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

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

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

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

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

early middle holocene lake desert evolution in northern ulan buh desert china abstract located in southwestern inner mongolia in northern china the ulan buh desert ubd has evolved significantly during the holocene the northern desert is adjacent to hetao plain an important agriculture area since the han dynasty 200 b c a series of aeolian sand lacustrine sequences from the desert were measured and dated by using differential global positioning system dgps and optically stimulated luminescence osl technologies respectively these lacustrine remains with similar deposit sequences have almost identical elevations and depositional ages indicating that they belonged to a unified paleolake in addition the holocene paleolake desert evolution process in ubd is established aeolian activity prevailed before 8 3 ka and a unified ulan buh paleolake containing the modern jilantai salt lake covered the northern desert during 7 8 7 1 ka ago the paleolake shrank and broke apart after 6 5 ka ago thereafter the paleolake evolved into the modern ubd and jilantai salt lake the study of one sand lacustrine section at the southern edge of hetao plain shows that the tushenze paleolake had a similar evolution process to ulan buh paleolake though they may not be connected to each other as suggested by the elevation difference the ulan buh desert lake evolution was likely due to the climate changes in the monsoon influenced region during the early middle holocene

optical dating of young coastal dunes on a decadal time scale we explore the use of quartz optically stimulated luminescence osl dating for reconstructing coastal evolution on a time scale of decades to a few hundred years samples are taken from the accretionary south west coast of texel a barrier island just offshore of the northern netherlands the ages of dune ridges are known from historical sources an excellent chronology with a decadal accuracy exists for the past 260 years osl ages of less than 10 years on the youngest samples indicate that the osl signal of the quartz grains is very well zeroed prior to deposition and burial osl ages of five samples from a 250 year old dune ridge are indistinguishable and the osl ages on 17 out of 20 samples are in excellent agreement with the well known independent age controls our results highlight the potential of osl dating for high resolution reconstruction of coastal evolution over the past few centuries

till stratigraphy in the st lawrence valley near malone new york revised glacial history and stratigraphic nomenclature compositional parameters are defined for till samples collected from 48 sites in the type areas of the malone and fort covington tills in the st lawrence valley new york till compositional variations are related directly to the influence of the underlying bedrock and are interpreted as facies changes that occur within one extensive till unit the fort covington malone drift boundary as previously mapped is disputed the single till sheet ranges from a gray silty sand carbonate rich facies where underlain by dolostone bedrock in the north to a red sandy carbonate depleted facies where underlain by sandstone and precambrian metamorphic bedrock to the south in contrast to previous studies till fabrics failed to distinguish units and were not useful for correlation surface till in the area is correlated with the upper till exposed in st lawrence seaway excavations the name fort covington till is retained but extended to include surface till in the adirondack highlands the lower till exposed in the seaway does not outcrop in the area and the name malone till should no longer be used the surface till may represent glaciation at least throughout the late wisconsinan extension of ice into the adirondack highlands is suggested by continuity of the till sheet and by ice flow indicators throughout the lowlands major physiographic elements influenced ice movement in that ice was channeled southward through the champlain basin southwesterly parallel to the st lawrence river into the ontario basin and southward into the adirondacks in a lesser flow strength

palynostratigraphy and th u ages of upper pleistocene interglacial and interstadial deposits on cape breton island eastern canada on cape breton island nova scotia near the margin of the wisconsinan ice sheet karst depressions in mississippian gypsum bearing rocks contain interglacial and interstadial organic rich deposits three palynostratigraphic units have been observed and tentatively dated by th u measurements on embedded fossil wood the first dated at ca 125 ka may be assigned to the oceanic sup 18 o substage 5e thermophilous forests quercus ostrya pinus strobus developed in response to a climate warmer than the present the second unit rich in abies balsamea pollen and dated at ca 87 ka may relate to the sup 18 o substage 5a it reflects a cool and wet climate not unlike that of today the third unit probably spans part of the mid wisconsinan sup 18 o stage 3 it shows alternating boreal forest tundra forest assemblages indicative of climatic oscillations during a generally cold interval

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

hyperscale terrain modelling of braided rivers fusing mobile terrestrial laser scanning and optical bathymetric mapping quantifying the morphology of braided rivers is a key task for understanding braided river behaviour in the last decade developments in geomatics technologies and associated data processing methods have transformed the production of precise reach scale topographic datasets nevertheless generating accurate digital elevation models dems remains a demanding task particularly in fluvial systems this paper identifies a threefold set of challenges associated with surveying these dynamic landforms complex relief inundated shallow channels and high rates of sediment transport and terms these challenges the morphological wetted channel and mobility problems respectively in an attempt to confront these issues directly this paper presents a novel survey methodology that combines mobile terrestrial laser scanning and non metric aerial photography with data reduction and surface modelling techniques to render dems from the resulting very high resolution datasets the approach is used to generate and model a precise dense topographic dataset for a 2 5 km reach of the braided rees river new zealand data were acquired rapidly between high flow events and incorporate over 5 x 109 raw survey observations with point densities of 1600 pts m 2 on exposed bar and channel surfaces a detailed error analysis of the resulting sub metre resolution is described to quantify dem quality across the entire surface model this reveals unparalleled low vertical errors for such a large and complex surface model between 0 03 and 0 12 m in exposed and inundated areas of the model respectively copyright 2013 john wiley sons ltd

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

palynologie et paleoenvironnements des episodes du sable de lotbiniere et des varves de deschaillons pleistocene superieur de la vallee du saint laurent lotbiniere sand and deschaillons varves are indicators of the drainage pattern of the st lawrence watershed which presumably occurred during the late sangamonian 5c and 5c 5b transition the pollen content of the lotbiniere sand suggests there was a picea mariana betula pinus boreal forest in the valley in the lowermost zone of the deschaillons varves the pollen is very abundant the boreal forest was progressively flooded by lake deschaillons above this zone the vegetation seems to evolve toward a picea and betula open forest the pollen of the upper contorted varves was presumably reworked from older material or transported from remote sources the following paleoenvironmental sequence is reconstructed in the st lawrence valley i lowering of the relative drainage level as indicated by the erosional disconformity in lower rythmites this phase of unknown duration is ascribed to an eustatic lowering related to a global climatic cooling ii an aggradation phase as indicated by the lo

cat scan in marine stratigraphy a quantitative approach abstract computed axial tomography cat scan gives a pseudo 3d representation of sedimentary cores sediments may be described and numerically processed from digitized high resolution images a 150 m long borehole was drilled and sampled at ile aux coudres middle estuary of the st lawrence quebec and analysed by a tomodensitometer cat scanner this borehole represents mainly the illinoian sangamonian transition series isotopic stage 5e 130 80 kyr b p of a post glacial glacioisostatic marine invasion and the subsequent regressive prodelta four representative samples 900 mm long were chosen for analysis from a transition zone between glacial and prodeltaic sediments they have been described from tomographic longitudinal and transversal sections from ct number series and also from classical analysis such as grain size organic matter and carbonates ct numbers reflect sedimentary characteristics and are closely linked to grain size and to organic matter carbonates are only weakly correlated probably because of its low concentration bed thickness and numerical processing of ct number series are used to characterize lamina and allow for depicting sub annual annual and longer periodicities clay facies fine and thick rhythmites and isolated diamicton beds were identified from bottom to top the first sample contains homogeneous clay rhythmites typical of a distal environment the second is composed of diamictons and thin alternating light dark annual lamina sets in the third sample annual light dark rhythmites are slightly thicker and display subtle semi annual cyclicities in the fourth sample annual rhythmites are several centimetres in thickness and contain preserved sub annual events of possible seasonal cyclicity this succession of facies and associated stratal periodicities may be typical of transgressive sedimentation in a basin such as the st lawrence estuary during the transition from glacial to non glacial conditions

optical dating of dune sands in the northeastern deserts of china abstract optical dating has been used to obtain the ages of fossil stabilized sand dunes from four sections in the northeastern deserts of china our results indicate that the optically stimulated luminescence ages of the four sections correlate well even though the samples were collected from different deserts about 600 km apart our results also indicate that active dune formation in this region lasted from the last glacial maximum to about 10 ka and that the warm climate of the holocene was interrupted by a cold dry dune formation episode about 3 5 1 7 ka the holocene optimum in this region is between 10 and 3 6 ka and a later warm humid dune stabilization phase lasted from at least 1 6 to 1 0 ka the youngest age on the uppermost sand unit yielded an age of only 40 yr supporting the previous argument that the existence of modern active eolian sands in the regions with a mean annual precipitation of up to 450 mm is not mainly due to drought but to extensive land cultivation over historic time from the luminescence properties of the quartz grains it is hypothesized that the sands in most of the sections are probably derived from more than one source with a minor source of quartz having a different thermal history before deposition

summer monsoon precipitation variations in central china over the past 750 years derived from a high resolution absolute dated stalagmite abstract a 2 3 year resolution record of stalagmite oxygen isotope variations from the south flank of the qinling mountains central china has revealed the asian summer monsoon asm precipitation variations in the investigated area over the past 750 years the summer monsoon precipitation gradually increased since 1249 ad reaching its highest values in the period 1535 1685 ad and then decreased with substantial decadal to centennial scale fluctuations the monsoon precipitation increased again between 1920 and 1970 ad three intervals of high monsoon precipitation were identified 1535 1685 ad 1755 1835 ad and 1920 1970 ad three intervals of low precipitation were inferred in 1249 1325 ad 1390 1420 ad and 1890 1915 ad the 18 o composition and lithological features of the stalagmite coincidently indicate a wetter climate during the little ice age lia which is also confirmed by climate records from chinese historical documents within this area a comparison with other high resolution speleothem records indicates regional differences in monsoon precipitation variability from the south to the north of central china in the last 750 years on decadal to centennial scale power spectrum analysis of the 18 o record shows significant 117 8 34 6 14 10 3 and 6 year periodicities these periodicities are widely observed in the climate records from asm controlled areas of china and are consistent with the gleissburg periodicity br ckner periodicity sunspot periodicity of solar activity and el nino southern oscillation enso periodicity these correlations suggest that both solar activity and enso periodicity may have had important influences on asm precipitation in china over the past 750 years

on the use of srtm and altimetry data for flood modeling in data sparse regions the growing availability of remotely sensed data has fostered the implementation of hydraulic modeling in poorly gauged regions however these applications suffer the lack of knowledge of river bathymetry which cannot be directly inferred from satellite instruments this study explores the possibility to set up calibrate and validate a hydrodynamic model which geometry is based on global and freely available satellite data first the study tests two different procedures for inferring the river bathymetry under the water surface level second focusing on a po river stretch of 140 km northern italy the study further assesses the suitability of spaceborne topographic and remotely sensed altimetry data i e ers 2 and envisat for implementing and calibrating hydrodynamic models referring to 90 m srtm shuttle radar topography mission digital elevation model for the representation of the riverbed morphology the work analyzes the performances of different 1 d numerical models which cross sections are modified according to two approaches 1 channel bankfull depth cb and 2 slope break sb approach the calibration and validation processes are performed by referring to extended altimetry time series 16 years of data while the accuracy and trustworthiness of 1 d models are tested with reference to a quasi 2 d model based on detailed geometry data results show that both cb and sb approaches enhance the performance of srtm based models in particular the sb approach is completely based on satelliteborne data and shows nash sutcliffe efficiency mae and rmse values similar to those obtained with the benchmark model

chronologie th u des concretions calcaires des varves du lac glaciaire de deschaillons wisconsinien inferieur late pleistocene lake deschaillons varves from the central st lawrence lowlands represent a lithostratigraphic unit whose upper limit is defined by the overlying gentilly till which was laid down

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

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

comment on flow resistance equations without explicit estimation of the resistance coefficient for coarse grained rivers by raul lopez javier barragan and m angels colomer

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

pleistocene palynostratigraphy in the st lawrence valley and middle estuary the litho biostratigraphic framework of the upper middle and upper quaternary units of the st lawrence basin results from the interplay of ice advance retreat isostatic depression rebound fluvial processes and climatic changes each main climatic cycle is characterized by a sedimentary sequence representative of the associated changing depositional environments the climatic significance of the units is assessed with reference to the pollen content and the evolving trend of the inferred vegetation five assemblages are defined 1 the mixed woods assemblage related to temperate deciduous forests 2 the boreal forest subdivided into a balsam fir a balsamea dominated assemblage a pine p banksiana or p divaricata dominated assemblage and a spruce dominated assemblage picea mariana 3 the forest tundra subarctic zone 4 the shrub tundra with subarctic plants and 5 the herb tundra arctic zone three marine invasions older than late wisconsinan record a progressive vegetal recolonization a pre illinoian marine episode the post illinoian marine invasion of guettard sea 6 5 transition and the cartier sea invasion substage 5b three types of lake inundated the lowlands 1 lake systems associated with interstadial or interglacial fluvial drainage 2 deglacial lakes with a gradual vegetal recolonization 3 pre glacial lakes whose pollen indicates boreal forest replacement by forest tundra and herb tundra

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

optically stimulated luminescence dating of young sediments a review optically stimulated luminescence osl dating of young 1000 years sediments is used increasingly in a wide variety of late holocene studies as a mean of establishing contemporary sedimentation rates or the timing of sediment deposition this paper provides a summary of the basic principles of osl dating outlines the problems specific to the dating of young material and then uses recent applications to young sediments to illustrate the greatly increased scope and potential of the method in geomorphology and the geology of recent deposits the overall reliability of this new generation of osl ages is examined by comparing where possible osl ages with independent age control it is concluded that the osl ages are accurate in that there is no evidence for systematic over or under estimation it is our conclusion that osl dating should be regarded as a reliable chronological tool for determining the time of deposition of water lain sediments from the coastal zone and aeolian deposits from both coastal and inland environments our conclusion is supported by the growing popularity of osl dating in geomorphology and geology

controls of channel morphology and sediment concentration on flow resistance in a large sand bed river a case study of the lower yellow river abstract accurate estimation of flow resistance is crucial for flood routing flow discharge and velocity estimation and engineering design various empirical and semiempirical flow resistance models have been developed during the past century however a universal flow resistance model for varying types of rivers has remained difficult to be achieved to date in this study hydrometric data sets from six stations in the lower yellow river during 1958 1959 are used to calibrate three empirical flow resistance models eqs 5 7 and evaluate their predictability a group of statistical measures have been used to evaluate the goodness of fit of these models including root mean square error rmse coefficient of determination cd the nash coefficient na mean relative error mre mean symmetry error mse percentage of data with a relative error 50 and 25 p 50 p 25 and percentage of data with overestimated error poe three model selection criterions are also employed to assess the model predictability akaike information criterion aic bayesian information criterion bic and a modified model selection criterion msc the results show that mean flow depth d and water surface slope s can only explain a small proportion of variance in flow resistance when channel width w and suspended sediment concentration ssc are involved the new model 7 achieves a better performance than the previous ones the mre of model 7 is generally

combining geomorphometry feature extraction techniques and earth surface processes research the way forward abstract in recent years the wealth of technological development revolutionised our ability to collect data in geosciences due to the unprecedented level of detail of these datasets geomorphologists are facing new challenges giving more in depth answers to a broad er range of fundamental questions across the full spectrum of the earth s and planetary processes this contribution builds on the existing literature of geomorphometry the science of quantitative land surface analysis and feature extraction translate land surface parameters into extents of geomorphological elements it provides evidence of critical themes as well as emerging fields of future research in the digital realm supporting the likely effectiveness of geomorphometry and feature extractions as they are advancing the theoretical empirical and applied dimension of geomorphology the review further discusses the role of geomorphometric legacies and scientific reproducibility and how they can be implemented in the hope that this will facilitate action towards improving the transparency and efficiency of scientific research and accelerate discoveries in geomorphology in the current landscape substantial changes in landforms ecosystems land use hydrological routing and direct anthropogenic modifications impact systems across the full spectrum of geomorphological processes although uncertainties in the precise nature and likelihood of changes exist geomorphometry and feature extraction can aid exploring process regimes and landscape responses taken together they can revolutionise geomorphology by opening the doors to improved investigations crossing space and time scales blurring the boundaries between traditional approaches and computer modelling and facilitating cross disciplinary research ultimately the exploitation of the available wealth of digital information can help to translate our understanding of geomorphic processes which is often based on observations of past or current conditions into the rapidly changing future

the last interglacial glacial group of sediments in the st lawrence valley quebec canada abstract during the last interglacial glacial sangamonian wisconsinian cycle the st lawrence valley was invaded by allochthonous ice flowing from the nouveau quebec labrador ice dome the valley was inundated by lakes during the englaciation phases and by post glacial lakes and glacio isostatic seas during at least two deglaciation episodes during the climatic optimum of the last interglacial stage isotopic substage 5e and during at least two interstades a fluvial system was inset into the previous units the base level of the drainage was related to contemporaneous mean sea level and glacio isostatic state of equilibrium according to published and original data the quaternary group of sediments of the valley can be divided into five parts 1 illinoian glacial deposits 2 fluvial deposits of the climatic optimum of the sangamonian 3 a set of intermediate sedimentary sequences which may comprise fluvial glaciolacustrine glacial and marine deposits 4 the upper main sequence and 5 holocene fluvial and lacustrine deposits the age and correlation of the intermediate sequences are debated they indicate at least one glacial event during isotopic stage 5b or 4 the upper sequence is a complete succession of fluvial glacial and post glacial marine facies les becquets interstade and trois rivieres stade according to contradictory 14 c and tl dates the valley was covered by ice after 75 ka stage 4 or after 61 ka during stage 3 until about 11 ka

optically stimulated luminescence dating of sand dune formed within the little ice age abstract optically stimulated luminescence osl dating has been intensively used to date the late quaternary deposits the single aliquot regenerative dose sar protocol was applied to measure coarse quartz grains extracted from dali sand dunes central china it was found that this popular method could not accurately date sand dunes activities that recently happened this is due to the low osl sensitivity of quartz grains leading to a failure in osl dating that has also been met in other sediments before to overcome this limitation quartz grains were heated to 500 c to increase the osl output for one magnitude sensitivity changes could also be corrected by the following test dose osl responses and has no influence on osl ages thus it is suggested to carry out the sar protocol for dim and young quartz osl samples with additional annealing step e g 500 c after the measurements of natural cycle the resultant osl ages proved that the last sand dune activities happened during the little ice age 400 years ago which was further supported by independent age control 1600 ad from historical documents