beach face evolution in the swash zone we investigate swash on an erodible beach using the one dimensional shallow water equations fully coupled to a bed evolution exner equation in particular the dam break bore collapse initial condition of shen meyer j fluid mech vol 16 1963 pp 113 125 and peregrine williams j fluid mech vol 440 2001 pp 391 399 is investigated using a numerical model based on the method of characteristics a sediment transport formula cubic in velocity u au 3 is used here this belongs to a family of sediment transport formulae for which pritchard hogg coastal engng vol 52 2005 pp 1 23 showed that net sediment transport under the shen meyer 1963 bore collapse is offshore throughout the swash zone when a non erodible bed is considered it is found that full coupling with the beach although still resulting in the net offshore transport of sediment throughout the swash zone leads to a large reduction in the net offshore transport of sediment from the beach face this is particularly true for the upper third of the swash zone moreover in contradistinction to swash flows over non erodible beds flows over erodible beaches are unique to the bed mobility and porosity under consideration this has very important implications for run up predictions the conclusion is that it is essential to consider full coupling of water and bed motions i e full morphodynamics in order to understand and predict sediment transport in the swash regardless of other physical effects e g turbulence infiltration pre suspended sediment etc

well balanced and flexible morphological modeling of swash hydrodynamics and sediment transport abstract existing numerical models of the swash zone are relatively inflexible in dealing with sediment transport due to a high dependence of the deployed numerical schemes on empirical sediment transport relations moreover these models are usually not well balanced meaning they are unable to correctly simulate quiescent flow here a well balanced and flexible morphological model for the swash zone is presented the nonlinear shallow water equations and the exner equation are discretized by the shock capturing finite volume method in which the numerical flux and the bed slope source term are estimated by a well balanced version of the slic slope limited centered scheme that does not depend on empirical sediment transport relations the satisfaction of the well balanced property is demonstrated through simulating quiescent coastal flow the quantitative accuracy of the model in reproducing key parameters i e the notional shoreline position the swash depth the flow velocity the overtopping flow volume the beach change depth and the sediment transport rate is shown to be satisfactory through comparisons against analytical solutions experimental data as well as previous numerical solutions this work facilitates an improved modeling framework for the swash hydrodynamics and sediment transport

variation of copper isotopes in chalcopyrite from dabu porphyry cu mo deposit in tibet and implications for mineral exploration abstract the study presents copper cu isotope data of mineral separates of chalcopyrite from four drill core samples in the miocene dabu porphyry cu mo deposit formed in a post collisional setting in the gangdese porphyry copper belt southern tibet copper isotope values in hypogene chalcopyrite range from 1 48 to 1 12 displaying a large variation of up to 2 60 which demonstrates cu isotope fractionation at high temperature during hydrothermal evolution the majority of measured chalcopyrite isotopic compositions show a gradual increasing trend from 1 48 to 1 12 with the increase of drilling depth from 130m to 483m as the alteration assemblages change from potassic to phyllic similarly the other 65 cu values 65 cu 65 cu 63 cu sample 65 cu 63 cu standard 1 1000 of the chalcopyrite show a gradual increasing trend from 1 48 to 0 59 with the decrease of drilling depth from 130 m to 57 m as the alteration assemblages change from potassic phyllic through argillic to relatively fresh these observations suggest a genetic link between cu isotope variation and silicate alteration assemblages formed at different temperatures indicative of a rayleigh precipitation process resulting in the large variation of 65 cu values at dabu in general samples closest to the center of hydrothermal system dominated by high temperature potassic alteration are isotopically lighter whereas samples dominated by low temperature phyllic alteration peripheral to the center are isotopically heavier the predicted flow pathways of hydrothermal fluids are from no 0 to no 3 exploration line and the lightest 65 cu values are the most proximal to the hydrothermal source finally we propose that the northwest side of the no 0 exploration line has high potential for hosting undiscovered orebodies the pattern of cu isotope variation in conjunction with the features of silicate alteration in porphyry system can be used to trace the hydrothermal flow direction and to guide mineral exploration

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

advances in numerical modelling of swash zone dynamics we present a comprehensive and critical review of work on the numerical modelling of swash zone processes between 2005 and 2015 a wide range of numerical models has been employed for the study of this region and hence only phase resolving approaches i e depth averaged and depth resolving models are analyzed the current advances in the modelling of swash zone processes are illustrated by comparing different numerical models against laboratory experiments of a dam break driven swash event depth averaged and depth resolving models describe well the swash flow for both coarse sand and gravel impermeable beach cases depth averaged models provides a practical tool for engineering use whereas depth resolving models improve the flow description especially for the backwash phase with a significantly higher computational cost the evolution and magnitude of bed shear stresses predicted by all models is reasonable when compared with laboratory estimates based on the log law however differences between modelling approaches cannot be rigorously evaluated owing to the uncertainty in shear stress estimates while employing such approximation furthermore small scale processes such as turbulence evolution are investigated with depth resolving models finding differences between the two dimensional and three dimensional approaches numerical models allow us to investigate other processes such as beach morphology changes the evolution of the turbulence coherent structures and the infiltration exfiltration effects on the swash flow a discussion on the advantages and limitations of each model is presented the future of swash zone modelling depends on the increase of the computational power and more importantly on the improvement of the current capability to obtain intra wave measurements for model validation calibration and greater resolution of physical processes

numerical modelling of the flow and bed evolution of a single bore driven swash event on a coarse sand beach abstract this paper examines the numerical prediction of the sediment transport and bed evolution for a single swash event on a coarse sediment beach in these conditions bed load is the dominant mode of sediment transport laboratory experiments of a single bore driven swash event are simulated numerically using a fully coupled model that solves the system of non linear shallow water equations and the exner sediment conservation formula the analysis focuses on two aspects the optimal choice of parameters for the meyer peter and muller sediment transport formula and the model used for computing the shear stress the methods tested for the bed shear stress are the momentum integral method and the chezy formulation in which the friction factor is computed using two different formulae infiltration into the beach and its effects on the shear stress and sediment transport are also modelled results show that the basic meyer peter and muller sediment transport formula provides good results in the run up on the other hand the sediment transport in the early stage of the backwash is overestimated a reduction of the sediment mobility constant in the formula in the backwash marginally improves the results however the causes of the overestimation of the sediment transport at the early stage of the backwash is the overestimation of the shear stress while at later stages there are several contributions that are identified i e modelling of the sediment transport and infiltration it is also suggested that the meyer peter and muller sediment transport formula might not capture the complexity of the processes involved during the backwash the comparison of the methods for the estimate of the bed shear stress show that comparable results can be obtained using the momentum integral method and the chezy formulation with time and space varying friction factor the resulting bed evolution is also described in the predicted final profile deposition is found in the upper part of the beach and erosion in the lower part a bed step is formed just below the position of the initial shoreline this feature is determined by the onset of a hydraulic jump during the backwash

transport of atmospheric water vapor by volcanic eruption columns contrary to assumptions often made in the literature explosive volcanic eruptions are capable of transporting significant amounts of water into the stratosphere in addition to the magmatic water component atmospheric water vapor is entrained by the column at lower levels a theoretical model for the conservation of mass momentum and thermal energy of four separate components dry air water vapor liquid condensates and solid particles is used to determine the extent of atmospheric water redistribution we examine the effects of water vapor condensation on dynamical characteristics and ambient water vapor transport a simple technique is presented for deriving canonical forms for the complex system of ordinary differential equations governing the column components solutions of this model are presented that show the influence of different volcanic boundary conditions and a range of ambient water vapor distributions on transport of the buoyant column we show that the water component vapor liquid of small eruption columns rising through a wet atmosphere is dominated by entrained water whereas larger columns are dominated by the magmatic water this is due in part to the proportionately smaller entrainment surface area in relation to the control volume for the larger columns we also show that a maintained column with an initial mass flux of 2 7 108 kg s 1 erupted into a wet atmosphere would inject 96 mt of water vapor into the stratosphere over 24 hours comparable to the annual input from methane oxidation or 100 midlatitude thunderstorms this increase may accelerate the conversion of simultaneously erupted volcanic so2 into sulfuric acid

shoreline motion in nonlinear shallow water coastal models abstract different shoreline boundary conditions for numerical models of the non linear shallow water equations based on godunov type schemes are compared the study focuses on the peregrine and williams peregrine d h williams s m 2001 swash overtopping a truncated plane beach journal of fluid mechanics 440 391 399 problem of a single bore collapsing on a slope this is considered the best test to assess performances of the shoreline boundary treatments in terms of all the parameters of interest in swash zone modelling emphasis is given to the shoreline trajectory and flow velocity modelling a mismatch of the velocity at the early stage of the motion is highlighted most of the tested techniques perform similarly in terms of maximum run up the backwash phase is critical in all cases starting from the brocchini et al brocchini m bernetti r mancinelli a albertini g 2001 an efficient solver for nearshore flows based on the waf method coastal engineering 43 2 105 129 shoreline boundary treatment a simple technique that improves the accuracy of velocity predictions is also developed a sensitivity analysis of the domain resolution and the threshold value of the water depth that defines a wet cell is also presented

riemann solution for a class of morphodynamic shallow water dam break problems this paper investigates a family of dam break problems over an erodible bed the hydrodynamics are described by the shallow water equations and the bed change by a sediment conservation equation coupled to the hydrodynamics by a sediment transport bed load law when the initial states ul and ur are sufficiently close to each other the resulting solutions are consistent with the theory proposed by lax 1973 that for a riemann problem of n equations there are n waves associated with the n characteristic families however for wet dry dam break problems over a mobile bed there are 3 governing equations but only 2 waves one wave vanishes because of the presence of the dry bed when initial left and right bed levels bl and br are far apart it is shown that a semi characteristic shock may occur which happens because unlike in shallow water flow on a fixed bed the flux function is non convex in these circumstances it is shown that it is necessary to reconsider the usual shock conditions instead we propose an implied internal shock structure the concept of which originates from the fact that the stationary shock over fixed bed discontinuity can be regarded as a limiting case of flow over a sloping fixed bed the needham hey 1991 approximation for the ambiguous integral term rhdb in the shock condition is improved based on this internal shock structure such that mathematically valid solutions that incorporate a morphodynamic semi characteristic shock are arrived at

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

explosive volcanic eruptions v observations of plume dynamics during the 1979 soufriere eruption st vincent summary during the 1979 eruption of the soufritre of st vincent west indies a 14min period of explosive activity occurred on april 22 the first three minutes of this activity were filmed five individual explosions formed distinct plumes which fed an eruption column which eventually ascended to a height of over 18 km the ascent velocities of the fronts of these plumes ranged from 8 5 to 61 7m s the half angle of spreading of the plume fronts ranged from 21 5 to 24 one of the plumes was observed to 8 km height and decelerated steadily from 5 1 5 to 23 m s l the main column fed by individual explosions was however observed to accelerate from 8 5 to 58 m s l in the same height interval a theoretical treatment of volcanic plume motion is presented measurements of dimensions velocities and spreading rates from the film are used to estimate plume parameters such as temperature particle content and volume discharge rate of magma from the theoretical relationships these calculations show that the individual plumes became hotter and richer in juvenile ash with time the acceleration of the main eruption column was the result of being fed by increasingly hotter and more ash rich explosions an average volume discharge rate of 12600m3s is estimated from the analysis of the plume motions this value agrees closely with an estimate of discharge rate based on the heat flux required to form an 18 km high column this agreement suggests that theories of convective motions in plumes can be successfully adapted to the volcanic case as long as the effect of hot entrained ash particles is considered

the morphodynamics of a swash event on an erodible beach a high accuracy numerical solution coupling one dimensional shallow water and bed evolution equations with for the first time a suspended sediment advection equation thereby including bed and or suspended load is used to examine two swash events on an initially plane erodible beach the event of peregrine williams j fluid mech vol 440 2001 pp 391 399 and that of a solitary wave approaching the beach equations are solved by the method of characteristics and the numerical model is verified full coupling of suspended load to beach change for peregrine williams j fluid mech vol 440 2001 pp 391 399 yields only slightly altered swash flows depending on beach mobility and sediment response time a series of similar final beach change patterns results for different beach mobilities suspended and bed load transport have distinct morphodynamical signatures for the solitary wave a backwash bore is created hibberd peregrine j fluid mech vol 95 1979 pp 323 345 this morphodynamical bore propagates offshore initially and leads to the creation of a beach bed step larson sunamura j sedimentary petrology vol 63 1993 pp 495 500 primarily due to bed load transport its height is directly related to bed load mobility and also depends strongly on the bed friction coefficient the shock dynamics of this bed step is explained and illustrated bed and suspended load mobilities are quantified using field data and an attempt is made to relate predictions to measurements of single swash events on a natural beach average predicted bed change magnitudes across the swash are of the order of 2 mm with maximum bed changes of up to approximately 10 cm at the bed step

influence of particle aggregation on deposition of distal tephra from the may 18 1980 eruption of mount st helens volcano the may 18 1980 eruption of mount st helens msh produced an extensive ashfall deposit in washington idaho and montana with a minumum volume of 0 55 km3 tephra an unusual feature of the deposit is the occurrence of a second thickness maximum 325 km ene of msh near ritzville washington grain size and component abundance analysis of samples along the main dispersal axis indicates that ash in this region is very fine grained mean size 22 m poorly sorted polymodal and rich in glass shards and pumice fragments a computer simulation of ash fallout from an atmospherically dispersed eruption plume was developed to evaluate various hypotheses for the origin of the distal ash characteristics particularly the thickness versus distance relationship the model was constrained by observations of the eruption column height elevation of major ash transport lateral spreading of the eruption plume and atmospheric wind structure in the vicinity of msh results of different simulations indicate that the second thickness maximum cannot be attributed to either decreased wind velocities over central washington or injection of fine ash above the horizontal wind velocity maximum near the tropopause for the model to fit the observed characteristics of the deposit significant particle aggregation of ash finer than 63 m must be invoked the best fit occurs when ash less than 63 m is aggregated into particles several hundred microns in diameter with a settling velocity of 0 35 m s support for this process comes from the observation and collection of fragile ash clusters of similar size which fell at pullman washington during the may 18 eruption sorem 1982 the premature fallout of fine ash as particle aggregates is a fundamental process in the origin of the grain size characteristics variations in component abundances and thickness versus distance relationship of the may 18 msh ash fall deposit

sediment transport by waves and currents a bed load model based on a generalization of bagnold s 1954 constitutive equations together with the assumption of similarity profiles for velocity and concentration was proposed for sediment transport by waves by sleath 1994 this model is now extended to wave current flows and applied to three different situations a oscillatory flows with superimposed currents b net transport produced by progressive waves over a flat horizontal bed and c longshore transport induced by waves approaching a beach in all three cases the model gives reasonable agreement with experiment in the case of longshore transport the model produces almost the same formula as that of the coastal engineering research center 1977 apart from additional terms for density and grain size

hydro and morpho dynamic modeling of breaking solitary waves over a fine sand beach part i experimental study abstract the objectives of this work are 1 to examine the mechanisms that influence tsunami erosion and deposition mechanisms in the littoral zone via physical simulations of breaking solitary waves over a fine sand beach and 2 to provide experimental data for validation of numerical models to predict tsunami erosion and deposition processes the experiments were carried out in a 48 8 m 2 16 m 2 1 m wave flume the flume was instrumented to observe free surface elevations cross shore velocities suspended sediment concentrations vertical and cross shore pore pressure gradients near the shoreline and morphological changes in addition wave sediment interactions were observed via underwater video cameras the results are systematically analyzed to investigate the roles of wave breaking bore runup wave drawdown and wave induced pore pressure variations on tsunami erosion and deposition processes the studies showed that the wave plunging on a thin layer of water prior to reaching the shoreline did not cause much sediment suspension while the waterjet impinging directly on the beach entrained substantial amounts of sand the suspended sediments were subsequently pushed up the slope by fluid momentum as the broken wave transformed to a turbulent bore a small net deposition region was observed near the maximum runup point where both the flow velocity and the water depth were near zero a significant amount of the sediment transport occurred during the wave drawdown in the form of thick sheet flow which resulted in net erosion of the shore face and the beach a hydraulic jump formed near the wave breaking region toward the end of the drawdown which caused most of the suspended sand to deposit in the wave breaking region consequently breaking solitary waves over a sloping fine sand beach led to net erosion of the shore face and the beach net deposition in a small region immediately seaward of the max excursion point and net deposition in the wave breaking zone

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

impact of a uniform bore on an erodible beach abstract the impact of a uniform bore on an erodible beach is investigated using a shallow water description and a sediment conservation equation the solution which is obtained using the method of characteristics employs a cubic bed load formula and a crudely calibrated sediment transport coefficient it is found that as with the fixed bed case of hibberd and peregrine 1979 a backwash bore forms which for the mobile bed also comprises a bed step it is found that this bed step achieves a significant height the volume of sand deposited above the final still water level is consistent with that observed under certain events on some sandy beaches

an analytical model for bore driven run up we use a hodograph transformation and a boundary integral method to derive a new analytical solution to the shallow water equations describing bore generated run up on a plane beach this analytical solution differs from the classical shen meyer runup solution in giving significantly deeper and less asymmetric swash flows and also by predicting the inception of a secondary bore in both the backwash and the uprush in long surf we suggest that this solution provides a significantly improved model for flows including swash events and the run up following breaking tsunamis

characterization of aerosols from eruptions of mount st helens measurements of mass concentration and size distribution of aerosols from eruptions of mount st helens as well as morphological and elemental analyses were obtained between 7 april and 7 august 1980 in situ measurements were made in early phreatic and later minor phreatomagmatic eruption clouds near the vent of the volcano and in plumes injected into the stratosphere from the major eruptions of 18 and 25 may the phreatic aerosol was characterized by an essentially monomodal size distribution dominated by silicate particles larger than 10 micrometers in diameter the phreatomagmatic eruption cloud was multimodal the large size mode consisted of silicate particles and the small size modes were made up of mixtures of sulfuric acid and silicate particles the stratospheric aerosol from the main eruption exhibited a characteristic narrow single mode with particles less than 1 micrometer in diameter and nearly all of the mass made up of sulfuric acid droplets

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

the possible effects of large 19th and 20th century volcanic eruptions on zonal and hemispheric surface temperatures abstract the contribution of volcanic material to the stratosphere from major eruptions within the last two centuries has been estimated using volcanological criteria including eruption type eruption column height volume and duration of eruption and composition and degree of fragmentation of magma the chronology of major explosive volcanic eruptions is compared with a record of mean surface temperature deviation t for the same interval constructed from all available temperature data the temperature records are divided into 6 latitudinal zones allowing analysis for individual zones where temperature changes induced by aerosol perturbation might be intensified we focus on the explosive volcanic events which by our estimates injected the most material into the stratosphere these include tambora 1815 krakatau 1883 santa maria 1902 katmai 1912 and quizapu 1932 such eruptions appear to have produced a consistent but small temperature decrease on the order of 0 2 to 0 5 c on a hemispheric scale for periods ranging from one to five years although these changes are similar to background temperature variations the maximum change in t after some of these explosions appears to lag by up to three years in going from equatorial to polar latitudes somewhat smaller eruptions e g agung 1963 and possibly cosiguina 1835 seem to have produced about the same perturbation in t as the larger eruptions this suggests either a limiting mechanism on loading of the aerosol layer after a volcanic eruption or that the composition of injected material i e the ratio of silicate dust to volatiles and composition of the volatiles may significantly effect stratospheric optical depth perturbation temperatures do not remain depressed for a longer period after a series of closely timed eruptions e g the 1881 1889 or the 1902 1903 sequences than after single events