assessment of radiometric correction techniques in analyzing vegetation variability and change using time series of landsat images abstract the homogeneity of time series of satellite images is crucial when studying abrupt or gradual changes in vegetation cover via remote sensing data various sources of noise affect the information received by satellites making it difficult to differentiate the surface signal from noise and complicates attempts to obtain homogeneous time series we compare different procedures developed to create homogeneous time series of landsat images including sensor calibration atmospheric and topographic correction and radiometric normalization two seasonal time series of landsat images were created for the middle ebro valley ne spain covering the period 1984 2007 different processing steps were tested and the best option selected according to quantitative statistics obtained from invariant areas simultaneous medium resolution images and field measurements the optimum procedure includes cross calibration between landsat sensors atmospheric correction using complex radiative transfer models a non lambertian topographic correction and a relative radiometric normalization using an automatic procedure finally three case studies are presented to illustrate the role of the different radiometric correction procedures when analyzing and explaining gradual and abrupt temporal changes in vegetation cover as well as temporal variability we have shown that to analyze different vegetation processes with landsat data it is necessary to accurately ensure the homogeneity of the multitemporal datasets by means of complex radiometric correction procedures failure to follow such a procedure may mean that the analyzed processes are non recognizable and that the obtained results are invalid

numerical modeling of low frequency wave dynamics over a fringing coral reef abstract low frequency infragravity wave dynamics on a fringing coral reef were investigated using the numerical model xbeach roelvink et al 2009 first the skill of the model was evaluated in one and two dimensions based on its predictions of short waves 0 04 0 2 hz infragravity waves 0 004 0 04 hz and water level measurements tidal and wave setup obtained during a 2009 field study at ningaloo reef in western australia the model calibration was sensitive to friction coefficients for short waves and current infragravity bed friction which were assumed independent in this model study although the one dimensional cross shore model captured the gradients in the dominant hydrodynamic processes at the site a high current ig bed friction coefficient was required this resulted in an overestimation and a phase lag between the observed and predicted wave setup signal in the two dimensional model a lower more realistic current infragravity wave friction coefficient was required to achieve optimum performance due to the presence of significant reef and lagoon mean flows in the model which led to reduced setup across the reef the infragravity waves were found to propagate from the surf zone across the reef in a dominantly cross shore direction towards the shore but with substantial frictional damping the infragravity waves were strongly modulated also over the reef by tidal depth variations primarily due to the variability in frictional dissipation rates when the total water depth over the reef varied two mean wave driven circulation cells were observed in the study area with cross shore flow becoming more alongshore dominated before exiting the system via the two channels in the reef the results reveal that short waves dominated bottom stresses on the forereef and near the reef crest however inside the lagoon infragravity waves become increasingly dominant accounting up to 50 of the combined bottom stresses

a numerical study of circulation in a coastal reef lagoon system 1 a coupled wave circulation numerical model was used to simulate the distribution of wave energy as well as the circulation induced by wave breaking wind and tidal forcing within a coral reef system in kaneohe bay oahu hawaii modeled wave current and wave setup fields were compared with field measurements collected on the forereef reef flat and reef channels and in the lagoon over a 4 week period the predicted wave height transformation across the reef lagoon system was in good agreement with field observations using single parameter spatially uniform values to describe both wave breaking and frictional dissipation the spatial distribution of the resulting wave setup field drove a persistent wave driven flow across the reef flat that returned to the ocean through two deeper channels in the reef both the magnitude and direction of these currents were well described using a spatially uniform hydraulic roughness length scale notably the model lends support to field observations that setup within the coastally bounded lagoon was a substantial fraction of the maximum setup on the reef 60 80 which generated relatively weak cross reef wave driven flows 10 20 cm s 1 compared with reefs having mostly unbounded lagoons e g many atolls and barrier reefs numerical experiments conducted using lagrangian particle tracking revealed that residence times within kaneohe bay are extremely heterogeneous typically ranging from 1 month within its sheltered southern lagoon

vegetation driven morphodynamic adjustments of a sand bed vegetation is ubiquitous in riverine and coastal environments but the physics governing morphodynamic interactions modulated by vegetation are still poorly understood here we use a simple experiment to study the impact of a vegetated patch on the morphodynamics of a sand bed we show that the vegetation patch reduces the sediment transport capacity of the flow and that the topography responds to this by an increase of the bed slope to accommodate the upstream sediment supply final bed slope and adjustment time scale depend on the ratio between the grain related shear stress and the total shear stress this demonstrates the mechanisms underlying a direct morphodynamic response to the presence of a vegetation patch

a framework for understanding drag parameterizations for coral reefs 1 in a hydrodynamic sense a coral reef is a complex array of obstacles that exerts a net drag force on water moving over the reef this drag is typically parameterized in ocean circulation models using drag coefficients cd or roughness length scales z0 however published cd for coral reefs span two orders of magnitude posing a challenge to predictive modeling here we examine the reasons for the large range in reported cd and assess the limitations of using cd and z0 to parameterize drag on reefs using a formal framework based on the 3 d spatially averaged momentum equations we show that cd and z0 are functions of canopy geometry and velocity profile shape using an idealized two layer model we illustrate that cd can vary by more than an order of magnitude for the same geometry and flow depending on the reference velocity selected and that differences in definition account for much of the range in reported cd values roughness length scales z0 are typically used in 3 d circulation models to adjust cd for reference height but this relies on spatially averaged near bottom velocity profiles being logarithmic measurements from a shallow backreef indicate that z0 determined from fits to point measurements of velocity profiles can be very different from z0 required to parameterize spatially averaged drag more sophisticated parameterizations for drag and shear stresses are required to simulate 3 d velocity fields over shallow reefs in the meantime we urge caution when using published cd and z0 values for coral reefs

hydraulic resistance of submerged flexible vegetation the main research objective consisted in analysing the influence of roughness caused by aquatic vegetation av in particular submerged macrophytes on the overall flow field these plants are highly flexible and behave differently depending on the flow situation they also react substantially to the flow field and thus the roughness becomes variable and dynamic conventional flow formulas such as the manning or the strickler formula are one dimensional and based on integral flow parameters they are not suitable for quantifying the roughness of av because the flow is complex and more dimensional due to the variable behaviour of the plants therefore the present investigation concentrates on the definition of a characteristic hydraulic roughness parameter to quantify the resistance of av within this investigation laboratory experiments were carried out with three different types of av chosen with respect to varying plant structures as well as stem lengths velocity measurements above these plants were conducted to determine the relationship between the hydraulic roughness and the deflected plant height the deflected plant height is used as the geometric roughness parameter whereas the equivalent sand roughness based on the universal logarithmic law modified by nikuradse was used as hydraulic roughness parameter the influence of relative submergence on the hydraulic roughness was also analysed the analysis of the velocity measurements illustrates that equivalent sand roughness and zero plane displacement of the logarithmic law are correlated to the deflected plant height and are equally to this height

flow velocity measurements in vegetated channels understanding of the hydraulics of flow over vegetation is very important to support the management of fluvial processes in this paper the flow over flexible bottom vegetation is experimentally studied a two dimensional acoustic doppler velocimeter is used to measure the local flow velocities for different vegetation concentrations discharges and flume slopes the influence of vegetation concentration and the depth vegetation height ratio on the measured velocity profiles is analyzed all measured velocity distributions are s shaped and exhibit a three zone profile the relationship between the velocity distribution and the turbulence intensity distribution is also analyzed the characteristics inflection point maximum value asymptotes of the measured velocity distributions and the results of the previous investigators are used to select an analytical expression for the shape of the velocity profile a theoretical velocity profile is deduced using the classical prandtl s mixing length approach with a new expression for the mixing length the deduced four coefficient profile allows description of the flow both inside and above the vegetation the physical and geometrical meaning of the four coefficients are also shown doi 10 1061 asce 0733 9429 2002 128 7 664 ce database keywords velocity profile vegetation channel flow

estimation of high resolution sediment concentration profiles in bottom boundary layer using pulse coherent acoustic doppler current profilers abstract the capability of two acoustic profilers sontek s 1 5 mhz pulse coherent acoustic doppler profiler pc adp and rdi s 600 khz acoustic doppler current profiler adcp with pulse coherent mode was evaluated for estimating high resolution suspended sediment concentration ssc profiles in bottom boundary layer in the laboratory measurements with a pc adp two types of sediments were tested to study acoustic responses to grain size a natural sediment sample from clay bank a mixture of clay and very fine sand showed a good linear relationship between range corrected volume scattering s v and backscattered strength e until ssc increased up to about 10 g l 1 in contrast a commercially available kaolinite exhibited earlier signal saturation and non unified linear regressions between s v and e most likely because the particle size is much smaller than the transmitted acoustic wavelength using a pulse coherent adcp the field measurement results from mobile bay alabama showed that the acoustically derived ssc profiles were well matched with the optically derived outcomes although slight discrepancies were noted the overestimation of acoustically derived ssc near the bed may be related to the side lobe interference near the bed and the enhanced acoustic sensitivity by coarser particles and denser aggregates eroded from the bed mean absolute error of acoustic estimates was within 4 1 7 3 of the optically derived ssc range which is attributable to the different acoustic and optical scattering responses to given sediment size spectra despite some error sources in acoustic inversion the results from laboratory and field experiments suggest that the pulse coherent acoustic profiler is able to reveal the evolution of in situ near bed ssc profiles with high vertical and temporal resolutions

the dynamics of infragravity wave transformation over a fringing reef a 3 week field study was conducted to investigate the dynamics of low frequency infragravity wave motions over a fringing reef at ningaloo reef western australia short period wave motions 0 04 0 2 hz were observed to dissipate on the reef crest beyond which infragravity wave motions 0 004 0 04 hz gradually dominated toward the lagoon however both the short waves and the infragravity waves were relatively small both 0 3 m on the reef flat owing to the shallow water depth 2 m the results revealed that the surf zone generation of free infragravity wave motions on the steep 1 20 fore reef slope was dominated by breakpoint forcing as opposed to shoaling bound waves which was also supported by detailed numerical simulations of the generation process this is consistent with theory suggesting the efficiency of the breakpoint forcing mechanism should be high in this steep slope regime shoreward propagating infragravity waves traveled across the reef but were damped by bottom friction dissipation however this was at a rate much smaller than experienced by the residual short waves with these rates of frictional dissipation also strongly dependent on the water depth over the reef the infragravity wave heights increased at higher water levels and hence were strongly modulated by the tide due to the strong dissipation of infragravity waves over this wide and shallow reef that is hydraulically rough any seaward propagating infragravity waves that reflected at the shoreline were small leading to the dominance of progressive shoreward propagating infragravity wave motions throughout the reef and lagoon

using landsat 5 thematic mapper and digital elevation data to determine the net radiation field of a mountain glacier abstract an accurate evaluation of glacier energy balance requires a precise knowledge of surface cover albedo and emittance usually these values are acquired from field measurements however the microclimatological effects in mountainous terrain greatly limit the potential for spatial extrapolation of such a set of values this study overcomes the problem by using the upward radiance values registered on landsat 5 thematic mapper tm images and information on the geometry of ter terrain extracted from a digital elevation model dem studies were performed in the athabasca glacier basin one of the major glacier outlets of the columbia icefield in the canadian rocky mountains the methodology is composed first of an automated procedure for the physiographic description of the glacierized basin cover type elevation slope aspect horizon profiles sky view factor and the level of enclosing topography in order to calculate the effects of topography on the radiation balance for each 30 m pixel because glacier surface covers usually have high reflective behaviors or distinct emission patterns this study puts special emphasis on modelling the amount of terrain reflected or terrain emitted radiation received on a particular surface second the topographic correction is applied to values of irradiance computed using the lowtran 6 code a spectrally based radiative transfer model and atmospheric radiosonde measurements of the vertical temperature air pressure and relative humidity profiles the measured upward radiance values from tm corrected for path effects are used to calculate surface cover albedo and brightness temperature third the daily net radiation field for snow and ice covers is computed to illustrate the contribution of the estimated surface radiative parameters to the glacier snow and ice melt analysis the resultsshow that the irradiance values are accurately modelled within 10 of the radiattion values acquired from a field pyranometer the calculated glacial surface cover reflectance and albedo values compare favorably to published information whereas the measured surface brightness temperature is well within the expected range of values

sediment transport and shear stress partitioning in a vegetated flow vegetation is a common feature in natural coastal and riverine water ways interacting with both the water flow and sediment transport however the physical processes governing these interactions are still poorly understood which makes it difficult to predict sediment transport and morphodynamics in a vegetated environment we performed a simple experiment to study how sediment transport responds to the presence of flexible single blade vegetation and how this response is influenced by the vegetation density we found that the skin friction and sediment transport are reduced in a plant patch and that this effect is larger for denser vegetation we then evaluated several methods to calculate the skin friction in a vegetated flow which is the key to sediment transport prediction among these the inversion of bed load transport formulas and the einstein and banks 1950 methods appeared to produce the most reasonable values of the skin friction finally we suggest using the parameter which is the ratio of the skin friction computed by these methods to the total bed shear stress to make more realistic sediment transport predictions in morphodynamic models

the influence of current speed and vegetation density on flow structure in two macrotidal eelgrass canopies the influence of eelgrass zostera marina on near bed currents turbulence and drag was investigated at three sites in two eelgrass canopies of differing density and at one unvegetated site in the san juan archipelago of puget sound washington usa eelgrass blade length exceeded 1 m velocity profiles up to 1 5 m above the sea floor were collected over a spring neap tidal cycle with a downward looking pulse coherent acoustic doppler profiler above the canopies and two acoustic doppler velocimeters within the canopies the eelgrass attenuated currents by a minimum of 40 and by more than 70 at the most densely vegetated site attenuation decreased with increasing current speed the data were compared to the shear layer model of vegetated flows and the displaced logarithmic model velocity profiles outside the meadows were logarithmic within the canopies most profiles were consistent with the shear layer model with a logarithmic layer above the canopy however at the less dense sites when currents were strong shear at the sea floor and above the canopy was significant relative to shear at the top of the canopy and the velocity profiles more closely resembled those in a rough wall boundary layer turbulence was strong at the canopy top and decreased with height friction velocity at the canopy top was 1 5 2 times greater than at the unvegetated sandy site the coefficient of drag cd on the overlying flow derived from the logarithmic velocity profile above the canopy was 3 8 times greater than at the unvegetated site 0 01 0 023 vs 2 9 10 3

three component recordings interest for land seismic source study three component recordings provide access to the particle trajectory due to seismic events this three dimensional picture shows successions of complex phenomena nevertheless this trajectory has predominant directions of polarization a method of spatial directional filtering is described to calculate the polarization direction of parts of the trajectory the application of this method provides means to reject trajectory parts for which the angular gap between their polarization axis and a reference direction for example x y or z is greater than a given threshold angle real data are submitted to this method leading to a color coded display showing the direction of polarization of each wave train the same noise spread used in conjunction with two different seismic sources was recorded with triphone groups the two sources were an sh wave vibrator and marthor using spatial directional filterings with threshold angles varying from 0 to 90 degrees the corresponding quantities of energy emitted i

topographic normalization of landsat tm images of forest based on subpixel sun canopy sensor geometry abstract because trees are geotropic perpendicular to the geoid topography has no control over the sun crown geometry what topography does influence is the relative positioning of trees and thus the amount of shadowing cast by them within the canopy as satellite sensors in general measure the collective radiance of many trees inside their instantaneous field of view the overall canopy brightness at the pixel scale is strongly controlled by canopy shadowing and hence by the topography the removal of or compensation for topographic effects on forest images should be based on the normalization of mutual shadowing at the subpixel scale rather than on the normalization of sun terrain sensor geometry at the pixel scale the sun canopy sensor scs topographic correction model was developed to characterize and hence correct the topographic effects on forest images testing with simulated image data showed the scs model to be accurate root mean squared residual error

using lagrangian particle saltation observations for bedload sediment transport modelling a lagrangian model for the saltation of sand in water is proposed simulated saltation trajectories neglecting particle rotation and turbulence effects compare fairly well with experimental observations the model for particle motion is coupled with a stochastic model for particle collision with the bed such that a number of realizations of the saltation process can be simulated numerically model predictions of mean values and standard deviations of saltation height length and streamwise particle velocity agree fairly well with experimental observations model predictions of the dynamic friction coefficient are also in good agreement with experimental observations but they underestimate the value of 0 63 proposed by bagnold for this coefficient the saltation model is applied to the estimation of bedload transport rates of sand using a bagnoldean formulation modelled values of the bedload transport rates overestimate those predicted by commonly used bedload formulae which appears to be a consequence of problems in the definition of the dynamic friction coefficient these results seem to indicate a few problems with the bagnoldean formulation particularly regarding the continuum assumption for the bedload layer which would be valid only for very high particle concentrations and small particle diameters and also regarding the evaluation of the shear stress exerted on the bed by the saltating particles 1998 john wiley sons ltd

examination of reference concentration under waves and currents on the inner shelf 1 we examine reference concentration using three different data sets of near bed suspended sediment concentration observed under combined waves and currents the data include observations made at 15 and 20 m depth off dounreay scotland uk and observations obtained at 13 m depth off duck north carolina usa these data accommodate different dynamic conditions from wave dominated conditions at dounreay to wind driven current dominated conditions at duck and sediment properties median size of bed sediment ranging from 120 to 350 m near bed concentration profiles to elevations of about 80 cm were obtained using acoustic backscatter sensors with 1 cm resolution the reference concentrations cr at 1 cm were then evaluated by regressing the observed suspended sediment concentrations against a rouse type model bed shear stresses associated with each estimate of cr were estimated using the wave current interaction model of grant and madsen existing equations for reference concentration based on shear stress alone fail to accommodate all cr estimates from different environments we introduce a new empirical relationship between cr and the product of shields and inverse rouse numbers these dimensionless parameters represent the ratio of bed shear stress and submerged particle weight and the ratio of shear velocity and particle settling velocity respectively the new formula adjusts the amount of mobile sediment at the bed related to the shields number to that available for suspension at the reference height related to the inverse rouse number the new formula for reference concentration accommodates observations from different environments suggesting that it may have wide applicability on sandy inner shelves

evaluation of topographic effects in remotely sensed data abstract remotely sensed data are generally analyzed assuming flat terrain as the spectral signature of the ground depends upon the orientation of the surface slope the topography has to be considered for efficient radiometric corrections in mountainous regions in this paper we present a modelization of the atmospheric downward radiance at the ground level which gives us the relative contributions of the direct solar beam and of the diffused radiation for different atmospheric turbidities and different solar incidence angles lastly we estimate the influence of the topography on these contributions to show up which effects can be neglected

spectral wave dissipation over a barrier reef 1 a 2 week field experiment was conducted to measure surface wave dissipation on a barrier reef at kaneohe bay oahu hawaii wave heights and velocities were measured at several locations on the fore reef and the reef flat which were used to estimate rates of dissipation by wave breaking and bottom friction dissipation on the reef flat was found to be dominated by friction at rates that are significantly larger than those typically observed at sandy beach sites this is attributed to the rough surface generated by the reef organisms which makes the reef highly efficient at dissipating energy by bottom friction results were compared to a spectral wave friction model which showed that the variation in frictional dissipation among the different frequency components could be described using a single hydraulic roughness length scale surveys of the bottom roughness conducted on the reef flat showed that this hydraulic roughness length was comparable to the physical roughness measured at this site on the fore reef dissipation was due to the combined effect of frictional dissipation and wave breaking however in this region the magnitude of dissipation by bottom friction was comparable to wave breaking despite the existence of a well defined surf zone there under typical wave conditions the bulk of the total wave energy incident on kaneohe bay is dissipated by bottom friction not wave breaking as is often assumed for sandy beach sites and other coral reefs

flow resistance and sediment transport by concentrated overland flow in a grassland valley abstract flow resistance and sediment transport data are needed from well vegetated humid environments to evaluate surface wash erosion and channel incision by overland flow in humid environments runoff in valley floors can reach depths of several centimetres but erosion is often limited by dense grass cover intense grazing reduces grass cover but the impacts of this on sediment transport processes are poorly understood we conducted flume experiments in a grassed valley of coastal california to investigate flow resistance and sediment yield under natural conditions and with progressive clipping of grass cover flow resistance has a laminar like relationship with reynolds number but we attribute this to very low velocity beneath submerged stems and not to the state of flow the sediment transport relations provide support for the concept of a threshold shear stress below which erosion is effectively prevented by surface resistance shear stress partitioning suggests that on a densely grassed surface over 90 of flow resistance is exerted on plant stems this effectively prevents sediment transport at boundary shear stresses as high as 1000 1800 dyn cm2 complete clipping of the grass cover reduces the critical shear stress for sediment transport to 11 38 of that under natural conditions continued surface wash erosion and channel initiation are prevented however by strong soil cohesion provided by a dense root mat even with reduction of root density boundary shear stresses of at least 250 430 dyn cm2 are required for channel incision

temporal and spatial variability in the flow and dispersal of suspended sediment on a fringing reef flat molokai hawaii abstract a multi year study was conducted on a shallow fringing reef flat on molokai hawaii to determine the temporal and spatial dispersal patterns of terrigenous suspended sediment during this study trade wind conditions existed for the majority of the year on the reef flat the trade wind conditions produced strong currents and resuspended moderate amounts of sediment on the reef flat on a daily basis during the year of study resulting in an overwhelming contribution to the total sediment flux the magnitude and direction of the trade winds relative to the orientation of the coastline the shallow relief and broad morphology and tidal elevation provided the primary control of the physical processes that resuspended and transported sediment on the reef flat over the period of record spatial data indicate that much of the terrigenous sediment resuspended on the reef flat is transported predominantly alongshore and is confined to the inner to mid reef flat evidence for the limited across shore mixing and transport is provided by the dominantly alongshore wind driven currents during trade wind conditions and the well defined across shore gradient in percentage calcium carbonate of the suspended sediment regions of slightly offshore suspended sediment transport along the reef flat can be attributed to the circulation pattern set up by the interaction between the trade winds coastal morphology and anthropogenic coastal structures i e fish ponds and wharf the regions in which sediment were seen to move offshore provide the strongest link between the sediment dynamics on reef flat and fore reef and qualitatively appears to be correlated with low coral coverage on the fore reef

effects of riparian vegetation on topographic change during a large flood event rio puerco new mexico usa 1 the spatial distribution of riparian vegetation can strongly influence the geomorphic evolution of dryland rivers during large floods we present the results of an airborne lidar differencing study that quantifies the topographic change that occurred along a 12 km reach of the lower rio puerco new mexico during an extreme event in 2006 extensive erosion of the channel banks took place immediately upstream of the study area where tamarisk and sandbar willow had been removed within the densely vegetated study reach we measure a net volumetric change of 578 050 490 000 m3 with 88 3 of the total aggradation occurring along the floodplain and channel and 76 7 of the erosion focusing on the vertical valley walls the sediment derived from the devegetated reach deposited within the first 3 6 km of the study area with depth decaying exponentially with distance downstream elsewhere floodplain sediments were primarily sourced from the erosion of valley walls superimposed on this pattern are the effects of vegetation and valley morphology on sediment transport sediment thickness is seen to be uniform among sandbar willows and highly variable within tamarisk groves these reach scale patterns of sedimentation observed in the lidar differencing likely reflect complex interactions of vegetation flow and sediment at the scale of patches to individual plants

tide effects on wave attenuation and wave set up on a caribbean coral reef abstract the effects of tides on wave attenuation and wave set up were investigated at great pond bay a caribbean reef located in st croix u s virgin islands measurements of wave pressure fluctuations were made at three stations across the reef profile total wave set up was measured between the forereef and the reef crest or backreef lagoon wave spectra indicate significant filtering of energy at the peak frequencies as waves traveled across the reef the energy dissipation calculations imply an average energy reduction of 62 between the forereef and reef crest mean energy reduction between the forereef and lagoon was 90 energy dissipation between the forereef and reef crest increased 15 between high and low tide and 6 between forereef and lagoon tidal reduction of water depth at the reef crest intensified wave breaking and this condition increased energy dissipation measurements of wave set up ranged from 0 8 to 1 5 cm calculations of wave set up using tait s 1972 model showed good agreement with observations

sediment transport in the presence of large reef bottom roughness the presence of large bottom roughness such as that formed by benthic organisms on coral reef flats has important implications for the size concentration and transport of suspended sediment in coastal environments a 3 week field study was conducted in approximately 1 5 m water depth on the reef flat at ningaloo reef western australia to quantify the cross reef hydrodynamics and suspended sediment dynamics over the large bottom roughness 20 40 cm at the site a logarithmic mean current profile consistently developed above the height of the roughness however the flow was substantially reduced below the height of the roughness canopy region shear velocities inferred from the logarithmic profile and reynolds stresses measured at the top of the roughness which are traditionally used in predictive sediment transport formulations were similar but much larger than that required to suspend the relatively coarse sediment present at the bed importantly these stresses did not represent the stresses imparted on the sediment measured in suspension and are therefore not relevant to the description of suspended sediment transport in systems with large bottom roughness estimates of the bed shear stresses that accounted for the reduced near bed flow in the presence of large roughness vastly improved the relationship between the predicted and observed grain sizes that were in suspension thus the impact of roughness not only on the overlying flow but also on bed stresses must be accounted for to accurately estimate suspended sediment transport in regions with large bottom roughness a common feature of many shallow coastal ecosystems

dart radiative transfer modelling for sloping landscapes abstract topography is one of the key factors that impact remotely sensed data and their interpretation indeed combined with the viewing geometry and neighbour effects it strongly affects the direct diffuse and multi scattered scene irradiance which in turn impacts the radiative budget and remote sensing signals of the landscapes the increased availability of digital elevation models dem and the advancement of 3d radiative transfer rt models allow us to better address these topographic effects dart discrete anisotropic radiative transfer is one of the most accurate and comprehensive 3d rt models that simulate remote sensing observations of natural and urban landscapes with topography and atmosphere it simulates environmental effects i e impact of adjacent landscape on the observed landscape using a so called infinite slope mode that infinitely duplicates the observed landscape while ensuring the continuity of slope and altitude at the dem edges up to dart version 5 7 4 this mode was slightly inaccurate and computer intensive depending on the topography this paper presents an innovative modelling strategy that greatly improves it in terms of accuracy image quality and computer efficiency for that a fictive auxiliary oblique plane adapted to the landscape topography is introduced for managing the scene illumination the earth atmosphere coupling and the storage of the radiation that exits the scene before being projected onto the sensor plane improvements and validations are illustrated both visually and quantitatively by dart images radiometric products and radiative budget for example the observed reflectance of a lambertian slope is equal to the expected analytical value in addition the solar plane reflectance of a forest on a mountain slope experimental scene has an average error of about 0 01 relative to the reflectance of the same forest stand in the reference scene i e nine duplications of the experimental scene this new modelling is already integrated in the official dart version https dart omp eu

scs c a modified sun canopy sensor topographic correction in forested terrain topographic correction based on sun canopy sensor scs geometry is more appropriate than terrain based corrections in forested areas since scs preserves the geotropic nature of trees vertical growth regardless of terrain view and illumination angles however in some terrain orientations scs experiences an overcorrection problem similar to other simple photometric functions to address this problem we propose a new scs c correction that accounts for diffuse atmospheric irradiance based on the c correction a rigorous comprehensive and flexible method for independent validation based on canopy geometric optical reflectance models is also introduced as an improvement over previous validation approaches and forms a secondary contribution of this paper results for a full range of slopes aspects and crown closures showed scs c provided improved corrections compared to the scs and four other photometric approaches cosine c minnaert statistical empirical for a rocky mountain forest setting in western canada it was concluded that scs c should be considered for topographic correction of remote sensing imagery in forested terrain

the limited growth of vegetated shear layers 1 in contrast to free shear layers which grow continuously downstream shear layers generated by submerged vegetation grow only to a finite thickness because these shear layers are characterized by coherent vortex structures and rapid vertical mixing their thickness controls exchange between the vegetation and the overlying water experiments conducted in a laboratory flume show that the growth of these obstructed shear layers is arrested once the production of shear layer scale turbulent kinetic energy ske is balanced by dissipation of ske within the canopy this equilibrium condition along with a mixing length closure scheme was used in a one dimensional numerical model to predict the mean velocity profiles of the experimental shear layers the agreement between model and experiment is very good but field application of the model is limited by a lack of description of the drag coefficient in a submerged canopy

an improved topography coupled kernel driven model for land surface anisotropic reflectance the semiempirical kernel driven model is commonly used for global surface reflectance characterization because of its simplicity and underlying physical meaning however the current kernel driven reflectance models assume that the terrain is flat and homogeneous and can induce significant errors in the surface reflectance estimation and subsequent parameter retrievals over rugged terrain in this study an improved topography coupled kernel driven tckd reflectance model with the correction of diffuse skylight effects was proposed based on the diffused equivalent slope model desm and rossthick litransit rtlt kernel driven model the tckd model s accuracy and effectiveness were evaluated using surface reflectance simulated by the radiosity approach and the moderate resolution imaging spectroradiometer modis data against simulated data the results show that the tckd model can accurately capture the distortion of the reflectance shape and hemispherical distribution caused by the topographic effects compared to modis data the tckd model has an overall better performance than the rtlt model across different spatial scales and land cover types when the mean slope is larger than 35 at the 500 m resolution the tckd model s near infrared nir root mean square error rmse and the regression slope of the fitting line are 0 037 and 0 752 respectively whereas those of the rtlt model are 0 049 and 0 645 neglecting the diffuse skylight in the tckd model can also lead to great bias in the reflectance retrievals when the mean slope is 31 as the ratio of diffuse skylight varies from 0 to 1 the nir rmse of the tckd model decreases from 0 012 to 0 005 whereas that increases from 0 012 to around 0 02 if the diffuse skylight effects are neglected these preliminary results demonstrate that the tckd model is capable of improving the fitting ability of the kernel driven model over rugged terrain and provides potentials for better retrieving and interpreting land surface parameters such as land surface albedo in mountainous areas

recent advances in the use of public domain satellite imagery for mineral exploration a review of landsat 8 and sentinel 2 applications abstract thanks to their wide coverage and the valuable spectral information remote sensing data constitute a popular instrument in the mineral exploration toolbox in recent times the remote sensing community has witnessed the launch of the new and improved landsat 8 and sentinel 2 multispectral sensors the former constitutes the eighth sensor of the landsat series launched by the national aeronautics and space administration nasa while the latter is linked to the sentinel mission launched by the european space agency esa the main objective of our contribution is to provide a comprehensive review of the use of the landsat 8 and sentinel 2 multispectral sensors in mineral exploration the free and open access to these data and their enhanced spectral and spatial characteristics compared to the existing multispectral sensors has clearly promoted the use of remotely sensed in mineral exploration in addition as illustrated by the case studies presented in this paper landsat 8 and sentinel 2 data present effective and accurate mapping tools for mineral exploration both sensors identified iron oxides and al oh absorption features in addition to silicate and carbonate minerals our review indicated that landsat 8 is by far the more popular sensor in mineral exploration applications greater uptake of sentinel 2 and further case studies will be necessary to better demonstrate its capabilities and potential

probability distributions of particle hop distance and travel time over equilibrium mobile bedforms the joint probability distribution of streamwise particle hop distance lateral particle hop distance and travel time constrains the relationships between topographic change and sediment transport

balancing aggradation and progradation on a vegetated delta the importance of fluctuating discharge in depositional systems vegetation is an important component of constructional landscapes as plants enhance deposition and provide organic sediment that can increase aggradation rates to combat land loss we conducted two sets of laboratory experiments using alfalfa medicago sativa to determine the effects of plants on channel organization and large scale delta dynamics in the first set we found that rapid vegetation colonization enhanced deposition but inhibited channelization via increased form drag that reduced the shear stress available for sediment entrainment and transport a second set of experiments used discharge fluctuations between flood and base flow or interflood interfloods were critical for reworking the topset via channel incision and lateral migration to create channel relief and prevent rapid plant colonization these low flow periods also greatly reduced the topset slope in the absence of vegetation by removing topset sediment and delivering it to the shoreline floods decreased relief by filling channels with sediment resulting in periods of rapid progradation and enhanced aggradation over the topset surface which was amplified by vegetation the combination of discharge fluctuations and vegetation thus provided a balance of vertical aggradation and lateral progradation we conclude that plants can inhibit channelization in depositional systems and that discharge fluctuations encourage channel network organization to naturally balance against aggradation thus variations in discharge are an important aspect of understanding the ecomorphodynamics of aggrading surfaces and modeling vegetated deltaic systems and the combined influences of plants and discharge variations can act to balance vertical and lateral delta growth

field observations of wave driven water level gradients across a coral reef flat 1 field measurements of still water surface elevations were obtained across a narrow leeward reef flat on lady elliot island great barrier reef australia in june 2003 stilling wells were deployed from the reef crest landward to the island beach and waves and mean water levels were monitored over both rising and falling tides during low to moderate wave energy conditions wave setup of up to 13 8 cm above still water level occurred in the presence of incident waves of 0 4 m yielding maximum water surface slopes greater than 6 results show that the magnitude of wave setup varies both temporally and spatially across the reef with changing water depth setup is dominant on the reef edge at low tide evolving into a dual setup system at both the reef edge and shoreline at midtide and finally a dominant shoreline setup at high tide on lady elliot island the dual setup system is considered to result from spatial differences in transformation and breaking of swell and wind waves at midtide stages the presence of a dual setup system across a reef flat has not been previously identified in field or modeling studies and has potentially significant implications for reefal current development sediment transport and the stability of reef island shorelines

wave driven circulation of a coastal reef lagoon system abstract the response of the circulation of a coral reef system in kaneohe bay hawaii to incident wave forcing was investigated using field data collected during a 10 month experiment results from the study revealed that wave forcing was the dominant mechanism driving the circulation over much of kaneohe bay as predicted theoretically wave setup generated near the reef crest resulting from wave breaking established a pressure gradient that drove flow over the reef and out of the two reef channels maximum reef setup was found to be roughly proportional to the offshore wave energy flux above a threshold root mean square wave height of 0 7 m at which height setup was negligible on the reef flat the wave driven currents increased approximately linearly with incident wave height however the magnitude of these currents was relatively weak typically 20 cm s 1 because of i the mild fore reef slope of kaneohe bay that reduced setup resulting from a combination of frictional wave damping and its re

sea level rise will drive divergent sediment transport patterns on fore reefs and reef flats potentially causing erosion on atoll islands these data files and matlab scripts reproduce the model data and figures as published in bramante et al in prep modeling the impacts of a changing climate on cross shore sediment transport kwajalein atoll marshall islands

modeling flow in coral communities with and without waves a synthesis of porous media and canopy flow approaches both canopy flow and porous media theories have been developed independent of one another to predict flow through submerged porous structures these approaches are very similar albeit with some key differences in how canopy resistance forces are parameterized canopy models provide a means of parameterizing the shear stresses that occur at the top of the canopy whereas porous media models can often provide a simpler and more tractable way of parameterizing turbulent form drag based on simple morphological metrics and empirical relationships already in the hydrology literature we developed a set of equations combining aspects of both models and applied this hybridized model to predict the flow structure within an experimental canopy formed by the branching coral porites compressa using model parameter values obtained from the literature results from the model predictions agreed well with direct measurements of flow speed and flow forces derived from particle image velocimetry under conditions of both unidirectional and wave driven oscillatory flow

estimating mountain glacier surface temperatures from landsat etm thermal infrared data a case study of qiyi glacier china abstract surface temperatures on mountain glaciers are a direct reflection of the heat budget at the glacier surface which controls the degree of ablation an understanding of surface temperatures is therefore crucial in simulating the evolution of mountain glaciers and in understanding a glacier s response to climate change in situ observations indicate that when the exitance angle equals 75 relative to the nadir angle the emissivity variation at 12 5 m in bare ice is as much as 0 24 however research involving the remote sensing retrieval of mountain glacier surface temperatures does not generally take into account the topography i e the exitance angle and the validation of remote sensing approaches using surficial climate measurements on mountain glaciers is lacking here we utilize the etm multispectral dataset and resampled water vapor content data from mod05 combined with the emissivity model of ice and snow taking the exitance angle into account hori et al 2013 and employ the single channel algorithm developed by jimenez munoz et al 2009 to calculate the remote sensing retrieved surface temperature distribution across qiyi glacier china from july 2012 to september 2013 the remote sensing retrieved temperatures are validated by the 10 min mean measurements of surface temperature from two automatic weather stations at different altitudes on the glacier and the results show good agreement at the two sites with an average bias of 0 96 k and an average root mean square error of 1 5 k of note in summer the influence of thermal emissions from surrounding topography means that the error associated with retrieved temperatures for the glacier tongue and margins might exceed 1 5 k

sediment patterns near a model patch of reedy emergent vegetation this laboratory study describes the sediment patterns formed in a sand bed around circular patches of rigid vertical cylinders representing a patch of reedy emergent vegetation the patch diameter was much smaller than the channel width two patch densities solid volume fraction 3 and 10 and two patch diameters 22 and 10 cm were considered for flows above the threshold of sediment motion patterns of sediment erosion and deposition were observed around and within the patch scouring within the patch was positively correlated with turbulent kinetic energy in the patch for sparse patches sediment scoured from within the patch was mostly deposited within one patch diameter downstream of the patch for dense patches which experience greater flow diversion sediment scoured from the patch was carried farther downstream before deposition along the patch centerline differences between the sparse and dense patch patterns of deposition are explained in the context of flow diversion and wake structure which are related to a nondimensional flow blockage parameter while sediment was redistributed near the patch observations suggest that net deposition was not recorded at the reach scale

wave driven flow over shallow reefs long term 1 month observations of waves and currents over a natural reef are presented which show a strong correlation between offshore rms incident wave height and cross reef currents at subtidal frequencies the energy spectrum of the cross reef currents shows a significant peak at twice the semidiurnal tidal frequency while the spectrum of sea surface elevation over the reef flat shows no corresponding peak furthermore experimental results reported by gourlay 1993 show setup over the reef occurs in the absence of a beach and the cross reef transport decreases with an increase in the sea surface slope across the reef flat due to an increase in setup at the top of the reef face analytic solutions for flow forced by wave breaking over an idealized reef explain the above features of cross reef flows in the absence of a beach through the surf zone on the reef face the cross reef gradient in the radiation stress due to wave breaking is partitioned between balancing an offshore pressure gradient associated with setup over the reef and forcing a mean flow across the reef over the reef flat where the depth is constant there is no forcing due to wave breaking and the flow is driven by a pressure gradient which results from the setup through the surf zone the magnitude of the setup through the surf zone is such that the transport across the reef flat matches the transport through the surf zone which is forced by the gradient in the radiation stress solutions are presented for general reef geometry defined by the reef width and slope of the seaward reef face and incident wave forcing defined by the depth at the breakpoint and the depth of water over the reef as the depth over the reef goes to zero the solutions converge to the plane beach solutions described by longuet higgins and stewart 1964 wave setup is maximized and the cross reef transport is zero in other cases the relative magnitudes of the setup and the cross reef transport depend on the geometry of the reef and the incident wave forcing

the topographic normalization of hyperspectral data implications for the selection of spectral end members and lithologic mapping abstract compact airborne spectrographic imager casi hyperspectral data is used to investigate the effects of topography on the selection of spectral end members and to assess whether the topographic correction improves the discrimination of rock units for lithologic mapping a publicly available digital elevation model dem at a scale of 1 50 000 is used to model the radiance variation of the scene as a function of topography assuming a lambertian surface skylight is estimated and removed from the airborne data using a dark object correction the casi data is corrected on a pixel by pixel basis to normalize the scene to a uniform solar illumination and viewing geometry the results show that topography has the effect of expanding end member clusters at times resulting in the overlap of clusters and that the correction process can effectively reduce the variation in detected radiance due to changes in local illumination when topographic effects are embedded in the hyperspectral data methods typically used for the selection of end members such as the convex hull method can miss end members or result in the selection of nonrepresentative pixels as end members thus end members selected by some conventional methods are very likely incomplete or nonrepresentative if the topographic effect is embedded in the data as shown in this study the topographic correction can reveal hidden end members and achieve a better representation of end members via the statistical center of isolated clusters

retrieval of snow reflectance from landsat data in rugged terrain we developed a model to calculate the spectral reflectance of snow by normalizing the topographic effect and correcting the atmospheric effect simultaneously this model considers the shadowing effect of the surrounding terrain on both direct and diffuse irradiance by using the obstruction coefficient in sun ray direction and introducing the isotropic view factor in addition a new method to calculate the surrounding reflected irradiance by introducing the shape factor which can account for the radiation reflected from the surrounding pixels was developed the model was tested in the upper stream of the heihe river basin qilian mountains china using a subscene of a landsat enhanced thematic mapper plus etm image acquired on 20 april 2000 the result showed that the model could eliminate most of the shadowing effect of rugged terrain and could estimate snow reflectance correctly the problem of data saturation when retrieving snow reflectance is also discussed

ecosystem engineering by annual intertidal seagrass beds sediment accretion and modification seagrasses are generally known as ecosystem engineers as they reduce flow velocities in their canopies in perennial subtidal meadows this usually leads to increased net sedimentation rates and reduction of the grain size the present study aims to describe the contribution of annual seagrass populations to these processes and elucidate the temporal dynamics sediment accretion and grain size modification were experimentally tested by transplanting seedlings of an annual intertidal eelgrass population to an unvegetated tidal flat within the planting units 79 shoots m 2 4 7 mm of sediment accreted whereas in the most dense parts of these units 199 shoots m 2 accretion amounted to 7 1 mm the silt fraction 63 m increased and the sand fraction 63 500 m decreased in the eelgrass beds which provides evidence that higher silt content in seagrass beds is the result and not the cause of seagrass presence annual intertidal eelgrass beds significantly contribute to the immobilisation of sediment during the growing season with its magnitude depending on canopy density during winter the accumulated sediments were released again and could even induce additional erosion possible consequences of these sediment dynamics for the larger scale functioning of estuarine ecosystems are discussed

atmospheric corrections to satellite radiometric data over rugged terrain radlometnc measurements from satelhtes m the solar portmn of the electromagnetic spectrum can be converted to measurements of surface eratance over rugged terrain the satelhte image must be precisely registered to a terrain data set for small areas a first order polynomial mterpolatmn scheme is generally satisfactory for the geometric rectlficatmn if there are saturated plxels a nearest neighbor procedure is used for the mterpolated satellite radiance nmnbers otherwise a cublc convolutmn algorithm is used path radiance and path transmittance are calculated wlth a simple spectral model whmh reqmres an estimate of the water vapor and aerosol content of the atmosphere

decomposition of multicomponent seismic data into primary p and s wave responses1 inversion of multicomponent seismic data can be subdivided in three main processes 1 surface related preprocessing decomposition of the multicomponent data into primary p and s wave responses 2 prestack migration of the primary p and s wave responses yielding the angle dependent p p p s s p and s s reflectivity of the subsurface 3 target related post processing transformation of the reflectivity into the rock and pore parameters in the target this paper deals with the theoretical aspects of surface related preprocessing which consists of two steps 1 decomposition of the multicomponent data pseudo p and s wave responses into true p and s wave responses 2 elimination of the surface related multiple reflections and conversions

episodic circulation and exchange in a wave driven coral reef and lagoon system we examined the role of wave driven circulation relative to wind and buoyancy forcing in a coral reef lagoon system circulation measurements in paopao bay moorea french polynesia during austral summer show the importance of waves in driving flows over the reef crest through the lagoon and out the reef pass tides were comparatively weak due to proximity to amphidromic points and exhibited an unusual spring neap cycle where the major lunar tide modulated the major solar tide and the overall tidal phase stayed approximately constant wind had only a secondary effect compared to surface waves a simple fluid mass balance indicated rapid flushing of the shallow back reef and export through the reef pass and a reef capture zone width of 2 3 km the reef pass circulation dynamics exhibited two layer baroclinic exchange flow when waves were small which was suppressed during large wave events the unusually weak tidal forcing provided an opportunity to more closely investigate wave driven circulation dynamics as expected theoretically there was a wave driven setup of the free surface across the shallow lagoon which drove a highly frictional flow evident by a large drag coefficient cp 0 1 diverging from extant theory the observed setup varied strongly with significant wave height and period overall the circulation and exchange between this coral reef system and the adjacent open ocean were largely determined by episodic remote forcing events and differed significantly from periodic tidal exchange mechanisms

spatial distribution of deposition within a patch of vegetation 1 this laboratory study describes the spatial pattern of deposition observed in a patch of vegetation located at the wall of a channel there are two sources of sediment flux to the patch the advection of particles across the upstream leading edge and the lateral dispersion of particles from the adjacent open channel the relative contribution of these two supplies determines the spatial pattern of net deposition in the patch we define the advection length scale within the patch as the longitudinal distance over which advection contributes a significant sediment source at distances from the leading edge that are within the advection length scale net deposition in the patch is laterally uniform reflecting the laterally uniform mean flow delivering the particles at distances farther than the advection length scale from the leading edge the net deposition is highest near the flow parallel edge and decreases into the patch which is the signature of dispersive transport from the patch edge two processes contribute to the lateral dispersion both of which are associated with the shear layer vortices formed at the flow parallel interface between the patch and the channel the vortices generate turbulence and enhance the turbulent diffusion of sediment across the interface in addition the vortices induce a wave oscillation in the flow field within the patch that appears to enhance the lateral transport inside the patch

field study of wave attenuation on an offshore coral reef a major field experiment was conducted which obtained measurements of the attenuation and transformation of short gravity waves as they cross the windward edge of an offshore coral reef water level data were collected for over 3000 individual time series during a wide range of environmental conditions at the innermost measurement site which is located on the horizontal reef flat after the completion of wave breaking the upper bound of significant and maximum wave heights is limited to less than 40 and 60 of the reef flat water depth respectively as with significant wave height both the shape and energy level of the reef flat spectra are strongly affected by changes in reef flat water depth for higher tide levels the spectra on the reef flat closely mimic the corresponding incident spectra however the attenuation is greater for both lower frequencies and higher energy portions of the spectra this causes the reef flat spectra to be broader than those measured windward of the reef at lower water levels considerable energy losses due to wave breaking and bottom friction occur most of the energy loss comes from the vicinity of the spectral peak and energy shifts to harmonics of the peak of the spectrum can be seen

modeling surface longwave radiation over high relief terrain abstract thermal anisotropy is an important phenomenon in thermal infrared remote sensing as it restricts the retrieval accuracy of surface longwave radiation slr topography is an essential controlling factor for the directionality of slr for high relief regions e g mountain regions where there is land surface heterogeneity and non isothermal properties at pixel scales however satellite sensors can only receive radiance from a specific surface object at a small number of simultaneous viewing angles which makes the quantitative modeling of thermal anisotropy challenging therefore we developed the topographic longwave radiation model tlrm to describe the directionality of slr components taking into account the variability of both subpixel topography and thermal anisotropy in high relief regions the reliability of tlrm was validated using the discrete anisotropic radiative transfer dart model over two typical geomorphic areas a valley scene and a peak scene the preliminary validation shows good agreement in terms of surface upward longwave radiance which confirms the potential of tlrm for capturing the anisotropic patterns of land surfaces the radiance values simulated by the dart model were first revised for the spectral mismatch then they are used to correct residual deviation for tlrm using linear regressions the root mean square error rmse and coefficient of determination r2 were 0 830 w m2 sr and 0 746 for the valley scene respectively and 0 239 w m2 sr and 0 711 for the peak scene respectively compared with tlrm models that do not consider terrain effects generate significant discrepancies in high relief slr components the differences in downward longwave radiation can reach 60 w m2 in valleys without considering terrain effects based on the reference of hemispherical upward longwave radiation surface upward longwave radiation estimated by the direct estimation method had a bias of 11 41 w m2 and standard deviation std of 7 30 w m2 while the directional upward longwave radiation had a bias of 5 99 w m2 and std of 4 08 w m2 showing lower estimation variation the discrepancy between surface net longwave radiation nlr and terrain corrected nlr ranged between 50 and 130 w m2 with clear negative biases mainly occurring in valleys with higher spatial resolutions of remotely sensed imagery the influence of complex terrain on land surface radiative flux has become more significant this parameterization scheme is expected to better represent the topographic effects on slr enhance understanding of thermal anisotropy in non isothermal mixed pixel areas of high relief and improve the inversion accuracy of slr

multicomponent seismic reflection profiling over an ore body structure a scale model investigation a multicomponent seismic laboratory experiment was conducted to examine the seismic signature of a simulated ore body structure the data were processed using a new form of controlled direction reception cdr filter which operates in tau p polarisation space so as to isolate the p and s waves the four cdr sections showed pp ss ps and sp wave reflections and all mode conversions from these the geometry and reflectivity of the ore body can be reconstructed with single component recording and processing imaging of the ore is extremely difficult

sediment transport part i bed load transport a method is presented which enables the computation of the bed load transport as the product of the saltation height the particle velocity and the bed load concentration the equations of motions for a solitary particle are solved numerically to determine the saltation height and particle velocity experiments with gravel particles transported as bed load are selected to calibrate the mathematical model using the lift coefficient as a free parameter the model is used to compute the saltation heights and lengths for a range of flow conditions the computational results are used to determine simple relationships for the saltation characteristics measured transport rates of the bed load are used to compute the sediment concentration in the bed load layer a simple expression specifying the bed load concentration as a function of the flow and sediment conditions is proposed a verification analysis using about 600 alternative data shows that about 77 of the predicted bed load transport rates are within 0 5 and 2 times the observed values

predicting the hydrodynamic response of a coastal reef lagoon system to a tropical cyclone using phase averaged and surfbeat resolving wave models abstract tropical cyclone tc olwyn travelled along the coast of ningaloo reef in northwestern australia as a category 3 tc during 12 13 march 2015 with sustained wind speeds of over 130 km h 1 and significant wave heights on the forereef reaching 6 m observations from tc olwyn showed that contrary to typical wave transformation patterns across a coastal reef lagoon under the tc conditions there was a substantial shoreward increase of wave height this unusual pattern was primarily due to strong local wind wave generation under the extreme wind conditions despite the lagoon itself being relatively small order 1 km wide and shallow order 1 m depth two common types of coastal numerical wave models that include either wave growth i e the phase averaged model swan or infragravity waves i e the surfbeat resolving model xbeach but not both processes were used to assess the capabilities of numerical models to predict the cyclone induced hydrodynamics model results showed that wave conditions in the lagoon and at the shoreline were dominated by locally generated wind waves with the reef efficiently dissipating the large incident waves offshore the infragravity waves in the lagoon were only of secondary importance during the tc compared to the locally generated sea swell waves although both the phase averaged swan and surfbeat resolving xbeach models were able to predict some of the local hydrodynamic responses for this specific site and storm the use of a phase averaged model yielded the most accurate predictions of the hydrodynamics given that it included wind wave growth however because the influence of infragravity waves cannot be neglected in reef environments in general these results emphasize the need for a more general modeling approach that requires the addition of wind wave growth formulations into surfbeat or fully phase resolving classes of numerical wave models and or the addition of an infragravity wave formulation in spectral wave models

temporal and spatial variation of the surface albedo of the morteratschgletscher switzerland as derived from 12 landsat images this investigation uses landsat images from 12 days in 1999 and 2000 to study the spatial and temporal variation in surface albedo of a glacier with a rugged topography morteratschgletscher switzerland our retrieval method considers all processes that substantially influence the relationship between the satellite signal and the surface albedo the correction for the anisotropy of the reflected radiation field of ice and snow ranges up to 0 10 depending on wavelength band solar zenith angle and surface type we analyzed the uncertainties in the retrieval method and mainly expect errors in satellite derived albedos for areas with large variation in topography and high albedos the latter is due to application of bidirectional reflectance distribution function brdf parameterizations for the anisotropic correction to albedos outside the parameterizations validity on average satellite derived albedos exceed the measured surface albedo by 0 03 the glacier tongue is characterized by bands of low and high albedo relating to ice with higher and lower concentrations of debris the ice albedo shows no dependence on altitude except at 2000 2200 m a s l it increases during summer which is likely associated with rainfall as concluded from a comparison between summer rainfall and measured albedos

flow characteristics within different configurations of submerged flexible vegetation summary the effects of three configurations aligned staggered and columnar of submerged flexible vegetation on flow structure are investigated experimentally in the laboratory time averaged flow velocity and turbulence behavior are evaluated at different positions in each configuration by using a 3d acoustic doppler velocimeter adv according to the hydrodynamic regimes in experimental results the vertical distribution of streamwise velocity can be separated into three layers the upper non vegetated layer middle vegetation layer and lower sheath layer this three layer model which is associated with different logarithmic equations can be applied to describe the vertical distribution of streamwise velocity the local maximum velocity within vegetation occurs at the sheath section of a plant clump 0 10 0 15 vegetation height h v where the frontal width is minimal turbulent intensities in the streamwise u rms and spanwise v rms directions peak at the sheath section and at the approximate top of the canopy 0 9 1 2 h v the maximum reynolds stresses exist at roughly 0 9 1 2 h v which may be migrated vertically as the frontal width of a plant clump is increased this high frontal width also increases streamwise velocity above vegetation leading to increase variations in reynolds stresses around the canopy top on the vertical turbulent velocity scale w rms the vortices above a still canopy rotate faster than those above a waving canopy therefore the experimental results demonstrate that the flow field can vary significantly at the sheath section and at the top of a plant clump due to altered flow pass these analytical findings will likely prove useful when designing ecological habitats and preventing riverbed erosion

unified view of sediment transport by currents and waves i initiation of motion bed roughness and bed load transport attention is given to the properties of sediment beds over the full range of conditions silts to gravel in particular the effect of fine silt on the bed composition and on initiation of motion critical conditions is discussed high quality bed load transport data sets are identified and analyzed showing that the bed load transport in the sand range is related to velocity to power 2 5 the bed load transport is not much affected by particle size the prediction of bed roughness is addressed and the prediction of bed load transport in steady river flow is extended to coastal flow applying an intrawave approach simplified bed load transport formulas are presented which can be used to obtain a quick estimate of bed load transport in river and coastal flows it is shown that the sediment transport of fine silts to coarse sand can be described in a unified model framework using fairly simple expressions the proposed model is fully predictive in the sense that only the basic hydrodynamic parameters dep

modelling topoclimatic controls on palaeoglaciers implications for inferring palaeoclimate from geomorphic evidence abstract evidence of small glaciers is often used to infer past atmospheric climate through calculation of steady state elas however if topographic niches such as shading or windblown snow augmented mass balance then elas cannot reflect regional climate and determining the significance of these topoclimates is therefore important the brecon beacons south wales contains upland glacial landforms dating to the younger dryas 11 000 10 000 yr bp when local climate was at the threshold for glaciation this case study categorises topoclimate using three dimensional modelling of topography and reconstructed palaeoglaciers from two sites containing mapped moraines whose orientation suggest complex patterns of deglaciation ablation season solar radiation is modelled over multiple ice surfaces as shade from surrounding topography and intensity from ice surface incidence angle snowblow and avalanching potential models are also used and the significance of all topoclimate variables assessed against a mass balance deficit calculated for each glacier given palaeoclimate models for the region results demonstrate that both glaciers were likely to be heavily reliant on topoclimate and that previous studies underestimate the significance of solar radiation modelled over multiple ice surfaces reflecting patterns of recession results indicate that the distribution of topoclimate variables predicts the style of deglaciation at both sites possibly explaining the complexity of glacial evidence in this environment

on the small scale fractal geometrical structure of a living coral reef barrier topographical complexity of coral reefs is of primary importance for a number of hydrodynamical and ecological processes the present study is based on a series of high resolution seabottom elevation measurements along the maupiti barrier reef french polynesia several statistical metrics and spectral analysis are used to characterize the spatial evolution of the coral geometrical structure from the reef crest to the backreef a consistent fractal like power law exists in the spectral density of bottom elevation for length scales between 0 1 and 7m while at larger scale the reef structure shows a different pattern such a fine characterization of the reef geometrical structure provides key elements to reconstruct the reef history to improve the representation of reef roughness in hydrodynamical models and to monitor the evolution of coral reef systems in the global change context

the definition of remotely sensed reflectance quantities suitable for rugged terrain abstract the anisotropic scattering behavior of land surface is characterized by its bidirectional reflectance distribution function brdf however a physically consistent brdf definition is still lacking for heterogeneous and rugged terrain that accounts for approximately 24 of earth s land surface in this study we revisited current brdf definitions and updated them for rugged terrain with few dependent parameters illumination and viewing geometries terrain shadows effective areas of illumination and observation and anisotropic reflectance properties of subpixel scale slopes furthermore the bidirectional reflectance factor brf hemispherical directional reflectance factor hdrf directional hemispheric reflectance dhr and bi hemispherical reflectance bhr were proposed within the current physical framework of reflectance quantities these reflectance quantities have been adopted by the 3 d discrete anisotropic radiative transfer dart model to provide the simulations of remote sensing images to highlight the importance of a proper usage of such reflectance terms we used dart simulations to present the topographic effects on these reflectance quantities finally the other issues with respect to surface brdf brf such as spatial scale of rugged terrain characterization of anisotropic reflectance of micro scale surfaces derivative reflectance quantities topographic parameters wavelength dependence and reciprocity and future perspective were discussed

sedimentation processes in a coral reef embayment hanalei bay kauai oceanographic measurements and sediment samples were collected during the summer of 2006 as part of a multi year study of coastal circulation and the fate of terrigenous sediment on coral reefs in hanalei bay kauai the goal of this study was to better understand sediment dynamics in a coral reef lined embayment where winds ocean surface waves and river floods are important processes during a summer period that was marked by two wave events and one river flood we documented significant differences in sediment trap collection rates and the composition grain size and magnitude of sediment transported in the bay sediment trap collection rates were well correlated with combined wave current near bed shear stresses during the non flood periods but were not correlated during the flood the flood s delivery of fine grained sediment to the bay initially caused high turbidity and sediment collection rates off the river mouth but the plume dispersed relatively quickly over the next month the flood deposit was reworked by mild waves and currents and the fine grained terrestrial sediment was advected around the bay and collected in sediment traps away from the river mouth long after the turbid surface plume was gone the reworked flood deposits due to their longer duration of influence and proximity to the seabed appear to pose a greater long term impact to benthic coral reef communities than the flood plumes themselves the results presented here display how spatial and temporal differences in hydrodynamic processes which result from variations in reef morphology and orientation cause substantial variations in the deposition residence time resuspension and advection of both reef derived and fluvial sediment over relatively short spatial scales in a coral reef embayment

topographic effects in avhrr ndvi data an investigation is made of the errors induced in the normalized difference vegetation index ndvi by topographic variation the advanced radiometric ray tracer ararat is used to simulate avhrr imagery for various viewing and illumination conditions at 1 1 km and 50 m resolution topographic error is calculated as the difference between the variable terrain simulation and a flat plane simulation correlation between this error and various topographic factors such as shadowing and adjacement hill illumination are examined the importance of sky occlusion as a topographic factor is highlighted while topographic errors of 13 5 are found in the 50 m resolution simulations these errors are reduced markedly in the 1 1 km dataset to approximately 3

mixing layers and coherent structures in vegetated aquatic flows 1 to date flow through submerged aquatic vegetation has largely been viewed as perturbed boundary layer flow with vegetative drag treated as an extension of bed drag however recent studies of terrestrial canopies demonstrate that the flow structure within and just above an unconfined canopy more strongly resembles a mixing layer than a boundary layer this paper presents laboratory measurements obtained from a scaled seagrass model that demonstrate the applicability of the mixing layer analogy to aquatic systems specifically all vertical profiles of mean velocity contained an inflection point which makes the flow susceptible to kelvin helmholtz instability this instability leads to the generation of large coherent vortices within the mixing layer observed in the model at frequencies between 0 01 and 0 11 hz which dominate the vertical transport of momentum through the layer the downstream advection of these vortices is shown to cause the progressive coherent waving of aquatic vegetation known as the monami when the monami is present the turbulent vertical transport of momentum is enhanced with turbulent stresses penetrating an additional 30 of the plant height into the canopy

seismic wavefield separation by multicomponent tau p polarisation filtering abstract this paper presents a modified form of controlled direction reception cdr filter to separate p and s waves in a multi component seismic profile the aim of cdr is to enhance the clarity of the section the essence of the method in seeking s wave extinction is to perform a dot product between the signal vector and the polarisation slowness vector during projection of the section into tau p space using the p wave velocity along the array alternatively s waves can be enhanced and all other wave types including background noise suppressed by using a conjugate rotation operator and the s velocity profile in forming the slant stack a two dimensional gain function based on the rectilinearity of particle motion is then applied in tau p space as a non linear boost function in order to enhance strongly polarised arrivals synthetic and physical model examples are used to demonstrate the noise rejection properties of the cdr process and to show how p and s wave seismic sections can be separately obtained

momentum balance across a barrier reef this paper reports on a combined experimental and numerical study dedicated to barrier reefs hydrodynamics a network of pressure sensors and velocity profilers has been deployed for more than 2 months over the ouano reef barrier new caledonia the primary aim of the study is to assess the relevance of the classical depth averaged momentum balance in such a complex and poorly documented environment the combined analysis of experimental and numerical measurements reveals a specific hydrodynamic behavior contrasting with sandy beaches and fringing reefs the cross reef current induced by wave breaking over the barrier reef plays an important role in the momentum budget in particular through friction processes the hydrodynamic behavior over the barrier reef is thus characterized by the progressive transition from a nearly classical beach type behavior on the forereef where the gradient of radiation stress is balanced by a barotropic pressure gradient associated to the wave setup to an open channel type regime dominated by frictional head loss the reef top wave setup shows a clear depth dependency mainly attributed to the forereef curvature during extreme wave events the measurements tend to indicate a transition toward a critical hydraulic regime above the reef top the numerical simulations involving a non hydrostatic wave resolving model coupled to a urn x wiley jgrc media jgrc23848 jgrc23848 math 0001 turbulence model highlight the vertical structure of the flow over the reef flat a classical log layer profile is observed in agreement with measurements while above the forereef an anticlockwise circulation develops under the breaking zone

a fast canopy reflectance model to simulate realistic remote sensing scenarios a model for light interaction has been developed to compute spectral and bidirectional reflectance from discontinuous canopies approximated by an arbitrary configuration of plants the model assumes certain principles of geometric models e g that sensor integrates the radiance reflected from tree plants shaded soil and illuminated soil however the model attempts to compensate for errors due to multiple scattering in vegetation canopies that lead to nonlinear mixing in contrast to geometric models tree crowns are treated as porous partially transmitting geometric bodies reflectance of canopy and shadowed ground are nonlinear mixtures of leaves and background signatures which are moreover influenced by parameters of canopy such as leaf area index lai coefficient of attenuation and leaves transmittance optical parameters are not constant but stochastic variables are controlled by a certain texture in canopy envelopes and roughness and relief in surface background the model may also be run using backgrounds presenting variable topography and comprising different landscape features on imported real images the model predicts the basic features of the bidirectional reflectance factor brf i e bowl shape and the hotspot but unlike common models it is well suited to address the spectral and spatial domains for example the model provides a fast and efficient strategy to derive hyperspectral images at appropriate spatial resolutions e g regional scale over a wide range of ecosystems

the influence of waves and seagrass communities on suspended particulates in an estuarine embayment resuspension of bottom sediments by waves corresponding changes in suspended particulate material spm concentrations in the overlying water column and transport pathways of spm were investigated in a shallow estuarine embayment colonized by seagrass communities in chesapeake bay in shallow 2 m unvegetated regions significant resuspension of bottom sediments was evident when northerly winds exceeded 25 km h 1 increasing spm concentrations up to 10 fold high concentrations of spm generated by resuspension dissipated rapidly within 24 h after winds became calm patterns of spm along the embayment s depth gradient suggest that part of this resuspended material was transported offshore into deeper reaches of the estuary in areas of the embayment colonized by seagrasses wave energy was attenuated by the vegetation suppressing resuspension and enhancing deposition as a result spm concentrations were significantly lower inside seagrass beds than in adjacent unvegetated areas during periods of high winds when wave induced resuspension occurred in unvegetated areas spm concentrations remained unchanged inside the bed at normal water levels however when water levels were elevated by spring tides or storm surges plants were less effective at attenuating wave energy and spm concentrations increased inside the seagrass bed due to resuspension and advective processes calculations based on the results of this study indicate that sedimentation rates are substantially higher in seagrass communities than in unvegetated areas

modeling anisotropic reflectance over composite sloping terrain heterogeneous terrain significantly complicates signals received by airborne or satellite sensors it has been demonstrated that both solar direct beam and diffuse skylight illumination conditions are significant factors influencing the anisotropy of reflectance over mountainous areas several models and methods have been developed to account for topographic effects on surface reflectance at the pixel level in remote sensing however subtopographic effects are generally neglected for low spatial resolution pixels due to the complex law of radiative transfer and the limitations of higher spatial resolution digital elevation models which can lead to deviations in reflectance estimation accurately estimating the subtopographic effects on anisotropic reflectance over composite sloping terrain under different illumination conditions presents a challenge for remote sensing models and applications in this paper the diffused equivalent slope model desm was developed which is an anisotropic reflectance simulation model coupled with diffuse skylight over composite sloping terrain the corresponding subtopographic impact factor was also proposed to exhibit how microslope topography affects reflectance over composite sloping terrain under different illumination conditions simulated reflectance data sets simulated by the radiosity method and moderate resolution imaging spectroradiometer reflectance data were used to evaluate the performance of the desm model the results reveal that the desm model can accurately capture the reflectance anisotropy over composite sloping terrain under different illumination conditions and the subtopographic impact factor can account for the effects of microslope topography shadow and illumination conditions

dynamic single thread channels maintained by the interaction of flow and vegetation most rivers on earth today flow as a single channel in some cases with occasional islands and follow a more or less sinuous course however single thread channels have proven difficult to reproduce and study experimentally experimental self formed channels tend to widen and subdivide leading to a braided pattern cohesive sediment has been the main mechanism studied for stabilizing banks and producing a single thread channel we show how laboratory experiments using vegetation to stabilize banks can organize the flow and convert the planform morphology from braided to single thread our experimental strategy a repeated cycle of short periods of high water discharge alternating with longer periods of low discharge accompanied by plant seeding and growth leads to the evolution of a dynamic self maintaining single thread channel with well defined banks and floodplain by eliminating weak flow paths the vegetation corrals the water into a single dominant channel until the reduction in total wetted width leads to a new self organized state in which the flow removes vegetated area as fast as it is produced the new channel is deeper and has a broader distribution of depths than the braided one with channel size adjusted to carry almost all the flood flow the resulting system maintains a dynamic steady state via similar mechanisms to those that operate in meandering channels in the field specifically erosion at the outside of bends bend growth and bar development our methodology provides a basis for experimental development of self sustaining high amplitude meanders and has applications for river management and basic research purposes

vertical seismic profiling vertical seismic profiling is one of the rapidly developing areas of geophysical technology for exploring in mature basins the measurement basically involves recording the total upgoing and downgoing seismic wave fields propagating through a stratigraphic section by means of geophones clamped to the wall of a drilled well

effect of submerged flexible vegetation on flow structure and resistance abstract flume studies were carried out to investigate flow structure above flexible vegetation a new data set of mean velocity profiles and turbulence characteristics is reported from experiments with wheat the flow above the wheat reasonably followed the log law maximum values of the turbulence intensity urms and reynolds stress u w were found approximately at the level of the maximum observed deflected plant height a recent approach for describing vertical velocity profiles above aquatic vegetation stephan u 2002 zum flieswiderstandsverhalten flexibler vegetation wiener mitteilungen 180 doctoral thesis institute of hydraulics hydrology and water resources management faculty of civil engineering technical university of vienna was evaluated with these new data which represent a different vegetal roughness type the approach proved to be successful beyond the original scope however a new definition for the shear velocity based on the deflected plant height is suggested the benefit of this modification is that complex turbulence measurements can be avoided which enhances the practical applicability of the approach

extending a turbid medium brdf model to allow sloping terrain with a vertical plant stand this paper extends the turbid medium approach used for modeling bidirectional reflectance from horizontal plant canopies to sloping terrain with a vertically oriented plant stand previous treatments have accounted for terrain slope by simple adaptation to an inclined plane of models for horizontal surfaces however such treatments implicitly assume that plants grow perpendicularly to the surface despite the fact that plant stems continue to grow vertically on slopes the authors investigate the differences between their new vertical growth model and the more usual perpendicular to the surface growth model in terms of the effect on canopy albedo and bidirectional reflectance factors although the effect of leaf angle distribution on the albedo is different for both the vertical growth and perpendicular growth models it appears to be a much smaller effect than that due to terrain slope for the bidirectional reflectance factors brfs the magnitude and sign of the differences between the two models varies with the direction of observation the slope and the leaf angle distribution and can exceed 10 for a planophile canopy a comparison between modeled and measured data shows that model predictions under the vertical growth assumption are consistent with measurements whereas the assumption of perpendicular growth can lead to large errors