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

a lagrangian model for boundary layer growth and bed shear stress in the swash zone abstract a new model for the boundary layer development and associated skin friction coefficients and shear stress within the swash zone is presented the model is developed within a lagrangian reference frame following fluid trajectories and can be applied to both laminar flow and smooth turbulent flow the model is based on the momentum integral approach for steady flat plate boundary layers with appropriate modifications to account for the unsteady flow regime and flow history the model results are consistent with previous measurements of bed shear stress and skin friction coefficients within the swash zone these indicate strong temporal and spatial variation throughout the swash cycle and a clear distinction between the uprush and backwash phase this variation has been previously attributed the unsteady flow regime and flow history effects both of which are accounted for in the new model fluid particle trajectories and velocity are computed using the non linear shallow water wave equations and the boundary layer growth across the entire swash zone is estimated predictions of the bed shear stress and skin friction coefficients agree reasonably well with direct bed shear stress measurements reported by barnes et al barnes m p o donaghue t alsina j m baldock t e 2009 direct bed shear stress measurements in bore driven swash coastal engineering 56 8 853 867 and for a given flow velocity give stresses which are consistent with the bias toward uprush sediment transport which has consistently been observed in measurements the data and modelling suggest that the backwash boundary layer is initially laminar which results in the late development of significant bed shear during the backwash with a transition to a turbulent boundary layer later in the backwash a new conceptual model for the boundary layer structure at the leading edge of the swash is proposed which accounts for both the no slip condition at the bed and the moving wet dry interface however further development of the lagrangian boundary layer model is required in order to include bore generated turbulence and to account for variable roughness and mobile beds

sedimentology stratigraphy and paleoclimate at the late miocene coffee ranch fossil site in the texas panhandle abstract the late miocene coffee ranch fossil assemblage contains some of the earliest evidence of c4 herbivory in north america however little is known regarding the environmental setting associated with the fauna and a general lack of detailed paleoclimate data exists for the late miocene from the north american continental interior in this study the sedimentary environments stratigraphy geochronology and paleoclimate are interpreted for a series of outcrops of the late miocene ogallala formation in the texas panhandle that includes the coffee ranch locality updated magnetostratigraphy coupled with previously published geochronology indicates that all exposed strata were deposited over a 277 kyr interval within chron c3an 2n from 6 42 6 70 ma depositional environments include fluvial channels floodplain ponds floodplain paleosols eolian paleosols riverine tufa and reworked volcanic ash trunk and tributary fluvial channels are differentiated using channel dimensions sedimentary structures and bounding surface architecture and indicate seasonally variable discharge paleosols from nine pedofacies are described and preserve a spectrum of weakly developed entisols and weakly to moderately mature inceptisols and vertisols constitutive mass balance calculations reveal that mature paleosols formed along distinct pedogenic pathways calcic vertisols accumulated pedogenic carbonate and exhibited either net volumetric dilation or collapse as a result of mineral weathering in contrast non calcic vertisols show patterns of decalcification and variable degrees of volumetric dilation and collapse the presence of the paleosols described in this study requires paleoprecipitation between of 900 1150 mm yr approximately double modern values and a westward shift of the continental udic ustic soil moisture boundary by 400 km during the late miocene this finding suggests that climates in the southern midcontinent were not sufficiently arid to select for c4 photosynthetic pathways over c3 photosynthesis in the late miocene

linking hydrological infinite slope stability and land use change models through gis for assessing the impact of deforestation on slope stability in high andean watersheds in the ecuadorian andes episodic slope movements comprising shallow rotational and translational slides and rapid flows of debris and soil material are common consequently not only considerable financial costs are experienced but also major ecological and environmental problems arise in a larger geographical area sediment production by slope movement on hillslopes directly affects sediment transport and deposition in downstream rivers and dams and morphological changes in the stream channels in developing countries world wide slope movement hazards are growing increasing population pressure and economic development force more people to move to potentially hazardous areas which are less suitable for agriculture and rangelands this paper describes the methods used to determine the controlling factors of slope failure and to build upon the results of the statistical analysis a process based slope stability model which includes a dynamic soil wetness index using a simple subsurface flow model the model provides a time varying estimate of slope movement susceptibility by linking land use data with spatially varying hydrologic soil conductivity evapotranspiration soil wetness and soil strength properties the slope stability model was applied to a high andean watershed gordeleg catchment 250 ha southern ecuadorian andes and was validated by calculating the association coefficients between the slope movement susceptibility map of 2000 and the spatial pattern of active slope movements as measured in the field with gps the proposed methodology allows assessment of the effects of past and future land use change on slope stability a realistic deforestation scenario was presented past land use change includes a gradual fragmentation and clear cut of the secondary forests as observed over the last four decades 1963 2000 future land use change is simulated based on a binary logistic deforestation model whereby it was assumed that future land use change would continue at the same rate and style as over the last 37 years 1963 2000 c 2002 elsevier science b v all rights reserved

establishing rates of karst landscape evolution in the tropics a context for the formation of archaeological sites in western flores indonesia tropical landscapes evolve at a rapid rate creating stepped alluvial terraces dense basin and cone topographies and multilevel cave systems an understanding of the rate of landscape evolution is crucial for understanding how landscapes respond to tectonic instability and for reconstructing landscapes that have changed over archaeological timescales the rate of landscape incision as a proxy for karst landscape evolution in indonesia a key region in the path of human dispersal has been established using the rate of karstification by estimating a chronology for stages of cave development using thermal ionisation mass spectrometry u series dating on flowstones and the rate of downcutting by establishing a chronology for a series of alluvial terraces using red thermoluminescence dating using these techniques we have determined that the estimated rate of karstification 113 26 mm ka 1 is slower than the average rate of downcutting 305 24 mm k 1 and the combined rate of landscape incision 217 18 mm ka 1 is slower than the known rate of tectonic uplift for this region derived from raised coral terraces 450 50 mm ka 1 this suggests that rivers are quicker to respond to tectonic instability but both cave and river systems display a slower rate of incision and karstification than uplift correlations between these components of the landscape system reveal a strong interacting relationship where defined phases of uplift are reflected in the pattern of karstification and cycles of downcutting an understanding of this relationship has been pivotal in reconstructing the formation and geomorphic history of archaeological caves such as liang bua copyright c 2010 john wiley sons ltd

differing responses to extreme rainfall events in headwater areas recorded by wood anatomy in roots gorce mountains poland abstract local short lasting downpour is typically observed more frequently in headwater areas than in overall catchments headwater systems act as buffers and serve as starting points for stream channels therefore recognition of the magnitude and frequency of their transformation is important for the understanding of the functioning of entire mountain catchments despite numerous studies on extreme events the headwater areas are still poorly recognised there are a number of steep forest covered headwater areas in the gorce mountains a range of flysch type mountains that form part of the polish carpathians which have not yet been studied in relation to this issue therefore the main aim of this study was to determine the nature of geomorphic activity acting within different parts of the headwater areas in order to date extreme geomorphic events precisely a dendrogeomorphic approach was performed based on anatomical changes in exposed roots a total of 59 spruce picea abies l karst roots were sampled besides the reduction in tracheid lumen area in earlywood that is traditionally used a recently developed approach using an abrupt change in the amount of latewood as an indication of the moment when geomorphic activity takes place was also taken into consideration data from exposed roots were compared to rainfall data the results showed that the headwater areas experienced a variety of geomorphic processes the timing of processes was assessed for the years 1944 to 2001 the main difference between the roots can be observed between the upper and lower parts of the headwater area in the upper part of the headwater area anatomical changes within the roots were observed when heavy rainfall events occurred i e in 1958 1970 1971 1972 and 1985 roots in the lower part of the headwater area had become exposed during continuous rainfalls in 1997 and 2001 this research provides a fundamental review of dendrogeomorphological methodology applied to the identification of extreme geomorphic events acting within headwater areas

morphological and sedimentological responses of small stream channels to extreme rainfall and land use in the darjeeling himalayas abstract three pairs of small fourth to sixth order catchments approximately 5 80 km2 draining the margin of the darjeeling himalayas into the piedmont were selected for a comparison of the land use impact on the morphology and sedimentology of their stream channels each pair experienced similar annual rainfall and comprised similar metamorphic bedrock steep topography and brown soils the members of each pair contrast with respect to their land use structure as they comprise large forest cover forest 90 and a significant contribution of agricultural land with tea plantations forest

geomorphic changes in a complex gully system measured from sequential digital elevation models and implications for management high resolution digital elevation models dems were derived from sequential aerial photography of an active uvio mass movement gully complex in new zealand s north island east coast region to measure geomorphic changes over approximately one year the gully showed a complex behaviour combining uvial and mass movement erosion deposition and reworking of materials stored in an active debris fan during the measurement period 5200 1700 m3 of material were eroded from the 8 7 ha gully complex and 670 180 m3 from the 0 8 ha depositional fan giving a total of 5870 1710 m3 for the entire gully complex fan system the results provide a high resolution description of gully behaviour over a short time period and also demonstrate that mass movement slumping and debris ows accounted for almost 90 per cent 4660 200 m3 of the sediment generated this erosional response is described in terms of gully evolution by comparing the gully complex to other systems in the region in various stages of development the effect of gully evolution on geomorphic coupling between the gully complex and channel system is described and coupling is also shown to vary with the magnitude and frequency of rainfall events from a land management perspective the success of strategies such as tree planting to mitigate against gully erosion depends on the stage of gully development particularly on whether or not mass movement erosion has begun in contrast to gully rehabilitation efforts elsewhere basin wide afforestation in the early stages of gully incision is favoured over riparian planting given that mass movement assisted by excessive groundwater pressure is the main process leading to uncontrollable gully expansion to protect land effectively against continuing gully erosion of headwater catchments and resulting downstream aggradation it is necessary for land managers to understand the spatial and temporal variability of gully development fully so that mitigation efforts can be targeted appropriately copyright 2003 john wiley sons ltd

eulerian and lagrangian aspects of the longshore drift in the surf and swash zones a theoretical study of the mean longshore mass flux and longshore drift velocities due to waves obliquely incident on a uniform sloping beach is presented analysis is performed using both eulerian and lagrangian representations of the flow a number of results based on inviscid solutions are obtained concerning the mean longshore mass flux m y inside the swash zone thus m y depends on the parameters wave amplitude wave frequency and wave number of waves incident at a shoreline in a similar fashion to the dependence of the mass flux occurring between the crests and troughs of propagating waves on the same wave parameters the mass flux depends on the square of the local wave amplitude even for very steep waves which break before reaching the shoreline a lagrangian approach shows that particle paths are not closed even offshore of the breaking point and that zigzag transport is characteristic of lagrangian particle paths in the two dimensional horizontal flow seaward of the swash zone the cross shore profile of the longshore drift velocity is analyzed very weak longshore drift velocity characterizes the nonbreaking waves up to the swash zone onshore of the breaking point we find that the longshore drift velocity has a quasi linear profile up to the maximum velocity reached near the shoreline effects of seabed friction are included in the computation of cross shore profiles of the longshore drift velocity a sensitivity analysis reveals that even for relatively small friction parameters f 0 1 velocities inside the swash zone are greatly reduced the reduction in longshore drift velocity is greater for the lagrangian profile than for the eulerian one and for larger friction parameters f 0 1 the maximum longshore velocity moves toward the breaking point where the friction effects are smaller finally steady state profiles of the longshore drift velocities eulerian and lagrangian are computed

direct measurements of bed stress under swash in the field 1 utilizing flush mounted hot film anemometry the bed stress under swash was measured directly in a field experiment conducted on barret beach fire island new york the theory development and calibration of the instrument package are discussed and results from the field experiment are presented examples of bed stress time series throughout a swash cycle are presented and an ensemble averaged swash bed stress cycle is calculated strong asymmetry is observed between the uprush and backwash phases of the swash flow the maximum bed shear stress exerted by the uprush is approximately double that of the backwash while the duration of the backwash is 135 greater than that of the uprush friction coefficients in the swash zone are observed to be similar in magnitude to those from steady flow with the mean observed friction coefficient equal to 0 0037 swash friction coefficients derived from the current measurements exhibit a reynolds number dependence similar to that observed for other flows a systematic difference between coefficients for uprush and backwash is suggested

simulation and prediction of swash oscillations on a steep beach this paper presents numerical simulations and analytical predictions of key aspects of swash oscillations on a steep beach simulations of the shoreline displacement based on bore run up theory are found to give excellent agreement with recent experimental data for regular waves wave groups and random waves the theory is used to derive parameters that predict the onset of swash saturation and the spectral characteristics of the saturated shoreline motion these parameters are again in good agreement with the measured laboratory data and are also consistent with previous experimental data simulation of irregular wave run up using a series of overlapping monochromatic swash events is found to reproduce typical features of swash oscillations and can accurately describe both the low and high frequency spectral characteristics of the swash zone in particular the low frequency components of the run up can be modelled directly using a sequence of incident short wave bores with no direct long wave input to the numerical simulations this suggests that wave groupiness must be accounted for when modelling shoreline oscillations

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

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

estimating swash zone friction coefficients on a sandy beach abstract video based swash motions from three studies on two separate beaches were analyzed with respect to theoretical swash trajectories assuming plane beach ballistic motions under quadratic friction friction coefficient values for both the uprush and backwash were estimated by comparing measured swash space time trajectories to these theoretical expectations given an initial velocity and beach slope observations were made spanning high tides and in one case during a light rain analysis of over 4500 individual swash events showed that the uprush friction coefficient was nearly constant during all three studies with a mean value of roughly 0 007 and showed no trends over a tidal cycle in contrast backwash friction coefficient values varied over the tidal cycles ranging between 0 01 and 0 07 with minimum values corresponding to the highest tides although these values are close to the theoretical estimates based on a law of the wall formulation and values commonly referenced in the literature these observations show a consistent tendency for backwash friction estimates to greatly exceed uprush friction estimates the disparity between uprush and backwash friction coefficients can be partially attributed to the exclusion of a pressure gradient term in the ballistic model however results indicate that backwash friction coefficients adjusted to account for this effect may be three times larger than the uprush friction values during lower tides this tidal dependence for backwash friction coefficients is attributed to a complex interaction between swash infiltration and entrained sediment loads these findings imply that friction estimates necessary for sediment transport calculations and hydrodynamic predictions based solely on grain roughness may not be correct for backwash flows

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

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

sand suspension storage advection and settling in surf and swash zones a time dependent cross shore sediment transport model in the surf and swash zones on beaches is developed to predict both beach accretion and erosion under the assumptions of alongshore uniformity and normally incident waves the model is based on the depth integrated sediment continuity equation which includes sediment suspension by turbulence generated by wave breaking and bottom friction sediment storage in the entire water column sediment advection by waves and wave induced return current and sediment settling on the movable bottom the hydrodynamic input required for this sediment transport model is predicted using the finite amplitude shallow water equations including bottom friction the developed model is compared with three large scale laboratory tests with accretional neutral little and erosional beach profile changes under regular waves the model predicts sediment suspension under the steep front of breaking waves and due to bottom friction in the swash zone the computed depth averaged sediment concentration does not respond to local sediment suspension instantaneously because of the sediment storage and advection the mean sediment concentration becomes large in comparison to the oscillatory concentration with the decrease of the normalized sediment fall velocity the net cross shore sediment transport rate is shown to be the small difference between the onshore transport rate due to the positively correlated oscillatory components of the suspended sediment volume per unit area and the horizontal sediment velocity and the offshore transport rate due to the product of the mean suspended sediment volume and the mean horizontal sediment velocity relatedly the net accretion or erosion rate of the movable bottom is determined by the small difference between the mean sediment settling rate and the mean suspension rate caused by wave breaking and bottom friction the present computation is limited to the initial beach profile change but the numerical model is capable of predicting the accretional erosional and neutral profile changes

discrete particle model for sheet flow sediment transport in the nearshore fully three dimensional discrete particle computer simulations of high concentration sheet flow transport in oscillatory flows quantify the effect of fluid acceleration on bed load transport in highly unsteady flows typical of nearshore marine environments a simple impulse momentum approach explains simulation results and forms the basis for adding an acceleration related term to widely used energetics sediment transport formulae transport predicted by the acceleration term becomes increasingly significant as wave shape approaches the sawtooth profile characteristic of surf zone bores simulations integrate f ma and a corresponding set of equations for the torques for each sphere normal and tangential forces between contacting particles are linear functions of the distance between sphere centers and the relative tangential displacement at the contact point respectively particle interactions are both inelastic and frictional pressure gradient forces generated by the passage of surface gravity waves drive fluid and particle motion in a stack of thin horizontal fluid layers that exchange momentum and exert fluid drag added mass and buoyancy forces on particles transport properties of the simulated granular fluid assemblage are robust to large variations in material properties of the particles simulated transport rates agree with available experimental data for unsteady transport of coarse sands the mode of bed load motion dispersion of bed load particles and particle segregation by size and density are qualitatively consistent with available particle scale observations of bed load transport of natural particles

exploiting remote imagery in an embayed sandy beach for the validation of a runup model framework storm surge and wave runup are key determinants of the potential for beach overwashing during storm events however the prediction and quantification of wave runup on embayed beaches is strongly influenced by particular characteristics e g irregular morphology low tides absence of swell etc which differ from those on open beaches and have rarely been investigated in literature in the present paper a model framework aimed at predicting wave induced runup on an embayed sandy beach is validated by means of measurements derived from a video monitoring station recently installed in south italy during two storm events in 2016 the numerical approach employs meteocean forecasted waves within swan and swash models in both 2 d and 1 d mode the combination of multibeam and d rtk surveys with unmanned aerial vehicle uav imagery provides high resolution depth grid m 0 015 particularly required in shallow waters where wave hydrodynamics is highly influenced by the bottom the results show and discuss the agreement between video measurements and 2 d predictions of runup a sensitivity analysis of the manningfls roughness factor is needed in 1 d simulations the accuracy of the empirical formulas in predicting wave runup in an embayed beach is also investigated showing mainly an overestimation of the observations

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

swash zone boundary conditions for long wave models abstract in this note a description of swash zone boundary conditions for implementation in wave resolving and wave averaging long wave models is given along with a discussion of the role of such conditions on the modelling of the entire surf zone hydro morphodynamics

integral flow properties of the swash zone and averaging part 2 shoreline boundary conditions for wave averaged models shoreline boundary conditions for nearshore hydrodynamic models are discussed on the basis of the swash zone equations of brocchini peregrine 1996 swash zone flows are investigated further using the shallow water equations results from numerical computations are used to guide approximation to provide more practical boundary conditions for wave averaged flows approximate boundary conditions valid for small values of the rate of change of the mean water volume in the swash zone are found which allow explicit computation of a non zero mean water depth at the mean shoreline this is computed in terms of the local height of the short waves implementation issues are also discussed

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

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

the swash of solitary waves on a plane beach flow evolution bed shear stress and run up the swash of solitary waves on a plane beach is studied using large scale experiments ten wave cases are examined which range from non breaking waves to plunging breakers the focus of this study is on the influence of breaker type on flow evolution spatiotemporal variations of bed shear stresses and run up measurements are made of the local water depths flow velocities and bed shear stresses using a shear plate sensor at various locations in the swash zone the bed shear stress is significant near the tip of the swash during uprush and in the shallow flow during the later stages of downrush in between the flow evolution is dominated by gravity and follows an explicit solution to the nonlinear shallow water equations i e the flow due to a dam break on a slope the controlling scale of the flow evolution is the initial velocity of the shoreline immediately following waveform collapse which can be predicted by measurements of wave height prior to breaking but also shows an additional dependence on breaker type the maximum onshore directed bed shear stress increases significantly onshore of the stillwater shoreline for non breaking waves and onshore of the waveform collapse point for breaking waves a new normalization for the bed shear stress which uses the initial shoreline velocity is presented under this normalization the variation of the maximum magnitudes of the bed shear stress with distance along the beach which is normalized using the run up follows the same trend for different breaker types for the uprush the maximum dimensionless bed shear stress is approximately 0 01 whereas for the downrush it is approximately 0 002

discussion of measurement of wave by wave bed levels in the swash zone by ian l turner paul e russell tony butt coastal eng 55 2008 1237 1242 this paper is a discussion of turner et al measurement of wave by wave bed levels in the swash zone the discussion highlights previous work on the same topic that in fact demonstrated swash by swash measurements of total net sediment transport but which was not presented by turner et al the discussion highlights the advantages and disadvantages of the two measurement methods and the problem of longshore sediment motion which can introduce errors c 2008 elsevier b v all rights reserved

integral flow properties of the swash zone and averaging the swash zone is that part of a beach over which the instantaneous shoreline moves back and forth as waves meet the shore this zone is discussed using the nonlinear shallow water equations which are appropriate for gently sloping beaches a weakly three dimensional extension of the two dimensional solution by carrier greenspan 1958 of the shallow water equations for a wave reflecting on an inclined plane beach is developed and used to illustrate the ideas thereafter attention is given to integrated and averaged quantities the mean shoreline might be defined in several ways but for modelling purposes we find the lower boundary of the swash zone to be more useful a set of equations obtained by integrating across the swash zone is investigated as a model for use as an alternative boundary condition for wave resolving studies comparison with sample numerical computations illustrates that they are effective in modelling the dynamics of the swash zone and that a reasonable representation of swash zone flows may be obtained from the integrated variables the longshore flow of water in the swash zone is in many ways similar to the stokes drift of propagating water waves further averaging is made over short waves to obtain results suitable as boundary conditions for longer period motions including the effect of incident short waves in order to clearly present the work a few simplifications are made the main result is that in addition to the kinematic type of boundary condition that occurs on a simple e g rigid boundary two further conditions are found in order that both the changing position of the swash zone boundary and the longshore flow in the swash zone may be determined models of the short waves both outside and inside the swash zone are needed to complete a full wave averaged model only brief indication is given of such modelling

role of pressure gradients in sheet flow of coarse sediments under sawtooth waves 1 discrete particle model dpm simulations have been performed to directly examine the role of horizontal pressure gradients acting on the wave bottom boundary layer wbbl during the process of sheet flow transport in the surf zone the dpm is a two phase wbbl model that directly couples a one dimensional eddy viscosity fluid flow to a three dimensional particle model newton s third law is enforced at every simulation time step through fluid particle interaction forces of buoyancy drag and added mass simulations are able to reproduce bedload transport rates from a laboratory data set for coarse sediment distributions consequently simulations of a monochromatic sawtooth wave were performed with three coarse grain size distributions to investigate the relative importance of bed shear stresses horizontal pressure forces and fluid particle drag forces on bedload transport processes the simulation results demonstrate that the magnitude of the horizontal pressure force acting directly on sediment embedded in the wbbl is small compared to the magnitude of the particle drag force or particle stress however the phasing of the onshore peak in the horizontal pressure force with respect to the particle drag force is important to sediment mobilization and enhances the observed onshore bias in bed load flux removing the horizontal pressure force on the sediment particles resulted on average in a 30 reduction in net bed load flux in the surf zone free stream fluid accelerations are typically equated to the horizontal pressure gradient thus the simulations may explain why the fluid acceleration can be a successful parameter for aiding in sediment transport predictions in the surf zone

suspended sediment transport mechanisms in high energy swash abstract measurements of suspended sediment concentration at three heights above the bed and cross shore velocity at a single height were obtained using miniature optical backscatter sensors and a miniature electromagnetic current meter from the swash zone of a high energy macrotidal dissipative beach time series from relatively low h s 0 8 m and high h s 2 2 m energy conditions were chosen for analysis possible onshore and offshore sediment transport mechanisms are identified as a sudden offshore to onshore velocity transition and turbulence in the swash front leading to subsequent onshore advection by the uprush and b low frequency high velocity backwashes exceeding a certain threshold for sediment suspension these mechanisms are related to the velocity field through skewness and asymmetry an increase in negative infragravity skewness in high energy conditions suggests a potential shift towards offshore net transport time averaged vertical profiles of cross shore suspended sediment flux were calculated from the velocity and concentration time series these show a tendency towards offshore transport in high energy conditions particularly at low levels in the water column the actual sediment fluxes are believed to be more offshore than those calculated one reason for this discrepancy is the inability of the instruments to detect swash activity at very low levels in the water column

experimental study of bore run up bore propagation near the shoreline the transition from bore to wave run up and the ensuing run up motion on a uniformly sloping beach are investigated experimentally as a bore approaches the shoreline the propagation speed first decelerates by compressing its wave form and then suddenly accelerates at the shoreline although this behaviour is qualitatively in agreement with the inviscid shallow water wave prediction the acceleration is caused by the momentum exchange process

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

environmental factors controlling spatial variation in sediment yield in a central andean mountain area a large spatial variability in sediment yield was observed from small streams in the ecuadorian andes the objective of this study was to analyze the environmental factors controlling these variations in sediment yield in the paute basin ecuador sediment yield data were calculated based on sediment volumes accumulated behind checkdams for 37 small catchments mean annual specific sediment yield ssy shows a large spatial variability and ranges between 26 and 15 100 mg km 2 year 1 mean vegetation cover c fraction in the catchment i e the plant cover at or near the surface exerts a first order control on sediment yield the fractional vegetation cover alone explains 57 of the observed variance in ln ssy the negative exponential relation ssy a x e b c which was found between vegetation cover and sediment yield at the catchment scale 10 3 10 9 m 2 is very similar to the equations derived from splash interrill and rill erosion experiments at the plot scale 1 10 3 m 2 this affirms the general character of an exponential decrease of sediment yield with increasing vegetation cover at a wide range of spatial scales provided the distribution of cover can be considered to be essentially random lithology also significantly affects the sediment yield and explains an additional 23 of the observed variance in ln ssy based on these two catchment parameters a multiple regression model was built this empirical regression model already explains more than 75 of the total variance in the mean annual sediment yield these results highlight the large potential of revegetation programs for controlling sediment yield they show that a slight increase in the overall fractional vegetation cover of degraded land is likely to have a large effect on sediment production and delivery moreover they point to the importance of detailed surface vegetation data for predicting and modeling sediment production rates c 2007 elsevier b v all rights reserved

suspended sediment transport and beach dynamics induced by monochromatic conditions long waves and wave groups abstract this study presents the analysis of the water surface elevation velocity and suspended sediment concentration measurements obtained at a large wave flume under mobile bed conditions the wave reproduced erosive and accretive conditions and included monochromatic short waves perturbed with a free long wave bichromatic and random conditions each tested condition started from a handmade 1 15 slope and lasted for an approximate time period of 2 4 h 6 runs of the selected wave condition to compare the different beach profile developments and in particular the events that control sediment transport in the swash and surf zones all erosive tested conditions produced a shoreline retreat and a bar at the breaking area whose development in time is directly correlated to the length of the breaking area on the other hand not all accretive conditions present a shoreward transport and random conditions do not seem to alter the initial profile the processed data show the suspended sediment event control produced by the existence or absence of wave backwash interactions in the swash zone the existence of these interactions and their number within the wave group will be a key parameter in controlling the sediment stirring water velocity magnitudes and therefore the suspended sediment fluxes in the inner surf and outer swash

riemann wave description of erosional dam break flows this work examines the sudden erosional flow initiated by the release of a dam break wave over a loose sediment bed extended shallow water equations are formulated to describe the development of the surge accounting for bed material inertia a transport layer of finite thickness is introduced and a sharp interface view of the morphodynamic boundary is adopted approximations are sought for an intermediate range of wave evolution in which equilibration of the sediment load can be assumed instantaneous but momentum loss due to bed friction has not yet been felt the resulting homogeneous hyperbolic equations are mathematically tractable using the riemann techniques of gas dynamics dam break initial conditions give rise to self similar flow profiles the wave structure features piecewise constant states two smoothly varied simple waves and a special type of shock an erosional bore forming at the forefront of the wave profiles are constructed through a semi analytical procedure yielding a geomorphic generalization of the stoker solution for dam break waves over rigid bed for most flow properties the predictions of the theoretical treatment compare favourably with experimental tests visualized using particle imaging techniques

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

the existence and break up of the antarctic land bridge as indicated by both amphi pacific distributions and tectonics abstract amphi pacific disjunct distributions between south america and australasia are correlated with the breakup and changing palaeo climate of gondwana for a long period with a temperate climate antarctica formed a land bridge between australia and south america allowing species to disperse vicariate between both continents dated phylogenies in the literature showing sister clades with a distribution disjunction between south america and australia were used for the correlation the initiation of the antarctic circumpolar current and a change to a colder antarctic climate is associated with the opening of the drake passage between south america and antarctica at c 30 ma and the final separation of australia and antarctica along the south tasman rise at c 45 ma the distribution data highlighted the existence of a southern disjunct distribution pattern which may be the result of continental vicariance dispersal this is strongly indicative of a connection between antarctica south america and australia which later provided a dispersal pathway and facilitated vicariance after break up the taxa that likely dispersed vicariated via antarctica included all species with a more sub tropical climate preference twelve distributions younger than 30 ma are interpreted as the result of long distance dispersal between south america and australia these taxa are suited to a temperate climate the climatic signal shown by all taxa is possibly a consequence of the australian plate s asynchronous rifting over tens of millions of years in combination with climate changes these events may have provided opportunities for tropical and sub tropical species to disperse and speciate earlier than what we observe for the more temperate taxa

flow and sediment transport induced by a plunging solitary wave 1 two parallel experiments involving the evolution and runup of plunging solitary waves on a sloping bed were conducted 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 and for observation of the morphological changes the two experimental conditions were kept as similar as possible the experiments showed that the complete sequence of the plunging solitary wave involves the following processes shoaling and wave breaking runup rundown and hydraulic jump and trailing wave the bed shear stress measurements showed that the mean bed shear stress increases tremendously with respect to that in the approaching wave boundary layer by as much as a factor of 8 in the runup and rundown stages and that the rms value of the fluctuating component of the bed shear stress is also affected by as much as a factor of 2 in the runup and hydraulic jump stages the pore water pressure measurements showed that the sediment at or near the surface of the bed experiences upward directed pressure gradient forces during the down rush phase the magnitude of this force can reach values as much as approximately 30 of the submerged weight of the sediment the experiments further showed that the sediment transport occurs in the sheet flow regime for a substantial portion of the beach covering the area where the entire sequence of the wave breaking takes place the bed morphology is explained qualitatively in terms of the measured bed shear stress and the pressure gradient forces

eulerian flow velocities in the swash zone field data and model predictions measurements of eulerian flow velocity obtained within the swash zone on a relatively steep beach face gradient 1 23 are compared with an extended ballistic swash model the model only requires a friction factor beach slope and terminal bore velocity as input the following model predictions matched well with observations 1 the maximum eulerian flow velocity is the shoreline velocity when it arrives at the fixed point of interest on the beach face 2 at any location the time of flow reversal occurs prior to the shoreline reaching its maximum landward excursion 3 the maximum flow velocity in the backwash is the velocity recorded as the shoreline recedes past the fixed point of interest and this is less than the maximum uprush velocity and 4 the duration of the uprush flow is shorter than the duration of the backwash flow previous studies have already confirmed that the ballistic swash model including friction can accurately predict shoreline motion and maximum run up on steep beaches this study shows that it is similarly successful in predicting eulerian flow velocities during individual swash events the model does not presently account for interacting swash however and so may be less appropriate on gently sloping beaches

human impact on geomorphic processes and hazards in mountain areas in northern spain abstract the temporal occurrence of slope movements their contribution to relief evolution and human influence on those processes in two study areas of northern spain are presented the work is based on temporal analyses covering 100 ka in one study area and 43 years in the other temporal analysis has been the basis for quantitatively assessing the magnitude of human influence and developing landslide susceptibility and hazard models with known independently tested prediction capability the results obtained in one study area show a relationship between landsliding periods and increasing precipitation during upper pleistocene and holocene significant increases of landslide frequency and mobilisation rate were also found around 5500 and 200 years ago those moments coincide with two periods of intensified human presence and activities neolithic and industrial revolutions the increase observed represents about one order of magnitude from pre neolithic to present a similar increase has been found between 1954 and 1997 in the other study area the latter increase shows no relationship with changes in climate parameters or seismic activity a fairly good correlation has been found between landslide frequency and socioeconomic indicators of human activity sedimentation rates in two neighbouring estuaries were determined and significant increases particularly in the second part of last century were also found evidence obtained suggest that the increases observed in the frequency of slope instability events and therefore hazard denudation and sedimentation rates are due to a greater extent to indirect geomorphologic changes caused by human action rather than climate change detailed analysis of landslide frequency during that 43 year period has also been used to produce and validate landslide susceptibility models and obtain landslide hazard maps with known prediction accuracy validation tests were carried out comparing susceptibility maps based on landslides that have occurred in the past with the ones occurring in several later periods prediction capability of models could thus be determined validation of susceptibility maps using data derived from the temporal analysis of landslides was used to obtain hazard maps expressed as probability of new ruptures in a given time period on the basis of past trends in terrain behaviour possible impacts of a growing influence of human activities on the terrain have been incorporated into the assessment of future hazards by considering different scenarios

hillslope deposits in gravel bed rivers and their effects on the evolution of alluvial channel forms a case study from the sudetes and carpathian mountains this paper describes initiation and development of specific alluvial channel forms connected with the supply of coarse grained hillslope sediment the study was carried out in gravel bed rivers located in mid mountain areas the sudetes and the carpathian mountains in central europe in the river channels studied where input of hillslope material is abundant patterns of sedimentation and erosion are determined by hillslope processes two types of primary sediment source in mountain temperate rivers with flat valley floors were identified mass movements in particular landslides and supply of angular coarse grained slope material to streams from cut bank sections the introduced coarsest hillslope sediment is only entrained during floods which destabilize the river systems downstream of the supply points at these river channel sections development of new and transformation of existing alluvial channel forms is observed sediment accretion and progradation of bars downstream of the hillslope sediment delivery zones hsd zones is connected with activity of these zones frequency of hillslope sediment supply size of coarse grained angular deposits introduced into the river channels and frequency of flood events the largest depositional forms such as gravel rich debris longitudinal bars lateral bars with a rock block core and lateral bars downstream of an hsd zone comprise coarse usually gravel sized sediment the main feature of their initiation and progradation is deposition of large rock blocks within or at a short distance downstream of the supply points lateral sediment accretion of the bars leads to river channel constriction during subsequent floods and development of other alluvial channel forms such as transverse gravel rich debris ribs diffuse gravel rich debris sheets side debris bars and small sandy rich gravel separation bars these forms create depositional complexes which are observed in the river channel within the zone of the hillslope sediment supply and for a few hundred meters downstream

the influence of seaward boundary conditions on swash zone hydrodynamics abstract the influence of the seaward boundary condition on the internal swash hydrodynamics is investigated new numerical solutions of the characteristics form of the nonlinear shallow water equations are presented and applied to describe the swash hydrodynamics forced by breaking wave run up on a plane beach the solutions depend on the specification of characteristic variables on the seaward boundary of the swash zone equivalent to prescribing the flow depth or the flow velocity it is shown that the analytical solution of shen and meyer shen m c meyer r e 1963 climb of a bore on a beach part 3 runup j fluid mech 16 113 125 is a special case of the many possible solutions that can describe the swash flow but one that does not appear appropriate for practical application for real waves the physical significance of the boundary conditions is shown by writing the volume and momentum fluxes in terms of the characteristic variables results are presented that illustrate the dependence of internal flow depth and velocity on the boundary condition this implies that the internal swash hydrodynamics depend on the shape and wavelength of the incident bore which differs from the hydrodynamic similarity inherent in the analytical solution a solution appropriate for long bores is compared to laboratory data to illustrate the difference from the analytical solution the results are important in terms of determining overwash flows flow forces and sediment dynamics in the run up zone

modelling of waves and currents around submerged breakwaters abstract recent experimental data collected during the delos project are used to validate two approaches for simulating waves and currents in the vicinity of submerged breakwaters the first approach is a phase averaged method in which a wave model is used to simulate wave transformation and calculate radiation stresses while a flow model 2 dimensional depth averaged or quasi 3d is used to calculate the resulting wave driven currents the second approach is a phase resolving method in which a high order 2dh boussinesq type model is used to calculate the waves and flow the models predict wave heights that are comparable to measurements if the wave breaking sub model is properly tuned for dissipation over the submerged breakwater it is shown that the simulated flow pattern using both approaches is qualitatively similar to that observed in the experiments furthermore the phase resolving model shows good agreement between measured and simulated instantaneous surface elevations in wave flume tests

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

widespread inclination shallowing in permian and triassic paleomagnetic data from laurentia support from new paleomagnetic data from middle permian shallow intrusions in southern illinois usa and virtual geomagnetic pole distributions abstract recent paleomagnetic work has highlighted a common and shallow inclination bias in continental redbeds the permian and triassic paleomagnetic records from laurentia are almost entirely derived from such sedimentary rocks so a pervasive inclination error will expectedly bias the apparent polar wander path of laurentia in a significant way the long standing discrepancy between the apparent polar wander paths of laurentia and gondwana in permian and triassic time may be a consequence of such a widespread data pathology here we present new middle permian paleomagnetic data from igneous rocks and a contact metamorphosed limestone from cratonic laurentia the exclusively reversed middle permian magnetization is hosted by low ti titanomagnetite and pyrrhotite and yields a paleomagnetic pole at 56 3 s 302 9 e a95 3 8 n 6 this pole which is unaffected by inclination shallowing suggests that a shallow inclination bias may indeed be present in the laurentian records to further consider this hypothesis we conduct a virtual geomagnetic pole distribution analysis comparing theoretical expectations of a statistical field model tk03 gad against published data sets this exercise provides independent evidence that the laurentian paleomagnetic data is widely biased likely because of sedimentary inclination shallowing we estimate the magnitude of this error from our model results and present and discuss several alternative corrections

integral properties of the swash zone and averaging part 3 longshore shoreline boundary conditions for wave averaged nearshore circulation models the aim of the present work final of a three part series is to analyse in detail flow motions within the swash zone and define suitable shoreline boundary conditions for the longshore flow for wave averaged circulation models the analyses of parts 1 and 2 are extended to cover horizontally two dimensional flows an analytical solution for the longshore motion representing the drift velocity of the whole swash zone water mass is found this is seen to be approximated well by the ratio between the time integral of the longshore momentum flux crossing the swash lower boundary and the swash zone net water volume further a complete set of shoreline boundary conditions taking into account wave wave interactions is obtained on the basis of fully numerical solutions of the nonlinear shallow water equations the main focus of the work is to clarify the structure of the shoreline boundary conditions for the longshore flow but attention has also been paid to their derivation and assessment from the numerical solutions the latter have been obtained on the basis of a fairly broad range of input wave conditions which though biased towards those typical of reflective beaches are believed to cover conditions also typical of moderate dissipative beaches two main terms are found to contribute to the longshore drift velocity i a term proportional to the shallow water velocity accounting for short wave interactions frictional swash zone forces and continuous forcing due to non breaking wave nonlinearities and ii a drift type term representing the momentum transfer due to wave breaking

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

bed level fluctuations in the inner surf and swash zone of a dissipative beach abstract a field study was conducted on a dissipative beach to quantify inner surf and swash zone bed level change during periods of inundation and throughout a tidal cycle elevation changes were acquired at millimeter resolution with a new conductivity concentration profiler that allowed quantification of the bed level throughout the duration of the wave swash cycle and also during periods of bed exposure bed level change spectra showed the highest energy at low frequencies even though event scale net bed level changes were observed to exceed the tidal scale net bed level change net bed level change for individual events was nearly normally distributed with most individual events displaying little or no net bed level change large erosion and accretion events with bed level elevation magnitudes that exceeded net tidal elevation change occurred with similar frequency the similarity between the frequency of large erosion and large accretion events suggests that a few events may be ultimately responsible for the observed net elevation change over the tidal cycle the large events displayed different hydrodynamic characteristics erosion events had longer duration onshore directed flow and higher maximum onshore directed velocity magnitude than offshore directed velocity magnitude the opposite was found for accretion events that had longer duration offshore directed flow and a higher maximum offshore directed velocity magnitude than onshore directed velocity magnitude

observations of swash zone velocities a note on friction coefficients 1 vertical flow structure and turbulent dissipation in the swash zone are estimated using cross shore fluid velocities observed on a low sloped fine grained sandy beach raubenheimer 2002 with two stacks of three current meters located about 2 5 and 8 cm above the bed the observations are consistent with an approximately logarithmic vertical decay of wave orbital velocities within 5 cm of the bed the associated friction coefficients are similar in both the uprush and downrush as in previous laboratory results turbulent dissipation rates estimated from velocity spectra increase with decreasing water depth from o 400 cm2 s3 in the inner surf zone to o 1000 cm2 s3 in the swash zone friction coefficients in the swash interior estimated with the logarithmic model and independently estimated by assuming that turbulent dissipation is balanced by production from vertical shear of the local mean flow and from wave breaking are between 0 02 and 0 06 these values are similar to the range of friction coefficients 0 02 0 05 recently estimated on impermeable rough nonerodible laboratory beaches and to the range of friction coefficients 0 01 0 03 previously estimated from field observations of the motion of the shoreward edge of the swash run up

suspended sediment transport in the swash zone of a dissipative beach abstract simultaneous high frequency field measurements of water depth flow velocity and suspended sediment concentration were made at three fixed locations across the high tide swash and inner surf zones of a dissipative beach the dominant period of the swash motion was 30 50 s and the results are representative of infragravity swash motion suspended sediment concentrations loads and transport rates in the swash zone were almost one order of magnitude greater than in the inner surf zone the vertical velocity gradient near the bed and the resulting bed shear stress at the start of the uprush was significantly larger than that at the end of the backwash despite similar flow velocities this suggests that the bed friction during the uprush was approximately twice that during the backwash the suspended sediment profile in the swash zone can be described reasonably well by an exponential shape with a mixing length scale of 0 02 0 03 m the suspended sediment transport flux measured in the swash zone was related to the bed shear stress through the shields parameter if the bed shear stress is derived from the vertical velocity gradient the proportionality coefficient between shear stress and sediment transport rate is similar for the uprush and the backwash if the bed shear stress is estimated using the free stream flow velocity and a constant friction factor the proportionality factor for the uprush is approximately twice that of the backwash it is suggested that the uprush is a more efficient transporter of sediment than the backwash because the larger friction factor during the uprush causes larger bed shear stresses for a given free stream velocity this increased transport competency of the uprush is necessary for maintaining the beach otherwise the comparable strength and greater duration of the backwash would progressively remove sediment from the beach

palaeoecology and sedimentology of carboniferous glacial and post glacial successions in the paganzo and rio blanco basins of northwestern argentina

experimental validation and characterization of mean swash zone boundary conditions 1 performances of recently developed shoreline boundary conditions for wave averaged nearshore flow solvers are evaluated on the basis of available experimental data applications of the model to experimental data show the chosen equations suitably determine boundary values required for one dimensional mean flow a detailed illustration is also given of the characteristics of flow properties which appear in the model it is finally shown that very simple conditions can be suitably used at the mean shoreline of wave averaged flows for which boundary values of position water depth and velocity are computed on the basis of local quantities known at the seaward boundary of the swash

on the transport of suspended sediment by a swash event on a plane beach we develop solutions for the transport of suspended sediment by a single swash event following the collapse of a bore on a plane beach and we investigate the morphodynamical role that such transport may play although the intrinsic asymmetry between uprush and backwash velocities tends to encourage the export of sediment we find that swash events may be effective in distributing across the swash zone much or all of the sediment mobilised by bore collapse additionally settling lag effects may promote a weak onshore movement of sediment we quantify both effects in terms of the properties of the sediment and of the swash event and comment on the relationship between our findings and recent field studies of swash zone sediment transport

the effects of deforestation on slope and channel evolution in the tectonically active darjeeling himalaya the main indicators of quaternary tectonic uplift are the young mountain slopes of the darjeeling himalaya rising straight above the ganga brahmaputra foredeep fragments of uplifted river terraces and fresh fault scarps evidence for the continuation of the uplift includes downcutting of the tista and other straight rivers in the bedrock continuing aggradation in the plains and overriding of the metamorphic rocks on the alluvia owing to deforestation and extensive land use the earlier natural tendency of a dominance of channel incision over slope degradation has changed to prevailing aggradation even in steep valley reaches caused by intensive slope mass movements and the overloading of the mountain creeks aggradation progresses upstream along the rivers dissecting the mountain front

large eddy simulation of dam break driven swash on a rough planar beach turbulence characteristics in the swash zone are investigated using a 3d large eddy simulation model the numerical model is implemented based on openfoam which solves the filtered navier stokes equations for two immiscible fluids with a standard smagorinsky sub grid scale closure the numerical model is validated with laboratory data for swash flow driven by a dam break apparatus the model results demonstrate that the main characteristics of turbulence in the swash zone are different from those in the surf zone which are mainly induced by surface wave breaking during uprush phase bore generated turbulence has 2d turbulence characteristics because of limited water depth near bed generated turbulence is mainly observed during backwash turbulence production and turbulent dissipation rate estimated from the model results indicate an imbalance possibly due to advection at swash front and large roughness used touching down of turbulent coherent structure tcs is observed during uprush which drives intense bed shear stress during the backwash interaction between tcs and bed is less clear however finger like patterns in the spatial extent of bed shear stress and vertical components of vorticity are predicted during the backwash the location of the strongest finger patterns in the vertical direction is collocated with that of maximum turbulence production these finger patterns are likely caused by boundary layer instabilities injected vertically from the bed this article is protected by copyright all rights reserved

wave run up on a high energy dissipative beach 1 because of highly dissipative conditions and strong alongshore gradients in foreshore beach morphology wave run up data collected along the central oregon coast during february 1996 stand in contrast to run up data currently available in the literature during a single data run lasting approximately 90 min the significant vertical run up elevation varied by a factor of 2 along the 1 6 km study site ranging from 26 to 61 of the offshore significant wave height and was found to be linearly dependent on the local foreshore beach slope that varied by a factor of 5 run up motions on this high energy dissipative beach were dominated by infragravity low frequency energy with peak periods of approximately 230 s incident band energy levels were 2 5 to 3 orders of magnitude lower than the low frequency spectral peaks and typically 96 of the run up variance was in the infragravity band a broad region of the run up spectra exhibited an f 4 roll off typical of saturation extending to frequencies lower than observed in previous studies the run up spectra were dependent on beach slope with spectra for steeper foreshore slopes shifted toward higher frequencies than spectra for shallower foreshore slopes at infragravity frequencies run up motions were coherent over alongshore length scales in excess of 1 km significantly greater than decorrelation length scales on moderate to reflective beaches

petrogenesis and tectonic implications of the early paleozoic intermediate and mafic intrusions in the south qinling belt central china constraints from geochemistry zircon u pb geochronology and hf isotopes abstract the characteristics and tectonic implications of the early paleozoic alkaline magmatic belt in the south qinling belt which was originally part of the northern yangtze block prior the devonian have remained elusive whether this magmatic belt is related to rifting of the passive continental margin to back arc extension in the active continental margin or to mantle plume activity is debated understanding the origin and geodynamic significance of this magmatic belt can provide new constraints on the early paleozoic tectonic evolution of the northern yangtze block here we present zircon u pb data from a suite of nepheline syenite quartz syenite diabase and gabbro from the northern margin of the yangtze block which show an age range of ca 435 440 ma the ehf t values of the intermediate rocks up to 16 59 suggest magma generation from depleted mantle sources and new crustal growth geochemically the syenites showing high total alkali contents and are enriched in lree lile rb ba and k and hfse th u nb ta zr and hf with depletion in sr p and ti the intermediate and mafic magmatic rocks were generated through magmas sourced from the subcontinental lithospheric mantle metasomatized by asthenospheric mantle and underwent fractional crystallization without significant crustal contamination the magmatic suite represents a significant phase of crustal extension in the northern margin of the yangtze block

osl dating of a holocene loess paleosol sequence in the southern loess plateau china optically stimulated luminescence osl dating of polymineral fine grained loess samples collected from the southern loess plateau of china was conducted using the single aliquot regenerative dose sar protocol a double sar procedure in which aliquots are subjected to both infrared ir and blue stimulations was used and two sets of equivalent dose d e determinations were produced these doses are assumed to be predominantly related to the feldspathic and quartz fine grain populations respectively the results revealed that the osl ages estimated by infrared stimulated luminescence irsl signals and those estimated by post ir stimulated luminescence post ir osl signals disagreed specifically the ages estimated using the irsl signals were smaller than those estimated using post ir osl signals the results of an anomalous fading test of the two types of osl signals revealed that the post ir osl signals from the etched sub sample by h2sif6 and hf and the un etched sub sample did not fade significantly however the irsl signals from the un etched sub sample showed obvious signs of fading these findings indicate that the lower age estimated by irsl is due to the anomalous fading of feldspar ir signals in the polymineral fine grains for samples collected from greater than 100 cm the estimates of their osl ages using two types of luminescence signals generally agreed with their pre estimated ages especially those of the post ir osl signals however for the three samples that were collected from a depth of less than 100 cm their osl ages were remarkably underestimated possibly due to the enhanced human activity such as soil cultivation that has occurred in the region since 3000 a b p

the response of slope and channel systems to various types of extreme rainfall a comparison between the temperate zone and humid tropics abstract the mountain slopes and river channels of the temperate zone and of the humid tropics are modelled by various types of extreme rainfall in the flysch carpathians the leading role is played by continuous rains causing floods and landslides rainy seasons wet years mobilizing deep landslides and to a smaller degree by local downpours in the darjeeling himalaya with young relief and uplift tendency the main influence on modelling the mountain slopes and river channels have been the extreme continuous rains separated by several decades of normal rainy season playing the preparatory or relaxation role with simultaneous transformation of slopes and river channels in both cases human impact has caused the acceleration of runoff and mobilization of sediment the higher extremes of precipitation and steep slopes in the humid tropics are balanced to some extent in temperate zones by the lower infiltration rates and lower thresholds of mass mobility on the gentle slopes originated in the periglacial environment

coupling between landslides and eroding stream channels reconstructed from spruce tree rings examples from the carpathians and sudetes central europe the analysis of the positive feedback between landslides and erosion requires determination of the precise temporal and spatial relations between events of colluvium delivery and fluvial erosion in our study we use decennial datasets on the occurrence of landsliding and erosion achieved through dendrochronological methods four sites covering areas of landslide slopes and adjacent valley floors with stream channels were studied landsliding on slopes was dated from the tree ring eccentricity developed in stems tilted due to bedrock instability erosion in channels was dated using the wood anatomy of roots exposed by erosion of the soil cover analysis of the temporal relations between dated landsliding erosion and precipitation record has revealed that two types of repeating sequences can be observed 1 rainfall landsliding erosion 2 rainfall erosion landsliding these sequences are an indication of the occurrence of slope channel positive feedback in the sites studied in the first type landsliding triggered by rainfall delivers colluvia into the valley floor and causes its narrowing which in turn causes increased erosion in the second type erosion triggered by rainfall disturbs the slope equilibrium and causes landsliding landsliding and erosion once triggered by precipitation can occur alternately in years with average precipitation and reinforce one another bidirectional coupling between landsliding and channel erosion was shown notably through the effects of channel shifting and forced sinuosity and by increased erosion of the slopes opposite the active landslides observations also suggest that the repetition of sequences described over longer periods of time can lead to a general widening of the valley floor at the expense of slopes and to a gradual change of the valley cross profile from narrow v shaped into a wide flat bottomed thus landsliding erosion coupling positive feedback was recognized as an important factor shaping hillslope valley topography of the mid mountain areas studied copyright 2014 john wiley sons ltd

sediment transport and beach morphodynamics induced by free long waves bound long waves and wave groups new laboratory data are presented on the influence of free long waves bound long waves and wave groups on sediment transport in the surf and swash zones as a result of the very significant difficulties in isolating and identifying the morphodynamic influences of long waves and wave groups in field conditions a laboratory study was designed specifically to enable measurements of sediment transport that resolve these influences the evolution of model sand beaches each with the same initial plane slope was measured for a range of wave conditions firstly using monochromatic short waves subsequently the monochromatic conditions were perturbed with free long waves and then substituted with bichromatic wave groups with the same mean energy flux the beach profile changes and net cross shore transport rates were extracted and compared for the different wave conditions with and without long waves and wave groups the experiments include a range of wave conditions e g high energy moderate energy low energy waves which induce both spilling and plunging breakers and different turbulent intensities and the beaches evolve to form classical accretive erosive and intermediate beach states the data clearly demonstrate that free long waves influence surf zone morphodynamics and promote increased onshore sediment transport during accretive conditions and decreased offshore transport under erosive conditions in contrast wave groups which can generate both forced and free long waves generally reduce onshore transport during accretive conditions and increase offshore transport under erosive conditions the influence of the free long waves and wave groups is consistent with the concept of the relative fall velocity h wst as a dominant parameter controlling net beach erosion or accretion free long waves tend to reduce h wst promoting accretion while wave groups tend to increase the effective h wst promoting erosion

deterministic coastal morphological and sediment transport modeling a review and discussion 1 modern coastal ocean modeling systems are now capable of numerically simulating a variety of coastal and estuarine problems and can thus provide useful information for managing coastal zones here we review state of the art eulerian implementations of bottom up sediment transport and morphological change in coastal ocean hydrodynamic models in order to investigate the fate of suspended sediment in coastal and estuarine waters as well as the evolution of sea or river beds sediment dynamics need to be represented at a scale relevant to the numerical discretized solution and significant effort is devoted to parameterize sediment processes we discuss boundary layer hydrodynamics and the computation of the bed shear stress we also focus on approaches used to represent near bed processes such as bed load transport and sediment erosion and deposition sediment diffusivities settling velocities and cohesive processes such as flocculation all have an impact on suspended sediment throughout the water column we then describe the implementation of process parameterizations in coastal hydrodynamic models explicitly reviewing five widely used systems the approaches implemented in these coastal models may present distinct strengths and shortcomings with regard to some important issues for coastal zones both numerical and physical while these detailed limitations need to be considered as part of model assessment more general issues also hinder present state of the art models in particular sediment transport is inherently highly empirical which is further compounded by issues arising from turbulence closure schemes we conclude by suggesting some possible directions toward improving sediment dynamics understanding and coastal scale predictive ability

an experimental study of wave run up at a steep beach this paper presents experiments on run up of strongly nonlinear waves on a beach of 10 54 inclination velocity fields are obtained by the piv particle image velocimetry technique acceleration measurements are also attempted but it is difficult to obtain useful results in every case in addition free surface profiles are extracted from digital images and wave resistance probes the investigation focuses on the dynamics of the early stages of the run up when steep fronts evolve in the vicinity of the equilibrium shoreline but maximum run up heights are also reported measurements on moderately nonlinear waves are compared to results from long wave theories including a numerical boussinesq model and analytic shallow water results from the literature in particular the applicability of the long wave theories is addressed however most attention is given to run up of high incident solitary waves that are on the brink of breaking at the shoreline in one case a temporarily slightly overturning wave front is found that neither develops into a plunger or displays appreciable spilling this feature is discussed in view of measured velocity and acceleration patterns and with reference to the dam break problem effects of scaling as well as viscous damping are also briefly discussed

paleomagnetism of the jurassic transantarctic mountains revisited evidence for large dispersion of apparent polar wander within less than 3myr the transantarctic mountains predominantly consist of jurassic continental flood basalts kirkpatrick and sills ferrar emplaced during the earliest phase of the break up of pangea published ages based on a variety of geochronological methods all agree rather well and cluster around 180 ma suggesting emplacement during a rather short time interval of not more than 3 myr paleomagnetic studies mostly carried out between the 60s and 90s of the last century however yield two well defined but significantly different groups of paleomagnetic pole positions plotting either in intermediate latitudes a or at latitudes exceeding 60 degrees s b pole positions belonging to group a are generally interpreted to be of primary origin whereas the significance of group b poles remains unclear here we report new data from the kirkpatrick basalts of northern victoria land antarctica where 157 oriented paleomagnetic samples were taken covering about 800 m of stratigraphy and 23 volcanic flows in gair mesa 73 4666 degrees s 162 8666 degrees e after removal of a steep magnetic overprint with rather low coercivities straight linear segments of exclusively normal polarity trending toward the origin of projection are identified in 151 samples from 22 sites maximum unblocking temperatures do not exceed 580 degrees c and maximum coercivities not 60 mt the resulting mean virtual geomagnetic pole vgp for the gair mesa plots at 66 4 degrees s 227 7 degrees e alpha 95 of 6 2 degrees k 25 7 comparable to group b poles reflecting light microscopy reveals that the magnetic inventory of all samples analyzed is dominated by magnetite showing shrinking cracks and broad ilmenite lamellae the latter being diagnostic for high temperature oxidation analysis of the distribution of the 22 pole positions obtained here shows that secular variation has successfully been averaged s b 15 9 degrees suggesting that the rocks studied here have recorded the time averaged geomagnetic field during early mid jurassic times based on these new results we postulate that both clusters a and b of pole positions reflect primary magnetizations and that the kirkpatrick basalts of gair mesa have been emplaced in a rather short normal polarity time interval of 3 myr if our reasoning is correct the apparent polar wander path for the latest early jurassic might be more complex than previously thought whether this complexity is evidence for massif true polar wander remains speculative c 2015 international association for gondwana research published by elsevier b v all rights reserved

swash infiltration exfiltration and sediment transport field measurements of vertical pore pressure gradients within the bed are used to quantify instantaneous 8 hz rates of swash infiltration exfiltration across the beach face cyclic infiltration exfiltration is associated with individual swash events with observed vertical flow rates o 10 3 m s rates of net swash groundwater exchange i e through bed flow integrated over several swash cycles are two orders of magnitude smaller at the timescale of individual swashes vertical pore pressure gradients within the beach face are much greater than horizontal pore pressure gradients this permits application of the numerical solution of darcy s law for one dimensional vertical flow to model fluctuating pore pressures and hence vertical through bed flow vertical flow through a porous bed modifies sediment mobility in at least two ways 1 seepage forces change the effective weight of surficial sediments and 2 boundary layer thickening or thinning result in altered bed shear stresses by considering these two opposing effects separately a new shields parameter is derived that incorporates terms for through bed flow simulation of time varying seepage force and bed stress effects over an uprush backwash cycle suggests that the effect of altered bed stresses dominates over the change in effective weight and that infiltration exfiltration effects are most important during uprush simulated transport rates are increased by up to 40 of the peak transport rate during uprush and reduced by 10 during backrush in summary swash infiltration exfiltration across a saturated beach face enhances the net upslope transport of sediment

swash overtopping a truncated plane beach swash on a plane beach is modelled by using a solution of the shallow water equations due to shen meyer 1963 the equations are used in a form appropriate for a plane at a finite angle to the horizontal the beach is cut off at a level below that of the maximum run up and the water is taken to fall freely over the end of the beach an explicit solution is found which permits evaluation of the overtopping flow and total volume for one swash event

swash zone sediment suspension and transport and the importance of bore generated turbulence a study of swash zone sediment transport was conducted at gleneden beach oregon during february 25 28 1994 the data collected included suspended sediment concentration ssc sea surface elevation and velocity initially 4 and 8 cm above the bed at three cross shore locations within the swash zone spanning high tides ensemble averages of 6 9 and 12 s duration swash events showed that the uprush suspension was high concentrated in the leading edge and nearly vertically uniform above the lower 1 2 cm of the water column shortly after the sensors were inundated by run up the sediment rapidly settled out of the water during flow reversal the ssc was small but increased again in the backwash backwash vertical profiles were markedly different from uprush profiles with much of the suspension being confined to very near the bed where strong vertical gradients in ssc existed these marked differences show that the backwash is not simply the reverse of the uprush implying significant differences in the underlying fluid dynamics and sediment transport mechanisms backwash sediment suspension increased with flow duration however ensemble averaged ssc profiles of varying duration showed that the backwash concentrations were not consistent at the same temporal phases which suggests that water depth in addition to flow duration may be a controlling factor strong cross shore gradients in ssc suggest that bore derived turbulence may affect local sediment transport specifically our data show this bore generated turbulence turbulent kinetic energy directly influences local sediment suspension hence standard bed shear bagnold type sediment transport models may no longer be valid in the vicinity of the bore in the vicinity of the bore a higher correlation between bore generated turbulence and suspended sediment transport was found than between a bagnold type formulation and suspended sediment transport

test of self organization in beach cusp formation 1 field observations of swash flow patterns and morphology change are consistent with the hypothesis that beach cusps form by self organization wherein positive feedback between swash flow and developing morphology causes initial development of the pattern and negative feedback owing to circulation of flow within beach cusp bays causes pattern stabilization the self organization hypothesis is tested using measurements from three experiments on a barrier island beach in north carolina beach cusps developed after the beach was smoothed by a storm and after existing beach cusps were smoothed by a bulldozer swash front motions were recorded on video during daylight hours and morphology was measured by surveying at 3 4 hour intervals three signatures of self organization were observed in all experiments first time lags between swash front motions in beach cusp bays and horns increase with increasing relief representing the effect of morphology on flow second differential erosion between bays and horns initially increases with increasing time lag representing the effect of flow on morphology change because positive feedback causes growth of beach cusps third after initial growth differential erosion decreases with increasing time lag representing the onset of negative feedback that stabilizes beach cusps a numerical model based on self organization initialized with measured morphology and alongshore uniform distributions of initial velocities and positions of the swash front at the beginning of a swash cycle reproduces the measurements except for parts of one experiment where limited surveys and a significant low frequency component to swash motions might have caused errors in model initialization

non random distribution of euler poles is plate tectonics subject to rotational effects terra nova 24 467 476 2012 abstract a full global physically coherent geodynamical model over 600 ma has been developed at the university of lausanne during the past 20 years based on the paleodyn database compiling information of geodynamical interest one of the outstanding results presented herein is the distribution of euler poles axis around which tectonic plates are moving on the earth s surface from one reconstruction to another which are not randomly distributed but smeared out along a weakly developed girdle the scattering reflects the tendency of plates to follow a random evolution however the distribution along a preferential plane best fitted plane suggests a long term influence on plate motion the fact that the poles predominantly lie within the inter tropical zone together with the computed net rotation throughout the phanerozoic indicating a westward drift suggest a long term influence of rotational effects

shear stress and sediment transport calculations for swash zone modelling it is shown that the observed difference in sediment transporting efficiency by the swash uprush compared with the downrush could be mainly due to greater bed shear stress for a given velocity in the more abruptly accelerated uprush the bed shear stress generated by an arbitrary free stream velocity time series is modelled in terms of usual wave boundary layer models plus a phase lead phi tau of the bed shear stress compared with the free stream velocity at the peak frequency with this approach the total transport amounts in uprush and downrush can be modelled satisfactorily with the same sediment transport formula without the need for different uprush and downrush coefficients while the adaptation of sediment transport formulae from steady flow can thus lead to the right total amounts of sediment moved by this method the timing of the instantaneous sediment transport rates are probably not accurately modelled due to the highly unsteady nature of the swash and the presence of pre suspended sediment in the uprush nevertheless the proposed method is a useful intermediate step before we have a complete understanding of sediment transport under very rapid accelerations and of the relative contribution of pre suspended sediment to the onshore sediment transport in swash zones c 2002 published by elsevier science b v