spectrally based mapping of riverbed composition abstract remote sensing methods provide an efficient means of characterizing fluvial systems this study evaluated the potential to map riverbed composition based on in situ and or remote measurements of reflectance field spectra and substrate photos from the snake river wyoming usa were used to identify different sediment facies and degrees of algal development and to quantify their optical characteristics we hypothesized that accounting for the effects of depth and water column attenuation to isolate the reflectance of the streambed would enhance distinctions among bottom types and facilitate substrate classification a bottom reflectance retrieval algorithm adapted from coastal research yielded realistic spectra for the 450 to 700 nm range but bottom reflectance based substrate classifications generated using a random forest technique were no more accurate than classifications derived from above water field spectra additional hypothesis testing indicated that a combination of reflectance magnitude brightness and indices of spectral shape provided the most accurate riverbed classifications convolving field spectra to the response functions of a multispectral satellite and a hyperspectral imaging system did not reduce classification accuracies implying that high spectral resolution was not essential supervised classifications of algal density produced from hyperspectral data and an inferred bottom reflectance image were not highly accurate but unsupervised classification of the bottom reflectance image revealed distinct spectrally based clusters suggesting that such an image could provide additional river information we attribute the failure of bottom reflectance retrieval to yield more reliable substrate maps to a latent correlation between depth and bottom type accounting for the effects of depth might have eliminated a key distinction among substrates and thus reduced discriminatory power although further more systematic study across a broader range of fluvial environments is needed to substantiate our initial results this case study suggests that bed composition in shallow clear flowing rivers potentially could be mapped remotely

spectrally based remote sensing of river bathymetry this paper evaluates the potential for remote mapping of river bathymetry by 1 examining the theoretical basis of a simple ratio based technique for retrieving depth information from passive optical image data 2 performing radiative transfer simulations to quantify the effects of suspended sediment concentration bottom reflectance and water surface state 3 assessing the accuracy of spectrally based depth retrieval under field conditions via ground based reflectance measurements and 4 producing bathymetric maps for a pair of gravel bed rivers from hyperspectral image data consideration of the relative magnitudes of various radiance components allowed us to define the range of conditions under which spectrally based depth retrieval is appropriate the remotely sensed signal must be dominated by bottom reflected radiance we developed a simple algorithm called optimal band ratio analysis obra for identifying pairs of wavelengths for which this critical assumption is valid and which yield strong linear relationships between an image derived quantity x and flow depth d obra of simulated spectra indicated that water column optical properties were accounted for by a shorter wavelength numerator band sensitive to scattering by suspended sediment while depth information was provided by a longer wavelength denominator band subject to strong absorption by pure water field spectra suggested that bottom reflectance was fairly homogeneous isolating the effect of depth and that radiance measured above the water surface was primarily reflected from the bottom not the water column obra of these data 28 of which were collected during a period of high turbidity yielded strong x versus d relations r2 from 0 792 to 0 976 demonstrating that accurate depth retrieval is feasible under field conditions moreover application of obra to hyperspectral image data resulted in spatially coherent hydraulically reasonable bathymetric maps though negative depth estimates occurred along channel margins where pixels were mixed this study indicates that passive optical remote sensing could become a viable tool for measuring river bathymetry copyright 2009 john wiley sons ltd

developments in monitoring and modelling small scale river bed topography recent research in fluvial geomorphology has emphasized the spatially distributed feedbacks amongst river channel topography flow hydraulics and sediment transport although understanding of the behaviour of dynamic river channels has been increased markedly through detailed within channel process studies less attention has been given to the accurate monitoring and terrain modelling of river channel form using three dimensional measurements however such information is useful in two distinct senses firstly it is one of the necessary boundary conditions for a physically based deterministic modelling approach in which three dimensional topography and river discharge drive within channel flow hydraulics and ultimately spatial patterns of erosion and deposition and therefore channel change secondly research has shown that an alternative means of estimating the medium term bedload transport rate can be based upon monitoring spatial patterns of erosion and deposition within the river channel this paper presents a detailed assessment of the distributed monitoring and terrain modelling of river bed topography using a technique that combines rigorous analytical photogrammetry with rapid ground survey the availability of increasingly sophisticated terrain modelling packages developed for civil engineering application allows the representation of topographic information as a landform surface intercomparison of landform surfaces allows visualization and quantification of spatial patterns of erosion and deposition a detailed assessment is undertaken of the quality of the morphological information acquired this allow some general comments to be made concerning the use of more traditional methods to monitor and represent small scale river channel morphology

carbon dioxide reaction processes in a model brine aquifer at 200 c and 200 bars implications for geologic sequestration of carbon the reactive behavior of supercritical co2 under conditions relevant to geologic storage and sequestration of c is largely unknown experiments were conducted in a flexible cell hydrothermal apparatus to determine the extent of fluid rock reactions in addition to carbonate mineral precipitation that may occur in a brine aquifer aquitard system that simulates a saline aquifer storage scenario the system was held at 200 c and 200 bars for 59 days 1413 h to approach steady state then injected with co2 and allowed to react for another 80 days 1924 h in addition to magnesite precipitation silicate minerals quartz plagioclase microcline and biotite in the aquifer and the aquitard display textures etch pits mineralization indicating significant reaction changes in elemental abundances in the brine following addition of co2 include ph decrease and enrichment in cl partly due to supercritical co2 desiccation of the brine geologic sequestration systems have potential for geochemical reactions that extend beyond simple aqueous dissolution of co2 and precipitation of carbonate these reactions may produce geochemical and geotechnical consequences for sequestration and provide important characteristics for monitoring and evaluation of stored co2 a n understanding of multi phase equilibrium relationships between supercritical co2 and aquifer brine systems also raises new questions for a variety of geologic systems multi phase fluid equilibria may for example account for the large amounts and heterogeneous distributions of calcite cement in a wide variety of geologic systems particularly in sedimentary basin sandstones published by elsevier science ltd

chicxulub impact the origin of reservoir and seal facies in the southeastern mexico oil fields stratigraphic and mineralogic studies of cretaceous tertiary k t boundary sections demonstrate that the offshore oil producing breccias and seals from oil fields in the campeche marine platform are of k t boundary age and that their mode of formation is probably related to the k t impact event at chicxulub the oil producing carbonate breccia and the overlying dolomitized ejecta layer seal found in several wells on the campeche marine platform contain typical chicxulub impact products such as shocked quartz and plagioclase and altered glass these offshore units are correlated with thick 50 300 m onshore breccia and impact ejecta layers found at the k t boundary in the guayal tabasco and bochil chiapas sections regionally the characteristic sequence is composed of from base to top coarse grained carbonate breccia covered by an ejecta bed and typical k t boundary clay the onshore and offshore breccia sequences are likely to have resulted from major slumping of the carbonate platform margin triggered by the chicxulub impact successive arrival times in this area 350 600 km from the crater of seismic shaking ballistic ejecta and tsunami waves fit the observed stratigraphic sequence the k t breccia reservoir and seal ejecta layer of the cantarell oil field with a current daily production of 1 3 million barrels of oil are probably the most important known oil producing units related to an impact event

spatial prediction of river channel topography by kriging topographic information is fundamental to geomorphic inquiry and spatial prediction of bed elevation from irregular survey data is an important component of many reach scale studies kriging is a geostatistical technique for obtaining these predictions along with measures of their reliability and this paper outlines a specialized framework intended for application to river channels our modular approach includes an algorithm for transforming the coordinates of data and prediction locations to a channel centered coordinate system several different methods of representing the trend component of topographic variation and search strategies that incorporate geomorphic information to determine which survey data are used to make a prediction at a specific location for example a relationship between curvature and the lateral position of maximum depth can be used to include cross sectional asymmetry in a two dimensional trend surface model and topographic breaklines can be used to restrict which data are retained in a local neighborhood around each prediction location using survey data from a restored gravel bed river we demonstrate how transformation to the channel centered coordinate system facilitates interpretation of the variogram a statistical model of reach scale spatial structure used in kriging and how the choice of a trend model affects the variogram of the residuals from that trend similarly we show how decomposing kriging predictions into their trend and residual components can yield useful information on channel morphology cross validation analyses involving different data configurations and kriging variants indicate that kriging is quite robust and that survey density is the primary control on the accuracy of bed elevation predictions the root mean square error of these predictions is directly proportional to the spacing between surveyed cross sections even in a reconfigured channel with a relatively simple morphology sophisticated methods of spatial prediction are no substitute for field data copyright 2007 john wiley sons ltd

remote measurement of river morphology via fusion of lidar topography and spectrally based bathymetry this study developed and evaluated a hybrid approach to remote measurement of river morphology that combines lidar topography with spectrally based bathymetry comparison of filtered lidar point clouds with surveyed cross sections indicated that subtle features on low relief floodplains were accurately resolved by lidar but that submerged areas could not be detected due to strong absorption of near infrared laser pulses by water the reduced number of returns made the active channel evident in a lidar point density map a second dataset suggested that pulse intensity also could be used to discriminate land from water via a threshold based masking procedure fusion of lidar and optical data required accurate co registration of images to the lidar and we developed an object oriented procedure for achieving this alignment information on flow depths was derived by correlating pixel values with field measurements of depth highly turbid conditions dictated a positive relation between green band radiance and flow depth and contributed to under prediction of pool depths water surface elevations extracted from the lidar along the water s edge were used to produce a continuous water surface that preserved along channel variations in slope subtracting local flow depths from this surface yielded estimates of the bed elevation that were then combined with lidar topography for exposed areas to create a composite representation of the riverine terrain the accuracy of this terrain model was assessed via comparison with detailed field surveys a map of elevation residuals showed that the greatest errors were associated with underestimation of pool depths and failure to capture cross stream differences in water surface elevation nevertheless fusion of lidar and passive optical image data provided an efficient means of characterizing river morphology that would not have been possible if either dataset had been used in isolation copyright 2011 john wiley sons ltd

effects of lateral confinement in natural and leveed reaches of a gravel bed river snake river wyoming usa this study examined the effects of natural and anthropogenic changes in confining margin width by applying remote sensing techniques fusing lidar topography with image derived bathymetry over a large spatial extent 58 km of the snake river wy fused dem s from 2007 and 2012 were differenced to quantify changes in the volume of stored sediment develop morphological sediment budgets and infer spatial gradients in bed material transport our study spanned two similar reaches that were subject to different controls on confining margin width natural terraces vs artificial levees channel planform in reaches with similar slope and confining margin width differed depending on whether the margins were natural or anthropogenic theeffects of tributaries also differed between the two reaches generally the natural reach featured greater confining margin widths and was depositional whereas artificial lateral constriction in the leveed reach produced a sediment budget that was closer to balanced although our remote sensing methods provided topographic data over a large area net volumetric changes were not statistically significant due to the uncertainty associated with bed elevation estimates we therefore focused on along channel spatial differences in bed material transport rather than absolute volumes of sediment to complement indirect estimates of sediment transport derived by morphological sediment budgeting we collected field data on bed mobility through a tracer study surface and subsurface grain size measurements were combined with bed mobility observations to calculate armoring and dimensionless sediment transport ratios which indicated that sediment supply exceeded transport capacity in the natural reach and vice versa in the leveed reach we hypothesize that constriction by levees induced an initial phase of incision and bed armoring because levees prevented bank erosion the channel excavated sediment by migrating rapidly across therestricted braidplain and eroding bars and islands

sedimentary signatures and processes during marine bolide impacts a review abstract studies of submarine impact craters resulting from impacts of comets or asteroids demonstrate that the presence of water and the physical properties of target rocks have a major influence on sedimentary processes associated with meteorite impacts this results in difference in sedimentary signature of bolide impacts in marine environments compared to subaerial impact craters in subaerial impacts the targets are commonly hard rocks frequently of igneous and or metamorphic origin whereas in submarine impacts the targets are mostly unconsolidated or poorly lithified sediments or sedimentary rocks with high volumes of pore water such differences result in variability in crater morphology and in sedimentary processes inside and outside the impact area impacts in shallow water marine neritic environments produced craters with low or absent rims and wide and shallow brims as characterize by both the montagnais on the scotian shelf the mjolnir in the barents sea 45 and 40 km in diameter respectively and the chesapeake bay 90 km in diameter lack of elevated rims is thought to be the result of current reworking and resurge of the water back into the excavated cavity as the water in the crater is vaporized during this process resurge gullies can be cut across the rim while mass and debris flows turbidites and other gravity deposits are produced as results of tsunami and crater wall and central high collapse during and after the crater excavation stage such deposits are found both within and outside the crater structure the only difference between gravity deposits triggered by an impact or other rare events such as earthquakes is the admixture of various melt particles and possible enrichments in iridium in the former impacts near the shelf edge may cause partial collapse of the continental margin as shown by the montagnais and chicxulub impacts some of the gravity and debris flows generated by margin collapse may be channelized with final deposits up to several hundred meters thick extending for hundreds of kilometers from the impact site other impact features such as shatter cones tektites spherules and ni spinels shocked quartz isotropication and partial melts are common to both submarine and subaerial impacts theoretical calculations of the destructive forces of mega tsunami waves triggered by meteorite impact in the ocean greatly exceed those based on geologic evidence a dearth of gigantic tsunami evidence for the chicxulub impact outside of the gulf of mexico where from theoretical modelling the maximum near bottom orbital velocity of water flow crossing the deep north atlantic basin should have been 1 m s could be the result of the mitigating effect of the bathymetry of surrounding area causing wave diffraction and interference calculated maximum horizontal orbital velocity near the seafloor at the shelf for the montagnais impact is 22 m s for a 200 m high wave 5 5 m s for a 50 m high wave at 500 km decreasing to 0 5 m s at 1000 km strong enough to scour the deep ocean bottom and produce distinct erosion surfaces and disconformities in marine sedimentary record however lack of cores across impact horizon prevents confirmation of occurrence of such bottom water flows

experimental study of potential wellbore cement carbonation by various phases of carbon dioxide during geologic carbon sequestration hydrated portland cement was reacted with co2 in supercritical gaseous and aqueous phases to understand the potential cement alteration processes along the length of a wellbore extending from a deep co2 storage reservoir to the shallow subsurface during geologic carbon sequestration the 3 d x ray microtomography xmt images showed that the cement alteration was significantly more extensive with co2 saturated synthetic groundwater than dry or wet supercritical co2 at high p 10 mpa t 50 c conditions scanning electron microscopy with energy dispersive spectroscopy sem eds analysis also exhibited a systematic ca depletion and c enrichment in cement matrix exposed to co2 saturated groundwater integrated xmt xrd and sem eds analyses identified the formation of an extensive carbonated zone filled with caco3 s as well as a porous degradation front and an outermost silica rich zone in cement after exposure to co2 saturated groundwater cement alteration by co2 saturated groundwater for 2 8 months overall decreased the porosity from 31 to 22 and the permeability by an order of magnitude cement alteration by dry or wet supercritical co2 was slow and minor compared to co2 saturated groundwater a thin single carbonation zone was formed in cement after exposure to wet supercritical co2 for 8 months or dry supercritical co2 for 15 months an extensive calcite coating was formed on the outside surface of a cement sample after exposure to wet gaseous co2 for 1 3 months the chemical physical characterization of hydrated portland cement after exposure to various phases of co2 indicates that the extent of cement carbonation can be significantly heterogeneous depending on the co2 phase present in the wellbore environment both experimental and geochemical modeling results suggest that wellbore cement exposure to supercritical gaseous and aqueous phases of co2 during geologic c sequestration is unlikely to damage the wellbore integrity because cement alteration by all phases of co2 is dominated by carbonation reactions this is consistent with previous field studies of wellbore cement with extensive carbonation after exposure to co2 for three decades however xmt imaging indicates that preferential cement alteration by supercritical co2 or co2 saturated groundwater can occur along the cement steel or cement rock interfaces this highlights the importance of further investigation of cement degradation along the interfaces of wellbore materials to ensure permanent geologic carbon storage published by elsevier ltd

a framework for modeling connections between hydraulics water surface roughness and surface reflectance in open channel flows this paper introduces a framework for examining connections between the flow field the texture of the air water interface and the reflectance of the water surface and thus evaluating the potential to infer hydraulic information from remotely sensed observations of surface reflectance we used a spatial correlation model describing water surface topography to illustrate the application of our framework nondimensional relations between model parameters and flow intensity were established based on a prior flume study expressing the model in the spatial frequency domain allowed us to use an efficient fourier transform based algorithm for simulating water surfaces realizations for both flume and field settings had water surface slope distributions positively correlated with velocity and water surface roughness however most surface facets were gently sloped and thus unlikely to yield strong specular reflections the model exaggerated the extent of water surface features leading to underestimation of facet slopes a ray tracing algorithm indicated that reflectance was greatest when solar and view zenith angles were equal and the sensor scanned toward the sun to capture specular reflections of the solar beam reflected energy was concentrated in a small portion of the sky but rougher water surfaces reflected rays into a broader range of directions our framework facilitates flight planning to avoid surface reflected radiance while mapping other river attributes or to maximize this component to exploit relationships between hydraulics and surface reflectance this initial analysis also highlighted the need for improved models of water surface topography in natural rivers

geomorphology within the interdisciplinary science of environmental flows article i nfo the field tradition in geomorphology informs beyond studying landforms by also providing a stage for understand ing how geomorphic elements influence the ecology of biota the intersection between fluvial geomorphology and riverine ecology represents an ideal confluence to examine the contribution of the geomorphic field tradition to en vironmental flows and show this area of riverine management as a research frontier for applied geomorphology environmental flows have consisted of a set of ecological based stream flow guidelines designed to inform sustain able water resource management that supports healthy riverine habitats and provides sufficient water supply for society geomorphological understanding is central to environmental flows because it is the interaction between flow form and substrate that influences habitat type condition availability and biotic use across space and time this relationship varies longitudinally laterally vertically overtime and across macro to mesoscale morphologies withintheriverine environment thegeomorphictemplateis therefore asintegralasthe flow wereviewedstudies where field evidence indicated that geomorphology impacts the effectiveness of environmental flow strategies and wemakethecasefortheneedtoincreasegeomorphic considerationsinenvironmental flows although flow iscom monly referred toas themaster variablein environmental flows geomorphologymediatestheeffectsof flow regime on ecological processes concepts and applications from this perspective on the role of geomorphology in riverine ecosystem research will inform the practice policy and implementation of environmental flows

numerical modeling of impact induced modifications of the deep sea floor abstract the mechanics of oceanic impact events differ in several respects from the process that accompanies the strike of an asteroid on land in order to explore the cratering process on a water covered target a series of 2d hydrocode simulations for impact velocities of 10 15 20 and 30 km s and water depth diameter ratios between 5 and 7 have been carried out in particular these simulations were aimed to examine the effects of the asteroid on the deep sea floor the interaction of the impacting body and the water column causes loss of the body s kinetic energy both through oceanic drag and through mass loss due to hydrodynamic heating prior to hitting the ocean bottom regardless of whether the impactor actually hits the ocean floor the shock wave generated in the water column by the impact of the body on the water surface will leave behind unique traces in the marine sediments for example an asteroid of 1 km in diameter arriving at the ocean surface with a velocity of 20 km s induces a shock pressure of 6 gpa in the oceanic crust at a water depth of 5 km the passage of the shock wave along the water ocean bottom interface causes significant disturbance in the sediment layer moreover the collapse of the transient cavity that results from the passage of the projectile through the water column causes a strong surge of water that generates a displacement and redeposition of sediments on the ocean floor in order to examine sediment transport processes we introduce computationally a large amount of massless particles within the projectile and the target material and follow the movement of each individual particle tracer particles represent only forced material movement and do not account for any frictional forces thus comparisions with real sediment disturbances may be qualitative only for an impact velocity of 20 km s and a water depth diameter ratio of 5 this procedure reveals significant particle movements within a distance of 15 km from the center of the impact the only known deep sea impact structure so far the eltanin impact in the bellingshausen sea antarctica is characterized by a zone of chaotically mixed sediments that most probably originated from impact induced turbulent water currents based on the present observations which do not allow the identification of an impact structure at the ocean bottom our model yields estimates of a projectile diameter of 1 km and an impact velocity of 20 km s

removing sun glint from optical remote sensing images of shallow rivers sun glint is the specular reflection of light from the water surface which often causes unusually bright pixel values that can dominate fluvial remote sensing imagery and obscure the water leaving radiance signal of interest for mapping bathymetry bottom type or water column optical characteristics although sun glint is ubiquitous in fluvial remote sensing imagery river specific methods for removing sun glint are not yet available we show that existing sun glint removal methods developed for multispectral images of marine shallow water environments over correct shallow portions of fluvial remote sensing imagery resulting in regions of unreliable data along channel margins we build on existing marine glint removal methods to develop a river specific technique that removes sun glint from shallow areas of the channel without overcorrection by accounting for non negligible water leaving near infrared radiance this new sun glint removal method can improve the accuracy of spectrally based depth retrieval in cases where sun glint dominates the at sensor radiance for an example image of the gravel bed snake river wyoming usa observed vs predicted r2 values for depth retrieval improved from 0 66 to 0 76 following sun glint removal the methodology presented here is straightforward to implement and could be incorporated into image processing workflows for multispectral images that include a near infrared band this article is protected by copyright all rights reserved

wellbore cement fracture evolution at the cement basalt caprock interface during geologic carbon sequestration abstract composite portland cement basalt caprock cores with fractures as well as neat portland cement columns were prepared to understand the geochemical and geomechanical effects on the integrity of wellbores with defects during geologic carbon sequestration the samples were reacted with co 2 saturated groundwater at 50 c and 10 mpa for 3 months under static conditions while one cement basalt core was subjected to mechanical stress at 2 7 mpa before the co 2 reaction micro xrd and sem eds data collected along the cement basalt interface after 3 month reaction with co 2 saturated groundwater indicate that carbonation of cement matrix was extensive with the precipitation of calcite aragonite and vaterite whereas the alteration of basalt caprock was minor x ray microtomography xmt provided three dimensional 3 d visualization of the opening and interconnection of cement fractures due to mechanical stress computational fluid dynamics cfd modeling further revealed that this stress led to the increase in fluid flow and hence permeability after the co 2 reaction xmt images displayed that calcium carbonate precipitation occurred extensively within the fractures in the cement matrix but only partially along the fracture located at the cement basalt interface the 3 d visualization and cfd modeling also showed that the precipitation of calcium carbonate within the cement fractures after the co 2 reaction resulted in the disconnection of cement fractures and permeability decrease the permeability calculated based on cfd modeling was in agreement with the experimentally determined permeability this study demonstrates that xmt imaging coupled with cfd modeling represent a powerful tool to visualize and quantify fracture evolution and permeability change in geologic materials and to predict their behavior during geologic carbon sequestration or hydraulic fracturing for shale gas production and enhanced geothermal systems

mapping gravel bed river bathymetry from space 1 understanding river form and behavior requires an efficient means of measuring channel morphology this study evaluated the potential to map the bathymetry of two clear flowing shallow 3 m deep gravel bed rivers 60 m wide from 2 m pixel worldview2 satellite images direct measurements of water column optical properties were used to quantify constraints on depth retrieval the smallest detectable change in depth was 0 01 0 04 m and the maximum detectable depth was 5 m in green bands but 2 m in the near infrared lower sensor radiometric resolution yields less precise estimates over a smaller range an algorithm for calibrating a band ratiox to field measurements of depth d proved effective when applied to spectra extracted from images r2 0 822 and 0 594 for the larger and smaller stream respectively or measured in the field r2 0 769 and 0 452 this procedure also identified optimal wavelength combinations but different bands were selected for each site accuracy assessment of bathymetric maps produced using various calibration approaches and image types indicated that 1 a linear d vs xrelation provided depth estimates nearly as accurate as a quadratic formulation 2 panchromatic and pan sharpened multispectral images with smaller 0 5 m pixels did not yield more reliable depth estimates than the original images and 3 depth retrieval was less reliable in pools due to saturation of the radiance signal this investigation thus demonstrated the feasibility as well as the limitations of measuring the bathymetry of clear shallow gravel bed rivers from space

sedimentological analysis of resurge deposits at the lockne and tvaren craters clues to flow dynamics the lockne and tvren craters formed about 455 million years ago in an epicontinental sea where seawater and mainly limestones covered a crystalline basement the target water depth for tvaren apparent basement crater diameter d 2 km was probably not over 150 m and for lockne d 7 5 km recent best fit numerical simulations suggest the target water depth of 500 700 m lockne has crystalline ejecta that partly cover an outer crater 14 km diameter apparent in the target sediments tvren is eroded with only the crater infill preserved we have line logged cores through the resurge deposits within the craters in order to analyze the resurge flow the focus was clast lithology frequencies and size sorting we divide the resurge into resurge proper with water and debris shooting into the crater and ultimately rising into a central water plume anti resurge with flow outward from the collapsing plume and oscillating resurge not covered by the line logging due to methodological reasons with decreasing flow in diverse directions at lockne the deposit of the resurge proper is coarse and moderately sorted whereas the anti resurge deposit is fining upwards and better sorted the tvren crater has a smoothly fining up section deposited by the resurge proper and may lack anti resurge deposits at lockne the content of crystalline relative to limestone clasts generally decreases upwards which is the opposite of tvren this may be a consequence of factors such as crater size i e complex versus simple and the relative target water depth the mean grain size i e the mean phi value per meter and standard deviation i e size sorting for both craters can be expressed by the equation 0 60 1 25

age measurement of the submarine montagnais impact crater seven laser generated 40ar 39ar age spectra of melt rocks from the newly described submarine montagnais crater are presented while the age spectra are not completely straight forward to interpret the evidence is very strong that the impact occurred approximately 51 m y ago thus the montagnais event is associated with neither the k t nor the north american tektite events such an age is also totally out of phase with the 26 32 m y cycles proposed recently for the meteorite impact and extinction records as it falls roughly midway between two of the most precisely dated points in such proposed cycles the k t boundary and the north american tektite event

very high spatial resolution imagery for channel bathymetry and topography from an unmanned mapping controlled platform the increasing availability of aerial photography and satellite imagery offers new possibilities for characterizing river morphology the precision of new very high resolution vhr images allows smaller scale objects within river corridors to be studied high survey frequencies provide increased opportunities for the monitoring of river restoration following this evolution in platform technology a small radio controlled motorized vehicle flying at low altitude was used to study both channel water depth and gravel bar geometry the vhr imagery provided by this equipment allowed both channel bathymetry and a high accuracy photogrammetric digital elevation model dem to be realized using case studies from the ain and the drome rivers in france the accuracy of the results is presented and the various challenges associated with the new platform are discussed one significant issue is that due to the low elevation of the survey the coverage of a target area is usually based on several photographs which leads to variations in illumination conditions that stem from atmospheric changes the images were processed to minimize this source of error but a number of issues have yet to be resolved bathymetric models with r2 values between 0 59 and 0 90 were created in spite of the lack of channel bed homogeneity at the various sites the gravel bar was also effectively mapped and the photogrammetrically predicted dem provided a 5 10 cm pixel resolution with a vertical precision between 2 and 40 cm according to the position within the image this paper shows that despite unstable image acquisition unmanned radio controlled platforms provide significant advantages for the study of river processes offering a flexible very high resolution data source for both channel bathymetry and gravel bar topography copyright 2007 john wiley sons ltd

evaluating the potential for remote bathymetric mapping of a turbid sand bed river 2 application to hyperspectral image data from the platte river 1 this study examined the possibility of mapping depth from optical image data in turbid sediment laden channels analysis of hyperspectral images from the platte river indicated that depth retrieval in these environments is feasible but might not be highly accurate four methods of calibrating image derived depth estimates were evaluated the first involved extracting image spectra at survey point locations throughout the reach these paired observations of depth and reflectance were subjected to optimal band ratio analysis obra to relate r2 0 596 a spectrally based quantity to flow depth two other methods were based on obra of data from individual cross sections a fourth strategy used ground based reflectance measurements to derive an obra relation r2 0 944 that was then applied to the image depth retrieval accuracy was assessed by visually inspecting cross sections and calculating various error metrics calibration via field spectroscopy resulted in a shallow bias but provided relative accuracies similar to image based methods reach aggregated obra was marginally superior to calibrations based on individual cross sections and depth retrieval accuracy varied considerably along each reach errors were lower and observed versus predicted regression r2 values higher for a relatively simple deeper site than a shallower braided reach errors were 1 3 and 1 2 the mean depth for the two reaches bathymetric maps were coherent and hydraulically reasonable however and might be more reliable than implied by numerical metrics as an example application linear discriminant analysis was used to produce a series of depth threshold maps for characterizing shallow water habitat for roosting cranes

geostatistical estimations of bathymetric lidar errors on rivers the geometry of river channels is a key descriptive element for hydromorphology hydraulics and hydroecology gravel bed rivers usually have a mean water depth of 0 5 m for such shallow waters the accuracy of bathymetric lidar data has to be precisely assessed alongside this accuracy investigation methodological questions arise how to assess the data quality of elevation lidar when comparing reference topographic points on river beds to laser beam footprints of several square metres at different locations what are the consequences of uncertainties and scaling in accuracy estimations in this study we designed a methodology to assess the quality of lidar topographical data within rivers using a specific geostatistical method that conducts upscaling as well as interpolation of reference data that takes into account uncertainties this method uses an anisotropic block kriging from dgps points on lidar footprint areas within a channel fitted coordinate system this assessment focused on a 1 5 km long reach of the gardon gravel bed river in the south of france dgps points pseudo regularly located along the river were acquired at the same time as the lidar survey with the hawkeyeii system lidar accuracy results for river bottom elevation show a negative bias for high depth added to that bias a random error with 0 32 m standard deviation was found by considering upscaling and uncertainties in reference data and a 0 20 m standard deviation was found if they were not considered consequently if lidar bias can be corrected measuring a water depth less than 32 cm i e for 28 of the river area is unrealistic however this experiment shows that lidar provides an accurate representation of the riverbed forms it also provided a useful continuous topographic surface from the underwater river bed up to riparian areas copyright 2010 john wiley and sons ltd

monitoring and modelling morphological change in a braided gravel bed river using high resolution gps based survey recent research in fluvial geomorphology has emphasized the direct monitoring of channel topography as a useful tool to better understand the interrelationship between river form and process and in particular to estimate bedload transport rates and reach scale sediment budgets until recently however this morphometric approach has been limited to comparison of repeatedly surveyed cross sections with the associated problems of low frequency sampling and an emphasis on cross stream as opposed to downstream morphological dynamics recent advances in analytical photogrammetry have however permitted the acquisition of data at sufficient resolutions to represent macroform 101 m and microform 10 m channel geometry in fully three dimensions while inherently spatially distributed the photogrammetric approach to land surveying is however restricted to observable areas of the channel and is thus of limited use in the subaqueous zone especially if flows are turbid or highly coloured this paper presents an alternative approach to the study of three dimensional morphological dynamics of a divided reach of the gravelly river feshie scotland in which topographic survey of both exposed and submerged areas of the reach was undertaken using the global positioning system gps survey results from two field programmes in 1998 and 1999 are presented in which a geotronics geotracer 2000 real time kinematic gps receiving unit was used to survey a 200 80 m reach rapid radial survey methods were employed permitting the collection of 2000 survey points per day giving a mean density over the 13 ha reach of 1 1 points per square metre a detailed assessment of survey errors and dem quality is presented and a limit of detection of c 10 cm proposed as an upper threshold for the identification of significant change between dems preliminary interpretation of channel dynamics in 1998 99 reveals relatively little change to the overall macroscale reach structure dem differencing techniques however highlight important local changes including the progradation of submerged bar fronts bar head aggradation and scour along major channel thalwegs and the erosion of fines from sloughs copyright 2000 john wiley sons ltd

high resolution basin extent observations and implications for understanding river form and process fifty years of fluvial studies have posited a variety of conceptual frameworks for characterizing river forms and processes throughout entire basins including hydraulic geometry the river continuum concept self organized criticality and sediment links this article uses basin extent high resolution observations of fluvial forms in the nueces river basin texas and yellowstone national park to evaluate the ability of these frameworks to characterize system behavior across a multitude of scales the nueces data were collected with remote sensing methods and the yellowstone data were collected through extensive field surveys the data resolution spatial extent and quality of these data sets allow direct comparison between the two areas the hyperscale comparison supports using of each these frameworks at specific scales but also indicates an irreducible amount of variation in both datasets across many different scales that is not captured by the conceptual frameworks moreover the scales and locations where one framework such as hydraulic geometry works well are often not the same scales and locations where another framework such as the river continuum concept works well because the conceptual frameworks appear to operate at scales and locations distinct from one another the measurement approaches necessary to observe them must also be at different scales and locations for example seeing self organized criticality in a river system is difficult without an extensive survey through space whereas the recognition of sediment links requires quite intense sampling in specific river regions we suggest that these separations between measurement scales represent an incommensurability issue in river studies making it very difficult to both communicate among and test between two or more competing theories making simultaneous hyperscale observations of the river is one approach to minimizing the theory ladeness of observation as deviations from different predictions can be plotted at every scale copyright 2010 john wiley sons ltd

ancient impact structures on modern continental shelves the chesapeake bay montagnais and toms canyon craters atlantic margin of north america abstract three ancient impact craters chesapeake bay 35 7 ma toms canyon 35 7 ma montagnais 51 ma and one multiring impact basin chicxulub 65 ma are currently known to be buried beneath modern continental shelves all occur on the passive atlantic margin of north america in regions extensively explored by seismic reflection surveys in the search for oil and gas reserves we limit our discussion herein to the three youngest structures these craters were created by submarine impacts which produced many structural and morphological features similar in construction composition and variability to those documented in well preserved subaerial and planetary impact craters the subcircular chesapeake bay diameter 85 km and ovate montagnais diameter 45 50 km structures display outer rim scarps annular troughs peak rings inner basins and central peaks similar to those incorporated in the widely cited conceptual model of complex impact craters these craters differ in several respects from the model however for example the montagnais crater lacks a raised lip on the outer rim the chesapeake bay crater displays only small remnants of a raised lip and both craters contain an unusually thick body of impact breccia the subtriangular toms canyon crater diameter 20 22 km on the other hand contains none of the internal features of a complex crater nor is it typical of a simple crater it displays a prominent raised lip on the outer rim but the lip is present only on the western side of the crater in addition each of these craters contains some distinct features which are not present in one or both of the others for example the central peak at montagnais rises well above the elevation of the outer rim whereas at chesapeake bay the outer rim is higher than the central peak the floor of the toms canyon crater is marked by parallel deep troughs and linear ridges formed of sedimentary rocks whereas at chesapeake bay the crater floor contains concentric faults and compression ridges formed in rocks of the crystalline basement the chesapeake bay crater is distinguished further by its cluster of at least 23 adjacent secondary craters the north american tektite strewn field a widespread deposit of distal ejecta is thought to be derived from the chesapeake bay impact perhaps with a small contribution from the toms canyon impact no ejecta field is known to be associated with the montagnais impact no immediate major extinction event is directly linked to any of these three impacts there is evidence however that the chesapeake bay and toms canyon impacts helped initiate a long term pulse of warm global climate whose eventual dissipation coincided with an early oligocene mass extinction event 2 ma after the impacts

smart sdb sample specific multiple band ratio technique for satellite derived bathymetry abstract spectrally based retrieval of bathymetry is challenging in inland coastal waters due to variations in factors other than water depth across a water body including bottom type optically significant constituents water surface roughness and others optimal band ratio analysis obra is the most widely used method to deal with these confounding effects to retrieve water depth obra identifies the pair of bands that provides the highest accuracy among all possible pairs when using a log transformed band ratio model however this approach fits a single ratio model to all training samples without fully accounting for the heterogeneity of the aforementioned complicating factors to deal with this problem we introduce a novel method called sample specific multiple band ratio technique for satellite derived bathymetry smart sdb the proposed smart sdb technique partitions the feature space of the spectral data and creates for every subspace a different band ratio model that performs better than the other models within that subspace bathymetry is then predicted based on the closest model s in the feature space by performing a sample specific k nearest neighbor k nn analysis the depth estimates provided by the neighboring models are averaged with weights proportional to their inverse distance in the feature space the proposed method can be used in both inland and coastal waters here we thoroughly examine its effectiveness in the challenging and heterogenous environments of fluvial systems using a wide range of spectral data including radiative transfer simulations an airborne hyperspectral image of the snake river usa and a worldview 3 satellite image of the sarca river italy the results of this study indicate a significant improvement in depth retrieval for estimations based on the smart sdb method relative to standard obra either when a single model or multiple models are employed

when a cosmic impact strikes the sea bed most bolides that collide with the earth hit the sea limited knowledge about marine target impacts hampers predictions about their perilousness this study presents geological features that are particular to craters formed at sea the features are most likely a result of the influence of the target on the cratering process marine target craters form only if the target sea is shallow enough to admit sufficient kinetic energy into the sea bed when the crater diameter is large compared to the water depth the crater resembles its counterparts that are formed on land craters formed in deeper water are concentric and often lack melt sheets and rim walls but have deposits and radial gullies formed by the resurge of the sea impacts on the deep shelf are probably much more energetic than is suggested by the dimensions of the preserved crater

a geostatistical framework for quantifying the reach scale spatial structure of river morphology 1 variogram models related metrics and relation to channel form abstract fluvial geomorphology is fundamentally concerned with the association between form and process in rivers examining these interactions in complex natural channels requires a means of quantifying the variability and organization of bed topography this paper introduces a geostatistical framework for characterizing reach scale spatial structure transformation to a channel centered coordinate system allows topographic variations to be resolved into along and across stream components dimensionless variables obtained by scaling distances by the mean channel width and de trended elevations by the mean bankfull depth account for channel size and allow spatial patterns to be compared over time or among sites these patterns are effectively described by the variogram a spatial statistic that expresses dissimilarity as a function of distance fitting a parametric model to the sample variogram provides a rich description of channel form for example multiple nested structures can be combined to account for anisotropy with varying degrees of spatial variability observed over different length scales along and across the channel integral metrics derived from the variogram model yield a more compact summary and variogram maps a useful visualization to guide interpretation of these metrics i used a simple channel builder to isolate the effects of specific aspects of river morphology on the variogram this analysis indicated that geostatistical models were sensitive to changes in the size shape and orientation of channel features but not to a pure translation of the morphology the results also highlighted the importance of considering streamwise and transverse components jointly rather than in isolation

satellite based remote sensing of running water habitats at large riverscape scales tools to analyze habitat heterogeneity for river ecosystem management abstract we illustrate an approach to quantify patterns in hydraulic habitat composition and local heterogeneity applicable at low cost over very large river extents with selectable reach window scales ongoing developments in remote sensing and geographical information science massively improve efficiencies in analyzing earth surface features with the development of new satellite sensors and drone platforms and with the lowered cost of high resolution multispectral imagery fluvial geomorphology is experiencing a revolution in mapping streams at high resolution exploiting the power of aerial or satellite imagery is particularly useful in a riverscape research framework fausch et al 2002 where high resolution sampling of fluvial features and very large coverage extents are needed this study presents a satellite remote sensing method that requires very limited field calibration data to estimate over various scales ranging from 1 m to many tens or river kilometers i spatial composition metrics for key hydraulic mesohabitat types and ii reach scale wetted habitat heterogeneity indices such as the hydromorphological index of diversity hmid when the purpose is hydraulic habitat characterization applied over long river networks the proposed method although less accurate is much less computationally expensive and less data demanding than two dimensional computational fluid dynamics cfd here we illustrate the tools based on a worldview 2 satellite image of the kiamika river near mont laurier quebec canada specifically over a 17 km river reach below the kiamika dam in the first step a high resolution water depth d map is produced from a spectral band ratio calculated from the multispectral image calibrated with limited field measurements next based only on known river discharge and estimated cross section depths at time of image capture empirical based pseudo 2d hydraulic rules are used to rapidly generate a two dimensional map of flow velocity v over the 17 km kiamika reach the joint distribution of d and v variables over wetted zones then is used to reveal structural patterns in hydraulic habitat availability at patch reach and segment scales here we analyze 156 bivariate d v density function plots estimated over moving reach windows along the satellite scene extent to extract 14 physical habitat metrics such as river width mean and modal depths and velocity variances and covariance in d and v over 1 m pixels hmid entropy a principal component analysis on the set of metrics is then used to cluster river reaches in regard to similarity in their hydraulic habitat composition and heterogeneity applications of this approach can include i specific fish habitat detection at riverscape scales e g large areas of riffle spawning beds deeper pools for regional management ii studying how river habitat heterogeneity is correlated to fish distribution and iii guidance for site location for restoration of key habitats or for post regulation monitoring of representative reaches of various types

sediment slides and turbidity currents on the laurentian fan sidescan sonar investigations near the epicenter of the 1929 grand banks earthquake the epicenter area of the 1929 grand banks earthquake on the continental slope south of newfoundland has been investigated using sea marc i a deeply towed midrange sidescan sonar with a 4 5 khz subbottom profiler shallow slides pass downslope into debris flows on the muddy continental slope east of the epicenter at the head of the eastern valley of the laurentian fan west of the epicenter arcuate slide scars cut undisturbed upper slope sediment and lead downslope to a lineated erosional seabed at a water depth of about 1600 m this erosional seabed passes into extensive fields of 100 m wavelength gravel waves situated on the broad irregular valley floor the gravel waves become better developed downslope and extend at least to water depths of 3000 m all these morphological features appear fresh on the sidescan sonograms suggesting that they date from the 1929 earthquake event and the distribution of slides corresponds to the area of instantaneous cable breaks in 1929 the upper limit of erosion on valley walls suggests that the 1929 turbidity current was less than 300 m thick timing of cable breaks downfan suggests that flow velocities were sufficient to rework gravel deposits into large bedforms during waning flow stages over elevated areas of the valley floor similar cross bedded coarse sands and gravels are common in ancient channel deposits

mass failure of the north atlantic margin triggered by the cretaceous paleogene bolide impact the 65 ma chicxulub impact is known to have triggered large submarine slope failures near the crater in the gulf of mexico and caribbean here we show that the impact also precipitated massive submarine failure of the continental margin around the western north atlantic we have identified mass flow deposits containing impact ejecta of cretaceous paleogene boundary age in two deep sea cores more than 700 km from the continental margin the mass flows must have originated from the continental margin because they contain microfossils typical of shallow water environments and sedimentary features indicative of deposition by gravity currents geophysical data suggest that the mass wasting deposits may be present over the entire western north atlantic from puerto rico to the grand banks of canada and that much of the eastern margin of north america catastrophically failed during the cretaceous paleogene impact

downstream effects of impounding a natural lake the snake river downstream from jackson lake dam wyoming usa a sediment mass balance constructed for a 16 km reach of the snake river downstream from jackson lake dam jld indicates that river regulation has reduced the magnitude of sediment mass balance deficit that would naturally exist in the absence of the dam the sediment budget was constructed from calibrated bed load transport relations which were used to model sediment flux into and through the study reach calibration of the transport relations was based on bed load transport data collected over a wide range of flows on the snake river and its two major tributaries within the study area in 2006 and 2007 comparison of actual flows with unregulated flows for the period since 1957 shows that operations of jld have reduced annual peak flows and increased late summer flows painted tracer stones placed at five locations during the 2005 spring flood demonstrate that despite the reduction in flood magnitudes common floods are capable of mobilizing the bed material the sediment mass balance demonstrates that more sediment exits the study reach than is being supplied by tributaries however the volume of sediment exported using estimated unregulated hydrology indicates that the magnitude of the deficit would be greater in the absence of jld calculations suggest that the snake river was not in equilibrium before construction of jld but was naturally in sediment deficit the conclusion that impoundment lessened a natural sediment deficit condition rather than causing sediment surplus could not have been predicted in the absence of sediment transport data and highlights the value of transport data and calculation of sediment mass balance in informing dam operations copyright 2011 john wiley sons ltd

diffuse reflectance of oceanic shallow waters influence of water depth and bottom albedo we used simplifying assumptions to derive analytical formulae expressing the reflectance of shallow waters as a function of observation depth and of bottom depth and albedo these formulae also involve two apparent optical properties of the water body a mean diffise attenuation coefficient and a hypothetical reflectance which would be observed if the bottom was infinitely deep the validity of these approximate formulae was tested by comparing their outputs with accurate solutions of the radiative transfer obtained under the same boundary conditions by monte carlo simulations these approximations were also checked by comparing the reflectance spectra for varying bottom depths and compositions determined in coastal lagoons with those predicted by the formulae these predictions were based on separate determinations of the spectral albedos of typical materials covering the floor such as coral sand and various green or brown algae the simple analytical expressions are accurate enough for most practical applications and also allow quantitative discussion of the limitations of remote sensing techniques for bottom recognition and bathymetry as early as 1944 duntley used a spectrograph mounted in a glass bottomed boat or flown in an airplane to analyze radiances emerging from the ocean and shallow waters he evidenced the influence of the water depth on the spectral composition of the upward flux duntley 1963 using a monte carlo technique plass and kattawar 1972 calculated the radiative field in the atmosphere cean system and in particular examined the dependence of the upward flux on the albedo of the ocean floor gordon and brown 1974 studied the diffuse reflectance of a shallow ocean using monte carlo simulations and a probabilistic approach gordon and brown provided an analysis based on photon history of the light field as modified by the presence of a reflecting bottom in addition ackleson and klemas 1986 developed a two flow model that simulated the light field within a canopy of bottom adhering plants a single scattering approximation for irradiance reflectance was also

seismic stratigraphic correlation across the new england seamounts western north atlantic ocean correlation in the western north atlantic basin of deep water seismic stratigraphy across a basement high within the new england seamounts shows that the seismic sequence of the nova scotian rise is broadly similar to that off the united states time of seamount volcanism inferred from stratigraphic relations around the basement high is consistent with a hot spot origin but nearby stratigraphic data indicate that earlier and later eruptions occurred suggesting lithospheric weakness that predisposed this area to volcanism patterns of tertiary abyssal current erosion and sediment deposition were controlled by sea floor morphology around the seamounts and interaction of abyssal currents with the gulf stream

recent large magnitude floods and their impact on valley floor environments of northeastern yellowstone abstract the lamar river watershed of northeastern yellowstone contains some of the most diverse and important habitat in the national park broad glacial valley floors feature grassland winter range for ungulates riparian vegetation that provides food and cover for a variety of species and alluvial channels that are requisite habitat for native fish rapid neogene uplift and quaternary climatic change have created a dynamic modern environment in which catastrophic processes exert a major influence on riverine riparian ecosystems uplift and glacial erosion have generated high local relief and extensive cliffs of friable volcaniclastic bedrock as a result steep tributary basins produce voluminous runoff and sediment during intense precipitation and rapid snowmelt recent major floods on trunk streams deposited extensive overbank gravels that replaced loamy soils on flood plains and allowed conifers to colonize valley floor meadows tree ring dating identifies major floods in 1918 ca 1873 and possibly ca 1790 in 1996 and 1997 discharge during snowmelt runoff on soda butte creek approached the 100 year flood estimated by regional techniques with substantial local bank erosion and channel widening indirect estimates show that peak discharges in 1918 were approximately three times greater than in 1996 with similar duration and much greater flood plain impact nonetheless 1918 peak discharge reconstructions fall well within the range of maximum recorded discharges in relation to basin area in the upper yellowstone region the 1873 and 1918 floods produced lasting impacts on the channel form and flood plain of soda butte creek channels may still be locally enlarged from flood erosion and net downcutting has occurred in some reaches leaving the pre 1790 flood plain abandoned as a terrace gravelly overbank deposits raise flood plain surfaces above levels of frequent inundation and are well drained therefore flood plain soils are drier noncohesive gravels also reduce bank stability and may have persistent effects on channel form overall floods are part of a suite of catastrophic geomorphic processes that exert a very strong influence on landscape patterns and valley floor ecosystems in northeastern yellowstone

identifying geochemical reactions on wellbore cement caprock interface under sequestration conditions the integrity of wells which are key components for co2 sequestration depends mainly on the seal between the wellbore cement and the geologic formation to identify the reaction products that may alter the cement caprock interface batch experiments and computer modelling were conducted and analysed over time the dissolution and precipitation of minerals alters the physical properties of the interface including its tightness one main objective of the simulation was thus to analyse the evolution of the porosity of cement and caprock over time the alteration of the cement caprock interface was identified as a complex problem and differentiated depending on rock type the characteristic feature of a cement shale contact zone is the occurrence of a highly carbonated compacted layer within the shale which in turn causes cement shale detachment in the case of a cement anhydrite interface the most important reaction is severe anhydrite dissolution secondary calcite precipitation takes place in deeper parts of the rock the cement rock contact zone is prone to rapid mineral dissolution which contributes to increased porosity and may alter the well integrity comparison of computer simulations with autoclave experiments enabled the adjustment of unknown parameters this enhances the knowledge of these particular assemblages overall a good match was obtained between experiments and simulations which enhances confidence in using models to predict longer term evolution

remote sensing of stream depths with hydraulically assisted bathymetry hab models this article introduces a technique for using a combination of remote sensing imagery and open channel flow principles to estimate depths for each pixel in an imaged river this technique which we term hydraulically assisted bathymetry hab uses a combination of local stream gage information on discharge image brightness data and manning based estimates of stream resistance to calculate water depth the hab technique does not require ground truth depth information at the time of flight hab can be accomplished with multispectral or hyperspectral data and therefore can be applied over entire watersheds using standard high spatial resolution satellite or aerial images hab also has the potential to be applied retroactively to historic imagery allowing researchers to map temporal changes in depth we present two versions of the technique hab 1 and hab 2 hab 1 is based primarily on the geometry discharge and velocity relationships of river channels manning s equation assuming average depth approximates the hydraulic radius the discharge equation and the assumption that the frequency distribution of depths within a cross section approximates that of a triangle are combined with discharge data from a local station width measurements from imagery and slope measurements from maps to estimate minimum average and maximum depths at a multiple cross sections these depths are assigned to pixels of maximum average and minimum brightness within the cross sections to develop a brightness depth relation to estimate depths throughout the remainder of the river hab 2 is similar to hab 1 in operation but the assumption that the distribution of depths approximates that of a triangle is replaced by an optical beer lambert law of light absorbance in this case the flow equations and the optical equations are used to iteratively scale the river pixel values until their depths produce a discharge that matches that of a nearby gage r 2 values for measured depths versus depths estimated by hab 1 and hab 2 are 0 51 and 0 77 respectively in the relatively simple brazos river texas r 2 values for hab 1 and hab 2 are 0 46 and 0 26 respectively in the lamar river a complex mountain river system in yellowstone national park although the r 2 values are moderate depth maps and crosssections derived from the hab techniques are consistent with typical stream geomorphology patterns and provide far greater

making riverscapes real abstract the structure and function of rivers have long been characterized either by 1 qualitative models such as the river continuum concept or serial discontinuity concept which paint broad descriptive portraits of how river habitats and communities vary or 2 quantitative models such as downstream hydraulic geometry which rely on a limited number of measurements spread widely throughout a river basin in contrast authors such as fausch et al 2002 and wiens 2002 proposed applying existing quantitative spatially comprehensive ecology and landscape ecology methods to rivers this new framework for river sciences which preserves variability and spatial relationships is called a riverine landscape or a riverscape application of this riverscape concept requires information on the spatial distribution of organism scale habitats throughout entire river systems this article examines the ways in which recent technical and methodological developments can allow us to quantitatively implement and realize the riverscape concept using 3 cm true color aerial photos and 5 m resolution elevation data from the river tromie scotland we apply the newly developed fluvial information system which integrates a suite of cutting edge high resolution remote sensing methods in a spatially explicit framework this new integrated approach allows for the extraction of primary fluvial variables such as width depth particle size and elevation from these first order variables we derive second order geomorphic and hydraulic variables including velocity stream power froude number and shear stress channel slope can be approximated from available topographic data based on these first and second order variables we produce riverscape metrics that begin to explore how geomorphic structures may influence river habitats including connectivity patchiness of habitat and habitat distributions the results show a complex interplay of geomorphic variable and habitat patchiness that is not predicted by existing fluvial theory riverscapes thus challenge the existing understanding of how rivers structure themselves and will force development of new paradigms

wellbore cement degradation in contact zone with formation rock in the work the risk of co2 migration in deep wells caused by integrity loss on cement rock interface and thow wellbore integrity correlated with the formation rock lithology were determined 19 composed samples of rock and wellbore cement were exposed to co2 saturated brine in the autoclave reactor under the formation conditions 50 c and 10 mpa mineralogical and textural changes in the cement rock interface in the case of selected rocks sandstones shale limestones dolomites and anhydrites were characterised the performed examination indicates that both cement and formation rocks react with co2 saturated brine under the experimental conditions the cement alteration is characterised by carbonation process in the outer rim but it is enhanced on the interface with formation rock it was stated that the performance of the cement rock interface is essentially dependent on the rock lithology including mineral composition and rock structure some minerals are very easily dissolving e g anhydrite gypsum calcite and feldspars what is contributing to an increase in the porosity and permeability in cement rock contact zone primary dissolution of certain minerals in the first stages of the experiment results in the secondary precipitation after the last stage of reaction contributing to a secondary reduction of pore space

gordo megabed a possible seismite in a tortonian submarine fan tabernas basin province almeria southeast spain abstract the mainly tortonian sediments of the tabernas basin contain the elements of a well developed small submarine fan synsedimentary unconformities and randomly intercalated megabeds in both basin plain and fan lobe deposits indicate tectonic activity during fan growth one of the megabeds the gordo megabed overlies dislocated and deformed fan lobe and basin plain deposits the megabed with a thickness of up to 40 m has a sheet like geometry and consists of four superimposed sedimentary units unit i is a matrix supported conglomerate and contains reefal limestone debris metamorphic rocks and mainly at its top large slabs of ripped up fan sediments up to 60 m across the irregular surface of the unit is filled in by unit ii a cobble pebble conglomerate this conglomerate is covered by unit iii a sandstone layer of 6 8 m thickness which grades into unit iv a normal graded to massive mudstone the extra basinal content of the megabed is conservatively estimated at 0 9 km3 its total volume at 6 km3 from sedimentary structures and textures it is inferred that unit i represents a deposit from a debris flow while unit ii consists of a complex mixture of deposits of debris flow and turbulent flow and units iii and iv are deposits from a turbulent flow the megabed is interpreted to originate from a single catastrophic collapse along the basin margin because of its exceptional volume the sheet like geometry and the random position within the fan sequence the megabed is referred to as a seismite the depositional history succeeding a tectonic triggering is envisioned as follows the collapse of the basin border evolved through stages of sliding and slumping into a debris flow body transformation of the debris flow produced turbulent flow it is tentatively assumed that the debris flow outraced its turbidite

high spatial resolution hyperspectral mapping of in stream habitats depths and woody debris in mountain streams this article evaluates the potential of 1 m resolution 128 band hyperspectral imagery for mapping in stream habitats depths and woody debris in third to fifth order streams in the northern yellowstone region maximum likelihood supervised classification using principal component images provided overall classification accuracies for in stream habitats glides riffles pools and eddy drop zones ranging from 69 for third order streams to 86 for fifth order streams this scale dependency of classification accuracy was probably driven by the greater proportion of transitional boundary areas in the smaller streams multiple regressions of measured depths y versus principal component scores x1 x2 xn generated r 2 values ranging from 67 for high gradient riffles to 99 for glides in a fifth order reach r 2 values were lower in third order reaches ranging from 28 for runs and glides to 94 for pools the less accurate depth estimates obtained for smaller streams probably resulted from the relative increase in the number of mixed pixels where a wide range of depths and surface turbulence occurred within a single pixel matched filter mf mapping of woody debris generated overall accuracies of 83 in the fifth order lamar river accuracy figures for the in stream habitat and wood mapping may have been misleadingly low because the fine resolution imagery captured fine scale variations not mapped by field teams which in turn generated false misclassifications when the image and field maps were compared the use of high spatial resolution hyperspectral hsrh imagery for stream mapping is limited by the need for clear water to measure depth by any tree cover obscuring the stream and by the limited availability of airborne hyperspectral sensors nonetheless the high accuracies achieved in northern yellowstone streams indicate that hsrh imagery can be a powerful tool for watershed wide mapping monitoring and modeling of streams d 2003 elsevier science b v all rights reserved

calibrating remotely sensed river bathymetry in the absence of field measurements flow resistance equation based imaging of river depths freebird remote sensing could enable high resolution mapping of long river segments but realizing this potential will require new methods for inferring channel bathymetry from passive optical image data without using field measurements for calibration as an alternative to regression based approaches this study introduces a novel framework for flow resistance equation based imaging of river depths freebird this technique allows for depth retrieval in the absence of field data by linking a linear relation between an image derived quantity x and depth d to basic equations of open channel flow continuity and flow resistance one freebird algorithm takes as input an estimate of the channel aspect width depth ratio a and a series of cross sections extracted from the image and returns the coefficients of the x versus d relation a second algorithm calibrates this relation so as to match a known discharge q as an initial test of freebird these procedures were applied to panchromatic satellite imagery and publicly available aerial photography of a clear flowing gravel bed river accuracy assessment based on independent field surveys indicated that depth retrieval performance was comparable to that achieved by direct field based calibration methods sensitivity analyses suggested that freebird output was not heavily influenced by misspecification of a or q or by selection of other input parameters by eliminating the need for simultaneous field data collection these methods create new possibilities for large scale river monitoring and analysis of channel change subject to the important caveat that the underlying relationship between x and d must be reasonably strong

seismoturbidites a new group of resedimented deposits abstract turbidite beds of exceptionally large volume and areal extent occur in both modern and ancient deep water basins these beds which may reach individual volumes in excess of 100 km3 are apparently the product of catastrophic gravity flows triggered by earthquakes along the margins of highly mobile basins most commonly elongate flysch troughs turbidite beds produced by these catastrophic events are generally characterized by very distinctive geometry internal structures and composition and are termed herein seismoturbidites characteristically these sediments lack time persistent features of deep sea fans such as channels and lobes seismoturbidites may occur as scattered intercalations diluted within otherwise normal turbidite sequences thus forming generally excellent markers for basin wide correlations or as closely spaced repetitive units comprising the bulk of the sedimentary fill of certain flysch basins in both cases they may offer a tremendously useful tool for a better understanding of the distribution of paleoseismic zones in time and space

remote measurement of river discharge using thermal particle image velocimetry piv and various sources of bathymetric information abstract although river discharge is a fundamental hydrologic quantity conventional methods of streamgaging are impractical expensive and potentially dangerous in remote locations this study evaluated the potential for measuring discharge via various forms of remote sensing primarily thermal imaging of flow velocities but also spectrally based depth retrieval from passive optical image data we acquired thermal image time series from bridges spanning five streams in alaska and observed strong agreement between velocities measured in situ and those inferred by particle image velocimetry piv which quantified advection of thermal features by the flow the resulting surface velocities were converted to depth averaged velocities by applying site specific calibrated velocity indices field spectra from three clear flowing streams provided strong relationships between depth and reflectance suggesting that under favorable conditions spectrally based bathymetric mapping could complement thermal piv in a hybrid approach to remote sensing of river discharge this strategy would not be applicable to larger more turbid rivers however a more flexible and efficient alternative might involve inferring depth from thermal data based on relationships between depth and integral length scales of turbulent fluctuations in temperature captured as variations in image brightness we observed moderately strong correlations for a site aggregated data set that reduced station to station variability but encompassed a broad range of depths discharges calculated using thermal piv derived velocities were within 15 of in situ measurements when combined with depths measured directly in the field or estimated from field spectra and within 40 when the depth information also was derived from thermal images the results of this initial proof of concept investigation suggest that remote sensing techniques could facilitate measurement of river discharge

widespread erosion and mass failure from the 51 ma montagnais marine bolide impact off southwestern nova scotia canada12 1this article is one of a series of papers published in this cjes special issue on the theme of mesozoic cenozoic geology of the scotian basin 2earth sciences sector contribution 20120241 the 51 ma montagnais impact crater on the outer scotian shelf is well known but the potential effects from the impact event on the slope and rise seaward of the crater have until now remained poorly understood through detailed seismic stratigraphic correlation and ties to available wells we define a threefold seismic stratigraphic subdivision for upper cretaceous to eocene strata on the shelf and slope calibrated to the most recent biostratigraphic results using this framework we identify a number of depositional and erosional products that are temporally consistent with a late ypresian impact event within the limits of seismic and biostratigraphic resolution we link a series of prominent failure scarps on the outer shelf and upper slope to a single widespread mass transport deposit mtd on the lower continental slope rise and abyssal plain failed material amassed in a large debris field referred to here as the montagnais mtd it covers an area of 93 000 km2 and travelled up to 580 km f

multiple optimal depth predictors analysis modpa for river bathymetry findings from spectroradiometry simulations and satellite imagery abstract remote mapping of bathymetry can play a key role in gaining spatial and temporal insight into fluvial processes ranging from hydraulics and morphodynamics to habitat conditions this research introduces multiple optimal depth predictors analysis modpa which combines previously developed depth predictors along with additional predictors derived from the intensity component of the hsi color space transformation modpa empirically selects a set of optimal predictors among all candidates utilizing partial least squares pls stepwise or principal component pc regression models the primary focus of this study was on shallow

assessing the effect of different bathymetric models on hydraulic simulation of rivers in data sparse regions abstract river bathymetry which is vital for accurate hydraulic modeling is not readily available at large scales because of the logistical difficulties in field surveys and uncertainties associated with remote sensing techniques several studies have explored the potential of conceptual models and interpolation algorithms to estimate bathymetry these models have certain underlying assumptions that limit their accuracy and widespread implementation this study aims to provide insights into the choice of bathymetric model for different hydraulic applications by analyzing the effect of different bathymetric models on hydraulic modeling under different geomorphologic and flow settings this study does not aim to reinforce the importance of bathymetry rather its objective is to identify the bathymetric properties that are critical to accurate estimation of different hydraulic outputs the study accomplishes its objectives by implementing three different bathymetric models with varying cost and efficiency at four sites with diverse bathymetric characteristics five hydraulic outputs namely wetted cross sectional area water surface elevation inundation extents velocity and shear are estimated at three characteristic low and high flows and the results from the four sites are grouped together to perform an unbiased and robust evaluation the performance of these models is evaluated using the best available bathymetric representation generated from detailed field surveys as a benchmark the results indicate that 1d flood modeling is somewhat insensitive to channel shape as long as the estimated shape reflects the channel storage accurately velocity and shear related applications should incorporate bathymetry that represent both the cross sectional area and channel thalweg accurately reaches with low sinuosity

evaluation of an experimental lidar for surveying a shallow braided sand bedded river reaches of a shallow 1 0 m braided sand bedded river were surveyed in 2002 and 2005 with the national aeronautics and space administration s experimental advanced airborne research lidar eaarl and concurrently with conventional survey grade real time kinematic global positioning system technology the laser pulses transmitted by the eaarl instrument and the return backscatter waveforms from exposed sand and submerged sand targets in the river were completely digitized and stored for postflight processing the vertical mapping accuracy of the eaarl was evaluated by comparing the ellipsoidal heights computed from ranging measurements made using an eaarl terrestrial algorithm to nearby 0 5 m apart ground truth ellipsoidal heights after correcting for apparent systematic bias in the surveys the root mean square error of these heights with the terrestrial algorithm in the 2002 survey was 0 11 m for the 26 measurements taken on exposed sand and 0 18 m for the 59 measurements taken on submerged sand in the 2005 survey the root mean square error was 0 18 m for 92 measurements taken on exposed sand and 0 24 m for 434 measurements on submerged sand in submerged areas the waveforms were complicated by reflections from the surface water column entrained turbidity and potentially the riverbed when applied to these waveforms especially in depths greater than 0 4 m the terrestrial algorithm calculated the range above the riverbed a bathymetric algorithm has been developed to approximate the position of the riverbed in these convolved waveforms and preliminary results are encouraging

effects of channel morphology and sensor spatial resolution on image derived depth estimates the utility of remote sensing in the study of fluvial systems depends upon the extent to which image data can be used to derive quantitative information of sufficient accuracy and precision for specific applications in this study we evaluate the effects of channel morphology on depth retrieval by coupling a radiative transfer model to various morphologic scenarios upwelling radiance l u spectra generated for a range of depths 2 150 cm and benthic cover types limestone periphyton and gravel were linearly mixed to simulate subpixel bed topography and substrate heterogeneity for sloping bottoms solar streambed geometry modified l u relative to a level bottom especially for beds sloping steeply away from the sun aggregate pixel scale l u spectra were compared to a database of simulated spectra to determine the radiance equivalent depth of a uniform bottom redub redub spectra for hypothetical stepped streambeds indicated underestimation of the actual area weighted mean depth but the ln l u l 560 l u l 690 redub ratio consistently reproduced the pixel scale mean for beta distributions of depths similarly when both dark periphyton and bright limestone substrates occurred within a pixel redub spectra produced large errors while the ratio proved robust along channel banks pixels will inevitably be mixed and our simulations indicated that although bank fractions estimated by spectral mixture analysis were highly accurate for vegetated cutbanks gravel bars were sensitive to the selection of both aquatic and terrestrial end members and subject to relatively large fraction errors these theoretical results were tested using a ratio based relative depth map and two end member mixture models derived from a hyperspectral image of the lamar river in yellowstone national park which also served to illustrate the importance and applicability of our simulations the primary conclusions of this study are that 1 the ratio based algorithm is well suited to complex river channels 2 channel morphology and sensor spatial resolution must be considered jointly during data collection and analysis and 3 the accuracy and precision of depth estimates are influenced by channel morphology and thus vary spatially

in situ characterization of grain scale fluvial morphology using terrestrial laser scanning the grain scale morphology of fluvial sediments is an important control on the character and dynamics of river systems however current understanding of its role is limited by the difficulties of robustly quantifying field surface morphology terrestrial laser scanning tls offers a new methodology for the rapid acquisition of high resolution and high precision surface elevation data from in situ sediments to date most environmental and fluvial applications of tls have focused on large scale systems capturing macroscale morphologies application of this new technology at scales necessary to characterize the complexity of grain scale fluvial sediments therefore requires a robust assessment of the quality and sources of errors in close range tls data this paper describes both laboratory and field experiments designed to evaluate close range tls for sedimentological applications and to develop protocols for data acquisition in the former controlled experiments comprising high resolution scans of white grey and black planes and a sphere were used to quantify the magnitude and source of three dimensional 3d point errors resulting from a combination of surface geometry reflectivity effects and inherent instrument precision subsequently a methodology for the collection and processing of grain scale tls data is described through an application to a coarse grained gravel system the river feshie d50 32 to 63 mm this stepwise strategy incorporates averaging repeat scans and filtering scan artefact and non surface points using local 3d search algorithms the sensitivity of the results to the filter parameter values are assessed by careful internal validation of digital terrain models dtms created from the resulting point cloud data the transferability of this methodology is assessed through application to a second river bury green brook dominated by finer gravel d50 18 to 33 mm the factor limiting the resolution of dtms created from this second dataset was found to be the relative sizes of the laser footprint and smallest grains copyright 2009 john wiley sons ltd

computer modelling of the water resurge at a marine impact the lockne crater sweden abstract when a cosmic impact occurs at sea the resulting crater can form completely in the water mass or extend into the seafloor at intermediate to great water depths the collapse of the water cavity generates a forceful resurge of water along the seafloor towards the central part of the crater the erosive effects as well as certain conspicuous deposits from resurge flows are known from several craters this study uses numerical modelling to estimate the magnitude of the resurge in the case of the 455 myr old marine target lockne impact crater sweden the water depth at the lockne target site was at least 200 m possibly even as great as 1 km field evidence show that the resurge was strong enough to erode gullies hundreds of metres wide tens of metres deep and kilometres long with computer modelling we studied the behaviour of the flow to get a notion of its magnitude the calculations required simplification of the reality we used a fixed seafloor topography and pure water a rim in the water mass is expected but was neglected in the calculations the simplification likely led to underestimation of the magnitude of the resurge the effect of different target water depths was studied at 200 m target water depth about 1 2 10 11 m 3 of water were needed to fill the lockne crater including the water cavity this took about 2200 s it has been suggested that the main gully formation occurs when the resurge passes the inner rim of the crater that phase lasts for about 700 s with a 500 m target water depth these processes are 3 4 times faster the erosive force of the flow i e unit stream power is 1 9 10 5 wm 2 in the 200 m water depth model this is of the same magnitude as the lake missoula flood the greatest catastrophic flooding known on earth at 500 m target water the unit stream power is a magnitude greater

impact induced mass wasting at the k t boundary blake nose western north atlantic seismic reflection data combined with results from ocean drilling document regional scale slumping associated with the cretaceous tertiary k t impact event the k t boundary is biostratigraphically complete at three ocean drilling program sites 1049 1050 and 1052 located on blake nose 30 n 75 w off eastern florida in water depths of 1300 2600 m maastrichtian chalk is folded and fractured below the k t boundary at all three sites whereas lowermost paleocene clays and chalks are undeformed deformation is pervasive in maastrichtian at the deepest water site site 1049 whereas at the shallower water sites sites 1050 and 1052 thick intervals of structurally intact maastrichtian chalk are separated by thinner intervals of highly deformed sediments correlation of core to seismic reflection data indicates that the k t boundary immediately overlies seismic facies characteristic of mass wasting that extend across most of the 55 km distance of the depth transect maastrichtian sediments appear to have moved as large slump blocks on the upper part of blake nose but deformed more uniformly in the deeper water parts of the transect we suggest that mass wasting occurred on the blake nose 1600 km from the chicxulub crater in response to the cataclysmic seismicity generated by the impact

a geostatistical framework for quantifying the reach scale spatial structure of river morphology 2 application to restored and natural channels abstract alluvial rivers are shaped by interactions between the bed topography the flow field and the movement of sediment to help refine our understanding of these connections between form and process i developed a geostatistical framework for quantifying the reach scale spatial structure of river morphology described in a companion paper in this study i applied this approach to a restored channel and three disparate reaches of a dynamic natural stream repeat topographic surveys of each site were used to examine relationships between channel change and the variability and organization of the topography for the restored river the development of point bars increased overall morphologic diversity primarily because of greater cross sectional asymmetry the three natural reaches experienced a variety of adjustments ranging from 1 gradual bar growth and bank erosion to 2 extensive deposition followed by channel abandonment and 3 chute cutoff and incision of a new channel in both the restored and natural streams geostatistical analysis which involved variogram modeling calculation of integral metrics and inspection of variogram maps provided an effective informative summary of the observed channel changes the use of dimensionless variables accounted for channel size highlighted differences in spatial structure and enabled a comparison among sites the restored reach had not yet achieved the same degree of heterogeneity as the more pristine channels emphasizing variability and spatial pattern via this geostatistical framework could yield insight on form process interactions and help to quantify geomorphic complexity and habitat heterogeneity in the applied context of river restoration

an entropy based method for determining the flow depth distribution in natural channels a methodology for determining the bathymetry of river cross sections during floods by the sampling of surface flow velocity and existing low flow hydraulic data is developed similar to chiu 1988 who proposed an entropy based velocity distribution the flow depth distribution in a cross section of a natural channel is derived by entropy maximization the depth distribution depends on one parameter whose estimate is straightforward and on the maximum flow depth applying to a velocity data set of five river gage sites the method modeled the flow area observed during flow measurements and accurately assessed the corresponding discharge by coupling the flow depth distribution and the entropic relation between mean velocity and maximum velocity the methodology unfolds a new perspective for flow monitoring by remote sensing considering that the two main quantities on which the methodology is based i e surface flow velocity and flow depth might be potentially sensed by new sensors operating aboard an aircraft or satellite