towards a protocol for laser scanning in fluvial geomorphology advances in spatial analytical software allow digital elevation models dems to be produced which accurately represent landform surface variability and offer an important opportunity to measure and monitor morphological change and sediment transfer across a variety of spatial scales many of the techniques presently employed aerial lidar edm theodolites gps photogrammetry suffer coverage or resolution limitations resulting in a trade off between spatial coverage and morphologic detail captured this issue is particularly important when rates of spatial and temporal change are considered for fluvial systems this paper describes the field and processing techniques required for oblique laser scanning to acquire 0 01 m resolution digital elevation data of an upland reach of the river wharfe in the uk the study site is variable with rapidly changing morphology diverse vegetation and the presence of water and these are evaluated with respect to laser data accuracy scan location frequency and distance are discussed with reference to survey accuracy and efficiency and a field protocol is proposed scan data cloud merging was achieved with a high degree of precision sub centimetre and positional data are shown to be very accurate for exposed surfaces vegetation and water decrease the accuracy as the laser pulse is often prevented from reaching the ground surface or is not returned copyright 2006 john wiley sons ltd

flow fields bed shear stresses and suspended bed sediment dynamics in bifurcations of a large river 1 channel bifurcations associated with bars and islands are important nodes in braided rivers and may control flow partitioning and thus affect downstream confluences as well as the formation and dynamics of bars however the morphodynamic processes associated with bar formation are poorly understood and previous studies have largely concerned laboratory experiments small natural streams or numerical analyses with large froude numbers high slopes and low shields stresses in these cases the morphologic changes at bifurcations are relatively rapid with predominant bed load transport and the suspended load playing a minor role in this paper the evolution of the flow structure and suspended bed sediment transport along four expansion diffluence units in the rio parana argentina are described the rio parana is a large multichannel river with a bed composed of medium and fine sands and possesses low froude numbers and high suspended bed material transport primary and secondary flow velocity components were measured with an acoustic doppler current profiler adcp along the expansion diffluence units and the backscatter signal of the adcp was calibrated to allow simultaneous measurements of suspended bed sediment concentrations the interactions between these variables show that the cores of primary flow velocity and suspended bed sediment concentration do not necessarily follow the thalweg at the bifurcation and that inertial effects on the suspended bed sediment may influence the morphodynamics of bar formation it is suggested that changes in flow stage as well as the presence of vegetation may further increase the deposition of suspended bed sediment at the bar head this study suggests that the ratio of suspended bed material to bed load is an important factor controlling the morphodynamics of bifurcations in large sand bed braided rivers

deconvolution technique to separate signal from noise in gravel bedload velocity data a deconvolution procedure is presented to estimate the probability density function of bedload transport velocity from noisy stationary data collected using the bottom tracking feature of acoustic doppler current profilers adcps the procedure involves the optimization of a computational summation of random variables for the instrument noise assumed to be gaussian with zero mean and the spatially averaged bedload velocity within the insonified area of each acoustic beam v the procedure was tested on two adcp time series measured in two different gravel bed rivers fraser river and norrish creek models generated using either a semitheoretical compound poisson gamma distribution or an empirical gamma distribution for v were similar and did not differ significantly from the distribution of the original data optimized distributions for v were highly positively skewed the instrument noise was comparable to instrument noise for adcp water velocity measurements i e an order of magnitude greater t

experimental study of the transport of mixed sand and gravel we measured a wide range of transport rates for five different sand gravel mixtures in a laboratory flume each mixture used the same gravel and sand was added to produce mixtures containing 6 15 21 27 and 34 sand control of other variables allows us to isolate the effect of bed sand content on transport as sand content increases gravel transport rates increase by orders of magnitude even though the proportion of gravel in the bed decreases the increase in gravel transport rate is most rapid over the range of bed sand content between 15 and 27 the increase in transport rate is larger than predicted using standard scaling relations between transport rate and grain size indicating that models of transport and sorting and predictions of stream channel response to sand inputs need to be revised to account for the influence of sand content bed surface grain size was measured at the end of each run surface grain size varied with sand content but showed little or no coarsening with flow strength and transport rate this casts doubt on the idea that armor layers form at small flows and weaken or vanish with increasing flow and transport rate

buffers barriers and blankets the dis connectivity of catchment scale sediment cascades abstract catchment configuration and the nature of connectivity within and between landscape compartments affect the operation of sediment cascades and geomorphic responses to disturbance events of differing magnitude and frequency this paper introduces the concept of landform impediments termed buffers barriers and blankets that impede sediment conveyance by limiting the connectivity between landscape compartments buffers restrict sediment delivery to channels barriers inhibit sediment movement along channels and blankets drape channel or floodplain surfaces affecting the accessibility of sediment to entrainment these features operate as a series of switches which turn on off processes of sediment delivery determining the effective catchment area at any given time using previously documented examples the role of these features in affecting the operation of sediment cascades in a low relief passive landscape setting such as the australian landmass is contrasted to examples from high relief uplifting settings in new zealand the australian examples are further explored by examining how changes to landscape connectivity brought about by human disturbance since european settlement have impacted upon landscape sensitivity and prospects for river recovery this approach to analysis of impediments to sediment conveyance is generic and can be applied in any environmental setting

case study of precision of gps differential correction strategies influence on adcp velocity and discharge estimates the precision of four differential global positioning systems dgps was evaluated in the context of fluvial water velocity and discharge measurement dgps is used to resolve water velocities measured with an acoustic doppler current profiler adcp into earth coordinates if bottom tracking is unavailable the dgps systems assessed were 1 the dual frequency real time kinematic rtkl1l2 2 the single frequency real time kinematic rtkl1 3 the code phase canadian coast guard cg and 4 the code phase wide area augmentation system waas repeat discharge surveys n 22 were conducted at a transect of the gatineau river canada simultaneously collecting bottom track boat velocity vbt and boat velocity from all four dgps vdgps the mean absolute single ping differences between vbt and vdgps were 3 1 rtkl1l2 3 2 rtkl1 8 9 cg and 9 8 cm s waas errors were observed more often near channel margins presumably due to obstruction and multipath associated with riverbank vegetation

hydraulic validation of two dimensional simulations of braided river flow with spatially continuous adcp data 1 gravel bed braided rivers are characterized by shallow branching flow across low relief complex and mobile bed topography these conditions present a major challenge for the application of higher dimensional hydraulic models the predictions of which are nevertheless vital to inform flood risk and ecosystem management this paper demonstrates how high resolution topographic survey and hydraulic monitoring at a density commensurate with model discretization can be used to advance hydrodynamic simulations in braided rivers specifically we detail applications of the shallow water model delft3d to the rees river new zealand at two nested scales a 300 m braid bar unit and a 2 5 km reach in each case terrestrial laser scanning was used to parameterize the topographic boundary condition at hitherto unprecedented resolution and accuracy dense observations of depth and velocity acquired from a mobile acoustic doppler current profiler adcp along with low altitude aerial photography were then used to create a data rich framework for model calibration and testing at a range of discharges calibration focused on the estimation of spatially uniform roughness and horizontal eddy viscosity h through comparison of predictions with distributed hydraulic data results revealed strong sensitivity to h which influenced cross channel velocity and localization of high shear zones the high resolution bed topography partially accounts for form resistance and the recovered roughness was found to scale by 1 2 1 4 d84 grain diameter model performance was good for a range of flows with minimal bias and tight error distributions suggesting that acceptable predictions can be achieved with spatially uniform roughness and h

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

morphology and flow fields of three dimensional dunes rio parana argentina results from simultaneous multibeam echo sounding and acoustic doppler current profiling 1 most past studies of river dune dynamics have concentrated on two dimensional 2 d bed forms with constant heights and straight crest lines transverse to the flow and their associated turbulent flow structure this morphological simplification imposes inherent limitations on the interpretation and understanding of dune form and flow dynamics in natural channels where dune form is predominantly three dimensional for example studies over 2 d forms neglect the significant influence that lateral flows and secondary circulation may have on the flow structure and thus dune morphology this paper details a field study of a swath of 3 d dunes in the rio parana argentina a large 0 35 km wide 1 2 km long area of dunes was surveyed using a multibeam echo sounder mbes that provided high resolution 3 d detail of the river bed simultaneous with the mbes survey 3 d flow information was obtained with an acoustic doppler current profiler adcp revealing a complicated pattern of dune morphology and associated flow structure within the swath dune three dimensionality appears intimately connected to the morphology of the upstream dune with changes in crest line curvature and crest line bifurcations junctions significantly influencing the downstream dune form dunes with lobe or saddle shaped crest lines were found to have larger more structured regions of vertical velocity with smaller separation zones than more 2 d straight crested dunes these results represent the first integrated study of 3 d dune form and mean flow structure from the field and show several similarities to recent laboratory models of flow over 3 d dunes

sediment transport from continuous monitoring in a perennial mediterranean stream vericat d batalla r j 2010 sediment transport from continuous monitoring in a perennial mediterranean stream catena 82 2 77 86 sponsorship research project sediment export from large semi arid catchments measurements and modelling sesam funded by the deutsche forschungsgemeinschaft dgf

the relationship between particle travel distance and channel morphology results from physical models of braided rivers channel form and sediment transport are closely linked in alluvial rivers and as such the development of a conceptual framework for the downstream controls on particle mobility and likely deposition sites has immense value in terms of the way we understand and predictively model rivers despite the development of conceptual models which frame flood scale particle transport distance termed path length as a function of channel bar locations an understanding of the controls on such path lengths in braided rivers remains especially elusive in large part due to the difficulty in explicitly linking morphology and particle transport distances in the field here we utilize a series of laboratory flume experiments to link path length distances with channel morphology our morphologic characterization is based on ultrahigh resolution digital elevation models and bar classifications derived from structure from motion topography while we simultaneously capture particle path lengths using fluorescent tracer particles over the course of five physical model simulations our findings underscore the importance of channel bars in acting as deposition sites for particles in transport 81 of recovered tracers were found in association with compound point lateral or diagonal bars bar heads 29 and bar margins 41 were the most common bar related deposition surfaces for recovered tracers peaks in particle deposition frequency corresponding to channel bars were often noted on path length distributions from tracer data most tracers were deposited in areas that had experienced shallow z 0 002 m deposition average path length distance 2 5 m was closely related to average confluence diffluence spacing 2 3 m across all runs the transferability of this understanding to braided streams has important implications for the development of simplified morphodynamic models which seek to predict braided channel evolution across multiflood timescales

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

morphodynamic signatures of braiding mechanisms as expressed through change in sediment storage in a gravel bed river previous flume based research on braided channels has revealed four classic mechanisms that produce braiding central bar development chute cutoff lobe dissection and transverse bar conversion the importance of these braiding mechanisms relative to other morphodynamic mechanisms in shaping braided rivers has not yet been investigated in the field here we exploit repeat topographic surveys of the braided river feshie uk to explore the morphodynamic signatures of different mechanisms of change in sediment storage our results indicate that when combined the four classic braiding mechanisms do indeed account for the majority of volumetric change in storage in the study reach 61 total chute cutoff traditionally thought of as an erosional braiding mechanism appears to be the most common braiding mechanism in the study river but was more the result of deposition during the construction of diagonal bars than it was the erosion of the chute three of the four classic mechanisms appeared to be largely net aggradational in nature whereas secondary mechanisms including bank erosion channel incision and bar sculpting were primarily net erosional although the role of readily erodible banks in facilitating braiding is often conceptualized we show that bank erosion is as or more important a mechanism in changes in sediment storage than most of the braiding mechanisms and is the most important secondary mechanism 17 of total change the results of this study provide one of the first field tests of the relative importance of braiding mechanisms observed in flume settings

how do gravel bed rivers braid sedimentary processes and bed forms leading to the onset of braiding were observed in small scale hydraulic models of gravel bed streams the laboratory streams had a variety of combinations of constant discharge and slope but identical bed material particle size distributions from initially straight channels braiding occurred by four different processes deposition and accumulation of a central bar chute cutoff of point bars conversion of single transverse unit bars to mid channel braid bars and dissection of multiple bars in these experiments the chute cutoff mechanism was the most common but the predominant braiding mechanism depends upon sediment mobility excess bed shear stress and the bed form regime at very low excess bed shear stress the central bar process dominates but at higher excess bed shear stress slip face unit bars are more common bed scour at confluences is more pronounced and propogation of alternate convergence scour and divergence deposition is more likely thus chu

analysis of the effect of changing discharge on channel morphology and instream uses in a braided river ohau river new zealand constant discharges of 26 5 56 7 105 240 and 507 m3s 1 were released down the ohau river from ohau a power station and measurements of water depths and mean velocities made along cross sections in a braided section of the channel frequency distributions of water depth and velocity are presented both singly and jointly for each discharge the methods used provide much more information on the changing character of the river than is provided by conventional hydraulic geometry relations as discharge increases existing channels become wider deeper and faster and frequently merge to become a single larger channel however additional channels are generated with the same characteristics as those existing at lower discharges and the total number of channels at a cross section remains constant hence the increase of water surface area tends to be by addition of faster deeper water to a constant area of shallow slow water whose location in the river bed changes this process has the major implication for instream uses such as salmonid spawning in that the area suitable for these uses may remain constant over a wide range of flows in some respects then the braided river is morphologically more stable than a single thread river

active width of gravel bed braided rivers previous analyses have identified the active width of braided rivers the bed area over which bed load flux and short term morphological change occurs as an important element of braiding dynamics and predictions of bed load flux here we compare theoretical predictions of active width in gravel bed braided rivers with observations from sunwapta river and from a generic physical model of gravel braided rivers to provide general observations of the variation in active width and to develop an understanding of the causes of variation bed topography was surveyed daily along a 150 m reach of the pro glacial sunwapta river for a total of four weeks during summer when flow was above threshold for morphological activity in the laboratory detailed digital elevation models dems were derived from photogrammetric survey at regular intervals during a constant discharge run from the field and flume observations there is considerable local and circumstantial variation in active width but also a general trend in average active width with increasing discharge there is also a clear relationship of active width with active braiding index number of active branches in the braided channel network and with dimensionless stream power which appears to be consistent across the range of data from field and physical models thus there is a link between active width and the river morphology and dynamics and the possibility of a general relationship for estimating active width from channel pattern properties or reach scale stream power values from which approximate bedload flux calculations may be made the analysis also raises questions about differences between hydraulically based numerical model computations of instantaneous active width and observation of time integrated morphological active width understanding these differences can give insight into the nature of bedload transport in braided rivers and the relationship to morphological processes of braiding copyright 2011 john wiley sons ltd

gravel transport in the braided waimakariri river mechanisms measurements and predictions abstract yields of grabel bed load in the braided lower waimakariri river in new zealand are investigated by several methods and for different timescales short term several months medium term several years and long term 1967 1983 short term estimates of gravel yield were made for five such periods in 1986 1987 by a morphological method bed morphology in a selected reach was mapped before and after flood events the gross volume of scour in that time period measured and a mean transport rate through the reach computed on the basis of the step distance of gravel movement from scour zones to areas of accretion the findings indicate that a considerable fraction of the annual gravel load is derived from scour of braid banks with the gravel being shunted downstream from one zone of temporary storage to another computation of bed load yields during the same period by the meyer peter and muller mpm equation revealed excellent agreement with the morphological estimate comparison of the mpm prediction based on flow duration data for 1967 1983 also showed excellent agreement with the long term rate assessed by stadia survey of cross sections in the reach of accumulation downstream of the study reach predictions using the mpm formula for the medium term however while acceptable showed greater differences from the surveyed rates evidence indicates that this is related to highly dynamic bed conditions in which the availability of more mobile finer grained gravel in the reach changes from year to year as slugs of such sediment move intermittently downstream thus while prediction of a short term yield based on bed conditions at the time of study and a long term yield based on temporal mean conditions as inferred from bed conditions averaged along the river are realistic goals the accurate prediction of successive short term or medium term yields seems to be impossible unless detailed analysis of bed conditions especially grain size is undertaken in each time period a major task

numerical simulation of relatively wide shallow channels with erodible banks a two dimensional numerical model was developed to simulate relatively wide shallow rivers with an erodible bed and banks composed of well sorted sandy materials a moving boundary fitted coordinate system was used to calculate water flow bed change and bank erosion the cubic interpolated pseudoparticle method was used to calculate flow which introduced little numerical diffusion the sediment transport equation for the streamline and transverse transport was used to estimate bed and bank evolution over time while considering the secondary flow bank erosion was simulated when the gradient in the cross sectional direction of the banks was steeper than the submerged angle of repose because of bed erosion near the banks the numerical model reproduced the features of central bars well such as bar growth channel widening due to divergence of the flow around the bars scour holes at the lee of the bars and the increase of bar size with time these features were in accordance with the observations for laboratory experiments it also reproduced the features of braided rivers such as the generation of new channels and abandonment of old channels the bifurcation and confluence of channels and the lateral migration of the channels the model showed that the sediment discharge rate fluctuated with time one of the dynamic features observed in braided channels

channel morphology and bedload pulses in braided rivers a laboratory study bedload pulses in gravel bed rivers have been widely reported in recent years and attempts have been made to relate them to channel morphology bedload transport and channel morphology were measured in a small scale generic model of braided gravel bed streams two experiments are described in which braided channels developed in a 14 m 3 m sand tray total bedload output from the tray was weighed every 15 minutes stream bed geometry was surveyed every four hours pulses were observed in the bedload output time series and were qualitatively related to the channel morphology immediately upstream of the measuring section the bagnold 1980 bedload equation generally overpredicts measured bedload transport rates when applied to channels that were in equilibrium or aggrading underprediction occurred when applied to degrading channels aggradation was associated with channel multiplication and bar deposition channel pattern simplification occurred when degradation took place and bars emerged from the water flow development of phases of aggradation and degradation is dependent upon the three dimensional geometry of the stream beds spatial and temporal feedback loops can be identified enabling links between channel morphology and bedload transport rate to be directly identified

new 3 d flow interpolation method on moving adcp data 1 a simple but accurate interpolation procedure for obtaining the three dimensional distribution of three component velocity data from moving acoustic doppler current profiler adcp observation data is proposed for understanding actual flow structure within a river with complex bathymetry the three dimensional mean velocity field provides a basic picture of the flow for obtaining the three dimensional distribution of three component velocity data in this work anisotropic gridding was introduced in order to remove the random component of measured velocity data caused by the turbulence of the flow and measurement error a continuity correction based on the pressure equation was used to reduce both random and systematic errors the accuracy of the developed method was evaluated using three dimensional flow simulation data from a detached eddy simulation des by using the procedure developed the complex flow structure surrounding the spur dikes section in the uji river was successfully visualized and explored the proposed method shows superiorities in both accuracy and consistency for the interpolated velocity field as compared to the kriging and inverse distance weighted idw methods

methodological sensitivity of morphometric estimates of coarse fluvial sediment transport abstract the estimation of fluvial sediment transport rate from measurements of morphological change has received growing recent interest the revival of the morphological method reflects continuing concern over traditional methods of rate determination but also the availability of new survey methods capable of high precision high resolution topographic monitoring remote sensing of river channels through aerial digital photogrammetry is a potentially attractive alternative to labour intensive ground surveys however while photogrammetry presents the opportunity to acquire survey data over large areas data precision and accuracy particularly in the vertical dimension are lower than in traditional ground survey methods this paper presents results of recent research in which digital elevation models dems have been developed for a reach of a large braided gravel bed river in scotland using both digital photogrammetry and high resolution rtk gps ground surveys a statistical level of change detection is assessed by comparing surfaces with independent check points the methodological sensitivity of the annual channel sediment budget 1999 2000 to the threshold is presented results suggest that while the remote survey methods employed here can be used to develop qualitatively convincing moderate precision dems of channel topography rmse 0 21 m the remaining errors imply significant limits on reliable change detection which lead to important information losses tests at a 95 confidence interval for change detection show that over 60 of channel deposition and 40 of erosion may be obscured by the lower level of precision associated with photogrammetric monitoring when compared to ground survey measurements this bias reflects the difficulty of detecting the topographic signature of widespread but shallow deposition on bar tops

step by step error assessment in braided river sediment budget using airborne lidar data abstract sequential airborne lidar surveys were used to reconstruct the sediment budget of a 7 km long braided river channel in southeastern france following a 14 year return period flood and to improve its accuracy step by step data processing involved i surface matching of the sequential point clouds ii spatially distributed propagation of uncertainty based on surface conditions of the channel and iii water depth subtraction from the digital elevation models based on water depths measured in the field the respective influence of each processing step on sediment budget computation was systematically documented this showed that surface matching and water depth subtraction both have a considerable effect on the net sediment budget although dem of difference thresholding based on uncertainty analysis on absolute elevation values had a smaller effect on the sediment budget this step is crucial for the production of a comprehensive map of channel deformations a large independent data set of rtk gps checkpoints was used to control the quality of the lidar altimetry the results showed that high density 7 9 points m 2 airborne lidar surveys can provide a very high level of detection of elevation changes on the exposed surfaces of the channel with a 95 confidence interval level of detection between 19 and 30 cm change detection from lidar data revealed that 54 of the pre flood active channel was reworked by the flood the braided channel pattern was highly disturbed by the flood owing to the occurrence of several channel avulsions

the zhayao tectonic window of the jurassic yuantai thrust system in liaodong peninsula ne china geometry kinematics and tectonic implications abstract liaodong peninsula on the northeastern north china block that witnessed the spectacular late mesozoic tectonics is a key area to probe the transition from compression to extension borehole data clearly reveals that the cambrian limestone overlay the jurassic limestone which identified the yuantai thrust system in liaodong peninsula zircon grains from a granodiorite dike that intruded the thrust system yielded u pb age of 128 3 1 3 ma further constraining the timing of the thrusting between late jurassic to early early cretaceous a detailed field study of three dimensional fault zone exposures in the zhayao tectonic window are conducted to decipher the thrust tectonics before the extension in liaodong peninsula the key observations are 1 meter scale asymmetric folds in deformed mid cambrian rocks 2 decameter scale recumbent folds and secondary imbricate thrusts in deformed middle jurassic rocks and 3 non foliated breccia fault gouge and brittle porphyroclasts adjacent to fault planes the combined brittle ductile style of deformation indicates that the fault zone operated under near surface conditions in addition we infer that the folds were formed first at the propagating fault tip and subsequently dismembered by normal faults we interpret the zhayao thrust which is located around the margin of the tectonic window as the frontal thrust of the yuantai thrust system furthermore by applying the theory of fault related folds we deduce that the zhayao frontal thrust is a secondary duplex based on our field observations and borehole data we propose an imbricate thrust model for the fold and thrust belt of the southern liaodong peninsula the structural data indicate that the transport direction of the yuantai thrust system was top to the southeast suggesting that the thrust system was resulted due to northwest ward subduction of the paleo pacific plate during the mesozoic

flow field and morphology mapping using adcp and multibeam techniques survey in the po river an 8 km long and 250 m wide reach of the po river italy was surveyed with two vessels aiming to investigate the channel morphology and flow field characterizing this major italian river and to provide data for the calibration of a numerical model the first vessel was equipped with a multibeam ecosounder mbes whereas an acoustic doppler current profiler adcp was located on the second one fixed vessel adcp measurements were used to preliminarily investigate the turbulence variability affecting the reliability of moving vessel measurements to evaluate the friction velocity by using moving vessel measurements the vertical variance of velocity profiles as an alternative to logarithmic fitting of adcp profiles was estimated an average of 30 m cells of depth averaged velocity friction velocity and surface bottom velocity angle are presented in maps as the most relevant flow field features the flow field and channel morphology at bed form or channel scales showed noticeable correlations 0 9 in

assessment of morphological changes induced by flow and flood pulses in a gravel bed braided river the tagliamento river italy large gravel bed braided rivers show a highly dynamic evolution where even moderate flow pulses can produce significant morphological adjustment an estimation of network variations is needed by river authorities as well as by ecologists for better managing river ecosystems however few field investigations have been performed to measure the effect of unsteady discharges in braided rivers in this paper we report on the morphological changes induced by six different floods in a 1 km long reach of the tagliamento river italy topographic surveys were performed after each significant flood and an automatic digital camera continuously monitored the planimetric configuration repeated measurements of cross section profiles allowed the quantification of the transported sediments volume and in particular provided a basis to estimate the percentage of the floodplain subject to morphological evolution data analysis showed a good relationship between peak flow level active width and mean bed level changes similarly lateral channel shifting is likely to increase for larger floods monitoring of a range of discharges up to bankfull conditions revealed a fundamental difference between flow pulses events on the average occurring one or more times per year and flood pulses with a return period larger than two years the morphological evolution in the former case is mainly limited to a few active branches and is locally driven by bank erosion at the bend apex on the other hand larger floods induce a complete reworking of the network configuration where bifurcations and confluences play a crucial role single morphological units like branches nodes bars are no longer recognizable after this type of event braided rivers are therefore characterized by the occurrence of two different spatial and temporal scales that force the ecosystem dynamics

bed load bias comparison of measurements obtained using two 76 and 152 mm helley smith samplers in a gravel bed river 1 we assess how the size of the helley smith hs bed load sampler nozzle affects the accuracy of bed load sampling semitheoretical considerations show that the larger grains resident on the streambed can influence the sample either by blocking the sampler entrance or by causing the sampler to rest in a perched position probabilities for interference can be derived from the distribution of grain sizes but they do not capture the actual complexity of the influence of the bed on sampler performance we therefore make an empirical comparison of sediment trapped by hs samplers with 76 and 152 mm intakes during floods in the gravel bed lower ebro river most bed load rates appeared higher when sampled with the hs152 the largest clasts collected by the hs76 also tend to be smaller than those obtained with the hs152 at the same flow analyzing paired bed load samples we find the probability of a bed load sample collected with the hs152 to be biased is around 43 in the conditions of the present study whereas 65 of samples were biased when obtained with the hs76 the analysis emphasizes the influence of bed material texture over sampler performance and demonstrates that the use of samplers with intake size much larger than bed grain size i e 5d will increase the accuracy of bed load grain size distributions and the precision of annual load estimates in gravel bed rivers

initial results of comparing cold seep carbonates from mussel and tubeworm associated environments at atwater valley lease block 340 northern gulf of mexico abstract chemosymbiotic macrofauna such as mussels and tubeworms and authigenic carbonates are typical of many hydrocarbon seeps to address whether mussels and tubeworms could impact the sediment geochemistry of their habitat where authigenic carbonates are precipitated a comparative study of petrographic and geochemical features of the authigenic carbonates from mussel and tubeworm associated environments at hydrocarbon seeps in atwater valley lease area block 340 at340 of the gulf of mexico was undertaken both mussel and tubeworm associated carbonates are dominated by high magnesium calcite hmc and aragonite and two tubeworm associated carbonate samples have minor amounts of dolomite the 13c values of all carbonates are low ranging from 60 8 to 35 5 pdb although there is much overlap surprisingly the 13c values of mussel associated carbonates are generally higher than those of tubeworm associated carbonates 51 8 vs 54 8 for an average of over 60 subsamples it is suggested that 1 carbon isotopic vital effect of seep mussels and tubeworms 2 fluid physical pumping of mussels and 3 release of sulfate by tubeworm roots may be responsible for the relatively lower 13c values of tubeworm associated carbonates it has been suggested that the heterogeneities in mineralogy and stable carbon isotope geochemistry of the seep carbonates may be attributed to the activity of macrofauna mussels and tubeworms and associated microbes our observations also suggest that at at340 the geochemical evolution of seep macrofauna is from a mussel dominated environment to a mixed mussel tubeworm environment and finally to a mostly tubeworm dominated environment this evolution is controlled mainly by the habitat e g hydrocarbon seep flux

evaluation of adcp apparent bed load velocity in a large sand bed river moving versus stationary boat conditions detailed mapping of bathymetry and apparent bed load velocity using a boat mounted acoustic doppler current profiler adcp was carried out along a 388 m section of the lower missouri river near columbia missouri sampling transects moving boat were completed at 5 and 20 m spacing along the study section stationary fixed boat measurements were made by maintaining constant boat position over a target point where the position of the boat did not deviate more than 3 m in any direction for each transect and stationary measurement apparent bed load velocity vb was estimated using adcp bottom tracking data and high precision real time kinematic rtk global positioning system gps the principal objectives of this research are to 1 determine whether boat motion introduces a bias in apparent bed load velocity measurements and 2 evaluate the reliability of adcp bed velocity measurements for a range of sediment transport environments results indicate that both high transport v b 0 6 m s and mo

bedload transport measurements at the erlenbach stream with geophones and automated basket samplers in the erlenbach stream a pre alpine steep channel in switzerland sediment transport has been monitored for more than 25 years near the confluence with the main valley river stream flow is monitored and sediment is collected in a retention basin with a capacity of about 2000 m3 the basin is surveyed at regular intervals and after large flood events in addition sediment transport has been continuously monitored with piezoelectric bedload impact and geophone sensors since 1986 in 2008 2009 the measuring system in the erlenbach stream was enhanced by installing an automatic system to obtain bedload samples movable metal baskets are mounted on a rail at the downstream wall of the large check dam above the retention basin and they can be moved automatically into the flow to take bedload transport samples the wire mesh of the baskets has a spacing of 10 mm to sample all sediment particles coarser than this size which is about the limiting grain size detected by the geophones the upgraded measuring system permits to obtain bedload samples over short sampling periods and to measure the grain size distribution of the transported material and its variation over time and with discharge the analysis of calibration relationships for the geophone measuring system confirms findings from very similar measurements which were performed until 1999 with piezoelectric bedload impact sensors there is a linear relationship between impulse counts and bedload mass passing over the sensors findings from flume experiments are used to discuss the most important factors which affect the calibration of the geophone signal the bedload transport rates as measured by the moving baskets are among the highest measured in natural streams with values of the order of several kilograms per meter per second copyright 2012 john wiley sons ltd

3 d flow and scour near a submerged wing dike adcp measurements on the missouri river 1 detailed mapping of bathymetry and three dimensional water velocities using a boat mounted single beam sonar and acoustic doppler current profiler adcp was carried out in the vicinity of two submerged wing dikes located in the lower missouri river near columbia missouri during high spring flows the wing dikes become submerged creating a unique combination of vertical flow separation and overtopping plunging flow conditions causing large scale three dimensional turbulent flow structures to form on three different days and for a range of discharges sampling transects at 5 and 20 m spacing were completed covering the area adjacent to and upstream and downstream from two different wing dikes the objectives of this research are to evaluate whether an adcp can identify and measure large scale flow features such as recirculating flow and vortex shedding that develop in the vicinity of a submerged wing dike and whether or not moving boat single transect data are sufficient for resolving complex three dimensional flow fields results indicate that spatial averaging from multiple nearby single transects may be more representative of an inherently complex temporally and spatially variable three dimensional flow field than repeated single transects results also indicate a correspondence between the location of calculated vortex cores resolved from the interpolated three dimensional flow field and the nearby scour holes providing new insight into the connections between vertically oriented coherent structures and local scour with the unique perspective of flow and morphology in a large river

prediction of discharge from water surface width in a braided river with implications for at a station hydraulic geometry 1 the total discharge of small braided rivers can be monitored nearly continuously using ground based orthorectified oblique images and a locally derived relationship between mean water surface width in a reach and total discharge with accuracy of the order of 10 the width discharge relationship is nearly linear over the normal range of summer flows measured in this proglacial stream the width discharge relation for a given location and channel configuration is transferable to adjacent reaches with different morphology with little loss in accuracy however the prospect of a more universal relation for braided rivers is remote because of differences in channel geometry and hydraulics between rivers the classical at a station hydraulic geometry exponent for width in this case is approximately 1 05 which is unique well above that observed in the few other braided rivers for which this has been derived and implies almost no change in mean velocity and depth with changing stage

linking the spatial distribution of bed load transport to morphological change during high flow events in a shallow braided river this paper provides novel observations linking the connections between spatially distributed bed load transport pathways hydraulic patterns and morphological change in a shallow gravel bed braided river these observations shed light on the mechanics of braiding processes and illustrate the potential to quantify coupled material fluxes using remotely sensed methods the paper focuses upon a 300 m long segment of the rees river new zealand and utilizes spatially dense observations from a mobile acoustic doppler current profiler adcp to map depth velocity and channel topography through a sequence of high flow events apparent bed load velocity is estimated from the bias in adcp bottom tracking and mapped to indicate bed load transport pathways terrestrial laser scanning tls of exposed bar surfaces is fused with the adcp surveys to generate spatially continuous digital elevation models which quantify morphological change through the sequence of events results map spatially distributed bed load pathways that were likely to link zones of erosion and deposition the coherence between the channel thalweg zone of maximum hydraulic forcing and maximum apparent bed load pathways varied this suggests that in places local sediment supply sources exerted a strong control on the distribution of bed load distinct from hydraulic forcing the principal braiding mechanisms observed were channel choking leading to subsequent bifurcation results show the connection between sediment sources pathways and sinks and their influence on channel morphology and flow path directions the methodology of coupling spatially dense adcp surveys with tls has considerable potential to understand connections between processes and morphological change in dynamic fluvial settings

sediment routing hypothesis for pool riffle maintenance this paper provides comprehensive evidence that sediment routing around pools is a key mechanism for pool riffle maintenance in sinuous upland gravel bed streams the findings suggest that pools do not require a reversal in energy for them to scour out any accumulated sediments if little or no sediments are fed into them a combination of clast tracing using passive integrated transponder pit tagging and bedload traps positioned along the thalweg on the upstream riffle pool entrance pool exit and downstream riffle are used to provide information on clast pathways and sediment sorting through a single pool riffle unit computational fluid dynamics cfd is also used to explore hydraulic variability and flow pathways clast tracing results provide a strong indication that clasts are not fed through pools rather they are transported across point bar surfaces or around bar edges depending upon previous clast position clast size and event magnitude spatial variations in bedload transport were found throughout the pool riffle unit the pool entrance bedload trap was often found to be empty when the others had filled further supporting the notion that little or no sediment was fed into the pool the pool exit slope trap would occasionally fill with sediment thought to be sourced from the eroding outer bank cfd results demonstrate higher pool shear stresses 140 n m 2 in a localized zone adjacent to an eroding outer bank compared to the upstream and downstream riffles 60 n m 2 at flows of 6 2 m3 s 1 60 of the bankfull discharge and above there was marginal evidence for near bed velocity reversal near bed streamlines produced from velocity vectors indicate that flow paths are diverted over the bar top rather than being fed through the thalweg some streamlines appear to brush the outer edge of the pool for the 4 9 m3 s 1 to 7 8 m3 s 1 between 50 and 80 of the bankfull discharge simulations however complete avoidance was found for discharges greater than this copyright 2013 john wiley sons ltd

variable source areas of bedload in a gravel bed stream abstract bedload texture is dependent on the spatially variable availability of mobile surface bed material distributed in patches or in other bedforms we measured bedload transport continuously with an automatic bedload station on the gravel bedded tordera river we also studied bed patchiness from pre flood vertical aerial photographs in a 40 m section upstream of the bedload station the results suggest that patches are the main source of sediment during the beginning of the flow event the median bedload size in low magnitude events depends on the percentage of total area occupied by patches of a given size patch areal extent and texture depend on the magnitude and general character of the previous flow event

modeling river bed morphology roughness and surface sedimentology using high resolution terrestrial laser scanning 1 recent advances in technology have revolutionized the acquisition of topographic data offering new perspectives on the structure and morphology of the earth s surface these developments have had a profound impact on the practice of river science creating a step change in the dimensionality resolution and precision of fluvial terrain models the emergence of hyperscale survey methods including structure from motion photogrammetry and terrestrial laser scanning tls now presents the opportunity to acquire 3 d point cloud data that capture grain scale detail over reach scale extents translating these data into geomorphologically relevant products is however not straightforward unlike traditional survey methods tls acquires observations rapidly and automatically but unselectively this results in considerable noise associated with backscatter from vegetation and other artifacts moreover the large data volumes are difficult to visualize require very high capacity storage and are not incorporated readily into gis and simulation models in this paper we analyze the geomorphological integrity of multiscale terrain models rendered from a tls survey of the braided river feshie scotland these raster terrain models are generated using a new computationally efficient geospatial toolkit the topographic point cloud analysis toolkit topcat this performs an intelligent decimation of point cloud data into a set of 2 5 d terrain models that retain information on the high frequency subgrid topography as the moments of the locally detrended elevation distribution the results quantify the degree of terrain generalization inherent in conventional fluvial dems and illustrate how subgrid topographic statistics can be used to map the spatial pattern of particle size grain roughness and sedimentary facies at the reach scale

measurements in a braided river chute and lobe 1 flow pattern sediment transport and channel change this paper and its companion ashworth et al this issue discuss measurements of channel change and associated flow and sediment transport processes in a representative chute and bar reach within a proglacial gravel bed river the sunwapta river in the canadian rockies during a week in which water discharge through the reach increased then decreased a sediment wave passed into and partly along the reach at first the chute aggraded then sediment was eroded from the chute and deposited in a prograding lobe to one side of the original bar head between two distributaries measurements of velocity shear stress and gravel transport rate revealed day to day changes in the divergent pattern of flow and sediment transport the off center location of the lobe reflected an initial asymmetry in the pattern of flow and sediment transport but as the lobe grew the flow and transport gradually switched away to the other distributary width averaged bed load transport rates do not agree well with average rates inferred from bar head deposition or from volumes and spatial patterns of scour and fill the indirect estimates are considered more reliable than those based on direct sampling for necessarily brief durations by the end of the study the new lobe had almost accreted onto the original bar head supporting the idea that most braid bars are of compound origin temporal and spatial patterns in grain size distributions of the bed bed load and deposited sediment are discussed in the companion paper