landslide generated tsunamis at reunion island 1 landslides that occur on oceanic volcanoes can reach the sea and trigger catastrophic tsunamis reunion island has been the location of numerous huge landslides involving tens to hundreds of cubic kilometers of material we use a new two fluid seawater and landslide numerical model to estimate the wave amplitudes and the propagation of tsunamis associated with landslide events on reunion island a 10 km3 landslide from the eastern flank of piton de la fournaise volcano would lift the water surface by about 150 m where it entered the sea the wave thus generated would reach saint denis the capital of reunion island population of about 150 000 people in only 12 min with an amplitude of more than 10 m and would reach mauritius island in 18 min although mauritius is located about 175 km from the impact waves reaching its coast would be greater than those for reunion island this is due to the initial shape of the wave and its propagation normal to the coast at mauritius but generally coast parallel at reunion island a submarine landslide of the coastal shelf of 2 km3 would trigger a 40 m high wave that would severely affect the proximal coast in the western part of reunion island for a landslide of the shelf of only 0 5 km3 waves of about 2 m in amplitude would affect the proximal coast

layer thicknesses and velocities of wave overtopping flow at seadikes abstract seadikes often fail due to wave overtopping and a failure of the landward slope therefore these aspects have to be taken into account for the design of seadikes in present design the calculation of the crest height of seadikes is essentially based on using a design water level and the corresponding wave run up height an average overtopping rate is generally considered for wave overtopping which can not account for the stresses and other effects due to extreme individual overtopping events landward slope design is more or less based on experience it can be concluded from failure analysis that dike failures on the landward slope are rather initiated by individual overtopping events in particular by the related overtopping flow velocities and layer thicknesses which are relevant for the prediction of erosion infiltration and slip failure therefore overtopping flow velocities and layer thicknesses are required in addition to average overtopping rates as hydraulic boundary conditions for the geotechnical stability analysis of seadikes the objective of the present paper is the theoretical and experimental determination of overtopping flow velocities and layer thicknesses on the seaward slope the dike crest and the landward slope of a seadike overtopping parameters are derived on the basis of small scale model tests which are required for the design of the landward slope and to avoid dike failures by wave overtopping in the future for the prediction of the layer thicknesses and the velocities of the overtopping flow on the seaward slope the dike crest and the landward slope a set of theoretical formulas is derived and validated by hydraulic scale model tests

predicting the crest height of a gravel beach the beach crest is a common morphological feature formed by the deposition of sediment carried up slope by wave swash the elevation to which waves can pile gravel is a function of the size and density of the material relative to the hydraulic components of swash velocity wave frequency and runup height two equations 17 and 21 that predict the height of the beach crest to the wave forces and the beach material are derived the first derivation compares the wave force acting to move a stone up the beach face with a weight force acting to hold the stone in place the second derivation relates the potential energy per unit area of the beach crest to the total wave energy that lifted and deposited the material above a given sea level datum as a test of the derived equations the actual crest height of one natural gravel beach was accurately estimated by both equations derived further research and testing on other natural beaches are needed to fully verify eqs 17 and 21 a comparison of other equations eqs 2 3 and 4 that predict crest height is also made the poor fit of the other equations are a result of using values for the coefficients that were established in wave tank experiments another shortcoming of eqs 3 and 4 is that they do not include variables related to the beach material hence they predict that all particle sizes from sand to boulders would be piled to the same elevation by the same wave forcing eq 2 includes a particle size variable but predicts increasingly higher beach crests for larger particles more realistic results for all three equations eqs 2 3 and 4 would be expected with field tested values for the coefficients but a range in values for each different beach would be necessary the advantage of eqs 17 and 21 is that equations are not dependent on coefficients whose values come from correlation with other data sets

nabukelevu volcano mt washington kadavu a source of hitherto unknown volcanic hazard in fiji nabukelevu volcano 805 m is a small ca 3 4 km3 hornblende biotite andesite dome breccia complex it is the youngest in a plio pleistocene series of volcanoes related to a presently inactive subduction zone in southern fiji we present new evidence of up to four holocene eruption episodes from this volcano with onshore evidence of the latest activity post 1686 40 years bp and offshore evidence of tephra falls between 2250 70 and 780 50 years bp scoriaceous pyroclastic flow deposits of one eruptive episode contain pottery fragments presumably entrained from habitation areas during emplacement like many composite edifices in moist climates nabukelevu is prone to failure the propensity in this case exacerbated by up to three edifice cutting fault zones the fault induced weak and saturated zones have been the focus of repeated edifice failure through late holocene debris avalanches of between 10 100 million m3 many of these avalanches entered the sea and these or additional submarine failures of the lower island flanks have led to emplacement of at least one major late holocene submarine mass flow deposit with distinctive mineralogy in the suva basin to the north two of the debris avalanches dated at post 2350 140 and post 1750 60 years bp apparently inundated local habitation areas and the deposits incorporate pottery and human remains a widespread local legend describing catastrophic events on nabukelevu corresponds in content with geologic findings to provide additional evidence of a late holocene eruptive and debris avalanche disaster on kadavu during the latter part of the last ca 2000 years of human occupation possibly as recent as between ad 1630 and 1680 the present hazardscape of the nabukelevu area includes common landslides induced by frequent earthquake swarms and cyclones larger edifice failures possibly related to volcanism or fault movement have the potential to create local tsunami which under favourable conditions could reach areas near fiji s capital suva 110 km to the north

modeling of landslide generated impulsive waves considering complex topography in reservoir area the impulsive wave is considered as one of the most notably secondary hazards induced by landslides in reservoir areas the impulsive wave with considerable wave amplitude is able to cause serious damage to the dam body shoreline properties and lives to investigate and predict the wave characteristics many experimental studies employed the generalized channels rather than the realistic topography deviation from the idealized geometries may result in non negligible effects due to the wave refraction or reflection with complex topography to consider the topography effect a prototype scaled experiment was conducted a series of tests with different collocation of parameters were performed the experimental results were then summarized to propose empirical equations to predict the maximum wave amplitude and wave decay in channel direction the generalized empirical equations can obtain better results for wave features prediction by compared with those derived from the idealized models furthermore a 3d numerical modeling corresponding to the physical experiment was conducted based on the sph method the wave characteristics in the sliding and channel directions were investigated in detail including the maximum wave amplitude wave run up wave arrival time and wave crest amplitude decay the comparison between the simulation and experiment indicates the promising accuracy of the sph simulation in determining the general features even with complex river topography finally the limitation and applicability of both the experimental and numerical methods in analyzing the practical engineering problems were discussed combination of the both methods can benefit the hazard prevention and reduction for landslide generated impulsive waves in reservoir area

numerical modelling of tsunami generation and propagation from submarine slumps the 1998 papua new guinea event summary deep and large submarine slumps may generate tsunamis as disastrous as tsunamis of tectonic origin such a landslide is likely to be the origin of the 1998 july 17 tsunami of papua new guinea the deadliest tsunami in the last 50 years water waves devastated a 20 km stretch of coastline wiping out three villages and killing more than 2200 people a numerical model has been developed to study the efficiency of deep slumps in producing tsunamis and has been applied to the papua new guinea event the landslide is treated as the flow of a homogeneous gravity driven continuum governed by a rheological law water waves are generated by sea bottom displacements induced by the landslide the shallow water approximation is adopted for both the landslide and the associated water waves the resulting differential equations are solved by a finite difference method based on shock capturing the shallow water hypothesis is tested by comparison with a model solving navier stokes equations for a mixture of water and sediments sensitivity tests carried out for a 2 d simplified geometry show that the water surface profile depends strongly on the constitutive law of the landslide the 1998 event is simulated numerically by the shallow water model testing different friction laws the observed inundation height distribution is well reproduced by the model for a volume of 4 km3 with its top located at a water depth of 550 m and sliding with a coulomb type friction law over a distance of 5 km

numerical modeling of the september 13 1999 landslide and tsunami on fatu hiva island french polynesia 1 on september 13 1999 omoa bay fatu hiva island french polynesia was struck by 2 to 5 m high water waves several buildings were flooded and destroyed but no lives were lost observations gathered during a post event survey revealed the recent collapse into the sea of a 300 300 m2 at least 20 m thick cliff located 5 km southeast of omoa this cliff failure most certainly triggered the tsunami waves since the cliff was reported intact 45 min earlier we simulate the tsunami generation due to a subaerial landslide using a finite difference model assimilating the landslide to a flow of granular material numerical modeling shows that a 0 0024 km3 landslide located in the presumed source area accounts for the tsunami waves reported in omoa bay we show that the striking amplification observed in omoa bay is related to the trapping of waves due to the shallow submarine shelf surrounding the island

generation mechanism of tsunamis from the 1883 krakatau eruption the 1883 eruption of krakatau generated a destructive tsunami which claimed about 34 000 lives we compute the generation and propagation of tsunamis from three models previously proposed they are 1 large scale caldera collapse of the northern part of krakatau island 2 emplacement of pyroclastic flow deposits 3 submarine explosion we numerically solve the non linear shallow water equations on actual bathymetry all three models displace the same volume 11 5 km 3 of water in different ways we compare the results of our computation with the observed tsunami waveforms at batavia and tsunami wave heights along the coasts of java and sumatra the comparison shows that the submarine explosion model of 1 to 5 min duration best explains the generation of the largest tsunami

numerical modeling of an underwater bingham plastic mudslide and the waves which it generates underwater landslides are a common source of tsunamis in coastal areas theoretical and experimental studies on this problem however are scarce because of the difficulties in modeling and observing a submarine slide and the associated tsunami to study this problem we present a numerical model that simulates the coupling of a bingham plastic mudslide on a gentle uniform slope with the surface waves which it generates a formulation of the dynamics of the problem is presented where the landslide is treated as an incompressible bingham plastic flow and the water motion is assumed irrotational the long wave approximation is adopted for both water waves and the mudslide dispersion of waves and potential turbulent mixing are not considered the resulting differential equations are solved by a finite difference method we present the numerical results for successive profiles of the mud surface the horizontal velocity distributions of the slide the evolution of the surface elevations and the distributions of the particle velocity of the water motion three major parameters dominate the magnitude of the waves if the volume of the mud is fixed the density of mud the yield stress of the mud and the depth of water at the mudslide site because of the yield stress the slides stop on the slope when the shear stress exerted on the bottom become smaller than the yield stress the bingham plastic behavior of the mud significantly reduces the extent and the speed of the mudslide and also the magnitude of the surface waves generated comparison of the solution of the bingham plastic mudslide model with a snow flow test is presented the solution of a viscous fluid model has been derived as a special case of the present solution

the importance of extratropical and tropical cyclones on the short term evolution of barrier islands along the northern gulf of mexico usa abstract data are presented indicating the complexity and highly variable response of beaches to cold front passages along the northern gulf of mexico in addition to the impacts of tropical cyclones and winter storms within the past decade an increase in the frequency of tropical storms and hurricanes impacting the northern gulf has dramatically altered the long term equilibrium of a large portion of this coast a time series of net sediment flux for subaerial and nearshore environments has been established for a section of this coast in florida and to a lesser extent mississippi the data incorporate the morphological signature of six tropical storms hurricanes and more than 200 frontal passages data indicate that 1 barrier islands can conserve mass during catastrophic hurricanes e g hurricane opal a strong category 4 hurricane near landfall 2 less severe hurricanes and tropical storms can promote rapid dune aggradation and can contribute sediment to the entire barrier system 3 cold fronts play a critical role in the poststorm adjustment of the barrier by deflating the subaerial portion of the overwash terrace and eroding its marginal lobe along the bayside beach through locally generated high frequency steep waves and 4 barrier systems along the northern gulf do not necessarily enter an immediate poststorm recovery phase although nested in sediment rich nearshore environments while high wave energy conditions associated with cold fronts play an integral role in the evolution and maintenance of barriers along the northern gulf these events are more effective in reworking sediment after the occurrence of extreme events such as hurricanes this relationship is even more apparent during the clustering of tropical cyclones it is anticipated that these findings will have important implications for the longer term evolution of barrier systems in midlatitude microtidal settings where the clustering of storms is apparent and winter storms are significant in intensity and frequency along the coast

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

simulation of water waves generated by a potential debris avalanche in montserrat lesser antilles the evolution of the volcano activity in montserrat could lead to the collapse of a portion of the lava dome in the tar river valley and to a sudden entry of debris avalanche into the caribbean sea the impact of a debris avalanche with a volume of 40 10 6 m 3 into the sea and the generated tsunami have been simulated numerically by a mixture model solving the 3d euler s equations the mixture is composed of sediments considered as an homogeneous fluid of density 2 and of water numerical tests show that the generated waves are sensitive to both initial impact velocities and avalanche fronts of the landslide the water surface and velocities calculated by the 3d mixture model are used as input data in a non linear shallow water model to calculate tsunami propagation along the coasts of montserrat the hydraulic risks in montserrat are roughly assessed for a tsunami generated by a mass of 40 10 6 m 3 entering the sea

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

flow speed estimated by inverse modeling of sandy sediment deposited by the 29 september 2009 tsunami near satitoa east upolu samoa abstract sandy deposits from the 29 september 2009 tsunami on the east coast of upolu samoa were investigated to document their characteristics and used to apply an inverse sediment transport model to estimate tsunami flow speed sandy deposits 6 to 15 cm thick formed from 25 to 250 m inland sedimentary layers in the deposits that are defined by vertical grain size variation and contacts are interpreted to have formed during onshore runup of two waves deposits at 3 locations 100 170 and 240 m inland contained two layers that are predominately normally graded 80 but contained massive sections 15 and inversely graded sections 5 at their bases about 75 of the total thickness of normally graded intervals exhibits a signature of sediment falling out of suspension at their top this type of grading termed suspension grading here was first recognized in turbidity current deposits and is characterized by the entire distribution shifting finer upwards in a layer as high settling velocity coarser material deposits first and low settling velocity finer material deposits last the jaffe and gelfenbaum 2007 inverse sediment transport model was applied to intervals within layers that exhibited suspension grading to estimate tsunami flow speed and was able to reproduce the general trends of the observed suspension grading a key unknown input in the modeling is the bottom roughness for a bottom roughness parameterization using a manning s n of 0 03 equivalent to a z0 0 006 m for the observed flow depths of 2 3 m flow speeds calculated for the 2 layers at the 3 locations were 3 8 3 6 and 3 7 m s bottom layer earlier wave and 4 4 4 4 and 4 1 m s top layer later wave at 100 170 and 240 m inland respectively these estimates are consistent with the 3 8 m s tsunami flow speed from boulder transport calculations and result in froude numbers of 0 7 1 0 when maximum measured flow depths are used because the inverse model assumes the deposit was formed by sediment falling out of suspension care must be taken to model only intervals of the deposit exhibiting suspension grading including intervals deposited by either bedload or suspended load transport convergences result in higher and sometimes unrealistic tsunami flow speed estimates

multiple pulsed debris avalanche emplacement at mount st helens in 1980 evidence from numerical continuum flow simulations abstract the complex 1980 mount st helens debris avalanche is modeled numerically as a transient biviscous fluid flow several approaches are considered including two step rheologically distinct models for avalanche i and combined avalanches ii iii and a composite flow model consisting of retrogressive slides of identical rheology successively accreted to the main avalanche flow for the two step situation flow rheologies are evaluated separately for the initial avalanche comprising the debris avalanche block facies and an ensuing explosive influenced flow strengths normalized by density as high as 250 m2 s2 and apparent newtonian viscosities as much as 275 m2 s were established for the block facies these parameters for the explosively influenced flow are an order of magnitude lower the distribution of stratigraphic units within flowing model debris compared with field distributions suggests that the higher strength emplacement models are appropriate for debris deposited on johnston ridge and in the upper parts and flanks of the north fork toutle river valley in general models for which constant rheology is assumed throughout the flow process provide lower bound emplacement times and excessive early velocities as compared to the prototype event because model calibration is based on matching runout by trial and error it is therefore biased toward the rheologic parameters essential to achieving that runout these values characterize the flow in its latter stages whereas the actual strength and viscosity may have substantially decreased as a function of displacement two dimensional models predict debris accumulation about twice as thick as that observed at the foot of mount st helens where flow divergence was significant this discrepancy is lessened with a quasi three dimensional modification of the flow model accretionary composite flow models with homogeneous rheology simulate the overriding of early avalanche debris by later debris pulses the accretionary composite model also predicts a thick flow snout down valley since this feature is not indicated in the debris deposit the model lends support to the concept of flow separation by rheology the two step and accretionary composite flow models complement one another and provide model based support for the harry glicken hypothesis for complex emplacement at mount st helens

mechanisms to account for the longshore spacing of overwash throats on a coarse clastic barrier in southeast ireland abstract the longshore spacing of overwash throats on two contrasting sections of a coarse clastic reflective barrier beach in southeast ireland is examined for evidence of spatial periodicity a fixed barrier section carnsore with an irregular barrier top dune field exhibits random longshore throat positions related to pre existing irregularities in the seaward dune boundary a free barrier section tacumshin without a barrier top dune field shows regular longshore throat positions with a peak throat to throat periodicity of between 30 40 m similar longshore periodicity is found in persistent high level beach cusps above mhws though not always spatially in phase there is no consistent near shore rhythmic morphology that can account for this spacing the storm event which generated the tacumshin overwash appears to have dominant longer incident wave periods than normal in celtic sea storms on weight of circumstantial evidence it is reasoned that this dominant wave period range 9 11 s can be related to a zero mode sub harmonic edge wave whose longshore wavelength matches the peak periodicity of overwash spacing overwash sites on this reflective barrier may be determined by an edge wave controlled extension of run up which generates high level cusps and thereby creates washover routeways the presence or absence of a barrier top dune field is a secondary control on whether washover is successful in reaching the back barrier usually only where surge penetration and pre existing dune irregularities coincide does washover occur

large scale laboratory investigation into the effect of varying back barrier lagoon water levels on gravel beach morphology and swash zone sediment transport abstract it is generally accepted that the effect on beach morphology of the interactions between swash motion and the beach groundwater table depends on the elevation of the latter relative to that of the sea specifically a low beach groundwater table is considered to enhance onshore sediment transport and beach accretion while the reverse is thought to hold for a high beach groundwater table here we use the results of a carefully designed series of tests conducted in the delta flume the netherlands as part of the barrier dynamics experiment bardex to unequivocally demonstrate the validity of this assertion during the experiment a 4 m high and 50 m long gravel barrier d 50 11 mm was constructed within the central region of the 250 m long and 7 m deep wave flume enabling a back barrier lagoon to be located at its landward side the groundwater table in the beach was manipulated by lowering and raising the lagoon level and the gravel beach was subjected to variable wave conditions and sea lagoon levels using as the initial beach profile the morphology resulting from 90 min of wave forcing with the sea and lagoon at the same level the identical wave forcing with a low lagoon level consistently resulted in onshore sediment transport in the swash zone and beach accretion whereas the identical wave forcing with a high lagoon level consistently caused offshore sediment transport in the swash zone and beach erosion the divergent beach morphological responses for the low and high lagoon levels could not be attributed to changes in the bulk swash hydrodynamics i e based on single point velocity measurements arising from a difference in the amount of swash infiltration into the unsaturated beach instead application of a sediment transport model that accounts for the effects of in exfiltration suggested that the onshore sediment transport and beach accretion for the low lagoon tests mainly resulted from enhanced bed shear stresses during the wave uprush due to infiltration into the saturated part of the beachface due to the large hydraulic conductivity of gravel k o 0 1 m s 1 the effect of altered shear stresses due to in exfiltration may be an important factor in sediment transport in the swash zone of gravel beaches

detailed investigation of overwash on a gravel barrier abstract this paper uses results obtained from a prototype scale experiment barrier dynamics experiment bardex undertaken in the delta flume the netherlands to investigate overwash hydraulics and morphodynamics of a prototype gravel barrier gravel barrier behaviour depends upon a number of factors including sediment properties porosity permeability grain size and wave climate since overwash processes are known to control short term gravel barrier dynamics and long term barrier migration a detailed quantification of overwash flow properties and induced bed changes is crucial overwash hydrodynamics of the prototype gravel barrier focused on the flow velocity depth and discharge over the barrier crest and the overwash flow progression across and the infiltration through the barrier during the bardex experiment overwash peak depth 0 77 m velocity 5 m s 1 and discharge max 6 m 3 m 1 were high especially considering the relatively modest wave energy significant wave height 0 8 m conversely to schemes found in the literature average flow depth did not linearly decrease across the barrier rather it was characterised by a sudden decrease at the crest a milder decrease at the barrier top and then propagation as a shallow water lens over the backbarrier the barrier morphological evolution was analysed over a series of 15 min experimental runs and at the timescale of individual overwash events overall the morphological variation did not result from an accumulation of many small consistently erosive or accretionary events but rather the mean bed elevation change per event was quite large 10 mm and the overall morphology change occurred due to a small imbalance in the number of erosive and accretionary events at each location two relationships between overwash hydrodynamic variables were deduced from results 1 between overwash flow depth and velocity a power type relation was obtained and 2 a linear relation was observed between overwash flow depth and maximum overwash intrusion distance across the barrier top i e overwash intrusion findings from this study are useful to enhance the knowledge of overwash processes and also have practical applications on the one hand results shown here can be use for the validation of overwash predictive models and additionally the simple empirical relations deduced from the dataset can be used by coastal managers to estimate overwash intrusion distance which in turn can assist in the location of areas under risk of overwash and breaching

modelling of tsunami generated by the giant late bronze age eruption of thera south aegean sea greece summary tsunami generated by the late bronze age lba eruption of thera were simulated using synthetic tide records produced for selected nearshore 20 m depths sites of northern crete the cyclades islands sw turkey and sicily inundation distances inland were also calculated along northern crete modelling was performed by incorporating fully non linear boussinesq wave theory with two tsunamigenic mechanisms the first involved the entry of pyroclastic flows into the sea assuming a thick 55 m 30 km3 flow entering the sea along the south coast of thera in three different directions all directed towards northern crete then a thin pyroclastic flow 1 m 1 2 km3 entering the sea along the north coast of thera directed towards the cyclades islands flows were modelled as a solid block that slowly decelerates along a horizontal surface the second mechanism assumed caldera collapse of 19 km3 and 34 km3 modelled as a dynamic landslide producing rapid vertical displacements calculated nearshore wave amplitudes varied from a few metres to 28 m along northern crete from pyroclastic flows and up to 19 m from caldera collapse 34 km3 volume inundation distances on crete were 250 450 m waves produced by pyroclastic flows were highly focused however as a function of sea entry direction smaller volume pyroclastic flows produced nearshore wave amplitudes up to 4 m in the cyclades islands north of thera wave amplitudes in the cyclades from smaller volume caldera collapse 19 km3 were up to 24 m whereas in sw turkey were as low as 2 1 and 0 8 m didim and fethye where lba tsunami deposits have been found wave amplitudes for the larger volume caldera collapse 34 km3 were generally 2 5 3 times larger than those generated by the smaller volume collapse 19 km3 these results provide estimates for understanding possible consequences of tsunami impact in lba coastal zones thus providing criteria at archaeological sites for detecting inundation damage as well as for contemporary hazard assessment they also provide additional criteria for deciphering homogenite layers in the abyssal stratigraphy of the ionian and eastern mediterranean seas

the 2011 japan tsunami current velocity measurements from survivor videos at kesennuma bay using lidar 1 on march 11 2011 a magnitude mw 9 0 earthquake occurred off the coast of japan s tohoku region causing catastrophic damage and loss of life the tsunami flow velocity analysis focused on two survivor videos recorded from building rooftops at kesennuma bay along japan s sanriku coast a terrestrial laser scanner was deployed at the locations of the tsunami eyewitness video recordings the tsunami current velocities through the kesennuma bay are determined in a four step process the lidar point clouds are used to calibrate the camera fields of view in real world coordinates the motion of the camera during recordings was determined the video images were rectified with direct linear transformation finally a cross correlation based particle image velocimetry analysis was applied to the rectified video images to determine instantaneous tsunami flow velocity fields the measured maximum tsunami height of 9 m in the kesennuma bay narrows were followed by maximum tsunami outflow currents of 11 m s less than 10 minutes later

concepts in gravel beach dynamics abstract the dominant processes in gravel beach dynamics are reviewed highlighting some common themes which unify the various components of the gravel beach system the repercussions of which impart on how gravel beach dynamics might be understood conceptually in particular gravel beach dynamics are thought to be highly dependent on the temporal and spatial variation in grain size and the continual adjustments made by an active beach step both of which act not only as the expression of changing morphodynamic conditions but also as a controlling influence morphodynamics the notion that the exchanges on beaches between the hydrodynamics sediment transport and morphological change takes the form of reciprocal relationships which are mediated through feedback mechanisms in such a way that they cannot be thought of or studied independently is not a new one yet it appears that for the gravel beach morphodynamics must be re defined to describe conditions where variations in sediment size are thought to deserve parity rather than as merely a sequent entity or boundary condition morpho sedimentary dynamics is a phrase coined to intuit such cause and effect detailing the co evolution of morphology hydro hydraulics and sediment properties whilst acknowledging causative pluralism feedbacks and multiplier effects this is the recommended conceptual framework within which to crystallise thought and organise further research for the gravel beach essentially it increases the minimum number of parameters needed to describe the state of the gravel beach as a physical system therefore it is advised that simplicity will be most expedient in our future modelling efforts if complexity is to be adequately encapsulated

extreme inundation flows during the hokkaido nansei oki tsunami the tsunami generated by the july 12 1993 hokkaido nansei oki mw 7 8 earthquake produced in japan the worst local tsunami related death toll in fifty years with estimated 10 18m sec overland flow velocities and 30m runup these extreme values are the largest recorded in japan this century and are among the highest ever documented for non landslide generated tsunamis we model this event to confirm the estimated overland flow velocities and we find that given reasonable ground deformation data current state of the art shallow water wave models can predict tsunami inundation correctly including extreme runup current velocities and overland flow we find that even small local topographic structures affect the runup to first order and that the resolution of the bathymetric data is more important than the grid resolution our results qualitatively suggest that for this event coastal inundation is more correlated with inundation velocities than with inundation heights explaining also why threshold type modeling has substantially underpredicted coastal inundation for this and other recent events

refined numerical modeling of the 1979 tsunami in nice french riviera comparison with coastal data 1 the 16 october 1979 landslide at nice airport france produced tsunami waves observed in several harbors and the city of antibes was significantly flooded a new simulation of this event is presented in this paper to assess the sensitivity of the tsunami to the properties of the slide and to evaluate how local bathymetry and harbor resonance influence the effects of the tsunami at the coast a study of slide viscosity and water incorporation is performed using a detailed numerical model with a single initial volume of about 107 m3 the propagation of the tsunami is then simulated with a multigrid finite difference code using high resolution bathymetry in the harbors to a greater level of detail than previous studies we show that while the slide parameters are of great importance to properly model the later stages of the slide the initial volume and early dynamics of the slide are the relevant factors for determining the characteristics of the tsunami numerical results are compared with tide recordings in nice and villefranche as well as a mapping of the flood computed maximum elevation maps are compared with witness reports highlighting a focusing of the waves on antibes which explains its vulnerability this kind of focusing pattern should be considered when assessing the tsunami hazard for coastal regions calculated resonant periods in nice villefranche port vauban and la salis are matched with components present in both observed and computed waveforms most of the observed waves in nice and villefranche can be attributed to resonance

twenty five years of progress in the science of geological tsunamis following the 1992 nicaragua and flores events we review a set of 47 tsunamis of geological origin triggered by earthquakes landslides or volcanoes which have occurred over the past 25 years and provided significant new insight into theoretical experimental field or societal aspects of tsunami science among the principal developments in our command of various aspects of tsunamis we earmark the development of the w phase inversion for the low frequency moment tensor of the parent earthquake the abandonment of the concept of a maximum earthquake magnitude for a given subduction zone controlled by simple plate properties the development and implementation of computer codes simulating the interaction of tsunamis with initially dry land at beaches thus introducing a quantitative component to realistic tsunami warning procedures and the recent in situ investigation of current velocities in addition to the field of surface displacements during the interaction of tsunamis with harbors continued research remains warranted notably in the field of the real time identification of tsunami earthquakes whose tsunamis are larger than expected from their seismic magnitudes especially conventional ones the recent tragedy during the 2018 krakatau flank collapse along a scenario which had been quantitatively forecast also emphasizes the need for a continued effort in the education of the populations at risk

decadal time gaps between mafic intrusion and silicic eruption obtained from chemical zoning patterns in olivine abstract intrusion of mafic magma in a silicic crustal reservoir has been reported in numerous studies of subduction related volcanoes and is considered a main process for triggering explosive eruptions and for transferring geochemical signatures from the mantle to the crust here we determine the timescales between mafic silicic encounters and eruption by exploiting the fact that during such interactions magmas exchange crystals and their mineral compositions will strive to equilibrate to the new environmental conditions specifically we model the fe mg zoning patterns of olivine found in the dacites andesite and quenched mafic inclusions of the holocene zoned eruption of volcan san pedro 36 s chilean andes the san pedro eruption is an example where mixing between silicic and mafic magmas produced intermediate compositions e g andesite at depth in the magma reservoir for modeling the compositional profiles we took into account the anisotropy of fe mg diffusion in olivine and also the effects of diffusion in multiple dimensions aspects that have been largely neglected in previous works the retrieved timescales for olivine melt equilibration by diffusion display an array ranging from 1 year for the most silica rich dacite to 50 years for the andesite this array of timescales rather than a single value provides new insight into the details of mafic silicic mixing at depth they reveal processes that occur on a longer timescale than the days to weeks time gap for cases where the mafic intrusion triggered the eruption and they might be associated with the instances where seismic activity or significant inflation of the volcanic edifice was not immediately followed by eruption on the other hand the year to decade timescales that we report for producing magmas of intermediate composition e g andesites are much shorter than the 10 3 10 5 years inferred from u series disequilibria data for igneous differentiation by closed system fractionation to produce similar magma compositions at subduction zones

numerical modelling of tsunamis generated by hypothetical landslides in the strait of georgia british columbia a modified and corrected version of the viscous slide model of jiang and leblond 1994 is used to assess the tsunami risk associated with hypothetical underwater slope failures in two coastal areas of british columbia having potentially unstable sediment deposits a malaspina strait separating the mainland coast and texada island in the central strait of georgia and b roberts bank on the foreslope of the fraser river delta in the southern strait of georgia the intent of this study is to demonstrate the capability of the model for tsunami risk assessment and to improve upon previous studies of tsunami risk in the region based on reasonable submarine landslide scenarios the potential risk from tsunamis associated with slide failures has been examined but the likelihood of failure events themselves was not considered for the malaspina strait scenarios simulated tsunamis are generated by failure of a lobe of perched sediment situ ated on the slope of eastern texada island failure as a flow slide of the estimated 1 250 000 m3 of sediment generates wave troughs reaching 4 9 m and trough to crest heights of 6 to 8 m along the coast of texada island at cape cockburn on the opposite side of the strait wave heights of 1 5 to 2 0 m are produced for roberts bank simulated waves are examined for two separate failure scenarios the larger slide case 1 involves the failure of a sediment lobe with lateral dimensions of 7 3 km2 and volume of 0 75 km3 while the smaller slide case 2 fails a sediment lobe with dimensions of 4 2 6 km2 and volume of 0 23 km3 computations were made both for high 3 m and low 3 m tide conditions for both failure volumes maximum wave amplitudes up to 18 m for case 1 and 8 m for case 2 occur on the coasts of mayne and galiano islands opposite the source area wave amplitudes are much smaller 1 to 4 m on the mainl and coast because of the reflection of the initial waves from roberts bank additional numerical experiments were conducted for both regions to estimate the sensitivity of the computed tsunami wave heights to input parameters such as slide viscosity bulk density and slide position

processes and timescales by which a coastal gravel dominated barrier responds geomorphologically to sea level rise story head barrier nova scotia sea level rise slr is considered to be important for barrier behaviour when barriers are swash aligned and single crested which is typical of only one part of a barrier s lifeterm under such conditions gravel barrier retreat rate correlates with mesoscale sub decadal 102 a slr rate is the critical control on barrier retreat as mesoscale slr variation in combination with surge potential is able to raise water level to the elevation threshold sufficient for barrier overwash and hence drive barrier retreat

crestal overtop and washover sedimentation on a fringing sandy gravel barrier coast carnsore point southeast ireland abstract storm sedimentation on a fringing sandy gravel barrier system in southeast ireland is examined recent wave overtopping and overwashing during severe onshore storms have resulted in a distinctive pattern of crest and backbarrier sedimentation this is not easily matched with available models of washover sedimentation drawn from the barrier islands of the eastern united states beach crest overtopping occurs at heights up to 6 m mhws and is related to the development of upper beach swash ramps that are plastered against storm wave eroded dune scarps located at the barrier crest ramp sediments comprise coarse basal beach gravels overlain by coarsening upward units and finally topped by distinctive seawarddipping fine grit coarse sand couplets in places where ramps reach the dune cre t overtopping swash has deposited a fine marine gravel veneer

overwash occurrence consequent on morphodynamic changes following lagoon outlet closure on a coarse clastic barrier the reduction in sediment volume of an ebb tide delta as a consequence of lagoon outlet closure on a coarse clastic barrier in southeast ireland initiated a sequence of beachface and barrier changes downdrift elimination of sediment supply to the ebb delta caused a cessation of downdrift longshore swash bar welding and led to beach volume reductions which in turn allowed a temporal sequence of beach and nearshore morphodynamic domains to develop these domains then controlled the sedimentation regime of the barrier adjacent to the old outlet a temporal sequence of a dissipative barrier b reflective barrier and c inner reflective barrier face outer dissipative subtidal wave regimes match respectively periods of a barrier crest build up by crestal dune development b barrier crest instability barrier width increasing barrier height decreasing due to rhythmic overwash and c a return to barrier crest stability with limited aeolian accretion two barriers at different stages in this sequence are discussed

short term morphodynamics of non storm overwash abstract overwash is an important process in barrier island evolution and its effects on the barrier morphology and sedimentology have been widely studied however the short term sediment dynamics of overwash processes are not well known due to the lack of specific field studies this paper presents field data that clarify the sedimentary dynamics of overwash processes on different washover morphologies and determine the factors leading to non storm overwash occurrence two fieldwork campaigns were undertaken during overwash events go 1 winter of 2001 and go 3 winter of 2003 on western barreta island algarve portugal the fieldwork included measurements of oceanographic conditions overwash flows morphology variations mixing depth and sediment transport paths using tracers the sediment dynamics induced by overwash varied according to the washover morphology washover plain versus washover lobe the sediment transport inside the washover plain was different for the two fieldwork campaigns average mixing depth of 13 cm for go 1 and 6 cm for go 3 however it had similar main stages stage 1 crest accretion stage 2 onshore transport and stage 3 dynamic equilibrium the sediment transport inside the washover lobe can be characterised by one onshore flow stage with erosion of the mouth and channel and accretion on the washover fan the main factors governing the occurrence of non storm overwash in the study area were the combined occurrence of 1 typical winter waves 2 spring high tides 3 washover crest below the high tide level 2 m and 4 absence of prominent beach berm this study proved that when the proper conditions are generated non storm overwash has sediment transport comparable to storm overwash and therefore may be significant for barrier evolution further field studies of overwash are needed principally for more detailed overwash flow velocity measurements high frequency morphologic surveys and barrier groundwater measurements

overwash threshold for gravel barriers abstract this paper uses results obtained from the large scale bardex experiments undertaken in the delta flume to investigate the morphological response of a prototype gravel barrier to wave and tidal forcing during overwash conditions gravel barrier behaviour depends upon a number of factors such as sediment properties porosity permeability grainsize geological setting and wave climate since overwash processes are known to control short term gravel barrier dynamics and long term barrier migration the development of a robust quantitative method to define the critical conditions leading to gravel barrier overwashing is important both for scientific and practical management purposes it is known that when wave runup exceeds the barrier crest elevation three outcomes are possible 1 insignificant morphological change when wave runup just overtops the barrier crest and flow velocities are very weak 2 overtopping resulting in accretion on the barrier crest region and barrier stabilisation and 3 overwashing resulting in erosion lowering of the crest region and ultimately to barrier inundation this study provides an insight into the critical conditions that distinguish these two possible outcomes and to the different mechanisms that provide the required positive and negative feedbacks to the sediment dynamics in order to define the overwash threshold condition and to predict the morphological outcome of particular overwash events use is made here of the overwash potential op defined as the difference between the wave runup and the barrier crest elevation to make effective use of op it is necessary to identify a reliable runup predictor following tests using 12 runup equations the stockdon et al stockdon h f holman r a howd p a sallenger a h 2006 empirical parameterization of setup swash and runup coast eng 53 573 588 approach has been identified as the best predictor of runup conditions necessary to generate positive values of op with overtopping and overwashing predicted to occur for average op values of 0 2 m and 0 5 m respectively the use of op values provides a practical means by which to identify potential coastal hazards associated with gravel barrier overwash processes and is considered to have a range of practical coastal management applications

numerical modeling of the 1995 chilean tsunami impact on french polynesia on the 30th july 1995 an earthquake with magnitude of 8 1 occurred off the coast of chile the associated tsunami propagated across the pacific ocean and reached french polynesia 10 hours after the seismic event with maximum run up heights of about 2 5 meters the most affected islands in french polynesia were the marquesas islands that present few outer reefs more gradual bottom slopes and large bays the tsunami propagation has been modeled from chile to polynesian islands solving the shallow water equations the water surface initialisation has been computed from okada s formulas using seismic parameters of ruegg 1996 the tsunami propagation is simulated by a finite difference numerical model using a system of multiple grids with different grid sizes the computed waves are in fair agreement with the recorded waves along the chilean coasts in tahiti and in nuku hiva the numerical results obtained in the marquesas islands confirm the observations of numerous eyewitnesses

unique and remarkable dilatometer measurements of pyroclastic flow generated tsunamis pyroclastic flows entering the sea may cause tsunamis at coastal volcanoes worldwide but geophysically monitored field occurrences are rare we document the process of tsunami generation during a prolonged gigantic collapse of the soufriere hills volcano lava dome on montserrat on 12 13 july 2003 tsunamis were initiated by large volume pyroclastic flows entering the ocean we reconstruct the collapse from seismic records and report unique and remarkable borehole dilatometer observations which recorded clearly the passage of wave packets at periods of 250 500 s over several hours strain signals are consistent in period and amplitude with water loading from passing tsunamis each wave packet can be correlated with individual pyroclastic flow packages recorded by seismic data proving that multiple tsunamis were initiated by pyroclastic flows any volcano within a few kilometers of water and capable of generating hot pyroclastic flows or cold debris flows with volumes greater than 5 10 6 m 3 may generate significant and possibly damaging tsunamis during future eruptions

organisational controls typologies and time scales of paraglacial gravel dominated coastal systems abstract the fundamental controls on the initiation and development of gravel dominated deposits beaches and barriers on paraglacial coasts are particle size and shape sediment supply storm wave activity primarily runup relative sea level rsl change and terrestrial basement structure primarily as it affects accommodation space this paper examines the stochastic basis for barrier organisation as shown by variation in gravel barrier architecture we recognise punctuated self organisation of barrier development that is disrupted by short phases of barrier instability the latter results from positive feedback causing barrier breakdown when sediment supply is exhausted we examine published typologies for gravel barriers and advocate a consolidated perspective using rate of rsl change and sediment supply we also consider the temporal variation in controls on barrier development these are examined in terms of a simple behavioural model barch for prograding gravel barrier architecture and its sensitivity to such controls the nature of macroscale 10 2 10 3 years gravel barrier development including inherited characteristics that influence barrier genesis as well as forcing from changing rsl sediment supply headland control and barrier inertia is examined in the context of long surviving barriers along the southern england coastline

numerical modelling of a landslide generated tsunami the 1979 nice event on the 16th of october 1979 a part of the nice new harbour extension close to the nice international airport french riviera slumped into the mediterranean sea during landfilling operations a submarine slide with initial volume close to seashore of about 10 millions m3 which could have evolved later into an avalanche was followed by a small tsunami noticed by several witnesses in the baie des anges the maximum tsunami effects were observed 10 km from the slide location near antibes city which was inundated previous analyses used rough approximate methods and produced models which did not conveniently fit data in this paper both the slide and the generated water waves are numerically simulated on the basis of the shallow water approximation the landslide is assimilated to a heavy newtonian homogeneous fluid downslope under gravity water waves are generated by sea bottom displacements induced by the landslide taking into account a very accurate multibeam bathymetric map the nice slide of 10 millions m3 is simulated by this model the numerical results are generally consistent with the observed hydraulic local effects in front of the nice airport however they are not in agreement in the far field a larger and deeper landslide 2 km off nice airport is tested to quantitatively study the effects of the landslide volume on water waves generation

tsunamigenic sea floor deformations in addition to the primary damage they do earthquakes can cause tsunamis massive ocean swells that can inundate coastal regions in their perspective synolakis et al describe results presented at a workshop on the interface between seismology and tsunami hydrodynamics held in santa monica in may 1997 the authors discuss the highlights of the meeting and summarize future directions for research

validation of volume continuity method for estimation of cross shore swash flow velocity the use of flow volume continuity to estimate depth averaged cross shore swash flow velocity is validated using appropriate field data swash surface and beach face elevation were measured by a network of ultrasonic altimeters mounted through the swash zone of a sandy beach estimates of cross shore flow velocity derived from these data compare well with concurrent measurements obtained from a vertical array of four electromagnetic current meters emcms significantly the continuity technique allows swash velocity to be estimated throughout the full swash cycle this is not possible using fixed current meters and the new measurements indicate that swash velocity is more negatively skewed than previously observed

physical processes and sedimentary record of a modern transgressive lacustrine barrier island abstract high water levels storms and a sparse sand supply have led to the formation and episodic migration of this 30 km wide foredune lacking lacustrine barrier transgression is dominated by overwash and by channels cut during storms that transport sand to the lagoon the barrier system is characterized by five environments near shore foreshore backshore washover terrace channel and lagoon the nearshore consists of irregular bars that overlie a holocene peat and or clay the bars are characterized by low angle stratification and ripples and landward dipping tabular sets the foreshore consists of a smooth plane surface and internally by lakeward dipping 3 to 12 laminations that truncate one another and thin towards the berm the backshore washover terrace consists of a gently 1 to 2 landward dipping surface that changes at the lagoon margin to a steeply 30 landward dipping surface stratification consists of subhorizontal landward dipping laminations and thin beds that are thinnest nearer the berm and gradually thicken toward the lagoon and by avalanche foresets washover fans coalesce to form the terrace the channels which are commonly less than a few tens of meters wide and a meter deep form during storms when wave energy is concentrated by refraction around nearshore bars the channel facies consists of nearly horizontal beds and laminations of gravel and coarse sand the lagoon consists of mud that overlies a holocene peat the lagoonal mud is eroded during transgression the vertical sequence which is 1 2 m thick consists from the base up of horizontal laminations of coarse sand and gravel of the channel facies the landward dipping foresets of the washover fan margin and the gently landward dipping laminations and landward dipping avalanche foresets of the backshore washover terrace the preservation potential is considered low although pleistocene and holocene coastal deposits have survived for up to 15 000 years in the great lakes region

overwash and aeolian processes on a u s northeast coast barrier abstract a field investigation of overwash aeolian processes and vegetative response was undertaken to obtain the first quantitative data of this kind for the new england area the new england blizzard of 1978 february 6 7 resulted in massive overwashing of nauset spit cape cod massachusetts volumetric determinations showed that as much as 400 m3 of overwash sand per meter of dune breach was transported across the barrier during this event with deposition thicknesses of 1 65 m above the living salt marsh although considerable amounts of sand were deposited by overwash much of this sediment was redistributed through aeolian processes during interstorm periods approximately half the sediment deposited by the 1978 northeaster was blown back to the beach by offshore winds and an equal amount accumulated in the peripheral dunes at distinct fan features large barren washover flats can remain unvegetated for long periods of time where the substrate is continually affected by overwash and aeolian transport these areas eventually become the loci of new major barrier dunes through the revegetation process initiated by drift line deposits