dune recovery after storm erosion on a high energy beach vougot beach brittany france abstract on 10th march 2008 the high energy storm johanna hit the french atlantic coast generating severe dune erosion on vougot beach brittany france in this paper the recovery of the dune of vougot beach is analysed through a survey of morphological changes and hydrodynamic conditions data collection focused on the period immediately following storm johanna until july 2010 i e over two and a half years results showed that the dune retreated by a maximum of almost 6 m where storm surge and wave attack were the most energetic dune retreat led to the creation of accommodation space for the storage of sediment by widening and elevating space between the pre and post storm dune toe and reducing impacts of the storm surge dune recovery started in the month following the storm event and is still ongoing it is characterised by the construction of secondary embryo dunes which recovered at an average rate of 4 4 5 cm per month although average monthly volume changes varied from 1 to 2 m 3 m 1 these embryo dunes accreted due to a large aeolian sand supply from the upper tidal beach to the existing foredune these dune construction processes were facilitated by growth of vegetation on low profile embryo dunes promoting backshore accretion after more than two years of survey the sediment budget of the beach dune system showed that more than 10 000 m 3 has been lost by the upper tidal beach we suggest that seaward return currents generated during the storm of 10th march 2008 are responsible for offshore sediment transport reconstitution of the equilibrium beach profile following the storm event may therefore have generated cross shore sediment redistribution inducing net erosion in the tidal zone

probabilistic design of dunes an example from the netherlands abstract dunes act as primary sea defences in some regions over the world and they have then the same function as common sea dikes they prevent flooding and protect people against drowning e g in the netherlands in other regions dunes form only the transition zone between sea and land and are sometimes part of important holiday resorts in those cases high investment costs have been made frequently in building houses and hotels close to the edge of the sea under storm surge conditions however dunes can be damaged by the sea knowing the amount of retreat of the dune s toe is in both cases important a design method for dunes primarily directed at the problem of the loss of life safety has been developed in the netherlands in recent years due to the large number of factors determining dune erosion a probabilistic design method was developed

groundwater salinity influenced by holocene seawater trapped in incised valleys in the red river delta plain brackish to salty waters have been found in inland areas of delta aquifers geophysical data and modelling suggest that salty groundwater in the red river delta originates from trapped seawater contained in underlying holocene marine deposits

an investigation of the multi scale temporal variability of beach profiles at duck using wavelet packet transforms abstract in an earlier paper a particular discrete wavelet transform dwt was used to study the complex variation of beach profile changes however use of the dwt requires that the sequence of spatial and temporal resolution is fixed as a dyadic sequence which means that the variability over longer intervals is not characterised well here we introduce the discrete wavelet packet transform dwpt that uses an adaptive scaling to partition the data variance according to an entropy cost function the advantages of this approach are demonstrated by its application to the study of temporal variability of a 22 year record of beach profile data from the field research facility frf at duck north carolina usa time series of beach elevations at three locations across a particular profile are investigated in detail we conclude that the dwpt provides a superior analysis of non stationary time series to that of the dwt with improved resolution of the scale intervals of the variability the beach elevation around the shoreline is shown to respond at both sub annual and interannual scales but variability at an annual scale is weak moving seaward into deeper water the variance is partitioned into fewer and longer scales it is confirmed that elevation changes around the inner bar at duck exhibit a strong interannual variation consistent with plant et al plant n g holman r a and freilich m h 1999 a simple model for interannual sandbar behaviour journal of geophysical research 104 c7 15755 15776 around 23 of the variance around the inner bar is explained at the temporal scale of 64 128 months which is consistent with the bar behaviour of 6 years found by ruessink et al ruessink b g wijnberg k m holman r a kuriyama y and van enckevort i m j 2003 intersite comparison of interannual nearshore bar behaviour journal of geophysical research 108 c8 1 12 a significant new finding is however that about 26 of the variance is attributable to temporal scales of 16 21 3 months reconstruction of the wavelet packet components for individual temporal scales is shown to provide a means for identifying the impact and scale of non stationary events such as storms on the beach response this provides further information that can be used to interpret the morphological changes in terms of the forcing processes and also serves to inform morphodynamic modelling

on the estimation of radar polarization orientation shifts induced by terrain slopes in recent studies d l schuler et al 2000 applied polarimetric imaging radar derived orientation angles to measure topography and j s lee et al 2000 used orientation angles for polarimetric sar data compensation to ensure accurate estimation of geophysical parameters in rugged terrain areas to support these applications it is important to accurately estimate shifts in orientation angles induced by the azimuth slope variations however in many cases inconsistency in the estimation of orientation angle shifts was encountered in several areas introducing noisy and erroneous results the present authors develop a unified analysis of estimation algorithms based on the circular polarization covariance matrix the concept of reflection symmetry is used to explain the soundness of the circular polarization method and to show problems associated with other algorithms l band polarimetric synthetic aperture radar sar images of camp roberts ca are used to substantiate this theory

experimental study of runup for sandy beaches under waves and tide abstract this paper describes an experimental investigation of runup for intermediate sandy beaches from a physical modelling in a wave flume with tide simulation shoreline elevation measurements are acquired over a wide range of conditions using an optical method simultaneous morphological and hydrodynamic changes are considered to determine the best parameters to predict the maximum wave runup the tidal level significantly affects the breaking conditions position height and type and the slopes of the beach present data show that the surf zone slope and the wave breaking height should be used to estimate the maximum runup the results are compared with previous formulations issued from the literature a new formula is proposed for the runup estimation for intermediate beaches

decorrelation in interferometric radar echoes a radar interferometric technique for topographic mapping of surfaces implemented utilizing a single synthetic aperture radar sar system in a nearly repeating orbit is discussed the authors characterize the various sources contributing to the echo correlation statistics and isolate the term which most closely describes surficial change they then examine the application of this approach to topographic mapping of vegetated surfaces which may be expected to possess varying backscatter over time it is found that there is decorrelation increasing with time but that digital terrain model generation remains feasible the authors present such a map of a forested area in oregon which also includes some nearly unvegetated lava flows such a technique could provide a global digital terrain map

laboratory investigation of beach scarp and dune recession due to notching and subsequent failure analytical models to calculate notch development and subsequent mass failure of dunes are presented the notch evolution model is based on a transport equation for sediment from the dune and the sediment volume conservation equation whereas the models of mass failure are derived using elementary engineering statics and soil mechanics an empirical transport coefficient in the model describing the notch growth rate is found to be related to the hydrodynamic forcing at the dune normalized by geotechnical parameters describing the resistive strength of the dune two modes of mass failure are modeled whereby the overhang generated by the removal of material from the dune foot notching slides downward or topples over following the development of a tensile crack some distance shoreward of the maximum notch depth the accuracy of the notch evolution and mass failure models are assessed by comparing calculated recession distances against measurements from a small scale laboratory experiment

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

wide band polarimetric radar inversion studies for vegetation layers the authors show how the entropy alpha target decomposition scheme may be used for parametric inversion studies on random particle cloud models for vegetation layers the decomposition is detailed first and then applied to a two parameter model for backscatter from a random cloud of small anisotropic particles the two main parameters used are the mean particle shape and the mean orientation angle of the cloud an inversion algorithm is presented and applied to broad band polarimetric radar data from the european microwave signature laboratory emsl joint research center ispra italy the results have been obtained from measurements of a fir tree and a ficus tree they show a wavelength scale dependence of the shape and distribution of scatterers which reflects the complex volume scattering nature of such problems moreover the values and trends from these two trees as a function of the frequency are different as expected from their physical structures consequently this algorithm has the potential to be useful in the construction of classification schemes for vegetation

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

radar modeling of a boreal forest the authors report on the use of microwave modeling ground truth and synthetic aperture radar sar data to investigate the characteristics of forest stands a mixed coniferous forest stand has been modeled at sar frequencies p l and c bands the extensive measurements of ground truth and canopy geometry parameters were performed in a 200 m square hemlock dominated plot inside a forest hemlock trees in the forest are modeled by characterizing tree trunks branches and needles leaves with randomly oriented lossy dielectric cylinders whose area and orientation distributions are prescribed the distorted born approximation is used to compute the backscatter at p l and c sar frequencies

morphodynamics of a macrotidal beach abstract an intensive field investigation of hydrodynamic processes processes of sediment entrainment and suspension and morphologic change was carried out on an unprotected macrotidal beach near broome in northwestern australia the spring tide range was 9 5 m waves had heights of 0 5 1 2 m and periods of 9 13 s the beach had an overall concave upward profile with low gradient and dissipative subtidal and low tidal zones and steeper more reflective mid tidal and high tidal zones direct measurement of energy flux dissipation over the intertidal profile showed dissipation rates on the order of 1 2 w m 2 of bed and indicated an approximate balance between shoaling and dissipation of unbroken waves so as to maintain a constant wave height time averaged predictive estimates of wave work over the lunar half cycle for different points on the intertidal profile show similar dissipation rates and reveal a relatively uniform distribution of work over most of the profile but with maxima in the middle of the low tidal zone and over the lower part of the high tidal zone most of the work over the low and mid tidal zones was performed by unbroken shoaling waves rather than by surf zone processes surf zone processes only dominate over the high tidal zone the nature of the surf zone processes varied across the profile as local gradient and degree of reflectivity changed with changing tide level the growth of standing waves and infragravity surf beat oscillations as identified from spectra and cross spectra of surface elevation and currents u and v was inhibited over most of the profile however well developed secondary standing wave energy particularly at infragravity frequencies was observed over the high tidal zone at spring high tide and over the mid tidal zone at neap high tide over the low tidal and subtidal zones strong shore parallel tidal currents were subordinate only to the orbital velocities of unbroken incident waves over the subtidal zone asymmetrical tidal currents skewed toward the north attained maximum speeds of 0 5 m s 1 just after high water field measurements of suspended sediment concentration profiles under broken and unbroken waves showed very good fit to a diffusion model for wave induced sediment suspension and suggested that sediment suspension was probably attributable largely to waves northerly advection of wave suspended sediment by asymmetrical tidal currents over the subtidal and low tidal zones accounted for a net northerly longshore transport the greatest morphologic mobility of the intertidal profile occurred over the lower high tidal and upper mid tidal zones corresponding to the position of the coarsest material and secondary maximum of time averaged wave work and to a beach state intermediate between the reflective and dissipative extremes temporally the greatest mobility of the profile as a whole was observed on the short within tidal cycle time scale net changes over the longest time scale of a lunar half cycle were negligible

terrain and surface modeling using polarimetric sar data features topography and surface slope variations affect perceived scattering polarization state of imaged targets in polarimetric synthetic aperture radar polsar applications accurate modeling of such effects can be used for both polarimetric data correction e g better target classification and topographic feature extraction a framework is established in this paper to model target topography based on analytic relation between surface slopes and polsar data and imagery products polarization orientation angle rotation in particular the developed formalism provides both forward i e polarization rotation from topography and inverse i e terrain slopes from polsar data solutions the synthetic aperture radar sar imaging scenario or mode is assumed to be general with arbitrary parameters e g squint angle and includes multi sar sensors for target terrain modeling

modeling and observation of the radar polarization signature of forested areas to understand radar measurements of forested areas the authors have developed a model of l band 25 cm microwave scattering from a forest the forest floor is layer of nearly vertical dielectric cylinders representing tree trunks above this layer is a second layer consisting of randomly oriented cylinders which represent branches the authors identify several scattering mechanisms and calculate the corresponding stokes matrices which combine to give the total stokes matrix and resulting polarization signature it is found that this simple model permits accurate prediction of the polarization of the scattered waves and that additional mechanisms including the effects of leaves and twigs are not required for the 25 cm observation of the forests studied the authors present measurements of the polarization signature acquired over a forested area and show comparisons with model calculations

the effect of topography on radar scattering from vegetated areas the ways in which radar scattering from vegetated areas is affected by the topography of the surface underneath the vegetation are discussed it is shown using a discrete scatterer model that the dominant scattering mechanism may change drastically when the ground surface is tilted relative to the horizontal for a horizontal ground surface for example the total scattering may be dominated by scattering off the tree trunks followed by a reflection off the ground surface for a relatively small tilt in the ground surface the ground trunk interaction term may be replaced by scattering from the branches alone as the dominant scattering mechanism the effect of the topography is more pronounced for scattering by longer wavelengths and the implications on algorithms designed to infer forest woody biomass and soil and vegetation moisture using polarimetric sar data are discussed the effect of the topography on the scattering behavior from forested areas is illustrated with images acquired by the nasa jpl three frequency polarimetric sar over the black forest in germany

study of wave runup using numerical models and low altitude aerial photogrammetry a tool for coastal management monitoring the impact of sea storms on coastal areas is fundamental to study beach evolution and the vulnerability of low lying coasts to erosion and flooding modelling wave runup on a beach is possible but it requires accurate topographic data and model tuning that can be done comparing observed and modeled runup in this study we collected aerial photos using an unmanned aerial vehicle after two different swells on the same study area we merged the point cloud obtained with photogrammetry with multibeam data in order to obtain a complete beach topography then on each set of rectified and georeferenced uav orthophotos we identified the maximum wave runup for both events recognizing the wet area left by the waves we then used our topography and numerical models to simulate the wave runup and compare the model results to observed values during the two events our results highlight the potential of the methodology presented which integrates uav platforms photogrammetry and geographic information systems to provide faster and cheaper information on beach topography and geomorphology compared with traditional techniques without losing in accuracy we use the results obtained from this technique as a topographic base for a model that calculates runup for the two swells the observed and modeled runups are consistent and open new directions for future research

runup estimations on a macrotidal sandy beach abstract this paper presents a methodological approach to calculate runup from the analysis of morphodynamic conditions on a macrotidal sandy beach the method is based on measurements of the elevation of high tide deposits and on the analysis of morphological and hydrodynamic changes a series of measurements has been carried out on the beach of vougot brittany france under different wave conditions this allowed to assess runup formula effectiveness on a macrotidal sandy beach and to determine the best slope parameters to estimate runup the results suggest that on that macrotidal sandy beach the slope of the active section of the upper beach should be used instead of the entire slope of the foreshore the latter resulting in an underestimation of runup elevations when used in predictive equations from the literature results obtained with widely used equations are relatively well correlated with observed values r2 0 63 an analysis of the relationship between observed runup elevations and various variables has enabled the establishment of a runup estimation formula with a relatively good fit to the study site r2 0 86

a radar backscatter model for discontinuous coniferous forests a radar backscattering model for low to medium density woodland in which each tree is treated as an individual backscatterer is described a forest stand viewed by radar is then an assemblage of scatterers standing on a background in a certain spatial pattern the backscattering components arising from the various intersections of radar beams with the forest stand are calculated separately and their stokes matrices are then added together to achieve the stokes matrix for total backscattering probabilities of radar beams intersecting tree crowns are introduced into the model

temporal and spatial scales of beach profile change duck north carolina abstract an 11 year time series of high resolution beach profile surveys made on an atlantic ocean beach was analyzed for spatial and temporal characteristics of beach profile change approximately 300 profile surveys most extending from the dune to 8 m depth were available for the analysis on each of four cross shore lines together with electronically recorded and statistically processed wave time series from a nearshore gage located seaward of the survey site the profile survey data set was analyzed for such quantities as depth change frequency of depth change general seasonal shape of the profile seasonal depth change and change in the profile produced by extreme storms the morphodynamics of an inner and outer longshore bar were also examined including depth to bar crest bar height and length and speed of bar movement onshore and offshore several properties of depth change were related to wave characteristics representative results were average profile elevation change from 4 m to 4 m was symmetric about the mean sea level shoreline the average spring and autumn profile shapes were almost identical and occurred as transitional states between the summer and winter profile shapes the depth of active profile movement within survey accuracy of about 0 025 m was 4 m for the summer and 6 m for the winter and the 10 year frequencies of maximum absolute depth change in depths of 2 4 6 and 8 m were 1 64 1 38 0 22 and 0 12 m respectively a surprising result was that typical large storms transported sand into the nearshore from the seaward end of the profile from a depth of about 6 8 m

storm generated morphological change and longshore sand transport in the intertidal zone of a multi barred macrotidal beach abstract the morphology hydrodynamics and sediment transport processes of a multi barred macrotidal beach were surveyed over 21 semi diurnal tides the first eight of which were dominated by storm conditions with offshore wave heights ranging from 1 2 to nearly 3 5 m the hydrodynamic conditions prevailing over the intertidal beach showed a rapid response to these storm conditions notably through strong longshore currents that attained peak velocities of 1 6 m s 1 i e over three times the peak spring tide velocities of tide generated longshore currents during calm conditions the bars showed no cross shore migration during the storm events morphological mapping of the beach tracer dispersal patterns and calculations of potential sand transport rates using the energetics based model of bailard bailard j a 1981 an energetics total load sediment transport model for a plane sloping beach j geophys res 86 10938 10954 showed significant longshore sand transport as well as longshore migration of an intertidal drainage channel these longshore movements were bi directional responded to changes in incident wind and wave directions and involved wave stirring coupled with longshore advection of sand along the bar crests in particular strong trough and cross shore channel flows also led to the longshore migration of crescentic dunes the longshore sediment movements were embedded in a cross shore gradient associated with increasing overall profile mobility from the lower to the upper beach in response to wave shoaling and post breaking processes assessed through examination of the relative wave height hs h 1 based on the relationship between significant wave height hs and water depth h longshore sediment transport is a characteristic feature of the long term evolution of wissant bay which is dominated by a net northeastward residual sand transport within a bay sediment cell characterised by significant updrift erosion and downdrift accumulation longshore transport should be considered as an essential element of the morphodynamics of bar trough beaches subject to large tidal ranges and significant wind stress but there is a need for a better understanding of the role of wind stress on longshore currents in the shallow intertidal zone of these beaches

unsupervised classification of scattering behavior using radar polarimetry data the use of an imaging radar polarimeter data for unsupervised classification of scattering behavior is described by comparing the polarization properties of each pixel in an image to that of simple classes of scattering such as even number of reflections odd number of reflections and diffuse scattering for example when this algorithm is applied to data acquired over the san francisco bay area in california it classifies scattering by the ocean as being similar to that predicted by the class of odd number of reflections scattering by the urban area as being similar to that predicted by the class of even number of reflections and scattering by the golden gate park as being similar to that predicted by the diffuse scattering class it also classifies the scattering by a lighthouse in the ocean and boats on the ocean surface as being similar to that predicted by the even number of reflections class making it easy to identify these objects against the background of the surrounding ocean

statistical and spatial properties of forest clutter measured with polarimetric synthetic aperture radar sar the purpose of this study was to assess the characteristics of the polarimetric radar clutter collected over various types of vegetation and to evaluate the potential utility of various measures for classifying vegetated terrain it utilized airborne radar data collected in october 1988 of pure and mixed stands of jack pine and aspen located in central minnesota and data collected in august 1989 of forested areas surrounding durham nc the measured parameters are the polarimetric signature a statistical distribution shape parameter and the texture autocorrelation function a method is presented for calculating the texture autocorrelation from single look complex sar imagery comparison of parameters from different clutter types at a variety of frequency polarization and incidence angle combinations showed that different terrain types exhibit unique polarimetric statistical and spatial properties

investigation of multifrequency multipolarization radar signatures of rain cells over the ocean using sir c x sar data radar signatures of rain cells are investigated using multifrequency multipolarization synthetic aperture radar sar images acquired from the space shuttle endeavour during the spaceborne imaging radar c x band sar sir c x sar missions in april and october 1994 in sir c x sar images radar signatures of rain cells over the ocean usually consist of irregularly shaped bright and dark patches that strongly depend on radar frequency and polarization the radar signatures of rain cells observed in sir c x sar imagery of the ocean originate from 1 the scattering and attenuation of the microwaves by raindrops and ice particles in the atmosphere and 2 the modification of the sea surface roughness induced by the impact of raindrops and by wind gusts associated with rain cells raindrops impinging on the sea surface generate ring waves which enhance the sea surface roughness but they also generate turbulence in the upper water layer which reduces the sea surface roughness depending on the radar wavelength ocean areas struck by rain can have higher or lower normalized radar cross section nrcs than the surrounding rain free area in ocean areas where heavy rain is impinging on the sea surface the x and c band nrcs is usually enhanced and the l band nrcs is reduced from the phase difference between the horizontally and vertically copolarized signals estimates of the rain rate are obtained the present analysis shows further that the presently used wind speed retrieval algorithms for the scatterometers aboard the ers and adeos satellites may yield biased wind fields if several rain cells lie within a scatterometer resolution cell

polarimetric sar data compensation for terrain azimuth slope variation this paper addresses the problem of polarimetric sar polsar data correction for changes in radar cross sections which are caused by azimuth slopes most radiometric slope corrections remove slope effects to account for the effective scattering pixel area however few studies address the slope effect on the radar cross section as a function of polarization states the authors propose two approaches to compensate for this azimuth slope effect for polsar data in the first approach the digital elevation model dem obtained from interferometric sar or from other means is used to estimate orientation angles and in the second approach orientation angles are derived directly from the polsar data they have developed three new methods to implement this second approach one is based on the right right and left left circular polarizations and the other two are based on cloude s and huynelt s decompositions the results are compared with the original polarization signature method using the dem generated orientation angles as the reference polsar data is then compensated using the derived orientation angles significant changes were observed in many elements of the coherency matrix the compensated polsar data should improve the accuracy of geophysical parameter estimation techniques nasa jpl airsar data for an area in central california is used for illustration

wave transformation across the inner surf zone sea and swell wave heights observed on transects crossing the mid and inner surf zone on three beaches a steep concave up beach a gently sloped approximately planar beach and a beach with an approximately flat terrace adjacent to a steep foreshore were depth limited i e approximately independent of the offshore wave height consistent with previous observations the wave evolution is well predicted by a numerical model based on the one dimensional nonlinear shallow water equations with bore dissipation the model is initialized with the time series of sea surface elevation and cross shore current observed at the most offshore sensors located about 50 to 120 m from the mean shoreline in mean water depths 0 80 to 2 10 m the model accurately predicts the cross shore variation of energy at both infragravity nominally 0 004 f 0 05 hz and sea swell here 0 05 f 0 18 hz frequencies in models of surf zone hydrodynamics wave energy dissipation is frequently parameterized in terms of s the ratio of the sea swell significant wave height to the local mean water depth the observed and predicted values of s increase with increasing beach slope and decreasing normalized by a characteristic wavenumber k water depth kh and are well correlated with kh a measure of the fractional change in water depth over a wavelength errors in the predicted individual values of s are typically less than 20 it has been suggested that infragravity motions affect waves in the sea swell band and hence s but this speculation is difficult to test with field observations numerical simulations suggest that for the range of conditions considered here s is insensitive to infragravity energy levels

a microwave scattering model for layered vegetation a microwave scattering model was developed for layered vegetation based on an iterative solution of the radiative transfer equation up to the second order to account for multiple scattering within the canopy and between the ground and the canopy the model is designed to operate over a wide frequency range for both deciduous and coniferous forest and to account for the branch size distribution leaf orientation distribution and branch orientation distribution for each size the canopy is modeled as a two layered medium above a rough interface the upper layer is the crown containing leaves stems and branches the lower layer is the trunk region modeled as randomly positioned cylinders with a preferred orientation distribution above an irregular soil surface comparisons of results obtained using this model with measurements from deciduous and coniferous forests show good agreement at several frequencies for both like and cross polarizations

separation of vegetation and rock signatures in thematic mapper and polarimetric sar images abstract a technique for separating classes of surface roughness and vegetation in semiarid regions using polarimetric synthetic aperture radar sar and thematic mapper tm data has been developed we conclude that polarimetric sar data may be used to separate areas with vegetation cover where one suite of model inversions may be applicable for derivation of surface roughness in more vegetated regions visible near infrared nir data will provide a mechanism for determining the relative contribution of vegetation to multiple scattering in the sar data thus the synergistic use of the two data sets provides a more complete characterization of surface units and cover this result while important for geologic interpretations is even more critical when trying to monitor dielectric constant variations related to changes in moisture content of soil and vegetation cover in arid to semiarid regions a strategy for automating a procedure for measurement of surface roughness is proposed

measurement of topography using polarimetric sar images a processing technique for polarimetric synthetic aperture radar sar data has been developed which produces profiles of terrain slopes and elevations in the azimuthal or along track direction this technique estimates the average shift in orientation angle of copolarization backscatter caused by azimuthal tilts of the scattering plane using p band data tests of this technique have been made for an area in the black forest near villingen schwenningen in baden wurttemberg germany the radar measured slope and derived elevation profiles have low rms errors and high correlation values when compared with a stereo photograph digital elevation map dem for the area this algorithm is capable of adaptively making transitions from the forested areas to nearby regions with open terrain subsequent tests of the algorithm have been conducted using polarimetric sar l band data for a mountainous nonforested region in the mojave desert ft irwin ca where an accurate dem also was available complete elevation and slope mapping of the terrain in two dimensions using this technique is possible when azimuthal elevation profiles are produced throughout the range extent of the sar image

modeling interferometric sar features of forest canopies over mountainous area at landscape scales high quality interferometric synthetic aperture radar insar data have become more available in recent years with insar missions such as the tandem x theoretical coherent backscattering models of forest canopies at landscape scales are necessary for understanding the relationship between positions of scattering phase center extracted from insar data and spatial structures of forest stands growing on complex mountainous terrain unlike most existing scattering models of forest canopies that focus on the prediction of the scattering behavior within a pixel a new model referred to as landsar was developed to fully account for compound effects of forest spatial structure terrain and geometrical distortion caused by slant range imaging on the scattering phase center the landsar model was validated over a mountainous forest scene about 8 8 km by 9 5 km imaged by an airborne laser scanner the interferogram flattened interferogram coherence unwrapped phase and digital surface model were successfully extracted from simulated insar data that have been processed as real insar data the effects of wavelength baseline length land cover and terrain features on decorrelation of simulated insar data were consistent with theoretical expectations both the height of the scattering phase center and the penetration depth were strongly correlated with forest heights these results demonstrated that the landsar successfully modeled the insar features of forest canopies over a mountainous area at landscape scales

dynamics of saltwater intrusion in coastal channels the dynamic behavior of saltwater intrusion in coastal channels with small tidal range is often dependent upon motions induced by freshwater inflow from the upstream drainage basin in coastal louisiana the salinity distribution in channels encompasses well mixed partially stratified and highly stratified phenomena a two dimensional laterally averaged and semi implicit hydrodynamic model coupled with a salt flux transport model is developed to quantify the saltwater intrusion due to interactions of freshwater discharge tidal activity prevailing wind and the density gradient caused by variations in salinity in the model the coefficients of eddy and salt diffusivity are varied as functions of space and time the values of coefficients fitted from the field data are comparable to those reported by others the numerical model calibrated with independent field data sets is then applied to predict the changes in the patterns of salinity distribution in channels resulting from changes in channel dimensions both computed and field results reveal that the salinity intrusion in coastal channels is highly dependent on the freshwater inflow and the channel dimensions

compensation of terrain azimuthal slope effects in geophysical parameter studies using polarimetric sar data abstract the existence of significant terrain relief reduces the accuracy of algorithms intended to extract geophysical parameters from polarimetric synthetic aperture radar sar images for this reason most inversion studies attempting to estimate biomass crop type snow cover surface roughness or soil moisture from sar data are best done in areas of flat earth in areas which require compensation for topography limited corrections have been made in the past for range slopes using a coregistered digital elevation model dem no corrections have been made however for terrain slope induced polarimetric effects in the azimuthal or along track direction recent methods using polarimetric sar data of measuring terrain slopes in the azimuthal direction have been developed this article presents an algorithm to use these slope estimates to compensate for the effects of azimuthal terrain slopes the algorithm involves rotation of the polarimetric covariance matrix to achieve maximum azimuthal symmetry evidence is given to substantiate the degree to which azimuthal slope effects have been removed from the data nasa airsar p l and c band data obtained for open terrain in death valley national park california 1994 are used to evaluate the compensation algorithm

studies of multibaseline spaceborne interferometric synthetic aperture radars the authors have utilized a set of seasat synthetic aperture radar sar data that were obtained in nearly repeat ground track orbits to demonstrate the performance of spaceborne interferometric sar insar systems an assessment of the topography measurement capability is presented a phase measurement error model is described and compared with the data obtained at various baseline separations and signal to noise ratios finally the implications of these results on future spaceborne insar design are discussed

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

multipolarization sar data for surface feature delineation and forest vegetation characterization this paper presents the utility of multipolarization synthetic aperture radar sar data for surface feature delineation and forest vegetation characterization three channels of ratioed data vv hh vh hh and vh vv are generated from the hh vv and vh polarization data v vertical h horizontal the ratioed data are linearly stretched to yield a digital number within a range of 0 to 255 the techniques for reducing sar speckle noise and for measuring the degree of separation are discussed for surface feature delineation the results indicate that cross polarization as well as cross polarization ratioed data better delineate those surface features that are difficult to separate by like polarization data the results suggest using a median value filtering technique to reduce within plot data fluctuation to increase the separability measure for forest vegetation characterization the results indicate that multipolarization sar data may be used to estimate forest properties such as total tree biomass basal area and tree height

rain footprints on c band synthetic aperture radar images of the ocean revisited abstract it is well known that rain leaves footprints on the sea surface that sometimes become visible on synthetic aperture radar sar images rain cells can easily be detected on sar images at all radar frequencies when they are associated with a downdraft pattern but rain cells are not always associated with downdraft and rain can also occur in other forms as stratified rain rain bands and squall lines it turns out that radar signatures of rain at c band are much more complex than at l or x band radar and that it is particularly difficult to identify unambiguously rain events on c band sar images acquired over the ocean this is because c band lies in the transition region where raindrops impinging onto the sea surface can increase usually or decrease the backscattered radar power and where volume scattering and attenuation by rain drops in the atmosphere are not always negligible at very high rain rates in order to get an insight into the physical mechanisms causing the c band radar signatures of rain we first revisit results obtained from historic laboratory and field experiments and multi frequency multi polarization sar data acquired during the sir c x sar spaceshuttle mission in 1994 then we analyze several c band sar images acquired by the european satellites envisat and sentinel 1a and the canadian satellite radarsat 2 and compare them whenever possible with quasi coincident and collocated weather radar images the observational data show that at low to medium rain rates the main physical mechanism causing c band radar signatures of rain is bragg scattering at ring waves generated by the rain drops impinging onto the sea surface which increase the radar backscatter however areas of increased radar backscatter are often accompanied by adjacent areas of decreased radar backscatter which is due to attenuation of the bragg waves by turbulence also generated by the impinging rain drops furthermore we present a full polarimetric radarsat 2 sar image of a rain cell together with a polarimetric decomposition analysis which shows that the c band radar signature of a rain cell is caused by surface scattering the observation show that radar signatures of rain cells often contain segments where the co polarized as well the cross polarized radar backscatter are strongly enhanced which indicates non bragg scattering contributions to the scattering process furthermore the polarimetric decomposition analysis shows that the c band radar signature of a rain cell is dominated by surface scattering possible mechanisms like scattering at splash products are discussed whether the normalized radar cross section nrcs due to rain is increased or decreased depends on rain rate wind speed incidence angle and history of the rain event at low to moderate wind speeds 10 m s 1 and low to high rain rates but

pocket beach hydrodynamics the example of four macrotidal beaches brittany france during several field experiments measurements of waves and currents as well as topographic surveys were conducted on four morphologically contrasted macrotidal beaches along the rocky iroise coastline in brittany france these datasets provide new insight on the hydrodynamics of pocket beaches which are rather poorly documented compared to wide and open beaches the results notably highlight a cross shore gradient in the magnitude of tidal currents which are relatively strong offshore of the beaches but are insignificant inshore despite the macrotidal setting the hydrodynamics of these beaches are thus totally wave driven in the intertidal zone the crucial role of wind forcing is emphasized for both moderately and highly protected beaches as this mechanism drives mean currents two to three times stronger than those due to more energetic swells when winds blow nearly parallel to the shoreline moreover the mean alongshore current appears to be essentially wind driven wind waves being superimposed on shore normal oceanic swells during storms and variations in their magnitude being coherent with those of the wind direction we also found evidence for the contribution of infragravity waves to the formation of an intertidal sand bar through prolonged duration of swash processes at the same beach level and to the development of beach cusps but not to their initiation for which the observed standing edge wave pattern may have been enhanced by the enclosed pocket beach setting the paper highlights some of the specificities of pocket beach with regards to their hydrodynamics and morphodynamics more detailed observations would be needed however prior to a more comprehensive review

a generalized radar backscattering model based on wave theory for multilayer multispecies vegetation a generalized radar scattering model based on wave theory is described the model predicts polarimetric radar backscattering coefficients for structurally complex vegetation comprised of multiple species and layers compared to conventional two layer crown trunk models modeling of actual forests has been improved substantially allowing better understanding of microwave interaction with vegetation the model generalizes an existing single species discrete scatterer model and by including scattering and propagation effects through judiciously defined vegetation layers enables its application to an arbitrary number of species types the scatterers within each layer are modeled as finite cylinders or disks having arbitrary size density and orientation as in the predecessor model the distorted born approximation is used to represent the propagation through each layer while scattering from each is modeled as a linear superposition of scattering from its respective random collection of scatterers interactions of waves within and between each layer and direct scattering from the ground are accounted for validation of the model is presented based on its application to 23 wooded savanna sites located in queensland australia and comparison with advanced land observing satellite alos phased arrayed l band synthetic aperture radar palsar and national aeronautics and space administration nasa jet propulsion laboratory jpl airborne synthetic aperture radar airsar data results indicate good agreement between simulated and actual backscattering coefficients particularly at hh and vv polarizations more discrepancies are found at hv polarizations and can be explained by uncertainties in the knowledge of input parameters such as inaccuracies in the surface model surface roughness parameterization and soil moisture

topographic mapping using radar interferometry processing techniques a new processing algorithm for the nasa jpl topsar topographic radar mapper is described it incorporates extensive motion compensation features as well as accurate three dimensional target location algorithm the processor applies an algorithm to resolving the absolute phase ambiguity this allows rectified height maps to be generated without any use of ground reference points the processor was tested using data acquired with extreme aircraft motion so that performance could be evaluated under adverse conditions the topographic maps generated by the radar were compared to digital elevation models dems derived using conventional optical stereo techniques in one region the rms elevation deviations measured were less than the specified dem accuracy and in the region covered by the more accurate dem errors varied from 2 2 m rms in relatively flat terrain up to 5 0 m in mountainous area the rms difference between radar and dem elevation over the 6 5 km by 22 km area covered by the more accurate dem was 3 6 m

the dynamics of a river bay delta system an analysis has been made to aid our understanding of various phenomena associated with turbulent plane jets that issue from river outlets and discharge into quiescent bays an integrated form of the hydrodynamic equations of flow continuity and momentum balance coupled with advective diffusion mass transport equations has been formulated into a two dimensional spatial domain closed form analytical solutions are obtained with the aid of similarity functions for the velocity and sediment concentration profiles a numerical procedure for estimating the areal and volume deposition of the delta sediments is presented the atchafalaya river delta a newly developing delta in the south central louisiana coast is used to illustrate analytical techniques the results of analytical predictions are compared with the results predicted by other statistical and generic approaches an agreement is found a sensitivity analysis is performed to assess the relative importance of various parameters in the river bay delta system

setup and swash on a natural beach wave setup and swash statistics were calculated from 154 runup time series measured on a moderately steep beach under incident waves varying from 0 4 to 4 0 m significant wave height when scaled by the incident wave height setup swash height and total runup the sum of setup and half the swash height were found to vary linearly with the surf zone similarity parameter 0 h0 l0 1 2 the foreshore slope appeared the appropriate value for the calculation of 0 although the setup data showed some influence of an offshore bar at low tide for low irribaren numbers the swash height in the incident frequency band becomes saturated while for high irribaren numbers no such signs of saturations were seen thus the infragravity band appears to become dominant in the swash below some value of 0 for these data that value is approximately 1 75 although there is considerable scatter associated with that estimate

a simple model for the spatially variable coastal response to hurricanes abstract the vulnerability of a beach to extreme coastal change during a hurricane can be estimated by comparing the relative elevations of storm induced water levels to those of the dune or berm a simple model that defines the coastal response based on these elevations was used to hindcast the potential impact regime along a 50 km stretch of the north carolina coast to the landfalls of hurricane bonnie on august 27 1998 and hurricane floyd on september 16 1999 maximum total water levels at the shoreline were calculated as the sum of modeled storm surge astronomical tide and wave runup estimated from offshore wave conditions and the local beach slope using an empirical parameterization storm surge and wave runup each accounted for 48 of the signal the remaining 4 is attributed to astronomical tides indicating that wave driven process are a significant contributor to hurricane induced water levels expected water levels and lidar derived measures of pre storm dune and berm elevation were used to predict the spatially varying storm impact regime swash collision or overwash predictions were compared to the observed response quantified using a lidar topography survey collected following hurricane landfall the storm averaged mean accuracy of the model in predicting the observed impact regime was 55 4 a significant improvement over the 33 3 accuracy associated with random chance model sensitivity varied between regimes and was highest within the overwash regime where the accuracies were 84 2 and 89 7 for hurricanes bonnie and floyd respectively the model not only allows for prediction of the general coastal response to storms but also provides a framework for examining the longshore variable magnitudes of observed coastal change for hurricane bonnie shoreline and beach volume changes within locations that experienced overwash or dune erosion were two times greater than locations where wave runup was confined to the foreshore swash regime during hurricane floyd this pattern became more pronounced as magnitudes of change were four times greater within the overwash regime than in the swash regime comparisons of pre storm topography to a calm weather survey collected one year after hurricane floyd s landfall show long term beach volume loss at overwash locations here the volume of sand eroded from the beach was balanced by the volume of overwash deposits indicating that the majority of the sand removed from the beach was transported landward across the island rather than being transported offshore in overwash locations sand was removed from the nearshore system and unavailable for later beach recovery resulting in a more permanent response than observed within the other regimes these results support the predictive capabilities of the storm scaling model and illustrate that the impact regimes provide a framework for explaining the longshore variable coastal response to hurricanes

the coupling of bay hydrodynamics to sediment transport and its implication in micro tidal wetland sustainability abstract to investigate bay hydrodynamics and its impacts on the adjacent micro tidal wetland sustainability hourly measurements of wave tidal current and benthic suspended sediment concentration in summer winter and spring of 2015 2016 were conducted in fourleague bay louisiana usa high temporal resolution data indicate that benthic suspended sediment resuspension had a dominant periodicity of 4 8 d which was mainly caused by wind driven waves sediment flux reached 28 g m 2 s 1 during events net sediment flux direction is northwestward in summer and southeastward in winter and spring potential depth integrated sediment flux to surrounding wetland varied within 0 500 g m 1 s 1 seasonal variations of river discharge and wind direction particularly speed 3 m s 1 dominated potential sediment contribution from the bay to the surrounding wetland three sediment transport regimes were delineated bypassing season resuspension accumulation season and combined bypassing and resuspension accumulation season this study couples bay hydrodynamics to the sediment transport processes and sustainability of adjacent wetlands in a micro tidal environment it sheds light on the understanding of natural feedback mechanisms and how estuarine marsh system survive high relative sea level rising scenario in micro tidal environment which could aid in the design of future ecological engineering restoration strategies

measurement of ocean surface slopes and wave spectra using polarimetric sar image data abstract methods have been investigated which use fully polarimetric synthetic aperture radar sar image data to measure ocean slopes and wave spectra independent techniques have been developed to measure wave slopes in the sar azimuth and range directions the azimuth slope technique in particular is a more direct measurement than conventional intensity based backscatter cross section measurements in the azimuth direction wave induced perturbations of the polarimetric orientation angle are used to sense the wave slopes in the range direction a new technique involving the alpha parameter from the cloude pottier h a entropy anisotropy and averaged alpha polarimetric scattering decomposition theorem is used to measure slopes both measurement types are sensitive to ocean wave slopes and are directional taken together they form a means of using polarimetric sar polsar image data to make complete measurements of either ocean wave slopes or directional wave spectra these measurements must still contend with fundamental nonlinearities in the sar image processing i e azimuth direction velocity bunching that are due to wave velocity and acceleration effects nasa jpl airsar l and p band data from california coastal waters were used in the studies wave parameters measured using the new methods are compared with those developed using both conventional sar intensity based methods and with in situ noaa national data center buoy measurement products

topography retrieval from single pass polsar data based on the polarization dependent intensity ratio at present many polarimetric synthetic aperture radar polsar remote sensing applications still perform radio metric terrain correction whereas other types of terrain slope analysis rely on shuttle radar topography mission and advanced spaceborne thermal emission and reflection radiometer digital elevation model dem databases however the terrain relief characteristics present in fully polsar images can also be used for topography retrieval from single flight data based on the analysis of the polarization signature peak shift we propose a new topography retrieval algorithm based on the polarization dependent intensity ratio the intensity term conforms to both the polarimetric orientation angle shift model and the lambertian scattering model which is refined for synthetic aperture radar sar imaging geometry this is useful in avoiding solving an ill conditioned problem and it is more practical than considering the two models independently another key idea of this algorithm is the derivation of a second order residual error equation for revising the ground range slope error with homogeneous media using the full multigrid fmg technique furthermore the fake topographic relief effect induced by geophysical terrain variations is also considered and reduced by including an bar alpha scattering angle based weighting coefficient in the second order residual error equation in addition a first order residual error equation combined with tie points is proposed for calculating the least squares estimation of the height from slope integration by fmg national aeronautics and space administration jet propulsion laboratory airsar and uavsar l band polsar and interferometry sar dem data are used to illustrate and validate this algorithm our results demonstrate the high potential of this method for employing a low resolution dem to match the corresponding high resolution polsar data

analysis and evaluation of the nasa jpl topsar across track interferometric sar system we have evaluated the accuracy of digital elevation models dem s generated by the jpwnasa topsar synthetic aperture radar interferometer instrument by acquiring topographic radar data in the summer of 1992 over the national training center near ft irwin california and comparing the measurements to a very accurate digital elevation model derived for this area by the us army topographic engineering center tec fiducial corner reflectors were deployed in the area and their locations were determined to cm accuracy by the defense mapping agency dma dem s generated from the acquired radar data were rotated and translated to precisely overlay the reference dem allowing an analysis of the achieved height accuracy we present here a detailed description of horizontal and vertical errors and their characteristics the standard deviation measured over a 5 6 x 7 km area was approximately 2 m the corresponding figures for relatively flat areas were in the 1 2 meter range and for mountainous areas in the 2 3 meter range consistent with theoretical expectations we also discuss key factors that presently limit the system performance