the wbbl in the inner surf zone the size of the observed large eddies is about 0 11 to 0 16 times the local water depth its energy spectra follow the 5 3 slope in the inertial subrange and decay exponentially in the dissipation subrange

large scale laboratory study of breaking wave hydrodynamics over a fixed bar a large scale wave flume experiment has been carried out involving a t 4 s regular wave with h 0 85 m wave height plunging over a fixed barred beach profile velocity profiles were measured at 12 locations along the breaker bar using lda and adv a strong undertow is generated reaching magnitudes of 0 8 m s on the shoreward side of the breaker bar a circulation pattern occurs between the breaking area and the inner surf zone time averaged turbulent kinetic energy tke is largest in the breaking area on the shoreward side of the bar where the plunging jet penetrates the water column at this location and on the bar crest tke generated at the water surface in the breaking process reaches the bottom boundary layer in the breaking area tke does not reduce to zero within a wave cycle which leads to a high level of residual turbulence and therefore lower temporal variation in tke compared to previous studies of breaking waves on plane beach slopes it is argued that this residual turbulence results from the breaker bar trough geometry which enables larger length scales and time scales of breaking generated vortices and which enhances turbulence production within the water column compared to plane beaches transport of tke is dominated by the undertow related flux whereas the wave related and turbulent fluxes are approximately an order of magnitude smaller turbulence production and dissipation are largest in the breaker zone and of similar magnitude but in the shoaling zone and inner surf zone production is negligible and dissipation dominates

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

pore water evolution during sediment burial from isotopic and mineral chemistry of calcite dolomite and siderite concretions abstract coal measures often contain concretions segregations of diagenetic minerals originally formed within unconsolidated sediments three different types calcite pyrite dolomite pyrite and siderite occurring spatially quite close together in the central pennine region of england vary widely in carbon isotope composition 10 35 13c 21 49 and in major cation chemistry ca mg fe mn within some siderite concretions very high mn fe ratios were found in central subsamples these were also most enriched in 13c the fe mg ratio decreases systematically from centre to edge early shallow to deeper later precipitation the calcite pyrite and dolomite pyrite concretions developed completely prior to significant burial both have high mn fe ratios but negative 13c values calcite 21 49 dolomite 8 67 to 10 48 all of these patterns can be equated precisely with theories of pore water evolution developed on the basis of geochemical investigations of modem sediments microbial processes sulphate reduction methanogenesis contributed significantly as did thermal decarboxylation to siderite precipitated at considerable burial depth mn iv and fe iii acted differentially as oxidants producing co2 and increasing alkalinity the interplay of fresh and marine depositional waters is seen most obviously in the presence or absence of sulphate reduction this controlled mineral type iron sulphide or carbonate as well as isotopic and mineral chemistry

experimental study on the hydrodynamics of regular breaking waves this paper illustrates the results of experimental research carried out in the wave flume of the water engineering and chemistry department laboratory of bari technical university italy and based on the analysis of three different regular waves breaking on a sloping bottom the investigation refers particularly to the surf zone with the aim to develop two themes the study of velocity and reynolds shear stress distributions in the shoaling zone of a regular wave field and the study of turbulence in the breaking region observing that these two aspects greatly influence many coastal processes such as undertow currents sediment transport and action on maritime structures

measurements of the vertical correlation in turbulence under broken waves abstract turbulence measurements have been carried out in the surf zone of a wave flume the purpose of the measurements is to determine the length scale of the turbulence generated by the wave breaking the length scale of the turbulence is estimated on basis of the correlation between simultaneous measurements of the vertical turbulent fluctuations taken at different levels above the bed

turbulence experiments in the swash zone abstract turbulence and water surface elevation measurements were carried out in the swash zone which was induced by plunging and collapsing breakers in a wave flume three different period regular waves were generated on a 1 10 smooth impermeable concrete beach and the water surface elevations were collected by a number of wave gauges and a run up meter lying on the bottom velocity measurements were carried out by a laser doppler velocimeter system at spatial steps of 1 mm from the bottom along three vertical sections in the swash zone the data have been used to describe the wave front dynamics to derive the length and velocity macro and micro scales and the eulerian frequency spectrum in some points it shows a double structure the results add to and expand on similar results obtained by other researchers in the surf zone

vertical distribution of wave shear stress in variable water depth theory and field observations 1 a generalized analytical model is developed to describe the vertical distribution of wave induced shear stress in the presence of bottom slope bottom friction and depth induced wave breaking in the shoaling region and surf zone the theory is compared to data obtained on an unbarred beach in 3 7 m mean water depth over a 2 bottom slope bottom slope and bottom friction are incorporated in the theory by including the wave energy dissipation by bottom friction in a potential wave theory for variable water depth and coupling the wave theory with a wave bottom boundary layer wbbl theory over a sloping bottom the effect of wave breaking is included through a periodic bore dissipation model previous studies have considered some but not all of these effects each of the three components sloping bottom bottom friction and wave breaking exhibits a different vertical structure the contributions due to bottom slope and bottom friction attain maximum strength in the wbbl and decay with distance above the bed approaching smaller but nonzero values at the surface in contrast the contribution from wave breaking is maximal at the surface and decays linearly with depth becoming zero at the bed the vertical structure of the cross shore u and vertical w components of wave orbital velocity was measured using a coherent doppler acoustic profiler the measured velocity fields were used to obtain the ensemble averaged wave shear stress profiles that extend across the wbbl to a height of 30 cm above the bed close to the seabed the observed and predicted uw profiles are similar confirming the sensitivity of wave stress to frictional and bottom slope effects within the wbbl farther from the bed however the observed profiles fall off more rapidly with height as w approaches quadrature with u faster than predicted wave breaking induced shear stresses were not observed

grain size dependent potential for self generation of magnetic anomalies on mars via thermoremanent magnetic acquisition and magnetic interaction of hematite and magnetite abstract early in the history of planetary evolution portions of martian crust became magnetized by dynamo generated magnetic field a lateral distribution of the secondary magnetic field generated by crustal remanent sources containing magnetic carriers of certain grain size and mineralogy is able to produce an ambient magnetic field of larger intensity than preexisting dynamo this ambient field is capable of magnetizing portions of deeper crust that cools through its blocking temperatures in an absence of dynamo we consider both magnetite fe3o4 and hematite fe2o3 as minerals contributing to the overall magnetization analysis of magnetization of magnetic minerals of various grain size and concentration reveals that magnetite grains less than 0 01 mm in size and hematite grains larger than 0 01 mm in size can become effective magnetic source capable of magnetizing magnetic minerals contained in surrounding volume preexisting crustal remanence for example 250 a m relates to 25 of multi domain hematite can trigger a self magnetizing process that can continue in the absence of magnetic dynamo and continue strengthening and or weakening magnetic anomalies on mars thickness of the primary magnetic layer and concentration of magnetic carriers allow specification of the temperature gradient required to trigger a self magnetization process

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

geology petrology and utilisation potential of some tertiary coals of the northeastern region of india abstract the coal bearing tertiary sediments of the northeastern region of india range in age from palaeocene to oligocene the coal deposits of meghalaya and the mikir and north cachar hills of assam contain generally thin seams of eocene age and were formed under stable shelf condition in peripheral platform areas the coal deposits of oligocene age occur in a narrow linear belt of overthrusts referred to as the belt of schuppen that extends from nagaland through assam to arunachal pradesh they were deposited in near shore deltaic wet forest swamps to marshy environments close to a geosynclinal trough the coal seams attain considerable thickness in the makum and namchik namphuk coalfields comparisons of coal type and rank variations in the eocene and oligocene coals indicate that the coals are broadly similar the coals are vitrinite rich 70 vol mineral matter free hereafter referred as mmf with moderate amounts of liptinite 8 vol mmf and inertinite 5 vol mmf the coals are high in volatile matter 38 57 dry mineral matter free basis hereafter referred as dmf sulphur 1 10 and hydrogen contents 4 9 dmf the carbon content of the coals ranges from 68 to 85 dmf the coals have caking properties in restricted zones the vitrinite reflectance of the oligocene coals r r 0 53 0 74 is slightly higher than that of the eocene coals r r 0 37 0 67 as per astm standard the eocene coals are classified as sub bituminous c to high volatile bituminous c and the oligocene coals as sub bituminous a to high volatile bituminous b microscopic examination of the coals shows a number of features which indicate that the northeastern coals may have generated hydrocarbons most of the eocene and oligocene coals are suitable for combustion and conversion e g liquefaction processes the coals with caking properties are being used at rates up to 5 10 in blends for metallurgical coke provided their sulphur content is below 3 and their ash content below 10

possible mineral sources of magnetic anomalies on mars at the end of the last millennium numerous ussr and u s spacecraft were sent to mars to begin exploration of that planet mars global surveyor 1997 onward is one of the successful missions that provided a detailed map of the topography and high resolution images of the surface and also discovered unusually large remanent magnetism of the crust up to 20 times larger than terrestrial standards

sedimentology palynostratigraphy and palynofacies of the late oligocene makum coalfield assam india a window on lowland tropical vegetation during the most recent episode of significant global warmth abstract the sedimentology palynofacies and pollen and spore assemblages together with observations on the preserved megaflora from the tirap coal mine assam india 27 17 20 n 95 46 15 e provide important insights into the composition and distribution of plant communities in a late oligocene tropical delta palaeolatitude approximately 18 n these insights take on additional significance because the late oligocene included the last significantly warm interval in earth s history before progressive neogene cooling to the present day icehouse the lower two thirds of a 188 m studied section represents lower delta plain environments with only a small degree of brackish water marine influence raised mires autochthonous swamps and allochthonous organic matter accumulations comprise the vitrinite rich high volatile bituminous b coals the upper third of the section represents upper delta plain environments with high sediment pass through here standing fossil forests attest to frequent inundation and recovery of the arborescent interfluve vegetation throughout the period of deposition of the studied section several 100 kyr sediment supply exceeded increases in accommodation space afforded by basin subsidence relative sea level rise a dominance of spores attributed to cyatheaceous and other fern taxa indicates that tree ferns and other pteridophytes were a major component of the vegetation throughout the environments represented by the section despite the absence of ferns in the megafossil record nypa and mangrove megaremains together with mangrove pollen and acrostichum spores attest to the presence of a mangrove community similar in composition to those of modern southeast asia palms and megathermal tree taxa such as those belonging to the malvaceae meliaceae alangiaceae anacardiaceae and pellicieraceae inhabited the interfluve and swamp forests perennial herbs of the family gunneraceae occur throughout the section palynofacies analysis shows a dominance of anoxic dysoxic environments with a small part of the lower part of the section exhibiting more oxic conditions associated with circumstantial evidence for mild marine possibly tidal influence most palynodebris fluoresce only weakly consistent with the relatively high rank for coals of this age a small number of reworked gondwanic permian grains suggest sediment erosion from the highlands to the north the late oligocene tropical delta vegetation has much in common with modern lowland wet megathermal forests from southeast asia however tree ferns appear more prevalent in the late oligocene

the funwave model application and its validation using laboratory data abstract in this paper the performance of a well known and widespread boussinesq model is evaluated for its ability to predict deep waters and shoaling zone velocity and elevation comparing them with laboratory data the model evaluation places emphasis on the parameters of the wave field that could be used for the prediction of coastal phenomena it was found that the model proved its ability to predict regular wave velocity and elevation both in deep waters and shoaling zones right up to the breaking region in contrast to previous works found in literature the comparisons in this case are not limited to modelled and measured wave elevations but also involve horizontal velocities as a result experimental and computed time series of wave elevations and horizontal velocities and their corresponding phase averaged values are investigated along the wave channel showing a good performance of the model also some considerations referring to measured and modelled turbulent velocities are illustrated

a particle image velocimetry investigation on laboratory surf zone breaking waves over a sloping beach particle image velocimetry piv measurements were performed in a wave tank under water waves propagating and breaking on a 1 15 sloping beach the wave transformation occurred in the surf zone over a large domain covering several wavelengths from incipient breaking to swash zone beyond the shoreline piv spatial interrogation windows must be small enough to obtain accurate velocities and one window covers only a small part of the domain to overcome this problem and to measure the instantaneous velocity field over the whole surf zone area we have split the full field into 14 overlapping smaller windows of the same size local measurements were synchronized with each other using pulsed ttl triggers and wave gauge data the full velocity field was then reconstructed at every time step by gathering the 14 piv fields we then measured the complete space time evolution of the velocity field over the whole surf zone we determined also the ensemble period average and phase average components of the flow with their associated fluctuating parts we used the piv images and velocity measurements to estimate the void fraction in each point of the surf zone special attention was given to the calculation of the spatial derivatives in order to obtain relevant information on vorticity and on the physical terms that appear in the fluctuating kinetic energy transport equation

palynological fluorescence in hinterland reconstruction of a cyclic shallowing up sequence pliocene papua new guinea abstract variations in fluorescence characteristics of contemporaneous and reworked palynological particles are documented through a cyclic shallowing upward sequence of lower pliocene mudstones of the orubadi formation in the puri anticline of the papuan foreland basin papua new guinea fluorescence of palynological particles may be affected by age oxidation and thermal maturation and therefore provides information about tectonic and palaeogeographical events in the source area of the particles the new guinea fold and thrust belt palynological particles have been identified with different fluorescence properties and sources 1 rocks at the southern proximal edge of the fold and thrust belt not greatly affected by tectonic events 2 rocks at a more distant location within the fold and thrust belt affected by tectonic controlled changes in gradient orographic rainfall and fluvial transportation and 3 contemporaneous vegetation affected by tectonic controlled changes in altitude and fluvial transportation variation in the fluorescence of palynological particles from these sources allows interpretations to be made about timing of thrusting events changes in the weathering and transportation regime and the variations in accommodation space in the foreland basin

evidence for weak ferromagnetic moment within the basal plane of hematite natural crystals at low temperature 1 low temperature magnetization of hematite within the basal plane has been studied in a collection of natural crystals by means of torque magnetometry comparison between the torque curves at room temperature and at 77 k allows identification of a weak ferromagnetic moment constrained within the basal plane at temperatures well below the morin transition annealing the samples produces the expected reduction of the weak ferromagnetic moment but there is also a relationship between the ferromagnetic moment before and after annealing low temperature measurements after the annealing experiment reveal the presence of a weak ferromagnetic moment that survives the annealing this observation suggests the magnetic structure of natural hematite crystals below the morin transition can still be a carrier of magnetization

analysis of surf zone turbulence measurements of turbulent kinetic energy k under surf zone waves are analyzed to show how k varies over depth between breaker point and shoreline and how k depends on the beach slope it is found that the variation of k over depth is remarkably weak large values being measured a few percent of the depth above the bottom a simple model for the dissipation mechanism makes it possible to derive an empirical formula for the time averaged k that accurately describes all the data considered reliable

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

turbulence in the swash and surf zones a review this paper reviews mainly conceptual models and experimental work in the field and in the laboratory dedicated during the last decades to studying turbulence of breaking waves and bores moving in very shallow water and in the swash zone the phenomena associated with vorticity and turbulence structures measured are summarised including the measurement techniques and the laboratory generation of breaking waves or of flow fields sharing several characteristics with breaking waves the effect of air entrapment during breaking is discussed the limits of the present knowledge especially in modelling a two or three phase system with air and sediment entrapped at high turbulence level and perspectives of future research are discussed

impact demagnetization of the martian crust primaries versus secondaries 1 numerical simulations presented here show that demagnetization of crust near the largest martian basins by secondary impacts can be comparable to that by direct shock waves outside the transient cavity the relative input from secondary impacts which demagnetize only the uppermost layers depends on the magnetic carrier distribution within the crust thus we discuss properties of likely magnetic remanence carriers and their possible spatial distribution within the crust

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

the early thermal and magnetic state of the cratered highlands of mars surface heat flows are calculated from elastic lithosphere thicknesses for the heavy cratered highlands of mars in terms of the fraction of the surface heat flow derived from crustal heat sources previous heat flow estimations for mars used linear thermal gradients which is equivalent to ignoring the existence of heat sources within the crust we compute surface heat flows following a methodology that relates effective thickness and curvature of an elastic plate with the strength envelope of the lithosphere and assuming crustal heat sources homogeneously distributed in a radioactive element rich layer 20 or 60 km thick the obtained results show that the surface heat flow increases with the proportion of heat sources within the crust and with the decrease of both radioactive element rich layer thickness and surface temperature also the results permit us to calculate representative temperatures for the crust base rock strength for the upper mantle and lower and upper limits to the crustal magnetization depth and intensity respectively for terra cimmeria an effective elastic thickness of 12 km implies between 30 and 80 of heat sources located within the crust in this case the uppermost mantle would be weak at the time of loading and temperatures in the lower crust cold enough to favor unrelaxed crustal thickness variations and to permit deep curie depths in the highlands as suggested by the observational evidence d 2005 elsevier b v all rights reserved

stable isotope composition of siderite as an indicator of the paleoenvironmental history of oil shale lakes the sediments of two eocene oil shale lakes messel graben and eckfeld maar west germany were analyzed with respect to the distribution chemical and stable isotope composition of siderite the data allow a reconstruction of different stages in the sedimentary and early diagenetic history of the lakes in the messel lake siderite formation started when the sedimentation of laminated sapropelic corg rich sediments was already established the early stage of oil shale sedimentation was characterized by pyrite precipitation in the siderite stage the stable isotope composition of the carbonate suggests methanogenesis to have been an important process at the sediment water boundary layer in the eckfeld lake siderite formation started even before sedimentation of the first sapropelic laminae the stable isotopic composition of the carbonate again indicates an anoxic sediment water boundary layer and strong methanogenesis with the expansion of this environment into the deep water mass sapropel sedimentation became established for both sequences the chemistry and stable isotope composition of the siderites correlates with petrographic and paleontological information about climate dependent fluctuations in the ecological chemical and early diagenetic environment the strong relationship of siderite formation to methanogenesis may be explained by the rate of microbial organic matter degradation which governed both methanogenesis and pco2

suspended sediment transport around a large scale laboratory breaker bar this paper presents novel insights into suspended sediment concentrations and fluxes under a large scale laboratory plunging wave measurements of sediment concentrations and velocities were taken at 12 locations around an evolving breaker bar covering the complete breaking region from shoaling to inner surf zone with particular high resolution near the bed using an acoustic concentration and velocity profiler wave breaking evidently affects sediment pick up rates which increase by an order of magnitude from shoaling to breaking zone time averaged reference concentrations correlate poorly with periodic and time averaged near bed velocities but correlate significantly with near bed time averaged turbulent kinetic energy the net depth integrated suspended transport is offshore directed and primarily attributed to current related fluxes undertow at outer flow elevations i e above the wave bottom boundary layer the wave related suspended transport is onshore directed and is generally confined to the wave bottom boundary layer cross shore gradients of sediment fluxes are quantified to explain spatial patterns of sediment pick up and deposition and of cross shore sediment advection suspended particles travel back and forth between the breaking and shoaling zones following the orbital motion leading to local intra wave concentration changes at locations between the breaker bar crest and bar trough intra wave concentration changes are due to a combination of horizontal advection and of vertical exchange with the bedload layer sediment is entrained in the bar trough during the wave trough phase almost instantly advected offshore and deposited near the bar crest during the wave crest phase finally these results are used to suggest improvements for suspended sediment transport models

contributions to the wave mean momentum balance in the surf zone abstract mean wave averaged cross shore flow in the surfzone has a strong vertical variation good understanding and prediction of this mean velocity profile is of crucial importance as it determines the advective transport of constituents such as sediment and consequently the coastal morphological evolution most modeling systems for coastal hydrodynamics and morphodynamics do no resolve the wave motion and wave current coupling is a challenging topic this paper investigates stresses and forces that control mean surfzone hydrodynamics based on detailed wave flume velocity measurements above a fixed sloping bed including two breaker bars the data show that the vertical distribution of normal stress below the wave trough level is fairly uniform at the same time the data suggest that a significant part is concentrated between the wave trough and crest level furthermore it is concluded that the horizontal radiation stress gradients and the vertical shear stress gradients can be of the same order of magnitude in the vicinity of the breaker bar although usually ignored in 3d mean flow modeling systems the wave reynolds stress makes an important contribution to the mean shear stress the normal stress below the wave trough level could be reasonably well predicted using the classical 16 expression accounting for the contribution between wave crest and trough the model of 39 reproduces the main trends in the wave reynolds stresses above the bottom boundary layer

large wave simulation of three dimensional cross shore and oblique spilling breaking on constant slope beach in this work the large wave simulation lws method is adapted for application in spilling wave breaking over a constant slope beach according to lws large scales of velocities pressure and free surface elevation are numerically resolved while the corresponding unresolved scale effects are taken into consideration by a subgrid scale sgs model for wave and eddy stresses the model may be not fully applicable in very shallow water close to the shoreline where the unresolved turbulent free surface oscillation is of the same order with the water depth time integration of the euler equations is achieved by a two stage fractional scheme combined with a hybrid scheme for spatial discretization consisting of finite difference and pseudospectral approximation methods model parameters are calibrated by comparison to available experimental data of free surface elevation and velocities in the surf zone for cross shore incoming waves the action of the wave sgs stresses in the outer coastal and surf zones initiates breaking and generates appropriate vorticity in the form of an eddy structure surface roller at the breaking wavefront at incipient breaking both advection and gravity contribute to the vorticity flux at the free surface while only after the full development of the surface roller the effect of advection becomes stronger the sgs model is also utilized to simulate propagation refraction and breaking of oblique incoming waves the gradual breaking and dissipation of wave crestlines and the surface roller structure along the breaking wavefront are automatically captured without any empirical input such as data for the roller shape or the wave propagation angle at breaking

observations of wave shear stress on a steep beach observations are presented of the wave shear stress u w on a steeply sloping beach above the wave boundary layer wbl positive values of u w were observed and are attributed to a combination of both wave shoaling due to the large scale bed slope and dissipation due to wave breaking in agreement with the wave theory of zou et al 2003 within the wbl observed vertical profiles of u w were also in good agreement with theory in cases where the wave height was small as wave heights increased however the wbl profile of u w generally did not agree with theory near simultaneous rotary sonar observations of the bed suggest the disagreement with theory was due to the presence of orbital scale ripples which the present theory does not accommodate