a stratigraphic framework for the preservation and shredding of environmental signals the stratigraphic record contains unique information about past landscapes and environmental change whether landscapes faithfully transmit signals of environmental change to stratigraphy is unknown because autogenic processes such as river avulsion can obscure signals prior to long term stratigraphic storage we develop a theoretical framework that predicts when a sediment flux signal will be transferred from the landscape to stratigraphy this threshold magnitude is a function of signal duration the magnitude is set by the maximum rate of autogenic volume change of the landscape which decreases with increasing time window physical delta experiments specifically designed to test our theory demonstrate that only sediment supply signals with a magnitude greater than the threshold are stored in stratigraphy supporting our theory this framework allows us to assess the fidelity of the stratigraphic record to archive past signals of environmental change and predict the short and long term impact of current anthropogenic forcing on landscapes

current measurements in rivers by spaceborne along track insar the global monitoring of river discharges is a technologically challenging problem with important applications in a variety of disciplines due to the limited availability and or quality of river runoff data from many regions an increasing use of remote sensing techniques is highly desirable altimeter specialists have already demonstrated water level retrievals in rivers from available data the along track interferometric synthetic aperture radar along track insar ati capabilities of state of the art imaging radars on satellites such as the german terrasar x which was launched on june 15 2007 also permit high resolution line of sight surface current measurements in this paper we evaluate the potential of current measurements in rivers by spaceborne ati on the basis of fundamental theoretical considerations existing spaceborne insar data from the shuttle radar topography mission srtm and simulated terrasar x data we show that an srtm derived line of sight surface current field in the elbe river germany agrees well with numerical hydrodynamic model results the data quality is sufficient to resolve characteristic lateral variations of the currents in the river around a pronounced main flow channel assuming that the flow direction is usually aligned with the river bed even a quasi 2d total surface current field can be derived simulations indicate that terrasar x was even better suited for current measurements in rivers depending on width surface roughness and relative flow direction of a river current estimates with an accuracy better than 0 1 m s were possible with an effective spatial resolution of a few hundred meters to kilometers

remote monitoring of volumetric discharge employing bathymetry determined from surface turbulence metrics current methods employed by the united states geological survey usgs to measure river discharge are manpower intensive expensive and during high flow events require field personnel to work in dangerous conditions indirect methods of estimating river discharge which involve the use of extrapolated rating curves can result in gross error during high flow conditions due to extrapolation error and or bathymetric change our goal is to develop a remote method of monitoring volumetric discharge that reduces costs at the same or improved accuracy compared with current methods while minimizing risk to field technicians we report the results of large scale particle image velocimetry lspiv and acoustic doppler velocimetry adv measurements conducted in a wide open channel under a range of flow conditions i e channel aspect ratio b h 6 6 31 9 reynolds number reh 4 950 73 800 and froude number fr 0 04 0 46 experiments were carried out for two different channel cross sections rectangular and asymmetric compound and two bathymetric roughness conditions smooth glass and rough gravel bed the results show that the mean surface velocity normalized by the depth averaged velocity the velocity index decreases with increasing h where is the boundary layer displacement thickness and that the integral length scales l11 1 and l22 1 calculated on the free surface vary predictably with the local flow depth remote determination of local depth averaged velocity and flow depth over a channel cross section yields an estimate of volumetric discharge

shredding of environmental signals by sediment transport 1 landscapes respond to climate tectonic motions and sea level but this response is mediated by sediment transport understanding transmission of environmental signals is crucial for predicting landscape response to climate change and interpreting paleo climate and tectonics from stratigraphy here we propose that sediment transport can act as a nonlinear filter that completely destroys shreds environmental signals this results from ubiquitous thresholds in sediment transport systems e g landsliding bed load transport and river avulsion this morphodynamic turbulence is analogous to turbulence in fluid flows where energy injected at one frequency is smeared across a range of scales we show with a numerical model that external signals are shredded when their time and amplitude scales fall within the ranges of morphodynamic turbulence as signal frequency increases signal preservation becomes the exception rather than the rule suggesting a critical re examination of purported sedimentary signals of external forcing citation jerolmack d j and c paola 2010 shredding of environmental signals by sediment transport geophys res lett 37 l19401 doi 10 1029 2010gl044638

bayhead deltas and shorelines insights from modern and ancient examples abstract bayhead deltas are important components of the rock record as well as modern estuaries hosting important hydrocarbon reservoirs and many coastal cities ports and large expanses of wetlands despite their significance few studies have summarized their occurrence and sedimentary characteristics in this paper we review the stratigraphic sedimentary and geomorphic characteristics of 68 modern and ancient bayhead deltas bayhead deltas are found in incised valleys structural basins fjords interdistributary bays of larger open ocean deltas and other backbarrier environments except for within fjords they generally prograde into shallower and more brackish waters than their open ocean equivalents as a result 80 of modern 68 of quaternary and 67 of ancient bayhead deltas have clinoform thicknesses of 10 m or less with 73 of modern bayhead deltas having clinoform thicknesses of 5 m or less additionally 89 of modern 81 of quaternary and 77 of ancient bayhead deltas examined are fluvial dominated we distinguish true bayhead deltas from their genetically similar bayhead shorelines which are not constructional features but sites of enhanced marsh or estuarine sedimentation near river mouths with inadequate rates of sediment delivery to form distributary channels and prograde into the estuary or lagoon we also distinguish confined bayhead deltas found in incised valleys structural basins and fjords from unconfined bayhead deltas found as incipient lobes of larger delta complexes and other back barrier lagoons the architecture of confined bayhead deltas is largely influenced by the limited accommodation brought about by the walls of the flooded valleys in which they are located as such confined bayhead delta ontogeny is controlled by many autogenic interactions within these valley walls both confined and unconfined bayhead deltas are sensitive to sea level rise climate controlled changes in sediment flux and tectonics their relatively small size connection with the terrestrial system and protected nature make them the ideal depositional system to record earth history including sea level and climate changes

streamflow properties from time series of surface velocity and stage time series of surface velocity and stage have been collected simultaneously surface velocity was measured using an array of newly developed continuous wave microwave sensors stage was obtained from the standard u s geological survey usgs measurements the depth of the river was measured several times during our experiments using sounding weights the data clearly showed that the point of zero flow was not the bottom at the measurement site indicating that a downstream control exists fathometer measurements confirmed this finding a model of the surface velocity expected at a site having a downstream control was developed the model showed that the standard form for the friction velocity does not apply to sites where a downstream control exists this model fit our measured surface velocity versus stage plots very well with reasonable values of the parameters discharges computed using the surface velocities and measured depths matched the usgs rating curve for the site values of depth weighted mea

transience and persistence in the depositional record of continental margins 1 continental shelves and coastal plains are large persistent depositional landforms which are stationary nonmigrating at their proximal ends and characterized by relatively steady long term growth in detail however their surface form and stratigraphic record is built of transient freely migrating landscape elements we derive the timescales of crossover from transient to persistent topographic forms using empirical scaling relations for mean sediment accumulation as a function of averaging time based upon tens of thousands of empirical measurements a stochastic noisy diffusion model with drift predicts all the gross features of the empirical data it satisfies first order goals of describing both the surface morphology and stratigraphic completeness of depositional systems the model crossover from noise dominated to drift dominated behavior corresponds to the empirical crossover from transport dominated autogenic transient behavior to accommodation dominated subsidence persistent behavior which begins at timescales of 102 103 years and is complete by scales of 104 105 years because the same long term scaling behavior emerges for off shelf environments it is not entirely explicable by steady subsidence fluctuations in sediment supply and routing probably have significant influence at short term transient scales the exponents of the scaling relations vary with environment particularly the prevalence of channeled sediment transport at very small scales modeling sediment transport as a diffusive process is inappropriate our results indicate that some of the timescales of interest for climate interpretation may fall within the transitional interval where neither accommodation nor transport processes are negligible and deconvolution is most challenging

application of an automated lspiv system in a mountainous stream for continuous flood flow measurements an imaging based automated large scale particle image velocimetry lspiv system for flash flood monitoring is developed and deployed in a mountainous stream in the longchi catchment chengdu china this system is built from a low cost raspberry pi board level computer with a camera module which can acquire continuous images videos automatically at programmed intervals the minimum quadratic difference algorithm tracks surface patterns as flow tracers to estimate the distribution of surface velocities meanwhile a stereo imaging based virtual pole method has been developed to reconstruct the three dimensional topography with a stereo digital camera and a cross sectional bathymetry has been generated without manual surveying the varying water stage and water surface gradient which are critical parameters that affect image rectification and surface velocity measurements can also be directly resolved by applying the two imaging modules together discharge can then be estimated with the velocity area method through selected cross sections a flash flood that occurred between 24 july 2014 and 25 july 2014 is selected for analysis the water surface level reconstructed from image processing was validated with marked water levels and a good agreement was found with a root mean square error of 3 7 cm the discharge recorded during the flood recession process ranged from approximately 3 5 to 27 m3 s the rating curve obtained can be well described by a power function and the linear regression suggested a manning s n roughness coefficient of 0 18 of one specific cross section some limitations of the presented large scale particle image velocimetry system are also put forward and possible solutions are provided for future improvements with these proposed upgrades the system can provide valuable datasets of flash floods in steep mountainous streams which are critically needed for improving our understanding and modelling of many hydrological processes associated with flood generation propagation and erosion as well as for real time forecasting copyright 2016 john wiley sons ltd

measuring stream discharge by non contact methods a proof of concept experiment this report describes an experiment to make a completely non contact open channel discharge measurement a van mounted pulsed doppler 10ghz radar collected surface velocity data across the 183 m wide skagit river washington at a usgs streamgaging station using bragg scattering from short waves produced by turbulent boils on the surface of the river surface velocities were converted to mean velocities for 25 sub sections by assuming a normal open channel velocity profile surface velocity times 0 85 channel cross sectional area was measured using a 100 mhz ground penetrating radar antenna suspended from a cableway car over the river seven acoustic doppler current profiler discharge measurements and a conventional current meter discharge measurement were also made three non contact discharge measurements completed in about a 1 hour period were within 1 of the gaging station rating curve discharge values with further refinements it is thought that open channel flow can be measured reliably by non contact methods

seismicity of the forearc marginal wedge accretionary prism three different types of seismic data have been examined for seismic events occurring within the zone called the accreted wedge or forearc marginal wedge that underlies the inner trench wall of some arcs these types of data are 1 teleseismically recorded earthquakes that have been reported in the literature as occurring in major arc trench regions these events fail to demonstrate that earthquakes occur within the accreted wedge because the uncertainty of focal depth usually exceeds the depth dimension of the accreted wedge these data include many tsunamigenic earthquakes 2 local earthquakes located by combined ocean bottom seismograph and land networks in the arc trench region in the new hebrides and the central and eastern aleutian trench none of the more reliable of these hypocenters lies within the accreted wedge 3 s p intervals measured at stations on islands located on the outer ridge or at ocean bottom seismograph stations on the forearc marginal wedge these data do not show the existence of events occurring within the accreted wedge e g from 18 ocean bottom seismograph stations with a cumulative operation time of about 1 year the smallest s p time is about 2 5 s for events in the new hebrides and about 4 s for events in the adak and kodiak regions we found no s p time smaller than 2 s from 6 years of seismograms recorded at middleton island alaska and no s p time smaller than 4 s from 25 years of seismograms recorded on barbados all of the events could have occurred outside the forearc marginal wedge although we have located no events with hypocenters which are situated unambiguously within the accreted wedge we have located many events which occurred in the vicinity of the accreted wedge some occur in the upper portion of the benioff zone shallower than about 40 km and others occur in the leading edge of the overriding plate these locations reported in this paper which are within or close to the seismic networks comprise some of the most reliably located shallow events ever reported in convergent margins of island arcs the absence of seismic activity within the accreted wedge in any island arc that we studied suggests that the deformation evident in this region occurs aseismically

measuring flood discharge in unstable stream channels using ground penetrating radar field experiments were conducted to test the ability of ground penetrating radar gpr to measure stream channel cross sections at high flows without the necessity of placing instruments in the water experiments were conducted at four u s geological survey gaging stations in southwest washington state with the gpr antenna suspended above the water surface from a bridge or cableway traverses were made across stream channels to collect radar profile plots of the streambed subsequent measurements of water depth were made using conventional depth measuring equipment weight and tape and were used to calculate radar signal velocities other streamflow parameter data were collected to examine their relation to radar signal velocity and to clarity of streambed definition these initial tests indicate that gpr is capable of producing a reasonably accurate 20 stream channel profile and discharge far more quickly than conventional stream gaging procedures while avoiding the problems and hazards associated with placing instruments in the water

interaction between bed roughness and flow hydraulics in eroding rills govers 1992 showed that the flow velocity in rills eroding loose nonlayered materials could be predicted from knowledge of discharge only without significant slope or soil effect the objective of this paper is to investigate to what extent the observed slope independence of flow velocity in eroding rills can be explained by the interaction between rill bed roughness and flow hydraulics in a laboratory study two situations were compared 1 rills which can freely erode a uniform soil layer and 2 rills with a fixed bed geometry during the experiments rill discharge and flow velocity were recorded after each experiment a detailed topographic survey of the rill bed was carried out using a laser scanner from these data the main hydraulic variables mean values of flow depth wetted perimeter and hydraulic radius were estimated the experiments confirmed the slope independence of rill flow velocities on mobile beds when the bed is fixed the flow velocity in rills is clearly slope dependent the slope independence of flow velocity on mobile beds is due to a feedback between rill bed morphology and flow conditions the roughness amplitude which was assessed from the standard deviation of corrected height values and the frequency of macroroughness elements which was assessed by counting the number of peaks per unit length in a previously simplified longitudinal profiles both increase and tend to counteract the effect of the increase in slope gradient on rill flow velocity the final rill flow velocity appears to be characterized by a constant average froude number

morphodynamic modeling of fluvial channel fill and avulsion time scales during early holocene transgression as substantiated by the incised valley stratigraphy of the trinity river texas the trinity river system provides a natural laboratory for linking fluvial morphodynamics to stratigraphy produced by sea level rise because the sediments occupying the trinity incised valley are well constrained in terms of timing of deposition and facies distribution herein the trinity river is modeled for a range of base level rise rates avulsion thresholds and water discharges to explore the effects of backwater induced in channel sedimentation on channel avulsion the findings are compared to observed sediment facies to evaluate the capability of a morphodynamic model to reproduce sediment deposition patterns base level rise produces mobile locations of in channel sedimentation and deltaic channel avulsions for scenarios characteristic of early holocene sea level rise 4 3 mm yr 1 the trinity fluvial deltaic system progrades 13 m yr 1 followed by backstepping of 27 m yr 1 avulsion is reached at the position of maximum sediment deposition located 108 km upstream of the outlet after 3 548 model years based on sedimentation filling 30 of the channel under scenarios of greater base level rise avulsion is impeded because the channel fill threshold is never achieved accounting for partitioning of bed material sediment between the channel and floodplain influences the timing and location of avulsion over millennial time scales the time to avulsion is greatly increased sedimentation patterns within the valley modeled and measured indicate preference toward sandy bed material and the rates of deposition are substantiated by previous measurements although the results here are specific to the trinity river the analysis provides a framework that is adaptable to other lowland fluvial deltaic systems

high resolution sequence stratigraphy of fluvio deltaic systems prospects of system wide chronostratigraphic correlation a basin scale numerical model with a sub grid parameterization of fluvio deltaic processes and stratigraphy was used to study the relation between alluvial sedimentation and marine deltaic deposition under conditions of time invariant forcing the experiments show that delta evolution is governed by a robust morphodynamic feedback loop which provides a link between major avulsions delta lobe switches and sequestration of sediments on the delta plain major avulsions driven by local superelevation result in abandonment of delta lobes and initiation of new lobes progradation of the delta front lengthens the fluvial profile and reduces its gradient which induces aggradation upstream the aggradation in turn causes local superelevation of the channel belt each major avulsion causes a wave of incision to migrate upstream whereas downstream of the avulsion point the rate of aggradation temporarily increases until a new equilibrium situation has been established the feedback loop explains storage and release of fluvial sediments without the need to invoke changes in upstream or downstream controls and provides a plausible mechanism for the generation of high frequency incision aggradation cycles as the sole result of compensational stacking the stratigraphic expression of a depocentre shift is an essentially isochronous surface hence the stratigraphic record of fluvio deltaic systems may be subdivided into a series of units representing intervals during which a channel belt and delta lobe were forming at a fixed location in the basin so called chronosomes fluvio deltaic chronosomes are bounded by abandonment surfaces which are clearly expressed in the marine as well as the fluvial domain the surface marking the abandonment of a particular channel belt and delta lobe correlates with the surface at the base of a new delta lobe landward this surface forms the base of an aggradational package of fluvial sediments downstream of an avulsion site associated with a lobe switch upstream of this site the conformable surface passes into a surface of fluvial incision and terrace formation onlapped by aggradational channel belt deposits identification of the isochronous bounding surfaces of chronosomes in the field offers the attractive prospect of high resolution chronostratigraphic correlation throughout fluvio deltaic systems

sediment storage partitioning in alluvial stratigraphy the influence of discharge variability abstract numerical models of formation of alluvial stratigraphy often specify either explicitly or implicitly the proportion of channel and overbank sediments that are deposited during a given interval of time however little is known about the factors that affect the partitioning of sediment between channels and the overbank environment over long time intervals and the fidelity with which that partition is preserved in the stratigraphic record here we use physical experiments to investigate the role that discharge variability plays in this partitioning in fluvial stratigraphy we find that channels formed under constant flow conditions have low lateral mobility and act mostly as conduits for sediments to reach the shoreline the bulk of the aggradation in this case is derived from sediment laden flow that escapes the main channels by contrast including floods increases channel lateral mobility and this change is recorded in stratigraphy as an increased proportion of channel deposits relative to overbank deposits when variable flow is included as an input condition a large volume of in channel deposition occurs rendering the channels substantial contributors to stratigraphic volume on their own the increase in channel deposit volume is driven mainly by a threefold increase in the average time that a location is subject to in channel aggradation other factors include a slight increase of in channel aggradation rates and an increase in erosion of the overbank environment that results from energetic overbank flows our study shows that the character of a river s hydrograph exerts a significant influence on the proportion of channel to overbank sediment bodies in alluvial successions which is an unexamined source of uncertainty in common stratigraphic models

development and application of an automated river estuary discharge imaging system abstractan automated river estuary discharge imaging system aredis is developed to measure the velocity of a wide tidal estuary the system contains near and far field cameras that capture the entire 370 m wide channel from an oblique angle with high image resolution a new rotational scheme is developed to calibrate the cameras wakes generated by flow past bridge piers are found to be natural tracers for large scale particle image velocimetry lspiv to reliably and accurately measure the surface velocity confirmed by buoy tracking velocimetry btv the success of aredis is demonstrated in three field measurements on the danshui river the largest estuary in taiwan first aredis is used to measure discharge over the entire tidal cycle under normal flow and a 10 difference is found between discharges measured with aredis and a boat mounted acoustic doppler profiler second aredis is employed to measure discharge under a typhoon event resulting in discharges 45 greater than those at normal flow

flow measurement in streams using video imagery 1 a video imagery technique for making flow measurements in streams and waterways is presented and used to estimate discharge for clear creek near oxford iowa a video camera was used to visualize the flow seeded with tracers measurements of free surface flow velocities were then made using particle image velocimetry piv techniques the velocity measurements were used as input to a hydraulic model which uses kinematic principles conservation of mass to derive three dimensional flow fields for discharge estimation a survey of five channel cross sections over a 7 15 m length of stream were made to define the channel bathymetry for the hydraulic model the average channel width was 5 7 m and the average depth was 0 2 m the discharge estimate using the video technique 0 183 m3 s compares well with the current meter discharge measurement 0 192 m3 s with an estimated standard error of 6 4 the root mean square difference of the depth averaged velocity at the locations of the current meter measurements was 0 032 m s potential applications of the video imagery technique include measurements of flood flows at ungaged sites river monitoring from a remote site and estimation of two and three dimensional flow components

scale dependent compensational stacking an estimate of autogenic time scales in channelized sedimentary deposits recent studies show that paleoenvironmental allogenic signals preserved in the stratigraphic record may be contaminated or overprinted by internally generated autogenic sedimentation this is problematic but it is unclear over what temporal and spatial scales autogenic patterns are most prevalent we propose that scale breaks in basin fi lling trends can be used to identify the transition between allogenic and autogenic stratigraphy using data from numerical and physical experiments and an ancient outcrop we explore how compensation the tendency for sediment transport systems to preferentially fi ll topographic lows varies with stratigraphic scale object based models demonstrate the temporal scales at which stratigraphy changes from being partially infl uenced by autogenic processes to being completely determined by allo genic forcings and suggest that this transition occurs at a time scale set by the maximum scale of surface roughness in a transport system divided by the long term aggradation rate this hypothesis is validated in a physical experiment where delta topography was monitored along fl ow perpendicular transects at a high temporal resolution relative to channel kine matics the strength of compensation in the experiment changes at the predicted time scale where the maxi mum surface roughness is equal to the depth of the experimental channels above this compensation time scale deposits stack purely compensationally but below this time scale deposits stack somewhere between randomly and deterministically similar scale dependent stacking is also observed in the ferris formation cretaceous paleogene hanna basin wyoming united states this study demonstrates that scale dependent compensational stack ing may be useful for isolating allogenic and autogenic stratigraphy in sedimentary basins

autogenic erosional surfaces in fluvio deltaic stratigraphy from floods avulsions and backwater hydrodynamics erosional surfaces set the architecture of fluvio deltaic stratigraphy and they have classically been interpreted in terms of changes in boundary conditions such as climate tectonics and base level allogenic forces intrinsic dynamics of sedimentary systems autogenic dynamics can also create a rich stratigraphic architecture and a major knowledge gap exists in parsing the relative roles of autogenic versus allogenic processes emerging theoretical and experimental work suggests that backwater hydrodynamics play an important role in driving transient channel incision in river deltas even those experiencing net aggradation here we identify and quantify two autogenic mechanisms that produce broad erosional surfaces in fluvio deltaic stratigraphy namely floods and avulsions using a simple mass balance model for single threaded delta channel systems we show that flood induced scours begin near the shoreline and avulsion induced scours begin at the avulsion site and both propagate upstream over a distance that scales with the backwater length bed slope and bed grain size we also develop scaling relationships for the maximum scour depths arising from these mechanisms which are functions of characteristic flow depth and formative flood variability we test our theoretical predictions using a flume experiment of river delta evolution governed by persistent backwater hydrodynamics under constant relative sea level results indicate that autogenic dynamics of backwater mediated deltas under conditions of constant base level can result in stratigraphic surfaces and shoreline trajectories similar to those often interpreted to represent multiple sea level cycles our work provides a quantitative framework to decouple autogenic and allogenic controls on erosional surfaces preserved in fluvio deltaic stratigraphy

water velocity and the nature of critical flow in large rapids on the colorado river utah 1 rapids are an integral part of bedrock controlled rivers influencing aquatic ecology geomorphology and recreational value flow measurements in rapids and high gradient rivers are uncommon because of technical difficulties associated with positioning and operating sufficiently robust instruments in the current study detailed velocity water surface and bathymetric data were collected within rapids on the colorado river in eastern utah with the water surface survey it was found that shoreline based water surface surveys may misrepresent the water surface slope along the centerline of a rapid flow velocities were measured with an adcp and an electronic pitot static tube integrating multiple measurements the adcp returned velocity data from the entire water column even in sections of high water velocity the maximum mean velocity measured with the adcp was 3 7 m s the pitot static tube while capable of only point measurements quantified velocity 0 39 m below the surface the maximum mean velocity measured with the pitot tube was 5 2 m s with instantaneous velocities up to 6 5 m s analysis of the data showed that flow was subcritical throughout all measured rapids with a maximum measured froude number of 0 7 in the largest measured rapids froude numbers were highest at the entrance of a given rapid then decreased below the first breaking waves in the absence of detailed bathymetric and velocity data the froude number in the fastest flowing section of a rapid was estimated from near surface velocity and depth soundings alone

digital mapping of riverine waterway hydrodynamic and geomorphic features this paper proposes an innovative non intrusive method for mapping waterway characteristics in riverine areas the technique uses photogrammetry to provide quantitative information about the dry area in the vicinity of the waterways banks and floodplain and image processing algorithms to characterize the flow riverside images of a riverine area are decomposed into quasi planar areas and ortho rectified and re assembled to obtain a panoramic ortho view of the area of interest morphological features of interest such as river bank positions flood plain edges mud deposits vegetation and erosion patterns are then identified on the ortho view and mapped digitally image sequences of the river flow are recorded allowing a surface velocity analysis to be obtained through large scale particle image velocimetry lspiv finally the mapped elements and the surface velocities are displayed together in a gis like visualization through the presentation of a case study of a flood event at a culvert site this paper demonstrates the capability of the technique to monitor characteristics of waterways over time the method is inexpen sive a conventional video or digital camera can be used fast and requires minimum preparation it can be applied in such important river related research areas as morphodynamic and sediment transport studies it also fosters an improved understand ing of the coupling between the river and its banks which is essential for river restoration and eco habitat studies the present methodology is readily available for implementation in routine bridge inspections fitted with an easy to use graphical interface copyright 2009 john wiley sons ltd

the human role in changing fluvial systems retrospect inventory and prospect historical and modern scientific contexts are provided for the 2006 binghamton geomorphology symposium on thehuman role in changing fluvial systems the 2006 symposium provides a synthesis of research concerned with human impacts on fluvial systems including hydrologic and geomorphic changes to watersheds while also commemorating the 50th anniversary of the 1955man s role in changingthe face of the earth symposium thomas jr w l ed 1956a man srole in changing the face of the earth univ chicago press chicago 1193 pp this paper examines the 1955symposium from the perspective of humanimpacts on rivers reviews current inquiry on anthropogenic interactions in fluvial systems and anticipates future directions in this field although the 1955 symposium did not have an explicit geomorphic focus it set the stage for many subsequent anthropogeomorphic studies the 1955 conference provided guidance to geomorphologists by recommending and practicing interdisciplinary scholarship through the use of diverse methodologies applied at extensive temporal and geographical scales and through its insistence on an integrated understanding of human interactions with nature since 1956 research on human impacts to fluvial systems has been influenced by fundamental changes in why the research is done what is studied how river studies are conducted and who does the research rationales for river research are now driven to a greater degree by institutional needs environmental regulations and aquatic restoration new techniques include a host of dating spatial imaging and ground measurement methods that can be coupled with analytical functions and digital models these new methods have led to a greater understanding of channel change variations across multiple temporal and spatial scales and integrated watershed perspectives all changes that are reflected by the papers in this volume these new methods also bring a set of technical demands for the training of geomorphologists the 2006 binghamton geomorphology symposium complements the 1956 symposium by providing a more specific and updated view of river systems coupled with human interactions the symposium focuses on linkages between human land use structures and channel modification with geomorphology hydrology and ecology the emergence of sustainability as a central policy guideline in environmental management should generate greater interest in geomorphic perspectives especially as they pertain to human activities the lack of theories of anthropogeomorphic change however presents a challenge for the next generation of geomorphologists in this rapidly growing subfield

anisotropy and large scale lateral inhomogeneity of the upper mantle abstract an investigation of travel time residuals of p waves as compared to an average global travel time curve with a base line determined shows that about 400 500 km of the upper mantle at the boundary with the crust and a similar thickness of the lower mantle at the boundary with the core are laterally inhomogeneous the upper mantle both under continents and under oceans consists of crust mantle blocks distinguished by longitudinal wave velocity surface tectonics and intensity of the heat flow it has been revealed that within individual crust mantle blocks there is an azimuthal relationship of p wave travel time indicative of possible anisotropy of upper mantle elastic properties down to depths of the order of several hundred kilometers

a big fan of signals exploring autogenic and allogenic process and product in a numerical stratigraphic forward model of submarine fan development distinguishing an allogenic signal from trends and patterns produced by autogenic processes is a critical element in interpreting understanding and predicting strata lobyte3d is a new reduced complexity model of dispersive flow over an evolving topography on fan systems that produces surprisingly complex potentially hierarchical strata despite a simple formulation two submarine fan model scenarios are run one with constant sediment input and one with a sinusoidal variation in sediment input with an oscillation period of 25 ky and a peak to trough 80 volume change both model scenarios show that flows cluster to produce lobes which migrate and can rapidly switch location runs tests that can detect thickening and thinning bed trends and spectral analysis that detects the frequency of any signal present suggest that strata can be ordered even in the absence of any allogenic signal with cycles and trends in bed thickness but no single characteristic frequency in the oscillating supply scenario an allogenic signal is present in places particularly in the axial mid fan but may be difficult to distinguish from the autogenic signal with only limited outcrop data and without knowing a priori how the allogenic signal is likely to be preserved in complex and incomplete strata based on these limited model results we hypothesize that analysis of mid fan vertical sections using simple power spectrum analysis and counting of the significant peaks present across a range of frequencies may allow identification of a signal bump that could be evidence of the presence and nature of allocyclic forcing further lobyte3d modeling work will explore if and how the signal bump is preserved with input signals across a range of frequencies and amplitudes to guide further data collection and interpretation in outcrop and subsurface strata

terrestrial heat flow in the northwestern pacific abstract on the basis of 150 new heat flow measurements the thermal structure of the uppermost layer of the earth in the transition zone of the northwestern pacific and relation of heat flow values to the age of tectonic magmatic activity have been established an analysis was made of the main factors distorting the geothermal field in the region under study and a map of measured and background heat flow values was constructed calculations were made to determine the temperatures in the deep crust and upper mantle along the dss profiles in the northwestern pacific and a map was constructed showing the depth of the zone of fractional melting 1200 c isotherm identified with the upper boundary of the asthenospheric layer

river discharge measurements by using helicopter mounted radar 1 the united states geological survey and the university of washington collaborated on a series of initial experiments on the lewis toutle and cowlitz rivers during september 2000 and a detailed experiment on the cowlitz river during may 2001 to determine the feasibility of using helicopter mounted radar to measure river discharge surface velocities were measured using a pulsed doppler radar and river depth was measured using ground penetrating radar surface velocities were converted to mean velocities and horizontal registration of both velocity and depth measurements enabled the calculation of river discharge the magnitude of the uncertainty in velocity and depth indicate that the method error is in the range of 5 percent the results of this experiment indicate that helicopter mounted radar can make the rapid accurate discharge measurements that are needed in remote locations and during regional floods

influence of sediment cohesion on deltaic morphodynamics and stratigraphy over basin filling time scales results from physical and numerical experiments suggest that sediment cohesion influences deltaic morphodynamics by promoting the development and maintenance of channels as a result cohesion is thought to increase the magnitude and time scales of internally generated autogenic processes and the dimensions of their stratigraphic products we test these hypotheses by examining the surface processes and stratigraphic products from a suite of physical experiments where the influence of cohesion is isolated over temporal and spatial scales important for basin filling given the stochastic nature of autogenic sediment transport processes we develop and employ a range of statistical tools and metrics we observe that 1 an increase in sediment cohesion decreases lateral channel mobility and thus increases the time necessary to regrade deltaic surfaces 2 enhanced channelization due to sediment cohesion increases the time necessary for the deposits of autogenic processes to average together and produce stratigraphic products with shapes set by the generation of regional accommodation 3 cohesion promotes the transport of suspended sediment to terrestrial overbank and marine environments which decreases the volume of channel relative to overbank and marine deposits in the stratigraphic record this increase in overbank and marine deposition changes the spatial distribution of sand in stratigraphy with higher cohesion linked to enhanced segregation of fine particles from coarse sand in the experimental deposits combined these results illustrate how the cohesion of sediment is fundamental in setting autogenic spatial and temporal scales and needs to be considered when inverting stratigraphic architecture for paleo environmental history

two dimensional hydraulic flood modelling using a finite element mesh decomposed according to vegetation and topographic features derived from airborne scanning laser altimetry airborne scanning laser altimetry lidar is an important new data source that can provide two dimensional river flood models with spatially distributed floodplain topography for model bathymetry together with vegetation heights for parameterization of model friction methods are described for improving such models by decomposing the model s finite element mesh to reflect floodplain vegetation features such as hedges and trees having different frictional properties to their surroundings and significant floodplain topographic features having high height curvatures the decomposition is achieved using an image segmentation system that converts the lidar height image into separate images of surface topography and vegetation height at each point the vegetation height map is used to estimate a friction factor at each mesh node the spatially distributed friction model has the advantage that it is physically based and removes the need for a model calibration exercise in which free parameters specifying friction in the channel and floodplain are adjusted to achieve best fit between modelled and observed flood extents the scheme was tested in a modelling study of a flood that occurred on the river severn uk in 1998 a satellite synthetic aperture radar image of flood extent was used to validate the model predictions the simulated hydraulics using the decomposed mesh gave a better representation of the observed flood extent than the more simplistic but computationally efficient approach of sampling topography and vegetation friction factors on to larger floodplain elements in an undecomposed mesh as well as the traditional approach using no lidar derived data but simply using a constant floodplain friction factor use of the decomposed mesh also allowed velocity variations to be predicted in the neighbourhood of vegetation features such as hedges these variations could be of use in predicting localized erosion and deposition patterns that might result in the event of a flood copyright 2003 john wiley sons ltd

field measurement of the velocity of overland flow using dye tracing a new method of computing the mean velocity of overland flow using dye tracing is proposed in which a specified cross section is divided into zones of relatively uniform flow characteristics termed partial sections the mean surface velocity for each partial section is determined by timing the passage of injected dye and this figure is multiplied by 0 67 0 70 or 0 80 depending on whether the flow is laminar transitional or turbulent to give mean velocity the mean velocity for the entire cross section is calculated by multiplying the mean velocity of each partial section by its cross sectional area summing the products for all the partial sections and dividing by the total area of the cross section a field test shows that mean velocity derived in this manner differs from mean velocity derived by the discharge method i e by dividing discharge measured volumetrically by cross sectional area by an average of only 7 07 per cent thus the partial section technique appears to provide a reliable method of estimating mean velocity of overland flow

resolving two dimensional flow structure in rivers using large scale particle image velocimetry an example from a stream confluence large scale particle image velocimetry lspiv has emerged as a valuable tool for measuring surface velocity in a variety of fluvial systems lspiv has typically been used in the field to obtain velocity or discharge measurements in relatively simple one dimensional flow detailed two dimensional or three dimensional characterization of flow structure has been relegated to laboratory settings because of the difficulty in controlling piv limiting factors such as poor particle seeding the need for camera rectification and challenging field conditions in this study we implement a low cost lspiv setup using a high resolution action camera mounted above a stream confluence and water seeded with recycled landscape mulch time averaged 2d velocities derived from lspiv are compared with those measured with an acoustic doppler velocimeter adv in the camera s field of view we also assess the capabilities of this setup to resolve both turbulent and time averaged flow structures at a stream confluence our results reveal that even in challenging field conditions a basic lspiv setup can yield accurate data on velocity and resolve in detail the temporal evolution of flow structures on the surface of rivers the resulting dataset contains velocity information at high spatial and temporal resolution a significant advance in understanding flow processes at stream confluences our lspiv analysis provides support for previous numerical modeling studies that have distinguished between kelvin helmholtz and wake modes of turbulent behavior within the mixing interface at confluences this study shows that lspiv should be considered as both an alternative for traditional methods and a tool that can provide unprecedented levels of resolution of surface velocity patterns on rivers that can be used to evaluate numerical predictions of flow structure in complex fluvial environments this article is protected by copyright all rights reserved

autogenic sedimentation in clastic stratigraphy internally generated or autogenic terrestrial and marine sediment transport dynamics can produce depositional patterns similar to those associated with climatic tectonic or sea level changes a central challenge in accurately interpreting the sedimentary archive is determining what scales and types of deposits reflect autogenic controls on sedimentation in different environments autogenic sediment transport dynamics commonly result from intermittent sediment storage in transient landforms which produces episodic spatially discontinuous sedimentation across a basin the transition from localized variable sedimentation to even basin wide sedimentation marks the shift from stochastic landscape dynamics to deterministic deposition responding to the long term balance between sediment supply and the creation of space to accommodate sediment this threshold can be measured in a wide variety of stratigraphic successions and has important bearing on whether climatic tectonic or sea level signals can be

mantle heterogeneities within active margins of the world oceans and their seismological characteristics abstract the principal geotectonic element of active marginal areas is represented by arcuate structures characterized by two mantle volumes in contact containing materials with different properties the rigid high density and comparatively cold region with concentrated earthquake hypocentres is accompanied by an aseismic mantle where a low velocity layer at depths from 150 to 250 km and a low velocity zone under the present volcanoes form a specific volume p wave velocity of the latter is nearly 15 below the standard values and nearly 20 lower than that in the adjacent seismically active blocks as a result of these lateral changes in the physical properties there appears to exist a considerable gradient of lithostatic pressure whose maximum occurs in the focal zone and its resulting forces point to the arc centre thus determining the horizontal displacement of sinking high density matter with the focal zone velocity changes of the aseismic mantle block along the geostructure are determined by the geological evolution of the region and reflected in its morphostructure in shallow parts of the northern sea of okhotsk and western kamchatka with continenetal type of crust developed on the bottom of the pre mesozoic platform the p wave velocities in the upper mantle are 0 5 0 6 km s smaller than those under the kuril abyssal plain with suboceanic crust small scale mantle inhomogeneities of the focal zone manifest themselves in a seismic anisotropy which changes both in magnitude and direction it reflects a reaction of the medium to the shearing stresses and is controlled by strength anisotropy distribution of seismic parameters velocity and attenuation of elastic waves in the mantle of active margins is represented by alternating areas of high and low strength weaker areas coincide both in setting and trend with deep seated faults which cut across the arcuate geofeatures this combination of arcuate and orthogonal tectonic systems in the northwestern pacific under the conditions of tensile stresses which act along the island arc favours a displacement of the central portion of the island arc toward the ocean

generation and verification of theoretical rating curves in the whitewater river basin kansas 1 a new method for generating stage discharge relations rating curves for geomorphically stable channels is presented and applied to two streams in the whitewater river basin kansas the approach converts measurements of stage into discharge using a fluid mechanically based model the model does not use empirical roughness coefficients such as manning coefficients but rather determines channel roughness from field measurements of the 1 channel geometry 2 the physical roughness of the bed banks and floodplain and 3 the vegetation density on the banks and floodplain these measurements are used to calculate explicitly the drag on the small scale topographic features on the boundary the drag on the stems and branches of woody vegetation and the friction on the bed banks and floodplain the theoretical rating curves produced by the model for two study reaches which are near u s geological survey usgs streamflow gauging stations are in good agreement with direct measurements of discharge made by the usgs our method has the potential of providing accurate estimates of stream flows less expensively than conventional gauging methods in addition the method can be used to obtain more accurate discharge estimates than conventional indirect methods for determining discharge which are based on estimates of manning s coefficient

two dimensional velocity distribution modeling for natural river based on uhf radar surface current abstract non contact flow measurement method plays an increasingly important role in river discharge measurement however most channel cross section velocity distribution models proposed by researchers have certain limitations in application underwater velocities are always necessary when applied in narrow channels which makes it challenging to calculate natural river discharge using water surface velocities measured by remote sensing instruments this letter takes water surface velocities detected by uhf radar as boundary conditions and a new velocity distribution model is derived based on the reynolds averaged navier stokes rans equations uhf radar measures surface velocities of the cross section and velocities on the river bed of the cross section are considered to be 0 the rans equations are simplified to be a two dimensional poisson equation and the cross section velocity distribution is solved by using the closed boundary conditions some field experiments were conducted in the hanjiang river at xiantao hubei china in september 2017 and april july 2018 the processing results of which show that the proposed model is superior to the power law and the log law models especially near the side wall narrow channel region river discharges calculated by this method are highly consistent with those provided by hubei xiantao hydrologic station which verifies the reliability of the model and the feasibility of using uhf radar to measure natural river discharge continuously and automatically

quantifying riverine surface currents from time sequences of thermal infrared imagery 1 river surface currents are quantified from thermal and visible band imagery using two methods one method utilizes time stacks of pixel intensity to estimate the streamwise velocity at multiple locations the other method uses particle image velocimetry to solve for optimal two dimensional pixel displacements between successive frames field validation was carried out on the wolf river a small coastal plain river near landon mississippi united states on 26 27 may 2010 by collecting imagery in association with in situ velocities sampled using electromagnetic current meters deployed 0 1 m below the river surface comparisons are made between mean in situ velocities and image derived velocities from 23 thermal and 6 visible band image sequences 5 min length during daylight and darkness conditions the thermal signal was a small apparent temperature contrast induced by turbulent mixing of a thin layer of cooler water near the river surface with underlying warmer water the visible band signal was foam on the water surface for thermal imagery streamwise velocities derived from the pixel time stack and particle image velocimetry technique were generally highly correlated to mean streamwise current meter velocities during darkness r2 typically greater than 0 9 and early morning daylight r2 typically greater than 0 83 streamwise velocities from the pixel time stack technique had high correlation for visible band imagery during early morning daylight hours with respect to mean current meter velocities r2 0 86 streamwise velocities for the particle image velocimetry technique for visible band imagery had weaker correlations with only three out of six correlations performed having an r2 exceeding 0 6

a novel method for measuring the timing of bed erosion during debris flows and floods 1 we describe a novel channel bed erosion sensor and the first results of its usage the sensor is based on a resistance chain built into a column of 5 cm tall cylindrical aluminum elements the timing and change in resistance as elements are removed from the column are logged outside of the channel five sensor columns were placed in the illgraben torrent bed prior to the start of the 2008 flow season before the first debris flow event 0 1 m of sediment was deposited by small flood events during the 16 june 2008 debris flow this layer was eroded and erosion was therefore first measured 44 min after front arrival and took place progressively over the next 12 min the results at the erosion sensors are consistent with measurements over the entire reach using traditional surveying methods and data from the adjacent debris flow monitoring station provide a basis for interpretation the main limitation is that this sensor records only the rate and timing of the maximum bed erosion and cannot be used to determine deposition and subsequent erosion within a given event

sequence stratigraphy of experimental strata under known conditions of differential subsidence and variable base level sequence stratigraphy has been applied from reservoir to continental scales providing a scale independent model for predicting the spatial arrangement of depositional elements we examine experimental strata deposited in the experimental earthscape facility at st anthony falls laboratory focusing on stratigraphic surfaces defined by discordant contact geometries surfaces analogous to those delineated in the original work on seismic sequence stratigraphy in this controlled setting we directly evaluate critical sequence stratigraphic issues such as stratigraphic horizon development and time significance as well as the internal geometry and migration of the bounded strata against the known boundary conditions and depositional history four key stratigraphic disconformities defined by marine downlap marine onlap fluvial erosion and fluvial onlap are mapped and vary greatly in their relative degree of time transgression marine onlap and downlap contacts closely parallel topographic surfaces time surfaces and prior to burial approximate the instantaneous offshore topography these stratal bounding surfaces are also robust stratigraphic signals of relative base level fall and rise respectively marine onlap surfaces are of special interest they tend to be the best preserved discordance where widespread allogenic based onlap surfaces subdivide otherwise amalgamated depositional cycles amidst cryptic stacks of marine foresets however local autogenic based marine onlap discordances are present throughout the fill a critical distinguishing feature of allogenic onlap is the greater lateral persistence of the discordance surfaces defined by subaerial erosional truncation and fluvial onlap do not have geomorphic equivalence because channel processes continually modify the surface as the stratigraphic horizons are forming hence they are strongly time transgressive last the stacking arrangement of the preserved bounded strata is found to be a good time averaged representation of the mass balance history

double seismic zone beneath the mariana island arc a double zone of seismicity has been found beneath the northern marianas in the depth range 80 120 km the benioff zone undergoes a pronounced bend with radius of curvature about 200 km before straightening and descending nearly vertically to a depth of more than 600 km thus this is an ideal area in which to search for evidence of stresses associated with unbending of the subducted oceanic plate we relocated all teleseismic events from 1963 through 1975 by using a regional composite master event technique which significantly decreased the scatter of the hypocenters the three events of the lower seismic zone are separated from the upper zone by about 30 35 km the true thickness of the upper seismic zone is probably 20 km or less the limited focal mechanism data indicate that there is downdip tension in the lower zone and downdip compression in the upper zone the seismicity patterns could be generated either by thermal stresses or by unbending a plate which was originally deformed anelastically we show that an elastic perfectly plastic model of the rheology of the plate can account for the separation of the two seismic zones the focal mechanisms and the greater activity of the upper seismic zone

calibrating discharge bed friction and datum bias in hydraulic models using water level and surface current observations 1 we show that observations of water surface elevation surface velocity and bathymetry can be used to calibrate multiple reach scale parameters such as the discharge the overall bed friction and a water surface datum bias in a hydraulic model fastmech for the depth averaged flow in the braided reach of the kootenai river near bonners ferry id remotely sensed surface velocity data acquired during a 2010 field experiment are converted to depth averaged velocity using a uniform ratio of 0 79 computed from concurrent in situ observation of vertical profiles of velocity the in situ measured discharge of the kootenai river was approximately 220 m3 s for given discharge forcing and downstream boundary condition provided by the measured water surface elevation the fastmech model was used to predict the horizontal variation of the depth averaged velocity and the water surface elevation over the braided reach the calibration considered here consists of varying the discharge the bed friction coefficient and the water surface datum offset to find the combination that minimizes error metrics based on the streamwise profiles of the measured water level and maximum depth averaged velocity composite error metrics that combine water level and velocity measurements are found to be more sensitive with respect to variation of the datum bias and the bed friction we find that a composite error based on the total head is minimized for a discharge of 220 m3 s friction coefficient of 0 005 and a datum offset of 40 cm

fluvio deltaic avulsions during relative sea level fall understanding river response to changes in relative sea level rsl is essential for predicting fluvial stratigraphy and source to sink dynamics recent theoretical work has suggested that rivers can remain aggradational during rsl fall but field data are needed to verify this response and investigate sediment deposition processes we show with field work and modeling that fluvio deltaic systems can remain aggradational or at grade during rsl fall leading to superelevation and continuation of delta lobe avulsions the field site is the goose river newfoundland labrador canada which has experienced steady rsl fall of around 3 4 mm yr 1 in the past 5 k y from post glacial isostatic rebound elevation analysis and optically stimulated luminescence dating suggest that the goose river avulsed and deposited three delta lobes during rsl fall simulation results from delft3d software show that if the characteristic fluvial response time is longer than the duration of rsl fall then fluvial systems remain aggradational or at grade and continue to avulse during rsl fall due to superelevation intriguingly we find that avulsions become more frequent at faster rates of rsl fall provided the system response time remains longer than the duration of rsl fall this work suggests that rsl fall rate may influence the architecture of falling stage or forced regression deposits by controlling the number of deposited delta lobes

the refinement of hypocenter parameters on the basis of three dimensional velocity models of focal zones abstract a complex approach to the processing of seismological data to determine hypocenter coordinates and to construct three dimensional velocity fields of focal zones is considered the iterative process includes the determination of focal coordinates under the assumption of a laterally homogeneous medium the construction of a three dimensional velocity model and subsequent redefinition of the focal coordinates taking into account the inhomogeneous structure of the medium the principal results of calculations of three dimensional velocity fields and refined earthquake hypocenters are presented for focal zones in vrancea carpathians the caucasus and kamchatka

waterborne gpr survey for estimating bottom sediment variability a survey on the po river turin italy we conducted an integrated geophysical survey on a stretchoftheriverpoinordertocheckthegprabilitytodiscriminate the variability of riverbed sediments through an analysis of the bottom reflection amplitudes we conducted continuousprofileswitha200 mhzgprsystemandahandheld broadband em sensor aconductivity meter and a tdr provided punctual measurements of water conductivity permittivity andtemperature theprocessingandinterpretation ofthegem 2andgprdatawereenhancedbyreciprocalresults and by integration with the punctual measurements of the em properties of the water we used a processing flow thatimprovedtheradargramimagesandpreservedtheamplitude ratios among the different profiles and the frequency content at the bottom reflection signal we derived the water attenuationcoefficientbothfromthepunctualmeasurements using the maxwell formulas and from the interpretation of the gpr data finding an optimal matching between the two values the gpr measurements provided maps of the bathymetry and of the bottom reflection amplitude the high reflectivity of the riverbed derived from the gpr interpretation agreed with the results of the direct sampling campaign that followed the geophysical survey the variability of the bottom reflection amplitudesmap whichwasnotconfirmed by the direct sampling could also have been caused by scatteringphenomenaduetotheriverbedclastswhicharedimensionallycomparabletothewavelengthoftheradarpulse

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

sediment and hydrological response to vegetation recovery following wildfire on hillslopes and the hollow of a small watershed summary wildfire can cause dynamically spatial and temporal variations of hydrology and sedimentation from forested environments the largest wildfire historically recorded in south korea burned 23 484 ha of forest land in april 2000 in 2001 systems to monitor post fire runoff and sediment were installed at the outlet of a small watershed and at seven plots on hillslopes of different vegetation condition the hillslope and catchment responses were monitored for five years post fire the watershed was divided into four sites including terrace sodding ts pine planting and fast recovery pf pine planting and slow recovery ps and hollow h according to treatment methods and topographical characteristic the ts site showed the fastest vegetation recovery among the sites and the greatest reduction of soil erosion with time elapsed after wildfire sediment yield from the watershed as well as from plots depended strongly on rainfall erosivity index while the runoff coefficient showed the highest correlation with rainfall amount the sediment response rate had the strongest correlation with a vegetation index characterizing vegetation structure litter and root the hollow mostly acted as a depositional zone but only contributed to erosion when it was disturbed by the treatment applications following the fire or during heavy rain following landslide activity in the catchment these results indicate that gently sloping hollow areas with rapidly recovering vegetation have the potential to reduce the flood and sediment risk however heavy and extreme rainfall events during the study produced excessive sediment by catastrophic debris flow and landslide processes even on vegetated hillslopes the study suggests that the boundary condition for whether i rain is heavy or extreme ii surface condition is bare and iii terrain has a deposition zone should be considered in order to evaluate sediment yields from burnt catchments

storage thresholds for relative sea level signals in the stratigraphic record the tug of relative sea level rsl set by climate and tectonics is widely viewed as the most important boundary condition for the evolution of deltas however the range of amplitudes and periodicities of rsl cycles stored in deltaic stratigraphy remains unknown experimental results presented here suggest that extraction of rsl cycles from the physical stratigraphic record requires their magnitudes and periodicities to be greater than the spatial and temporal scales of the internal autogenic dynamics of deltas these results predict stratigraphic storage of information pertaining to rsl cycles during icehouse earth conditions however these thresholds commonly overlap with the magnitudes and periodicities of rsl cycles for major river deltas during greenhouse earth conditions suggesting stratigraphic signal shredding this theory suggests quantitative limits on the range of paleo rsl information that can be extracted from stratigraphy which could aid the prediction of deltaic response to climate change

estimation of bathymetry and discharge in natural river cross sections by using an entropy approach summary this paper presents a new method for reconstructing the bathymetric profile of a cross section based on the application of the principle of maximum entropy and proposes a procedure for its parameterization the method can be used to characterize the bathymetry of a cross section based on a reduced amount of data exclusively of a geometric type namely the elevation of the lowest point of the channel cross section the observed georeferenced flow widths and the corresponding water levels measured during the events the procedure was parameterized and applied on two actual river cross sections characterized by different shapes and sizes in both cases the procedure enabled us to describe the real bathymetry of the cross sections with reasonable precision and to obtain an accurate estimate of the flow areas with reference to the same two cases we show finally that combining the bathymetry reconstruction method proposed here and an entropy based approach for estimating the cross sectional mean velocity previously proposed farina et al 2014 enables a good estimate of discharge

hydraulics and erosion in eroding rills rills often act as sediment sources and the dominant sediment and water transport mechanism for hillslopes six experiments were conducted on two soils and a uniform sand using three experimental methodologies the results of this study challenge the assumption often used in hydrologic and erosion models that relationships derived for sheet flow or larger channel flow are applicable to actively eroding rills velocity did not vary with slope and reynolds number was not a consistent predictor of hydraulic friction this result was due to interactions of slope gradient flow rate erosion and the formation of rill roughness bed structures and head cuts a relationship for rill flow velocities was proposed stream power was found to be a consistent and appropriate predictor for unit sediment load for the entire data set while other hydraulic variables were not the data for stream power and sediment load fit the form of a logistic curve r2 0 93 which is promising relative to recently proposed erosion models which are based on probabilistic particle threshold theory

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

mineralogy geochemistry and petrogenesis of kurile island arc basalts whole rock major and trace element and mineral chemical data are presented for basaltic rocks from the main evolutionary stages of the kurile island arc nw pacific an outer inactive arc contains a cretaceous lower tertiary sequence of tholeiitic calcalkaline and shoshonitic basalts the main arc miocene quaternary is dominated by weakly tholeiitic with lesser alkalic basalts the mineralogy of kuriles basalts is characterised by an rich plagioclases a continuous transition from chromites to titanomagnetites pyroxenes with low fe3 contents and without strong fe enrichment abundance of groundmass pigeonites and the absence of amphiboles there is an increase in k2o contents both along arc northwards and towards the reararc side the basalts show an exceptionally wide but continuous range of k2o contents 0 1 4 7 which correlate with other lil element contents tholeiitic basalts with low lil element contents la yb and th u but high k rb p2o5 la and zr nb were derived from depleted lherzolitic mantle which had suffered fluid metasomatism by k rb cs sr ba pb and h2o only alkali basalts are also thought to be derived from depleted mantle but melt metasomatism involved addition of all lil elements to a garnet lherzolite mantle the kuriles basalts and their mantle sources range continuously between these two end member compositions the metasomatic fluids melts were probably released by early dehydration and later melting within subducted oceanic lithosphere though the process is not adequately constrained

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

stereo imaging lspiv si lspiv for 3d water surface reconstruction and discharge measurement in mountain river flows abstract large scale particle image velocimetry lspiv has been successfully applied for stream flow and flood measurements in most lspiv studies the water surface has been approximated as a two dimensional planar surface errors may arise due to this approximation for flows in steep channels and with complex riverbed topography especially for small mountain rivers in this study a stereo imaging based lspiv system si lspiv is developed to reconstruct the three dimensional topography and water surface distribution in addition to surface velocity measurements the si lspiv system consists of two synchronized raspberry pi camera modules that can capture stereo images autonomously uncalibrated rectification and point cloud methods are implemented for surface reconstruction detailed three dimensional surface topography as well as water level distribution can be obtained which facilitates image ortho rectification and wetted area delineation for lspiv calculation over the past years an unattended si lspiv system has been deployed in longxi river sichuan china one major flow event was captured and the results were presented to demonstrate that lspiv analysis aided with three dimensional water surface distribution can improve velocity measurement and stream discharge estimation for torrential mountain river flows

scaling the response of deltas to relative sea level cycles by autogenic space and time scales a laboratory study abstract relative sea level rsl change influences surface processes and stratigraphic architecture of deltaic systems and has been studied extensively for decades however we still lack a quantitative framework to define how the magnitude and period of a rsl cycle influences deltaic morphodynamics and the resulting stratigraphy one method for scaling the magnitude and period of rsl cycles is through comparison with the autogenic time and space scales that characterize individual deltaic systems we explore this method using a suite of physical experiments that shared identical forcing conditions with the exception of sea level this approach utilizes two nondimensional numbers that characterize the magnitude and period of rsl cycles magnitude is defined with respect to the maximum autogenic channel depth while the period is defined with respect to the time required to deposit one channel depth of sediment on average everywhere in a basin the experiments include 1 a control experiment lacking rsl cycles used to define autogenic scales 2 a low magnitude long period lmlp stage and 3 a high magnitude short period hmsp stage we observe clear differences in the response of deltas to the forcing in each experiment the rsl cycles in the hmsp stage induce allogenic surface processes and stratigraphic products with scales that exceed the stochastic variability found in the control stage these include the generation of rough shorelines and long temporal gaps in the stratigraphy in contrast the imprint of lmlp cycles on surface processes and stratigraphy is found in properties that define the mean state of a system these include the mean shoreline location and the timing and location of mass extraction from the transport system this work demonstrates the effectiveness of defining the magnitude and period of rsl cycles through autogenic scales and provides insights for generation of forward stratigraphic models influenced by rsl change

relationship between discharge velocity and flow area for rills eroding loose non layered materials a relationship between discharge flow velocity and flow area in rills is established using data from four field and laboratory studies the proposed relationship is shown to predict successfully flow velocities measured in six other studies although slopes range from 0 035 to 0 45 and soil materials range from stony sands over silt loams to vertisols mean flow velocity can be well predicted from discharge alone thus there is no important influence of slope and or soil material characteristics on flow velocities in rills the proposed relationship may be used to improve performance of deterministic flow routing models when applied to rilled catchments furthermore it allows the calculation of unit stream power which has been shown to be related to the transporting capacity of overland flow in terms of slope and discharge

hydraulics of interrill overland flow on rough bare soil surfaces a set of laboratory experiments on bare rough soil surfaces was carried out to study the relationship between soil surface roughness and its hydraulic resistance existing models relating roughness coefficients to a measure of surface roughness didnotpredictthehydraulicresistancewellforthesesurfaces therefore anewmodelisdevelopedtopredictthehydraulic resistanceofthesurface basedondetailedsurfaceroughnessdata roughnessprofilesperpendiculartotheflowareusedto calculatethewetcross sectionalareaandhydraulicradiusgivenacertainwaterlevel thealgorithmofsavatisthenapplied tocalculatethehydraulicresistance thevaluefortheequivalentroughness whichisusedinthealgorithmofsavat couldbe predictedfromtheroughnessprofiles here thetortuosityofthesubmergedpartofthesurfacewasused whichmeansthat thecalculatedroughnessdependsonflowdepth theroughnessincreasedwithdischarge duetothefactthatrougherpartsof the surface became submerged at higher discharges therefore a single measure of surface roughness e g random roughness isnotsufficienttopredictthehydraulicresistance theproposedmodelallowstheextensionoftheflowoverthe surfacewithincreasingdischargetobetakenintoaccount aswellastheroughnesswithinthesubmergedpartofthesurface therefore themodelisabletopredictflowvelocitiesreasonablywellfromdischargeandroughnessdataonly copyright 2000 john wiley sons ltd

fluvial responses to climate and sea level change a review and look forward summary fluvial landforms and deposits provide one of the most readily studied quaternary continental records and alluvial strata represent an important component in most ancient continental interior and continental margin successions moreover studies of the long term dynamics of fluvial systems and their responses to external or allogenic controls can play important roles in research concerning both global change and sequence stratigraphy as well as in studies of the dynamic interactions between tectonic activity and surface processes these themes were energized in the final decades of the twentieth century and may become increasingly important in the first decades of this millennium this review paper provides a historical perspective on the development of ideas in the fields of geomorphology quaternary geology vs sedimentary geology and then summarizes key processes that operate to produce alluvial stratigraphic records over time scales of 103 106 years of particular interest are changes in discharge regimes sediment supply and sediment storage en route from source terrains to sedimentary basins as well as changes in sea level and the concept of accommodation late quaternary stratigraphic records from the loire france mississippi usa colorado texas usa and rhine meuse the netherlands rivers are used to illustrate the influences of climate change on continental interior rivers as well as the influence of interacting climate and sea level change on continental margin systems the paper concludes with a look forward to a bright future for studies of fluvial response to climate and sea level change at present empirical field based research on fluvial response to climate and sea level change lags behind a the global change community s understanding of the magnitude and frequency of climate and sea level change b the sequence stratigraphic community s desire to interpret climate and especially sea level change as forcing mechanisms and c the modelling community s ability to generate numerical and physical models of surface processes and their stratigraphic results a major challenge for the future is to catch up which will require the development of more detailed and sophisticated quaternary stratigraphic sedimentological and geochronological frameworks in a variety of continental interior and continental margin settings there is a particular need for studies that seek to document fluvial responses to allogenic forcing over both shorter 102 103 years and longer 104 106 years time scales than has commonly been the case to date as well as in larger river systems from source to sink studies of quaternary systems in depositional basin settings are especially critical because they can provide realistic analogues for interpretation of the pre quaternary rock record

remote determination of the velocity index and mean streamwise velocity profiles when determining volumetric discharge from surface measurements of currents in a river or open channel the velocity index is typically used to convert surface velocities to depth averaged velocities the velocity index is given by k ub usurf where ub is the depth averaged velocity and usurf is the local surface velocity the usgs united states geological survey standard value for this coefficient k 0 85 was determined from a series of laboratory experiments and has been widely used in the field and in laboratory measurements of volumetric discharge despite evidence that the velocity index is site specific numerous studies have documented that the velocity index varies with reynolds number flow depth relative bed roughness and with the presence of secondary flows a remote method of determining depth averaged velocity and hence the velocity index is developed here the technique leverages the findings of johnson and cowen 2017 and permits remote determination of the velocity power law exponent thereby enabling remote prediction of the vertical structure of the mean streamwise velocity the depth averaged velocity and the velocity index

no evidence from the eastern mediterranean for a mis 5e double peak sea level highstand to understand past and future sea level variability it is important to know if during an interglacial the eustatic sea level is constant or oscillates by several meters around an average value several field sites within and outside the tropics have been interpreted to suggest such oscillations during marine oxygen isotope stage mis 5e 129 116 ka here we present our analysis of one such non tropical site hergla where a facies succession indicates two foreshore deposits above each other previously interpreted as mis 5e sea level highstand amplified by a second rise our study based on field microfacies and optical age bayesian statistics shows a sea level rise forming the upper foreshore strata that coincided with the global sea level rise of the mis 5a interstadial the site does therefore not provide evidence for the mis 5e double peak we conclude from our analysis that the facies based proxy is insensitive to small scale sea level oscillation likewise uncertainties associated with age estimates are too large to robustly infer a short term sea level change

astronomical forcing of middle permian terrestrial climate recorded in a large paleolake in northwestern china abstract geological records of milankovitch cycles provide a temporal framework for reconstructing earth climate evolution and mapping out the history of the ancient solar system understanding the fundamental celestial mechanics driving astronomical rhythms during the permian period from stratigraphic record is challenging because of the inherent limitations of astronomical solutions the chaotic nature of solar system motion and the paucity of cyclostratigraphic studies of geological records the junggar and adjacent basins of northwestern china constituted a large tectonic lake in the middle permian which deposited one of the thickest and richest petroleum source rock intervals in the world constructing an accurate timescale for the permian junggar basin is critical to understand the processes that controlled organic carbon burial as well as paleoclimatic and paleoenvironmental background conditions in this study detailed spectral analyses of natural gamma ray ngr data were performed on the lacustrine muddy dominated lucaogou formation from five exploitation wells the results reveal significant meter scale sedimentary cycles of 37 8 m 10 7 10 m 3 85 3 2 m and 2 0 1 58 m reflecting oscillations in lithologies variations in changing clay content within the mudstone sandstone and dolomite these cycle wavelength ratios match well with those of the milankovitch cycles predicted for middle permian period the depositional duration of the lucaogou formation was estimated at 3 myr correlation of the 1 2 myr obliquity modulation cycles among the ngr logs sedimentation rates and lake levels of the junggar basin as well as with the middle permian global sea level suggests that long term astronomical grand cycles tightly forced climatic and sedimentary processes throughout the lucaogou formation according to two independent approaches we reconstruct middle permian astronomical parameters earth precession constant k and fundamental frequencies terms gi i 1 2 3 4 5 and calculate astronomical periods eccentricity obliquity and precession these results document astronomical forcing of paleozoic lake systems constrain earth moon orbital evolution and refine the fundamental astronomical frequencies of the solar system during the middle permian

impact of glacial lake paleofloods on valley development since glacial termination ii a conundrum of hydrology and scale for the lowstand brahmaputra jamuna paleovalley system

high resolution sequence stratigraphy and implications for cretaceous glacioeustasy of the late cretaceous gallup system new mexico u s a

crustal seismicity in the andean precordillera of argentina using seismic broadband data abstract in this study we analyze 100 crustal precordilleran earthquakes recorded in 2008 and 2009 by 52 broadband seismic stations from the siembra and esp two temporary experiments deployed in the pampean flat slab region between the andean cordillera and the sierras pampeanas in the argentine andean backarc region in order to determine more accurate hypocenters focal mechanisms and regional stress orientations we relocated 100 earthquakes using the jhd technique and a local velocity model the focal depths of our relocated events vary between 6 and 50 km we estimated local magnitudes between 0 4 ml 5 3 and moment magnitudes between 1 3 mw 5 3 focal mechanisms were determined from new hypocenter relocations and first motion p wave polarities our solutions exhibit a majority of the earthquakes with reverse faulting mechanism regional stress tensor from the inversion of p and t axis orientations shows a maximum stress axis 1 almost horizontal with a strike of 85 and a minimum stress axis 3 almost vertical we correlate this small to moderate magnitude seismicity with the presence of large basement structures beneath the iglesia calingasta basin in the west and the eastern precordillera in the east the nucleation of deep earthquakes beneath the iglesia basin could be related to the presence of a major ramp accommodating the crustal shortening between the frontal cordillera and the precordillera the crustal seismicity beneath the precordillera seems to correlate with west dipping structures rooting deep into the cuyania basement suggesting a thick skinned basement deformation system beneath the precordillera and its shallow thin skinned fold and thrust belt

flume experimental evaluation of the effect of rill flow path tortuosity on rill roughness based on the manning strickler equation abstract numerous soil erosion models compute concentrated flow hydraulics based on the manning strickler equation v kst r2 3 i1 2 even though the range of the application on rill flow is unclear unconfined rill morphologies generate local friction effects and consequently spatially variable rill roughness which is in conflict with the assumptions of sectional uniform channel flow and constant channel roughness of the manning strickler equation the objective of this study is to evaluate the effect of rill morphology on roughness and hence to assess the manning strickler roughness coefficient kst by rill morphological data a laboratory experiment was set up to analyse rill hydraulics and roughness of i free developed rill fdr flows and ii straight constrained rill scr flows in the flume the flume experiment generated manning strickler roughness coefficients kst between 22 m1 3 s 1 and 44 m1 3 s 1 reflecting a potential area of the roughness parameter uncertainty it was found that fdr experiments generated significantly lower kst values compared to scr experiments because skin and local friction effects in the fdr experiments were more efficient reducing flow velocity probably due to higher energy dissipation rill flow path tortuosity tort was used to describe the rill morphology of the experiments and correlation statistics between tort and kst identified considerable explanatory capacity of rill flow path tortuosity on rill roughness the flume study demonstrated that a regression model between tort and kst can be used to assess local friction effects of unconfined rill morphologies and hence to reduce the area of uncertainty of the manning strickler roughness parameter

remotely sensed river surface features compared with modeling and in situ measurements 1 images of river surface features that reflect the bathymetry and flow in the river have been obtained using remote sensing at microwave visible and infrared frequencies the experiments were conducted at jetty island near the mouth of the snohomish river at everett washington where complex tidal flow occurs over a varied bathymetry which was measured as part of these experiments an x band 9 36 ghz doppler radar was operated from the river bank and produced images of normalized radar cross sections and radial surface velocities every 20 min over many tidal cycles the visible and infrared instruments were flown in an airplane all of these techniques showed surface evidence of frontal features flow over a sill and flow conditioned by a deep hole these features were modeled numerically and the model results correspond well to the remote observations in situ measurements made near the hole showed that changes in measured velocities correlate well with the occurrence of the features in the images in addition to tidal phase the occurrence of these features in the imagery depends on tidal range the surface roughness observed in the imagery appears to be generated by the bathymetry and flow themselves rather than by the modulation of wind waves

estimating manning s n for steep slopes abstract hydrological and soil erosion models require calculations of flow velocity for which either the darcy weisbach or the manning equation is generally used a series of field experiments was carried out in a small catchment on the chinese loess plateau to obtain reliable values of manning s n the soils are typically erodible loess soils the experiments were conducted for a range of land uses as well as for different slope angles 6 64 measurements were performed on a 2 5 0 4 m plot on which flow was allowed to find its own path water was evenly applied to the top of the plot and discharge surface velocity flow width and slope were measured the results show that manning s n can just like darcy weisbach f be estimated from reynolds number furthermore for croplands there is an apparent linear increase in manning s n and f with increasing slope angle r2 0 70 as manning s n is usually assumed to be constant this must mean that either velocity increases with slope or hydraulic radius decreases the measurements showed virtually no increase in velocity and a minor increase in hydraulic radius with slope as flow was more concentrated on steeper slopes possible explanations for this lack of increase in velocity include increased roughness water resour res 37 2001 791 decreased effective slope angle because of the development of vertical head cuts and a shift in energy use all three hypotheses only apply to situations involving erosion the trend of manning s n with slope implies that in soil erosion models using manning s equation or darcy weisbach the value of n or f should be a function of the slope for erodible soils for non erodible soil as in woodland no increase in manning s n with slope was observed

the distribution of sediment residence times at the foot of mountains and its implications for proxies recorded in sedimentary basins abstract the geochemical and physical properties of terrigenous sediment stacked in sedimentary basins are used as proxies for the paleo environmental conditions that prevailed during their period of deposition nevertheless sediment grains have a stochastic transit from mountain sources to sedimentary basins a fraction of grains are stored for a long time while others are recycled from old deposits consequently the temporal representativity of a population of grains in a sedimentary stratum is uncertain the potential recycling of old material is a major concern in the reconstruction of paleo environments and this recycling is usually difficult to evaluate in particular the distribution of grain residence times in basins between sources and sinks is out of reach here we use a landscape evolution model that traces grains to analyse the distribution of residence times in an alluvial apron at the foot of a mountain relief we study an end member scenario that is the least favourable for the storage of grains when the mountain is eroding at the same rate as rock is uplifting in this case the alluvial apron behaves as a by pass zone when averaging sediment flux over ma and the storage of grains of any size should be minimal yet the model predicts that some grains are stored for hundreds of thousands of years before exiting the alluvial apron consequently the mean residence time of sediment grains is much higher than the observed residence time of 95 of the grains exported by the alluvial apron rivers this process may explain very long residence times found in fluvial systems by geochemical methods based on bulk measurements of sediment furthermore it suggests that grains stored for a very long time although a minority can bias time dependent proxies