laboratory simulation of clast abrasion brewer paul lewin j 2002 laboratory simulation of clast abrasion earth surface processes and landforms 27 pp 145 164 rae2008

surface based transport model for mixed size sediment we present a transport model for mixed sand gravel sediments fractional transport rates are referenced to the size distribution of the bed surface rather than subsurface making the model completely explicit and capable of predicting transient conditions the model is developed using a new data set of 48 coupled observations of flow transport and bed surface grain size using five different sediments the model incorporates a hiding function that resolves discrepancies observed among earlier hiding functions the model uses the full size distribution of the bed surface including sand and incorporates a nonlinear effect of sand content on gravel transport rate not included in previous models the model shares some common elements with two previous surface based transport models but differs in using the full surface size distribution and in that it is directly developed from a relatively comprehensive data set with unambiguous measurement of surface grain size over a range of flow transport rate and sediments

a transferable method for the automated grain sizing of river gravels 1 the spatial and temporal resolution of surface grain size characterization is constrained by the limitations of traditional measurement techniques in this paper we present an extremely rapid image processing based procedure for the measurement of exposed fluvial gravels and other coarse grained sediments defining the steps required to minimize the errors in the derived grain size distribution this procedure differs significantly from those used previously it is based around a robust object detection algorithm that produces excellent results on images exhibiting a wide range of sedimentary conditions crucially without any user intervention or site specific parameterization the procedure is tested using a data set comprising 39 images from three rivers with contrasting grain lithology shape roundness and packing configuration and representing a very wide range of textures it is shown to perform more consistently than the best existing automated method achieving a precision equivalent to that obtainable by wolman sampling but taking between one sixth and one twentieth of the time the error in area by number grain size distribution percentiles is typically less than 0 05

compaction permeability evolution and stress path effects in unconsolidated sand and weakly consolidated sandstone abstract the influence of stress paths on the mechanical behavior and coupled permeability evolution of quartz sand packings and soft sandstone have been investigated the proposed approach is mainly based on the performing drained compression tests keeping constant a stress path parameter k defined as the ratio of the horizontal to vertical effective stress increments macroscopic mechanical data and the stress path dependency of permeability have been measured in the elastic brittle and compaction regimes the micro structural characteristics of unconsolidated materials coarse rounded grains glass beads gb and angular grains durance sand ds and a weakly consolidated sandstone otter sherwood sandstone oss have been quantified in intact and deformed states combining petrophysical core analysis and multi scale imaging according to the feasibility of sub sampling of the different materials two different types of hydro mechanical behavior were evidenced for each material the weakly consolidated oss presents a mechanical behavior similar to the consolidated rocks with two distinct regimes of deformation the transition between these two regimes is a function of the stress path on the other hand the sand shows a gradual transition regime requiring the use of a curvature criterion to pick yield stresses this criterion has been validated on the basis of acoustic emissions analysis the modified cam clay model and the elliptical cap model allow capturing efficiently the yield envelopes the permeability measurements were performed with intermediate pressure ports to measure accurately the high permeable sand and to avoid end effects for oss permeability evolutions follow closely the volumetric strain evolutions in both the elastic and plastic regimes and are mainly controlled by the mean pressure before yield at these critical stresses the permeability drops drastically under the influence of deviatoric stress conversely for ds the correlation between strain and permeability is not obvious as permeability reduction is pronounced at an early stage of loading

sampling surficial fluvial gravels the precision of size distribution percentile sediments abstract grid by number wolman sampling is commonly used to characterize the texture of surficial fluvial sediments assessments of sampling precision have concentrated on the median grain size but adequate representation of other grain size percentiles is paramount in a number of sedimentological contexts the field effort required to construct percentile sampling distributions by replication is prohibitive and the absence of any general size distribution for fluvial sediments precludes theoretical calculation of percentile standard errors bootstrapping is used in this paper to determine percentile standard errors for large samples from two gravel bar surfaces the improvement of percentile precision with sample size follows the theoretical expectation hence improvement in percentile recision is achieved only at the expense of much greater sampling effort once sample sizes reach about 400 stones however absolute percentile standard errors differ significantly from theoretically derived values of particular interest is the stability of coarser percentile estimates in coarse skewed distributions d95 estimates may be as precise as d50 estimates for a given sample size the sensitivity of the precision of estimated percentiles to distribution shape is examined using synthetic skewed and bimodal grain size distributions the absolute precision of percentile estimates is shown to vary with the grain size distribution of a particular sediment our field results provide a reference for further work

bed material texture in low order streams on the queen charlotte islands british columbia low order channels comprise a large proportion of the links of every drainage basin and are often at the centre of land management concerns they exhibit hydrological and geomorphological characteristics atypical of higher order links this paper examines the nature and causes of variations in the bed material texture of two streams on the queen charlotte islands british columbia the extant functional exponential model is found to be inadequate for explaining observed changes in grain size parameters with distance downstream recurrent disruption of sediment transport by large organic debris jams and the sporadic contamination of the fluvial sediment population by colluvial inputs preclude the development of longitudinal structure rather grain size varies erratically over short distances a stochastic model best describes the observed variations and should be adopted as an alternative to the exponential model in low order links characteristic variances are controlled by the degree of hillslope channel coupling and the extent and characteristics of non alluvial storage mechanisms

seismological and sar signature of unrest at nisyros caldera greece abstract nisyros island a quaternary volcanic center located at the se of the aegean volcanic arc has been in the past characterized by periods of intense seismic activity accompanied sometimes by hydrothermal explosions the last one being in 1887 the recent long lasting episode of unrest 1995 1998 in the area is the first instrumentally documented providing information on the behavior of the volcano evidence from seismicity and sar interferometry suggests that the presently active part of the kos nisyros volcano tectonic complex is located at the nw coast of nisyros island defining an area much smaller than the whole volcano tectonic area seismicity patterns vary both temporally and spatially consistently with different rates of vertical ground deformation inferred from sar interferometry these observations help us to discuss the different elements controlling the behavior of the volcanic system such as the existence location and timing of magma chamber inflation the occurrence of tensile failure at the boundaries of the chamber and the possibility of magmatic fluids being expelled to form a shallow magmatic intrusion the seismic failure and migration of hypocenters indicating shallow magma transport

sediment transport along lower fraser river 1 measurements and hydraulic computations a comprehensive program of sediment transport measurements was conducted along lower fraser river british columbia between 1966 and 1986 the data yield a detailed sediment budget annual total suspended loads at three stations are virtually identical averaging 17 106 tonnes year t yr 1 the suspended sand load is about 5 5 106 t yr 1 about one third of the total in the gravel bed reach of the river the sand behaves as wash load significant transport of gravel begins at agassiz at a discharge of about 5000 m3 s 1 the annual gravel transport was estimated to be about 0 23 106 t yr 1 only 1 of the total load all of this material is deposited in the reach upstream of mission at mission sands finer than 0 177 mm make up more than 50 of the suspended sand load but are virtually absent from the sand bed therefore a portion of the sand load at mission is wash load the total bed material load here was estimated to be 3 0 106 t yr 1 about 18 of the total sediment load virtually all of the bed material load was transported in intermittent suspension near the bed less than 5 occurring as bed load in the long term the suspended sand load upstream is approximately equal to the total sand load at mission however within individual years some of the sand is stored within the reach temporarily and then reentrained later

using uas optical imagery and sfm photogrammetry to characterize the surface grain size of gravel bars in a braided river veneon river french alps this paper explores the potential of unmanned aerial system uas optical aerial imagery to characterize grain roughness and size distribution in a braided gravel bed river veneon river french alps with this aim in view a wolman field campaign 19 samples and five uas surveys were conducted over the veneon braided channel during summer 2015 the uas consisted of a small quadcopter carrying a gopro camera structure from motion sfm photogrammetry was used to extract dense and accurate three dimensional point clouds roughness descriptors roughness heights standard deviation of elevation were computed from the sfm point clouds and were correlated with the median grain size of the wolman samples a strong relationship was found between uas sfm derived grain roughness and wolman grain size the procedure employed has potential for the rapid and continuous characterization of grain size distribution in exposed bars of gravel bed rivers the workflow described in this paper has been successfully used to produce spatially continuous grain size information on exposed gravel bars and to explore textural changes following flow events c 2017 elsevier b v all rights reserved

stabilizing self organized structures in gravel bed stream channels field and experimental observations stable reticulate structures which we call stone cells have been observed in cobble gravel channel beds with low bed material transport rates experiments show that such structures develop simultaneously with the armor layer during an extended period when flows do not exceed the shields threshold by more than 2 times so that bed material transport is low they are constructed by particles moving from less stable positions into more stable configurations against each other intermediate developments include clusters and stone lines they reduce sediment transport by orders of magnitude and are evidently a major stability promoting mechanism in gravel channels the timescale for their development suggests that the boundaries of many gravel bed channels are not in equilibrium with recent competent flows but reflect the history of recent dominant flows

field evidence for rapid downstream fining of river gravels through selective transport doubts have been expressed about the ability of either abrasion or sorting to explain strong downstream fining of river gravels we describe pronounced fining over a short distance in a scottish river that has no human disturbance or lateral input of water and sediment measured abrasion rates are far too small to explain observed downstream fining but bed load trap measurements and the dispersion of magnetic tracer pebbles in six subreaches both show sorting during transport the observed downstream fining is also simulated well by a numerical sediment routing model using hydraulic and transport laws consistent with our field measurements the geomorphological cause of the strong fining is slope reduction above a local base level control in this common situation the development of downstream fining is part of the river9s tendency to minimize downstream variation in bed load transport rates and can proceed far more rapidly than the major aggradation otherwise required for equilibration

form and growth of bars in a wandering gravel bed river the changing form of developing alluvial river bars has rarely been studied in the field especially in the context of the fixed compound mainly alternate gravel bars that are the major morphological feature of the wandering style century scale patterns of three dimensional growth and development and the consequent scaling relations of such bars are examined along the gravel bed reach of lower fraser river british columbia canada a retrospective view based on maps and aerial photographs obtained through the twentieth century shows that individual bars have a life history of about 100 years except in certain protected positions a newly formed gravel bar quickly assumes its ultimate thickness and relatively quickly approaches its equilibrium length growth continues mainly by lateral accretion of unit bars consistent with the lateral style of instability of the river bar growth is therefore allometric mature bars approach equilibrium dimensions and volume that scale with the overall size of the channel accordingly the bars conform with several published criteria for the ultimate dimensions of alternate barforms sand bars observed farther downstream have notably different morphology fraser river presents a typical wandering channel planform exhibiting elements of both meandered and low order braided channels hydraulic criteria to which the fraser bars conform illustrate why this planform develops and persists the modest rate of bed material transfer along the channel typical of the wandering type determines a century length time scale for bar development this time scale is consistent with estimates that have been made for change of the macroform elements that determine the overall geometry of alluvial channels copyright 2009 john wiley sons ltd

response of bed surface patchiness to reductions in sediment supply 1 river beds are often arranged into patches of similar grain size and sorting patches can be distinguished into free patches which are zones of sorted material that move freely such as bed load sheets forced patches which are areas of sorting forced by topographic controls and fixed patches of bed material rendered immobile through localized coarsening that remain fairly persistent through time two sets of flume experiments one using bimodal sand rich sediment and the other using unimodal sand free sediment are used to explore how fixed and free patches respond to stepwise reductions in sediment supply at high sediment supply migrating bed load sheets formed even in unimodal sand free sediment yet grain interactions visibly played a central role in their formation in both sets of experiments reductions in supply led to the development of fixed coarse patches which expanded at the expense of finer more mobile patches narrowing the zone of active bed load transport and leading to the eventual disappearance of migrating bed load sheets reductions in sediment supply decreased the migration rate of bed load sheets and increased the spacing between successive sheets one dimensional morphodynamic models of river channel beds generally are not designed to capture the observed variability but should be capable of capturing the time averaged character of the channel when applied to our experiments a 1 d morphodynamic model rte bookagdegnormgravmixpw xls predicted the bed load flux well but overpredicted slope changes and was unable to predict the substantial variability in bed load flux and load grain size because of the migration of mobile patches our results suggest that 1 the distribution of free and fixed patches is primarily a function of sediment supply 2 the dynamics of bed load sheets are primarily scaled by sediment supply 3 channels with reduced sediment supply may inherently be unable to transport sediment uniformly across their width and 4 cross stream variability in shear stress and grain size can produce potentially large errors in width averaged sediment flux calculations

paradox of downstream fining and weathering rind formation in the lower hoh river olympic peninsula washington although downstream fining of clasts is typical in modern and ancient river systems the hoh river a cobble and boulder bed river in washington state contains surprisingly little downstream fining of the coarsest tail of the grain size distribution along its lower 63 km mean rate of fining of the coarsest size fraction is only 0 24 mm km barely significant given uncertainties in measurement in addition these same clasts have weathering rind thicknesses that change very little along the length of the river they decrease by 0 01 mm km because weathering rinds are well developed in this setting and both tumbler studies and field observations show that abrasion of weathering rinds greatly accelerates clast diminution there seems to be a paradox between predicted and observed downstream fining rates field study shows that detritus is constantly being resupplied to the river by erosion of late glacial materials along the river9s cutbanks and tributaries the clasts supplied range in size but include abundant coarse grains with very thick weathering rinds the continuous resupply of grains strongly attenuates the rate of downstream fining despite the fact that these weathered grains abrade relatively rapidly thus the dominance of reworked glacial debris overwhelms any processes by which grains are reduced in size in the modern river these results suggest that relatively infrequent glaciation can have a long lived effect on river sedimentation

mapping sub pixel fluvial grain sizes with hyperspatial imagery this paper presents an investigation of image texture approaches for mapping sub pixel fluvial grain size features from airborne imagery allowing for the rapid acquisition of surface sand and coarse fraction 1 41 mm grain size information imagery at 30 mm resolution was acquired over four gravel bars from the fraser river british columbia canada combined first order and second order image texture approaches windowed standard deviation filter and the grey level co occurrence matrix were used first order image texture through the application of a standard deviation filter and subsequent thresholding was used to detect the presence of surface sand with optimal accuracy achieved at 91 1 9 a wide ranging parameter space investigation was used to derive optimum parameters for the grey level co occurrence matrix subsequently first and second order image textures were used in multiple linear regression to achieve good calibrations with several sub pixel grain size percentiles relative error at 1 44 3 18 6 80 and 10 6 for d5 d16 d35 and d50 respectively the larger percentiles of d84 and d95 had relative errors of 24 7 and 29 7 respectively the breakdown of calibration precision for larger percentiles is attributed to a pixel averaging effect it is concluded that multispectral imagery is not required because sufficient image texture information can be derived from standard colour imagery recommendations are suggested for application of this method to other localities and datasets thus reducing exhaustive parameter searches in future studies

formation of stationary alternate bars in a steep channel with mixed size sediment a flume experiment alternate bars were formed by sediment transport in a flume with froude modelled flow and relative roughness characteristic of gravel boulder channels with steep slopes the flume 0 3 m wide 7 5 m long was filled with a sand gravel mixture which was also fed into the top of the flume at a constant rate under constant discharge channel slope was set at 0 03 initially coarse particles accumulated on incipient bar heads near one side of the flume and diverted flow and bedload transport across the flume toward a pool scoured against the opposite flume wall downstream sorting in the pool directed coarse particles onto the next bar head downstream alternate sequences of pools and coarse bar heads were thereby linked down the entire flume by interactions of sediment sorting flow and channel morphology during episodes of bar construction unsorted bedload invaded interior bar surfaces and was deposited persistent deposition of coarse particles on bar heads prevented downstream migration of bars by inhibiting bar head erosion and bedload transport over bars likely factors leading to bar head stabilization in modelled gravel bed channels are coarse mixed size sediment steep channel gradients and shallow depths

spatial variations in surface sediment structure in riffle pool sequences a preliminary test of the differential sediment entrainment hypothesis dseh riffle pool sequences are maintained through the preferential entrainment of sediment grains from pools rather than riffles this preferential entrainment has been attributed to a reversal in the magnitude of velocity and shear stress under high flows however the differential sediment entrainment hypothesis dseh postulates that differential entrainment can instead result from spatial sedimentological contrasts here we use a novel suite of in situ grain scale field measurements from a riffle pool sequence to parameterise a physically based model of grain entrainment field measurements include pivoting angles lift forces and high resolution dems acquired using terrestrial laser scanning from which particle exposure protrusion and surface roughness were derived the entrainment model results show that grains in pools have a lower critical entrainment shear stress than grains in either pool exits or riffles this is because pool grains have looser packing hence greater exposure and lower pivoting angles conversely riffle and pool exit grains have denser packing lower exposure and higher pivoting angles a cohesive matrix further stabilises pool exit grains the resulting predictions of critical entrainment shear stress for grains in different subunits are compared with spatial patterns of bed shear stress derived from a 2d computational fluid dynamics cfd model of the reach the cfd model predicts that under bankfull conditions pools experience lower shear stresses than riffles and pool exits however the difference in sediment entrainment shear stress is sufficiently large that sediment in pools is still more likely to be entrained than sediment in pool exits or riffles resulting in differential entrainment under bankfull flows significantly this differential entrainment does not require a reversal in flow velocities or shear stress suggesting that sedimentological contrasts alone may be sufficient for the maintenance of riffle pool sequences this finding has implications for the prediction of sediment transport and the morphological evolution of gravel bed rivers

experiments on cauldron formation a polygonal cauldron and ring fractures abstract the sequence of formation of the motojuku type cauldron fujita et al 1970 is summarized as follows 1 doming due to ascent of a magma body 2 development of normal faults which produce a polygonal cauldron and 3 eruption of acidic to intermediate pyroclastic material model experiments on a scale of 1 200 000 reveal that ascent of the magma body which was imitated by a ball of hardened putty produced a polygonal cauldron composed of radial and concentrically arranged short fractures on the roof of a dome no ring fractures were formed this type of cauldron develops near the surface on the other hand emission of magma which was imitated by evaporation of a ball of dry ice in brittle powdered material caused ring faults dipping outward and a circular cauldron without up or downwarping this type of cauldron develops upward from the magma body the former model is equated to the motojuku type cauldron and the latter model to the other types of cauldrons with ring fractures

experimental studies of collapse calderas we present experiments to investigate the formation of calderas using inflatable balloons in a medium of fused alumina powder this system provides a model of a magma chamber in an homogeneous elastic media which scales to volcanic systems in terms of geometry and strength of the media three kinds of experiment were performed i the balloon was inflated and then deflated simulating pre emption tumescence and caldera collapse ii the balloon was deflated without prior inflation simulating caldera formation without pre eruption tumescence iii three balloons were inflated and deflated in a line simulating multiple magma chambers the influence of magma chamber shape was investigated using different shaped balloons balloon inflation formed a dome with a surface pattern of shallow polygonal fractures centrally and radial fractures peripherally uplift occurs along deep inward dipping concentric reverse faults deflation generated depressions with an outer set of concentric ring fractures surrounding a central funnel formed by sagging along numerous minor faults some of which formed during doming during collapse the concentric reverse faults were converted to normal faults and the radial normally faulted fractures were converted to reverse faults without prior tumescence an outer set of near vertical ring faults surround a flat central depression due to collapse of a coherent block an inner set of outward dipping reverse ring faults also develop the experimental caldera area increased with balloon size and increased as the balloon depth decreased for a given balloon volume and depth collapse area is significantly smaller if doming had occurred prior to collapse arcuate fractures can provide the pathways for magma ascent during pre emption tumescence smith bailey 1968 but the shallow radial and polygonal fracture systems may also influence vent location changes in fault geometry and sense of movement extension to compression and vice versa occur when subsidence initiates and can account for changes in vent location that occur in many eruptions multiple overlapping collapse calderas are associated with magma chamber migration whereas nested calderas can result from the activity of a single magma chamber

the 2017 july 20 mw 6 6 bodrum kos earthquake illuminates active faulting in the gulf of gokova sw turkey

downstream patterns of bed material grain size in a large lowland alluvial river subject to low sediment supply 1 a new data set of bimodal subaqueous channel bed sediments was analyzed for longitudinal patterns in grain size it yielded two interesting observations 1 separate fining trends in d50 exist for gravel and fines that overlap for 175 river kilometers and 2 this overlap in fining trends results in a protracted nonabrupt gravel to sand transition these suggest bed patchiness that is interpreted in the context of inherent grain size bimodality localized hydraulic sorting due to spatially heterogeneous and low sediment supply and local deviations in channel gradient the data also show that tributaries have a minor impact on main stem downstream fining due to basin shape and tectonic history in addition subaqueous channel sediments were observed to be finer than nearby sediments collected from exposed bars which may indicate a narrow active zone of transport where bars are disconnected from sediment movement this research has implications for bed material collection and theories of downstream fining

geomorphological effectiveness of floods to rework gravel bars insight from hyperscale topography and hydraulic modelling bars are key morphological units in river systems fashioning the sediment regime and bedload transport processes within a reach reworking of these features underpins channel adjustment at larger scales thereby acting as a key determinant of channel stability despite their importance to channel evolution few investigations have acquired spatially continuous data on bar morphology and sediment size to investigate bar reworking to this end four bars along a 10 km reach of a wandering gravel bed river were surveyed with terrestrial laser scanning tls capturing downstream changes in slope bed material size and channel planform detrended standard deviations z were extracted from tls point clouds and correlated to underlying physically measured median grain size d50 across a greater range of z values than have hitherto been reported the resulting linear regression model was used to create a 1 m resolution median grain size map a fusion of airborne lidar and optical empirical bathymetric mapping was used to develop reach scale digital elevation models dems for rapid two dimensional hydraulic modelling using jflow software the ratio of dimensionless shear stress over critical shear stress was calculated for each raster cell to calculate the effectiveness of a range of flood events 2 33 100 year recurrence intervals to entrain sediment and rework bar units results show that multiple bar forming discharges exist whereby frequent flood flows rework tail and back channel areas whilst much larger less frequent floods are required to mobilise the coarser sediment fraction on bar heads valley confinement is shown to exert a primary influence on patterns of bar reworking historical aerial photography hyperscale dems and hydraulic modelling are used to explain channel adjustment at the reach scale the proportion of the bar comprised of more frequently entrained units tail back channel supra platform relative to more static units bar head exerts a direct influence upon geomorphic sensitivity

discriminating between pore filling load and bed structure load a new porosity based method exemplified for the river rhine sediments contained in the river bed do not necessarily contribute to morphological change the finest part of the sediment mixture often fills the pores between the larger grains and can be removed without causing a drop in bed level the discrimination between pore filling load and bed structure load therefore is of practical importance for morphological predictions in this study a new method is proposed to estimate the cut off grain size that forms the boundary between pore filling load and bed structure load the method evaluates the pore structure of the river bed geometrically only detailed grain size distributions of the river bed are required as input to the method a preliminary validation shows that the calculated porosity and cut off size values agree well with experimental data application of the new cut off size method to the river rhine demonstrates that the estimated cut off size decreases in a downstream direction from about 2 to 0 05 mm covariant with the downstream fining of bed sediments grain size fractions that are pore filling load in the upstream part of the river thus gradually become bed structure load in the downstream part the estimated mass percentage of pore filling load in the river bed ranges from 0 in areas with a unimodal river bed to about 22 in reaches with a bimodal sand gravel bed the estimated bed porosity varies between 0 15 and 0 35 which is considerably less than the often used standard value of 0 40 the predicted cut off size between pore filling load and bed structure load dc p is fundamentally different from the cut off size between wash load and bed material load dc w irrespective of the method used to determine dc p or dc w dc w values are in the order of 10 1 mm and mainly dependent on the flow characteristics whereas dc p values are generally much larger about 100 mm in gravel bed rivers and dependent on the bed composition knowledge of dc w is important for the prediction of the total sediment transport in a river including suspended fines that do not interact with the bed whereas knowledge of dc p helps to improve morphological predictions especially if spatial variations in dc p are taken into account an alternative to using a spatially variable value of dc p in morphological models is to use a spatially variable bed porosity which can also be predicted with the new method in addition to the morphological benefits the new method also has sedimentological applications the possibility to determine quickly whether a sediment mixture is clast supported or matrix supported may help to better understand downstream fining trends sediment entrainment thresholds and variations in hydraulic conductivity

reconstructing a sediment pulse modeling the effect of placer mining on fraser river canada gold mining along 525 km of the fraser river between 1858 and 1909 added an estimated 1 1 108 t of tailings half gravel and the rest finer to the river s natural sediment load we simulate the response using a 1 d multigrain size morphodynamic model since premining conditions are unknown and modern data are insufficient for tuning the process representation we devised a novel modeling strategy which may be useful in other data poor applications we start the model from a smoothed version of the modern longitudinal profile with bed grain size distributions optimized to match alternative assumptions about natural sediment supply and compare runs that include mining with control runs that can be used to quantify the effects of deficiencies in process representation and initialization simulations with an appropriate choice of natural supply rate closely match the best available test data which consist of a detailed 1952 1999 gravel budget for the distal part of the model domain the simulations suggest that the main response to mining was rapid bed fining which allowed a major increase in bed load transport rate with only slight 0 1 m mean aggradation within the mining region and most of the excess sediment exported well beyond the mountain front within the mining period or soon afterward we compare this pattern of response by a large powerful river with previous case studies of river adjustment to sediment supply change

characterisation and multifaceted anisotropy assessment of corvio sandstone for geological co2 storage studies we present a comprehensive characterisation of the physical mineralogical geomechanical geophysical and hydrodynamic properties of corvio sandstone this information together with a detailed assessment of anisotropy is needed to establish corvio sandstone as a useful laboratory rock testing standard for well constrained studies of thermo hydro mechanical chemical coupled phenomena associated with co2 storage practices and for geological reservoir studies in general more than 200 core plugs of corvio sandstone 38 1 and 50 mm diameters 2 1 length to diameter ratio were used in this characterisation study with a rock porosity of 21 7 1 2 dry density 2036 32 kg m 3 and unconfined compressive and tensile strengths of 41 3 28 and 2 3 0 14 mpa respectively geomechanical tests show that the rock behaves elastically between 10 and 18 mpa under unconfined conditions with associated young s modulus and poisson s ratio of 11 8 2 8 gpa and 0 34 0 01 gpa respectively permeability abruptly decreases with confining pressure up to 10 mpa and then stabilises at 1 md ultrasonic p and s wave velocities vary from about 2 8 3 8 km s 1 and 1 5 2 4 km s 1 respectively over confining and differential pressures between 0 1 and 35 mpa allowing derivation of associated dynamic elastic moduli anisotropy was investigated using oriented core plugs for electrical resistivity elastic wave velocity and attenuation permeability and tracer injection tests corvio sandstone shows weak transverse isotropy symmetry axis normal to bedding of 10 for velocity and 20 for attenuation

automatic grain sizing of vertical exposures of gravelly deposits abstract the grain size distribution gsd is a key indicator in stratigraphy and morphology it is a basic tool used by a variety of disciplines geology geomorphology archeology ecology and engineering automatic grain sizing ags has been developed to estimate the gsd of surfaces in a rapid and effortless manner yet the traditional bulk method time consuming and laborious is still in use for the determination of the gsd of coarse grained sedimentary deposits and of the near subsurface of landforms principally river beds the ags technique is examined here in its application to the stratigraphic record and to the subsurface images processed by ags and manual samples of coarse grained deposits in section were compared for evaluation of accuracy and determination of the extent of validation of the ags technique the ags often achieves results very similar to field counting especially when the largest grains are accounted for in the size of the sampling area and when photographs are taken afar without flash best results are provided when two images of the same sediment are taken at close range and also from afar to combine their gsds hence overcoming errors generated by resolution sampling area and grain size the computed errors are larger than those in prior studies yet remain reasonably small even though results are not bias corrected axes exposed in an outcrop very likely differ from those exposed on the surface and sediment properties and lighting conditions vary although results indicate a 25 burial effect the performance of the ags for sections is high unlike prior application of ags for riverbed surface openwork gravels conglomerate sections and the near subsurface include a matrix resulting in a somewhat larger mean irreducible error the technique may be utilized in studies of conglomerate texture allowing the evaluation of entire gsds under difficult sampling conditions an example use of ags to subsurface gsd evaluation is provided among others enabling an easy and fast method to calculate extent of armoring

downstream variation in grain size along an alpine river analysis of controls and processes downstream variation in bed material size was studied along a 115 km reach of the piave river eastern alps italy this river drains a region producing high sediment yields and has a braided pattern along half of its length during the last century the river system has been affected by several human impacts hydroelectric dams diversions gravel mining which have strongly altered flow regime and sediment dynamics the aim of the study is to analyse the changes of bed material size in the downstream direction and to explain these changes in the light of both natural and anthropogenic factors surface material was sampled at 35 sites using the grid by number method the collected data give a detailed picture of the downstream variation in sediment size which is characterised by a complex pattern rather than by a simple decreasing trend an explanation of this variation was found through identification of discontinuities significant steps in the downstream trend and factors which can determine changes in sediment texture both natural lateral sediment sources and anthropogenic factors e g barrages are significant in this river system and they provide an explanation for most of the observed discontinuities seven out of eight discontinuities few tributaries disrupt downstream fining while as expected the barrages produce important changes in sediment texture fining processes were investigated in the lower part of the study reach where the lateral sediment sources and the barrages have minor effects on the bed material exponential models provide acceptable explanations of the downstream variations and give fining coefficients equal to 0 027 and 0 028 km 1 respectively for d50 and d84 evidence suggests that both abrasion and sorting are important in determining the downstream fining observed but it is likely that sorting is the dominant process

morpho sedimentary characteristics of proximal gravel braided river deposits in a froude scaled physical model a froude scaled physical model of a proximal gravel bed braided river was used to connect the river morphological characteristics and sedimentary processes and forms to deposit geometry high resolution continuous three dimensional topographic data was acquired from sequential photogrammetric digital elevation models paired with grain size surface maps derived from image analysis of textural properties of the surface from these data the full three dimensional development of the braided river deposit and grain size sorting patterns was compiled over an experimental time period of 40 hours during which the model river reworked a large portion of the braided channel the minimum surface of the deposit is developed progressively over time by erosion migration and avulsion of channels and by local scour at channel confluences the maximum surface of the deposit is formed by amalgamation of braid bar surfaces and has less overall relief than the minimum surface confluence scour constitutes about 5 of the area of the minimum surface migration of individual confluences is limited to distances of the order of the width and length of the confluence so that confluences do not form laterally extensive deposits and basal surfaces maximum and minimum surfaces have very similar grain size distributions and there is no extensive basal coarse layer deposit maximum thickness is strongly associated with large channel confluences which occur as deeper areas along the main channel belt and make up a large proportion of the thickest portions of the deposit this article is protected by copyright all rights reserved

tectonics of nisyros island greece by field and offshore data and analogue modelling abstract we use new on land and offshore structural data and scaled analogue models to analyse the fault tectonic pattern at nisyros island greece which has an active caldera that shows a complicated network of faults fractures and volcano tectonic structures we measured 157 faults that show dominant dip slip normal motions along planes mainly striking ne sw nne ssw and nnw sse inside the caldera dykes necks and morphometric parameters of volcanic domes explosion craters and fumarole pits indicate the control by ne striking discontinuities on magma and gas paths the nnw and ne striking faults bound a major block that underwent repeated downthrow and uplift movements during the late pleistocene holocene experiments with scaled models of caldera resurgence and two magma chambers indicate the formation of an hourglass shaped fault pattern as seen in plan view with an asymmetric increase in the fault offset and a widening of the fault divergence towards the volcano flank all these data suggest that regional fault tectonics and stress state strongly guided magma upwelling and the emplacement of volcanic centres whereas periodical bulging due to the overpressure of a second magma chamber located northwest of the caldera combined with faulting due to tectonic stresses can account for the overall deformation field

the hydrodynamics of particle clusters and sediment entrapment in coarse alluvial channels particles projecting from the bed of an alluvial channel distort the fluid stream to produce a distinctive pressure field this has considerable significance for both the entrapment and entrainment of other particles and is a primary cause of the widespread occurrence of pebble clusters and boulder shadows lift and drag forces are determined on clustered hemispherical particles of varying size in the wake of an obstructing particle both forces are shown to vary directly with particle separation in a linear fashion on the stoss side of the cluster drag is uniform regardless of the separation of the component particles but lift is shown to increase when particle separation is small so affecting stability this mutual interference of neighbouring clustered bed particles is a vital consideration of incipient motion and is shown by field evidence to cause a wide range in transport stage for particles of similar size and shape on average 46 of clustered particles are entrained by flood flow compared to 87 of particles in open plane beds the influence of clusters is a major determinant of sedimentary sorting

river system discontinuities due to lateral inputs generic styles and controls in alluvial river systems lateral inputs of water and or sediment at junctions or undercut hillsides can disrupt what would otherwise be smooth downstream trends in mainstream bed elevation channel gradient and bed grain size generic styles of mainstream response to lateral inputs are investigated using a one dimensional sediment routing model with multiple grain size fractions numerical experiments isolate the effects of three para meters ratio of tributary to mainstream water flux qr ratio of tributary to mainstream bedload flux fr and ratio of tributary to mainstream bedload diameter dr the findings are not unduly sensitive to the choice of initial conditions or to approximations made in the model the primary distinction is between junctions that aggrade causing local profile convexity with interrupted downstream fining and junctions that degrade the immediate effects of aggradation extend further upstream than downstream whereas degradation is much more subdued and has no upstream impact aggradation is typical of coarse inputs dr 2 and degradation of fine inputs dr 1 but very high ratios of qr to fr also promote degradation both aggrading and degrading junctions can lead to a change in mainstream bed grain size well below the junction with higher ratios of qr to fr producing a coarser distal bed the effect of a tributary reflects the interplay between additional bed load and additional discharge to transport it

grain size sorting within river bars in relation to downstream fining along a wandering channel the textural variability of river bed gravels at bar scales is poorly understood as are the relations between variability at this scale and at reach and river scales surface and subsurface grain size distributions were therefore examined at reach bar and bedform scales along lower fraser river british columbia canada grain size variations within compound bars are conditioned by longitudinal position elevation and morphological setting surface and subsurface sediments tend to decrease in median size from bar head to bar tail by 33 and 17 respectively sediment size is constrained at some upper limit that is inversely related to bar surface elevation and which is consistent with competence considerations the surface sediments on unit bars are finer and better sorted than the bed materials in bar top channels and along the main bar edges secondary unit bars tend to have a lower sand content than other features a consequence of sediment resorting individual unit bars and gravel sheets exhibit streamwise grain size fining and lee side sand deposition over time significant amounts of cut and fill do not ipso facto cause changes in surface grain sizes yet sediment characteristics can change without any significant morphological adjustment taking place at the reach scale there is a clear downstream fining trend but local variability is consistently high due to within bar variations the surface median grain size range on individual bars is on average 25 of that along the entire 50 km reach but is 68 on one bar while the overall fining trend yields a downstream change in surface median size of 0 76 mm km 1 the average value for head to tail size reduction on individual bars is 6 3 mm km 1 an order of magnitude difference that highlights the effectiveness of bar scale sorting processes in gravel bed rivers possibilities for modelling bar scale variability and the interaction of the different controls that are identified are discussed

depositional and erosional architectures of gravelly braid bar formed by a flood in the abe river central japan inferred from a three dimensional ground penetrating radar analysis abstract we conducted a ground penetrating radar gpr survey of gravelly braid bars in the abe river central japan to clarify the three dimensional 3d variations in their depositional facies under various geomorphologic conditions in september 2011 a ten year return period flood in the study area reworked and deposited braid bars after the flood we surveyed three bars with different geomorphologies using a gpr system with a 250 mhz antenna and identified seven fundamental radar depositional facies inclined reflections facies ia and ib horizontal to subhorizontal reflections facies iia and iib discontinuous reflections facies iiia and iiib and facies assemblage with a large scale channel shaped lower boundary facies iv combinations of these facies in dicate bar formation processes channel filling lateral aggradation and lateral and downstream accretion in the abe river aerial photographs and airborne laser scanning data were obtained before and after the flood the observed changes of the surface topography are consistent with the subsurface results seen in the gpr sections this study demonstrated that the erosional and depositional architecture observed among bars with different channel styles was related to river width and represented depositional processes for high sediment discharge the quantitative characterizations of the sedimentary architecture will be useful for interpreting gravelly fluvial deposits in the rock record

numerical model of sediment pulses and sediment supply disturbances in mountain rivers sediment pulses in rivers can result from many mechanisms including landslides entering from side slopes and debris flows entering from tributaries artificial sediment pulses can be caused by the removal of a dam this paper presents a numerical model for the simulation of gravel bedload transport and sediment pulse evolution in mountain rivers a combination of the backwater and quasi normal flow formulations is used to calculate flow parameters gravel bedload transport is calculated with the surface based bedload equation of parker in 1990 the exner equation of sediment continuity is used to express the mass balance at different grain size groups and lithologies as well as the abrasion of gravel the river is assumed to have no geological controls such as bedrock outcrops and immobile boulder pavements the results of nine numerical experiments designed to study various key parameters relevant to the evolution of sediment pulses are reported here results of the numerical runs indicate that the evol

continuous monitoring of bedload discharge in a small steep sandy channel this paper reports on bedload flux and texture monitored in a natural steep sandy ephemeral channel draining a small gullied sandy watershed the barranca de los pinos 1 32 ha spain bedload flux was continuously monitored with two independent reid type slot samplers bedload texture was determined from the sediment collected in the samplers channel morphology was surveyed with a high spatial resolution with a terrestrial laser scanner the monitored instantaneous bedload fluxes are among the highest measured in natural rivers characterized by high temporal and spatial variability related to the presence of bedforms shallow bars and sand sheets and to the reworking of the dry bed between and at the end of individual flow events the grain size distribution of the bedload indicates equal mobility but bedload texture fluctuates depicting the transport of coarser bar surfaces and of finer grained anabranch surfaces as well as of the overall bed subsurface

hydrothermal eruptions of nisyros dodecanese greece past events and present hazard abstract the detailed analysis of the craters of hydrothermal eruptions and related products present on nisyros island demonstrates the ephemerality of these morphological forms in other words the mere recognizable existence of the craters and associated deposits implies recency of hydrothermal activity the minimum temperature required to cause the explosive phenomenon and possibly the depth of the reservoir which can be evaluated on the basis of the correlation between the diameter of the crater and the depth of explosion as proposed by fytikas and marinelli 1976 are therefore closely representative of the current hydrothermal circulation both field evidence and historical records indicate that all the deposits of hydrothermal eruption recognized on nisyros island were emplaced as debris flows almost all the ballistic ejecta were entrained in these debris flows and either redeposited far from their landing sites or involved in later crater collapse and erosion this emplacing mechanism implies that the original products were characterized by a water content higher than about 5 by weight steam driven hydrothermal eruptions one of which took place in 1871 originated deposits of limited dispersion as no sign of these erodible products can be found in the field today surface geology and fluid geochemistry together with subsurface information e g primary and hydrothermal lithologies distribution of temperature with depth physical chemical characteristics of deep water bearing zones indicate that two distinct hydrothermal aquifers are present underneath the southeastern part of the caldera floor both aquifers were probably involved in the most important historically documented hydrothermal eruptions which occurred in 1873 at that time violent earthquakes fractured the brittle aquiclude separating the two aquifers and caused a sudden transfer of fluids from the deep to the shallow aquifer thus triggering the hydrothermal eruptions hydrothermal eruptions will probably occur in future and this hazard must be taken into serious consideration the southern half of lakki plain where all past eruptions took place and active fumaroles are concentrated is the zone at highest risk at present gas geochemistry represents an effective tool to detect changes in the p t conditions of the shallow aquifer and particularly the phenomena of pressure build up that may lead to a hydrothermal eruption

measurements in a braided river chute and lobe 2 sorting of bed load during entrainment transport and deposition grain size distributions of bed material bed load and bar head deposition were sampled during the evolution of a chute and lobe in the braided gravel bed sunwapta river alberta although bed shear stress and total bed load transport rate varied substantially within the reach and from day to day ferguson et al this issue the median diameter d50 of bed load was remarkably constant the bed initially fined from chute to bar head but became more uniform sediment deposited on the bar head also had a near constant d50 similar to that of the bed load truncated at the same lower size limit both load and deposition were finer on average than the bed suggesting overall selective transport despite little sign of local sorting in contrast to median diameters maximum sizes dmax of sediment in motion and deposited on the bar head varied substantially and showed a weak but significant dependence on shear stress inferring selective entrainment from this evidence alone would be dubious because dmax was also found to increase systematically with the mass of sediment sampled however two different methods of analysis of fractional transport rates throughout the size range also showed size selective entrainment and transport in the marginal transport conditions of this study size sorting appears to occur but only weakly and mainly in the coarser fractions

earthquake mechanisms in the gulfs of gokova sigacik kusadasi and the simav region western turkey neotectonics seismotectonics and geodynamic implications abstract the mechanical behavior of continental lithosphere of aegean region and western turkey is one of the foremost interesting geological disputes in earth sciences this region provides complex tectonic events which produced a strong heterogeneity in the crust as such in among most continental regions the reasons of the ongoing lithospheric scale extension within the aegean region can be revealed by the correlation with the prevailing kinematic and dynamic factors such as roll back of the subduction slab and back arc extension westward extrusion of the anatolian micro plate block rotations and transtensional transform faults seismological studies of earthquake source mechanisms and slip inversions play important roles on deciphering the current deformation and seismotectonic characteristics of the region in recent years several moderate earthquakes have occurred in the gulfs of gokova sigacik kusadasi and simav graben we studied source mechanisms and rupture histories of those earthquakes to retrieve the geometry of active faulting source characteristics kinematic and dynamic fault parameters and current deformations in western turkey we used teleseismic body waveform inversions of long period p and sh and broad band p waveforms we also checked first motion polarities of p waves recorded at both regional and teleseismic stations inversion results revealed e w striking normal faulting mechanisms with small amount of left lateral strike slip components in the gulf of gokova and ne sw oriented right lateral strike slip faulting mechanisms in the gulf of sigacik in simav graben earthquake source parameters show dominantly normal faulting mechanisms with strike slip components our inversions resulted in focal depths for the earthquake ranging from 10 to 15 km and ne sw trending t axes directions the finite fault slip distribution and rupture propagation models exhibit seismic moment releases and large displacement values which essentially occurred at hypocenters of the earthquakes the overall results exhibited uniform and circular shaped rupture propagations along dip directions of fault planes although most of the focal mechanism solutions show dominantly normal faulting mechanisms associated with the e w oriented horst graben structures in western turkey there are also strike slip faulting mechanisms related to remarkable strike slip faults which are capable of generating damaging earthquakes particularly in the gulf of sigacik and karaburun peninsula thus we suggest that present day deformation in the gulfs of gokova sigacik kusadasi and simav graben western turkey is still mainly driven by the n s extensional tectonics but we tentatively further emphasize the importance of strike slip faults in shaping tectonic structures in the aegean region

a modified morphodynamic model for investigating the response of rivers to short term climate change near future climate change will affect the discharge and base level of rivers and thus cause channel changes the nature and pace of such changes can be simulated using morphodynamic models as part of an investigation of how the changing hydrology of the st lawrence river quebec canada will affect its tributaries we have made additions and modifications to a one dimensional morphodynamic model developed for gravel bed rivers sedrout the changes allow simulation of sand bed rivers variable discharge downstream water level fluctuations and flow and sediment routing in channels with islands a revised formulation for calculating the grain size distributions of the surface and subsurface material is presented to allow for alternating sedimentation and erosion we test the enhanced model using small scale simulations and present day conditions in four tributaries of the st lawrence river the model is calibrated and validated for the tributaries and the capability to simulate river morphology over a 100 year period is tested good validation agreement on water level cross sectional mean velocity and sediment transport rate is obtained for the four tributaries of the st lawrence river with these modifications modelling a very wide range of river morphodynamic problems is now possible

estimating shear stress from moving boat acoustic doppler velocity measurements in a large gravel bed river 1 moving boat acoustic doppler current profiling adcp is increasingly used to measure discharge in large rivers we investigate whether useful information about bed shear stress can be recovered from such data alternative ways to estimate local bed shear stress using the logarithmic law of the wall and spatial averaging are tested using adcp transects across lower fraser river canada repeatability is assessed by comparing estimates from outward and return boat tracks the most precise method uses the vertically averaged mean velocity and a zero velocity height based on bed grain size information the accuracy of the assumed zero velocity height can be judged by consistency between estimates using mean velocity and near bed velocity shear stress estimates from unconstrained log law fits are less repeatable and tend to overpredict and mean shear stress estimates using the depth slope product are unreliable in this river because of nonuniform flow

a critical perspective on 1 d modeling of river processes gravel load and aggradation in lower fraser river 1 we investigate how well a width averaged morphodynamic model can simulate gravel transport and aggradation along a highly irregular 38 km reach of lower fraser river and discuss critical issues in this type of modeling bed load equations with plausible parameter values predict a gravel input consistent with direct measurements and a sediment budget simulations using spatially varying channel width and forced by dominant discharge or a 20 year hydrograph match the observed downstream fining well they reproduce major qualitative features of a 47 year sediment budget and match maximum local rates of aggradation and degradation to well within a factor of 2 locations and rates of aggradation and degradation are influenced by channel constrictions runs for single years of unusually high or low peak discharge suggest that the main transfers of gravel occur in different parts of the reach in different years one dimensional morphodynamic modeling of highly nonuniform rivers has serious conceptual limitations but may be a valuable complement to empirical approaches

remote monitoring of the mechanical instability induced by fluid substitution and water weakening in the laboratory abstract we studied the effect of fluid injection on the mechanical behaviour of the poorly consolidated and layered sherwood sandstone under varying stresses with micro seismic ms monitoring in order to highlight possible weakening effects water and inert oil have been injected into critically loaded samples to assess their effect on strength and elastic properties derive the ultrasonic signature of the saturation front for each fluid and the potential development of damage to this end the specimens were instrumented with 16 ultrasonic p wave transducers used for both passive and active monitoring during loading and fluid injection a first set of injection tests in hydrostatic conditions using either water or inert oil has been performed on samples subjected to low confining pressure water invasion in the pore space induces a significant decrease of the p wave velocity whereas oil invasion shows a velocity increase the velocity decrease associated with water injection is analysed in terms of attenuation mechanisms and corresponding critical frequencies a second series of injection tests with the same fluids has been performed during creep tests on critically loaded samples the development of mechanical instability inducing micro seismic activity is observed only when water is injected into the sample the recorded micro seismic events are spatially and temporally located thanks to the dedicated velocity models accounting for the initially homogeneous sample anisotropy and for the heterogeneous velocity field associated with fluid migration within the sample the consistency between the relocated clusters of events and the final damage pattern is verified thanks to x ray computed tomography images of the samples taken post mortem

grain size along two gravel bed rivers statistical variation spatial pattern and sedimentary links a new set of field data facilitates a detailed analysis of variations in bed material grain size within two confluent gravel bed rivers in northeastern british columbia canada a preliminary assessment of grain size variability establishes a basis for examination of the spatial pattern of grain size change standard anova techniques are inappropriate because individual samples have unequal variances and are not normally distributed alternative tests for homoscedasticity and comparison of means are therefore utilized within site between sample variability is not significant the grain size distributions that were obtained at individual sites are therefore representative of the depositional environments that were sampled in both rivers mean grain size does vary significantly between sites and there is therefore a basis for examining the data for spatial patterns such as downstream fining textural variations along the two rivers studied here are complex and show negligible overall fining in over 100 km this is the consequence of a large number of tributary inputs and non alluvial sediment sources which are the legacy of late pleistocene glaciation the identification of lateral sources like these is fundamental for understanding textural changes within rivers the sedimentary link a channel reach between significant lateral sediment inputs provides a means of isolating fluvial maturation processes abrasion and sorting from contingent lateral inputs strong fining trends are apparent in most links and classification of grain size measurements according to their location within particular links greatly improves the statistical explanation of textural variation identification of sedimentary links provides a means of applying models of fluvial fining processes so isolation of link networks will aid the development of basin scale models of textural variation 1998 john wiley sons ltd

towards successful osl sampling strategies in glacial environments deciphering the influence of depositional processes on bleaching of modern glacial sediments from jostedalen southern norway the optically stimulated luminescence osl signals of quartz and k feldspar are known to bleach poorly within some glacial settings and can present a major challenge to dating applications however because the osl signal is extremely sensitive to sunlight exposure history the residual luminescence signals of modern glacial sediments also encode information about transport and depositional processes through examination of the residual luminescence properties equivalent dose de and overdispersion values of a suite of modern glacial sediments from different depositional settings sandar proglacial delta and main meltwater channel this study provides insights not only into which sediments are likely to be fully bleached within glacial settings but also into how osl can be used to trace different depositional processes across sedimentary landforms improved understanding of the processes of sediment bleaching will enable better sample selection and may improve the accuracy and precision of osl dating of glacial sediments the luminescence signals of both coarse grained quartz and k feldspar with similar sediment sources are found to be sensitive to both depositional process and specific depositional setting whereas modern braid bar head deposits from the nigardsdalen ice proximal proglacial delta typically have ages of 3 ka similar depositional features from the fabergstolsgrandane sandur have residual ages of 26 ka exploration of changing residual luminescence signals across individual sandur and proglacial delta braid bar features shows that braid bar head deposits can retain large residual d e values while the partner braid bar tail deposits are almost completely bleached the quartz osl signal and k feldspar irsl50 and post ir irsl250 signals are shown to bleach at the same rate across the same bar feature and the irsl50 k feldspar signal is also shown to be completely bleached for bar tail deposits in nigardsdalen therefore the irsl50 k feldspar signal is suitable for dating some glacial deposits circumventing the challenges associated with dim quartz signals 2014 the authors published by elsevier ltd this is an open access article under the cc by license

ground deformation of nisyros volcano greece for the period 1995 2002 results from dinsar and dgps observations differential gps dgps and differential inter ferometric synthetic aperture radar dinsar analyses were applied to the kos yali nisyros volcanic field se hellenic volcanic arc to quantify the ground deformation of nisyros volcano after intense seismic activity in 1996 a gps network was installed in june 1997 and re occupied annually up to 2002 a general uplift ranging from 14 to 140 mm was determined at all stations of the network the corresponding horizontal displacements ranged from 13 to 53 mm the displacement vectors indicate that the island is undergoing extension towards the east west and south a two source mogi model combined with assumed mo tion along the mandraki fault was constructed to fit the observed deformation the best fit model assumes sources at a depth of 5500 m nw of the centre of the island and at 6500 m offshore ese of yali island dinsar analysis using four pairs of images taken between may 1995 and september 2000 suggests that deformation was occurring during 1995 before the start of the seismic crisis an ampli tude of at least 56 mm along the slant range appeared for the period 1996 through 1999 this deformation is consistent with the two source model invoked in dgps modelling surface evidence of ground deformation is expressed in the contemporaneous reactivation of the mandraki fault

morphology and evolution of bars in a wandering gravel bed river lower fraser river british columbia canada a hierarchical typology for the channels and bars within aggradational wandering gravel bed rivers is developed from an examination of a 50 km reach of lower fraser river british columbia canada unit bars built by stacking of gravelly bedload sheets are the key dynamic element of the sediment transfer system linking sediment transport during individual freshets to the creation development and remoulding of compound bar platforms that have either a lateral or medial style primary and secondary unit bars are identified respectively as those that deliver sediment to compound bars from the principal channel and those that redistribute sediment across the compound bar via seasonal anabranches and smaller channels the record of bar accretion evident in ground penetrating radar sequences is consistent with the long term development of bar complexes derived from historical aerial photographs for two compound bars inter annual changes associated with individual sediment transport episodes are measured using detailed topographic surveys and longer term changes are quantified using sediment budgets derived for individual bars from periodic channel surveys annual sediment turnover on the bars is comparable with the bed material transfer rate along the channel indicating that relatively little bed material bypasses the bars bar construction and change are mainly accomplished by lateral accretion since the river has limited capacity to raise bed load onto higher surfaces styles of accretion and erosion and therefore the major bar form morphologies on fraser river are familiar and consistent with those in gravelly braided channels but the wandering style does exhibit some distinctive features for example 65 year histories reveal the potential for long sequences of uninterrupted accretion in relatively stable wandering rivers that are unlikely in braided rivers

the gravel sand transition along river channels abstract this paper discusses a hitherto neglected aspect of fluvial downstream fining the transition from a gravel bed to a sand bed from the few known examples and by additional study of new sites some general features of such transitions are given these transitions are generally rapid and involve a change in bed texture from unimodal gravels through bimodal sediments to exclusively sand material and are often associated with a break in slope we propose three possible causes local base level control an excess of sand supply and abrasion breakdown of fine gravel we further argue that such transitions occur in a variety of fluvial environments and are geographically more widespread than previously supposed and on this basis we suggest they may also aid in interpreting ancient sediment showing bimodality and rapid proximal to distal changes in grain size

fluvial aggradation in vedder river testing a one dimensional sedimentation model sediment routing models which simulate the coevolution of river long profile and bed grain size distributions have been used to investigate downstream fining above base level channel response to rectification and other disequilibrium situations at a variety of timescales we extend one such model sedrout hoey and ferguson 1994 to deal with sand as well as gravel and test its ability to simulate aggradation and downstream fining in a well documented canadian river previous tests of this and similar models have been largely restricted to comparing observed and simulated gradients of downstream fining but it is not obvious when to make the comparison in a time dependent model with uncertain initial state and no equilibrium except in the very long term we discuss and apply a more rigorous set of test criteria and address issues of defining initial conditions and time to test the model s varying sensitivity to different boundary conditions and parameters indicates key data constraints on the testability and predictive accuracy of any such model we also consider the adequacy of one dimensional calculations in channels with variable width and present initial results of attempts to allow for this

response of a channel with alternate bars to a decrease in supply of mixed size bed load a flume experiment the response of a channel with a topography and modeled bed material size typical of gravel bed rivers to reductions in sediment supply was investigated in a laboratory flume filled and fed with a sand gravel mixture after a series of quasi stationary alternate bars were formed under equilibrium sediment transport feed rate was reduced in two steps to one third and one tenth the initial rate as discharge was held constant the primary response following both reductions was an increase in bed surface particle size as a corridor of intensive bed load transport contracted and local transport rates decreased after the first feed rate reduction the channel incised by twice the mean water depth on average and caused distal bar surfaces to emerge as terracelike features bar roughness decreased and mean boundary shear stress exerted on bed surface particles increased little incision occurred after the second feed rate reduction

the potential for future explosive volcanism associated with dome growth at nisyros aegean volcanic arc greece monitoring of the explosivity controlling parameters in magmas associated with dome growth in the quaternary volcano at nisyros aegean sea involves determining the chemical composition including dissolved volatiles h2o co2 f cl and s of melt inclusions in phenocrysts and interstitial matrices in pre and post caldera volcanic products our results indicate that the volatile content of the pre caldera magma was a dominant factor responsible for the catastrophic explosivity of the caldera forming episode the relatively high estimated volatile contents and apparent interstitial viscosities of the post caldera magmas as well as the geophysical evidence for the existence of an active magma chamber beneath nisyros all suggest that this volcano is presently dormant but has a high potential for future explosive volcanism

modelling gravel transport and morphology for the fraser river gravel reach british columbia a two dimensional 2d numerical hydrodynamic morphological model is developed to investigate gravel transport and channel morphology in a large wandering gravel bed river the fraser river gravel reach in british columbia canada the model takes into count multi fraction bedload transport including the effects of surface coarsening hiding and protrusion model outputs together with river discharge statistics were analyzed producing distributed sediment budget and well defined localised zones of aggradation and degradation along the gravel reach long term channel response to gravel extraction from aggrading zones as a flood hazard mitigation measure was also investigated numerically to assess the effectiveness of such an extraction the total computed sediment budget agrees well with results based on field measurements of gravel transport available to us this study points to the importance of a number of factors to bedload predictions the gravel to sand ratio the adequacy of resolving the wandering planform and the distinction between bed shear stress driving bedload transport and bed resistance on the flow these are in addition to the physical processes governing the flow field and gravel mobilization the methodology presented in this paper can provide a scientific basis for gravel management including monitoring and extraction in order to maintain adequate flood protection and navigation while preserving the ecosystem

selective sorting and abrasion of river gravel i theory most gravel rivers show a tendency for characteristic grain size to decrease in the downstream direction over scales of tens or hundreds of kilometers it has been surmised that this downstream fining is due to some combination of selective sorting by which finer grains are preferentially transported downstream and abrasion by which individual particles are reduced in size here a framework for the simultaneous treatment of both phenomena is developed the analysis is restricted to bed load transport of gravel only abrasion due to binary collisions between moving bed load and stationary bed particles is considered the formulation includes the possibility of differential basin uplift and subsidence due to tectonism and mixtures of rock types with differing coefficients of abrasion the formulation of selective sorting is based on the concept of hiding as applied to a surface based bed load transport relation abrasion is first treated in terms of a lagrangian formulation for individual grains and t

bedload sheets in heterogeneous sediment field observations in streams with beds of coarse sand and fine gravel have revealed that bedload moves primarily as thin migrating accumulations of sediment and coarse grains cluster at their leading edge these accumulations are one or two coarse grains high and are much longer 0 2 0 6 m long in sand 0 5 2 0 m in fine gravel than their height the authors propose the term bedload sheet for these features and the authors argue that they result from an instability inherent to bedload movement of moderately and poorly sorted sediment in essence coarse particles in the bedload slow or stop each other trap finer particles in their interstices and thus cause the coarse particles to become mobile again bedload sheets develop on the stoss side of dunes causing the dune to advance incrementally with the arrival of each sheet successive deposition of coarse sediment from the leading edge followed by fine sediment may generate the grain size sorting that distinguishes cross bedding available flume experiments and field observations indicate that bedload sheets are a common but generally unrecognized feature of heterogeneous sediment transport

routing of heterogeneous sediments over movable bed model verification a one dimensional numerical model of heterogeneous size density sediment transport has been developed to simulate the movement of graded sediments in natural and laboratory flow reaches predicted temporal and spatial variations in bed and armor layer grain size distributions eroded grain size distribution eroded thicknesses and total bedload transport rates compare quite favorably to observed variations in flumes the san luis canal colorado and the east fork river wyoming for a large variety of flow scales and flow conditions the main advantages of this model over others is the high degree of accuracy of model results obtained using only bed and flow variables as input the treatment of turbulent fluctuations of bed shear stress the minimization of calibration factors and the explicit treatment of multiple grain densities in addition only the active layer thickness must be calibrated

high resolution grain size characterisation of gravel bars using imagery analysis and geo statistics abstract the scarcity of grain size data from gravel bed rivers has traditionally hindered hydraulic sediment transport and river habitat studies a new remote sensing methodology to estimate grain size distribution is presented it combines textural digital images of the riverbed at 1 1000 and 1 40 scales with grain size sampling it was applied to a 12 km reach of the isabena river central pyrenees ne spain first textural patterns for each grain size range were obtained selecting the most closely related texture variables including the use of semivariograms second multiple linear regression equations were derived from the textural variables to estimate each value of the grain size distribution the highest correlation values r 2 were obtained from the central part of the distribution d 50 with a rms error of 12 7 finally new multiple linear regression equations to estimate the d 50 and d 84 were obtained from 1 1000 images and four textural variables these were used to derive d 50 and d 84 maps of the riverbed re sampled at a resolution of 1 5 m pixels with rms estimation errors of 26 and 32 respectively downstream change in grain size is also well reproduced by the method the mean d 50 of 72 and 32 mm were estimated in the upper and the lower reaches of the river respectively the methodology shows great potential for application the relation between the spatial resolution of the images and the mean grain size of the riverbed sediment being the main issue for future development

sediment supply and the development of the coarse surface layer in gravel bedded rivers the bed surface of most gravel rivers is considerably coarser than the sub surface or the gravel load transported over it a phenomenon affecting river dynamics morphology and ecology the coarse surface layer often called an armour or pavement has been attributed to an inherent tendency for small grains to settle between larger ones during active transport of all sizes1 2 and to selective erosion or trapping of finer particles when the coarse grains are relatively immobile3 4 where bedload supply is cut off below dams selective erosion causes coarsening5 6 using a simple quantitative model we propose that surface coarsening develops in gravel bedded rivers when local bedload supply from upstream is less than the ability of the flow to transport that load we present laboratory results which support this hypothesis and show that supply reduction causes changes in bedforms and progressive confinement of active bedload transport to a narrow band of finer bed surface bordered by a coarse less active bed it may therefore be possible to relate the degree of river bed surface coarsening to sediment supply resulting from land use

comparison between outcrop spectral gamma ray logging and whole rock geochemistry implications for quantitative reservoir characterisation in continental sequences abstract a high resolution spectral gamma ray sgr log is compared to elemental whole rock geochemical data in a reservoir scale outcrop analogue the otter sandstone formation sherwood sandstone group east devon sgr data compare closely to those generated for point samples by inductively coupled plasma icp techniques with disparities attributable to the different sample volumes icp data reveal separate mineralogical sources for radio elements which enable three lithotypes to be discriminated using th u ratio and k 2 o data once established the discriminants are applied to the sgr log enabling three lithotypes to be dicriminated these conclusions suggests that sgr logs have significant potential for real time lithotype prediction in continental sequences which in turn enable predictions of reservoir quality and increase confidence in the interpretation of sedimentary architecture

behavior of hydrocarbon reservoir sands and sandstones most new oil and gas reservoirs are discovered in sands and weak sandstones and the petroleum industry has therefore generated an extensive amount of data from laboratory tests on these materials some of these data are reexamined in this paper within the context of recent soil mechanics research of key importance to petroleum engineers is the compressibility of the sands and this is shown to be related both to the current density and stress level of the soil and to the location of its normal compression line when present the cement bonds between the particles appear to be weaker than the particles themselves so that the major yield point during compression is still associated with breakage of the particles rather than of the cement bonds the paper also examines the behavior of the sands and sandstones in shearing allowing a more general understanding of the mechanics of the materials to be developed

faulting and effects of earthquakes on minoan archaeological sites in crete greece abstract examination of damages affecting the buildings of the archaeological sites of phaistos and agia triada southern crete suggests that these minoan settlements were probably destroyed by two major seismic events characterized by mks intensities of ix x and occurred at the end of the protopalatial 1700 bc and the neopalatial 1450 bc periods geological and morphological studies carried out in the neighbouring areas show the occurrence of e w trending quaternary normal fault segments spili and agia galini faults that control the present topography and morphology and exhibit steep young scarps mostly holocene in age these fault segments are related to a nw se extension direction which is consistent with that indicated by the available focal mechanisms of the earthquakes occurring in this area in the last 50 years combining structural and seismic data we can infer that the spili and agia galini fault segments could represent good candidates to be considered active faults generating large earthquakes m 6 5 that were responsible for the damages of phaistos and agia triada this hypothesis suggests that the minoan palatial centres were destroyed by several large earthquakes related to ruptures along distinct fault segments rather than by a single catastrophic event that caused the abrupt destruction of the minoan civilisation in the eastern mediterranean

subsurface flow in lowland river gravel bars geomorphic and hydraulic processes which form gravel bars in large lowland rivers have distinctive characteristics that control the magnitude and spatial patterns of infiltration and exfiltration between rivers and their immediate subsurface environments we present a bedform infiltration relation together with a set of field measurements along two reaches of the san joaquin river ca to illustrate the conditions required for infiltration and exfiltration of flow between a stream and its undulating bed and a numerical model to investigate the factors that affect paths and residence times of flow through barforms at different discharges it is shown that asymmetry of bar morphology is a first order control on the extent and location of infiltration which would otherwise produce equal areas of infiltration and exfiltration under the assumption of sinusoidal bedforms hydraulic conductivity varies by orders of magnitude due to fine sediment accumulation and downstream coarsening related to the process of bar evolution this systematic variability not only controls the magnitude of infiltration but also the residence time of flow through the bed the lowest hydraulic conductivity along the reach occurred where the difference between the topographic gradient and the water surface gradient is at a maximum and thus where infiltration would be greatest into a homogeneous bar indicating the importance of managing sand supply to maintain the ventilation and flow through salmon spawning riffles numerical simulations corroborate our interpretation that infiltration patterns and rates are controlled by distinctive features of bar morphology

the nature and controls on downstream fining within sedimentary links abstract at scales of 100 to 102 km grain size change in gravelly alluvial systems is characterized by punctuated downstream fining significant lateral sediment inputs define a sequence of sedimentary links within which fluvial processes produce fining trends using a new set of surface grain size data eighteen such links along two canadian gravel bed rivers are examined negative exponential functions are found to be most appropriate for describing within link grain size changes development of a pragmatic means of predicting grain size is then pursued by searching for a means to relate model diminution coefficients to link attributes consideration of lithologically differentiated fining trends indicates that lithology plays an insignificant role in controlling fining rate examination of within link longitudinal profiles indicates a reasonable relation between fining rate and the rate of change of channel slope the predictive value of this relation is limited by the regional nature of the data upon which it is based and the relative difficulty of obtaining accurate gradient information however as previously noted for alluvial fans although for different reasons channel gradient is correlated with link length and a reasonable predictive tool is apparent in a relation between link length and diminution rate the validity of the derived relation cannot be tested for want of a suitable data set several lines of evidence indicate that abrasion is unimportant as a fining mechanism on these rivers and it is argued that this may be typical of sedimentary links fining rate must then be a function of the efficiency with which sorting processes operate and it is suggested that this efficiency is dependent on aggradation rates associated with the lateral sediment influxes at the head and terminus of individual links

one dimensional numerical modeling of sediment transport and bed deformation in open channels 1 a one dimensional numerical model for simulating unsteady flow and sediment transport in open channels is presented and tested the flow hydrodynamics is represented by the shallow water equations and the bed morphodynamics is represented by the exner equation and an additional equation describing the nonequilibrium sediment transport sediment size distribution is represented by the median grain diameter and the standard deviation instead of the usual modeling with multiple particle size classes various methods for computing bed elevation changes at a cross section due to erosion or deposition of sediment are proposed and tested including an innovative approach that relates the spatial pattern of erosion and deposition rates to boundary shear stress distribution which is calculated by the merged perpendicular method an explicit finite difference scheme is employed for solving the water and sediment governing equations the pertinence of the model is examined for two hypothetical cases the model is then tested on one set of laboratory experiments on bed degradation under steady flow showing excellent model data fit and indicating that incorporating a nonequilibrium sediment transport equation into the model structure is an important element in reproducing the bed degradation process finally the model is applied to simulate the morphological changes taking place in the ha ha river quebec after the failure of the ha ha dyke on july 1996 relevant results can be obtained in terms of changes in longitudinal bed profile and cross sectional geometry as well as water levels although some discrepancies are obtained between the simulated and surveyed cross sectional geometries mainly because bank failure and channel widening are not modeled

field application of close range digital photogrammetry crdp for grain scale fluvial morphology studies in situ measurement of grain scale fluvial morphology is important for studies on grain roughness sediment transport and the interactions between animals and the geomorphology topics relevant to many river practitioners close range digital photogrammetry crdp and terrestrial laser scanning tls are the two most common techniques to obtain high resolution digital elevation models dems from fluvial surfaces however field application of topography remote sensing at the grain scale is presently hindered mainly by the tedious workflow challenges that one needs to overcome to obtain high accuracy elevation data a recommended approach for crdp to collect high resolution and high accuracy dems has been developed for gravel bed flume studies the present paper investigates the deployment of the laboratory technique on three exposed gravel bars in a natural river environment in contrast to other approaches having the calibration carried out in the laboratory removes the need for independently surveyed ground control targets and makes for an efficient and effective data collection in the field optimization of the gravel bed imagery helps dem collection without being impacted by variable lighting conditions the benefit of a light weight three dimensional printed gravel bed model for dem quality assessment is shown and confirms the reliability of grain roughness data measured with crdp imagery and dem analysis evidences sedimentological contrasts between gravel bars within the reach the analysis of the surface elevations shows the effect variable grain size and sediment sorting have on the surface roughness by plotting the two dimensional structure functions and surface slopes and aspects we identify different grain arrangements and surface structures the calculation of the inclination index allows determining the surface forming flow direction s we show that progress in topography remote sensing is important to extend our knowledge on fluvial morphology processes at the grain scale and how a technique customized for use by fluvial geomorphologists in the field benefits this progress copyright 2016 john wiley sons ltd

ultrasonic monitoring of spontaneous imbibition experiments acoustic signature of fluid migration capillary rise experiments spontaneous imbibition tests were conducted in the laboratory with ultrasonic and x ray monitoring on the sherwood sandstone and the majella grainstone the aim was to provide a direct comparison between the variation in seismic attributes amplitude velocity spectral content and energy and the actual fluid distribution in the rock two pairs of ultrasonic p wave sensors located at different heights on a cylindrical rock specimen recorded every 5 s the waveforms when capillary forces make water rise up into the rock from the bottom in contact with a water tank simultaneously computerized tomography scan images of a vertical cross section were also recorded two important results were found i the amplitude of the first p wave arrival is impacted by the upward moving fluid front before the p wave velocity is while the fluid front has not yet reached the sensors level in contrast the p wave velocity decreases when the fluid front reaches the fresnel clearance zone the spectral analysis of the waveforms shows that the peak frequency amplitude is continuously decreasing without noticeable frequency shift ii a methodology based on the calculation of the analytical signal and instantaneous phase was designed to decompose each waveform into discrete wavelets associated with direct or reflected waves the energy carried by the wavelets is very sensitive to the fluid substitution process the coda wavelets related to reflections on the bottom end face of the specimen are impacted as soon as imbibition starts and can be used as a precursor for the arriving fluid

numerical modeling of gravel bed river response to meander straightening the coupling between the evolution of bed pavement and long profile 1 artificial meander straightening rectification was conducted in the early 1960s along the sainte marguerite river canada in order to facilitate highway construction along the valley previous studies talbot and lapointe 2002 confirm that vertical reprofiling coupled with pavement coarsening in the degrading reach were the main responses counteracting the disequilibrium in gravel transport rates triggered at rectification of this system numerical simulations using sedrout2 0 a one dimensional hydraulic and sediment transport model and validated against the observed channel response show the important role played by an advancing wave of pavement coarsening down the rectified reach in modulating the bed degradation response simulations extending into the future reveal an asymptotically slowing approach to equilibrium in the middle of the 21st century with a response half time of the order of 10 years in near threshold gravel bed systems like the sainte marguerite river pavement coarsening after rectification buffers the system against extreme degradation most significantly for watershed management this also appears to severely limit the extent of propagation of degradation upstream of the rectification

observations of downstream fining on the north fork toutle river near mount st helens washington we carried out a series of measurements to provide data for testing models of downstream fining in an actively braiding gravel bed river in particular the model developed in the previous paper we sampled a series of nine cross sections for bulk grain size distributions over a downstream distance of 5 4 km on the north fork toutle river near mount st helens washington in addition we sampled two of the nine sections for detailed analysis of surface grain size distributions in the cross stream direction by wolman counting within areas of distinct mean grain size patches our theory predicts that the rate of downstream fining depends on the distribution of deposition and a relative mobility function that depends on the characteristics of the grain size patches application of the theory to the study area shows that most of the observed downstream fining can be explained using patchiness as the dominant mechanism

temporal variations in seismicity during quasi static and dynamic rock failure abstract a comprehensive model is presented which can explain temporal fluctuations in seismic b values in the period leading to mechanical failure in terms of the underlying physical processes of time varying applied stress and stress corrosion enhanced crack growth under conditions of constant strain rate the form of the b value anomaly in the period leading to failure depends on the form of the stress time relationship for the case where dynamic failure occurs at peak stress after a period of strain hardening the model predicts a single cusp like b value anomaly reaching a critically low value of 0 5 at failure for the physically most realistic case where dynamic failure is preceded by a period of precursory strain energy release during strain softening the model predicts two minima in the b value separated by a temporary maximum or inflection point these fluctuations in the b value are consistent with reported intermediate term and short term earthquake precursors separated by a period of seismic quiescence for the case of quasi static cataclastic flow the b value mirrors the stress and never falls to the critical value because there is no critical rupture new results from a series of controlled laboratory experiments are presented in which microseismic event rates and b value were monitored contemporaneously with stress time data for all variants of the stress time relationship recent field observations of temporal changes in seismicity rates and b value preceding major earthquakes are also reported both data sets exhibit b value anomalies which are consistent with the model predictions

end effects on stress dependent permeability measurements abstract permeability changes have been studied under deviatoric stresses for chalk cores and under both hydrostatic and deviatoric stresses for sandstone cores at room temperature to avoid end effects in the triaxial cell caused by friction between the axial steel pistons and the sample the cell was modified to have pressure outlets from the mid section of the sample with pressure tubes connected to the outside of the cell for pressure recording both permeabilities over the mid section and over the total core were determined during the action of stresses the chalk cores with permeability in the range of 1 3 10 15 m 2 and porosity of about 40 45 were flooded with methanol while the sandstone cores with permeability values varying from 8 to 100 10 15 m 2 and porosity of about 30 were flooded with a mineral oil major observations were 1 for the chalk cores 4 out of 8 samples showed a mid section permeability with a factor of 1 2 to 1 4 higher than the overall permeability the remaining 4 samples did not show differences in permeability values taking into account the error on measurements 2 for the sandstone samples the mid section permeability was a factor of 1 2 to 2 4 higher than the overall permeability 3 in all cases during the deviatoric phase the change in permeability was rather small even if the tests were run beyond the yield point 4 the permeability generally decreased with increasing hydrostatic stresses

sedimentary links and the spatial organization of atlantic salmon salmo salar spawning habitat in a canadian shield river abstract the segmenting of gravel bed rivers flowing through mountain valleys into a number of discrete sedimentary links each characterized by downstream fining of alluvium is a relatively recent concept which offers promise to model the large scale spatial organisation of many types of aquatic habitat reproductive feeding refuge etc strongly dependent on dominant bed sediment calibre although so far the ecological application of the concept has mainly focused on benthic invertebrates here we illustrate its application to fish atlantic salmon salmo salar moreover the link concept has also been primarily applied to alpine river environments where link formation is triggered by point sources mainly tributaries supplying coarser sediment however somewhat lower relief mountain valley landscapes of north eastern canada are often structured into sedimentary links triggered by non point supply zones of coarse sediments originating in bedrock canyon reaches or valley bottom deposits of glacial drift here we propose an adaptation and extension of the original sedimentary link concept to such landscapes and test its utility along one such system the ste marguerite river smr a salmon river draining the canadian shield in the saguenay region of quebec we first discuss a simple field and office based method of link delineation then we discuss potential sources of minor sublink scale grain size variability and their effects on how sedimentary links are defined lastly we demonstrate the usefulness of the link structure to model the distribution of atlantic salmon spawning habitat a habitat that depends critically on bed texture our results indicate that a revised sedimentary link typology is needed to describe longitudinal grain size patterns where non point valley segment scale sources of coarse sediment are important and that consideration of the research purpose and scale is important in defining meaningful link units we also show that salmon spawning zones can be directly predicted from the link structure along the smr spawning activity is apportioned within each of the discrete links in those sub zones where surface sediment size and sand content are optimal for reproduction

variation in surface bed material along a mountain river modified by gravel extraction and channelization the czarny dunajec polish carpathians abstract longitudinal changes in the grain size of bar sediments of the mountain czarny dunajec southern poland were investigated to determine the impact of human activity in the river on depositional conditions in its channel the grain size of surface bed material was established on 47 gravel bars along an 18 km long river reach without tributaries in which some sections were modified over the past few decades by channelization or gravel extraction and the resultant channel incision a downstream fining trend of bar sediments was determined from samples taken at the sites with close to average river width and a vertically stable channel and used as reference for the other samples in the deeply incised upper part of the reach bar gravels are markedly coarser than the reference grain size in the narrow channelized section in the middle part of the reach bar sediments exhibit better than average sorting and change from coarser gradation to one similar to that of the reference grain size along the section in the wide multithread channel in the lower part of the reach bar gravels are distinctly finer than the reference grain size a similar pattern of downstream variation in the study reach was determined for the river competence on the basis of critical bed shear stress required to entrain d95 particles of the bar gravels the extraction of larger particles from the channel bed in the upper part of the study reach facilitated entrainment of exposed finer grains hence inducing rapid bed degradation at the same time the concentration of flood flows in an increasingly narrow and deep channel must have increased their competence enabling a delivery of the coarse particles previously typical of the upstream reach the middle section has been channelized to prevent sediment delivery to a downstream located dam reservoir however it actually operates as a conveyor belt transferring downstream the bed material flushed out from the upstream incising river section as low unit stream power and high channel form roughness facilitate sediment deposition in the unmanaged lower part of the reach it functions as a sediment sink and may reduce bed material delivery to the dam reservoir

particle over passing on depth limited gravel bars an experimental channel is used to examine the transport of mixed sand and gravel bedload over the crestal platform of hump back bars and along the top of planar gravel sheets hydraulic processes result in the simultaneous transport of cobbles and pebbles over a static closely packed bed consisting of like sized and finer particles for prescribed conditions flat upper stage plane sand beds develop over the crestal location with pebbles rolling easily over the sandy bed at the brinkpoint flow separation ensures effective segregation of the gravel from the sand over the slip face the deposition rate of the sand is insufficient to fill fully the interstices within the gravel foresets before rapid deposition of gravel further advances the bed form consequently distinctive vertical assemblages of open work and closed contact framework gravels could be generated as another bar migrates over and preserves the initial structure in respect to the observed mechanisms of sorting over the bars a mathematical expression is developed to explain the critical conditions allowing coarse particle mobility over planar sand or gravel beds under upper stage plane bed conditions on the crestal platform the model then is used to ascertain whether the depositional environment ascribed to certain facies in the bunter pebble beds described in a recent publication is appropriate given the distinctive facies assemblages generated in this experiment and the known hydrodynamic control of the particle segregation process

integrated geophysical and hydromechanical assessment for co2 storage shallow low permeable reservoir sandstones geological reservoirs can be structurally complex and can respond to co2 injection both geochemically and geomechanically hence predicting reservoir formation behaviour in response to co2 injection and assessing the resulting hazards are important prerequisites for safe geological co2 storage this requires a detailed study of thermal hydro mechanical chemical coupled phenomena that can be triggered in the reservoir formation most readily achieved through laboratory simulations of co2 injection into typical reservoir formations here we present the first results from a new experimental apparatus of a steady state drainage flooding test conducted through a synthetic sandstone sample simulating real co2 storage reservoir conditions in a shallow 1 km low permeability 1md 26 porosity sandstone formation the injected pore fluid comprised brine with co2 saturation increasing in steps of 20 brine co2 partial flow rates up to 100 co2 flow at each pore fluid stage an unload loading cycle of effective pressure was imposed to study the response of the rock under different geomechanical scenarios the monitoring included axial strains and relative permeability in a continuous mode hydromechanical assessment and related geophysical signatures ultrasonic p wave and s wave velocities vp and vs and attenuations qp 1 and qs 1 respectively and electrical resistivity on average the results showed vp and vs dropped 7 and 4 respectively during the test whereas qp 1 increased 55 and qs 1 decreased by 25 from the electrical resistivity data we estimated a maximum co2 saturation of 0 5 whereas relative permeability curves were adjusted for both fluids comparing the experimental results to theoretical predictions we found that gassmann s equations explain vp at high and very low co2 saturations whereas bulk modulus yields results consistent with white and dutta ode model predictions this is interpreted as a heterogeneous distribution of the two pore fluid phases corroborated by electrical resistivity tomography images the integration of laboratory geophysical and hydromechanical observations on representative shallow low permeable sandstone reservoir allowed us to distinguish between pure geomechanical responses and those associated with the pore fluid distribution this is a key aspect in understanding co2 injection effects in deep geological reservoirs associated with carbon capture and storage practices

predicting and monitoring long term compaction in unconsolidated reservoir sands using a dual power law model we propose a model for predicting the long term creep compaction of unconsolidated sand reservoirs prior to significant depletion the model is based upon linear viscoelasticity theory whereby deformation is decoupled into instantaneous and time dependent components the instantaneous component of deformation is modeled using a power law function of effective pressure model parameters are solved by conducting a constant strain rate laboratory experiment the time dependent deformation is modeled using a power law function of time associated model parameters are solved by conducting a creep strain test at the anticipated in situ effective pressure in total application of the model involves measurement of three model parameters obtained by conducting two different laboratory experiments we illustrate the model utilizing samples from unconsolidated sand reservoirs in the wilmington field in california and an offshore field in the gulf of mexico we show that the stiffness change associated with the porosity reduction predicted by the model is large and could be monitored using p wave velocity this should make compaction observable with 4d seismic surveys of the example fields