use of numerical models to study land based sedimentation and subsequent nearshore morphological evolution a beach sedimentation problem is presented this problem involves assessing the impact and importance of land based sediment sources erosion from gullies during intense rainfall and directly from cliffs by wave action on morphodynamic changes at a beach the site motivating the study is la barrosa beach spain the location is described and a discussion of possible approaches presented a schematized representation of a gully and beach is used a hybrid approach is adopted in which sediment deposition by run off and to a lesser extent cliff erosion is modelled using wave resolving hydrodynamic models it is found that significant amounts of sediment can be supplied by gully run off during storms for small run offs the swash can be involved in determining the region of deposition within the gully area with longer period motions favouring increased sediment deposition at gully sides simulations also show that swash motions can erode gully sides and the presence of a cross shore jet associated with the swash and gullies can also impact on sediment movement longer term wave averaged morphodynamic modelling without a swash zone indicates that run off deposits subsequently diffuse laterally whether under normal or oblique incidence these simulations also reveal the possibility of underlying crescentic bar shedding dynamics that may pertain during changes of wave conditions

a simple method to predict long term morphological changes a method is presented to obtain a first estimate of long term bathymetric changes based on an initial transport field obtained from a 2dh process model the results are compared with full morphodynamic simulations and measured bottom developments after extension of the harbour moles at umuiden the netherlands

a phase resolving cross shore sediment transport model for beach profile evolution abstract a phase resolving wave transformation module is combined with an intra wave sediment transport module to calculate the on offshore sediment transport rates the wave module is based on the boussinesq equations extended into the surf zone the vertical variation of the mean undertow and the intra wave sediment concentrations are calculated the net sediment transport rates are calculated and the equation for conservation of sediment is solved to predict the beach profile evolution the results of the present paper showed that the undertow contribution to the sediment transport rates is not dominating in all parts of the surf zone even for eroding beaches suggesting that other contributions should not be neglected the present model also showed that for the same offshore wave energy the time series of the oscillatory motion is important and that the effect of wave groups cannot be disregarded

a model for cross shore sediment transport a model for cross shore sediment transport due to random waves is described which adopts a vertically integrated transport description for sheetflow situations the formulation of the transport as a function of the instantaneous velocity field is based on the approach of bailard 1981 this approach assumes in essence that the instantaneous transport is proportional to some power of the instantaneous near bottom velocity implementation of this transport description in a time dependent model requires a formulation of the time mean and some low order moments of the near bottom velocity field an initial formulation based on a monochromatic second order stokes wave representation is presented the model is checked on the basis of both field and laboratory data some consequences for further study are indicated

numerical modelling of storm and surge events on offshore sandbanks abstract this contribution uses a 3 dimensional coastal area numerical model dhi s mike3 to simulate the impact of storm and surge events on offshore sandbanks three offshore sandbanks in the bristol channel are considered due to the region s sensitivity to anthropogenic pressures and the gradients in wave and tidal forcing in the area two extreme storm and surge events are simulated one co incident with spring tide and the other with neap tide reference simulations of astronomical tidal forcing only are also presented it is shown that for the two sandbanks with greater wave exposure storm conditions can provide a mechanism for the maintenance of crest position for these cases bed level changes over the crest are in the opposite direction compared to astronomically forced change for the least wave exposed bank both wave and tide only cases exhibit similar patterns of bed level change volumetric changes under astronomical forcing are shown to vary with changing maximum tidal current accretion occurs over a neap tidal cycle for all three sandbanks and as maximum tidal current increases the amount of accretion increases however over a spring tidal cycle accretion is observed for the less tidally dominated site but increasing maximum tidal current leads to reduced accretion and then erosion for the most tidally dominated bank volumetric changes under storm conditions are related to sandbank morphology and setting rather than relative wave exposure the two single banks closely tied to headlands show similar magnitude of percentage volumetric change despite being at the two extremes of wave exposure and greater erosion occurs over the neap tide event the sandbank that has associated secondary banks shows lesser percentage change and greater erosion over the spring tide event

nourishing the shoreface observations and hindcasting of the egmond case the netherlands abstract although beach nourishment policy in the netherlands is generally successful in maintaining the 1990 shoreline the efficiency of nourishments at several locations along the north sea coast is unacceptably low these locations are identified as erosion hotspots egmond aan zee is such a hotspot the bathymetric longshore irregularities make this coastal stretch highly susceptible to rip currents and horizontal circulations which transport large volumes of nourished sand to the sea in 1999 an alternative nourishment design was implemented this consisted of a shoreface nourishment at the outer bar at 7 5 m depth combined with a nourishment of the beach behind it high resolution bathymetric surveys carried out with the wesp revealed that the shoreface nourishment resulted in a significant shoreward migration of the outer bar during 1999 2001 after 2 years the system started to return to its natural dynamic equilibrium and lost the positive influence of the shoreface nourishment area shoreward movement of bars and increase of bar height which forms the first defense line of the mainland against the sea and positive contribution to the sand budget which increased as a result of the nourishment after 3 years may 1999 to april 2002 the sediment volume still had an increase of 477 500 m3 45 of the applied sand relative to may 1999 the shoreface nourishment area did not have a direct effect on the beach the shoreface nourishment area probably will have to be maintained to retain the sediment on the beach in the long run in egmond the shoreface nourishment started to disappear before the sediment could reach the beach the time scale of sediment feed to the beach zone probably is of the order of 5 10 years the shoreface nourishment seems to function as a reef creating a lee side effect that influences both cross shore and longshore sediment transport resulting in two main hypotheses firstly the longshore effect in which large waves break at the shoreface nourishment cause a calmer wave climate shoreward of the shoreface nourishment area and a reduction of the longshore current the shoreface nourishment partially blocks the wave driven longshore current secondly the cross shore effect in which shoaling waves generate onshore transport these hypotheses are supported by generated model results with both a process based profile model unibest tc and a process based coastal area model delft3d mor the unibest tc model was able to predict the detachment of the outer bar from the shoreface nourishment and to some extent the shoreward bar movements in the lee of the shoreface nourishment area the model found an increase in sediment confirming the shielding effect of the shoreface nourishment area the delft3d model found as a result of the shoreface nourishment area a decrease of the flow velocity and the wave height just shoreward of the shoreface nourishment area the model was able to predict the similar trend in sedimentation erosion pattern although the intensities were smaller in the lee of the shoreface nourishment area a clear sedimentation was found erosion was found south and seaward of the shoreface nourishment area the modeled profiles did not follow the measured profile changes the separation of the shoreface nourishment from the outer bar and the shoreward migration of the bars could not be accurately modeled because the cross shore transport caused by wave asymmetry is not taken into account in the standard version of delft3d these results were in line with the expectations

analytical and numerical modeling of sandbanks dynamics linear and nonlinear behavior of large scale underwater bedform patterns like sandbanks are studied using linear stability analysis and numerical modeling the model is based on depth integrated hydrodynamics equations with a quadratic bottom friction law and a bed load sediment transport model including a bottom slope effect first the linear stability analysis of a flat erodible bottom subject to a steady current is performed the direction of the most amplified bedform is controlled by the current whereas its wavelength is selected by the gravity driven sediment flow the instability proved to be due to the velocity component parallel to the mean flow whereas the transverse velocity and the bottom slope effect are damping processes the growth rate is then related to the spatial phase lag between flow velocity and bathymetry in order to validate the numerical model in this linear regime the growth rate and the phase celerity of an infinitesimal bottom perturbation are computed as a function of its wavevector a good agreement with linear stability results is found second using the property that the growth rates for block function and steady current are the same the nonlinear behavior of the instability is investigated for a simple tidal current the saturation height of the theoretically most amplified mode is estimated using the numerical model the analysis of the sediment fluxes gradients shows that the saturation is mostly due to the hydrodynamic processes although the saturation height slightly depends on the value of the bottom slope effect coefficient third a landau equation whose coefficients are computed from the previous results is used to predict the temporal evolution of the bedform amplitude from the initial infinitesimal perturbation to the saturation a comparison with the characteristics of continental shelf sandbanks shows that the model gives a reasonable estimation of the temporal dynamics of these large scale bedforms however the saturation height seems to be slightly overestimated the limitations of the method are also discussed

cross shore mean flow in the surf zone abstract the seaward mean returnflow or undertow in the surf zone which compensates for the shoreward mass flux above the wave trough level is found to be driven by the force imbalance between the wave momentum flux on the one hand and the set up on the other hand in qualitative agreement with the model of dyhr nielsen and sorensen 1970 a model which quantifies this imbalance is shown to yield theoretical results in good accordance with experiments when the proper boundary conditions are accounted for

boat towed radio magnetotelluric and controlled source audio magnetotelluric study to resolve fracture zones at aspo hard rock laboratory site sweden boat towed radio magnetotelluric rmt measurements using signals between 14 and 250 khz have attracted increasing attention in the near surface applications for shallow water and archipelago areas

effect of temporal and spatial variations of the primary signal on vlf total field surveys most of the airborne and ground vlf instruments presently used measure the total field response in addition to field ratios results of surveys using these instruments are adversely affected by spatial and temporal variations in the vlf primary field until now the nature of such variations has not been studied from the point of view of geophysical surveying practice spatial variations are analyzed using radio propagation models the most important result is the identification of primary field minima where surveys would be unreliable their dependence on the transmitter location is rather complex and modeling should be carried out before specifying vlf stations for a survey area spatial and temporal variations have been studied using field monitoring of the transmitted signal the results of field experiments indicate that the nature of the received vlf fields changes significantly even over moderate distances 20 30 km and that data cannot be reliably corrected over larger distances this observatio

electric and magnetic galvanic distortion decomposition of tensor csamt data application to data from the buchans mine newfoundland canada electric and magnetic galvanic distortion decomposition of tensor csamt data application to data from the buchans mine newfoundland canada

medium term 2dh coastal area modelling the state of the art in depth averaged mathematical modelling of 3 d coastal morphology is described for the medium term morphodynamic model type in which constituent models of waves currents and sediment transport based on first physical principles are linked together to describe the time evolution of the bed topography various aspects of the combined system of equations are discussed such as its mathematical character its inherent stability and its equilibrium state the results of an intercomparison of different models are shown for two test cases and the potentials and limitations of the model concept are discussed

observations of sand bar evolution on a natural beach waves currents and the location of the seafloor were measured on a barred beach for about 2 months at nine locations along a cross shore transect extending 255 m from 1 to 4 m water depth the seafloor location was measured nearly continuously even in the surf zone during storms with sonar altimeters mounted on fixed frames the crest of a sand bar initially located about 60 m from the shoreline moved 130 m offshore primarily when the offshore significant wave height exceeded about 2 m with 1 5 m of erosion near the initial location and 1 m of accretion at the final location an energetics type sediment transport model driven by locally measured near bottom currents predicts the observed offshore bar migration but not the slow onshore migration observed during low energy wave conditions the predicted offshore bar migration is driven primarily by cross shore gradients in predicted suspended sediment transport associated with quasi steady near bottom offshore flows these strong 50 cm s currents intensified near the bar crest by wave breaking are predicted to cause erosion on the shoreward slope of the bar and deposition on the seaward side the feedback amoung morphology waves circulation and sediment transport thus forces offshore bar migration during storms

simulation of coastal profile development using a boussinesq wave model a phase resolving wave transformation module is combined with an intra wave sediment transport module to calculate the on offshore sediment transport rates the wave module is based on the boussinesq equations extended into the surf zone the vertical variation of the instantaneous currents and concentrations are calculated the net sediment transport rates are calculated and the equation for conservation of sediment is solved to predict the beach profile evolution the results ofthe present paper showed that the undertow contribution to the sediment transport rates dominated only at local areas even for eroding beaches suggesting that other contributions should not be neglected

mineral exploration in the thompson nickel belt manitoba canada using seismic and controlled source em methods seismic reflection and electromagnetic em data were acquired near thompson manitoba canada to map the subsurface extent of the paleoproterozoic nickel ore bearing ospwagan group these data are supplemented by surface and borehole geology and by laboratory measurements of density seismic velocity and electrical conductivity which indicate that ospwagan group rocks are generally more seismically reflective and electrically conductive than the archean basement rocks that envelop them the combined seismic em interpretation suggests that the thompson nappe cored by ospwagan group rocks lies blind beneath the archean basement gneisses to the east of the subvertical burntwood lineament in a series of late recumbent folds and or southeast dipping reverse faults the em data require that the shallowest of these fold fault structures occur within the basement gneisses or perhaps less conductive ospwagan group rocks the results of this study demonstrate how seismic and deep sounding em methods might be utilized as regional exploration tools in the thompson nickel belt

evidence of electrical anisotropy in limestone formations using the rmt technique azimuthal resistivity surveys are often applied to complement hydrological information or to improve the location of observation boreholes in pump tests symmetric electrode configurations cannot distinguish anisotropy from lateral changes or dipping layers but asymmetric arrays e g the offset wenner array can tensor radiomagnetotellurics rmt is presented as an alternative method in studies of electrical anisotropy in the shallow subsurface the electromagnetic and geomagnetic transfer functions provide information about the dimensionality of the data these transfer functions can also be used to find the directions of anisotropy data with an anisotropic signature can be inverted for a one dimensional 1d azimuthal anisotropy model the method is faster than the azimuthal resistivity method a 380 m long profile of tensor rmt data 12 7 243 khz from limestones that overlie shale on the island of gotland sweden is used to show the merits of the method the data have a clear anisotropic signatur

development of a medium long term beach evolution model abstract a new medium long term beach evolution model is proposed this model is based on an analytically integrated sediment conservation equation and on a beach profile evolution model the sediment conservation equation provides the sediment supplies or losses the beach profile evolution model redistributes the sediment supplies or losses along the beach profile in the beach profile evolution model the definition of the complete profile is incorporated breaking zone transition zone exterior zone and geological zone the proposed model has been applied to several theoretical cases and to field data showing the advantages of this model compared to classical one line models

reproduction of estuarine bathymetry by means of a process based model western scheldt case study the netherlands abstract the current study aims to investigate the processes governing the evolution of major morphological features in alluvial estuaries as well as their morphodynamic interaction with the geometry by means of a 3d morphodynamic process based numerical model delft3d the main hypothesis is that channel shoal patterns evolve through the interaction between tidal movement the available sediments and the tidal basins geometry once such a system is not disturbed too much by extreme events stable morphological patterns will emerge that compare well with observed features starting from a flat bed and imposing the western scheldt geometry model results show two distinct time scales i e channel shoal pattern formation within decades and a slow longitudinal profile development continuing for centuries the developing channel shoal patterns reflect major morphological features observed in the western scheldt estuary using the 1998 bathymetry as a reference we applied different indicators and techniques to evaluate the model performance over time namely visual comparison hypsometries brier skill score bss mean basin depth and longitudinal profiles sensitivity analysis shows that trends in development are similar for different model parameter settings like introducing salt fresh water density differences or variations in sediment grain size and sediment transport formulation varying river discharge and including non erodible layers dredging and dumping activities and 3d hydrodynamics led to occasional improvements the geometry is an important governing factor for pattern development applying an erodible geometry reveals a timescale for geometric adaptation that is much longer than the pattern development timescale within the basin model runs including highly schematized extreme conditions suggest that extreme events play a limited role the main conclusion of the study is that the interaction between tidal forcing and basin geometry plays a major role in the development of morphological features in an alluvial tidal basin such as the western scheldt a process based model taking into account these major forcing mechanisms can predict such features with significant skill the bathymetries generated in this study may form the basis for further studies considering for example the impact of sea level rise on estuarine morphodynamic development or a rapid assessment of estuarine bathymetry in the absence of measured data

semi analytic model of tidal induced inlet flow and morphological evolution abstract a semi analytic model is developed to describe the flow through an inlet between a lagoon and the sea due to a simple tide and the related morphological response of the inlet the governing equation for the water level variation in the lagoon is derived from the continuity and momentum equations and then solved for quasi steady conditions yielding analytic expression for the main flow related properties such as lagoon amplitude maximum and mean inlet velocity tidal prism and retention time these quantities are expressed in non dimensional form where the repletion coefficient is the main independent variable a sediment balance model is formulated for the inlet that relates changes in the inlet cross sectional area to the difference between the longshore sediment transport and the transport through the inlet because of the tidal motion this balance equation can be solved to yield the conditions at equilibrium as well as the evolution towards equilibrium or closure the semi analytic model is employed in the balance equation allowing for a close coupling between inlet hydraulics and morphology investigation of inlet equilibrium revealed similarly to the escoffier curve two equilibrium situations one corresponding to stable conditions and one to unstable conditions the leading parameters in the stability analysis are the repletion coefficient and the longshore transport rate normalized with a fictive inlet transport rate

an airborne tensor vlf system from concept to realization1 radio signals from very low frequency vlf transmitters distributed world wide have been used for several decades to study the lateral variations of the electrical conductivity in the upper few hundred metres of the earth s crust traditionally in airborne applications the total magnetic fields from one or two transmitters are measured to form the basis for construction of maps that primarily show those conductive structures that are parallel or subparallel to the direction to the transmitters the tensor vlf technique described in this paper makes use of all signals available in a predefined frequency band to construct transfer functions relating the vertical magnetic field and the two horizontal magnetic field components these transfer functions are uniquely determined for a particular measuring site and contain information about the lateral conductivity variations in all directions first experiences with real field data acquired during a test survey in sweden show that maps of the so called peaker the spatial divergence of the transfer functions give an image of the conducting structures most of the structures can be correlated to small valleys filled with conducting sediments or valleys underlain by conductive fracture zones in the crystalline rocks

groundwater exploration using combined controlled source and radiomagnetotelluric techniques radiomagnetotelluric rmt 14 250 khz combined with controlled source magnetotelluric csmt 1 12 khz measurements were applied to the exploration of groundwater located in sandy formations at depths as great as 20 m below thick clay lenses a combination of approximately 30 radio frequencies and controlled source frequencies is essential for penetrating the thick clay layers the electromagnetic transfer functions of impedance tensor and tipper vectors point toward a structure that is largely two dimensional although clear three dimensional effects can be observed where the sandy formation is close to the surface the determinant of the impedance tensor was chosen for inversion using two dimensional models the final two dimensional model fits the data to within twice the estimated standard errors which is considered quite satisfactory given that typical errors are on the level of 1 on the impedance elements comparison with bore hole results and shallow reflection seismic sections show that the

a radio magnetotelluric study to evaluate the extents of a limestone quarry in estonia electromagnetic signals from distant radio transmitters in the frequency range 15250 khz were measured to model an electrical resistivity structure beneath 7 profiles in the vicinity of the karinu limestone quarry in estonia with the aim to map the extent of the economically exploitable limestone the resistivity models from a 2d inversion of determinant resistivity and phase values using an occam type of regularization contained reasonably accurate information about the geometry namely depth to the top and the bottom of the target high resistivity limestone the resistivity models correlated well with existing geological evidences as well as information from closely located boreholes however the sharp lithological boundaries seen in the boreholes were not resolved exactly in the resistivity models this is probably because of the smoothing regularization used in the inversion process combined use of borehole data together with resistivity models resulted in two major geological interpretations a towards the western part of the existing limestone quarry there is a nnw to ns striking fault covered by post glacial sediments b a potential cost effective exploitable area containing high quality highly resistive limestone is located south of the existing quarry this case study shows the applicability of the reasonably fast radio magnetotelluric rmt method for the exploration of near surface resources

detection of an ionospheric current for the preliminary impulse of the geomagnetic sudden commencement magsat observed a geomagnetic sudden commencement at an altitude of 550 km on its dawnside orbit above the south atlantic ocean the h component of the magnetic field increased monotonically by 46 nt in about 4 minutes while the d component decreased westward by 10 nt in the first 1 2 minutes and then increased gradually there was no significant deviation in the z component the comparison with ground based magnetograms showed that the negative impulse of the d component provided the first experimental evidence of the global ionospheric current system for the preliminary impulse of the geomagnetic sudden commencement

numerical modelling of the morphological response induced by low crested structures in lido di dante italy this paper analyses the morphological response induced by low crested structures on the adjacent seabed with particular interest in the erosion patterns that frequently develop at gaps and roundheads the mechanisms responsible for erosion processes are examined by means of morphodynamic simulations with the numerical suite mike 21 cams developed by dhi water environment the main purpose of the paper is to verify how and how far a commercial code can predict bed evolution in vicinity of defence structures in a real case in order to get information that may be very useful for structure design and possible maintenance of existing works the code is applied to a long term simulation on a study site that is characterized by a composite intervention and suffers from severe erosion lido di dante italy the simulation covers the period one year and a half between two available multi beam surveys in order to have a detailed real bathymetry as starting point and another one as accurate as the first to compare numerical with surveyed results all the other input data for the model as waves tide wind and sediment characteristics are derived from measurements in the area moreover the code is calibrated using wave and current data acquired during a field campaign the bed evolution derived from simulations shows a good agreement with the survey both in the locations and in the intensity of erosive and depositional areas a sensitivity analysis of results to some selected modelling parameters is performed on a shorter simulation period one month showing that accounting for bed slope in sediment transport modelling has greater effects in bathymetry evolution than the use of a complex sediment bathymetry or the representation of wave diffraction

an equilibrium model to predict shoreline rotation of pocket beaches a novel and simple beach evolution model for estimating shoreline rotation at sandy pocket beaches is presented the model is based on the assumption that the instantaneous changes to the planview shape of the shoreline depend on the long term equilibrium planview shape two years of shoreline observations extracted from video images of three artificially embayed beaches of barcelona and hourly wave timeseries are used to validate the model numerical model results and field observations show an excellent agreement with an rmse less than 1 5 m the model successfully reproduced the shoreline response over a range of scales months and years because of its simplicity and its computational efficiency the model provides a powerful tool to understand the dynamics regulating the evolution of pocket beaches and predict temporal patterns in beach rotation

exploration for unconformity type uranium deposits with audiomagnetotelluric data a case study from the mcarthur river mine saskatchewan canada unconformity type deposits supply a significant amount of the world s uranium and consist of uranium that is generally codeposited with graphite in a fault zone the low resistivity of the graphite produces a significant contrast in electrical resistivity which can be located with electromagnetic em methods the athabasca basin in western canada hosts significant uranium deposits and exploration in deeper parts of the basin has required the application of new em methods this paper presents an evaluation of the audiomagnetotelluric amt exploration method at the mcarthur river mine in the athabasca basin amt data were collected at 132 stations on a grid and two dimensional 2d and three dimensional 3d inversions were used to generate resistivity models these models showed two major results 1 a significant conductor coincident with a major basement fault p2 and the uranium deposits this conductor begins at the unconformity at a depth of 550 m and extends to a depth of at least three km an

integrated 2d modeling and interpretation of geophysical and geotechnical data to delineate quick clays at a landslide site in southwest sweden radio magnetotellurics rmt electrical resistivity tomography ert and high resolution reflection seismic data were collected along four lines to characterize the geometry and physical properties of geologic structures at a quick clay landslide site in southwest sweden the site is situated in the gota river valley where the normally consolidated materials mainly consist of glacial and postglacial sediments geotechnical data suggest the presence of quick clays above coarse grained layers these layers play a key role in the formation of quick clays and landslide triggering the rmt and ert data were individually and jointly inverted in 2d to study the resolution of resulting models for each data set the resistivity models from the joint inversions demonstrate superior resolution and accuracy compared with individual ones the geometry and location of shallower structures resolved in the 2d resistivity models from joint rmt ert inversions correlated well with those imaged in the reflection seismic data and observed in the existing geotechnical boreholes the models were poor in resolving deeper resistive bedrock at locations where the thickness of the conductive overburden exceeds a certain limit however information from the reflection seismic data could be used to estimate the depth to the top of the bedrock along all the four lines comparison between the geotechnical data and the resistivity models suggested that quick clays overlying the coarse grained layer have higher electrical resistivity than the marine clays we further validated and refined the obtained results by performing synthetic tests we showed that integration of ertand rmt data with reflection seismic data is ideal for quick clay landslide studies especially when the clay materials are thick

assessment of telemac system performances a hydrodynamic case study of anglet france the wave propagation and flow modules of the telemac system have been applied to the adour river mouth and the adjacent beaches of anglet france the wave propagation has been simulated using the phase averaged model tomawac in addition the phase resolving refdif s model has been also used as the diffraction of wind waves which is not taken into account in tomawac can occur in the vicinity of the river mouth next the hydrodynamics has been simulated using the two dimensional depth averaged flow telemac 2d model the numerical results are compared with field measurements collected in march 2003 model performance statistics are calculated in order to assess the accuracy of the predictions at six locations regarding the computation of the wave propagation a root mean square error rmse is evaluated for the significant wave height the mean period and the peak direction of propagation for the flow computation a mean absolute error mae is used as it is applicable to vector quantities a classification is also adopted that categorises the quality of the results regarding the significant wave height the average relative rmse is of 18 2 for the tomawac computations whereas the error is of 30 8 for the refdif s simulations concerning the peak wave direction the rmse is about 10 both models predict the wave direction normal to the shore whereas the experimental parameters are more variable however the areas where energy concentrates are well reproduced the classification of errors shows that telemac 2d flow predictions are in a range from excellent to reasonable

pattern of sediment transport in a microtidal river mouth using geostatistical sediment trend analysis abstract we perform a grain size trend analysis gsta to investigate sediment transport mechanisms in the grand rhone microtidal mouth during various hydroclimatic conditions the objective is to determine the efficiency of this method to explain the directions of residual transport pattern and mode of distribution of the fluvial sediment input in an environment that is very difficult to equip with instrumentation during extreme events the known biases of this sedimentological approach are reduced by using enriched geostatistical processing and choosing periods of sampling subject to unequivocal hydrodynamic forcings the modeling results and grain size distributions of surface sediments clearly show three vector fields during periods of low river discharge the first vector field corresponds to an upstream zone under fluvial influence the second field is characteristic of a mixing zone confined inside the river mouth and marked by heterogeneous sedimentation this sector is interpreted as the confrontation zone between alluvial and marine dynamics farther offshore the vectors are oriented towards the river and at counter slope in deeper zones the vectors reflect the sediment transport generated by wave refraction at the top of the mouth bar at the delta front bathymetry from 5 m to 20 m the vectors are interpreted as representing a lag deposit the periods of medium and extreme floods are associated with storms the marine dynamic regime generates a longshore drift current which brings sediments onto the mouth bar during medium flood events only the inner part of the mouth bar is highly influenced by the river during extreme flood events the river influences both the eastern part of the mouth and the wave regime in the central part consequently the gsta method shows that even during flood events the river solid discharge is not transferred towards the adjoining upper shoreface in the context of a wave dominated delta the distribution of surface sedimentation in a microtidal mouth remains controlled mainly by the swell even in periods of flood when the intensity of river dynamics is exacerbated finally all these results are similar to the known hydro sedimentological behaviours of the rhone river mouth nevertheless gsta results seem not self sufficient to explain all the processes but this method proposes an alternative approach to traditional methods used to measure bed load sediment transfer during extreme events

a morphology model for an eroding beach backed by a seawall abstract a morphology model for the prediction of beach erosion in the vicinity of a seawall has been developed the effect of wave reflection off a continuous seawall was included in the different components of the model the morphology model was verified against wave flume and wave basin physical model tests and predicted the beach evolution well for the cases simulated a sensitivity analysis of the numerical model was also performed the numerical results showed that the reflected wave had a small effect on the beach profile evolution and only reduced the volume of erosion close to the seawall slightly the morphology model also showed that for the cases tested the volume of erosion for beaches backed by a seawall was nearly the same as that for a beach without a seawall

a morphological behaviour model for the outer delta of mixed energy tidal inlets abstract the long term evolution of the seaward part of mixed energy tidal inlet systems is analysed and modelled mathematically in terms of aggregated morphological parameters the model is an adapted version of a two line model in which empirical information on the equilibrium state of the outer delta is included thus detailed computations of the water and sediment motion at the hydrodynamic time scale are avoided the viability of the concept is tested and the model is verified against data from one of the inlets of the western wadden sea the results of a number of practice based applications are shown and discussed

quasi 3d modelling of nearshore currents abstract existing concepts of wave induced nearshore current models in the cross shore vertical plane 2dv and depth integrated 2dh are combined to a quasi 3d mathematical model this combination is tested for reproducing correct results in 2dv and 2dh situations the importance of the various contributions to the wave induced secondary circulation in the vertical plane is investigated for realistic parameter ranges which leads to the conclusion that both the non breaking and the breaking fraction of a random wave field in the surf zone generate important secondary currents additional computations show the relevance of a 3d approach of nearshore currents even in seemingly simple situations like a plane sloping beach with obliquely incident waves

the predictability of cross shore bed evolution of sandy beaches at the time scale of storms and seasons using process based profile models deterministic and probabilistic profile models have been compared with hydrodynamic and morphodynamic data of laboratory and field experiments on the time scale of storms and seasons the large scale laboratory experiment is a pure 2d case and offers and ideal test case for cross shore profile models as disturbing alongshore non uniformities are absent the field experiments are performed at the egmond site the netherlands during the eu coast3d project and represent storm time scale oct nov 1998 as well as seasonal time scale conditions may 1998 sep 1999 the objective of the paper is to present information of coastal processes on these time scales and to assess the predictive capabilities coastal process based profile models with respect to hydrodynamics and morphodynamics at sandy beaches on the time scales of storms and seasons profile models can quite accurately errors smaller than 10 represent the cross shore significant wave height distribution in the surf zone if the wave breaking model is properly calibrated the wave breaking coefficient should be a function of local wave steepness and bottom slope for most accurate results profile models can reasonably represent the cross shore and longshore currents undertow in a pure 2d case and in 3d field conditions profile models including cross shore mixing effects and breaker delay effects do not produce better predictions of the longshore and cross shore current velocities profile models using default settings can quite reasonably simulate the behaviour of the outer and inner bars on the storm time scale the behaviour of the beach cannot be modelled with sufficient accuracy on the storm time scale profile models can reasonably simulate the post storm onshore bar migration provided that the near bed orbital velocities and wave asymmetry related sand transport are represented in a sufficiently accurate way using non linear wave theories profile models cannot simulate the beach recovery processes on the post storm time scale because these essentially 3d processes are not sufficiently known to be included in the models profile models using default settings cannot simulate the behaviour of the outer and inner bars and the beach on the seasonal time scale the behaviour of the outer bar on the seasonal time scale can only be represented properly after tuning using measured bed profiles the simulation of the inner bar and beach morphology on the seasonal time scale could not be improved by tuning

vertical flow structure during sandy duck observations and modeling abstract observations of the vertical distribution of time averaged cross shore and alongshore flows during the sandy duck field experiment are compared with model predictions to assess the parameters governing the flow behaviour the measurements were obtained with a vertical stack of eight two component current meters with the lowest and highest sensor at respectively o 0 1 and o 2 7 m above the bed observations under breaking wave conditions within the surfzone show that the maximum return flow velocities occur in the lower part of the water column consistent with laboratory observations under non breaking conditions outside the surfzone the maximum return flow velocities are observed closer to the water surface again in line with laboratory results analogous to previous observations the measured longshore current velocity profiles are logarithmic under non breaking conditions and become more depth uniform under breaking conditions the model description of the vertical structure of the flow includes the presence of wind stresses wave stresses pressure gradients turbulent eddy viscosity and a wave boundary layer the model utilizes parabolic shape functions to describe the vertical distribution of the turbulent eddy viscosity in the middle layer and within the bottom boundary layer eddy viscosity is enhanced in regions where turbulence is produced i e near the surface in the case of breaking waves and within the bottom boundary layer estimates of the wave breaking induced turbulent eddy viscosity and bottom friction are obtained by minimizing the model measurement discrepancies predictions utilizing calibrated expressions for both the turbulent eddy viscosity and bottom friction are in general agreement with the observations provided the wave transformation and associated mass flux are modeled correctly and a parabolic eddy viscosity distribution is used using a piecewise constant eddy viscosity distribution generally results in a degrading of the agreement between measurements and model results

mechanisms for linear sandbank formation and maintenance in relation to dynamical oceanographic observations abstract theories associated with flow in the vicinity of headlands and sandbanks together with proposed mechanisms for sandbank formation and maintenance are reviewed to exemplify water and sand movement around a sandbank on a tidally dominated shelf tidal currents in the vicinity of a headland associated linear sandbank are described these data are integrated with sedimentological information on bedforms and grain size distributions the sandbank under detailed investigation the scarweather sands is located along the northern coastline of the bristol channel uk which is an area susceptible to high energy inputs the maximum spring tidal range here is around 10m and a 6000km fetch is available for storm wave approach from the atlantic ocean but the area is 460km from the shelf break detailed observations are presented from 11 long term current meter stations located within 10km of the sandbank currents are described in terms of residual water circulation shallow water harmonics and tidal ellipse characteristics bedload transport paths are inferred from the distribution of bedforms grain size and m2 m4 tidal current interactions transport vectors are predicted from near bed current meter observations combined with empirically derived formulae it is demonstrated that water circulation and sand transport paths form part of a clockwise eddy system around the sandbank mechanisms controlling the location and the characteristics of this particular sandbank are shown to be explicable in terms of a combination of models for sandbank formation and maintenance the results of the present study are thought to be applicable directly to headland associated sandbanks elsewhere it is shown on the basis of theoretical considerations that the pattern of residual water movement and possibly sand transport around this sandbank could be extended to continental shelves on a global basis

an energetics total load sediment transport model for a plane sloping beach bagnold s energetics based total load sediment transport model for streams is used as a basis for the development of a total load model of time varying sediment transport over a plane sloping bed in both the bedload and suspended load the transport rate vectors are found to be composed of a velocity induced component directed parallel to the instantaneous velocity vector and a gravity induced component directed down slope the model is applied to idealized surfzone conditions leading to estimates of the local longshore and onshore offshore sediment transport rates as well as the equilibrium beach slope as a function of the local wave and current conditions the model is combined with a nonlinear longshore current model and spatially integrated to obtain predictions of the total longshore transport rate as a function of the incident wave conditions the results support the general form of the wave power equation except that the wave power coefficient is no longer constant but is instead a complex function of the incident wave and beach characteristics

new evidence of a meridional current system in the equatorial ionosphere an interesting variation in the geomagnetic d component has been found by analysis of the magsat data characteristics of this variation are that it appears everyday on the low latitude duskside and is antisymmetric about the dip equator negative in the northern hemisphere that the magnitude from 5 to 25 nt depends upon the geographic longitude and altitude and that no corresponding change can be seen on the ground magnetic data the change suggests a meridional current system in the equatorial ionosphere produced in association with the electrojet current along the dip equator this effect should be taken into account in the study of geomagnetic anomaly of internal origin with the magsat data

a behavioral template beach profile model for predicting seasonal to interannual shoreline evolution 1 this contribution presents a simple behavioral template model for beach profile evolution which is calibrated and tested against a 6 year time series of shoreline position derived from a coastal imaging system at the gold coast australia from a coastal management perspective the position of the shoreline is arguably one of the most important morphodynamic parameters to be monitored and predicted and therefore forms the focus of this paper the template model attempts to encapsulate some of the current understanding of coastal dynamics deduced from both scientific investigations and observations the model framework is based on a simple relaxation model whereby the profile approaches a template exponentially with time under conditions of constant forcing the template evolves dynamically in response to incident wave forcing such that when a threshold value of the dimensionless fall velocity hs wtp where hs offshore significant wave height tp peak wave period and w sediment fall velocity is exceeded the beach face erodes and flattens and the shoreline retreats landward forming an erosional scarp and a breakpoint bar conversely when the falls below threshold progradation and steepening of the shoreface ensues accompanied by the evolution of a swash bar and breakpoint step the gold coast data are used to calibrate the threshold value of 4 0 which is close to the time series mean 3 8 testing the calibrated model on unseen data shows that it is able to reproduce the dominant seasonal interannual shoreline succession observed at this site and up to 77 of the detrended shoreline variability

a quasi 3d phase resolving hydrodynamic and sediment transport model a two dimensional phase resolving wave transformation module is combined with an intra wave sediment transport module to calculate the two dimensional sediment transport rates the wave module is based on the boussinesq equations extended into the surf zone two hydrodynamic modules are developed for the calculation of the vertical variation of the eddy viscosity and the currents the intra wave sediment concentrations and sediment transport rates are also calculated the model was verified against several test cases and a sensitivity analysis was performed both hydrodynamic modules produced close results for the mean currents the two models also produced close results for the sediment transport rates with larger differences observed at the locations with a stronger undertow the model results showed that for irregular breaking waves the mean sediment concentration cannot be calculated directly from the mean eddy viscosity

boat towed radio magnetotellurics a new technique and case study from the city of stockholm we have developed a new data acquisition system and technique to measure the radio magnetotelluric rmt signals from distant radio transmitters with the objective of mapping and modeling electric

delineating hydrothermal stockwork copper deposits using controlled source and radio magnetotelluric methods a case study from northeast iran radio and controlled source tensor magnetotelluric rmt and cstmt methods are used to target hydrothermal veins of copper mineralization the data were acquired along six eastwest and three

data assimilation for a coastal area morphodynamic model morecambe bay this paper investigates the use of data assimilation in coastal area morphodynamic modelling using morecambe bay as a study site a simple model of the bay has been enhanced with a data assimilation scheme to better predict large scale changes in bathymetry observed in the bay over a 3 year period the 2dh decoupled morphodynamic model developed for the work is described as is the optimal interpolation scheme used to assimilate waterline observations into the model run each waterline was acquired from a sar satellite image and is essentially a contour of the bathymetry at some level within the inter tidal zone of the bay for model parameters calibrated against validation observations model performance is good even without data assimilation however the use of data assimilation successfully compensates for a particular failing of the model and helps to keep the model bathymetry on track it also improves the ability of the model to predict future bathymetry although the benefits of data assimilation are demonstrated using waterline observations any observations of morphology could potentially be used these results suggest that data assimilation should be considered for use in future coastal area morphodynamic models

integration of controlled source and radio magnetotellurics electric resistivity tomography and reflection seismics to delineate 3d structures of a quick clay landslide site in southwest of sweden abstractquick clay which is the main cause of landslides that occur in the northern countries liquefies easily and its presence implies an increased risk of landslide geophysical methods have been increasingly used in landslide investigations three dimensional electric resistivity tomography radio magnetotelluric rmt controlled source rmt csrmt and high resolution reflection seismic data were acquired at a quick clay landslide site in the southwest of sweden the main objectives were to evaluate the capability of each method in delineating different subsurface geologic structures that controlled a peculiar and hazardous retrogressive type landslide in the study area a 3d resistivity model from the inversion of csrmt data showed the best correlation with the reflection seismic data and borehole information thanks to the broad frequency range of the data set it better imaged the resistive crystalline bedrock underlying the marine conductive clays and showed considerable correlations with the

long term morphological modeling of a tidal inlet the arcachon basin france abstract the arcachon lagoon on the french atlantic coast is a triangular shaped lagoon of 20 km on a side connected to the ocean by a 3 km wide inlet between the mainland and an elongated sand spit this tidal inlet exhibits a particularly active morphology due to locally strong tidal currents and rough wave conditions during the past 300 years minimum and maximum spatial extents of the cap ferret sand spit have varied by 8 km while one or two channels have alternately allowed circulation between the lagoon and the ocean these impressive morphological changes have never prevented regular flushing of the lagoon eventhough the spit came as close as 300 m from the coast during the 18th century according to bruun s concept of tidal inlet stability theory and engineering 1978 510 pp the balance between longshore littoral transport and the tidal prism ensures the perpetuity of the inlet process modeling was believed to give better insight into the respective roles of tides and waves in driving the long term morphological changes of the inlet a two dimensional horizontal morphodynamic model was therefore developed combining modules for hydrodynamics waves sediment transport and bathymetry updates the use of process models at a scale of decades requires a schematization of the input conditions we defined representative mean annual wave and tide conditions with respect to sediment transport i e conditions that induce the same annual transport as measured in the field driven by these representative conditions simulations run from the 1993 bathymetry show that the tide is responsible for the opening of a new channel at the extremity of the sand spit where tidal currents are the strongest while waves induce a littoral transport responsible for the longshore drift of sand bodies across the inlet one particular simulation consisted in running the model from a hypothetical initial topography where the channels are filled with sand and the entire inlet is set to a constant depth 3 m the results show the reproduction of a channel and bar system comparable to historical observations which supports the idea that the lagoon is unlikely to be disconnected from the ocean provided tide and wave conditions remain fairly constant in the following decades

analysis of far field erosion induced by low crested rubble mound structures this paper focuses on the analysis of the morphological response induced by low crested structures on the adjacent seabed with emphasis on the far field erosion that is frequently observed close to roundheads and at the gaps between structures the analysis is based on observations of far field erosion both at prototype scale and in laboratory experiments mechanisms responsible for the observed erosion are highlighted using coastal area numerical modelling tools to simulate the flow patterns induced by schemes involving low crested structures finally an example of the use of a coastal area morphological modelling system to investigate the dependence of the far field erosion processes on the freeboard of the coastal protection structures is presented and discussed

storm time changes of geomagnetic field at magsat altitudes 325 550 km and their comparison with changes at ground locations the values of h x y and z at magsat altitudes were first expressed as residuals h x y and z after subtracting model values hmd xmd ymd and zmd the storm time variations of h showed that h dusk was larger negative than h dawn and occurred earlier indicating a sort of hysteresis effect effects at magsat altitudes were roughly the same 10 accuracy as at ground indicating that these effects were mostly of magnetospheric origin the y component also showed large storm time changes the latitudinal distribution of storm time h showed north south asymmetries varying in nature as the storm progressed it seems that the central plane of the storm time magnetospheric ring current undergoes latitudinal meanderings during the course of the storm

combined magnetic electromagnetic and resistivity study over a highly conductive formation in orrivaara northern sweden different geophysical methods were used to determine the characteristics of a highly conductive structure in northern sweden first discovered on airborne data airborne electromagnetic very low frequency data indicate a high conductivity structure coincident with low magnetic patterns the airborne data were processed in different ways to enhance various structures features in particular we introduce a new transformation to current density that is suitable for delineating conductive structures ground measurements of the total magnetic field radiomagnetotelluric measurements and resistivity imaging provided valuable information that was used in the compilation of a new bedrock map over the area the results of our measurements indicate that the conducting structure consists of metasedimentary rocks containing thin horizons of pyrrhotite and graphite

the effects of wave chronology on medium and long term coastal morphology the sequencing or chronology of wave events plays an important role in determining how coastlines and nearshore regions evolve over medium and long timescales from weeks to decades however present day computer models of coastal morphology treat the input wave conditions in either a deterministic i e a single wave sequence or a probabilistic manner in neither method are the effects of the full range of possible future wave sequences for given overall statistical values calculated the methodology presented here addresses this problem by multiple model runs using different re orderings of a wave sequence a series of tests demonstrate different aspects of wave chronology and its importance in the prediction of seabed and beach levels the method provides a means both for understanding wave chronology effects and for predicting these effects in practical engineering problems involving medium and long timescale changes to coastal morphology

three dimensional imaging of a ag au rich epithermal system in british columbia canada using airborne z axis tipper electromagnetic and ground based magnetotelluric data abstractwe have evaluated results from a study combining airborne z axis tipper electromagnetic ztem and ground based magnetotelluric mt data to image an epithermal system in british columbia the spatially coincident use of these two methods allowed for a direct comparison of both data sets in the overlapping frequency band and showed that both measurements were consistent inversion of just the ztem data suffered from the lack of electric field amplitude information which could be provided by the mt data three dimensional inversion modeling of the two individual data sets was performed models of electrical resistivity derived from both data sets were consistent and could be correlated with the geological and structural setting of the mineralization gold is associated with disseminated pyrite and marcasite in quartz sericite altered felsic volcanic rocks and intrusions especially near the contact with mafic volcanic rocks and a late diorite intrusion the quartz sericite alteration yields a cond

a multi scale hybrid long term morphodynamic model for wave dominated coasts abstract process based modules based on conservative equations to solve the transport of waves currents and sub aqueous sediment and behavior oriented modules based on empirical descriptions of cliff erosion bed load and terrestrial aeolian sand transport are coupled with up scaling measures and stability maintaining approaches in a parallel code to simulate decadal to millennial scale morphological evolution of wave dominated coasts an application to the southern baltic sea for a hindcast of holocene morphogenesis of the darss zingst peninsula demonstrates the robustness of the model the model is then used to investigate the morphogenesis and evolution of spits in an idealized fetch limited sandy coastal environment evolution of the spit system can be categorized into three periods according to the simulation results in the early period all initial coastline perturbations are amplified due to the high angle wave effects size competition between adjacent spits starts afterwards interaction between adjacent spits dominates the middle period smaller spits tend to retrogress due to unbalanced sediment budget and this sediment loss feeds further growth of their larger neighbors the retrograded spits are either smoothed or evolve into barrier lagoons and relatively stable large scale spits originating from larger spits are developed in the late period low frequency storms impinging from a regular high angle onto the coastline facilitate the development of spits in the early period but become a hindering factor afterwards terrestrial aeolian transport not only plays a key role in stabilizing the spits but is also revealed as an important factor for long term coastline erosion

modelling morphological processes in the vicinity of shore parallel breakwaters abstract a coastal area morphological modelling system is used to investigate the planform development tombolo or salient behind a single surface piercing detached breakwater a quasi three dimensional q3d description of the flow and the sediment transport together with a revised bed level update scheme were incorporated recently in the morphological modelling suite applied in the present investigation the q3d sediment transport formulation used allows simulating beach profile evolution and planform development simultaneously several breakwater layouts were investigated in a series of tests in which the incident wave condition was taken as constant in time the investigation was done for surface piercing shore parallel breakwaters in a non tidal environment the morphological simulation results for the planform shape agree qualitatively with field observations and predictions from empirical rules using the simulation results simple design curves for surface piercing breakwaters are derived the importance of properly accounting for the influence of wave diffraction when modelling sediment transport and morphology in the vicinity of shore parallel structures is also investigated the present paper summarises much of the work performed at dhi water environment over the past 10 years within the field of coastal area morphological modelling

analysis of horizontally two dimensional morphological evolutions in shallow water a system of depth integrated equations forming a rather primitive mathematical model of horizontally two dimensional 2dh bed evolutions in shallow water is analyzed using characteristics theory the analysis shows that the solution of this system exhibits an essentially two dimensional propagation character with bottom disturbances traveling in other directions than the current velocity and the sediment transport the results of this analysis are verified by numerical experiments and interpreted physically their relevance for numerical modeling of 2dh morphological processes in shallow water is discussed and their occurrence and recognizability in natural situations is checked by a qualitative comparison with field observations

modelling of morphological changes due to coastal structures two different concepts are applicable to model the nearshore morphodynamics the first one takes into account only final consequences of acting mechanisms and is aimed at the prediction of long term trends in beach development another approach implies the modelling of the whole suite of elementary processes responsible for changes in nearshore bottom topography during a given storm and it is the approach used in the present work a coastal area model complex is proposed that allows to reproduce the local morphological changes due to both the natural processes and the influence of coastal structures such as a groin a detached breakwater and a navigable channel underwater trough consisting of a traditional series of basic components the model differs from other ones in essential aspects concerning the treatment of transport mechanisms in particular the determination of wave induced near bed mean flow is based on the hypothesis that the direction and magnitude of bottom drift depend on difference between the actual rate of energy dissipation and its threshold value marking the flow reversal point this hypothesis is shown to explain a general trend of cross shore mean flow distributions observed in the nearshore region besides the influence of the wave breaking process on sediment suspension is taken into account and the contribution of the swash zone to total sediment transport is included examples of computed morphological response are represented to demonstrate the model capability a satisfactory agreement of computations with available data is pointed out

modelling the effect of wave overtopping on nearshore hydrodynamics and morphodynamics around shore parallel breakwaters wave overtopping nearshore coastal structures such as shore parallel breakwaters can significantly alter the current circulation and sediment transport patterns around the structures which in turn affects the formation of tombolos and salients in the nearshore area this paper describes the implementation of a wave overtopping module into an existing depth averaged coastal morphological mode coast2d and model applications to investigate the effect of wave overtopping on the hydrodynamics and morphodynamics around a group of shore parallel breakwaters the hydrodynamic aspects of the model were validated against a series of laboratory conditions the model was then applied to a study site at sea palling norfolk uk where 9 shore parallel segmented breakwaters including 4 surface piercing and 5 low crested breakwaters are present for the storm conditions in nov 2006 the model results were compared with laboratory data and field measurements showing a good agreement on both hydrodynamics and morphological changes further analysis of wave overtopping effect on the nearshore hydrodynamics and morphodynamics reveals that wave overtopping has significant impacts on the nearshore circulation sediment transport and the resulting morphological changes within such a complex breakwater scheme under the storm and macro tide conditions the results indicate the importance of including the wave overtopping in modelling nearshore morphodynamics with the presence of coastal structures

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

2dh mathematical modelling of morphological evolutions in shallow water abstract a class of compound mathematical models of transient morphological evolutions in shallow water is discussed based on commonly applied horizontally two dimensional formulations of the water and sediment motion in the coastal zone three major aspects of the composition of such models are considered viz the specific adequacy of the constituent models the balance of the total model and the possibility of spurious interactions the lacunae in the knowledge and the tools needed to judge a proposed model at these points are indicated examples of spurious interactions are described in further detail and techniques to trace and avoid them are given these examples concerning morphological evolutions without the influence of waves show that the advective acceleration terms in the flow model play an essential part in the bottom evolution and its interaction with the current and that incorporation of the bottom slope effects on the sediment transport is indispensable in models with a local transport formulation

tensor csamt survey over the sulphur springs thermal area valles caldera new mexico u s a part ii implications for csamt methodology the resistivity model for the sulphur springs area in the companion paper part i plus the availability of overlapping controlled source audiomagnetotelluric csamt and magnetotelluric mt data has allowed study of far field to near field transitions source field geometries over the survey area and scalar tensor impedance discrepancies the regional setting of conductive paleozoic sediments over resistive basement seriously reduced depth of exploration within the plane wave regime to about 1 20th of the transmitter receiver separation rather than the traditional 1 3rd to 1 5th based on half space models as frequency falls to where skin depth in the sedimentary layer exceeds its thickness transmitter electromagnetic em fields enter the resistive basement and may diffuse to the receiver with relatively little attenuation promoting near field behavior comparisons are made of observed electric e and magnetic h fields inside and outside the caldera with em fields computed from layered resistivi

numerical modelling of erosion rates life span and maintenance volumes of mega nourishments mega nourishments aiming at providing long term coastal safety nature qualities and recreational space have been applied recently at the holland coast and are considered at various other places in the world methods to quickly evaluate the potential and lifetime of these coastal mega nourishments are therefore very much desired which is the main objective of this research two types of mega nourishments can be distinguished feeder type mega nourishments may erode freely to feed adjacent coasts for a more natural dynamic dune growth while permanent mega nourishments are designed to preserve safety levels and need to maintain their size and shape and thus needs to be nourished themselves the design and impact assessment studies for both types of mega nourishments require detailed morphological studies to determine the morphological evolution in this paper 2dh delft3d and 1d unibest cl and longmor numerical models were calibrated using data of the sand motor mega nourishment and were then applied to model a series of mega nourishments with various width over length ratios and volumes in order to derive relations and design graphs for erosion rates life span and maintenance volumes these relations and design graphs can be used in project initiation phases and feasibility studies the magnitude of the modelled wave driven longshore sediment transport rates in 1d coastline models depend on the representation of wave refraction on the lower shoreface since a distinction should be made between the non rotating lower shoreface and active surfzone it was shown that the life time of nourishments is mainly determined by the dimensions of the nourishment and incoming wave energy

quasi three dimensional modelling of the morphology of longshore bars a morphological quasi three dimensional q3d area model for barred coasts has been developed the model combines a two dimensional depth integrated model for wave driven currents with a model for undertow circulation currents the combined model makes a simultaneous simulation of the bar forming processes associated with the undertow and the horizontal wave driven circulation currents which may cause instabilities of the bar and the formation of rip channels situations with normal and oblique wave incidence are considered compared to the depth integrated approach the q3d model produces less pronounced alongshore irregularities for obliquely incident waves for normal incident waves the q3d model produces a crescentic bar while the depth integrated model predicts almost straight sections of the bar interrupted by rip channels the sensitivity to variation of wave angle and beach slope is further investigated

modeling shore normal large scale coastal evolution abstract we present a model for the evolution of the shelf surface in response to marine sedimentary processes following morphodynamical theory the model presupposes a characteristic configuration of the shelf surface that in profile is a concave up exponential curve whose steeper inner limb is the shoreface the profile is seen as an equilibrium response to the variables of sedimentation the profile translates landward or seaward as sea level rises or falls but will do so in an state of dynamic equilibrium with the shape of the profile varying according to changes in 1 the rate of sea level change 2 the time averaged wave and bottom current conditions 3 the average allochthonous sediment supply rate and 4 the sediment grain size distribution the governing equations for the model include an equation for time averaged cross shore diabathic sediment flux and the sediment continuity equation p simulations of continental margin profiles show that profile adjustments affect mainly the coefficient of curvature of the profile an increase in the rate of sea level rise straightens the profile it decreases the slope of the shoreface but increases the shelf slope an increase in sediment input increases profile curvature the shoreface steepens while the shelf floor flattens an intensification of hydraulic climate straightens the profile in a manner similar to an increase in the sea level rise rate while an increase in grain size increases profile curvature as does an increase in sediment input

a numerical model of beach morphological evolution due to waves and currents in the vicinity of coastal structures a numerical model was developed of beach morphological evolution in the vicinity of coastal structures the model includes five sub models for random wave transformation surface roller development nearshore wave induced currents sediment transport and morphological evolution the model was validated using high quality data sets obtained during experiments with a t head groin and a detached breakwater in the basin of the large scale sediment transport facility at the coastal and hydraulics laboratory in vicksburg miss usa the simulations showed that the model reproduced well the wave conditions wave induced currents and beach morphological evolution in the vicinity of coastal structures both salient and tombolo formation behind a t head groin and a detached breakwater were simulated with good agreement compared to the measurements c 2011 elsevier b v all rights reserved

equilibrium shoreline modelling of a high energy meso macrotidal multiple barred beach abstract 8 year time series of incident wave energy and monthly alongshore averaged beach surveys at the high energy meso macrotidal multiple barred truc vert beach are analysed we apply two behaviour oriented equilibrium shoreline models that relate the rate of cross shore shoreline displacement to the wave energy and the wave energy disequilibrium between the wave energy and the equilibrium wave energy that would cause no change to the present shoreline location the two models show similar skill results show that the equilibrium shoreline model concept works on meso macrotidal multiple barred beaches with similar skill when applied to non barred and or micro mesotidal beaches provided that a relevant shoreline proxy is used simulations show that truc vert beach responds predominantly at seasonal timescales rather than at individual storm frequency the first winter storms drive the most pronounced erosion events because both the wave energy disequilibrium and erosion change potential are large the best shoreline proxy at truc vert beach is the mean high water level where the inner bar and berm dynamics have little influence on the shoreline cross shore displacement implications for shoreline monitoring through video imagery on this type of beach are discussed results also reveal that the equilibrium shoreline concept can be extended to an equilibrium beach profile concept pending further improvements