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

infragravity swash parameterization on beaches the role of the profile shape and the morphodynamic beach state abstract a field campaign was undertaken at somo beach in northern spain with the aim of understanding the processes involved in the generation of low frequency swash taking the parameterization presented in earlier studies as a starting point a novel empirical model was defined based on a database which included datasets from somo beach and from 9 other experiments this new parameterization was obtained by relating the horizontal cross shore component of the infragravity swash to the foreshore slope and the morphodynamic beach state through the non dimensional fall velocity parameter the role of previous sea states when determining the morphodynamic beach state was also assessed a strong correlation between low frequency oscillations and the morphology of the beach was verified resulting in a substantial improvement over existing infragravity swash predictions proposed in the literature

simulating wave setup and runup during storm conditions on a complex barred beach abstract the purpose of this study is to assess the ability of the swash model to reproduce wave setup and runup in highly dissipative stormy conditions to proceed we use data collected during the ecors truc vert 08 experiment especially during the johanna storm in the winter of 2007 008 wave setup under hs 8 2 m and tp 18 3 s and runup under 6 4 m and peak period up to 16 4 s we test different model settings 1d and 2d mode and model forcing spectral and parametric to reproduce sensor measured wave setup at several locations in the nearshore area and video measured runup on two beach profiles for the whole tested configurations the wave setup is reproduced accurately results considering all the sensor locations in the near shore area in 1d and 2d are significantly correlated to the observations with respectively 0 66 and 0 81 rmse 0 13 m and 0 08 m without any significant bias observations and simulations of runup are investigated in terms of spectra and statistic component 1d simulations produces an overall overestimation and no significant improvement is obtained by modifying the breaking parameters the results for 2d simulations are fairly satisfactory reproducing significant swash height s but are significantly improved with spectral forcing than parametric with respectively 0 73 and 0 71 rmse 0 19 m and 0 43 m generally the model reproduces accurately the infragravity component but tends to overestimate the incident component leading to an overestimation of the energy density for moderate wave conditions and more accurate results for higher energy wave conditions results in 2d with spectral forcing show a saturation of the infragravity component with a threshold around hs 4 to 5 m which is comparable to the observations collected at truc vert beach as regards the conventional statistical parameter for runup estimation r2 three methods are applied to derive the 2 exceedence value for runup from observed and simulated shoreline vertical elevation time series when r2 is based on the sum of wave setup and half of the significant swash height results provided by the model are close or even better than estimations provided by empirical formulas from the bibliography defining r2 as the exceeded 2 values of the time derived considering the cumulative distribution function of the entire water level time series also provide fairly good results results using only runup maxima time series are less satisfactory in the two last cases r2 is slightly underestimated for moderate wave conditions hs

a self similar scaling for cross shelf exchange driven by transient rip currents transient rip currents episodic offshore flows from the surf zone to the inner shelf present a recreational beach hazard and exchange material across the nearshore ocean the magnitude and offshore extent of transient rip current induced exchange and its relative importance to other inner shelf exchange processes are poorly understood here 120 model simulations with random normally incident directionally spread waves spanning a range of beach slopes and wave conditions show that the transient rip current exchange velocity is self similar the nondimensional exchange velocity surf zone flushing time and cross shore decay length scale are scaled by beach slope and wave properties depending strongly on wave directional spread transient rip current driven exchange can be compared to other cross shelf exchange processes for example transient rip current driven exchange is stronger than wave induced stokes drift driven exchange up to six surf zone widths from shore

advances in swash zone research small scale hydrodynamic and sediment transport processes abstract extensive research efforts in the last decade have improved knowledge of swash zone processes this paper reviews and synthesizes from 2004 onward the research advances of small scale hydrodynamics and sediment transport processes considering field laboratory and numerical modeling efforts swash zone hydrodynamics are examined by means of shoreline motions fluid velocities pressure gradients flow structure bed shear stress friction coefficients and turbulence subsequently advances related to sediment transport mechanisms and morphological changes are described detailed descriptions of measuring techniques novel findings and the strengths and weaknesses of the different approaches are discussed the review also acknowledges the major advances in the development of instrumentation to collect highly resolved flow and sediment concentration measurements in direct proximity of the bed and the experimental framework for analyzing local dynamics on a wave by wave time scale e g dam break

swash oscillations on a natural beach run up swash oscillations were measured on a gently sloping beach face for a variety of incident wave conditions run up energy spectra at wind wave frequencies show an 3 dependence and energy levels that are independent of incident wave height this suggests saturation in contrast run up energy at surf beat periods increase approximately linearly with increasing incident wave energy thus in the inner surf zone where wave breaking limits the energy at wind wave frequencies the principal manifestation of large incident wind waves is energetic surf beat

wave reflection and saturation on natural beaches the role of the morphodynamic beach state in incident swash abstract in this work we present an analysis of the effect of the processes related to beach morphodynamic state on high frequency incident band swash oscillations the effect of wave reflection and saturation on swash oscillations was assessed based on new field data measured under different morphodynamic conditions on the northern coast of spain data measured under more reflective conditions indicated the occurrence of a cross shore partial standing structure a process which was observed earlier using laboratory and numerical data part of the dataset data showed saturation in accordance to limits between reflection and saturation established in previous works the new measured data was added to a large database compiled from previous works and assuming the hypothesis that the reflection and saturation processes are related to the beach state a new parameterization was established to calculate the incident swash under different morphodynamic conditions our results indicate that the role of the foreshore slope and wave steepness varies according to the morphodynamic beach state the proposed formula showed a reasonable correlation with measured data 2 0 56 and rmse 0 41 m and improvements in s i n c predictions were observed for all beach types when compared to existing formulas

runup kinematics on a natural beach runup kinematics on a gently sloping natural beach are examined with detailed measurements from video images resistance wires deployed at five elevations between 5 and 25 cm above and parallel to the beach face and pressure sensors located in the inner surf zone as suggested in a previous study comparing a single level resistance wire and manually digitized films runup measurements are sensitive to the sensor elevation above the bed owing to the elongated shape of the runup tongue the measured mean runup elevation setup and vertical excursion increase as the sensor elevation decreases with the video based runup estimates having the maximum means and variances for the six data runs the average ratios of the videobased setup and significant runup excursion to estimates based on wires elevated 15 cm above the bed are 2 7 and 1 5 respectively these trends combined with the high coherence and small phase difference between the video and the lowest wire demonstrate that the video based estimates correspond to a very near bed less than a few centimeters elevation wire measurement the measured increase in runup excursion with decreasing sensor elevation and the cross shore variation in the amplitudes of pressure fluctuations at infragravity frequencies are consistent with the theory for linear in viscid normally incident standing waves for example valleys in the pressure spectra occur at approximately the predicted standing wave nodal frequencies also in accord with small amplitude wave theory observed swash excursions are nearly identical to pressure fluctuations at the location of the measured runup mean for pressure sensors located seaward of the most offshore bed level rundown however at very low frequencies where reflection is typically assumed complete and dissipation negligible the observed near bed swash magnitudes are overamplified relative to a best fit of the linear standing wave model based on the amplitude and phase of the seaward observations

the importance of explicitly modelling sea swell waves for runup on reef lined coasts abstract the importance of explicitly modelling sea swell waves for runup was examined using a 2d xbeach short wave averaged surfbeat xb sb and a wave resolving non hydrostatic xb nh model of roi namur island on kwajalein atoll in the republic of marshall islands field observations on water levels wave heights and wave runup were used to drive and evaluate both models which were subsequently used to determine the effect of sea level rise and extreme wave conditions on wave runup and its components results show that specifically modelling the sea swell component using xb nh provides a better approximation of the observed runup than xb sb which only models the time variation of the sea swell wave height despite good model performance of both models on reef flat water levels and wave heights xb sb has a bias of 0 108 0 057 m and scatter index of 0 083 0 639 whereas xb nh has bias of 0 132 0 055 m and 0 122 0 490 respectively however both models under predict runup peaks the difference between xb sb and xb nh increases for more extreme wave events and higher sea levels as xb nh resolves individual waves and therefore captures ss wave motions in runup however for even larger forcing conditions with offshore wave heights of 6 m the island is flooded in both xb sb and xb nh computations regardless the sea swell wave energy contribution in such cases xb sb would be adequate to model flooding depths and extents on the island while requiring 4 5 times less computational effort

remote sensing technology and geographic information system modeling an integrated approach towards the mapping of groundwater potential zones in hardrock terrain mamundiyar basin in this paper remote sensing evaluation of digital elevation models dem geographic information systems gis and fieldwork techniques were combined to study the groundwater conditions in mamundiyar basin tamilnadu several digital image processing techniques including standard color composites intensity hue saturation ihs transformation and decorrelation stretch ds were applied to map rock types remote sensing data were interpreted to produce lithological and lineament maps dem was used for lineament and geomorphologic mapping all thematic layers were integrated and analyzed in a gis the overall results demonstrate that the use of remote sensing and gis provide potentially powerful tools to study groundwater resources and design a suitable exploration plan

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

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

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

observations and predictions of run up for a significant range of offshore wave conditions and foreshore slopes run up observations are compared to semiempirical formulations and predictions of an existing numerical model based on the depth averaged one dimensional nonlinear shallow water equations with bore like breaking wave dissipation and quadratic bottom friction the numerical model is initialized with time series of sea surface elevation and cross shore velocity observed in 80 cm mean water depth approximately 50 m offshore of the mean shoreline on a gently sloping beach and in 175 cm water depth 100 m offshore of the shoreline on a steep concave beach run up was measured with a stack of resistance wires at elevations 5 10 15 20 and 25 cm above and parallel to the beach face at sea swell frequencies nominally 0 05 f 0 18 hz run up energy is limited by surf zone dissipation of shoreward propagating waves so that increasing the offshore wave height above a threshold value does not substantially increase the predicted or observed sea swell run up excursions e g run up is saturated existing semiempirical saturation formulations are most consistent with the observations and numerical model predictions of run up excursions nearest the bed in contrast at infragravity frequencies 0 004 f 0 05 hz where surf zone dissipation is relatively weak and reflection from the beach face is strong e g saturation formulas are not applicable the run up excursions increase approximately linearly with increasing offshore wave height the numerical model also accurately predicts that the tongue like shape of the run up results in sensitivity of run up measurements to wire elevation for instance run up excursions and mean vertical superelevation above the offshore still water level increase with decreasing wire elevation and continuous thinning of the run up tongue during the wave uprush can result in large phase differences between run up excursions measured at different wire elevations numerical model simulations suggest that run up measured more than a few centimeters above the bed cannot be used to infer even the sign of the fluid velocities in the run up tongue

influence of directional spreading on wave overtopping of sea dikes with gentle and shallow foreshores abstract the work highlights the importance of directional spreading effects on wave overtopping estimation in shallow and mild sloping foreshores wave short crestedness leads in general to a reduction of mean overtopping discharges on coastal structures in the present work the case of a sea dike with gentle foreshore in very and extremely shallow water conditions is analysed physical model tests have been carried out in order to investigate the effect of directional spreading on overtopping and incident wave characteristics in the present experimental campaign the effect of wave spreading has only been investigated for perpendicular wave attack results show that directional spreading is proved to cause a reduction of average discharge of sea dikes with gentle and shallow foreshore expressions for the reduction factor for directional spreading are derived fitted on the tested database the use of this reduction factor leads to more accurate prediction and avoids overtopping overestimation however reduction factor formulations are overtopping formula depending

observations of wave energy fluxes and swash motions on a low sloping dissipative beach 1 field observations of swash and ocean waves show that runup saturation at infragravity frequencies 0 025 0 035 hz infragravity waves where typically less than 5 of the linear energy flux was reflected from the beach and where similar to the sea swell band the swash energy was independent of offshore wave energy the infragravity frequency range of saturation was determined by the tide with saturation extending to lower frequencies at low tide when the local beach face slope over the concave shaped profile was gentler runup was strongly dominated by infragravity frequencies which accounted on average for 96 of the runup variance and its energy levels were entirely consistent with strong infragravity wave dissipation observed in the surfzone particularly when including the nonlinear contributions to the wave energy fluxes the infragravity wave dissipation was strongly associated with breaking of sea swell waves which abruptly decreased nonlinear transfers to infragravity frequencies and made infragravity dissipation prevail over forcing within the breaking region our observations show evidence of nonlinear interactions involving infragravity and high frequency harmonic waves and suggest that these harmonics could play a role in the wave energy balance near the shoreline on low sloping dissipative beaches

optimisation of focused wave group runup on a plane beach abstract insight is provided into focused wave group runup on a plane beach by means of laboratory wave flume experiments and numerical simulations a focused wave group is presented as an alternative to an empirical description of the wave conditions leading to extreme runup second order correction to the laboratory wavemaker generation signal is observed to remove about 60 of the sub harmonic error wave that would otherwise contaminate coastal response experiments laboratory measurements of the wave runup time history are obtained using inclined resistance type wires and copper strips attached to the beach surface the numerical wave runup model is based on hybrid boussinesq nonlinear shallow water equations empirical parameters for wave breaking and bed friction and a wetting and drying algorithm after calibration against experimental runup data the numerical model reproduces satisfactorily the propagation shoaling and runup of focused wave groups over the entire length of the wave flume results from a comprehensive parametric study show that both measured and predicted maximum runup elevations exhibit strong dependence on the linear focus amplitude of the wave group linked to its probability of occurrence the focus location and the phase of the wave group at focus the results also demonstrate that extreme runup events owing to focused wave incidence cannot be characterised using spectral parameters alone the optimal band of focus locations shifts onshore as linear focus amplitude of the incident wave group increases optimisation of phase and focus location leads to a maximum runup elevation at each linear amplitude and when generated using second order corrected paddle signals the maximum runup appears to approach saturation at very large focused wave amplitudes this study therefore moves beyond simple wave focusing and presents a focused wave group as a tool for investigating the relationship between extremes within an incident wave field and extreme wave runup

observations of swash under highly dissipative conditions video measurements of swash were made at the low sloping beach of the multiple bar system at terschelling netherlands the majority of the measurements were conducted under highly dissipative conditions with iribarren numbers 0 the ratio of beach slope to the square root of offshore wave steepness less than 0 2 infragravity 0 004 0 05 hz waves dominated the swash with an average ratio of infragravity and total swash height rig r of 0 85 using linear regression we investigated the dependence of swash parameters on environmental conditions such as short wave height period and local beach slope on average rig was about 30 of the offshore wave height h0 the slope in the linear h0 dependence of rig amounted to only 0 18 considerably smaller than that observed on steeper beaches the data set shows evidence for saturation of the higher infragravity frequencies for 0 less than roughly 0 27 in our opinion this saturation caused the constant of proportionality in the linear relationship between rig h0 and 0 to be significantly larger than that observed under higher iribarren number regimes the saturated tails of the swash spectra had an approximate f 3 roll off where f is frequency whereas in general the nonsaturated parts were white this lack of significant peaks casts doubt on the causality between infragravity waves and nearshore bars

observations of waves and currents during barrier island inundation overwash and inundation on barrier islands can transport sediment onshore leading to vertical accretion these processes could ensure barrier island growth in times of sea level rise but wave and current fields during overwash and inundation are not well understood field data of water levels waves and currents were collected on a barrier island in the netherlands to investigate the hydrodynamics during island inundation observations show that even in shallow water depths 0 5 m wave energy was not completely dissipated as waves propagated from the north sea onshore additionally locally generated wind waves entered the field area from the wadden sea and propagated offshore infragravity waves were an important part of the wave field particularly onshore of the beach crest they were observed to be onshore progressive and displayed a bore like shape when water depths were shallow wave breaking was the dominant dissipation mechanism for high frequency waves as well as for infragravity waves which is in agreement with prior research on infragravity wave energy dissipation on mild sloping closed boundary beaches a large scale offshore directed water level gradient between the wadden sea and the north sea side caused by elevated water levels in the wadden sea during the storms frequently drove an offshore flow if it was large enough to exceed the cross shore gradient due to wave setup in addition elevated water levels in the wadden sea decreased current velocities due to a decrease in water level gradients this study highlights the influence of back barrier processes on the hydrodynamics during inundation

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

wave runup and overwash on a prototype scale sand barrier abstract accurate methods to predict wave runup are of critical importance to coastal engineers extreme runup during storm conditions can present a danger to coastal infrastructure and lead to dune overtopping and erosion overwash of barrier beaches and is an essential design parameter for certain coastal protection works this paper uses data obtained during the unique bardex ii prototype scale laboratory experiment on a reflective sand barrier to investigate wave runup and overwash runup measurements were acquired using ultrasonic altimeters 2d scanning lidar and camera systems under controlled wave and water level conditions it was found that extreme runup r 2 scaled well with the deepwater irribarren number where the beach slope was taken to be the beach face gradient the lower limit of the swash zone defined by the 2 wave rundown limit was also found to be a function of the irribarren number and was consistently below the swl in all tests the high resolution free surface measurements obtained using the ultrasonic altimeters and lidar enabled an analysis of the dynamics of individual swash events it was found that the vertical runup excursion of each swash correlated strongly with the height of the bore at collapse and could be predicted based on the assumption of a conversion of potential to kinetic energy at bore collapse

observations of wave run up and groundwater seepage line motions on a reflective to intermediate meso tidal beach abstract swash sw and ground water seepage line gwsl motions have been recorded at an exposed meso tidal reflective to intermediate beach using a coastal video monitoring system during a 15 month period the monitoring period allowed the collection of imagery under a wide variety of wave and beach morphological conditions and sw and gwsl velocities were extracted on a wave by wave basis the continuous double bounded kumaraswamy kw probability distribution is proposed to parameterize the sw and gwsl height distributions and since the distribution shape of the latter was shown to be influenced by the tidal elevation generic tidal elevation dependent kw pdfs are proposed the beach face slope more than any other factor tested was found to apply certain control to the mean uprush backwash and gwsl velocities the results also indicate that in reflective to intermediate beaches the gwsl lies between the mean and 2 exceedance swash elevation with the occurrence of swash running above a saturated beach face being controlled by the tidal gradient and the significant wave height

large runup controls on a gently sloping dissipative beach observations on a mildly sloping beach suggest that the largest runup events are related to bore bore capture bbc a numerical model based on the reynolds averaged navier stokes equation is implemented to evaluate the effects that bbc have on runup from simulations with realistic sea states bbc is found to be a necessary but not sufficient condition for large runup generation the dominant dynamics leading to bbc are amplitude dispersion and interactions with infragravity waves in the outer and inner surf zone respectively when the effects of bbc are isolated it is found that the runup associated with the merging of two bores is at least 50 larger than that associated with the larger of the two waves in a monochromatic wave train the phase difference of the incident waves with the infragravity wave can generate up to 30 variability of the runup maxima the majority of the shoreward directed momentum flux prior to runup initiation is related to the interaction between the bores and the infragravity wave followed by that of the incident infragravity waves alone

effect of wave frequency and directional spread on shoreline runup 1 wave breaking across the surf zone elevates the mean water level at the shoreline setup and drives fluctuations about the mean runup runup often is divided into sea swell 0 04 0 3 hz and lower frequency infragravity 0 00 0 04 hz components with energetic incident waves runup is dominated by infragravity frequencies and total water levels combined setup and runup can exceed 3 m significantly contributing to coastal flooding and erosion setup and runup observations on sandy beaches are scattered about empirical parameterizations based on near shoreline beach slope and deep water wave height and wavelength accurate parameterizations are needed to determine flooding and erosion risk to coastal ecosystems and communities here numerical simulations with the boussinesq wave model funwavec are shown to statistically reproduce typical empirical setup and runup parameterizations furthermore the model infragravity runuprs ig strongly depends on the incident wave directional and frequency spread about the mean direction and peak frequency realistic directional spread variations change rs ig equivalent to a factor of two variation in incident wave height the modeled rs ig is shown to vary systematically with a new non dimensional spreading parameter that involves peak frequency frequency spread and directional spread this suggests a new parameterization forrs ig potentially useful to predict coastal flooding and erosion

partitioned postseismic deformation associated with the 2009 mw 6 3 l aquila earthquake surface rupture measured using a terrestrial laser scanner using 3d terrestrial laser scan tls technology we have recorded postseismic deformation on and adjacent to the surface rupture formed during the 6th april 2009 l aquila normal faulting earthquake mw 6 3 using surface modeling techniques and repeated surveys 8 124 days after the earthquake we have produced a 4d dataset of postseismic deformation across a 3 65 m area at high horizontal spatial resolution we detected millimetre scale movements partitioned between discrete surface rupture slip and development of a hangingwall syncline over 10 s of meters we interpret the results as the signal of shallow afterslip in the fault zone we find 52 of the total postseismic hangingwall vertical motion occurs as deformation within 30 m of the surface rupture the total postseismic vertical motions are approximately 50 that of the coseismic we highlight the importance of quantifying partitioned postseismic contributions when applying empirical slip magnitude datasets to infer palaeoearthquake magnitudes

improving digital tools for quaternary field survey a case study of the rodoretto valley nw italy in the modern geological mapping activities geomatics technologies can facilitate data collection during field survey and avoid practical problems related to the transposition of that data onto topographic maps this paper describes an innovative tool the solid true orthophoto stop for the structured acquisition and recording of geological field survey data that is immediately available in a gis framework an experimental software graphical interface has been developed to manage the stop application during the survey the benefits of the stop system were tested by producing a digital map of the quaternary formations and landforms in a 3 km2 sector of the rodoretto valley a minor tributary of the germanasca valley northwestern italy

numerical modeling of wave runup on steep and mildly sloping natural beaches abstract runup on ocean beaches includes steady wave setup and oscillating swash often decomposed into wind generated sea swell ss and lower frequency infragravity ig waves we show that the numerically fast open source numerical model 1d swash predicts accurately the bulk properties of runup observed on two natural beaches one steep and one shallow sloped for a range of incident wave conditions the runup tongue shape was measured with a scanning lidar and the waterline location was defined in both the observations and model with a 10 cm depth threshold runup is reasonably accurately predicted with energetic e g 5 m significant height incident waves even though the assumption of 1d bound waves significantly overpredicts infragravity energy at the offshore boundary in 10 m depth the model data comparisons are limited by statistical chatter often larger in runup than offshore because runup energy is concentrated in the relatively narrow infragravity ig band with low effective degrees of freedom

modeling surf zone tracer plumes 2 transport and dispersion 1 five surf zone dye tracer releases from the hb06 experiment are simulated with a tracer advection diffusion model coupled to a boussinesq surf zone model funwavec model tracer is transported and stirred by currents and eddies and diffused with a breaking wave eddy diffusivity set equal to the breaking wave eddy viscosity and a small 0 01 m2 s 1 background diffusivity observed and modeled alongshore parallel tracer plumes transported by the wave driven alongshore current have qualitatively similar cross shore structures although the model skill for mean tracer concentration is variable from negative to 0 73 depending upon release cross shore integrated tracer moments normalized by the cross shore tracer integral have consistently high skills 0 9 modeled and observed bulk surf zone cross shore diffusivity estimates are also similar with 0 72 squared correlation and skill of 0 4 similar to the observations the model bulk absolute cross shore diffusivity is consistent with a mixing length parameterization based on low frequency 0 001 0 03 hz eddies the model absolute cross shore dispersion is dominated by stirring from surf zone eddies and does not depend upon the presence of the breaking wave eddy diffusivity given only the bathymetry and incident wave field the coupled boussinesq tracer model qualitatively reproduces the observed cross shore absolute tracer dispersion suggesting that the model can be used to study surf zone tracer dispersion mechanisms

evaluation of wave runup predictions from numerical and parametric models abstract wave runup during storms is a primary driver of coastal evolution including shoreline and dune erosion and barrier island overwash runup and its components setup and swash can be predicted from a parameterized model that was developed by comparing runup observations to offshore wave height wave period and local beach slope because observations during extreme storms are often unavailable a numerical model is used to simulate the storm driven runup to compare to the parameterized model and then develop an approach to improve the accuracy of the parameterization numerically simulated and parameterized runup were compared to observations to evaluate model accuracies the analysis demonstrated that setup was accurately predicted by both the parameterized model and numerical simulations infragravity swash heights were most accurately predicted by the parameterized model the numerical model suffered from bias and gain errors that depended on whether a one dimensional or two dimensional spatial domain was used nonetheless all of the predictions were significantly correlated to the observations implying that the systematic errors can be corrected the numerical simulations did not resolve the incident band swash motions as expected and the parameterized model performed best at predicting incident band swash heights an assimilated prediction using a weighted average of the parameterized model and the numerical simulations resulted in a reduction in prediction error variance finally the numerical simulations were extended to include storm conditions that have not been previously observed these results indicated that the parameterized predictions of setup may need modification for extreme conditions numerical simulations can be used to extend the validity of the parameterized predictions of infragravity swash and numerical simulations systematically underpredict incident swash which is relatively unimportant under extreme conditions

how well can wave runup be predicted comment on laudier et al 2011 and stockdon et al 2006 abstract laudier et al 2011 suggested that there may be a systematic bias error in runup predictions using a model developed by stockdon et al 2006 laudier et al tested cases that sampled beach and wave conditions that differed from those used to develop the stockdon et al model based on our re analysis we found that in two of the three laudier et al cases observed overtopping was actually consistent with the stockdon et al predictions in these cases the revised predictions indicated substantial overtopping with in one case a freeboard deficit of 1 m in the third case the revised prediction had a low likelihood of overtopping which reflected a large uncertainty due to wave conditions that included a broad and bi modal frequency distribution the discrepancy between laudier et al results and our re analysis appear to be due in part to simplifications made by laudier et al when they implemented a reduced version of the stockdon et al model

the generation of surfzone eddies in a strong alongshore current abstractthe surfzone contains energetic two dimensional horizontal eddies with length scale larger than the water depth yet the dominant eddy generation mechanism is not understood the wave resolving model funwavec is used to simulate surfzone eddies in four case examples from the sandyduck field experiment that had alongshore uniform bathymetry the funwavec model is initialized with the observed bathymetry and the incident wave field in 8 m depth and reproduces the observed cross shore structure of significant wave height and mean alongshore current within the surfzone the wave resolving funwavec modeled e f ky spectra and the bulk frequency and ky integrated rotational velocities are consistent with the observations below the sea swell band 0 05 hz demonstrating that the model can be used to diagnose surfzone eddy generation mechanisms in the mean squared perturbation vorticity budget the breaking wave vorticity forcing term is orders of magnitude larger than the shear instability gene

wave runup during extreme storm conditions 1 video measurements of wave runup were collected during extreme storm conditions characterized by energetic long swells peak period of 16 4 s and offshore height up to 6 4 m impinging on steep foreshore beach slopes 0 05 0 08 these conditions induced highly dissipative and saturated conditions over the low sloping surf zone while the swash zone was associated with moderately reflective conditions iribarren parameters up to 0 87 our data support previous observations on highly dissipative beaches showing that runup elevation estimated from the variance of the energy spectrum can be scaled using offshore wave height alone the data is consistent with the hypothesis of runup saturation at low frequencies down to 0 035 hz and a hyperbolic tangent fit provides the best statistical predictor of runup elevations

the effect of stokes drift and transient rip currents on the inner shelf part i no stratification abstractthis is part ii of a two part study focused on stokes drift and transient rip current trc effects on the unstratified part i and stratified this paper inner shelf part i focuses on funwavec coupled ocean atmosphere wave sediment transport coawst coupling and trc effects on mixing and exchange on an unstratified inner shelf here two simulations r3 and r4 are performed on a stratified inner shelf and surfzone with typical bathymetry stratification and wave conditions r3 is a coawst only simulation no trcs while r4 has funwavec coawst coupling with trcs in r4 trcs lead to patchy near surface cooling vertical isotherm displacement and increased water column mixing for both r3 and r4 the mean lagrangian circulation has two nearly isolated surfzones and inner shelf overturning circulation cells with a stronger r4 inner shelf circulation cell the r4 inner shelf vertical velocity variability is 2 3 times stronger than a simulation with trcs and no stratification relative

combining digital elevation data srtm aster high resolution satellite imagery quickbird and gis for geomorphological mapping a multi component case study on mediterranean karst in central crete abstract remote sensing data have become more and more popular for geomorphological investigations because their steadily increasing level of detail and accessibility opens up new potentials in this context this paper examines the application and quality of digital elevation models srtm and aster dems high resolution satellite imagery quickbird and gis techniques for the detection and mapping of karst landforms mainly enclosed depressions at different scales in the ida mountains of central crete besides discussing methodological issues and evaluating suitability potentials we conducted an exemplary case study based on spatial analysis of the regional karst morphology different input datasets and processing methods are applied gis based analysis land cover classification raster calculations etc in order to carry out an area wide surveying and mapping of karst depressions the findings are supported and validated by auxiliary field studies due to the level of detail and occasional data errors an exclusive use of satellite imagery or digital elevation models for automatic karst landform detection performs insufficiently our results demonstrate that mapping karst features through remote sensing is significantly dependent on scale of interest existing environmental conditions and data quality a semi automatic data integration approach on the basis of digital datasets generated by combined satellite image processing and dem analysis yields the best results especially when indirect karst indicating variables like iron oxide rich sediments are included as detection criteria the multi component application presented in this paper provides a time saving and effective tool for meso to macro scale object detection and extensive study areas however the potential of fully automated karst feature mapping still needs to be explored in future work concerning the spatial dimension of karstification in central crete the gis based results allow differentiating further geomorphological characteristics e g by indicating a significant altitudinal change of karst forms within the study area size and shape of depressions dolines uvalas and poljes vary considerably due to the geological setting climatic impacts neotectonics and elevation

modeling surf zone tracer plumes 1 waves mean currents and low frequency eddies 1 a model that accurately simulates surf zone waves mean currents and low frequency eddies is required to diagnose the mechanisms of surf zone tracer transport and dispersion in this paper a wave resolving time dependent boussinesq model is compared with waves and currents observed during five surf zone dye release experiments in a companion paper clark et al 2011 compare a coupled tracer model to the dye plume observations the boussinesq model uses observed bathymetry and incident random directionally spread waves for all five releases the model generally reproduces the observed cross shore evolution of significant wave height mean wave angle bulk directional spread mean alongshore current and the frequency dependent sea surface elevation spectra and directional moments the largest errors are near the shoreline where the bathymetry is most uncertain the model also reproduces the observed cross shore structure of rotational velocities in the infragravity 0 004 f 0 03 hz and very low frequency vlf 0 001 f 0 004 hz bands although the modeled vlf energy is 2 3 times too large similar to the observations the dominant contributions to the modeled eddy induced momentum flux are in the vlf band these eddies are elliptical near the shoreline and circular in the mid surf zone the model data agreement for sea swell waves low frequency eddies and mean currents suggests that the model is appropriate for simulating surf zone tracer transport and dispersion

radiography of a normal fault system by 64 000 high precision earthquake locations the 2009 l aquila central italy case study 1 we studied the anatomy of the fault system where the 2009 l aquila earthquake mw 6 1 nucleated by means of 64 k high precision earthquake locations spanning 1 year data were analyzed by combining an automatic picking procedure for p and s waves together with cross correlation and double difference location methods reaching a completeness magnitude for the catalogue equal to 0 7 including 425 clusters of similar earthquakes the fault system is composed by two major faults the high angle l aquila fault and the listric campotosto fault both located in the first 10 km of the upper crust we detect an extraordinary degree of detail in the anatomy of the single fault segments resembling the degree of complexity observed by field geologists on fault outcrops we observe multiple antithetic and synthetic fault segments tens of meters long in both the hanging wall and footwall along with bends and cross fault intersections along the main fault and fault splays the width of the l aquila fault zone varies along strike from 0 3 km where the fault exhibits the simplest geometry and experienced peaks in the slip distribution up to 1 5 km at the fault tips with an increase in the geometrical complexity these characteristics similar to damage zone properties of natural faults underline the key role of aftershocks in fault growth and co seismic rupture propagation processes additionally we interpret the persistent nucleation of similar events at the seismicity cutoff depth as the presence of a rheological i e creeping discontinuity explaining how normal faults detach at depth