brittle ductile transition shear failure and leakage in shales and mudrocks abstract this paper presents an experimental study on brittle ductile transition shear behaviour the formation of shear fractures in shales and mudrocks and the hydraulic properties of shales and mudrocks with shear induced fractures the experimental study is based on triaxial tests on different mudrocks and shales from north sea reservoirs and adjacent areas sheared at different effective confining stresses it is shown that during burial mudrocks behave as normally consolidated materials and exhibit ductile response to increased load however several processes like uplift chemical diagenesis and overpressure build up turn mudrocks into overconsolidated materials which exhibit brittle behaviour during loading triaxial tests with different loading conditions have been performed to establish the brittle to ductile transition of various mudrocks based on the results of the tests it is shown that the brittle to ductile transition can be related to the overconsolidation ratio a relationship between normalized undrained shear strength and overconsolidation ratio is established in combination with this relationship a correlation between compressional wave velocity and apparent pre consolidation stress which accounts for both mechanical and chemical diagenesis may be used as a tool to evaluate possible leakage of hydrocarbon seals

co2 ecbm field tests in the ishikari coal basin of japan abstract the feasibility of extracting gas from coal seam while storing carbon dioxide underground was evaluated in japan a co2 ecbm project had begun near the town of yubari on the island of hokkaido in northern japan the primary coal seam of interest was a 5 6 m thick yubari coal seam located at the depth of 900 m a micro pilot test with a single well and multi well co2 injection tests involving an injection and production wells were carried out in the period between may 2004 and october 2007 there were a variety of tests conducted in the injection well including an initial water injection fall off test and a series of co2 injection and fall off tests although gas production rate was obviously enhanced by co2 injection water production rate was not clearly affected by co2 injection several injection tests suggested that injectivity of co2 into the virgin coal seam saturated with water was eventually increased as the water saturation near the injector was decreased by the injected co2 it was estimated that low injectivity of co2 was caused by the reduction in permeability induced by coal swelling n2 flooding test was performed in 2006 to evaluate the effectiveness of n2 injection on improving well injectivity the n2 flooding test showed that daily co2 injection rate was boosted but only temporarily moreover the permeability did not return to the initial value after co2 and n2 were repeatedly injected it was also indicated that the coal matrix swelling might create a high stress zone near to the injection well

effect of carbon dioxide sequestration on the mechanical properties of deccan basalt carbon dioxide sequestration is considered to be an efficient method of curbing the release of carbon dioxide emissions into the atmosphere and to mitigating corresponding effects on climate change in this regard basaltic rocks are among the potential repositories due to their ability to trap carbon dioxide in form of carbonate minerals a series of laboratory scale saturation experiments was conducted on three types of basalts that were collected from different horizons of the deccan volcanic province dvp india the basalt cores were treated in a saturation chamber for different exposure periods under low pressure and room temperature conditions a set of key mechanical physical and chemical properties of the pre and post treated samples were analyzed to identify saturation related changes the results show that exposure of the basalts to carbon dioxide has a strong effect on their strength however the extent of the effect is different for different types of basalts and is strongly controlled by the exposure time the mineralogical composition and rock texture x ray diffraction and scanning electron microscopy sem show that saturation leads to dissolution of the mafic minerals and precipitation of new carbonate minerals in the cracks and vesicles of the host rock these changes in the mineralogical content and the development of micro cracks in the samples are interpreted as being the primary factors that affect the loss of integrity in the rock

the formation and failure of natural dams of the numerous kinds of dams that form by natural processes dams formed from landslides glacial ice and late neoglacial moraines present the greatest threat to people and property landslide dams form in a wide range of physiographic settings the most common types of mass movements that form landslide dams are rock and debris avalanches rock and soil slumps and slides and mud debris and earth flows the most common initiation mechanisms for dam forming landslides are excessive rainfall and snowmelt and earthquakes landslide dams can be classified into six categories based on their relation with the valley floor type i dams 11 of 184 landslide dams from around the world that we were able to classify do not reach from one valley side to the other type ii dams 44 span the entire valley floor in some cases depositing material high on opposite valley sides type iii dams 41 move considerable distances both upstream and downstream from the landslide failure type iv dams 1 are rare and involve the contemporaneous failure of material from both sides of a valley type v dams 1 also are rare and are created when a single landslide sends multiple tongues of debris into a valley and forms two or more landslide dams in the same reach of river type vi dams 3 involve one or more failure surfaces that extend under the stream or valley and emerge on the opposite valley side many landslide dams fail shortly after formation in our sample of 73 documented landslide dam failures 27 of the landslide dams failed less than 1 day after formation and about 50 failed within 10 days over topping is by far the most common cause of failure the timing of failure and the magnitude of the resulting floods are controlled by dam size and geometry material characteristics of the blockage rate of inflow to the impoundment size and depth of the impoundment bedrock control of flow and engineering controls such as artificial spill ways diversions tunnels and planned breaching by blasting or conventional excavation glacial ice dams can produce at least nine kinds of ice dammed lakes the most dangerous are lakes formed in main valleys dammed by tributary glaciers failure can occur by erosion of a drainage tunnel under or through the ice dam or by a channel over the ice dam cold polar ice dams generally drain supraglacially or marginally by downmelting of an outlet channel warmer temperate ice dams tend to fail by sudden englacial or subglacial breaching and drainage late neoglacial moraine dammed lakes are located in steep mountain areas affected by the advances and retreats of valley glaciers in the last several centuries these late neoglacial dams pose hazards because 1 they are sufficiently young that vegetation has not stabilized their slopes 2 many dam faces are steeper than the angle of repose 3 these dams and lakes are immediately downslope from steep crevassed glaciers and near vertical rock slopes and 4 downstream from these dams are steep canyons with easily erodible materials that can be incorporated in the flow and increase flood peaks the most common reported failure mechanism is overtopping and breaching by a wave or series of waves in the lake generated by icefalls rockfalls or snow or rock avalanches melting of ice cores or frozen ground and piping and seepage are other possible failure mechanisms natural dams may cause upstream flooding as the lake rises and downstream flooding as a result of failure of the dam although data are few for the same potential energy at the dam site ownstream flood peaks from the failure of glacier ice dams are smaller than those from landslide moraine and structed earth fill and rock fill dam failures moraine dam failures appear to produce some of the largest downstream flood peaks for potential energy at the dam site greater than 1011 1012 joules differences in flood peaks natural dam failures appear to be controlled by dam characteristics and failure mechanisms

swelling induced volumetric strains internal to a stressed coal associated with co2 sorption abstract it is generally accepted that typical coalbed gases methane and carbon dioxide are sorbed both adsorbed and absorbed in the coal matrix causing it to swell and resulting in local stress and strain variations in a coalbed confined under overburden pressure the swelling interactions of gases within the coal matrix and the resultant changes in the permeability sorption gas flow mechanics in the reservoir and stress state of the coal can impact a number of reservoir related factors these include effective production of coalbed methane degasification of future mining areas by drilling horizontal and vertical degasification wells injection of co2 as an enhanced coalbed methane recovery technique and concurrent co2 sequestration such information can also provide an understanding of the mechanisms behind gas outbursts in underground coal mines the spatio temporal volumetric strains in a consolidated pittsburgh seam coal sample were evaluated while both confining pressure and carbon dioxide co2 pore pressure were increased to keep a constant positive effective stress on the sample the changes internal to the sample were evaluated by maps of density and atomic number determined by dual energy x ray computed tomography x ray ct early time images as soon as co2 was introduced were also used to calculate the macroporosity in the coal sample scanning electron microscopy sem and photographic images of the polished section of the coal sample at x ray ct image location were used to identify the microlithotypes and microstructures the co2 sorption associated swelling and volumetric strains in consolidated coal under constant effective stress are heterogeneous processes depending on the lithotypes present in the time scale of the experiment vitrite showed the highest degree of swelling due to dissolution of co2 while the clay kaolinite and inertite region was compressed in response the volumetric strains associated with swelling and compression were between 15 depending on the location although the effective stress on the sample was constant it varied within the sample as a result of the internal stresses created by gas sorption related structural changes sem images and porosity calculations revealed that the kaolinite and inertite bearing layer was highly porous which enabled the fastest co2 uptake and the highest degree of compression

co2 permeability of indian bituminous coals implications for carbon sequestration abstract the permeability of coal is one of the most critical parameters in estimating the performance of coal seams as methane reservoirs or carbon dioxide sinks the reservoir behaviour of coal offers many challenges for the long term planning of gas production performance and the drainage of water from reservoirs moreover heterogeneity in coal from basin to basin from seam to seam and within parts of the same seam makes the process more complex reservoir specific understanding is needed for the best possible estimation of its behaviour factors such as shrinkage swelling of coal matrix gas flow and slippage geomechanical changes cleat anisotropy and effective stresses control the flow behaviour of gases in coal studies of these aspects have gathered momentum in recent decades for different basins across the world however no research is available on swelling induced permeability characteristics or the role of effective stresses for gondwana coals in india considering the fairly high co 2 storage potential of indian coals bituminous coals of the barakar formation in jharia basin india were tested using gas phase co 2 under triaxial conditions this paper presents the results of changing effective stresses in terms of confining stresses and pore pressure incorporating the role of coal swelling with time on the flow pattern of gaseous co 2 corresponding to different depths of target coal seams coal was subjected to different confining stresses in a newly developed triaxial cell for each confinement co 2 was injected at different injection pressures to minimize the effects of temperature on the characteristics of the gas phase it was kept constant at 26 c throughout while use of the drained method of testing maintained the downstream pressure equal to one atmosphere the results showed that at low confinement increase in gas injection pressures leads to an initial decrease in permeability of coal which then becomes almost constant however at higher confinements the permeability increases with increasing injection pressure swelling in coal contributes to reduction of permeability the volumetric expansion in coal reduces the permeability with changing gas injection pressure during the initial confinement as the confining pressure is increased coal permeability reduces by one to two orders of magnitude finally an empirical relation accounting for the role of effective stresses and swelling on coal permeability is proposed for indian coals at lower effective stresses the logarithmic decline model is better suited while the exponential decline relationship fits the data better at effective stresses 12 mpa

carbon dioxide gas permeability of coal core samples and estimation of fracture aperture width abstract the structure of cleats or natural fractures in coal seams is an important factor affecting gas permeability coal seam permeabilities have been classified into fracture and matrix flows however fractures in coal seams are generally not regular and usually are discontinuous in addition it is difficult to definitively distinguish the fracture and matrix permeabilities and to measure the fracture widths or other necessary properties of fractures for permeability estimation typically gas permeability has been determined by using the darcy equation for incompressible fluid flow and homogeneous porous media even if the gas flow through fractures has different characteristics with respect to effective stress which is given by the confined stress minus the gas pressure in this study permeability measurements were carried out with a new procedure and methodology to estimate the fracture width in coal core samples this measurement method is an improvement on conventional permeability measuring methods in this research it was identified that fracture permeability can be estimated from measurements of gas flow rates in a limited small area using a pipe attachment on the end of the surface of the core finally a linear equation composed of fracture permeability and matrix permeability is presented

pool spacing in forest channels field surveys of stream channels in forested mountain drainage basins in southeast alaska and washington reveal that pool spacing depends on large woody debris lwd loading and channel type slope and width mean pool spacing in pool riffle plane bed and forced pool riffle channels systematically decreases from greater than 13 channel widths per pool to less than 1 channel width with increasing lwd loading whereas pool spacing in generally steeper step pool channels is independent of lwd loading although plane bed and pool riffle channels occur at similar low lwd loading they exhibit typical pool spacings of greater than 9 and 2 4 channel widths respectively forced pool riffle channels have high lwd loading typical pool spacing of 2 channel widths and slopes that overlap the ranges of free formed pool riffle and plane bed channel types while a forced pool riffle morphology may mask either of these low lwd loading morphologies channel slope provides an indicator of probable morphologic response to wood loss in forced pool riffle reaches at all study sites less than 40 of the lwd pieces force the formation of a pool we also find that channel width strongly influences pool spacing in forest streams with similar debris loading and that reaches flowing through previously clear cut forests have lower lwd loading and hence fewer pools than reaches in pristine forests

evaluation indexes of coalbed methane accumulation in the strong deformed strike slip fault zone considering tectonics and fractures a 3d geomechanical simulation study both the deformation and rupture characteristics of rocks are related to geomechanics in this paper we identify the evaluation indexes related to coalbed methane cbm accumulation in strongly deformed strike slip fault zones considering tectonics and fractures we found that fault scale the fault combination the tectonic stress the preservation conditions and fractures all have important effects on the cbm distribution areas near the large scale opening faults are unfavourable to the preservation of coalbed methane the distribution of gas wells with different capacities is influenced by tectonic extension and convergence a 3d geomechanical method was used to analyse the influence of the ribbon effect of strike slip faults on the cbm distribution due to the influence of the ribbon effect the tectonic stress presents a plane in situ stress heterogeneity which in turn will affect the gas well productivity we also calculated the integrated rupture rate if to characterize the degree of tectonic fracture development in the target coal reservoir the appropriate fracture development degree can improve the petrophysical properties of the coal reservoirs while maintaining good storage conditions such that the gas wells can achieve a higher production capacity this study is of great significance for the enrichment of the geomechanical theory of oil and gas exploration

adjustments in channel form sediment calibre and vegetation around check dams in the headwater reaches of mountain torrents calabria italy the structure and dynamics of vegetation in valley bottoms are both strongly associated with fluvial processes and landform dynamics all of these associations are disrupted by the installation of engineering control works we use survey and analysis methods developed previously to investigate the impact of the installation of check dams within the confined headwaters of steep seasonally flowing streams fiumaras in calabria southern italy on active channel form sediment calibre and the richness cover and development of riparian vegetation based on detailed field measurements along transects across the active channel estimates of indices of vegetation extent gcc development wch and their cross sectional variability coefficients of variation of both indices at each survey site cvgcc cvwch the number of species present ns channel shape w d the width depth ratio cross sectional area csa downstream gradient slope surface bed sediment calibre d50 and subsurface fine sediment content percentage less than 250 m by weight were obtained for 60 transects located immediately upstream u downstream d and at intermediate sites i around 20 check dams located in four different headwater catchments analysis of this data set suggests that statistically significant changes in channel form and sediment calibre upstream of check dams are associated with more consistent vegetation development across the active channel including an increase in species richness relative to other transects but notable increases in vegetation cover and development only arise where the physical characteristics of the channel are notably different from intermediate and downstream channels because of the naturally steep profile of the study torrents intermediate sections between check dams tend to be more similar in form to channels located immediately downstream of check dams than those located upstream leading to similar structural properties in the riparian vegetation the intermediate transects support considerably more species than downstream reaches but the conditions upstream of the check dams appear to be so favourable for riparian vegetation development that species richness exceeds that found in intermediate reaches despite the confined headwater locations these contrasts in form sediment and vegetation development around check dams are strong and consistent across the study catchments over riding more subtle contrasts in species richness and sediment calibre between catchments copyright 2009 john wiley sons ltd

characteristics and origins of coal cleat a review abstract cleats are natural opening mode fractures in coal beds they account for most of the permeability and much of the porosity of coalbed gas reservoirs and can have a significant effect on the success of engineering procedures such as cavity stimulations because permeability and stimulation success are commonly limiting factors in gas well performance knowledge of cleat characteristics and origins is essential for successful exploration and production although the coal cleat literature spans at least 160 years mining issues have been the principal focus and quantitative data are almost exclusively limited to orientation and spacing information few data are available on apertures heights lengths connectivity and the relation of cleat formation to diagenesis characteristics that are critical to permeability moreover recent studies of cleat orientation patterns and fracture style suggest that new investigations of even these well studied parameters can yield insight into coal permeability more effective predictions of cleat patterns will come from advances in understanding cleat origins although cleat formation has been speculatively attributed to diagenetic and or tectonic processes a viable mechanical process for creating cleats has yet to be demonstrated progress in this area may come from recent developments in fracture mechanics and in coal geochemistry

permeability of sub critical carbon dioxide in naturally fractured indian bituminous coal at a range of down hole stress conditions abstract understanding reservoir dynamics from a geotechnical and petrophysical perspective is essential for safe and steady fluid extraction transport or injection in the reservoir the recent approach on storage of anthropogenic greenhouse gases ghg for mitigation of climate change in the deep geologic reservoirs has led to fast paced research on resolving storage related issues a coal seam is one such target reservoir where co 2 may be injected for storage this may be coupled with the enhanced extraction of coalbed methane cbm it is known that the interaction of co 2 with coal induces hydro mechanical changes however detailed investigation is mandatory for site specific operation the lack of such studies on indian coal is the motivation for this research a naturally fractured coal specimen was chosen and the subcritical co 2 flow was maintained by monitoring the injection pressures and ambient temperature the variations in permeability under various scenarios were also investigated the results indicate that initial co 2 injection caused coal matrix swelling which took nearly 5 6 h of flow related sorption for maximum closure of the natural fractures linear variation in flow rate with the pressure gradient across the sample indicated laminar or darcian flow of co 2 through the coal fractures deeper coal seams have high confinements the co 2 permeability results for such in situ conditions indicated an exponential decline in naturally fractured coal due to increasing confining pressures the observed reduction of co 2 permeability with increase in gas inlet pressure is debated and may be attributed fully to matrix swelling or partly to the klinkenberg effect this study is vital for successful ghg sequestration in coal seams and for better understanding of the gas flow behaviour in the seams

gas migration of coal in front of a mining face considering crack evolution the analysis of gradual mechanical responses of coal and gas migration within the coal in front of a mining face is crucial to coal and gas outburst prevention and control in the present paper the stress distribution of an entire stope is numerically studied by flac3d the stress state and its development within coal in front of a mining face are analyzed and a simplified physics model is developed based on the simulation results the crack expansion process of a coal specimen under a quasi plane strain condition is studied using a coal solid gas coupled meso mechanics system that is imported into comsol for simulating the gas migration of coal in front of a mining face a self established solid gas coupling constitutive model which considers the gas pressure and gas adsorption is used the gas pressure gradient and speed of gas migration reach maximum values near the free sidewall which is in agreement with the field test results

effects of coarse woody debris and its removal on a channel affected by the 1980 eruption of mount st helens washington during the may 18 1980 eruption of mount st helens washington a pyroclastic surge introduced large volumes of coarse woody debris cwd and fine grained sediment to clearwater creek approximately 15 km northeast of the summit effects of controlled cwd removal on sediment storage substrate and pool frequency and volume were measured in four reaches each with three 200 m segments from 1982 to 1990 in each reach the upstream segment served as a control with no debris removal and cwd was totally and selectively removed from the other two segments unique among similar experiments are the large size and volume of cwd and the large inputs of fine grained sediment except for segments of two reaches that received debris torrents the clearwater channel thalweg scoured until 1985 in three reaches total debris removal caused additional scour and coarsening of the bed surface compared to segments with no or partial debris removal pools contracted from 1982 to 1985 and expanded afterward especially in control segments total debris removal apparently caused pools to become shallower and in segments of low sinuosity decreased the frequency of major pools habitat complexity decreased after total debris removal as indicated by a decrease in the standard deviation of residual depth and an increase in the size of substrate patches

spatiotemporal evolution of a unique preserved meandering system in central europe the morava river near litovel abstract rivers are naturally dynamic over time and space and respond to the variability of water and sediment inputs and to anthropogenic pressures that cause changes to the river s behaviour and form this study describes the evolution of part of the morava river and the kenick meander in the litovelske pomoravi protected area near the city of olomouc the research describes the historical development of the study area using aerial photos uav images and geodetic measurements long term measurements and imaging using uav technologies have allowed a large amount of information to be collected this information was used to study the kenick meander and the morava river significant lateral channel changes in the banks have occurred in the past and generated the kenick meander a significant event occurred in the spring of 2012 when high water levels were caused a rupture of a meander natural cutoff the water level was monitored in the kenick wood accumulation which formed in the kenick meander before and after the rupture monitoring the movement of wood in the river basin is particularly important because the movement of ice in the winter can cause blockage of the channel and subsequent flooding of water over the banks and into the surrounding communities

quantification of fluvial wood using uavs and structure from motion abstract fluvial wood is recognized as one of the key elements of riverine environments its importance role and potential related risks are widely considered and analysed still to characterize and measure wood elements in the field a large investment in terms of time and cost is normally required these activities are often carried out in complex and potentially dangerous environments in this context the use of unmanned aerial vehicles uavs provides a powerful alternative technology to traditional approaches in this work we propose a novel approach combining uav surveys with structure from motion sfm photogrammetry to quantify fluvial wood the proposed methodology was tested in the blanco river southern chile which was severely affected by the chaiten volcanic eruption in 2008 that delivered large quantities of wood to the channel an area of about 1 2 ha was surveyed using uav and field measurements a comparative analysis between the traditional field based and uav surveys was carried out to quantify the accuracy of the latter and to better understand the strengths and potential limitations of the proposed methodology results showed that differences between the two methodologies were about 13 for both single large wood elements and wood jam volumes moreover a sensitivity analysis applied to 12 different scenarios allowed us to define the measurement precision achieved using the orthomosaics and dems our results showed that the proposed approach is effective in terms of field and laboratory activities saving around half the time this study demonstrates that the combination of uav and sfm can yield accurate results covering large areas in less time and providing a powerful tool for performing repeated surveys and thus acquiring relevant information for wood budgets and wood dynamics in rivers

importance of fabric and composition on the stress sensitivity of permeability in some coals northern sydney basin australia relevance to coalbed methane exploitation fabric and composition of a series of upper permian high volatile to low volatile bituminous coals of the sydney basin have a marked effect on stress sensitivity of permeability and thus on the reservoir characteristics of the coal the coals vary in composition from end members of predominantly bright banded coal comprised mainly of the microlithotype vitrite and the maceral vitrinite to dull coal composed of significant amounts of ash inertinite group macerals and the microlithotype inertite the brighter coals are more extensively fractured with one or more commonly two or three regularly spaced fracture sets cleats spaced at 5 20 m fusinite and semifusinite common macerals in the dull coals are characterized by phyteral porosity mainly cell lumens and fabric selective intergranular porosity the permeability of tested samples varies significantly with composition and effective stress the fabric of the samples is the most important factor in determining permeability and stress sensitivity of permeability coals with the highest permeability are those with at least one well developed throughgoing fracture set these samples generally include abundant vitrite bands the lowest permeability samples are nonbanded with an attrital fabric and significant authigenic mineralization at copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received april 1 1996 revised manuscript received december 4 1996 final acceptance june 16 1997 2department of earth and ocean sciences university of british columbia vancouver bc v6t 1z4 canada this study was financially supported by a grant from csiro syndal and by the earth resources foundation university of sydney samples and some data were provided by pacific power ltd sydney i thank paul gamson formerly of csiro for overseeing the permeability analyses and facilitating some of the study i thank k wright of the earth resources foundation university of sydney j enever of csiro j c close of meridian oil and chris clarkson of university of british columbia for their comments on an earlier draft of this paper reviewers andrew scott roger taylor and w ayers are thanked for their thoughtful comments

quasi static fault growth and cracking in homogeneous brittle rock under triaxial compression using acoustic emission monitoring this paper describes the localization of deformation acceleration in the period prior to dynamic failure in hornblende schist rock under triaxial compression using acoustic emission ae monitoring rather than stabilize the failure process by controlling axial stress to maintain a constant rate of ae for monitoring ae hypocenters as in previous works e g lockner et al 1991 we have instead developed a rapid multichannel data collection system this enables us to elucidate the dynamics of fault nucleation under condition of constant stress creep loading which is a better approximation to low strain rate condition in the earth and allows both quasi static and dynamic crack growth to occur the waveforms of more than 8000 ae events which occurred mainly during a 15 s period were recorded on 32 channels with a sampling rate of 50 ns and mask time of 200 s hypocentral locations of ae sources revealed that the fault initiated at one end of the core and then propagated into the unfaulted rock with a process zone fault front of intense cracking we found that there were two different processes operating during the quasi static nucleation of a shear fault namely a process zone in front of the fault tip and a wake of damage zone following the process zone the process zone had the following features 1 major tensile cracking 2 low b value and fewer larger events and 3 strong self excitation the mechanism of crack interaction and fault growth was therefore a mutual enhancement on dilatation due to tensile cracking on the other hand the damage zone was characterized by 1 major shear cracking 2 low b value and more larger events and 3 weak self excitation indicating that in the damage zone following the development of a shear fault linkage between cracks became the major mechanism of crack interaction and fault development the mutual changes of b value and self exciting strength observed in our experiments seem to occur as a result of the hierarchy of fault growth which was not observed under slowed down loading conditions therefore our experimental results under a realistic approximation of the dynamic condition of the earth are meaningful for the problems of earthquakes as well as rock bursts

permeability changes in coal analytical modeling abstract permeability changes can be very large during depletion of coalbed methane wells up to 100 times in the san juan basin analytic models of permeability increase during depletion are accessible easy to use and practical they are more transparent and less complicated than coupled numerical models however there are minor differences between the analytic models and these are reviewed here there are also discrepancies in attempting to match field data which is the final test of a model and these are discussed two different sets of san juan data have been modeled after suppressing the pressure dependent permeability with reasonably consistent reservoir parameters the matching parameters appear to be justifiable the small porosities do not seem to be ruled out by reservoir experts and the changes of elastic parameters including pore volume compressibility with depletion do not seem unreasonable the analytic models are used in reservoir simulators to model and predict injection of greenhouse gases in coal seams only when we can match the permeability increase of coalbed methane wells during depletion will we have the confidence to use the analytic models in reservoir simulators to match or predict sequestration of greenhouse gases such as co2

the effects of stress and fracturing on permeability of coal abstract this paper examines the changes in structure and permeability of coal under the stress conditions experienced around longwall faces the effect of fracturing on permeability of coal is discussed and the stress permeability relationship for fractured coal is compared with that of non fractured coal an empirical relationship between stress and permeability for coal is derived from the experimental data which relates the stress permeability behaviour of coal to its rank through the compressibility of the coal itself

assessing tree ring carbon and oxygen stable isotopes for climate reconstruction in the canadian northeastern boreal forest abstract in this study we analyzed stable isotopes of oxygen 18o and carbon 13c of five black spruce picea mariana mill bsp trees growing in the quebec boreal forest we then produced the first dendroisotopic series covering the last two centuries 1800 2003 for this region where climatic records are particularly scarce and of short duration our aim was to evaluate the isotope sensitivity to climate and their potential as proxies for past climate conditions the 18o results show a strong coherence between all trees indicating that these values express a homogenous response at the site scale for the 13c series slight inter tree differences suggest the influence of micro site conditions isotopic values were compared to climatic data for the period 1944 2003 these statistical analyses indicate that the 13c and 18o ratios are directly influenced by summer maximum temperatures but also correlate with parameters that integrate temperatures and moisture status in all cases the climate effects on 13c values are weaker than the ones recorded by the 18o series moreover because the 18o and 13c values are sensitive to climatic variables that are linked and commonly associated in typical subarctic climate ambiances warm dry cold wet the patterns of their joint response show stronger correlations with climatic parameters then a temperature reconstruction was developed based on a regression model that calibrates the combined 13c and 18o series against summer maximum temperature tmaxjja the reconstructed summer temperatures indicates that the first half of the 19th century was the coldest period in the past 200 years and that a steadily change throughout milder conditions started in the early 1940 s these trends are consistent with other reconstructed values from independent proxies available for the same region this research confirms that c and o dendroisotopic series of black spruce trees in high latitudes can document adequately past climatic conditions

patterns and processes of wood debris accumulation in the queets river basin washington field surveys in the 724 km 2 queets river basin on the west slope of the olympic mountains in nw washington reveal basin wide patterns of distinctive wood debris wd accumulations that arise from different mechanisms of wd recruitment hydraulic geometry and physical characteristics of wd individual pieces of wd in an accumulation or jam can be separated into key racked and loose members ten types of wd accumulations are identified based on the mode of recruitment and the orientation of key racked and loose debris relative to the channel axis although some types of wd accumulation have few geomorphic effects others form stable in stream structures that influence alluvial morphology at both subreach and reach length scales ranging from less than 1 to greater than 10 channel widths in the queets river stable accumulations of wd directly influence channel anabranching planform geometry flood plain topography and establishment of long term riparian refugia for old growth forest development the classification of wood debris accumulations in the queets river basin is based on physical observations that offer a template potentially applicable to other forested mountain regions d 2002 elsevier science b v all rights reserved

role of tree dams in the construction of pseudo terraces and variable geomorphic response to floods in little river valley virginia geomorphic response to a 1985 flood in little river valley northern virginia was different in magnitude and style from the largest historic flood in the same valley in 1949 the primary geomorphic activity during the 1985 flood was severe bank erosion and channel gravel deposition rather than the debris flow and avalanching of the 1949 event an unusual and widespread phenomenon of the recent flood was that large trees eroded and transported by the floodwater were aligned parallel to the river banks and at isolated sites were braced and stacked against trees still standing on the floodplain lateral barriers or dams created from these displaced trees allowed the channel to be locally aggraded above the level of the flood plain in these reaches little if any river gravel was deposited on the floodplain even though the adjacent channel floor was raised well above that surface the river has now shifted around the filled segments leaving flat isolated surfaces underlain by channel gravel standing above the level of the modern floodplain these features may be mistaken for terraces alter they become vegetated and the trees bracing the gravels decay interpreting these surfaces to be terrace remnants would lead to a faulty reconstruction of geomorphic history in the little river valley and other valleys where floodplain morphology is controlled by infrequent flood events

the influence of coarse woody debris on gravel beach geomorphology abstract coarse woody debris cwd is an important component of fluvial systems affecting in channel hydrology and sediment storage which in turn controls channel geometry and evolution the role of coarse woody debris in coastal geomorphology is an emerging research field and this study investigates its role on mixed sand and gravel beach systems a case study approach is used whereby two field areas in wellington new zealand each with two distinct beaches with differing wood accumulations were investigated through field surveying it is found that on gravel beaches cwd is most important during storm events where it causes the berm crests to be 0 5 1 0 m higher than on unwooded beaches as well as making the beachface twice as steep during calm periods the berm appears to be inactive as non storm waves can only rework the lower beachface a review of the literature indicates that on sandy beaches cwd is most important in the post storm recovery of beach systems the same wave event that causes beach erosion also deposits the cwd during calm periods the woody material is a trap for sand being transported along the beachface and therefore aids in re establishing foredune systems the differing sediment composition between sandy and gravelly beaches drives their morphological response to storm events and in turn determines how cwd interacts with the beach profile

combining historical and process perspectives to infer ranges of geomorphic variability and inform river restoration in a wandering gravel bed river restoration approaches such as dam removal and channel reconstruction have moved beyond the realm of small streams and are being applied to larger rivers this development has substantial economic and ecological implications but may test gaps in our understanding of larger river systems and of restoration science we examine how information about historical ranges of geomorphic variability can inform stream restoration in the context of the clark fork river montana focusing on a study reach where one of the largest restoration projects to date was implemented upstream of the recently removed milltown dam analysis of historical sources and aerial photographs of the clark fork river s pre mining mining and more recent history suggest that a wandering channel pattern has persisted despite variations in sediment supply and transport capacity predictive metrics for channel pattern also suggest a wandering pattern transitional between braided and meandering in this geomorphic setting these analyses suggest that the creation of a single thread meandering channel which incorporates structures to limit erosion and channel movement is inconsistent with the historical range of variability in this reach the perils of restoring channels to a condition different than the historical range of variability for their geomorphic setting were illustrated on the clark fork by flood induced avulsions of the restored channel that occurred soon after project construction application of an experimental approach to restoration founded on the method of multiple working hypotheses provides a means for embracing uncertainty can maximize the potential for site specific restoration success and can foster advances in restoration science copyright 2012 john wiley sons ltd

logjam controls on channel floodplain interactions in wooded catchments and their role in the formation of multi channel patterns the role of wood in the formation and maintenance of complex dynamic floodplain surfaces is important and to date has received relatively limited attention compared to in channel habitat processes this paper explores the role of logjams as important agents of channel floodplain interaction we draw on a specific case study as well as examples from the literature to show that although the processes of interaction differ the resulting dynamic floodplain patchwork is a common feature of rivers with logjams in addition we contend that the presence of logjams is an important factor in the evolution and maintenance of multiple channel patterns in both montane and lowland river environments these observations have important implications for the definition of reference targets for river restoration the specific results of this research show 1 the presence of a range of types of multiple channel network dissecting the floodplains of low order channels that are strongly associated with the presence of logjams 2 the relatively rapid formation of floodplain channels following logjam formation 3 the dynamic nature of logjams within headwater channels on both seasonal and annual timescales that lead to a highly dynamic habitat mosaic on the floodplain surface 4 an increased frequency of overbank flooding and high rates of floodplain sediment accumulation upstream of logjams and along floodplain channel networks that create the complex topography observed in the case study forested floodplains

interaction analysis for co2 geological storage and underground coal mining in ordos basin china abstract the co 2 geological storage in ordos basin and coal mining activities occurring simultaneously at the same location is a highly challenging coupled thermo hydro mechano chemical thmc problem to address this problem an in house program named aeea coupler was developed by linking two commercial software packages simulia abaqus and schlumberger eclipse both of which are widely used and highly recognized in their respective fields the applicability and accuracy of the developed coupler were tested by benchmark studies a coupled multi physics analysis was conducted based on real formation data of the ordos and shenhua ccs demonstration project with an injection rate of 0 1 mtpa million tonnes per annum a larger injection rate of 1 0 mtpa was also investigated to explore the potential for the commercialization of large scale ccs projects in the area the primary conclusions that were obtained from the numerical simulations are as follows a the pore pressure and displacement at the top of the reservoir increase with co 2 injection and the displacement continues to increase even after the termination of the co 2 injection due to the coal mining activity b the displacement of the wellbore peaks at the coal seam floor where the axial strain of the well soars abruptly our work suggests that the distance between coal pillars should be at least 90 m to ensure that the mises stress of the casing is below the designed safe value c the tensile stress and shearing stress increase significantly in the caprock as a result of the coupling of the two engineering activities therefore damages in the caprock occur more easily d after co 2 injection only the strata with a depth of less than 769 m are affected by the coal mining activity e the combined activities achieve a surface subsidence reduction comparable to that of only coal mining finally several recommendations are given regarding the actual engineering implementation of the combined activities

influence of carbon dioxide on coal permeability determined by pressure transient methods abstract the permeability of coal samples from pittsburgh seam was determined using carbon dioxide as the flowing fluid the confining pressure was varied to cover a wide range of depths the permeability was determined as a function of exposure time of carbon dioxide while the confining stress was kept constant the porosities of the coal samples were found to be very low and most of the samples had porosities less than 1 the permeability of these coal samples was very low less than 1 d since the objective of this study was to investigate the influence of co2 exposure on coal permeability it was necessary to increase the initial permeability of the coal samples by introducing a fracture a longitudinal fracture was induced mechanically and ct scans were taken to ensure that the fracture was present throughout the sample and that the sample was not damaged otherwise during the process in this study the permeability of coal was determined by using pressure transient methods two types of pressure pulses were used a spike and sine 6 pressure transients it was first established that the permeability of fractured coal samples did not change with exposure time when an inert gas argon was used as the fluid medium in the experiments however the permeability of coal samples decreased significantly when carbon dioxide was used as the fluid medium this reduction can be attributed to the coal swelling phenomenon the results show that the permeability reduction in fractured coal samples can be over 90 of the original value and the exposure time for such reductions can range from 1 5 days up to a week typically about 2 days under laboratory conditions the permeability decreased significantly with the increase in confining pressure the higher confining pressure appears to close internal fractures causing a reduction in permeability

episodic wood loading in a mountainous neotropical watershed abstract the upper rio chagres drains 414 km2 of steep mountainous terrain in central panama a tropical air mass thunderstorm on 10 july 2007 produced a flood across the basin that peaked at 720 m3 s 1 at a headwaters gage draining 17 5 km2 and 1710 m3 s 1 at a downstream gage draining 414 km2 the storm also triggered numerous landslides in the upper basin which facilitated the formation of large logjams along portions of the channel where transport capacity of wood was reduced by a change in channel geometry such as a bend or channel expansion during field work in february 2008 we characterized three jams with surface areas of 400 2450 m2 two of these jams resulted in storage of substantial 1100 8200 m3 sediment wedges upstream we returned to these sites in march 2009 to document changes in the logjams and sediment storage drawing on observations made in the basin since 2002 and site visits during 2008 and 2009 we suggest that jams such as these last two years or less we propose that wood dynamics in the upper chagres alternate between brief periods of moderate wood load in the form of large logjams and much longer periods of essentially no wood load a situation that contrasts with the more consistent wood loads in catchments of similar size in temperate environments and with limited studies of more consistent wood load in tropical catchments with no landslides

islands in a european mountain river linkages with large wood deposition flood flows and plant diversity abstract vegetated islands are characteristic landforms of braided mountain rivers long term observations and recent morphological and botanical surveys conducted in the gravel bed czarny dunajec polish carpathians were used to determine the processes and patterns governing initiation and development of islands and their floristic complexity moreover dendrochronologically estimated years of island inception were compared with the timing and magnitude of flood flows in the period 1970 2011 to infer about controls on the formation and persistence of islands in the river in the high energy braided river islands originate as a result of deposition of large vegetative particles mostly large wood on gravel bars and the associated vegetative regeneration of living wood or the growth of seedlings and saplings in the shelter of wood accumulations tree ring dating of the largest trees growing in particular zones of building and established islands indicated a predominant upstream island growth in the river it results from repeated accumulation of living wood on the head of islands and its subsequent regeneration and contrasts with the progressive downstream growth of islands in the rivers supplied with large stable logs of the tree species without the capability to re sprout the lack of islands from the years 1982 1996 most likely reflects the removal of relatively young islands by two major floods in the 1990s which were however unable to destroy older and larger islands after 1997 the occurrence of low to moderate floods facilitated the formation and persistence of islands the plant inventory demonstrated that species richness increased non linearly with the increasing age area and shoreline length of islands islands supported more plant species than the riparian forest and attained comparable species richness at an early stage of development fast developing dynamic and supporting rich plant communities islands contribute highly to the overall floristic complexity of the river corridor and their re establishment should be viewed as an important factor in the restoration of hydromorphologically degraded mountain rivers

volumetric strain associated with methane desorption and its impact on coalbed gas production from deep coal seams the permeability of deep 1000 m 3300 ft coal seams is commonly low for deep coal seams significant reservoir pressure drawdown is required to promote gas desorption because of the langmuir type isotherm that typifies coals hence a large permeability decline may occur because of pressure drawdown and the resulting increase in effective stress depending on coal properties and the stress field during production however the permeability decline can potentially be offset by the permeability enhancement caused by the matrix shrinkage associated with methane desorption the predictability of varying permeability is critical for coalbed gas exploration and production well management we have investigated quantitatively the effects of reservoir pressure and sorption induced volumetric strain on coal seam permeability with constraints from the adsorption isotherm and associated volumetric strain measured on a cretaceous mesaverde group coal piceance basin and derived a stress dependent permeability model our results suggest that the favorable coal properties that can result in less permeability reduction during earlier production and an earlier strong permeability rebound increase in permeability caused by coal shrinkage with methane desorption include 1 large bulk or young s modulus 2 large adsorption or langmuir volume 3 high langmuir pressure 4 high initial permeability and dense cleat spacing and 5 low initial reservoir pressure and high in situ gas content permeability variation with gas production is further dependent on the orientation of the coal seam the reservoir stress field and the cleat structure well completion with injection of n2 and displacement of ch4 only results in short term enhancement of permeability and does not promote the overall gas production for the coal studied

laboratory measurement of two phase flow parameters in rock joints based on high pressure triaxial testing the accurate flow measurement of each individual phase is important in unsaturated flow through rock joints where both air and water phases flow together an increase in the quantity of one fluid phase decreases the relative permeability of the other phase the relative permeability is important in numerical models to analyze the risk of ground water inundation and uncontrollable gas flows in underground excavations in jointed rock a new apparatus the high pressure two phase triaxial apparatus hptpta has been designed for examining the strength and coefficient of permeability characteristics of fractured and intact rocks under two phase flows in single phase triaxial equipment the rock specimen is subjected to a single fluid flow either water oil or gas through the fractures in the hptpta two fluids e g water 1 air water 1 oil and oil 1 air can be forced to flow through the specimen and the flow rates of the fluids can be measured independently the scope of tests that can be carried out in this apparatus is wide including the evaluation of 1 stress strain behavior subject to internal fluid flow 2 relative permeability of each fluid phase under different degrees of saturation and 3 the associated volume change of the specimen in this paper the design concepts of the hptpta and the results based on the testing of fractured rock specimens are discussed the laboratory results are compared to a simplified mathematical model developed by the writers based on the laboratory results it is shown that the well known darcy s law can be modified for estimating the two phase flow rates using the relative permeability concept

large wood lw 3d accumulation mapping and assessment using structure from motion photogrammetry in the laboratory abstract a structure from motion sfm photogrammetry based methodology for precise mapping of large wood lw accumulations in fluvial systems is presented the technique may be useful for routine inventory and rapid volume estimation of complex lw structures that tend to divert or obstruct flow in rivers our methodology is validated by means of laboratory experiments ranging from elementary to complex arrangements of lw components and organic fine material ofm seven experimental setups were used as the basis for i manual approximations of 2 5d and 3d geometric reference volumes ii 2 5d volume models based on mesh geometry iii a closed watertight 3d mesh from an unorganized point cloud and iv estimates of porosity a commercially available sfm photogrammetry software package pix4dmapper was used for point cloud and simplified mesh generation in order to obtain more precise volumes 3d surface models are required accordingly we generated 3d watertight mesh models of the unorganized point cloud using the screened poisson surface reconstruction psr technique the pix4d volume tool 2 5d resulted in an overestimation 2 9 to 52 7 of the geometric volume 3d due to the convex hull approximation of the geometry normal to the surface plane psr 3d resulted in more precise volumes showing deviations from the geometric volume 3d in a range of 15 9 to 10 6 as the algorithm could capture concavities and involuted surfaces on the accumulation assuming that the difference between 3d and 2 5d volume models represents many of the voids visible within or on the surface of the deposit this volume can be used as an estimate of porosity our assessment suggests that image based sfm methodology is well suited for further investigations in lw research due to its time and cost efficiency in comparison with other conventional surveying techniques the methodology can be used to generate high quality point cloud and mesh models of log jam formations these may be used by river managers and researchers to quantify accumulation volume and thus gain a better understanding of lw composition and the influence of wood geometry on hydraulic flow conditions

riparian vegetation and island formation along the gravel bed fiume tagliamento italy after more than 300 years of river management scientific knowledge of european river systems has evolved with limited empirical knowledge of truly natural systems in particular little is known of the mechanisms supporting the evolution and maintenance of islands and secondary channels the dynamic gravel bed fiume tagliamento italy provides an opportunity to acquire baseline data from a river where the level of direct engineering intervention along the main stem is remarkably small against a background of a strong alpine to mediterranean climatic and hydrological gradient this paper explores relationships between topography sediment and vegetation at eight sites along the active zone of the tagliamento a conceptual model of island development is proposed which integrates the interactions between large woody debris and vegetation geomorphic features sediment calibre and hydrological regime islands may develop on bare gravel sites or be dissected from the floodplain by channel avulsion depositional and erosional processes result in different island types and developmental stages differences in the apparent trajectories of island development are identified for each of the eight study sites along the river the management implications of the model and associated observations of the role of riparian vegetation in island development are considered in particular the potential impacts of woody debris removal riparian tree management regulation of river flow and sediment regimes and changes in riparian tree species distribution are discussed

deformation failure and permeability of coal bearing strata during longwall mining abstract to mitigate water shortage a few groundwater reservoirs are being built at the daliuta coal mine shaanxi province china it is essential to investigate the deformation failure and permeability of coal bearing strata during longwall mining and their influences on the construction of groundwater reservoirs in this paper the local geology was introduced briefly and the complete stress strain and permeability for different rock samples were investigated using laboratory experiments and then a three dimensional coupling model between stress and permeability was proposed after that a series of numerical simulation was performed to investigate the dynamics of stress permeability coefficient using flac3d it turns out that due to the relatively low mechanical strength of the coal bearing strata at the daliuta coal mine there are only two zones above the goaf that is caving zone and fracture zone and the fracture zone extends directly to the surface the rock mass permeability is closely related to the stress strain and the permeability decreases with the rise of stress in the stage of elastic deformation while it increases significantly in the stages of plastic deformation and failure the maximum value of permeability coefficient appears in the stage of strain softening and the value varies greatly with the rock lithology during the advancement of longwall face the redistribution range is much wider for permeability than for rock failure and the permeability is the largest on the periphery of goaf rock mass with increased permeability is horizontally oval shaped and vertically saddle shaped the permeability of coal seam roof and floor experiences three stages decrease increase and gradual recovery during coal mining the results are in good agreement with those of physical modeling and field observation the outcomes may contribute to the site selection and construction of the groundwater reservoir at the daliuta coal mine

fluvial islands first stage of development from nonmigrating forced bars and woody vegetation interactions abstract fluvial islands can develop from the channel bed by interactions between pioneer trees and bars although vegetation recruitment and survival is possible on all bar types it is easier for trees to survive on nonmigrating bars developed from a change in channel geometry or to the presence of a steady perturbation this field study details the first stages of development of a vegetated mid channel nonmigrating or forced bar and its evolution toward an island form over six years analysis of bed topographical changes vegetation density and roughness scour and fill depths sediment grain size and architecture and excess bed shear stress highlighted a specific signature of trees on topography and grain size segregation two depositional processes combining the formation of obstacle marks and upstream shifting deposition of sediments led to the vertical accretion of the vegetated bar during the first stage of the bar accretion bedload sediment supply coming from surrounding channels during floods was identified as a key process modulated by the presence of woody vegetation and a deflection effect induced by the preexisting topography grain size segregation between vegetated and bare areas was also highlighted and interpreted as an important process affecting the development of surrounding channels and the degree of disconnection and hence the speed of development of a growing island the heterogeneity of bedload supply can explain why sediment deposition and density of trees are not strictly related a general conceptual model detailing the first stages of evolution from a bar to an established island is proposed for relatively large lowland rivers

improving the co2 well injectivity and enhanced coalbed methane production performance in coal seams abstract this paper reports on the performance comparison for different co2 ecbm schemes in relatively thin unminable seams typical of northern appalachian coal basin using a horizontal well configuration numerical simulations based upon public domain coalbed reservoir properties indicated that injection of pure co2 is likely to result in only limited incremental methane recovery if any over primary recovery due to the low injection rates that can be achieved on the other hand the presence of the nitrogen component in the injected gas stream is capable of improving the efficiency of enhanced methane recovery significantly without compromising the net co2 injection rates as a result of improved injectivity over pure co2 injection there is however a trade off between incremental methane recovery and produced gas purity due to early nitrogen breakthrough

wood mediated geomorphic effects of a jokulhlaup in the wind river mountains wyoming a jokulhlaup burst from the head of grasshopper glacier in wyoming s wind river mountains during early september 2003 five reaches with distinct sedimentation patterns were delineated along the dinwoody creek drainage this paper focuses on a portion of the jokulhlaup route where erosion of the forested banks created 16 large logjams spaced at longitudinal intervals of tens to hundreds of meters aggradation within the main channel upstream from each logjam created local sediment wedges and the jams facilitated overbank deposition during the jokulhlaup field surveys during 2004 and 2006 documented logjam characteristics and associated erosional and depositional features as well as initial modification of the logjams and flood deposits within the normal seasonal high flow channel overbank deposits have not been altered by flows occurring since 2003 field measurements supported three hypotheses that i logjams present along the forested portions of the jokulhlaup route are larger and more closely spaced than those along adjacent otherwise comparable stream channels that have not recently experienced a jokulhlaup ii logjams are not randomly located along the jokulhlaup route but instead reflect specific conditions of channel and valley geometry and flood hydraulics and iii the presence of logjams facilitated significant erosional and depositional effects this paper documents a sequence of events in which outburst floodwaters enhance bank erosion and recruitment of wood into the channel and thus the formation of large logjams these logjams sufficiently deflect flow to create substantial overbank deposition in areas of the valley bottom not commonly accessed by normal snowmelt peak discharges and through this process promote valley bottom aggradation and sediment storage changes in the occurrence of glacier outburst floods thus have the potential to alter the rate and magnitude of valley bottom dynamics in these environments which is particularly relevant given predictions of worldwide global warming and glacial retreat processes observed at this field site likely occur in other forested catchments with headwater glaciers

predicting natural channel patterns based on landscape and geomorphic controls in the columbia river basin usa 1 based on known relationships of slope discharge valley confinement sediment supply and sediment caliber in controlling channel patterns we developed multivariate models to predict natural channel patterns across the 674 500 km2 columbia river basin usa we used readily available geospatial data sets to calculate reach slopes 2 year flood discharge and valley confinement as well as to develop hypothesized landscape level surrogates for sediment load and caliber relative slope percent of drainage area in alpine terrain and percent of drainage area in erosive fine grained lithologies using a support vector machine svm classifier we found that the four channel patterns were best distinguished by a model including all variables except valley confinement 82 overall accuracy we then used that model to predict channel pattern for the entire basin and found that the spatial distribution of straight meandering anabranching and braided patterns were consistent with regional topography and geology a simple slope discharge model distinguished meandering channels from all other channel patterns but did not clearly distinguish braided from straight channels 68 overall accuracy addition of one or more of the hypothesized sediment supply surrogates improved prediction accuracy by 4 14 over slope and discharge alone braided and straight channels were most clearly distinguished on an axis of relative slope whereas braided and anabranching channels were most clearly distinguished by adding percent alpine area to the model

interactions between instream wood and hydrogeomorphic development within recently deglaciated streams in glacier bay national park alaska the physical and structural characteristics of instream wood were examined within five streams that represented 200 years of stream development following glacial recession within glacier bay national park alaska wood characteristics altered with watershed age as terrestrial succession progressed and wood was recruited into the riverine environment the influence of wood characteristics on the development of geomorphic diversity and hydraulic variability within the streams were assessed using detailed habitat mapping sediment analysis and hydraulic assessment using an acoustic doppler current profiler at a number of transects upstream downstream and adjacent to wood results show that the size complexity and orientation of wood accumulations are the main drivers in determining the degree of influence instream wood have on stream geomorphic and hydraulic complexity adjacent terrestrial vegetation must be of a sufficient stage of development in terms of size and maturity in order to elicit significant hydrogeomorphic changes to benefit aquatic biota such as fish macroinvertebrates and plants

adsorption kinetics of co2 ch4 and their equimolar mixture on coal from the black warrior basin west central alabama abstract laboratory experiments were conducted to investigate the adsorption kinetic behavior of pure and mixed gases co 2 ch 4 approximately equimolar co 2 ch 4 mixtures and he on a coal sample obtained from the black warrior basin at the littleton mine twin pine coal company jefferson county west central alabama the sample was from the mary lee coal zone of the pottsville formation lower pennsylvanian experiments with three size fractions 45 150 m 1 2 mm and 5 10 mm of crushed coal were performed at 40 c and 35 c over a pressure range of 1 4 6 9 mpa to simulate coalbed methane reservoir conditions in the black warrior basin and provide data relevant for enhanced coalbed methane recovery operations the following key observations were made 1 co 2 adsorption on both dry and water saturated coal is much more rapid than ch 4 adsorption 2 water saturation decreases the rates of co 2 and ch 4 adsorption on coal surfaces but it appears to have minimal effects on the final magnitude of co 2 or ch 4 adsorption if the coal is not previously exposed to co 2 3 retention of adsorbed co 2 on coal surfaces is significant even with extreme pressure cycling and 4 adsorption is significantly faster for the 45 150 m size fraction compared to the two coarser fractions

effects of coarse woody debris on morphology and sediment storage of a mountain stream system in western oregon effects of coarse woody debris cwd on channel morphology and sediment storage were investigated at five sites representative of first order to fifth order streams in the steep and bedrock confined stream first second order interaction between the channel and cwd was limited except where breakage upon falling produced cwd pieces shorter than channel width channel widening steepening and sediment storage associated with cwd were observed predominantly in third to fifth order streams variation in channel width and gradient was regulated by cwd in the fifth order stream most of the cwd pieces derived from the riparian forest interacted directly with the channel without being suspended by sideslopes in this system cwd promoted lateral channel migration but sediment storage was temporary with annual release and capture

reconstructing the development of sampled sites on fluvial island surfaces of the tagliamento river italy from historical sources in parallel with research on surface sediment characteristics of evolving island features patches along an island braided reach of the tagliamento river italy the present research reconstructed the development of the sampled sites using historical information coupled with field measurements since any field sediment sampling programme inevitably focuses on small areas of the order of a few metres the historical sources were assessed bearing in mind their spatial resolution and geographical accuracy in relation to the size of the sampled sites and the information they could provide regarding the historical evolution of those sites the analysis combined four sources of information i river stage records revealed flood events that had the potential to reset bar surfaces and float in wood and seeds to initiate vegetation colonization ii oblique ground photographs identified areas of the river s active corridor where riparian vegetation colonization appeared to have been initiated by specific flood events iii dendrochronology was used to estimate the age of sampled sites iv field measured geographical locations of the sampled sites were combined with historical vertical areal imagery to further establish sampling site age and changes in vegetation cover from 1944 to 2012 a chronosequence of sampled sites 0 2 8 12 40 years was established vegetation colonization and island development showed a statistically significant development trajectory among sites of each age across the 40 year period following formative floods in 1965 1966 2000 2004 and a flow pulse in 2010 the trajectory progressed through pioneer and building island stages until vegetated areas became part of established islands evidence from the younger sites indicates that the pioneer island phase lasts up to eight years evidence from the oldest site indicates a building island phase lasting a maximum of 30 years but probably a lot less copyright 2014 john wiley sons ltd

wood storage in three mountain streams of the southern andes and its hydro morphological effects this study analyses large wood lw storage and the associated effects on channel morphology and flow hydraulics in three third order mountain basins drainage area 9 12 km2 covered in old growth nothofagus forests ranging from the temperate warm chilean andean cordillera to the sub antarctic tierra del fuego argentina amount characteristics and dimensions of large wood 10 cm diameter 1 m long were recorded as well as their effects on stream morphology hydraulics and sediment storage results show that major differences in lw abundance exist even between adjacent basins as a result of different disturbance histories and basin dissection massive lw volumes i e 1000 m3 ha 1 can be reached in basins disturbed by fires followed by mass movements and debris flows potential energy dissipation resulting from wood dams is about a quarter of the total elevation drop in two streams with a gross sediment volume stored behind wood dams of around 1000 m3 km 1 which appears to be of the same order as the annual sediment yield finally the presence of wood dams may increase flow resistance by up to one order of magnitude copyright 2007 john wiley sons ltd

creating and coupling a high resolution dtm with a 1 d hydraulic model in a gis for scenario based assessment of avulsion hazard in a gravel bed river abstract in this paper we explore the development and assimilation of a high resolution topographic surface with a one dimensional hydraulic model for investigation of avulsion hazard potential on a gravel bed river a detailed channel and floodplain digital terrain model dtm is created to define the geometry parameter required by the 1d hydraulic model hec ras the ability to extract dense and optimally located cross sections is presented as a means to optimize hec ras performance a number of flood scenarios are then run in hec ras to determine the inundation potential of modeled events the post processed output of which facilitates calculation of spatially explicit shear stress and level of geomorphic work specific stream power per unit bed area for each of these further enhancing this scenario based approach the dtm is modified to simulate a large woody debris lwd jam and active channel sediment aggradation to assess impact on innundation and under previously modeled flow conditions the high resolution dtm facilitates overlay and evaluation of modeled scenario results in a spatially explicit context containing considerable detail of hydrogeomorphic and other features influencing hydraulics bars secondary and scour channels levees this offers advantages for i assessing the avulsion hazard potential and spatial distribution of other hydrologic and fluvial geomorphic processes and ii exploration of the potential impacts of specific management strategies on the channel including river restoration activities