micro seismic measurements of cliff motion under wave impact and implications for the development of near horizontal shore platforms abstract few high resolution measurements of process form interactions have been taken on rock coasts but recent studies in california have shown that portable seismometers enable useful proxy measurements of wave energy delivery to cliffs here we describe measurements over 20 days of high frequency ground motion of cliffs formed in sedimentary flysch rocks at okakari point north of auckland new zealand three sensors were located in a shore normal array inland from the cliff top and a fourth sensor was bolted to a ledge 2 m above the cliff toe the nearshore wave field in front of the cliff and shore platform was monitored using a shore normal array of 5 wave gauges the instrumentation provided measurements of wave energy delivery and consequent ground motion including the first observations of motion at the top and bottom of cliffs results showed that horizontal ground motion is dominant at the cliff top whereas vertical motion is dominant at the cliff toe power spectra show that several high frequency peaks occur in data from the cliff toe whereas a single broader peak frequency occurs at the cliff top resulting from signal modification as seismic waves pass through tens of metres of cliff rock a 100 m wide shore platform at the cliff toe fundamentally controls the patterns of observed energy delivery the shore platform is nearly horizontal elevated close to high water level and abruptly plunges into water 10 m deep at its seaward edge as expected the magnitude of ground motion at all sensors is greatest during larger waves measurements further show that ground motion both at the bottom and top of the cliff is strongest at low tide and weakest at high tide this observation is opposite to that noted at santa cruz where ground motion was greatest at high tide at okakari point the most significant high frequency ground motions occur at low tide when waves are forced to break sometimes violently against the seaward edge of the shore platform four distinctive frequency peaks between 1 and 50 hz increase in magnitude as tidal stage drops implying that wave breaking against the outside edge of the shore platform represents an important source of vibration a detailed understanding of the energy source e g short duration shock pressures and rock resonance is not provided by this study however quantifying the spatial and temporal patterns of energy delivery places strong emphasis on the important role of shore platform geometry in filtering wave energy delivery to the cliff during the 20 day experiment most wave energy was delivered to the outside edge of the shore platform not the cliff toe the geomorphic role of high frequency shaking from wave impacts remains to be clearly demonstrated but if wave impacts are capable of eroding rock then the data from this study imply that under present conditions the outside edge of the shore platform may be subject to higher erosion rates than the cliff toe it is possible that the shore platform is currently being destroyed rather than created but a longer programme of measurements is required to test this notion

surface mass balance of small glaciers on james ross island north eastern antarctic peninsula during 2009 2015 two small glaciers on james ross island the north eastern antarctic peninsula experienced surface mass gain between 2009 and 2015 as revealed by field measurements a positive cumulative surface mass balance of 0 57 0 67 and 0 11 0 37 m w e was observed during the 2009 2015 period on whisky glacier and davies dome respectively the results indicate a change from surface mass loss that prevailed in the region during the first decade of the 21st century to predominantly positive surface mass balance after 2009 10 the spatial pattern of annual surface mass balance distribution implies snow redistribution by wind on both glaciers the mean equilibrium line altitudes for whisky glacier 311 16 m a s l and davies dome 393 18 m a s l are in accordance with the regional data indicating 200 300 m higher equilibrium line on james ross and vega islands compared with the south shetland islands the mean accumulation area ratio of 0 68 0 09 and 0 44 0 09 determined for whisky glacier and davies dome respectively is similar to the value reported for vega island and within the range of typical values for high latitude glaciers

a methodology for the study of the relation between coastal cliff erosion and the mechanical strength of soils and rock masses abstract a methodology is proposed to make approximate estimates of the destructive force of waves at the bottoms of cliffs where no accurate bathymetric data are available by means of correlation between the erosion rate of rocky coasts and the mechanical strength of soils and rock masses the correlation used makes it possible to obtain a linear semi logarithmic expression between the long term average erosion rate from an engineering standpoint of coasts consisting of different lithologies wave energy and the uniaxial compressive strength of soils and rock masses forming the cliffs the uniaxial compressive strength of soils consisting of landslide debris was measured using a pocket penetrometer and the rock mass index rmi method was used for rock masses these methods were chosen after critical analysis of the methodologies currently available the proposed approach was tested in the cilento area of southern italy and in particular along a 6 km stretch of coast typified by rock masses and landslide debris that are particularly susceptible to erosion this coastline is exposed to south westerly waves which in deep water reach significant heights between 1 and 3 m and significant wave periods between 4 and 7 s estimates of the coastal erosion rates were made by studying the variations especially in restricted headland areas occurring over two time spans 30 and 45 years respectively by comparing topographic maps and aerial photographs taken at different times these comparisons give approximate indications of retreats of 15 m over the time span of 30 years average erosion rate of 0 5 m year 1 and of 35 m over the time span of 45 years average erosion rate of ca 0 8 m year 1 these data do have a local significance but clearly show how quick these processes sometimes are lastly the study of a notch incised by wave action on a concrete sea wall built to protect a terrace made it possible to quantify the impact of erosion on concrete it was possible to obtain rmi values through field observations furthermore it was possible to obtain the constants of the hoek and brown failure criterion using rmi on the basis of rmi values the rock masses studied were defined as moderately strong to strong and according to the hoek and brown criterion as poor to fair a semilogarithmic linear relation was found between the strength of landslide debris rock masses and concrete as well as their respective long term erosion consequently a rough estimate of the destructive force of waves ca 24 mpa was calculated this value is given by the product of the mean value of their hydraulic pressure for a non dimensional constant which in turn takes into account the sandy pebbly beach sediment at the foot of the cliffs that acts as an abrasive on the rock mass

microseismic measurement of wave energy delivery to a rocky coast rocky coasts are attacked by waves that drive sea cliff retreat and etch promontories and embayments into the coastline understanding the evolution of such coastlines requires knowledge of the energy supplied by waves which should depend upon both the deep water waves and the coastal bathymetry they cross we employ microseismic measurements of the wave induced shaking of sea cliffs near santa cruz california as a proxy for the temporal pattern of wave energy delivery to the coast during much of the winter 2001 storm season visual inspection of the time series suggests that both deep water wave heights and tide levels exert considerable control on the energy delivered we test this concept quantitatively with two models in which synthetic time series of wave power at the coast are compared with the shaking data in the first model deep water wave power is linearly scaled by a fitting parameter because this model fails to account for the strong tidal signal it fits poorly in the second model the wave transformation associated with shoaling and refraction diminishes the nearshore wave power and dissipation associated with bottom drag and wave breaking is parameterized by exponential dependencies on two length scales this model reduces the variance by 32 45 and captures the essence of the full signal shoaling and refraction greatly modulate the wave power delivered to the coast energy dissipated by bottom drag across the shelf is relatively small the dissipation length scale is many times the path length across the shelf in contrast much energy is dissipated in the surf zone the tidal dissipation depth scale is of the same order as the tidal range 1 2 m which accounts for the strong dependence of the cliff shaking on the tide

lithological anomalies in a relict coastal dune geophysical and paleoenvironmental markers 1 ground exposures of migration surfaces slipfaces of a relict holocene coastal dune along the southeastern baltic sea coast provide an ideal opportunity for establishing the causes of prominent reflections on geophysical profiles high amplitude reflections on high resolution ground penetrating radar gpr images correlate well with two major lithological anomalies 1 paleosols developed on dune slipfaces and 2 slipfaces consisting of heavy mineral concentrations hmcs paleosols serve as indicators of dune stability represent datable chronostratigraphic surfaces and help reconstruct dune paleo morphology hmcs have substantially higher magnetic susceptibility values than background quartz rich sands and where they are well developed can be also used for spatial correlation based on their occurrence at the study site these enriched horizons likely represent periods of increased wind activity storminess multiple hmcs upwind of paleosol p1 800 670 cal years bp likely reflect periods of intensified wind activity along the southeast baltic region during the medieval warm period

processes of selective grain transport and the formation of placers on beaches placers are found on many beaches of the oregon coast in the beach that is the focus of this study the principal placer minerals are ilmenite 22 0 epidote 20 0 garnet 18 7 augite 15 5 hypersthene 8 1 hornblende 5 8 and zircon 2 0 the ilmenite fraction actually being partly chromite a series of beach face sand samples was obtained along a profile when sand was being eroded from the upper beach and transported to offshore bars since the processes of grain selective sorting leading to placer formation were probably most active at such a time the landward most sample contained 96 heavy minerals being part of the placer this concentration systematically decreased offshore to a 6 heavy mineral content in the seaward most sample 54 m offshore determinations of individual heavy mineral concentrations revealed that although they all tended to become concentrated within the placer with light quartz and feldspar dominating the offshore transport the sorting processes were m

sea cliff erosion as a function of beach changes and extreme wave runup during the 1997 1998 el nino abstract over time scales of hundreds to thousands of years the net longshore sand transport direction along the central california coast has been driven to the south by north pacific winter swell in contrast during the el nino winter of 1997 1998 comparisons of before and after airborne lidar surveys showed sand was transported from south to north and accumulated on the south sides of resistant headlands bordering pocket beaches this resulted in significant beach erosion at the south ends of pocket beaches and deposition in the north ends coincident with the south to north redistribution of sand shoreline morphology became prominently cuspate with longshore wavelengths of 400 700 m the width and elevation of beaches were least where maximum shoreline erosion occurred preferentially exposing cliffs to wave attack the resulting erosional hotspots typically were located in the embayments of giant cusps in the southern end of the pocket beaches the observed magnitude of sea cliff retreat which reached 14 m varied with the number of hours that extreme wave runup exceeded certain thresholds representing the protective capacity of the beach during the el nino winter a threshold representing the width of the beach performed better than a threshold representing the elevation of the beach the magnitude of cliff erosion can be scaled using a simple model based on the cross shore distance that extreme wave runup exceeded the pre winter cliff position cliff erosion appears to be a balance between terrestrial mass wasting processes which tend to decrease the cliff slope and wave attack which removes debris and erodes the cliff base increasing the cliff slope

the temporal and spatial scales of rocky coast geomorphology a commentary rocky shores are complex landforms that result from marine erosion and subaerial weathering they are time integrated features where their present day form is the result of instantaneous erosion often on the millimetre to sub metre scale occurring for centuries to millennia as a result research on rocky coasts focuses on a range of temporal and spatial scales from granular scale swelling of a rock surface and instantaneous wave impact to modelling millennial scale sea level drivers the challenge for rocky coast researchers is either to upscale or to downscale their results to the human timescales of greatest interest to managers the research presented in earth surface processes and landforms over the past 3 years highlights the range of spatial and temporal approaches to the study of coastal cliffs and shore platforms we identify a key temporal and spatial gap in current research seasonal annual timeframes over hundreds of metres to kilometre scale studies appear to be lacking and are likely critical in understanding the future evolution of rocky coasts especially their response to climate change copyright 2017 john wiley sons ltd

ground motions on rocky cliffed and sandy shorelines generated by ocean waves 1 we compare ground motions observed within about 100 m of the waterline on eight sites located on shorelines with different morphologies rock slope cliff and sand beaches at all sites local ocean waves generated ground motions in the frequency band 0 01 40 hz between about 0 01 and 0 1 hz foreshore loading and gravitational attraction from ocean swell and infragravity waves drive coherent in phase ground flexing motions mostly oriented cross shore that decay inland at higher frequencies between 0 5 and 40 hz breaking ocean waves and wave rock impacts cause ground shaking overall seismic spectral shapes were generally consistent across shoreline sites and usually within a few orders of magnitude despite the diverse range of settings however specific site response varied and was influenced by a combination of tide level incident wave energy site morphology ground composition and signal decay flexing and shaking increased with incident wave energy and was often tidally modulated consistent with a local generation source flexing magnitudes were usually larger than shaking and flexing displacements of several mm were observed during relatively large incident wave conditions hs 4 5 m comparison with traffic noise and earthquakes illustrate the relative significance of local ocean generated signals in coastal seismic data seismic observations are not a simple proxy for wave cliff interaction

observations on a debris covered polar glacier whisky glacier james ross island antarctic peninsula antarctica on etudie la structure d un glacier polaire dans lequel des couches de debris atteignent la surface pour generer une aire tres vaste de glace couverte de debris

decadal scale coastal cliff retreat in southern and central california abstract airborne lidar data collected in 1998 and 2009 2010 were used to measure coastal cliff erosion and retreat between the mexico california border and bodega head california cliff erosion was detected along 44 of the 595 km of shoreline evaluated while the remaining cliffs were relatively stable the mean cliff top retreat rate was 0 12 m yr while mean retreat averaged over the entire cliff face was 0 04 m yr the maximum cliff top and face retreat rates were 4 2 and 3 8 m yr respectively historical 1930s to 1998 and recent retreat rates were significantly inversely correlated for areas with large historical or recent cliff retreat such that locations with elevated historical retreat had low levels of recent retreat and locations with elevated recent retreat were preceded by low rates of historical retreat the strength of this inverse correlation increased with cliff change magnitudes up to r2 of 0 91 for cliff top retreat rates 2 9 m yr mean recent retreat rates were 52 83 lower than mean historical retreat rates although beaches can protect cliffs against wave driven erosion cliffs fronted by beaches retreated 49 more than cliffs without beaches on average unarmored cliff faces retreated 0 05 m yr between 1998 and 2009 2010 about three times faster than artificially armored cliffs alongshore metrics of wave cliff impact precipitation and cliff hardness were generally not well correlated with recent cliff changes a cliff hazard metric is used to detect cliff steepening and areas prone to future cliff top failures

alongshore variability in wave energy transfer to coastal cliffs abstract the alongshore distribution of wave energy is believed to be an important control on the spatial variability of coastal erosion there is however a lack of field data quantifying the alongshore variability in wave energy on rock coasts whereby the relative control of coastline geometry versus foreshore characteristics on wave energy delivery remains unclear a number of studies have identified high frequency cliff top ground shaking to be generated by wave impacts at the cliff toe during high tides ht to capture the variability of wave cliff impact energy along coast we installed an array of cliff top seismometers along a 1 km stretch of coastline in north yorkshire uk our aim is to constrain how wave energy transfer to the cliff toe varies and to examine the relative energy transfer around typical coastline features including a bay and headlands whilst the greatest ht ground motion energy is recorded at a headland and the lowest at the centre of the bay 5 of that observed at the headland we identify no systematic alongshore variation in the ht ground motion energy that can be related to coastline morphology we also note considerable variation between features of similar form the total ht ground motion energy at one headland is only 49 of the next headland 1 km alongshore between neighbouring sites within the bay separated by only 100 m we observe up to an order of magnitude difference in ground motion energy transfer our results demonstrate the importance of the foreshore in driving the variations in energy delivery that we observe local alterations in water depth and foreshore topography control the alongshore distribution of wave energy available to generate cliff ht ground motions importantly this apparently local effect overrides the influence of macroscale coastal planform morphology which has previously been assumed to be the dominant control the results show that foreshore characteristics that hold influence over wave energy transfer vary significantly over short 100 m distances and so we expect erosion controlled by wave impacts to vary over similar scales

an analytical model to predict dune erosion due to wave impact an analytical model is developed to calculate recession distance and eroded volume for coastal dunes during severe storms the transport relationship used in the model is based on wave impact theory where individual swash waves hitting the dune face induce the erosion combining this relationship with the sediment volume conservation equation describes the response of the dune to high waves and water levels four different data sets on dune erosion originating from the laboratory and the field were employed to validate the model and to determine the value of an empirical transport coefficient appearing in the analytical solutions the time evolution of dune recession observed in the different data sets was well described by the model but the empirical coefficient showed some variation between cases especially for the field data in practical applications of the model it is recommended to use a range of coefficient values to include an uncertainty estimate of calculated quantities such as recession distance and eroded volume

nearshore erosion on a cohesive shoreline abstract a study to measure vertical erosion of till in the inner nearshore was carried out along a stretch of shoreline just west of port dalhousie on the south shore of lake ontario canada in addition to measuring the rate of vertical erosion an attempt was made to determine the influence of thickness and mobility of the surficial sediment cover and of softening of the till on erosion bluffs at the site are 4 5 m in height and developed almost entirely in till beach width at the time of the study ranged from 0 3 m and the toe of the bluff was actively undercut during periods of high waves till outcrops in the nearshore close to the shoreline and again beyond 100 m but considerable quantities of sand and gravel exist in the zone between forming a distinct nearshore bar located 40 60 m offshore elevation surficial sediment thickness and size and characteristics of the till surface were determined along 7 lines spaced 20 m apart vertical erosion was measured with a micro erosion meter at stations spaced 10 m apart a total of 16 stations was established along 3 lines to a maximum distance offshore of 120 m some erosion was measured in each time period with cumulative erosion during the period may to october 1992 being on the order of 3 4 cm erosion in any time period increased with increasing cumulative wave energy softening of the till surface was observed in many localities and appears to be an important factor that increases the erosion potential particularly lakeward of the nearshore bar where the till is always exposed erosion appears to be reduced where there is protection by surficial sediments but it is necessary to determine that the cover is maintained during high wave conditions the annual rate of vertical lowering determined from these measurements is of the same order as predicted from longterm bluff recession rates assuming maintenance of an equilibrium profile

patterns of erosion sedimentation heavy mineral concentration and grain size to interpret boundaries of littoral sub cells of the nile delta egypt abstract analyses have been undertaken of 68 beach nearshore profiles spanning the years 1971 1995 to interpret sub littoral cells of the nile delta that developed during cross shore and alongshore sediment transport bottom sediments of these profiles taken along the 240 km length of the delta coastline have been analyzed to determine seabed level changes textural and heavy mineral concentration distributions the spatial distribution of seabed depth changes linked with the heavy mineral concentration allows identification of three zones of erosion source areas associated with accretion sink areas erosion zones occur off the nile promontories at rosetta 20 to 50 cm yr burullus and damietta 0 to 20 cm yr accretion ranging from 0 to 40 cm yr occurs between erosion zones at abu quir bay the rosetta saddle gamasa embayments and along the western side of the jetty at the suez canal entrance port said this pattern was generally induced from the temporal variability in the direction and intensity of the incoming waves currents orientation of coastline seafloor morphology and local protective structures the correspondence among patterns of seabed depth change heavy mineral concentration and to some extent the texture of seabed sediments refine boundaries of littoral sub cells of the nile including sediment paths sources sinks nodal points and zones of sediment transport convergence and divergence this correspondence is not strongly correlated as might be expected in this deltaic system where sediment has been recycled between recent and relict seabed settings moving in the alongshore and cross shore directions nevertheless the present investigation shows that the relationship between seabed level changes heavy mineral concentration and to some extent mean grain size of the littoral zone can be practically applied in other deltaic settings to interpret sediment transport pathways particularly where there are less relict sediments

the subtidal morphology of microtidal shore platforms and its implication for wave dynamics on rocky coasts abstract the subtidal portions of shore platforms are important geomorphic features as they can modify deep water wave energy before it impacts the intertidal platform edge in this study an integrated marine and terrestrial aerial lidar dataset is used to analyse the morphology of the subtidal portion of shore platforms semi horizontal intertidal platforms on an 85 km along stretch of microtidal open ocean rocky coast in victoria australia are investigated and described quantitatively three distinct types of subtidal morphology occur i a steep cliff with a mean slope of 8 18 ii a gently sloping ramp with a mean slope of

modeling the development of wave cut shore platforms abstract a mathematical model was used to investigate the development of wave cut shore platforms with constant sea level the model considered the effects of deep water wave height spectra period and wavelength breaker height and depth breaker type the width and bottom roughness of the surf zone the gradient of the submarine slope an erosional threshold related to the strength of the rocks the number of hours each year in which the water level is at each intertidal elevation and the amount and persistence of the debris at the cliff foot intertidal erosion rates were calculated according to the force of the surf reaching the shoreline whereas submarine erosion rates were determined using a depth decay variable each of the two hundred and fifty model runs consisted of 300 000 iterations platform width increased and gradient progressively decreased through model runs and states of static equilibrium were attained by the end of one hundred and nine runs when the wave induced force at each point in the intertidal zone had became too weak to continue eroding the rock runs with mesotidal spring tidal range 3 m generally produced subhorizontal platforms with cliff platform junctions at the mean low water neap tidal level a greater variety of profiles was produced in runs with macrotidal spring tidal ranges 9 m although almost 30 of these runs produced gently sloping platforms with average gradients of only 0 3 about two thirds of the simulated profiles had average gradients ranging from about 1 to 3 simulated platform width increased with tidal range and decreased with the rate of submarine erosion rock resistance the roughness or irregularity of the platform surface the amount and persistence of the cliff foot debris and wave period because higher waves break in deeper water than lower waves there was no consistent relationship between simulated platform width and wave height

assimilating coastal wave observations in regional swell predictions part i inverse methods abstract inverse methods are used to assimilate wave observations into numerical predictions of ocean swell 0 04 0 12 hz surface waves propagating over complex continental shelf bathymetry model predictions of swell on the shelf can be degraded by the limited accuracy and resolution of the initializing offshore unsheltered deep water frequency directional spectra so usually derived from buoy measurements or meteorological hindcasts the authors use a spectral refraction wave propagation model to find improved estimates of so that are consistent with both unsheltered and sheltered altered by coastal bathymetry observations and vary smoothly in direction and time in part i linear and nonlinear inverse assimilation methods are developed their potential and limitations are illustrated qualitatively using a scenario where no a priori knowledge of so is used in the inverse estimates inverse estimates of so based solely on sheltered wave data routinely collected in the southern california bight are

quantitative provenance analysis of sediments review and outlook provenance analysis of sediments is aimed at reconstructing the parent rock assemblages of sediments and the climaticphysiographic conditions under which sediments formed inferring sediment provenance from the final product a basin fill is anything but straightforward because the detrital spectrum evolves as the sediment is transported along the pathway from source to basin successful provenance analysis requires that the nature and extent of compositional and textural modifications to the detrital spectrum be recognised if not quantified the history of quantification in sediment provenance studies is summarised and illustrated by tracking two fundamental ideas the concept of the sediment petrological province or petrofacies and the relation between sandstone composition and plate tectonic environment progress in sedimentary provenance analysis has been closely linked with advancements in measurement technology a brief survey of modern data acquisition tools illustrates the possibilities and limitations of modern provenance research an operational definition of quantitative provenance analysis qpa is presented in which the central role of mass balance is acknowledged extension of this definition to include quantitative predictions obtained by forward modelling computer simulation of sediment production as well as methodological improvements in data acquisition and processing is needed to cover likely future developments in qpa the contributions to the special issue quantitative provenance analysis of sediments illustrate the intrinsic multidisciplinarity and rapid expansion of qpa d 2004 elsevier b v all rights reserved

a predictive model for wave induced cliff erosion with application to pacific coasts of japan a model for predicting the rate of short term bluff recession originally derived from wave tank experiments is tested under field conditions the fundamental equation is dx dt k c ln gh sc where dx dt is the recession rate h is the wave height at the cliff base sc is the compressive strength of the cliff forming material is the density of water g is the acceleration due to gravity c is a nondimensional constant and k is a constant with units of lt 1 the critical wave height to initiate erosion hcrit is given by hcrit sce c g this model is applied to two eroding tertiary cliffs in japan both facing the pacific ocean results show that 1 the larger but rarer waves only cause cliff erosion compared with the smaller but more common waves and 2 the erosion rate at each site is greatly affected by the occurrence frequency of waves higher than hcrit

probability distributions for wave runup on beaches measured probability distributions of shoreline elevation swash height shoreline excursion length and swash maxima and minima from a wide range of beach types are compared to theoretical probability distributions the theoretical distributions are based on assumptions that the time series are weakly steady state ergodic and a linear sum of random variables despite the swash process being inherently non linear results indicate that these assumptions are not overly restrictive with respect to modeling exceedence statistics in the upper tail of the probability distribution the rms errors for a range of exceedence level statistics 50 10 5 2 and 1 were restricted to 10 cm and often 5 cm for all of the swash variables that were investigated the results presented here provide the basis for further refinement of coastal inundation modeling as well as stochastic type morphodynamic modeling of beach response to waves further work is required however to relate the parameters of swash probability distributions to wave conditions further offshore c 2010 elsevier b v all rights reserved

seismic precursory patterns before a cliff collapse and critical point phenomena 1 we analyse the statistical pattern of seismicity before a 1 2 103 m3 chalk cliff collapse on the normandie ocean shore western france we show that a power law acceleration of seismicity rate and energy in both 40 hz 1 5 khz and 2 hz 10khz frequency range is defined on 3 orders of magnitude within 2 hours from the collapse time simultaneously the average size of the seismic events increases toward the time to failure these in situ results are derived from the only station located within one rupture length distance from the rock fall rupture plane they mimic the critical point like behavior recovered from physical and numerical experiments before brittle failures and tertiary creep failures our analysis of this first seismic monitoring data of a cliff collapse suggests that the thermodynamic phase transition models for failure may apply for cliff collapse

a new process response coastal recession model of soft rock cliffs abstract the development of cliff erosion predictive models is limited by the complex interactions between environmental processes and material properties over a range of temporal and spatial scales current models incorporate a stochastic representation of cliff behavior based on assumptions regarding the magnitude and frequency of events in a probabilistic framework the new model presented here has been developed to incorporate the behavioral and mechanical characteristics of coastal cliffs which are dominated geologically by overconsolidated clays tills and an associated protective colluvial wedge this model is capable of providing precise and stable responses to some of the inherent uncertainties in cliff recession processes including those caused by different failure mechanisms e g colluvium generation groundwater and erosive tidal cycles material strength is incorporated using the unconfined compressive strength of the material that composes the cliff unlike previous models a calibration parameter is restricted to account for uncertainties linked to marine processes the mechanisms of cliffline retreat have been identified as slump and topple landslides once cliff material has fallen colluvium formation at the cliff foot is incorporated into the model using three different procedures according to the geomechanical characteristics of the debris the model is validated through profile evolution assessment at various locations of coastline retreat on the holderness coast uk higher groundwater content also produces an increase in the number and size of the slope failures the results represent an important step forward in linking material properties to the processes of cliff recession

spatial variations in heavy minerals and patterns of sediment sorting along the nile delta egypt abstract sand samples were collected along 34 beach profiles spanning the 240 km length of the nile delta in order to examine the sorting patterns of heavy minerals that develop during cross shore and alongshore sediment transport factor analysis of the heavy mineral contents shows that two mineral factors or groups result from sorting due to the contrasting densities and sizes of the grains one factor is dominated by augite hornblende and epidote while the second factor consists of opaques garnet zircon rutile and monazite minerals of factor 1 are of lower densities and coarser sizes and represent the grains that are selectively entrained by waves and currents in areas of beach erosion and preferentially transported to zones of beach accretion where they are deposited the higher density minerals of factor 2 tend to become concentrated in areas of beach erosion accounting for the formation of black sand placers where the erosion has been greatest the spatial distributions of these two factors reflect the grain sorting patterns of the heavy minerals which coincide with the general trends of shoreline erosion versus accretion that exist along the length of the delta there is also a distinctive pattern of cross shore sorting with factor 2 containing the denser minerals being best developed within the inner surf zone generally with a maximum at the shoreline its development corresponds to the formation of black sand concentrates on the beach face where erosion has been greatest implying that grain sorting has taken place mainly within the swash zone there is a general decrease in factor 2 relative to factor 1 toward the offshore often with oscillations that are congruent with the beach topography factor 1 with the lower density minerals is greatest over offshore bars where deposition has prevailed

coastal knickpoints and the competition between fluvial and wave driven erosion on rocky coastlines abstract active margin coastlines are distinguished by rock erosion that acts in two different directions waves erode the coast horizontally or landwards a process that creates sea cliffs and rivers and streams erode the landscape vertically via channel incision the relative rates of each process exert a dominant control on coastline morphology using a model of river channel incision and sea cliff retreat we explore how terrestrial and marine erosion compete to shape coastal topography and specifically what conditions encourage the development of coastal knickpoints i e a river or stream channels that end at a raised sea cliff edge we then compare results to actual landscapes model results and observations show that coastal knickpoint development is strongly dependent on drainage basin area where knickpoints typically occur in drainage basins smaller than 5 105 6 106 m2 as well as channel geometry and sea cliff retreat rate in our study area coastal knickpoints with persistent flow waterfalls are uncommon and form only within a small morphological window when 1 drainage basin area is large enough to sustain steady stream discharge but not large enough to out compete sea cliff formation 2 sea cliff retreat is rapid and 3 channel concavity is low so that channel slopes at the coast are high this particular geomorphic combination can sustain sea cliff formation even when streams tap into larger drainage basins with greater discharge and more stream power and provides an initial explanation of why persistent coastal waterfalls are along many coastlines relatively rare features

chemical composition of ice containing tephra layers in the byrd station ice core antarctica abstract the chemical composition of ice containing tephra volcanic ash layers in 22 sections of the byrd station ice core was examined to determine if the volcanic eruptions affected the chemical composition of the atmosphere and precipitation in the vicinity of byrd station the liquid conductivity acidity sulfate nitrate aluminum and sodium concentrations of ice samples deposited before during and after the deposition of the tephra layers were analyzed ice samples that contain tephra layers have on average about two times more sulfate and three to four times more aluminum than nonvolcanic ice samples the acidity of ice samples associated with tephra layers is lowered by hydrolysis of silicate glass and minerals average nitrate sodium and conductivity are the same in all samples because much of the sulfur and chlorine originally associated with these eruptions may have been scavenged by ash particles the atmospheric residence time of these volatiles would have been minimized therefore the eruptions probably had only a small effect on the composition of the antarctic atmosphere and a negligible effect on local or global climate

an alternative approach to the identification of net sediment transport paths based on grain size trends abstract progressive changes in grain size parameters have long been linked to net sediment transport paths however the methods employed to date suffer from limitations potentially leading to serious interpretational errors which necessitate the formulation of an integrated quantitative technique the approach advocated here is a step in this direction as it eliminates some of the problems inherent in the older methods previously trend vectors were obtained by comparing the grain size parameters of only two sampling stations at a time which gives a low probability of identifying the actual transport direction in the proposed method groups of five stations comprising a central station and four satellite stations are used for each trend vector grain size parameters are first combined in such a way that bias towards any one of them is climated the resultant dimensionless numbers are then substituted for the proportional frequencies of recorded directions in conventional vector analysis the satellite stations must be located equally far from the central station on radials 90 from each other which is seldom the case an iterative trigometric technique is therefore employed to determine the combined grain size parameters at these localities conventional vector analysis adapted to the situation of using four raials instead of 10 sectors allows the calculation of a vector mean azimuth and vector magnitude

coastal cliff ground motions from local ocean swell and infragravity waves in southern california 1 ground motions atop a southern california usa coastal cliff are compared with water level fluctuations observed at the cliff base and with ground motions observed 10 km inland at high tide cliff top ground motions in three frequency bands were generated locally by ocean waves at the cliff base 1 high frequency 0 3 hz shaking caused by waves impacting the cliff and 2 gravitational loading induced swaying at the frequency of the incident sea swell waves 0 05 0 1 hz and 3 slow swaying at infragravity frequencies 0 006 0 05 hz at high tide at infragravity and incident sea swell wave frequencies cliff top vertical ground displacement and cliff base water level fluctuations are coherent and oscillate in phase with occasional deviation at sea swell frequencies and spectral levels at the cliff top are much higher than at the inland seismometer in contrast at double frequencies 0 1 0 3 hz spectral levels of vertical motions are nearly identical inland and at the cliff top consistent with a common distant or spatially distributed source at low tide when ocean waves did not reach the cliff base power levels of vertical ground motions at the cliff top decreased to inland levels at incident wave frequencies and higher and only infragravity band motions were noticeably forced by local ocean waves

long term shoreline changes and the concentration of heavy minerals in beach sands of the nile delta egypt abstract analyses have been undertaken of shoreline positions established from beach profile surveys at 65 positions along the coastline of the nile delta spanning the years 1971 to 1990 the analyses identify long term linear trends as well as any cycles in the horizontal movement of shoreline positions the results reveal longshore patterns wherein erosion along a stretch of coast gives way to accretion in an adjacent stretch defining a subcell within the overall littoral system of the delta the rate of shoreline retreat has been greatest along the rosetta promontory 106 m yr and damietta promontory 10 4 m yr significant erosion has also occurred along the central bulge of the delta coast but at a lesser rate 6 5 m yr areas of accretion exist within the saddles or embayments between the promontories with the maximum shoreline advance averaging about 13 m yr the identified patterns of erosion versus accretion along the delta reflect the natural processes of wave induced longshore currents and sediment transport associated with this longshore sediment movement is a selective transport of different minerals according to their densities and grain sizes with the light minerals quartz and feldspar having the highest advection rates and the dense opaque minerals the lowest rates tending to remain behind as a lag within the erosion areas as a result of this longshore grain sorting paralleling the patterns of shoreline erosion versus accretion there are correlations between the rates of shoreline change and the heavy mineral contents and mean grain sizes of the beach sediments these large scale delta wide patterns are affected somewhat by local shoreline changes and mineral variations induced by the construction of jetties or shoreline protection structures

magnetic mineral transport and sorting in the swash zone northern lake erie canada a combined field and laboratory study in northern lake erie has provided new insights into the origin and dynamics of heavy mineral placer deposits on beaches consisting primarily of non magnetic sediment work was conducted on the cross shore and longshore transport of heavy magnetic minerals using magnetic susceptibility and fluorescent paints to trace the movement in the field of samples of magnetic magnetite and non magnetic quartz and calcite grains respectively laboratory experiments examined how the burial of small dense magnetic minerals is affected by the grain size of the non magnetic host material and how grain burial affects magnetic susceptibility measurements at the surface the field experiments demonstrated that the magnetic mineral tracers were buried rapidly beneath coarser non magnetic grains under low to moderate wave conditions and subsequently were unable to move in the longshore or cross shore directions the laboratory experiments showed that the magnetic susceptibility rapidly decreased with the rate and depth of burial of the magnetic minerals and that magnetic grain burial was most effective beneath coarser rather than finer non magnetic sand and for the latter sediments under less rather than more energetic conditions the results imply that magnetic mineral concentrations develop in this area through magnetic grain burial under fairly mild conditions and subsequent settling exposure and concentration in the upper swash zone during more energetic periods when the non magnetic grains are eroded it is probably during these erosional periods when the magnetic minerals are exposed in fairly homogeneous deposits that longshore and cross shore transport takes place

isotopic diffusion in cold snow and firn molecular mixing in cold snow and firn is ordinarily controlled by vapor diffusion diffusion through or along the ice matrix is slow whereas diffusion from the air to within separate grains is comparatively rapid thus mixing occurs in the vapor phase and exchange with the local ice involves all the water molecules a quantification of these concepts is applied to the diffusion of oxygen isotopic depth profiles in southern greenland and at dome c antarctica it successfully describes the smoothing of measured profiles the smoothing rate is strongly dependent on temperature and density of the firn

the role of beach morphology on coastal cliff erosion under extreme waves erosion of hard rock coastal cliffs is understood to be caused by a combination of both marine and sub aerial processes beach morphology tidal elevation and significant wave heights especially under extreme storm conditions can lead to variability in wave energy flux to the cliff toe wave and water level measurements in the nearshore under energetic conditions are difficult to obtain and in situ observations are rare here we use monthly cliff face volume changes detected using terrestrial laser scanning alongside beach morphological changes and modelled nearshore hydrodynamics to examine how exposed cliffs respond to changes in extreme wave conditions and beach morphology the measurements cover the north atlantic storms of 2013 2014 and consider two exposed stretches of coastline porthleven and godrevy uk with contrasting beach morphology fronting the cliffs a flat dissipative sandy beach at godrevy and a steep reflective gravel beach at porthleven beach slope and the elevation of the beach cliff junction were found to influence the frequency of cliff inundation and the power of wave cliff impacts numerical modelling xbeach g showed that under highly energetic wave conditions i e those that occurred in the north atlantic during winter 2013 2014 with hs 5 5 m dissipative site and 8 m reflective site the combination of greater wave height and steeper beach at the reflective site led to amplified wave run up subjecting these cliffs to waves over 4 times as powerful as those impacting the cliffs at the dissipative site 39 kwm 1 compared with 9 kwm 1 this study highlighted the sensitivity of cliff erosion to extreme wave conditions where the majority over 90 of the annual value of cliff face erosion ensued during the winter the significance of these short term erosion rates in the context of long term retreat illustrates the importance of incorporating short term beach and wave dynamics into geomorphological studies of coastal cliff change

modelling the response of soft cliffs to climate change a statistical process response model using accumulated excess energy abstract cliff retreat poses a threat to coastal communities worldwide in soft cliff environments coastal retreat may occur at rapid rates the environmental significance of soft cliff environments coupled with the societal impacts of cliff retreat means that it is important to understand the processes and timings of soft cliff erosion here a new statistical process response model of soft cliff erosion is proposed based on the premise that wave energy delivered to the cliff toe is the key parameter forcing erosion more specifically and in contrast to prior studies that have sought to link erosion rates to indices of peak wave energy we postulate that the accumulated excess wave energy aee the time integrated total wave energy above an erosion threshold is the key hydraulic control on soft cliff erosion the new model is calibrated to two uk sites with contrasting atlantic versus north sea wave energy regimes before downscaled hadcm3 global climate model outputs are used to assess how future next 100 year changes in sea level and wave height affect retreat rates at the two study sites we show that the aee model accounts for between 46 and 89 of the variance in observed coastal erosion representing an improvement over prior models that use measures only of peak wave energy the aee model suggests increases of between 0 5 m a 1 92 and 0 3 m a 1 33 in mean erosion rate by 2100 for sites in the atlantic and north sea respectively furthermore it is shown that at both sites extreme events exceeding the 95th percentile value are projected to become three to four times more likely under scenarios of future climate change highlighting a need to understand and predict the extreme response of coastal cliff systems to changes in climate

decadal timescale links between antarctic peninsula ice core oxygen 18 deuterium and temperature the antarctic peninsula region has exprienced a long term warming trend over the twentieth century with the 1971 90 mean at faraday being 1 9 c warmer than the mean over 1903 41 based on expedition reports for the period prior to 1900 there is conflicting evidence from different data sources an initial interpretation of isotopic data from ice cores suggests that the nineteenth century was warmer than the twentieth century in contrast snow accumulation rate data for the nineteenth century from the same ice cores suggest lower temperatures here we investigate these facts by studying the links between atmospheric temperature over the antarctic peninsula circulation parameters and isotopic data over the period of instrumental records we show that the relationships between these variables are complex and highly spatially variable in particular the correlations between temperature and 18o and d are generally of the order r 0 5 or less on timescales of one to five years conflicts between evidenc

coastal cliff ground motions and response to extreme storm waves coastal cliff erosion from storm waves is observed worldwide but the processes are notoriously difficult to measure during extreme storm wave conditions when most erosion normally occurs limiting our understanding of cliff processes over january february 2014 during the largest atlantic storms in at least 60 years with deepwater significant wave heights of 6 8 m cliff top ground motions showed vertical ground displacements in excess of 50 100 m an order of magnitude larger than observations made previously repeat terrestrial laser scanner surveys over a 2 week period encompassing the extreme storms gave a cliff face volume loss of 2 orders of magnitude larger than the long term erosion rate the results imply that erosion of coastal cliffs exposed to extreme storm waves is highly episodic and that long term rates of cliff erosion will depend on the frequency and severity of extreme storm wave impacts

grain size and heavy mineral distribution as related to hinterland and environmental conditions for modern beach sediments from the gulfs of antalya and finike eastern mediterranean abstract backshore sediment samples from 22 beaches along the antalya and finike gulfs have been studied for their grain size chemical and heavy mineral composition data presented here suggest that well to moderately sorted 0 41 0 92 medium sand 1 2 represents dominant mean grain size in most beaches in contrast some beaches from the western part of the gulf of antalya goynuk kemer kiris and beldibi are composed of pebble to boulder size grained beaches which are located close to mouths of short and steep gradient ephemeral rivers entering the sea from the western taurus mountains the heavy mineral assemblages are dominated by detrital opaque minerals 14 58 magnetite chromite and hematite pyroxene 8 65 augite amphibole 3 15 tremolite and actinolite epidote 3 25 garnet 2 9 pyrope and almandine and micas 3 20 biotite muscovite and chlorite the very high concentrations of heavy minerals up to 86 of bulk sediment together with the significant concentrations of some elements found in beach sediments from the gulf of finike and western gulf of antalya fe 18 40 cr 10 00 and ti 1 32 are indicative of ultramafic origin mainly derived from the ophiolitic rocks of the antalya tekirova nappe on coastal hinterland

breaking wave loads at vertical seawalls and breakwaters this paper presents recent advances in knowledge on wave loads based on experimental work carried out in the ciem lim large flume at barcelona within the framework of the vows violent overtopping by waves at seawalls project both quasi static and impact wave forces from the new data set have been compared with predictions by empirical and analytical methods the scatter in impact forces has been found to be large over the whole range of measurements with no existing method giving especially good predictions based on general considerations a simple and intuitive set of prediction formulae has been introduced for quasi static and impact forces and overturning moments giving good agreement with the new measurements new prediction formulae have been compared with previous measurements from physical model tests at small and large scale giving satisfactory results over a relatively wide range of test conditions the time variation of wave impacts is discussed together with pressure distribution up the wall which shows that within experimental limitations the measured pressures are within existing limits of previous study

assessment of dispersive pressure as a beach placer mechanism the concept of sediment sorting extending from the bagnold constitutive relationship for sediment under shear is examined in the context of beach placer formation the traditional interpretation of shear sorting is found to be inconsistent with data from new granular flow experiments a binary mixture satisfying the shear equivalence relationship displayed pronounced segregation during shear this observation is contrary to shear sorting as applied in the literature where no such segregation for this pairing of mineral species is expected further experiments minimizing the potential of grain percolation of smaller grains or kinetic sieving also demonstrated sorting patterns inconsistent with the existing shear sorting interpretation consequently the shear sorting process as currently formulated may not be an appropriate means to describe beach placer formation kinetic sieving appears to be a more likely mechanism in this context enhanced by the shearing and dilation of the granular fluid flow 2009 the authors journal compilation 2009 international association of sedimentologists

directional spreading of waves in the nearshore observations of surface gravity waves shoaling between 8 m water depth and the shoreline on a barred beach indicate that breaking results in an increase in the directional spread of wave energy in contrast to the directional narrowing with decreasing depth predicted by refraction theory snell s law during low energy wave conditions when breaking induced wave energy losses over the instrumented transect are small the observed mean propagation direction and spread about the mean both decrease with decreasing depth consistent with the expected effects of refraction nonlinearity causes high frequency components of the spectrum to become directionally aligned with the dominant incident waves during high energy wave conditions with significant wave breaking on the sand bar the observed mean directions still decrease with decreasing depth however the observed directional spreads increase sharply nominally a factor of 2 for values integrated over the swell sea frequency range between the outer edge of the surf zone and the crest of the sand bar followed by a decrease toward the shoreline observations on a nonbarred beach also show directional broadening with spreads increasing monotonically from the outer edge of the surf zone to a maximum value near the shoreline although the mechanism is not understood these spatial patterns of directional broadening suggest that wave breaking causes significant scattering of incident wave energy into obliquely propagating components

observing calving generated ocean waves with coastal broadband seismometers jakobshavn isbrae greenland we use time lapse photography modis satellite imagery ocean wave measurements and regional broadband seismic data to demonstrate that icebergs that calve from jakobshavn isbrae greenland can generate ocean waves that are detectable over 150 km from their source the waves which are recorded seismically have distinct spectral peaks are not dispersive and persist for several hours on the basis of these observations we suggest that calving events at jakobshavn isbrae can stimulate seiches or basin eigenmodes in both ilulissat icefjord and disko bay our observations furthermore indicate that coastal land based seismometers located near calving termini e g as part of the new greenland ice sheet monitoring network glisn can aid investigations into the largely unexplored oceanographic consequences of iceberg calving

coastal cliff top ground motions as proxies for environmental processes 1 a two year dataset of coastal cliff microseismic ground motions is used to explore energy transfer to a cliff the long term dataset enables us to characterise cliff motion responses to a wide range of environmental processes and examine whether short term characteristics are representative of the long term we examine whether cliff top motions are reliable proxies for environmental processes to inform future investigations into the drivers of erosion the study is based at an actively eroding macrotidal hard rock cliffed coast where considerable intra annual variability in wave tide and storm conditions permit the examination of a full range of environmental permutations three frequency bands of ground motion are identified that represent wind and wave processes that transfer energy to the cliff examining mean energy transfer by aggregating the frequency bands by sea water elevation reveals a notable departure from tidal inundation duration alone of relevance to understanding the timing duration and intensity of effective processes of erosion peak energy transfer to the cliff face occurs during the largest storms where water levels significantly exceed those of tidal inundation rather than at locations most frequently inundated by tides we anticipate it is therefore these conditions that are likely to be most effective in eroding hard rock coasts rather than periods which accrue energy transfer associated with still or calm waters and hence tidally modulated inundation may not relate well to coastal erosion promisingly despite signal overlap and noise cliff top motions can be used as proxies for the processes that transfer energy to the coast

foredune morphological changes and beach recovery from the extreme 2013 2014 winter at a high energy sandy coast the beach dune response at truc vert sw france is analysed using dgps topographic surveys sampled every 2 4 weeks covering an alongshore distance of 1 5 km combined with wave tide and extreme water level hindcast and beach dune photographs during the 2013 2014 winter which was the most energetic since at least 1948 the beach dune system at truc vert eroded by approximately 180 m3 per beach width divided equally between beach and dune erosion beach and dune erosion was strongly variable alongshore with cuspate type rhythmic dune erosion scarps stripped of vegetation with a cross shore amplitude of 25 m the alongshore variable scarps were coupled with an alongshore variability in elevation of the beach with lower beach levels co located with the megacusp bays the following 10 months showed modest morphological beach and dune changes with for instance destabilisation of the scarped dune by trough blowouts scarp slumping and filling and seasonal beach berm dynamics the most profound morphological and vegetation changes occurred during the subsequent 10 months only 1 5 years after that winter the beach dune system at truc vert almost recovered to its pre winter volume but not to its pre winter foredune profile most of the sand volume recovery occurred during spring summer autumn 2015 when approximately 120 m3 m of sand naturally came back in the system the beach volume recovery rate was relatively steady and uncorrelated with wave conditions with rates twice as large across the megacusp bay profile as across the that of the megacusp horns during that period the widened and risen dry beach provided large fetch length enhancing onshore windblown transport and a rapid rising of the backshore the slumped and filled dune scarp which was providing a high barrier to aeolian transport from the beach to the dune since the 2013 2014 winter reformed as a dune ramp providing efficient conduit for beach dune delivery exchange of sediment by the end of the study this process favoured both natural revegetation into the scarp and incipient foredune formation despite the reinstatement of natural processes between the beach and the dune the dune foot was still located landward by more than 10 m on average with respect to its pre 2013 2014 winter position this study shows that even after the most severe winter over the last 68 years in terms of average wave energy arriving at the coast beach recovery can be a relatively fast process along high energy sandy beaches backed by large dunes in contrast foredune recovery which timing and magnitude can provide a proxy measure for the resilience of the system to climatic variability and change is a much slower process that can take years to decades

a comparison of two spectral wave models in the southern california bight abstract two models a spectral refraction model longuet higgins and a parabolic equation method pem refraction diffraction model kirby are used to simulate the propagation of surface gravity waves across the southern california bight the bight contains numerous offshore islands and shoals and is significantly larger 300 km by 300 km than regions typically studied with these models the effects of complex bathymetry on the transformation of incident wave directional spectra s0 f 0 which are very narrow in both frequency and direction are difficult to model accurately as s0 f 0 becomes broader in both dimensions agreement between the models improves and the spectra predicted at coastal sites become less sensitive to errors in the bathymetry grid to tidal changes in the mean water depth and to uncertainty in s0 f 0 itself the smoothing associated with even relatively narrow 0 01 hz 5 bandwidth s0 f 0 is usually sufficient to bring the model predictions of shallow water energy into at least qualitative agreement however neither model is accurate at highly sheltered sites the importance of diffraction degrades the predictions of the refraction model and a positive bias o 10 of the deep ocean energy in the refraction diffraction model estimates believed to stem from numerical noise kirby may be comparable to the low wave energy the best agreement between the predicted spectra generally occurs at moderately exposed locations in deeper waters within the bight away from shallow water diffractive effects and in the far field of the islands in these cases the differences between the models are small comparable to the errors caused by tidal fluctuations in water depth as waves propagate across the bight the accuracy of predicted energies at these sites is likely to be limited by the uncertainty in specifying s0 f 0

nearshore wave induced cyclical flexing of sea cliffs 1 evolution of a tectonically active coast is driven by geomorphically destructive energy supplied by ocean waves wave energy is episodic and concentrated sea cliffs are battered by the geomorphic wrecking ball every 4 25 s we measure the response of sea cliffs to wave assault by sensing the ground motion using near coastal seismometers sea cliffs respond to waves in two distinct styles high frequency motion 20 hz reflects the natural frequency of the sea cliff as it rings in response to direct wave impact low frequency motion in the 0 1 0 05 hz 10 20 s band consistently agrees with the dominant nearshore wave period integrating microseismic velocities suggests 50 m and 10 m displacements in horizontal and vertical directions respectively displacement ellipsoids exhibit simultaneous downward and seaward sea cliff motion with each wave video footage corroborates the downward sea cliff flex in response to the imposed water load on the wave cut platform gradients in displacement amplitudes documented using multiple seismometers suggest longitudinal and shear strain of the flexing sea cliff on the order of 0 5 4 strains during each wave loading cycle as this sea cliff flexure occurs approximately 3 million times annually it has the potential to fatigue the rock through cyclical loading local sea cliff retreat rates of 10 cm yr imply that a given parcel of rock is flexed through roughly 109 cycles of increasing amplitude before exposure to direct wave attack at the cliff face

rain waves and short term evolution of composite seacliffs in southern california abstract a four year time series of nine airborne lidar surveys were used to assess the roles of wave attack and rainfall on the erosion of 42 km of southern california seacliffs nine continuous seacliff sections separated by coastal lagoon mouths all show maximum seacliff erosion in the rainiest time period when wave energy was not particularly elevated and in most sections the squared correlations between rainfall and erosion time series exceeded 0 8 although rain and associated subaerial mechanisms such as groundwater seepage triggered most of the observed seacliff failures wave attack accelerated seacliff erosion with erosion rates of cliffs exposed to wave attack five times higher than at adjacent cliffs not exposed to waves the results demonstrate the importance of both waves and rain in the erosion of southern california seacliffs and suggest that the combined influences of marine and subaerial processes accelerate the erosion rate through positive feedbacks

systematic analysis of rocky shore platform morphology at large spatial scale using lidar derived digital elevation models abstract much of the existing research on rocky shore platforms describes results from carefully selected field sites or comparisons between a relatively small number of selected sites here we describe a method to systematically analyse rocky shore morphology over a large area using lidar derived digital elevation models the method was applied to 700 km of coastline in southwest england a region where there is considerable variation in wave climate and lithological settings and a large alongshore variation in tidal range across shore profiles were automatically extracted at 50 m intervals around the coast where information was available from the coastal channel observatory coastal classification routines were developed to automatically remove non platform profiles the remaining 612 shore platform profiles were then subject to automated morphometric analyses and correlation analysis in respect to three possible environmental controls wave height mean spring tidal range and rock strength as expected considerable scatter exists in the correlation analysis because only very coarse estimates of rock strength and wave height were applied whereas variability in factors such as these can locally be the most important control on shoreline morphology in view of this it is somewhat surprising that overall consistency was found between previous published findings and the results from the systematic automated analysis of lidar data platform gradient increases as rock strength and tidal range increase but decreases as wave height increases platform width increases as wave height and tidal range increase but decreases as rock strength increases previous studies have predicted shore platform gradient using tidal range alone a multi regression analysis of lidar data confirms that tidal range is the strongest predictor but a new multi factor empirical model considering tidal range wave height and rock strength yields better predictions of shore platform gradient root mean square error of predictions reduced by 5 the key finding of this study is that large scale semi automated morphometric analyses have the potential to reveal dominant process controls in the face of small scale local variability

heavy mineral analysis for assessing the provenance of sandy sediment in the san francisco bay coastal system abstract heavy or high specific gravity minerals make up a small but diagnostic component of sediment that is well suited for determining the provenance and distribution of sediment transported through estuarine and coastal systems worldwide by this means we see that surficial sand sized sediment in the san francisco bay coastal system comes primarily from the sierra nevada and associated terranes by way of the sacramento and san joaquin rivers and is transported with little dilution through the san francisco bay and out the golden gate heavy minerals document a slight change from the strictly sierran sacramento mineralogy at the confluence of the two rivers to a composition that includes minor amounts of chert and other franciscan complex components west of carquinez strait between carquinez strait and the san francisco bar sierran sediment is intermingled with franciscan modified sierran sediment the latter continues out the gate and turns southward towards beaches of the san francisco peninsula the sierran sediment also fans out from the san francisco bar to merge with a sierran province on the shelf in the gulf of the farallones beach sand sized sediment from the russian river is transported southward to point reyes where it spreads out to define a franciscan sediment province on the shelf but does not continue southward to contribute to the sediment in the golden gate area

provenance of silt and clay within sandy deposits of the lithuanian coastal zone baltic sea abstract mineralogical analysis of the silt and clay fraction of sandy deposits of 37 surface samples and grain size data are used to interpret sediment sources acting in the se baltic sea along the lithuanian coast mineralogical composition was determined using x ray diffraction xrd methods grain size distribution was obtained by standard dry sieving and pipette techniques for identification of sources we combined known compositional information of possible sources with logical models for mineral combinations related to regional geological provinces and processes supported by results of correlation and factor principal component analyses between minerals grain size parameters and bathymetric features of the area the main sources supplying sediment into the area are 1 the sambian peninsula to the south 2 the nemunas river whose discharge passes through the curonian lagoon and 3 late pleistocene till erosion on the sea floor in the north and at the olando kepure shore cliffs the general pattern of spatial distribution related to the identified sources for the fine grained sediment fraction is interpreted as a shore parallel transport of suspended matter flowing northwards in the southeastern part of the baltic sea

snow chemistry on james ross island antarctic peninsula more than 400 firn samples were collected at an altitude of 1660 m on the small ice sheet covering james ross island northeastern coast of the antarctic peninsula chemical analysis of these samples provides information about the marine background aerosol composition in the area the samples cover the years 1975 1979 pit samples and the last 15 years firn core samples major impurities na k ca al h so4 and no3 were determined by using flameless atomic absorption neutron activation acid titration or ion chromatography aerosols are contributed mainly by the surrounding ocean however secondary aerosol deposition h2so4 and hno3 is also important all samples were found to be slightly acidic ph generally in the range 5 6 strong seasonal variations maximum values in summer are found in the h2so4 deposition a photochemical mechanism is proposed to explain the local production of h2so4 from gaseous marine sulfur compounds from these results a yearly deposition of 0 13 tg of h2so4 is calculated for the entire antarctic continent

spatial patterns in heavy mineral concentrations along the curonian spit coast southeastern baltic sea abstract the 98 km long curonian spit is fronted by beaches mainly composed of quartz sand with minor high density fractions in this study heavy mineral concentration hmc trends and grain size statistical parameters were used to assess their role as indicators of natural processes human activities and patterns of longshore transport a total of 92 surface sand samples were collected at 1 km intervals from the middle of the beach along the baltic sea shoreline of the spit between klaip da strait in lithuania and zelenogradsk in russia hmc contribution was assessed in the laboratory using bulk low field magnetic susceptibility ms as a proxy for ferrimagnetic and paramagnetic mineral content quartz dominated background sand is generally characterized by low ms values of 150 si are typical for heavy mineral rich sand the greatest ms values along the middle of the beach occur in the southern part of the spit and are 40 times higher than in the northern sector this pattern suggests the existence of a longshore particle flux with hmc distribution having the potential as a useful tracer of longshore sediment transport local anomalously high ms excursions are associated with contribution of iron rich materials from adjacent man made structures therefore temporally constrained hmc distribution along the middle of the beach reflects the cumulative effect of antecedent geologic framework longshore sediment transfer erosional and accretionary processes wave and wind climate and local coastal protective structures

development of shore platforms on kaikoura peninsula south island new zealand abstract the role of waves in shore platform development has been investigated on kaikoura peninsula by direct measurement of waves in deep water and on platforms at high tide this showed that the deepwater wave environment off the kaikoura peninsula is very energetic but the amount of energy delivered to platforms is very low in deep water wave power ranged from 5900 to 106 700 n m s 1 per m of crest when calculated from mean significant wave height and when calculated from maximum wave height it ranged from 31 400 to 5 370 000 n m s 1 per m of crest a comparison of deep water wave energy flux with wave energy flux at the high tide cliff of platforms showed that there was a reduction by as much as five orders of magnitude during storm conditions an analysis of the role of breaking waves revealed that these are ineffective as an erosional agent because the depth of water offshore causes breaking before waves arrive on platform surfaces depth of water controlling wave breaking causes larger storm waves to break further from shore preventing direct attack at the cliff base shear stresses and dynamic forces under waves were calculated from waves measured on shore platforms this showed that these forces never exceeded the compressive strength of the platform rocks at kaikoura it is concluded that wave forces are not directly capable of causing erosion on shore platforms at kaikoura

the morphodynamics of shore platforms in a micro tidal setting interactions between waves and morphology abstract the interactions between waves and morphology on shore platforms were investigated at four platforms located at kaikoura peninsula new zealand and the otway coast victoria australia waves were measured over six tidal peaks of a spring tidal sequence at each site during a six month period february 2007 july 2007 this paper reports the results of an investigation into the research question how are waves modified by platform morphology in a micro tidal setting through the investigation of wave interactions on shore platforms it was found that complex hydrodynamic patterns formed on the shore platforms studied through direct measurement of waves on the platforms it was found that wave attenuation was not dependent on platform width but rather influenced by platform gradient and depth of water on the platform spectral analysis was used to assess how wave energy was transformed across the platforms at three of the four platforms investigated energy gradients formed across the platform with wave energy recorded within the infragravity range

cross shore decay of cliff top ground motions driven by local ocean swell and infragravity waves 1 ground motions at the frequencies between 0 01 and 0 1 hz of ocean infragravity and swell waves were observed on a cross shore transect extending landward from the edge of a southern california coastal cliff cliff top ground motions are coherent and in phase with water level fluctuations at the cliff base vertical ground motions at infragravity and single frequencies decay rapidly with inland distance from the cliff edge e folding scale is about 12 m and at the edge decrease by several orders of magnitude between high tide when waves reach the cliff base and low tide when the waterline is about 50 m from the cliff base the observed cross shore decay scales are qualitatively consistent with gravitational loading and attraction of water waves at tidally modulated distances from the cliff base at approximately constant distance from the waterline ground motions vary roughly linearly with nearshore swell wave energy in contrast to these locally forced ground motions double frequency band 0 1 0 2 hz cliff top vertical ground motions are remotely generated with spatially uniform magnitudes approximately equal to those observed 14 km inland near the cliff edge ground tilt dominates the observed large relative to vertical cross shore acceleration at infragravity frequencies contributes significantly to cross shore acceleration at swell frequencies and is a small fraction of cross shore acceleration at higher frequencies

differential transport of fall equivalent sand grains lake ontario new york abstract fractions composed of grains having uniform fall velocity equivalent to 2 quartz were extracted from beach sands collected along the eastern end of lake ontario new york heavy liquid separations and point counts were performed on these fall equivalent velocity splits to obtain relative abundances of hornblende augite hypersthene garnet magnetite and quartz density lights heavy minerals decrease in abundance in the direction of transport and the degree to which any particular mineral lags behind another lighter mineral is a simple function of the mineral s effective density ratio our results appear to confirm that heavy minerals are less transportable than fall equivalent lights an effect that may result from differential entrainability transport within different zones of the beach or both

the unsteady nature of sea cliff retreat due to mechanical abrasion failure and comminution feedbacks sea cliff retreat is often linked to large waves heavy precipitation and seismic events but the specific operative mechanics have not been well constrained in particular what is the role of mechanical abrasion by beach sediments in cliff platform evolution and how does it relate to the episodic nature of cliff retreat observed at certain locations here we present a simple numerical model of sea cliff retreat that incorporates mechanical abrasion of a basal notch threshold controlled failure of the cantilevered block and a feedback mechanism wherein retreat is dependent on the rate of sediment comminution within the surf zone using shore platform and cliff characteristics found in two coastal settings the central california coast and the english north sea coast the model produces retreat rates comparable to those observed via field measurements the highest retreat rates coincide with the steepest shore platforms and increasing wave height steeper platforms promote wave access to the cliff toe and correspondingly the receding cliff face produces additional accommodation space for the platform beach preserving the erosive efficacy of the beach sediments when exposed to energetic wave forcing the slope of the inner platform segment controls retreat rates for concave platforms whereas the slope of the outer platform segment exerts greater control for convex platforms platform beaches approached a long term dynamic equilibrium on the concave profiles leading to more consistent and steady retreat platform beaches were ephemeral on convex profiles mirroring observed sand wave ord migration on the holderness coast uk these findings agree with previous field observations and support mechanical abrasion as a viable cause of temporal heterogeneity in cliff retreat rate for both coastlines

where is the seaward edge a review and definition of shore platform morphology abstract shore platforms are erosional coastal landforms that have attracted scientific attention since the mid 19th century the defining element of a platform is width that is used in many calculations such as determining a platform s evolutionary state or inferring how wave energy is distributed along the shore although a critical variable there are no uniform criteria for defining the seaward edge quantification of platform width has been driven by site specific variables with the seaward edge defined on the basis of tides morphology biology processes and sediment coverage the lack of a uniform definition has meant that comparative studies are difficult and results are possibly spurious as widths derived from very different criteria can vary by an order of magnitude just on the basis of which criteria is used to determine its edge in this review a combination of morphologic and process elements is used to define the seaward edge of a shore platform the development of strict criteria is especially needed in an environment of rising sea levels if measurements of landscape change are to be made in addition the advent of seamless datasets that cross the land sea boundary means that the delineation of platform morphology is no longer limited by physical access this review concludes that the seaward edge of a shore platform will occur at or landward of wave base and should be defined as the point where active erosion of the bedrock ceases characterised by erosional features such as notches and block plucking scars or the deposition of sediment of such a thickness that the underlying bedrock is not exposed during storm events

processes of coastal bluff erosion in weakly lithified sands pacifica california usa abstract coastal bluff erosion and landsliding are currently the major geomorphic processes sculpting much of the marine terrace dominated coastline of northern california in this study we identify the spatial and temporal processes responsible for erosion and landsliding in an area of weakly lithified sand coastal bluffs located south of san francisco california using the results of a five year observational study consisting of site visits terrestrial lidar scanning and development of empirical failure indices we identify the lithologic and process controls that determine the failure mechanism and mode for coastal bluff retreat in this region and present concise descriptions of each process bluffs composed of weakly cemented sands unconfined compressive strength ucs between 5 and 30 kpa fail principally due to oversteepening by wave action with maximum slope inclinations on the order of 65 at incipient failure periods of significant wave action were identified on the basis of an empirical wave run up equation predicting failure when wave run up exceeds the seasonal average value and the bluff toe elevation the empirical relationship was verified through recorded observations of failures bluffs composed of moderately cemented sands ucs up to 400 kpa fail due to precipitation induced groundwater seepage which leads to tensile strength reduction and fracture an empirical rainfall threshold was also developed to predict failure on the basis of a 48 hour cumulative precipitation index but was found to be dependent on a time delay in groundwater seepage in some cases

occurrence and formation of water laid placers a placer is a deposit of residual or detrital mineral grains in which a valuable mineral has been concentrated by a mechanical agent the agent is usually running water and the valuable mineral is usually denser than quartz for example gold diamond cassiterite ilmenite or chromite it is difficult to overemphasize the importance of placers as sources of mineral wealth the witwatersrand south africa paleoplacers discovered in 1886 alone have provided over half of all the gold ever mined in the world pretorius 1976 and alluvial placer deposits of cassiterite in southeast asia presently are the world s major source of tin toh 1978 the earliest evidence of placer mining comes from stone carvings in egypt dated at 2500 b c macdonald 1983 and as early as 7 b c strabo pointed out that in turdetania spain more gold was procured from washing sand in the rivers than by digging in the mines given the economic importance of water laid placers and the long history oftheir exploitation it is remarkable that they have received so little attention in sedimentary research mining and exploration practices for the most part have been guided by empirical rules of thumb that are locally useful but lack any firm physical basis of understanding see bateman

rock coast geomorphology recent advances and future research directions there have been considerable advances in rock coast research in the past decade as measured in terms of the number of active researchers and in the number of research papers being produced this review although not exhaustive highlights many of the improvements that have been made in our ability to identify and measure the processes shaping rock coasts at a range of spatial and temporal scales we review how researchers are experimenting with new techniques grappling with quantifying the effects of multiple processes on resultant landforms and exploring how well rock coast systems relate to wider geomorphological and earth science debates recent research including those in this special issue aptly demonstrate the scientific benefits that can be accrued by studying rock coasts at a variety of spatial and temporal scales by considering the effect of the wide range of processes that operate on them and by the application of new measurement techniques and approaches despite these advances there is ample scope for future research which could profit from increasing collaboration with other coastal geomorphologists and allied earth science disciplines in order to identify and quantify linkages between rock coasts and other coastal systems it is also important that new research considers how rock coasts will respond to extreme events and to risks associated with changing climate and to how rock coast geomorphology might contribute beyond coastal science to wider debates in theoretical geomorphology

sea cliff retreat and shore platform widening steady state equilibrium we challenge the notion of steady state equilibrium in the context of progressive cliff retreat on micro tidal coasts ocean waves break at or close to the abrupt seaward edge of near horizontal shore platforms and then rapidly lose height due to turbulence and friction conceptual models assume that wave height decays exponentially with distance from the platform edge and that the platform edge does not erode under stable sea level these assumptions combine to a steady state view of holocene cliff retreat we argue that this model is not generally applicable recent data show that 1 exponential decay in wave height is not the most appropriate conceptual model of wave decay 2 by solely considering wave energy at gravity wave frequencies the steady state model neglects a possible formative role for infragravity waves here we draw attention to possible mechanisms through which infragravity waves may drive cliff retreat over much greater distances and longer timescales than imaginable under the established conceptual model copyright 2013 john wiley sons ltd

recent deep seated coastal landsliding at san onofre state beach california abstract airborne lidar collected during the period 1998 2010 and differential gps surveys conducted over 2008 2013 show recent reactivation and movement of a large deep seated coastal landslide at san onofre state beach san diego county california the overall slide complex extends about 700 m alongshore 150 m inland and an unknown distance offshore differencing digital elevation models and tracking field monuments benchmarks provide time series of quantitative topographic landslide changes and new insight in to the slide motion sequences and mechanics the slide contains several distinct primary and secondary regions moving and deforming at different rates primary slide motion includes slow seaward translational motion rotational slipping and upward offshore movement secondary processes of basal wave erosion and new inland cliffline failures contribute to primary landslide destabilization the landslide exhibits lithologic and structural controls is driven by a combination of marine and subaerial processes influences local beach morphology and deviates from typical southern california coastal cliff processes which mostly involve shallow landslides and topples large scale cross shore slide rotation has recently created new nearshore reefs eroded cliff sediments provide a local beach sand source and probably influence local nearshore ecosystems all known time periods of major historical landslide activity were preceded by elevated seasonal rainfall and analysis suggests elevated rainfall generated primary slide motion as opposed to wave action as of spring 2013 landslide activity has slowed but continued positive feedbacks including toe removal by wave activity suggest that future landsliding will probably threaten coastal infrastructure

field observations of infragravity waves and their behaviour on rock shore platforms infragravity wave igw transformation was quantified from field measurements on two shore platforms on new zealand s east coast making this the first study to describe the presence characteristics and behaviour of igws on rock platform coasts data was collected using a cross shore array of pressure transducers during a 22 hour experiment on oraka shore platform and a 36 hour experiment at rothesay bay shore platform a low pass fourier filter was used to remove gravity wave frequency oscillations allowing separate analysis of igws and the full wave spectrum offshore igw heights were measured to be 7 cm oraka and 9 cm rothesay bay which were 21 oraka and 7 5 rothesay bay the height of incident wave height at the cliff toe significant igw height averaged 15 cm at oraka and 13 cm at rothesay bay this increase in igw height over the platform during both experiments is attributed to shoaling of 40 to 55 over the last 50 60 m before the cliff toe respectively shoaling across the platform was quantified as the change in igw height from the platform edge to cliff toe resulting in a maximum increase of 1 88 and 2 63 on rothesay bay and oraka platforms igw height at the cliff toe showed a strong correlation with incident wave height the proportional increase in igw height shows a strong correlation to water level on each platform the rate of shoaling of long period waves on the shallow horizontal platforms increased at higher water levels resulting in a super elevation in water level at the cliff toe during high tide greater igw shoaling was also observed on the wider oraka shore platform results from this study show the first measurements of igws on shore platforms and identify long wave motion a significant process in a morphodynamic understanding of rock coast copyright 2011 john wiley sons ltd

identifying and removing tilt noise from low frequency 0 1 hz seafloor vertical seismic data low frequency 0 1 hz vertical component seismic noise can be reduced by 25 db or more at seafloor seismic stations by subtracting the coherent signals derived from 1 horizontal seismic observations associated with tilt noise and 2 pressure measurements related to infragravity waves the reduction in effective noise levels is largest for the poorest stations sites with soft sediments high currents shallow water or a poorly leveled seismometer the importance of precise leveling is evident in our measurements low frequency background vertical seismic spectra measured on a seafloor seismometer leveled to within 1 10 4 radians 0 006 degrees are up to 20 db quieter than on a nearby seismometer leveled to within 3 10 3 radians 0 2 degrees the noise on the less precisely leveled sensor increases with decreasing frequency and is correlated with ocean tides indicating that it is caused by tilting due to seafloor currents flowing across the instrument at low frequencies this tilting generates a seismic signal by changing the gravitational attraction on the geophones as they rotate with respect to the earth s gravitational field the effect is much stronger on the horizontal components than on the vertical allowing significant reduction in vertical component noise by subtracting the coherent horizontal component noise this technique reduces the low frequency vertical noise on the less precisely leveled seismometer to below the noise level on the precisely leveled seismometer the same technique can also be used to remove background noise due to the seafloor pressure field up to 25 db noise reduction near 0 02 hz and possibly due to other parameters such as temperature variations

hydraulic sorting of heavy mineral grains by swash on a medium sand beach abstract hydraulic sorting of detrital mineral grains in the swash zone was investigated using data on sedimentology and flow dynamics obtained from fishermans beach on the east coast of australia the beach is characteristically reflective displaying a steep beach face composed of medium sand and virtually no surf zone samples were taken from two beds enriched in heavy minerals and from the adjacent beds above and below the mineralogy of the samples was determined and measurements of grain size and settling velocity were obtained the heavy mineral grains had both a smaller intermediate diameter and a smaller settling velocity than the light mineral grains the difference between the two mineral types was typically in the range 0 25 0 50 and 2 0 2 5 cm s 1 respectively on the basis of these sedimentological measurements alone any one of three mineral sorting mechanisms could provide a feasible explanation for the development of the heavy mineral enriched beds suspension sorting entrainment sorting or shear sorting a numerical model for swash based on the nonlinear shallow water wave theory is used to provide a quantitative description of flow dynamics in the swash zone at the time the heavy mineral enriched beds were formed for the probable wave height responsible for producing the enriched beds modeled maximum flow velocity and bed shear stress at the mid swash position reached 3 5 m s 1 and 79 51 dynes cm 2 respectively given the shallow water depths and the lack of sorting in the horizontal direction of flow suspension sorting does not seem to be of overriding importance at fishermans beach the large bed shear stresses seem to also preclude entrainment sorting because for most of the time all mineral types are predicted to be in motion this contrasts with previous studies on finer grained beaches where entrainment sorting was favored and suggests that beach type may play a role in determining the sorting mechanism operating at a particular location shear sorting was found to be feasible within the modeled flow constraints at fishermans beach but it does not provide an entirely satisfactory explanation for the observed mineral sorting patterns we contend that the inability to unequivocally identify the true sorting mechanism is more a reflection of our poor understanding of the operation of these sorting mechanisms particularly within the swash zone rather than an indication that any of these mechanisms are physically inoperative in the swash zone

observations of coastal cliff base waves sand levels and cliff top shaking concurrent observations of waves at the base of a southern california coastal cliff and seismic cliff motion were used to explore wave cliff interaction and test proxies for wave forcing on coastal cliffs time series of waves and sand levels at the cliff base were extracted from pressure sensor observations programmatically and used to compute various wave impact metrics e g significant cliff base wave height wave cliff interaction was controlled by tide incident waves and beach sand levels and varied from low tides with no wave cliff impacts to high tides with continuous wave cliff interaction observed cliff base wave heights differed from standard normal and rayleigh distributions cliff base wave spectra levels were elevated at sea swell and infragravity frequencies coastal cliff top response to wave impacts was characterized using microseismic shaking in a frequency band 20 45 hz sensitive to wave breaking and cliff impacts response in the 20 45 hz band was well correlated with wave cliff impact metrics including cliff base significant wave height and hourly maximum water depth at the cliff base r2 0 75 with site specific calibration relating wave impacts and shaking and acceptable anthropogenic traffic noise levels cliff top seismic observations are a viable proxy for cliff base wave conditions the methods presented here are applicable to other coastal settings and can provide coastal managers with real time coastal conditions copyright 2016 john wiley sons ltd

changes in coastal sediment transport processes due to construction of new damietta harbour nile delta egypt abstract a combination of remote sensing field surveys and sedimentological analysis of beach sands is used to assess changes of the shorelines consequent to the construction of a harbour at damietta on the nile delta the results indicate that harbour construction and in particular the construction of two jetties that extend out from the harbour entrance have created a discontinuity in the eastward moving littoral drift imagery from landsat thematic mapper provides crude assessments of the rate of up drift accretion and down drift erosion of the shorelines despite the relatively coarse pixel size 30 m and short time scale of the monitoring period 1984 1987 1991 conventional bathymetric surveys highlight changes in the nearshore environment associated with the growth of the updrift accretionary wedge and siltation of the harbour access channel beach sediments also provide a record of the changes in erosion and accretion dominated process domains on both sides of the harbour entrance the accretionary beaches west of the western jetty having a finer mean grain size with a tendency to poorer sorting skewed to the finer fraction and preferential increase in the assemblage of low density non opaque heavy minerals the beach sands of the erosional shoreline east of the eastern jetty are characterised by coarser mean grain size with a tendency to better sorting skewed to the coarser fraction and heavy mineral assemblages dominated by opaques and high density non opaques the synergistic use of remote sensing bathymetric surveying and sedimentology provides evidence that changes have affected a much larger area than predicted at the time of harbour construction

impact of tsunami on texture and mineralogy of a major placer deposit in southwest coast of india the great indonesian earth quake 26 december 2004 triggered a tsunami wave across the bay of bengal and indian ocean basins and has brought a major havoc in several countries including india the coastal segment between thotapalli and valiazhikal in kerala state of southwest india where considerably rich beach placer deposit with ilmenite percentage of more than 70 is concentrated has been investigated to understand the impact of tsunami on coastal sediments the grain size analysis flashes out the significant differences between the pre and post tsunami littoral environments while the mineral grains collected during pre tsunami period show well sorted nature the post tsunami samples represent moderately to poorly sorted nature similarly unimodal and bimodal distributions of the sediments have been recorded for pre and post tsunami sediments respectively further mineral assemblages corresponding to before and after this major wave activity clearly indicate the large scale redistribution of sediments the post tsunami sediments register increasing trends of garnet sillimanite and rutile the total heavy mineral percentage of the post tsunami sediment also shows an improved concentration perhaps due to the large scale transport of lighter fraction magnetite percentage of post tsunami samples reflects higher concentration compared to the pre tsunami samples indicating the intensity of reworking process x ray diffraction patterns of ilmenite grains have confirmed the increased presence of pseduorutile and pseudobrookite in post tsunami samples which could be due to the mixing of more altered grains sem examination of grains also confirms the significant alteration patterns on the ubiquitous mineral of placer body the ilmenite the reason for these textural mineralogical and micromorphological changes in heavy minerals particularly in ilmenite could be due to the churning action on the deeper sediments of onshore region or on the sediments entrapped in the near shelf region of the area by the 6 m high tsunami waves

swash on a gently sloping beach waves observed in the inner surf and swash zones of a fine grained gently sloping beach are modeled accurately with the nonlinear shallow water equations the model is initialized with observations from pressure and current sensors collocated about 50 m from the mean shoreline in about i m depth and model predictions are compared to pressure fluctuations measured at five shoreward locations and to run up run up was measured with a vertical stack of five wires supported parallel to and above the beach face at elevations of 5 10 15 20 and 25 cm each 60 m long run up wire yields time series of the most shoreward location where the water depth exceeds the wire elevation as noted previously run up measurements are sensitive to the wire elevation owing to thin run up tongues not measured by the more elevated wires as the wire elevation increases the measured mean run up location moves seaward low frequency infragravity energy decreases and higher frequency sea swell energy increases these trends as well as the variation of wave spectra and shapes e g wave skewhess across the inner surf zone are well predicted by the numerical model

high frequency seismic noise generated from breaking shallow water ocean waves and the link to time variable sea states breaking waves in the nearshore are known to generate a significant amount of high frequency f 5 hz energy we investigate the correlation between the spectrum of seismic energy and the local sea states we deployed a single three component broadband seismometer approximately 50 m from the seashore and recorded continuously for approximately 10 days our observations show that during elevated sea states and presumably larger breaking waves in the surf zone the power spectral density of the wave generated seismic energy shifts to lower frequencies and higher spectral amplitudes this is similar to the observation that large plunging breakers generate 1 20 hz acoustic infrasound suggesting that a significant portion of the infrasound couples into seismic energy at the water sea floor interface based on our observations and previous models it appears that the seismic spectrum is sensitive to the wave size but not sediment movement regardless the correlation of the seismic spectral power to the height and period of ocean waves suggests that seismic observations can be used as a proxy for local sea states which may have implications for seashore sediment transport

swash aquifer interaction in the vicinity of the water table exit point on a sandy beach the coupling of sandy beach aquifers with the swash zone in the vicinity of the water table exit point is investigated through simultaneous measurements of the instantaneous shoreline swash front location pore pressures and the water table exit point the field observations reveal new insights into swash aquifer coupling not previously gleaned from measurements of pore pressure only in particular for the case where the exit point is seaward of the observation point the pore pressure response is correlated with the distance between the exit point and the shoreline in that when the distance is large the rate of pressure drop is fast and when the distance is small the rate decreases the observations expose limitations in a simple model describing exit point dynamics which is based only on the force balance on a particle of water at the sand surface and neglects subsurface pressures a new modified form of the model is shown to significantly improve the model data comparison through a parameterization of the effects of capillarity into the aquifer storage coefficient the model enables sufficiently accurate predictions of the exit point to determine when the swash uprush propagates over a saturated or a partially saturated sand surface potentially an important factor in the morphological evolution of the beach face observations of the shoreward propagation of the swash induced pore pressure waves ahead of the runup limit shows that the magnitude of the pressure fluctuation decays exponentially and that there is a linear increase in time lags behavior similar to that of tidally induced water table waves the location of the exit point and the intermittency of wave runup events is also shown to be significant in terms of the shore normal energy distribution seaward of the mean exit point location peak energies are small because of the saturated sand surface within the seepage face acting as a rigid lid and limiting pressure fluctuations landward of the mean exit point the peak energies grow before decreasing landward of the maximum shoreline position

short term patterns and processes of coastal cliff erosion in santa barbara california abstract sequential terrestrial lidar scans and 3d volumetric change were used to document coastal cliff erosion at several sites along the coast of santa barbara california retreat rates along the base middle and cliff top were calculated for six different scans throughout the el nino of 2015 16 to quantitatively link wave action to cliff base erosion and two seasonal scans were taken during 2017 to investigate patterns in erosion and retreat rates retreat rates along the cliff base middle and top converged over the course of the study period and observations and patterns in erosion help characterize the fundamental mechanisms that govern the retreat of soft shale cliffs the base and middle of the cliff preferentially eroded during high energy swell events and are strongly coupled whereas cliff top erosion is temporally variable and retreat rates increased with higher seasonal rainfall totals we observe that the cliff base experiences erosion from both abrasion and mechanical wave action but the dominant processes is segregated by elevation above the cliff toe abrasion was found to be the dominant processes at elevations up to 0 8 m above the cliff toe whereas block removal from mechanical wave action was dominant at elevations above 0 8 m threshold behavior was observed for cliff base retreat rates and spearman correlation coefficients suggest strong relationships with the sum of the wave energy flux imparted to the cliff base r2 0 84 the sum of the wave energy flux 35 000 w m r2 0 82 and the average total water level above the cliff toe r2 0 85 threshold behavior and maximum retreat rates occurred when average total water levels were 0 8 m above the cliff toe seasonal schmidt hammer measurements suggest that energy thresholds are modulated by weathering rates which remain poorly understood these thresholds when exceeded produced the highest cliff base retreat rates during the study period and reinforce the expectation that coastal cliff retreat rates will increase with rising sea levels

oregon beach sand compositions produced by the mixing of sediments under a trasngressing sea abstract heavy mineral compositions of sands from oregon beaches north of cape blanco have been determined optically in order to examine the causes of marked along coast variations in mineralogy effects of local sorting were reduced by the use of large composite samples sands from rivers and sea cliffs were also analyzed as potential sources four principal beach sand sources are identified by factor analysis the columbia river on the north a coast range volcanic source sands from the umpqua river on the south oregon coast and a metamorphic source from the klamath mountains of southern oregon and northern california most beach sands consist of mixtures of these four sources in spite of the presence of headlands which prevent along coast sand movements the results of the study demonstrate that many beach sand compositions are in part relict reflecting an along coast mixing of mineralogies from the four sources during lowered sea levels when blockage by headlands was absent the distributions of minerals originating in the klamath mountains indicate that the net littoral sand transport was to the north sand from the columbia river is found in progressively decreasing amounts in the beach sands toward the south a pattern which results from its southward diffusion in opposition to the net transport with a rise in sea level and accompanying migrations of the beaches headlands eventually interrupted the along coast mixing of sand the pattern of relict compositions inherited from mixing during lowered sea levels has been modified du ing the past several thousand years by additions of sand to the beaches from sea cliff erosion and from rivers now the columbia river supplies beach sand southward only to the first headland tillamook head at that headland there is a marked change in mineralogy and grain rounding with angular recently supplied sand to the north and rounded relict sand to the south

quantifying the environmental controls on erosion of a hard rock cliff linking hard rock coastal cliff erosion to environmental drivers is challenging with weak relationships commonly observed in comparisons of marine and subaerial conditions to the timing and character of erosion the aim of this paper is to bring together datasets to explore how best to represent conditions at the coast and to test relationships with erosion which on this coast is primarily achieved via rockfalls on the n yorkshire coast in the uk we compare a continuously monitored microseismic dataset regionally monitored coastal environmental conditions modelled at cliff conditions and periodic high resolution 3d monitoring of changes to the cliff face over a 2 year period cliff top microseismic ground motions are generated by a range of offshore nearshore and at cliff sources we consider such ground motions as proxies for those conditions that promote the occurrence of rockfalls and erosion both these data and modelled at cliff water levels provide improved insight into conditions at and wave energy transfer to the cliff the variability in microseismic modelled and regionally monitored environmental data derives statistically significant relationships with increases in the occurrence of rockfalls the results demonstrate a marine control on the total volume and size characteristics of rockfalls the strongest relationships found are with rockfalls sourced from across the entire cliff rather than just at the toe indicating that the marine influence albeit indirectly extends above and beyond the area inundated these results identify failure mechanisms driving erosion where a range of processes unique to the coast trigger failure but in a manner beyond purely wave action at the cliff toe greater erosion occurs at the cliff toe however comparing water level inundation frequency microseismic energy transfer and erosion we observe that heights up the cliff that correspond with water levels associated with low frequency high energy storms or more frequent inundation do not experience increased erosion our results describe the relationship between inundation duration energy transfer and erosion of hard rock cliffs and illustrate the relative intensity of erosion response to variations in these conditions implicitly our data suggests that in future cliffed rocky coasts may be relatively quick to respond to changes in environmental forcing