the effects of large organic debris on sediment processes and stream morphology in vermont abstract research conducted on a small third order stream in the green mountains of vermont suggests that large organic debris lod has an important influence on areal sorting and storage of sediment spacing of pool riffle sequences and channel geometry large organic debris forms local base levels that trap over 26 cubic meters of sediment and cause over 14 percent of the vertical drop along a 412 meter study reach on tiger brook vermont the local base levels created by large organic debris accumulations are the most important control on sediment storage between large bedrock knickpoints along the study reach focusing fine grained sediment deposition in areas stable at low and moderate discharges the micro steps created by these lod local base levels dominate gradient and sediment storage at short time scales between the slowly evolving large bedrock macrosteps the relation that exists among the volumes of standing timber adjacent to the channel lod and sediment stored behind lod seems to indicate that large organic debris causes a negative feedback type mechanism where channel degradation leads to increased standing timber recruitment and large organic debris sediment storage sites

distribution of bedrock and alluvial channels in forested mountain drainage basins mountain river networks often consist of both bedrock and alluvial channels1 5 the spatial distribution of which controls several fundamental geomorphological and ecological processes6 7 the nature of river channels can influence the rates of river incision and landscape evolution1 2 as well as the stream habitat characteristics affecting species abundance and aquatic ecosystem structure8 11 studies of the factors controlling the distribution of bedrock and alluvial channels have hitherto been limited to anthropogenic badlands12 here we investigate the distribution of channel types in forested mountain drainage basins and show that the occurrence of bedrock and alluvial channels can be described by a threshold model relating local sediment transport capacity to sediment supply in addition we find that valley spanning log jams create alluvial channels hospitable to aquatic life in what would otherwise be bedrock reaches the formation of such jams depends critically on the stabilizing presence of logs derived from the largest trees in the riverside forests suggesting that management strategies that allow harvesting of such trees can have a devastating influence on alluvial habitats in mountain drainage basins

hydrologic and hydraulic effects of riparian root networks on streambank stability is mechanical root reinforcement the whole story abstract riparian vegetation has a number of effects on the mechanisms by which streambanks fail some positive and some negative previous research has shown that the effect of mechanical root reinforcement on soil stability can be considerable and can be successfully quantified and included in streambank stability models root networks contained within a soil matrix however also have effects on the hydrologic and hydraulic processes acting on a streambank and although these effects are often discussed they have generally been difficult to quantify this paper summarizes the results of field data collection laboratory testing and computer simulations carried out to better quantify the effects of riparian vegetation on hydrologic and hydraulic processes occurring along streambanks first the evapotranspiration potentials of different riparian species were isolated by setting up an experiment to grow young riparian trees and switch grass in separate soil columns each instrumented with tensiometers at 30 cm and 70 cm depths and compared against bare control columns the hydrological reinforcement provided to the soil from increased apparent cohesion as a result of enhanced matric suction was estimated to range from 1 0 to 3 1 kpa in spring when bank stability was most critical and up to a maximum of 5 0 kpa in the summer second a vertical jet test device was used to measure rates and volumes of scour in soils permeated by switch grass roots results showed that the volume of soil scoured during a test declined non linearly with increasing root volume per unit volume of soil and with increasing root length density rld and increasing root biomass calculation of relative soil detachment rates rsd showed that with the highest rooting densities measured in the field jet tests eroded soil volume was 10 of that in the tests with no roots third the effects of enhanced matric suction from evapotranspiration and decreased soil erodibility because of the presence of plant roots were modeled using bstem 5 1 to quantify the effects on streambank factor of safety fs and to compare with the effects of mechanical root reinforcement the sensitivity analysis showed that the change in soil matric suction from evapotranspiration provided the greatest potential benefit to fs but only during the summer months during the winter and spring months root reinforcement remained the most important contributor to fs the sensitivity analysis conducted here also showed that whilst roots are capable of reducing the volume of hydraulic scour the resulting effect on streambank geometry did not increase fs as much as changes in soil matric suction and or mechanical root reinforcement

wood recruitment and retention the fate of eroded trees on a braided river explored using a combination of field and remotely sensed data sources abstract this paper investigates wood recruitment and deposition dynamics in a large gravel bed braided river tagliamento river italy we used a combination of field measurements automatically repeated ground images and remotely sensed surveys to quantify wood input through bank erosion and associated downstream deposition two sites were investigated where floods caused the erosion of vegetated island edges a lidar survey preceding the erosion events provided data on the morphology and vegetation structure of the eroded areas allowing estimation of the number of trees that were uprooted sequences of ground based images acquired automatically and supported by field measurements showed the time number and location of deposited trees results show that the complex morphology of braided rivers induces specific deposition patterns we observed wide dispersal of wood on gravel bars with jams characterised by a small number of logs on average 2 3 and in many cases only a single log a large proportion of the eroded trees up to 40 were deposited on the nearest downstream bar this illustrates significant wood retention close to the recruitment site with the remaining wood dispersed widely downstream differences in the observed level of local wood retention were associated with the proximity of the erosion site to the main channel and differences were also observed in retention between the peak and the falling limb of flood events confirming that water depth and probably flow velocity are the crucial parameters controlling wood deposition

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

large wood sediment and flow regimes their interactions and temporal changes caused by human impacts in japan abstract water sediment and large wood lw are the three key components of dynamic river floodplain ecosystems we examined variations in sediment and lw discharge with respect to precipitation the presence of dams land and river use change and related channel incision and forest expansion on gravel bars and floodplains across japan the results indicated that unit sediment discharge and unit lw discharge were smaller in southern japan where precipitation intensity is generally much greater effective precipitation an index that takes current and antecedent precipitation into account was a strong predictor of discharge in small watersheds but not in larger watersheds however precipitation intensities related to unit sediment discharge in intermediate and large watersheds were smaller than those associated with unit lw discharge which we attribute to differences in particle shape and size and also transport mechanisms the relationship between river flow and discharge of sediment and lw lead us to posit that discharges of these components are supply limited in southern japan and transport limited in northern japan the cross sectional mean low flow bed elevation of gravel bed and sand bed rivers in japan decreased by 0 71 and 0 74 m on average respectively over the period 1960 2000 forest expansion on bars and floodplains has been prominent since the 1990s and trees apparently began to colonize gravel bars 10 to 20 years after riverbed degradation began forest recovery in headwater basins dam construction gravel mining and channelization over the past half century are likely the dominant factors that significantly reduced downstream sediment delivery thereby promoting channel incision and forest expansion changes in rivers and floodplains associated with channel incision and forest expansion alter the assemblages of aquatic and terrestrial organisms in riverine landscapes of japan and climate change may contribute to this change by intensified precipitation additionally regime shifts of water sediment and lw may continue or they may reach a dynamic state of quasi equilibrium in the future continued monitoring of these three components taking into account their geographic variation is critical for anticipating and managing future changes in river floodplain systems in japan and around the world

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

characteristics distribution and geomorphic role of large woody debris in a mountain stream of the chilean andes the paper presents an analysis of amounts characteristics and morphological impact of large woody debris lwd in the tres arroyos stream draining an old growth forested basin 9 1 km2 of the chilean southern andes large woody debris has been surveyed along a 1 5 km long channel section with an average slope of 0 07 and a general step pool cascade morphology specific wood storage is very high 656 710 m3 ha 1 comparable to that recorded in old growth forested basins in the pacific northwest half of the lwd elements were located on the active floodplain and around two thirds of lwd elements were found in accumulations different types of log jam were observed some heavily altering channel morphology log steps and valley jams while others just line the channel edges bankfull bench jams log steps represent approximately 22 of all steps whereas the elevation loss due to lwd log steps and valley jams results in 27 loss of the total stream potential energy about 1600 m3 of sediment is stored in the main channel behind lwd structures corresponding to approximately 150 of the annual sediment yield copyright 2007 john wiley sons ltd

changes in woody debris and bed material texture in a gravel bed channel abstract this study investigated the response of bed material texture under two distinct periods of log jam conditions in a 900 m study reach of carnation creek vancouver island bc a field program extending over seven flood seasons coupled with existing streamflow records channel maps and low altitude aerial photography provides observations of jam stability and permeability surface and subsurface grain size as well as bed material fluxes sediment supply calibre streambed stability and sediment exchange near jams all jams functioned as partial dams throughout the field program but the overall perturbation of sediment transfers decreased when two jams were breached bed material texture exhibited the largest differences over the study reach during a period when log jams exerted a stronger influence over the passage of water and sediment at individual gravel bars most adjustments in surface and subsurface grain size constituted less than a 20 change in percentile values larger changes occurred primarily in subsurface sediment temporal patterns in bed material texture exhibited variation between bars but downstream of breached jams surface sediment conformed to the expected fining trend while the subsurface sediment increased in size surface and subsurface sediments evolved in the same direction only 64 of the time and the different magnitudes of adjustment caused local armor ratios to vary over time results highlight that the temporal dynamism of large woody debris lwd should be coupled with spatial considerations for effective stream restoration and management of streambed sediment

decadal changes in distribution and frequency of wood in a free meandering river the ain river france this study examined the temporal dynamics and longitudinal distribution of wood over a multi decadal timescale at the river reach scale 36 km and a meander bend scale 300 600 m in the ain river a large gravel bed river flowing through a forested corridor and adjusting to regulation and floodplain land use change at the 36 km scale more wood was recruited by bank erosion in 1991 2000 than since the 1950s the longitudinal distribution of accumulations was similar between 1989 and 1999 but in both years individual pieces occurred homogeneously throughout the reach while jam distribution was localized associated with large concave banks a relationship between the mean number of pieces and the volume recruited by bank erosion r 2 0 97 indicated a spatial relationship between areas of wood production and storage wood mass stored and produced and channel sinuosity increased from 1993 to 2004 at three meander bends sinuosity was related to wood mass recruited by bank erosion during the previous decade r 2 0 73 and both of these parameters were correlated to the mean mass of wood plot r 2 0 98 and 0 69 respectively appearing to control wood storage and delivery at the bend scale this suggests a local origin of wood stored in channel not input from upstream trapped by preferential sites the increase in wood since 1950 is a response to floodplain afforestation to a change from braided to meandering channel pattern in response to regulation and to recent large floods we observed temporal stability of supply and depositional sectors over a decade on a reach scale meander bends were major storage sites trapping wood with concave banks also delivering wood these results and the link between sinuosity and wood frequency establish geomorphology as a dominant wood storage and recruitment control in large gravel bed rivers

large wood recruitment and transport during large floods a review large wood lw elements transported during large floods are long known to have the capacity to induce dangerous obstructions along the channel network mostly at bridges and at hydraulic structures such as weirs however our current knowledge of wood transport dynamics during high magnitude flood events is still very scarce mostly because these are locally rare and thus unlikely to be directly monitored therefore post event surveys are invaluable ways to get insights although indirectly on lw recruitment processes transport distance and factors inducing lw deposition all aspects that are crucial for the proper management of river basins related to flood hazard mitigation this paper presents a review of the quite limited literature available on lw transport during large floods drawing extensively on the authors own experience in mountain and piedmont rivers published and unpublished the overall picture emerging from these studies points to a high catchment specific variability in all the different processes affecting lw dynamics during floods specifically in the lw recruitment phase the relative floodplain bank erosion vs hillslope landslide and debris flows contribution in mountain rivers varies substantially as it relates to the extent of channel widening which depends on many variables itself but also to the hillslope channel connectivity of lw mobilized on the slopes as to the lw transport phase within the channel network it appears to be widely characterized by supply limited conditions whereby lw transport rates and thus volumes are ultimately constrained by the amount of lw that is made available to the flow indeed lw deposition during floods was mostly in terms of volume observed at artificial structures bridges in all the documented events this implies that the estimation of lw recruitment and the assessment of clogging probabilities for each structure for a flood event of given magnitude are the most important aspects for the prediction of lw transport magnitude at any cross section along the river network finally the review discusses the optimal strategies to manage lw related hazard which should consider riparian vegetation and in channel dead wood as key components of river ecosystems and thus should interfere with lw as well as with sediment transport dynamics only for limited spatial and temporal scales

a new methodology for monitoring wood fluxes in rivers using a ground camera potential and limits abstract ground imagery which produces large amounts of valuable data at high frequencies is increasingly used by fluvial geomorphologists to survey and understand processes while such technology provides immense quantities of information it can be challenging to analyze and requires automatization and associated development of new methodologies this paper presents a new approach to automate the processing of image analysis to monitor wood delivery from the upstream rhone river france the genissiat dam is used as an observation window all pieces of wood coming from the catchment are trapped here hence a wood raft accumulates over time in 2011 we installed an axis 211w camera to acquire oblique images of the reservoir every 10 min with the goal of automatically detecting a wood raft area in order to transform it to wood weight t and flux t d the methodology we developed is based on random forest classification to detect the wood raft surface over time which provided a good classification rate of 97 2 based on 14 mechanical wood extractions that included weight of wood removed each time conducted during the survey period we established a relationship between wood weight and wood raft surface area observed just before the extraction r2 0 93 we found that using such techniques to continuously monitor wood flux is difficult because the raft undergoes very significant changes through time in terms of density with a very high interday and intraday variability misclassifications caused by changes in weather conditions can be mitigated as well as errors from variation in pixel resolution owing to camera position or window size but a set of effects on raft density and mobility must still be explored e g dam operation effects wind on the reservoir surface at this stage only peak flow contribution to wood delivery can be well calculated but determining an accurate continuous series of wood flux is not possible several recommendations are made in terms of maximizing the potential benefit of such monitoring

transport and deposition of large woody debris in streams a flume experiment abstract large woody debris lwd is an integral component of forested streams of the pacific northwest and elsewhere yet little is known about how far wood is transported and where it is deposited in streams in this paper we report the results of flume experiments that examine interactions among hydraulics channel geometry transport distance and deposition of floating wood these experiments were carried out in a 1 22 m wide 9 14 m long gravel bed flume using wooden dowels of various sizes as surrogate logs channel planforms were either self formed or created by hand and ranged from meanders to alternate bars floating pieces tended to orient with long axes parallel to flow in the center of the channel pieces were deposited where channel depth was less than buoyant depth typically at the head of mid channel bars in shallow zones where flow expanded and on the outside of bends we hypothesize that the distance logs travel may be a function of the channel s debris roughness a dimensionless index incorporating ratios of piece length and diameter to channel width depth and sinuosity travel distance decreased as the ratio of piece length to both channel width and radius of curvature increased but the relative importance of these variables changed with channel planform large pieces can move further than our debris roughness models predict if greater than 50 of the active channel area is deeper than the buoyant depth of the piece or if momentum is high enough to carry pieces across shallows our debris roughness model allows first order prediction of the amount of wood transport under various channel geometries

modeling entrainment of waterlogged large wood in stream channels 1 research has led to an understanding of how floatable wood provides physical complexity and habitat in streams but little is known about large wood that does not float because it is waterlogged mineralized or naturally heavier than water to better understand the dynamics of this largely unrecognized component of streams i derived a theoretical model for predicting entrainment of waterlogged logs then constructed prototype logs to simulate waterlogged wood and used them to measure log friction and critical flow velocities at log entrainment in an alluvial creek i then modeled critical velocities under the same conditions entrainment was observed the model underpredicted critical velocities by an average of 24 with a range of error from 8 to 69 sensitivity analyses indicated that reducing lift and drag coefficients improved the average error but not the error range lack of unique drag coefficients for prototype logs winnowing of bed material from around prototype logs during entrainment tests error estimating friction for logs approaching neutral buoyancy and the variability of flow velocity common in streams were probable causes of error observed critical velocities that entrained prototype logs averaged 0 70 m s 1 critical velocities and log friction increased with branch length bed roughness and log density but only friction increased with log length friction coefficients averaged 0 62 and increased with branch length and bed roughness this model and existing equations for predicting movement of buoyant large wood can be used to compute budgets for logs with a range of attributes in streams

spatial density and characteristics of woody debris in five mountain rivers of the dolomites italian alps abstract this research quantifies amounts and characteristics of woody debris in mountain channels of the alps all pieces of woody debris greater than 5 cm diameter and 0 3 m length have been surveyed along five channels of the dolomites italian alps with channel slopes ranging from 0 04 to 0 26 basin area 2 2 51 km2 during the survey channels were divided into uniform reaches and the mean gradient bankfull width and depth of flow were measured overall 4900 woody debris pieces single and jam forming were measured and classified with respect to several qualitative attributes such as presence absence of rootwads orientation to flow and position in the channel results show that very large variations in the volume of woody debris per unit area of the streambed occur even within single streams and that inputs mainly result from slope instabilities adjacent to the channels amounts of woody debris are low compared to most previous data published from different world regions but match with other mountain rivers of the alps debris transport seems to be of minor importance compared to local inputs from the slopes because reach characteristics are poorly correlated with the volume of woody debris in a reach a strong negative correlation is however observed between basin area and average density of woody debris in the five channels but debris removal in the larger channels likely affects such a trend finally the frequency of log steps is inversely correlated to drainage area and positively related to the density of debris

effects on bedload transport of experimental removal of woody debris from a forest gravel bed stream experimental removal of woody debris from a small gravel bed stream in a forested area resulted in a four fold increase in bedload transport at bankfull discharge this was caused by increased transportability of sediment previously stored upslope of debris buttresses or in low energy hydraulic environments related to debris bank erosion delivered additional sediment to the channel and transport energy was increased by an inferred increase in the component of total boundary shear stress affecting grains on the bed increased transport following debris removal in may 1987 continued throughout the entire autumn storm season through late november 1987 indicating persistent adjustment of the stream bed and banks despite marked response to earlier flows as large as bankfull stream bed adjustments included development of a semi regular sequence of alternate bars and pools many of which were spaced independently of former pool locations

development of spatial pattern in large woody debris and debris dams in streams the spatial distribution of large woody debris lwd in streams was evaluated using neighbor k statistics following extensive wood deposition from an ice storm in the eastern adirondack mountains new york two years after wood deposition we surveyed individual pieces of lwd in one stream and surveyed debris dam locations in eight streams within the ice storm area to examine the linear pattern of debris dams within a stream we used a one dimensional version of ripley s k a second order statistic that evaluates the spatial pattern of points within a landscape both aggregated and segregated regularly spaced distributions of wood were identified individual pieces of lwd were aggregated at spatial extents ranging from 0 to 40 m and were segregated at spatial extents ranging from 80 to 100 m in two streams we found that debris dams were segregated at distances ranging from 100 to 300 m relative to randomly chosen locations but debris dams showed no significant spatial pattern in six other study streams previous studies of wood distribution in streams have not observed segregated distribution patterns spatial segregation of debris dams in the study area likely occurred in response to regularly spaced stream features or processes that allow movement of individual pieces of lwd toward more stable accumulation points neighbor k statistics can be used to identify and describe spatial pattern in large woody debris and such patterns can be used to help evaluate and identify processes responsible for their generation

wood storage within the active zone of a large european gravel bed river wood storage within the active zone of the dynamic gravel bed fiume tagliamento italy was investigated at eight sites along the river s main stem the quantity nature and mode of wood storage revealed a number of trends related to active zone morphology cover type and distance from the river s source relatively small quantities of wood were stored on open gravel surfaces estimates ranged from 1 to 21 t ha 1 intermediate quantities were associated with established islands 24 186 t ha 1 and large quantities were associated with pioneer islands 293 1664 t ha 1 thus variations in the geomorphological style of the river which are associated with changes in these three cover types are reflected in variations in the amount of wood that is stored in different reaches in addition although wood was found in many locations within the active zone it was preferentially stored in three specific locations i bar crests the main open gravel location for wood accumulations and pioneer islands ii the margins and iii surfaces of established islands the proportion of the stored wood that was living sprouting increased downstream and was higher on the open gravel than in association with established islands there was a downstream gradient in the dominant type of wood accumulation individual logs predominated at the most upstream site thereafter on the open gravel whole shrubs and trees dominated the more confined sites in the headwaters and middle reaches whereas jams were the most frequent form of accumulation in the downstream reaches jams were the most frequent type of accumulation associated with established islands throughout the river in contrast to small streams where debris dams constitute the major type of wood accumulation complex patterns and trends of wood storage were revealed along the tagliamento although further studies are needed it is clear that erosion of woody vegetation its subsequent transport and deposition play a major role in structuring the geomorphological and ecological character of this relatively natural large european river system insight into the mechanisms underlying the observed spatial patterns will contribute to a better understanding of the dynamic processes involved and is essential for more effective management of river ecosystems

leaky rivers implications of the loss of longitudinal fluvial disconnectivity in headwater streams article i nfo naturally induced longitudinal disconnectivity in the form of channel spanning logjams creates backwaters along headwater streams that reduce velocity and transport capacity create at least temporary storage sites for finer sediment and organic matter and enhance biological processing and uptake of nutrients land uses that reduce wood recruitment and instream storage result in reduced stream complexity and in creased longitudinal connectivity in headwater rivers we examine three scales of naturally occurring longi tudinal disconnectivity in headwater streams of the colorado front range and the implications for channel process and form of historical alterations in disconnectivity basin scale disconnectivity at channel lengths of 10 2 10 3 m results from downstream alternations between steep narrowly confined valley segments with single thread channels and lower gradient wider valley segments with multi thread channels this variation in valley geometry likely reflects differences in average spacing between joints in bedrock outcrops which influences bedrock weathering and erosion greater volumes of wood stored in the wide valley seg ments correlate with more closely spaced channel spanning logjams and greater storage of fine sediments and organic matter reach scale disconnectivity at channel lengths of 10 1 10 2 m results from the presence of numerous closely spaced channel spanning logjams which cumulatively store substantial amounts of fine sediment and organic matter the backwater effects associated with an individual jam can result in the accumulation of up to 11 m 3 of fine sediment upstream from the jam of which as much as 21 is organic

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

scour protection of partially embedded pipelines using sloping curtains abstracta geotextile mattress with sloping curtain gmsc was introduced to protect underwater pipelines from scour in steady currents gmsc is a newly developed countermeasure against river and es

the role of vegetation and large wood on the topographic characteristics of braided river systems riparian vegetation and large wood play a crucial role in shaping rivers on the one hand vegetation tends to increase bank stability reduce channel width and reduce the braiding index in gravel bed rivers conversely large wood tends to increase channel dynamics and promote avulsions the effects of vegetation and large wood have been rarely simulated together in flume experiments in this paper we present a series of experimental runs conducted in a large flume facility using cylindrical wooden dowels and alfalfa seedlings to represent logs and vegetation respectively in order to investigate their role on determining the topographical nature of braided river systems a terrestrial laser scanner was used to measure in detail the topography of the channels and bars and distribution of the elevations and second order structure functions were used to explore the topography that large wood and vegetation imposed on the braided pattern in the flumes results show that vegetation reduced the braiding index and produced wider and deeper channels the standard deviation of the bed elevations was higher than in flumes without vegetation large wood alone was not effective in changing the braiding index or the standard deviation of the elevations when vegetation and large wood acted together in the flume the braiding index reached a minimum value and the skewness of the distribution of elevation increased revealing shallower pools if compared with runs conducted with only vegetation

rules of the road a qualitative and quantitative synthesis of large wood transport through drainage networks abstract to effectively manage wood in rivers we need a better understanding of wood mobility within river networks here we review primarily field based and some numerical studies of wood transport we distinguish small medium large and great rivers based on wood piece dimensions relative to channel and flow dimensions and dominant controls on wood transport we suggest further identification and designation of wood transport regimes as a useful way to characterize spatial temporal network heterogeneity and to conceptualize the primary controls on wood mobility in diverse river segments we draw analogies between wood and bedload transport including distinguishing eulerian and lagrangian approaches exploring transport capacity and quantifying thresholds of wood mobility we identify mobility envelopes for remobilization of wood with relation to increasing peak discharges stream size and dimensionless log lengths wood transport in natural channels exhibits high spatial and temporal variability with discontinuities along the channel network at bankfull flow and when log lengths equal channel widths although median mobilization rates increase with increasing channel size maximum mobilization rates are greatest in medium sized channels most wood is transported during relatively infrequent high flows but flows under bankfull can transport up to 30 of stored wood we use conceptual models of dynamic equilibrium of wood in storage and of spiralling wood transport paths through drainage networks as well as a metaphor of traffic on a road to explore discontinuous wood movement through a river network the primary limitations to describing wood transport are inappropriate time scales of observation and lack of sufficient data on mobility from diverse rivers improving models of wood flux requires better characterization of average step lengths within the lifetime travel path of a piece of wood we suggest that future studies focus on i continuous or high frequency monitoring of wood mobility ii monitoring changes in wood storage iii using wood characteristics to fingerprint wood sources iv quantifying volumes of wood buried within river corridors v obtaining existing or new data from unconventional sources such as citizen science initiatives and vi creating online interactive data platforms to facilitate data synthesis

large wood recruitment processes and transported volumes in swiss mountain streams during the extreme flood of august 2005 abstract the extreme flood event that occurred in august 2005 was the most costly documented natural hazard event in the history of switzerland the flood was accompanied by the mobilization of 69 000 m3 of large wood lw throughout the affected area as recognized afterward wood played an important role in exacerbating the damages mainly because of log jams at bridges and weirs the present study aimed at assessing the risk posed by wood in various catchments by investigating the amount and spatial variability of recruited and transported lw data regarding lw quantities were obtained by field surveys remote sensing techniques lidar and gis analysis and was subsequently translated into a conceptual model of wood transport mass balance detailed wood budgets and transport diagrams were established for four study catchments of swiss mountain streams showing the spatial variability of lw recruitment and deposition despite some uncertainties with regard to parameter assumptions the sum of reconstructed wood input and observed deposition volumes agree reasonably well mass wasting such as landslides and debris flows were the dominant recruitment processes in headwater streams in contrast lw recruitment from lateral bank erosion became significant in the lower part of mountain streams where the catchment reached a size of about 100 km2 according to our analysis 88 of the reconstructed total wood input was fresh i e coming from living trees that were recruited from adjacent areas during the event this implies an average deadwood contribution of 12 most of which was estimated to have been in channel deadwood entrained during the flood event

analogies between mineral sediment and vegetative particle dynamics in fluvial systems abstract riparian vegetation fragments and propagules form part of the organic sediment load of rivers this review paper draws analogies between the transfer of these vegetative particles and that of mineral sediment within river systems whole plants vegetation fragments and propagules are delivered to rivers by physical processes but the timing of seed release and the morphological characteristics of the plants moderate delivery the transport and deposition of plant material is partly controlled by flow patterns but is also influenced by the buoyancy and morphology of the plant material once deposited the vegetative fragments propagules and the plants that develop from them can have significant local effects on flow hydraulics and sediment erodibility producing complex assemblages of physical features aggregate vegetative particles are identified as being particularly important in accelerating vegetation colonisation of exposed river sediments driving landform development and supporting the rapid development of a diverse cover of plants the geomorphological significance of interactions between vegetative particles and fluvial processes is illustrated at different spatial scales at the catchment scale ribbons of mineral and vegetative particles are transferred downstream with inputs continuously supplied throughout the river s course individual particles experience phases of mobilisation transport and deposition as a result along larger rivers down river changes are typically seen in the size and type of mineral sediment and vegetative particles and also the species composition of the vegetative particles coupled with downstream changes in hydroclimatological conditions within a river s active zone marked downstream changes in interactions between fluvial processes vegetation propagules and landforms can result at the patch scale individual vegetative particles particularly aggregate particles deposited on exposed riverine sediments create local hydraulic complexity that induces the scour and deposition of sediment and further plant propagules resulting in a suite of distinctive landforms which may support many plant species within individual reaches patch scale interactions between mineral sediment and vegetative particles are moderated or sieved by the form of the reach and its flow patterns so that the integration of patch scale effects can support the development of different landforms in different locations

spatial distribution of coarse woody debris dams in the lymington basin hampshire uk abstract debris dams of coarse woody debris have a significant influence on channel processes in forested areas but few detailed studies have been made of variations within a single basin results from previous research are standardised and show that average variations throughout basins include densities of debris dams up to 40 per 100 metres of channel and can involve a loading value of up to 225 kg per m2 of channel variations have been ascribed to distance downstream to channel width to land use effects to felling and to the management of coarse woody debris in streams this study of the lymington basin 110 4 km2 in drainage area shows that the input of storm debris resulting from blowdown accounts for 45 of the gross load the remaining 55 net load varies to distance downstream to land use with the greatest loads in deciduous woodland areas and according to management removal of debris from streams and multiple regression equations are provided it is deduced that as a consequence of long term management the present channel debris may be as little as 7 of the total net load that could have been present if no management had occurred

hierarchical patterns of physical biological associations in river ecosystems abstract the interplay of biological and physical patterns and processes within river ecosystems generates a complex matrix of interactions a challenge in interdisciplinary river science is to dissect patterns and processes in multi causal river ecosystems into hierarchical levels of organization hierarchy theory and the associated concept of scale provides a sound framework for achieving this we present two interdisciplinary case studies that demonstrate how a multi scale approach can dissect hierarchies of organization in river ecosystems the first case study examined patterns of large wood character and distribution at three scales of a hierarchy of morphological river system organization in the large lowland river murray the character and distribution of large wood was uniform at the largest reach scale 95 km length of river because stream energy conditions are relatively uniform within the reach however there was an association between lower level functional sets straight or bend sections of river and functional units 12 quadrats within each functional set and the character and distribution of large wood because stream energy differs between straight and bend morphologies and the inner and outer channel functional units thus functional sets and functional units are important levels of organization for large wood in the river murray the second case study examined the associations between macroinvertebrate assemblage distribution and environmental influences across a hierarchy of river system organization in the upland murrumbidgee river catchment we previously demonstrated that macroinvertebrate assemblages were arranged hierarchically at the region cluster within region reach within cluster and riffle within reach scales with region and reach being the strongest signatures in this study we related different scaled environmental factors collected across a hierarchy of catchment zone valley confinement reach similar stream orders and riffle scales to the region and cluster levels of macroinvertebrate distribution the hierarchical pattern of large region level and local reach level macroinvertebrate distribution was matched by a large catchment scale and local reach scale of environmental influence intermediate zone scale environmental factors and smaller riffle scale factors were not important influences thus large regions and catchments and local reaches are important levels of organization for macroinvertebrate environment associations in rivers of the upper murrumbidgee catchment both case studies support the applicability of hierarchy theory to describe the organization of physical biological associations in river ecosystems the multi scaled approach allowed the detection of levels of hierarchical organization and showed other hierarchical characteristics such as emergent properties and top down constraint bottom up influence hierarchical understanding of river ecosystem organization will enhance river conservation and management because it facilitates a holistic ecosystem perspective rather than a partial single scale single component or single discipline perspective

understanding processes of island development on an island braided river over timescales from days to decades this is the peer reviewed version of the following article gurnell a m bertoldi w francis r a gurnell j and mardhiah u 2019 understanding processes of island development on an island braided river over timescales from days to decades earth surf process landforms 44 624 640 https doi org 10 1002 esp 4494 which has been published in final form at https doi org 10 1002 esp 4494 this article may be used for non commercial purposes in accordance with wiley terms and conditions for use of self archived versions

modern changes of the high mountain landscapes and glaciation in southern siberia russia by the example of the eastern sayan mountains the period of observations of glaciation of the munku sardyk mountain massif in siberia is one of the longest i e 155 years however the data obtained are scattered and not systematic the paper presents an integrated analysis of the materials collected since the first description by the explorer of siberian mountains g i radde istoriy 1896 and extended by peretolchin 1908 and komarov 1953 as well as by glaciologists maksimov 1965 arefiev and mukhametov 1996 the authors considered the current state of the glaciers and interaction of natural geosystems of the massif taking into account the nival glacial processes since the beginning of the current millennium regular observations have been conducted on the munku sardyk massif by the v b sochava institute of geography sb ras limnological institute sb ras and east siberian state academy of education the studies revealed the leading landscape forming factors and examined the landscape structure of the surroundings of the contemporary nival glacial geosystems with due regard for the manifestations of altitudinal zonation a medium scale landscape typological mapping was carried out presented are the quantitative parameters of the dynamics of the nival glacial geosystems obtained on the basis of modern remote sensing instruments gps measurements and surface laser scanning using gis analysis the stump and stem of larch detected in the valley of the bugovek river 300 m above the contemporary upper forest limit and 1330 m up the valley show that most likely there was no glaciation during the atlantic period 7000 7300 years ago the modern glacier complex has formed only during the last 4000 5000 years the trend of shrinkage of glaciers since the end of the little ice age can be traced especially in recent years the length and area of the open part of the glaciers have decreased by half from 0 68 to 0 34 km2 the presence of small forms of glaciation on the southernmost limit of the siberian glaciation 1500 m below the theoretical climate boundary suggests that this area can be considered a unique key site to identify trends in development of the mountain and nival glacial geosystems and provides an opportunity to built reconstructive and predictive models of development of mountain landscapes under the conditions of ever increasing anthropogenic influence

mountain glaciers of southeast siberia current state and changes since the little ice age contemporary glaciers of southeast siberia are located on three high mountain ridges east sayan baikalsky and kodar in this study we present an updated glacier inventory based on high to middle resolution satellite imagery and field investigations the inventory includes 51 glaciers with a total area of 15 km2 areas of individual glaciers vary from 0 06 to 1 33 km2 lengths from 130 to 2010 m and elevations from 1796 to 3490 m the recent ice maximum extents little ice age have been delineated from terminal moraines on average debris free surface area shrunk by 59 between 1850 and 2006 11 0 37 a 1 by 44 between 1850 and 2001 02 0 29 a 1 and by 27 between 2001 02 and 2006 11 3 39 a 1 the kodar glaciers have experienced the largest area shrinkage while the area loss on baikalsky ridge was more moderate glacier changes are mainly related to regional summer temperature increase by 1 7 2 6c from 1970 to 2010 there are some differences in glacier response due to different spatial patterns of snow accumulation local topography e g glacier elevation slope and geological activity the studied glaciers especially of kodar ridge are the most sensitive in siberia to climate change since the late 20th century

nival glacial dynamics of geosystems in eastern siberia russia for the last 50 years it is presented the results of studying of small glaciers located in the eastern siberia along transect the kodar mountains baikalskiy and barguzinskiy ridges the eastern sayan mountains some glaciers from this transect have not been described before the inventorying of these glaciers is based on high resolution satellite images and fieldworks the most numbers of glaciers are located in the kodar mountains and few are in the baikalskiy and the barguzinskiy ridges most likely these glaciers remained mainly due to coldest winters and geomorphologic features the main parameters of a glacier s data the dynamics the current state cartographic representation remote sensing data and others are selected by analogy of the international glaciological database

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

temporal variations of large wood abundance and mobility in the blanco river affected by the chaiten volcanic eruption southern chile abstract the aim of this study is to analyze the temporal variation in abundance and transport of in channel wood along a river affected by a volcanic eruption considering the mobility and retention rates in detail the 2008 eruption of chaiten volcano southern chile severely affected the blanco river basin causing changes in channel morphology and large wood lw dynamics along the fluvial corridor of the river a fourth order stream on the southern slope of the volcano temporal dynamics of lw were investigated from january 2015 until march 2016 in three 80 m long study reaches of the active channel in the lower course of the river every wood element 1 m in length and 0 1 m in diameter within the active channel of each reach was georeferenced measured tagged and characterized wood mobility rate defined as the number of tagged wood pieces repositioned or not found within each study reach to total tagged lw in the same reach and retention rate defined as the number of tagged lw pieces found within each study reach to total tagged wood pieces in the same reach were calculated considering two periods one in summer and one in autumn winter a regional flood frequency analysis estimated flood magnitude defining a recurrence interval of 1 year for summer floods and 10 25 years for autumn winter floods results highlighted how eight years after the eruption the types of lw are still influenced by the impacts of pyroclastic density currents on riparian vegetation the characteristics and abundance of monitored lw are typical of a river system with frequent wood transport the mobility rate ranges between 42 and 94 during the summer and autumn winter period respectively while the wood volume decreases during the summer and increases in autumn winter large wood mobility was also found to vary according to the predominant morphological settings with lower values in narrower channels compared to wider wetted areas in this context the greatest abundance of lw was detected after the higher floods corresponding to an input of lw up to 285 35 m3 ha 1 along the blanco river ordinary floods deliver lw mainly through fluvial transport and bank erosion during higher floods appears as an additional and important wood recruitment process the bank erosion processes with up to 5200 m2 of eroded area confirmed the widening tendency occurring in river systems following volcanic disturbances as there are dead riparian trees along the easily erodible banks it is reasonable to suppose that the blanco river will continue to widen for a long period recruiting and transporting downstream huge volumes of lw in this context these analyses appear of fundamental importance to better manage the river system also for decreasing hazards to the downstream village of chaiten

the distribution of large woody debris accumulations and pools in relation to woodland stream management in a small low gradient stream this paper focuses upon the natural dynamics of large woody debris lwd the impact of management on lwd dynamics and the impact of lwd removal and channelization on the distribution and size of pools in a british second to third order headwater catchment the study stream is rather different from those subject to lwd accumulations which have been studied in north america the most important contrast is that it is surrounded by predominantly deciduous rather than coniferous woodland in terms of its width 1 8 4 5 m and gradient 0 013 m m 1 it falls within the lower range of channels studied in north america nevertheless there are similarities in lwd dam and pool spacing with some north american studies the information on lwd dynamics during a period without management and on recovery of lwd dams after clearance covers a 16 year period 1982 1997 the paper illustrates that seven to eight years after clearance the total number of lwd dams has recovered but the most hydraulically active dam type has not recovered to pre clearance levels an analysis of geomorphological maps of the channel surveyed in 1982 and 1996 97 shows an overall decrease in the number and size of pools along the section that was cleared of lwd dams the magnitude of the decrease and the associated adjustments in pools through changes in their size and location differ according to location with respect to a section of the study stream which was channelized in c 1966 and which has subsequently incised its bed copyright 1998 john wiley sons ltd

late holocene development of a floodplain along a small meandering stream northern quebec canada this paper describes the activity of a small meandering stream and the development of its floodplain during the last 4600 years calendar years bp in the northern boreal zone of quebec three trenches were excavated across the floodplain s full width and permitted the interpretation of morphosedimentary units in relation to modern analogs chronological controls within trenches was provided by the dendrochronological and radiocarbon dating of buried tree trunks from 4600 to 2900 cal bp and from 1000 to 120 cal bp the channel migrated and constructed its floodplain at very slow rates mostly because of low flow velocities vegetated streambanks and the cohesive texture of marine sediments reworked by the channel vertical accretion rates were extremely variable on the floodplain with high rates proximal to the modern channel and low rates over distal also older portions of the floodplain following a major channel shift meander cut off or avulsion around 2900 cal bp channel migration appears to have been constrained to a narrow zone adjacent to the modern channel within this constrained zone the migrating channel has reworked its own sediments leading to a marked unconformity between 2900 1000 cal bp it is thought that underlying marine sediments protrusions and perhaps the forested banks protected older alluvial sediments from being eroded during the last three millenniums our study shows that small boreal floodplains may contain in a very small area abundant and diversified archives of their evolution

contrasting patterns of wood storage in mountain watercourses narrower and wider than the height of riparian trees abstract large wood exerts a beneficial influence on the functioning of riverine and riparian ecosystems but can be also the source of flood risk several studies have recognised a trend of decreasing amounts of large wood on unit channel area with increasing width of mountain streams this study verifies whether this trend can also be generalised for wide mountain rivers longitudinal wood distribution was compared for two watercourses in the polish carpathians second to fourth order kamienica stream 14 m wide on average and the fifth order czarny dunajec river with a mean width of 52 m in the stream both the number and the mean mass of wood deposits were unrelated to channel width and this was reflected in a lack of the relationship between total wood storage the amount of stored wood per channel length and channel width in turn specific wood storage the amount of stored wood per channel area decreased nonlinearly with increasing channel width in the wide czarny dunajec the number and the mean mass of wood deposits increased as the river widened and this was reflected in a marked trend of increasing total wood storage with increasing river width here the width related variation in total wood storage was so high that it overcame the influence of increasing channel area on calculated values of specific wood storage which also increased with increasing river width this study shows that different mechanisms known to govern large wood retention in the channels narrower and wider than the height of riparian trees are reflected in the contrasting patterns of wood storage in mountain watercourses of different relative width different relations between the tendencies of total and specific wood storage in the two types of channels emphasise the need of identifying the spatial density and the total amount of large wood

log transport and deposition in incised channelized and multithread reaches of a wide mountain river tracking experiment during a 20 year flood abstract distance of large wood transport during floods and conditions for wood deposition in wide mountain rivers are still insufficiently understood tracking of logs tagged with radio transmitters was used to investigate differences in depositional conditions and the length of log displacement during a 20 year flood between channel reaches of different morphology in the czarny dunajec river polish carpathians during the rising limb of the flood logs were placed into the river at three locations at the beginning of an incised reach close to the beginning of a channelized reach and 1 km upstream from the beginning of a wide multithread reach the incised channelized and multithread reaches retained 12 5 33 and 94 of tagged logs introduced to these reaches respectively and of the logs retained in the multithread reach all were deposited in its upstream half significant differences in the length of displacement existed between the logs delivered to the river at the three locations with logs placed into the river at the beginning of the incised reach moving the longest distance and those delivered just upstream from the multithread reach moving the shortest distance before deposition one fourth of the logs were deposited in a low flow channel or on a channel margin one fifth on the floodplain and more than half on gravel bars after the flood river cross sections with deposited logs and a set of cross sections without any wood deposits were surveyed to collect data for one dimensional modelling of hydraulic conditions at the flood peak the cross sections with deposited logs were typified by significantly greater flow width and flow area and by significantly smaller mean flow depth mean velocity froude number mean bed shear stress and unit stream power principal component analysis of the hydraulic parameters in the analysed cross sections grouped the two types of cross sections in distinct clusters indicating that multithread cross sections differed in hydraulic parameters from all the other cross sections the experiment confirmed findings from the previous wood inventory and numerical modelling of wood transport and deposition in the river indicating that in a wide mountain river wood can be transported long distances in a narrow single thread channel it is however preferentially deposited in a wide multithread channel that functions as a natural wood trap preventing or considerably limiting further transfer of large wood to vulnerable sites therefore it is crucial to avoid channelization of multithread reaches that would eliminate their functioning as natural wood traps the hydraulic modelling provided a physical justification for the observed differences in wood behaviour between the distinct channel morphologies

the geomorphic function and characteristics of large woody debris in low gradient rivers coastal maine usa abstract the role function and importance of large woody debris lwd in rivers depend strongly on environmental context and land use history the coastal watersheds of central and northern maine northeastern u s are characterized by low gradients moderate topography and minimal influence of mass wasting processes along with a history of intensive commercial timber harvest in spite of the ecological importance of these rivers which contain the last wild populations of atlantic salmon salmo salar in the u s we know little about lwd distribution dynamics and function in these systems we conducted a cross basin analysis in seven coastal maine watersheds documenting the size frequency volume position and orientation of lwd as well as the association between lwd pool formation and sediment storage in conjunction with these lwd surveys we conducted extensive riparian vegetation surveys we observed very low lwd frequencies and volumes across the 60 km of rivers surveyed frequency of lwd 20 cm diameter ranged from 15 50 pieces km 1 and wood volumes were commonly 3 km 1 moreover most of this wood was located in the immediate low flow channel zone was oriented parallel to flow and failed to span the stream channel as a result pool formation associated with lwd is generally lacking and

large woody debris physical process and riparian forest development in montane river networks of the pacific northwest abstract we present a conceptual biogeomorphic model of riparian forest development in montane river networks the role of physical process in driving the structure composition and spatial distribution of riparian forests is examined we classify the drainage network into disturbance process based segments including 1 debris flow and avalanche channels 2 fluvial and debris flow channels and 3 fluvial channels riparian forests are shown to be significant in the development of channel morphology through the stabilization of active floodplains and as sources of large woody debris olwd lwd is operationally defined as wood 0 1 m diameter and 1 m length lwd plays a key role in the development of montane riparian forests lwd deposited in the active channel and floodplain provides sites for vegetation colonization forest island growth and coalescence and forest floodplain development riparian forest patterns parallel the distribution of hillslope and fluvial processes through the network riparian forest structure composition and spatial distribution through the network are driven by the major disturbance processes including 1 avalanches 2 debris flows and 3 flooding riparian forest patterns also reflect the action of lwd in the organization and development of forested floodplains in gravel bedded montane river networks the focus of our examples are montane river networks of the pacific northwest usa

channel adjustments and vegetation cover dynamics in a large gravel bed river over the last 200 years article i nfo the timing and extent of the morphological changes that occurred in the last 200 years in a large gravel bed river the piave river eastern italian alps that was heavily impacted by human activities training structures hydropower schemes and gravel mining have been analyzed by historical maps aerial photos repeated topographic measurements and geomorphological surveys results show that the channel underwent a strong narrowing during the twentieth century but with a faster pace during the 1970s 1990s and with an associated shift from a dominant braided pattern to a wandering morphology bed incision up to 2 m mostly from gravel mining has been documented for this period large areas of the former active channel were colonized by riparian forests both as islands and as marginal woodlands the ceasing of gravel extraction in the late 1990s seems to have determined a reversal in the evolutionary trend with evidence of vegetation erosion channel widening even though a significant aggradation phase is not present we conclude that alteration of sediment regime has played a major role on the long term channel evolution however only relevant flood events rin10 15 years appear to determine substantial island erosion and therefore the proportion of island vs channel area fluctuates depending on flood history

physical modelling of the combined effect of vegetation and wood on river morphology abstract the research reported in this paper employs flume experiments to investigate the potential effects of living vegetation and large wood on river morphology specifically aiming to explore how different wood input and vegetation scenarios impact channel patterns and dynamics we used a mobile bed laboratory flume divided into three parallel channels 1 7 m wide 10 m long and filled with uniform sand to reproduce braided networks subject to a series of cycles of flooding wood input and vegetation growth temporal evolution of river configuration in terms of the braiding index vegetation establishment and erosion and wood deposition amount and pattern was recorded in a series of vertical images the experiments reproduced many forms and processes that have been observed in the field from scattered logs in unvegetated dynamic braided channels to large wood jams associated with river bars and bends in vegetated stable single thread rivers results showed that the inclusion of vegetation in the experiments changes wood dynamics in terms of the quantity that is stored and the depositional patterns that develop vegetated banks increased channel stability reducing lateral erosion and the number of active channels this promoted the formation of stable wood jams where logs accumulated continuously at the same locations during subsequent floods reinforcing their effect on river morphology the feasibility of studying these processes in a controlled environment opens new possibilities for disentangling the complex linkages in the biogeomorphological evolution of the fluvial system and thus for promoting improved scientific understanding

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

mobility of large woody debris lwd jams in a low gradient channel abstract mobility of large woody debris lwd in low gradient channels is an important but often overlooked transport process the majority of studies on lwd have focused on its role in geomorphic and ecologic river processes when jams extend across the width of the channel they have the potential to retain sediment and alter the channel profile when jams obstruct only a portion of the channel they can re direct flow altering patterns of scour and deposition the boundary complexity created by lwd has a recognized role in riverine ecosystems which has led to programs of replacing lwd in channel corridors where it was previously removed although lwd jams are common in rivers around the world they have been studied most intensely in steep forested channel reaches where they are often found to be stable channel features it is not fully known how much of the information on lwd from steep forested channels will transfer to other channel types whereas it may be reasonable to assume that the ecological benefits of lwd are similar in low gradient channels research has shown that a much higher rate of lwd transport occurs in low gradient channels with jams mobilized on timescales of 10 0 10 2 years this study evaluates the distribution and mobility of lwd over 72 km of the san antonio river a low gradient channel in southeast texas lwd jam locations were identified for 2003 and 2007 using a combination of aerial photography and field mapping each jam was cataloged according to its location in the channel cross section and the amount of channel area blocked during the four year period all the lwd jams were mobilized including those jams extending across the channel width although easily mobilized 34 jams re form in the same locations creating 34 channel locations with persistent lwd jams data from the san antonio river are applied to two models developed to predict lwd mobility and transport distances to assess the applicability of each model to a low gradient channel the locations of stable or recurring lwd jams were matched to model results where predicted lwd transport distances were equal to measured lwd jam spacing model results showed good agreement with the mean and median spacing of lwd jams when given input parameters specific to the channel and wood species the ability to predict where lwd jams will persist over time in a low gradient channel has application in watershed management persistent lwd jams can exert a greater influence on channel morphology and may require active management

the floodplain large wood cycle hypothesis a mechanism for the physical and biotic structuring of temperate forested alluvial valleys in the north pacific coastal ecoregion abstract a floodplain large wood cycle is hypothesized as a mechanism for generating landforms and influencing river dynamics in ways that structure and maintain riparian and aquatic ecosystems of forested alluvial river valleys of the pacific coastal temperate rainforest of north america in the cycle pieces of wood large enough to resist fluvial transport and remain in river channels initiate and stabilize wood jams which in turn create alluvial patches and protect them from erosion these stable patches provide sites for trees to mature over hundreds of years in river valleys where the average cycle of floodplain turnover is much briefer thus providing a future source of large wood and reinforcing the cycle different tree species can function in the floodplain large wood cycle in different ecological regions in different river valleys within regions and within individual river valleys in which forest composition changes through time the cycle promotes a physically complex biodiverse and self reinforcing state conversely loss of large trees from the system drives landforms and ecosystems toward an alternate stable state of diminished biogeomorphic complexity reestablishing large trees is thus necessary to restore such rivers although interactions and mechanisms may differ between biomes and in larger or smaller rivers available evidence suggests that large riparian trees may have similarly fundamental roles in the physical and biotic structuring of river valleys elsewhere in the temperate zone

stabilization of a gravel channel by large streamside obstructions and bedrock bends jacoby creek northwestern california jacoby creek bed width 12 m bankfull discharge 32 6 m 3 s contains stationary gravel bars that have forms and positions controlled by numerous large streamside obstructions bedrock outcrops large woody debris and rooted bank projections and bedrock bends bank projection width and bar volume measured in 104 channel segments 1 bed width long are significantly cross correlated at lags of 1 3 and 4 indicating the tendency for large obstructions and bends to form bars 3 to 4 bed widths downstream and 1 bed width upstream all of the 18 bars downstream of large obstructions or bends in the study reach were along the obstruction side of the channel or outside bank of the bend most of the pools 85 were next to large obstructions or in bends conversely 92 of large obstructions or bends had pools comparison of the volume of four bars with volumetric bar changes and volume of bedload transported during four high flow events suggests that rates of sediment transport were sufficient to cause major changes in bars during bankfull events the only important channel changes observed in 4 yr however have been associated with the movement of large woody debris and with changes in the angle at which the flow approaches an obstruction a general model is proposed that large obstructions and nonalluvial bends stabilize the form and location of gravel bars bars are stabilized by two related mechanisms 1 large obstructions and bends cause intense quasi steady secondary circulation in scour holes that terminate upstream bars at fixed locations obstruction width channel deflection scour hole width and bed width were measured at 26 obstructions these data show that obstructions wider than approximately one third of the bed form pools spanning the entire channel and thus terminating bars smaller obstructions form scour holes contained within a single bar 2 bars are deposited upstream of large obstructions and sharp bends because of backwater reductions in stream power bars are deposited downstream because flow energy is expended around obstructions and bends and because the flow expands downstream of constrictions that result from large obstructions the formation of bars and pools inherent in many gravel channels can thus be enhanced and fixed in position by flow structures set up around large obstructions and bends formed of resistant materials

dynamics of natural conditions around modern glaciation location at the eastern sayan mountain massif munku sardyk presents the highest mountain range and adjacent stanovoy ridge highlands of the eastern sayan there is situated modern glaciation site which was the most studied in the course of last 160 years this periglacial area experienced different periods of cooling and warming in the holocene and retained traces of the sartan glaciation of subboreal 3000 5000 years ago the little ice age the evidences of holocene optimum and general warming last time the authors examined the variability of activity of modern glaciation and variation of natural conditions of the periglacial zone on climate and on dendrochronological data results of larch and siberian stone pine growth data were revealed at the higher border of forest communities analysis of the growth of the fossil tree in the holocene optimum showed that the absolute magnitude of its increment was two times higher than for up to date long lived trees identified periods of the peretolchin glacier retreat in 1900 1965 and 1983 2000 years took place with increased growth of trees and the rate of sedimentation in proglacial lake and vice versa glacier advance on in 1965 1980 years was accompanied by slowing of tree increments and reduction in sedimentation rate since 2000 there has been growth of trees instability associated with a decrease in average monthly summer temperatures

assessment of flow forces on large wood in rivers 1 large wood lw exerts an important influence on the geomorphology and ecology of streams and rivers the magnitudes of flow forces on lw are needed to support stream management activities and are typically computed using time mean lift and drag coefficients determined in laboratory flumes using small smooth cylinders herein we report measurements of forces on lw of varying complexity simple cylinder branching and complex root wad and surface bark roughness made in an outdoor grassed channel under steady and unsteady flows lw orientation relative to the primary flow direction and lw relative submergence were varied drag and lift coefficients for cylindrical unbranched lw followed patterns reported by others for metal cylinders in wind tunnels drag coefficients for cylindrical unbranched lw corrected for blockage effects ranged from 0 05 to 1 29 and lift coefficients ranged from 0 88 to 0 52 varying systematically with lw position relative to the channel bed and incident flow direction measured drag coefficients for the noncylindrical lw corrected for blockage effects ranged from 0 22 to 6 27 while lift coefficients varied from 3 65 to 30 84 systematic relationships between the relative submergence and orientation of branching lw and the drag and lift coefficients were not observed but coefficients were greatest for lw with few branches and converged on smaller values typical of blunt bodies as lw complexity increased for both simple and complex lw maximum lift and drag forces during the rising limb of unsteady flows were about 2 3 times greater than steady flow temporal mean values

distribution recruitment and geomorphic significance of large woody debris in an alluvial forest stream tonghi creek southeastern australia the complex yet poorly understood interactions between riparian vegetation large woody debris and fluvial geomorphology in an anthropogenically undisturbed reach of an alluvial sand bed forest stream in se australia have been determined riparian vegetation exhibits lateral and vertical zonation of understorey and overstorey species the dominant riparian tree species tristaniopsis laurina water gum grows within the channel and on the floodplain within one channel width of the stream larger eucalyptus species only grow on the highest parts of the floodplain and on a low pleistocene river terrace a complete large woody debris lwd census conducted in the 715 m long study reach revealed that water gum comprises 17 6 of the total lwd loading which at 576 m 3 ha 1 is high for a stream with a catchment area of 187 km 2 although most lwd has a small diameter 0 1 0 3 m the greatest contribution to the total volume of lwd is by pieces with a diameter between 0 3 and 0 7 m a high proportion of lwd 10 4 has a blockage ratio greater than 10 the spatial distribution of lwd is random both longitudinally and within individual meander bends dominant recruitment processes of lwd vary by species t laurina trees are recruited to the channel by minor bank erosion and senescence while the eucalyptus species are predominantly recruited from the highest parts of the floodplain low river terrace by episodic windthrow during large storms multiple radiocarbon dates of outer wood of immobile lwd indicate a maximum residence time of 240f40 years bp for t laurina timber the high loading of lwd combined with the extensive root systems of riparian vegetation stabilize tonghi creek log steps form natural wooden drop structures with a mean height of 29 mm that were responsible for 20 5 of the total head loss under base flow conditions q 0 08 m 3 s 1 large woody debris is buried in the bed at depths of up to 2 3 m and is responsible for an estimated 49 of the 11 600 m 3 of sand stored in the study reach pools are spaced at 0 8 channel widths and 82 of pools are formed by scour over under around or beside lwd or by the impoundment of water upstream of debris dams due to the high density of hardwood timber species debris dams however do not readily form in tonghi creek as the timber is difficult to transport and lwd usually sinks to the bed of the stream despite the high degree of

transport of large woody debris in the presence of obstacles flume experiments were carried out to investigate the motion of large woody debris lwd in rivers as influenced by the presence of obstacles non rooted defoliated lwd was modelled by placing properly scaled wooden dowels placed into controlled water flow obstacles were represented by wooden rods randomly placed into the flume with a specified probability distribution the results provide the probability of lodging of the dowels and statistics of the distance travelled their relationships with flow rate and depth dowel length and spatial density of the obstacles is explored this yields a general theoretical framework to approach lwd transport in rivers by combining random factors with deterministic dimensionless variables

neighborhood matters patterns and controls on wood distribution in old growth forest streams of the colorado front range usa abstract we surveyed wood characteristics along four headwater channel segments of the colorado front range with drainage areas of 8 82 km2 stream lengths surveyed range from 3025 to 8980 m and together include a total of 15 706 pieces of wood time since last disturbance in the form of a stand killing fire varied from 31 to 500 years individual pieces of wood were highly aggregated at length scales of 1 to 150 m trends among jams were more weakly developed but jams tended to be more segregated at lengths 300 m with jams along individual channels being aggregated segregated or random multiple linear regressions failed to produce highly predictive models to explain the response variables of wood load piece dimensions or characteristics of jams other than jam volume which correlated with drainage area and wood load but examination of downstream patterns suggests that local valley and channel geometry valley bottom width gradient and sequence of longitudinal channel changes exert a stronger influence on patterns of wood distribution than either time since last forest disturbance or progressive downstream trends associated with increasing drainage area the longitudinal sequences of wood recruitment sources forest stand age and channel geometry together exert an important control on reach scale wood load and aggregation wood loads in streams draining old growth 250 years forests of the colorado front range are low compared to old growth sites in other regions of the world which we interpret to reflect decreased retention of wood recruited to the streams

3d scour below pipelines under waves and combined waves and currents this paper presents the results of an experimental investigation on three dimensional local scour below a rigid pipeline subjected to wave only and combined wave and current conditions the tests were conducted in a conventional wave flume the major emphasis of the investigation was on the scour propagation speed free span expansion rate along the pipeline after local scour was initiated at a controlled location the effects of flow ratio steady current velocity vs combined waves current velocity flow incidence angle and pipeline initial embedment depth on free span expansion rate were investigated it was observed that the scour along the pipeline propagated at a constant rate under wave only conditions the scour propagation rate decreased with increasing embedment depth however increased with the increasing keuglegan carpenter kc number under combined wave and current conditions the effect of velocity ratio on scour propagation velocity along the pipeline was quantified empirical relationships between the scour propagation rate vh and key parameters such as the kc number and embedment depth e d were established based on the testing results

the complexity of the real world in the context of the field tradition in geomorphology abstract among the dominant twentieth century conceptual models of geomorphology that rely on insights resulting from field based research are stanley a schumm s formulations of complex response intrinsic thresholds river metamorphosis and spatial zonation of drainage basins schumm s research focused primarily on finer grained alluvial channels in lower relief environments as a result of his work most investigators now approach river process and form within a framework based on three fundamental assumptions first channel changes are abrupt and driven by crossing external and internal thresholds second channel change is likely to be asynchronous resulting in different portions of a river or a river network behaving in very different manners at a given point in time third different portions of a river network are dominated by distinct disturbance regimes and resulting suites of geomorphic processes and forms more recent research on resistant boundary mountain channels illustrates how field evidence demonstrates that river process and form are inherently nonlinear with spatial and temporal thresholds multithread channels can form within unconfined valley segments in mountainous river networks of the colorado front range but only in the presence of biotic drivers in the form of i old growth forest that facilitates the formation of closely spaced channel spanning logjams or ii beavers that build dams thresholds of channel and valley geometry govern the occurrence and persistence of jams and dams and these channel obstructions initiate specific nonlinear responses in valley and channel form when the biotic drivers are removed river metamorphosis occurs alluvial channels which are typically regarded as being relatively responsive to changes in water and sediment yield and substrate composition and channels with more resistant boundaries that typically respond to external changes over longer timespans exhibit nonlinear complex behavior in both cases the nonlinear behavior of rivers with numerous interdependent variables multiple internal and external thresholds and complex responses would be difficult to conceptualize and quantify in the absence of extensive field data one of the management implications of complex nonlinear behavior is that a one size fits all approach to managing rivers is inadequate field research initially focused on understanding specific examples of river process and form revealed underlying patterns that give rise to conceptual models broadly applicable within fluvial geomorphology

modeling channel morphodynamic response to variations in large wood implications for stream rehabilitation in degraded watersheds abstract anthropogenic modification of forests has often decoupled streams from riparian ecosystems and altered natural wood recruitment processes extensive research has shown that large wood significantly impacts channel dynamics especially in small and intermediate sized forested streams where wood pieces are similar in length to channel width and many stream rehabilitation efforts now involve the addition of large wood to streams the primary objective of this research is to investigate the relation between large wood and reach scale channel morphology and hydraulics using a physical model in order to better inform stream rehabilitation programs and future modeling efforts four experiments each comprising numerous five hour runs were conducted using a froude scaled stream table with wood loads scaled to 0 m3 m2 0 011 m3 m2 0 016 m3 m2 and 0 022 m3 m2 the addition of large wood significantly decreased the reach averaged velocity in all experiments and was associated with decreased sediment transport and increased sediment storage in the reach increases in bed and water surface slope compensated for the loss of energy available to transport sediment and enabled the system to reach a new steady state within the equivalent of 6 to 9 years adding wood increased pool frequency as well as the variability in cross sectional depth while causing the reach to undergo a transition from a plane bed to a riffle pool morphology retention of fine sediment increased the availability of fish spawning substrate while increased water stage improved connectivity between the channel and the floodplain the changes in habitat complexity were generally related to the wood load added to the reach but were also dependent on the orientation and arrangement of the pieces these results demonstrate that wood may exert a primary control on channel morphodynamics and the availability of aquatic habitat in intermediate sized streams and suggest that the benefits from stream rehabilitation efforts are highly dependent on project scale the relatively long time needed to realize habitat benefits demonstrates that long term monitoring of rehabilitation projects is necessary

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

flood plain and channel dynamics of the quinault and queets rivers washington usa abstract comparison of historic channel migration rates modern planform conditions and overall sediment wood and flow conditions and interactions for the quinault river and queets river in the western olympic peninsula washington reveals decadal to century scale interactions between gravel bed channels and forested flood plains in temperate maritime environments the downstream alluvial portions of these two rivers can be divided into three reaches of different slope flow sediment and wood regimes i the upper quinault river is aggrading behind lake quinault a natural lake that traps most sediment and wood transported from the olympic mountain headwaters ii the lower quinault river downstream of lake quinault transports only sediment and wood derived from reworking of flood plain deposits and contributed from valley margins iii the queets river has unimpeded movement of sediment and water from the mountainous headwaters to the pacific ocean measurements of channel planform characteristics and historic migration rates and patterns show that these three reaches have correspondingly distinct channel and flood plain morphologies and dynamics the aggrading and sediment rich upper quinault river has the widest flood plain widest active channel greatest number of low flow channels and flanking gravel bars and an average channel migration rate of 12 7 3 3 m year between 1900 and 1994 the comparatively sediment poor lower quinault river has the narrowest flood plain narrowest active channel and lowest channel migration rate 4 0 1 2 m year and most flow is through a single channel with few adjacent gravel bars the queets river has attributes intermediate between the lower and upper quinault rivers including an average channel migration rate of 7 5 2 9 m year flood plain turnover rates are similar for all three reaches with channels eroding the flood plain at the rate of about 0 2 of the flood plain area per year and with corresponding flood plain half lives of 300 to 500 years observations from this study and previous studies on the queets river show that channel and flood plain dynamics and morphology are affected by interactions between flow sediment and standing and entrained wood some of which likely involve time frames similar to 200 500 year flood plain half lives on the upper quinault river and queets river log jams promote bar growth and consequent channel shifting short distance avulsions and meander cutoffs resulting in mobile and wide active channels on the lower quinault river large portions of the channel are stable and flow within vegetated flood plains however locally channel spanning log jams have caused channel avulsions within reaches that have been subsequently mobile for several decades in all three reaches log jams appear to be areas of conifer germination and growth that may later further influence channel and flood plain conditions on long time scales by forming flood plain areas resistant to channel migration and by providing key members of future log jams appreciation of these processes and dynamics and associated temporal and spatial scales is necessary to formulate effective long term approaches to managing fluvial ecosystems in forested environments

groundwater controls on biogeomorphic succession and river channel morphodynamics biogeomorphic succession describes feedbacks between vegetation succession and fluvial processes that at the decadal timescale lead to a transition from bare river deposited sediment to fully developed riparian forest where the rate of stabilization by biogeomorphic succession is greater than the rate of ecological disturbance by fluvial processes a river is likely to evolve into less dynamic states while river research has frequently considered the physical dimensions of morphodynamics less is known about physical controls on succession rates and how these impact stream morphodynamics here we test the hypothesis that groundwater dynamics influence morphodynamics via the rate of biogeomorphic succession we applied historic imagery analysis in combination with dendroecological methods for willows growing on young gravelly fluvial landforms along a steep groundwater depth gradient we determined the following floodplain morphodynamics and plant encroachment at the decadal scale pioneer willow growth rates and their relationships to hydrological variables willow growth rates were correlated with moisture availability groundwater discharge and precipitation variability in the downwelling reach while little correlation was found in the upwelling reach after a reduction in ecological disturbance frequency data suggest that where groundwater is upwelling biogeomorphic succession is fast the engineering effect of vegetation is quickly established and hence channel stability increased and active channel width reduces where groundwater is downwelling deeper and more variable biogeomorphic succession is slower the engineering effect is reduced and a wider active width is maintained thus groundwater is an important control on biogeomorphic feedbacks intensity and through the stabilizing effect of vegetation may drive long term river channel morphodynamics

morphological adaptation of river channels to vegetation establishment a laboratory study while the scientific community has long recognized that alluvial rivers are the product of interactions between flowing water and bed material transport it is increasingly evident that vegetation mediates these interactions and influences the stream channel characteristics in a novel set of mobile bed laboratory experiments with variable discharge we demonstrate that vegetation colonization affects bank erosion rates channel shape channel sinuosity and bar pattern our analyses compared the morphological evolution of channels with initially steady bars considering the following three scenarios 1 channel without vegetation 2 channel with vegetation added to the floodplains and 3 channel with vegetation added to both the floodplains and the bar surfaces that emerge at low flows absence of vegetation produced the widest and shallowest channel with the lowest sinuosity floodplain vegetation in the second scenario reduced bank erosion and resulted in a deeper and more sinuous channel with shorter bars in the third scenario vegetation establishment on emerging bar surfaces intensified erosion on the opposing bank enlarging the amplitude of bends enhanced sedimentation on vegetated bar areas increased both bar elevation and bar length compared to the second scenario the results show that the colonization of bar surfaces by plants creates the conditions for new floodplain and island formation fostering channel meandering and anabranching finally our experiments emphasize the role of alternating high and low flows on the morphological development of streams mediated by vegetation

geomorphic effects of wood quantity and characteristics in three italian gravel bed rivers abstract in channel wood is a fundamental component of the riverine system its nature abundance and distribution as well as the role of wood in trapping sediment have been reported by many authors however a lack of knowledge still exists on how the geomorphic effects quantity and characteristics of in channel wood may be altered by different human pressures for this reason in channel wood was surveyed in the brenta piave and tagliamento gravel bed rivers northeastern italy which are altered by different degrees of human pressures both single pieces of wood 0 1 m diameter and or 1 m long and accumulations of large wood were measured on cross sectional transects within the active channels overall 3430 8 4 13 9 and 10 7 elements ha in the brenta piave and tagliamento rivers respectively of isolated pieces and 591 9 8 15 0 and 11 0 wood accumulations ha in the brenta piave and tagliamento rivers respectively accumulations were surveyed in the study sites in the brenta and piave rivers which feature the greater human pressures logs appear in a worse state of conservation in the less disturbed tagliamento river the logs appear to be smaller and in a better state of conservation with higher capacity for resprouting in addition higher geomorphic interactions were found between wood and sediments in the tagliamento river because of its ability to create geomorphic effects in channel wood represents an important source of complexity that can increase habitat diversity in river systems a better knowledge of the role of human disturbances on the characteristics and abundance of large wood in river systems could help in developing better river management and the practical application of river ecology

wood storage in a wide mountain river case study of the czarny dunajec polish carpathians storage of large woody debris in the wide mountain czarny dunajec river southern poland was investigated following two floods of june and july 2001 with a seven year frequency within a reach to which wood was delivered only by bank erosion and transport from upstream wood quantities were estimated for eighty nine 100 m long channel segments grouped into nine sections of similar morphology results from regression analysis indicated the quantity of stored wood to be directly related to the length of eroded wooded banks and river width and inversely related to unit stream power at the flood peak the largest quantities of wood up to 33 t ha 1 were stored in wide multi thread river sections here the relatively low transporting ability of the river facilitated deposition of transported wood while a considerable length of eroded channel and island banks resulted in a large number of trees delivered from the local riparian forest in these sections a few morphological and ecological situations led to the accumulation of especially large quantities of wood within a small river area very low amounts of wood were stored in narrow single thread sections of regulated or bedrock channel high stream power facilitated transport of wood through these sections while the high strength of the banks and low channel sinuosity prevented bank retreat and delivery of trees to the channel considerable differences in the character of deposited wood existed between wide multi thread channel sections located at different distances below a narrow 7 km long channellized reach of the river wood deposited close to the downstream end of the channellized reach was highly disintegrated and structured into jams whereas further downstream well preserved shrubs and trees prevailed this apparently reflects differences in the distance of wood transport and shows that in a mountain river wider than the height of trees growing on its banks wood can be transported long distances along relatively narrow single thread reaches but is preferentially deposited in wide multi thread reaches copyright 2005 john wiley sons ltd

coarse sediment movement in the vicinity of a logjam in a neotropical gravel bed stream wood influences channel morphology by increasing channel roughness altering flow hydraulics and decreasing sediment transport in most fluvial systems where it is present in many locations the collection of wood into jams leads to even greater interruption of sediment transport by means of sediment impoundment and the creation of low velocity backwater flow zones we examined tracer clast movement near a wood jam in a neotropical gravel bed stream in order to evaluate the effect of wood mobility and piece transience on the ability of the jam to impede sediment transport we found that the jam had minimal influence on the passage of any individual clast with tracer clast mobilization and travel distance being best predicted by flow magnitude and grain size rather than location relative to the jam the rate of clast passage through the jam did not correlate with either the piece retention rate of the jam or with the density of the jam the jam did however temporarily trap a sediment wedge during a period when fluvially imported wood pieces blocked flow under a key wood piece diverting flow to a secondary flow path these results suggest that there is an upper bound on the flows in which wood is able to disrupt sediment transport and unlike for bedrock roughness elements this bound is frequently crossed at our study site

input storage and distribution of large woody debris along a mountain river continuum the drome river france abstract large woody debris lwd input storage and distribution were studied along the drome river a french alpine river with an active shifting channel and a well developed riparian forest lwd input from the floodplain is low 669 6 mg year 1 between 1948 and 1971 and 569 3 mg year 1 between 1971 and 1991 based on estimates of average lwd mass per study plot a range of 766 2122 mg year 1 of lwd were stored within the active channel e g unvegetated bars and low flow channel 60 km course covering 492 ha lwd accumulations are mainly observed on gravel bars at a limited number of preferential sites they are relatively rare and are randomly distributed in the low flow channel consequently lwd location is mainly associated with the decrease of flow level in shallow sectors in the low flow channel lwd stop en route is primarily caused by in channel structures such as boulders or vegetated islets general geomorphological factors e g pattern slope etc provide less explanation of lwd distribution moreover the residence time of lwd accumulations on the drome river is short lwd storage 1 3 3 7 times the annual lwd input from the floodplain and their morphogenic role is negligible few of the accumulations are buried or characterized by vegetation shoots and associated pools

laboratory modeling of the mechanisms of piping erosion initiation a laboratory modeling program has been conducted to assess the mechanics of initiating the piping erosion process in sandy soils the models were performed on several soils differing in gradation grain size grain shape and specific gravity observations and monitoring of pore pressures within the samples during the modeling identified four stages in the development of piping initiation initial movement progressive heave boil formation and total heave by linking the observed behavior with the measured pore pressure regime in the sample a model for the mechanics of piping development has been developed finite element seepage analyses were performed to model the progression of piping development in the laboratory models and corroborate the developed model of mechanics the findings of the study identified a new model for the initiation of piping development that can be applied to the assessment of piping in the field

morphological perspective on the sedimentary characteristics of a coarse braided reach tagliamento river ne italy abstract in order to understand heterogeneity distribution of hydraulic properties many studies have proposed models of coarse braided river deposits however they often focus either on the surface near surface or on ancient deposit analysis furthermore the link between morphological surface and sedimentological outcrops information has not been fully explored yet this publication aims to characterize the morphodynamics of a braided gravel bed reach of the tagliamento river ne italy and to assess its relationship with the subsurface heterogeneity the morphological analysis is based on a lidar derived dem aerial and satellite photographs from 1998 to 2011 as well as field observations a water stage time series allows the morphological changes to be related to the discharge dynamics the sedimentological knowledge on coarse braided deposits was mainly gained from the observation of analog pleistocene coarse deposits in switzerland the main geomorphological elements are identified in terms of their topographic signature and genesis setting apart the trichotomy water vegetation bar the braidplain is characterized by higher lying zones with dentritic gully drainage networks and active zones where most of the morphology reworking occurs furthermore two morphologies mark the active zones a low discharge morphology low discharge incisions and channels slip face lobes etc superimposed on a high discharge morphology gravel sheets scours etc each morphological element is related to a depositional i e sedimentological element whose preservation potential in the subsurface is assessed as a function of the river bed aggradation dynamic the settings that impact the subsurface flow in terms of fast pathway and connectivity are addressed

log jam effects on bed load mobility from experiments conducted in a small gravel bed forest ditch abstract bed load transport experiments have been conducted in a steep gravel bed open ditch this initially straight ditch has been neglected for many years and looks at present like a second order natural stream channel the channel flows through a spruce forest and several log jams have produced chutes and pools creating supplementary roughness the total shear stress has been evaluated using the slope hydraulic radius product and the ratio between grain and bed form shear stresses has been calculated using different methods the shear stress has also been evaluated from the shear velocities and this gives a good evaluation of the grain shear stress additional experiments have been conducted with marked pebbles to estimate particle mobility and to improve the motion equations equations such as c a di d50 b b defined by andrews apply in these cases but the values of a and b are lower than those produced by this author in a second stage of experimentation we have destroyed the log jams resulting in a diminution of the roughness and critical shear stress when the total shear stress is used an increase of the grain shear stress and thus greater bed particle mobility for the same discharge it emerges from these experiments that the log jams contribute to the reduction of bed load evacuation and explain the very weak bed load discharge measured by a bed load trap 0 3 t km 2 yr 1

impact of glacier changes on ecosystem of proglacial lakes in high mountain regions of east siberia russia mountain lakes in east siberia have been studied for recent changes in water chemistry turbidity and diatom assemblages preserved in bottom sediments we performed a regional analysis of the relative effect of climate and glacier changes on change in diatom diversity and supply of meltware in proglacial lakes we analysed sediment records from east siberian glacier lakes using geochemical and diatoms proxies we found that dramatic changes in communities and abundance of diatoms and biogenic proxy could be induced by low nutrient concentrations in glacial lakes and high turbidity due to active degradation of glaciers and snow patches as a result of the global increase in temperature in the northern hemisphere our evidences show that diatoms have been gradually decreased since ca the 1880s a significant tendency towards diatom reducing occurred at high summer regional temperatures this tendency may be attributed to the fact that glaciers and snow patches thawed actively in east siberia during ca 1880 1958 which was induced by the beginning of the recent warming ca 1850 1860 and a long period of relatively warm regional climate from ca 1900 to 1960

effect of sampling time in the laboratory investigation of braided rivers we focus on the measurement of the bed elevation of braided networks in flume experiments in particular the effect of the survey frequency on the measurement accuracy is studied to this aim an innovative measurement system is adopted it consists of a laser ultrasonic sensor and can survey the bed elevation under owing water this measurement system was used to profile a flume transect with a frequency of 4 minutes without stopping the water discharge by this technique the topography of a single transect was continuously acquired during the evolution of a braided river model twelve braided rivers generated with different experimental conditions were studied the main results are i there exists a threshold survey frequency 4 8 minutes in our analysis which guarantees that the morphological evolution of the braiding channels is fully measured ii if this threshold frequency of survey is exceeded significant errors occur in the balance of the eroded deposited sediments and in the evaluation of the bed elevation dynamics and iii these errors depend on the river stream power

bridging the gaps an overview of wood across time and space in diverse rivers abstract nearly 50 years of research focused on large wood lw in rivers provide a basis for understanding how wood enters rivers how wood decays breaks and is transported downstream and how at least temporarily stable wood influences channel geometry fluxes of water sediment and organic matter and the abundance and diversity of aquatic and riparian organisms field based studies have led to qualitative conceptual models and to numerical stimulations of river processes involving wood numerous important gaps remain however in our understanding of wood dynamics the majority of research on wood in rivers focuses on small to medium sized rivers defined using the ratio of wood piece size to channel width as channels narrower than the locally typical wood piece length small and slightly narrower than the longer wood pieces present medium although diverse geographic regions and biomes are represented by one or a few studies in each region the majority of research comes from perennial rivers draining temperate conifer forests regional syntheses most commonly focus on the pacific northwest region of north america where most of these studies originate consequently significant gaps in our understanding include lack of knowledge of wood related processes in large rivers dryland rivers and rivers of the high and low latitudes using a wood budget as an organizing framework this paper identifies other gaps related to wood recruitment transport storage and how beavers influence lw dynamics with respect to wood recruitment we lack information on the relative importance of mass tree mortality and transport of buried or surficial downed wood from the floodplain into the channel in diverse settings knowledge gaps related to wood transport include transport distances of lw and thresholds for lw mobility in small to medium rivers with respect to wood storage we have limited data on longitudinal trends in lw loads within unaltered large and great rivers and on fluctuations in lw load over time intervals greater than a few years other knowledge gaps relate to physical and ecological effects of wood including the magnitude of flow resistance caused by lw patterns of wood related sediment storage for diverse river sizes and channel geometry quantification of channel floodplain lw interactions and potential threshold effects of lw in relation to physical processes and biotic communities finally knowledge gaps are related to management of large wood and river corridors including understanding the consequences of enormous historical reductions in lw load in rivers through the forested portions of the temperate zone and how to effectively reintroduce and manage existing lw in river corridors which includes enhancing public understanding of the importance of lw addressing these knowledge gaps requires more case studies from diverse rivers as well as more syntheses and metadata analyses

a flume experiment on the formation of wood jams in rivers 1 a flume experiment is carried out to explore jamming of large woody debris lwd in streams with complex morphology occurring in mountain streams with in channel boulders or vegetation in braided rivers or in floodplains during flood events non rooted defoliated lwd is modeled using wood dowels and obstacles to motion are represented by vertical wood rods congested transport of lwd is simulated by insertion of a number 100 of dowels the final position of the dowels is mapped and the observed jams are classified according to their size and position the key member of each jam is identified and its trapping mechanism evaluated either by leaning against a single obstacle or by bridging two obstacles to mimic uncongested transport the experiment is repeated for single pieces of wood with subsequent removal longer dowels and shallower water result in shorter traveled distance wood pieces travel farther when congested transport is observed the traveled distance of the wood pieces can be modeled using a gamma distribution for both congested and uncongested transport jams instead display uniform traveled distance the number of pieces displays an exponential distribution the degree of uniformity in space of jams and wood pieces is evaluated using a neighbor k statistic wood pieces show considerable clustering while jams show sparse distribution eventually the relationship between jams magnitude and position is explored showing negative correlation model application is then discussed and some conclusions and future developments are outlined

palaeozoic landscapes shaped by plant evolution fluvial landscapes diversified markedly over the 250 million years between the cambrian and pennsylvanian periods the diversification occurred in tandem with the evolution of vascular plants and expanding vegetation cover in the absence of widespread vegetation landscapes during the cambrian and ordovican periods were dominated by rivers with wide sand beds and aeolian tracts during the late silurian and devonian periods the appearance of vascular plants with root systems was associated with the development of channelled sand bed rivers meandering rivers and muddy floodplains the widespread expansion of trees by the early pennsylvanian marks the appearance of narrow fixed channels some representing anabranching systems and braided rivers with vegetated islands we conclude that the development of roots stabilized the banks of rivers and streams the subsequent appearance of woody debris led to log jams that promoted the rapid formation of new river channels our contention is supported by studies of modern fluvial systems and laboratory experiments in turn fluvial styles influenced plant evolution as new ecological settings developed along the fluvial systems we suggest that terrestrial plant and landscape evolution allowed colonization by an increasingly diverse array of organisms

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

assessment of transfer patterns and origins of in channel wood in large rivers using repeated field surveys and wood characterisation the isere river upstream of pontcharra france abstract when and whence does wood enter large mountain alluvial rivers how stable through time are characteristics and quantities of wood deposited in a reach these simple questions related to the complex practice of wood budgeting are explored on the isere river in france we hypothesise that i the wood originates from the riparian zone all along the alluvial reach and that ii the characters and quantity of wood in the reach can vary through time according to flood occurrence and provenance in order to validate these hypotheses two complementary approaches were performed i wood pieces were surveyed along 190 km river length and taxonomy in channel wood macromorphology and dendrochemistry were used to infer wood origin local vs upstream respective subbasin contributions and transport conditions ii wood movement was monitored using both tracking techniques in specific sampling plots and with an experiment orchestrated using wood placement coupled with a significant artificial flood surveys were done over a period of 3 years so as to include two distinct sampling events to explore wood deposition and mobilisation within a channel network under different flood conditions one of the subbasins the arly river underwent a 1 in 30 year flood in 2004 allowing us to assess its effect on in channel wood quantity and characteristics results confirm that wood is primarily introduced by erosion from river banks but they are not always as close as expected from the sites of deposition temporal variability of wood introduced deposited and transferred downstream is also significant in terms of abundance and origin as shown by dendrochemical and macromorphological signatures the types of wood observed along the channel length changes through time large flood signature can be detected from wood characteristics and uplands make a slight contribution but in average wood characteristics do not change much no significant difference between years and tributaries in wood characteristics based on discriminant analysis data suggest that the interannual variability is fairly low so that the diversity of wood characteristics is maintained by the complex and multiple sources of wood in the network further research is needed to better understand such patterns and to study physical breakage in space and time to better infer distance between sources and depositional zones

the role of large wood in retaining fine sediment organic matter and plant propagules in a small single thread forest river abstract this paper investigates associations among large wood accumulations retained sediment and organic matter and the establishment of a viable propagule bank within a forested reach of a lowland river the highland water uk a wood survey within the 2 km study reach illustrates that the quantity of wood retained within the channel is typical of relatively unmanaged river channels bordered by deciduous woodland and that the wood accumulations jams that are present are well developed typically spanning the river channel and comprised of wood that is well decayed sediment samples were obtained in a stratified random design focusing on nine subreaches within which samples were aggregated from five different types of sampling location two of these locations were wood associated within and on bank faces immediately adjacent to wood jams and the other three locations represented the broader river environment gravel bars bank faces floodplain the samples were analysed to establish their calibre organic and viable plant propagule content the gravel bar sampling locations retained significantly coarser sediment containing a lower proportion of organic matter and viable propagules than the other four sampling locations the two wood related sampling locations retained sediment of intermediate calibre between the gravel bar and the bank floodplain samples but they retained significantly more organic matter and viable propagules than were found in the other three sampling locations in particular the jam bank samples areas of sediment accumulation against bank faces adjacent to wood jams contained the highest number of propagules and the largest number of propagule species these results suggest that retention of propagules organic matter and relatively fine sediment in and around wood jams has the potential to support vegetation regeneration further sediment retention and as a consequence landform development within woodland streams although this process is arrested by grazing at the study site these results also suggest that self restoration using wood is a potentially cost effective and far reaching river restoration strategy but that its full effects develop gradually and require the establishment of a functioning wood budget coupled with grazing levels that are in balance with vegetation growth

porosity and volume assessments of large wood lw accumulations abstract the formation of large wood lw accumulations during floods represents a major hazard for constricted river cross sections e g bridges and weirs as it affects flow hydraulics and sediment transport to better assess lw accumulations reliable strategies and techniques are required there are currently practical limits on monitoring accumulation configurations both laser scans and photogrammetric techniques can be used to scan the outer contours of lw accumulations but cannot practically assess the wood content and porosity details of the outer deposit are captured in high resolution but the core of the deposit remains occluded and estimation is necessary this becomes more challenging for deposits of increasing size relative to wood elements to develop a more efficient workflow for lw accumulation assessment in the field we performed a laboratory study to develop a relationship between the envelope volume of water worked lw jams during a single flood hydrograph and the volume of woody elements within explicitly accounting for porosity we used photogrammetric techniques now in common use for reconnaissance surveys of debris accumulations on wood accumulations scaled for the laboratory the study s aim is to develop a semi automated assessment method enabling efficient image acquisition processing and computation of lw accumulation volume using a multi camera array above the laboratory channel and applying structure from motion photogrammetry we developed 3d models for 16 experimental flow formed wood accumulations each with 50 individual wooden dowels no correlations were found between porosity and flow magnitude porosity was found to be similar for most deposits 66 as a result of this accumulation structure the envelope volume used in 3d and 2 5d photogrammetric methods tended to overestimate wood content by 3 and 2 6 respectively the results obtained here will contribute to a more reliable volumetric assessment for inventories of wood mass in river systems

wood distribution along streams draining old growth floodplain forests in congaree national park south carolina usa abstract we measured wood volume and other characteristics along a series of instream and floodplain transects in and around congaree national park south carolina seven transects were surveyed at most sites one within the bankfull channel and three on each bank at 10 50 and 100 m lateral distances respectively from the channel along each transect we measured piece dimensions location along transect orientation and decay category we also characterized channel width drainage area vegetation type average forest basal area and inundation category for each transect forest transects 100 m from a channel were also surveyed instream wood loads for unmanaged channels draining old growth forests were 102 178 m 3 ha which is lower than most instream wood loads documented for old growth temperate forests we attribute the lower wood loads to the combined effects of high transport capacity and rapid decay floodplain wood loads are lowest close to the channel but increase with distance reaching comparable values up to 172 m 3 ha at distances 100 m from a channel channel geometry does not appear to exert the significant influence on instream wood loads that has been documented for more laterally constrained channels channel spanning jams are uncommon and appear to be transient features

bank erosion history of a mountain stream determined by means of anatomical changes in exposed tree roots over the last 100 years bila opava river czech republic abstract the date of exposure of spruce roots as a result of bank erosion was investigated on the bila opava river in the northeastern czech republic following the exposure of roots wood cells in the tree rings divide into early wood and late wood root cells within the tree rings also become smaller and more numerous these processes permit dating of the erosion episodes in which roots were exposed sixty root samples were taken from seven sampling sites selected on two riverbed reaches the results of root exposure dating were compared to historical data on hydrological flooding using the root exposure dating method several erosion episodes were recorded for the last 100 years the greatest bank erosion was recorded as consequence of an extraordinary flood in july 1997 in the upper rocky part of the valley studied bank erosion often took place during large floods that occurred in the early 20th century in the lower alluvial part of the valley erosion in the exposed roots was recorded only in 1973 and has been intensive ever since it is suggested that banks in the lower part are more frequently undercut which leads to the falling of trees within whose roots older erosion episodes were recorded locally bank erosion is often intensified by the position of 1 to 2 m boulders in the riverbed which direct water into the parts of the banks where erosion occurs selective bank erosion could be intensified by debris dams and hillslope material supply to the riverbed

influence of large woody debris on morphological evolution of incised sand bed channels this paper documents the influence of large woody debris lwd on the morphological evolution of unstable degrading sand bed rivers in the yazoo basin north mississippi usa the study was performed as part of the demonstration erosion control dec project twenty three river reaches were studied with the aim of determining whether the presence of lwd was beneficial or detrimental to the recovery of stability in degrading sand bed river systems and to provide the geomorphic understanding necessary to underpin enhanced lwd management strategies the results demonstrate that locations of lwd inputs volumes of lwd stored in different reaches and number of jams per unit channel length are causally related to the morphological processes occurring during different stages of adjustment in these unstable incised fluvial systems and may be explained using a channel evolution model cem the net impact of lwd jams on reach scale sediment budgets was found in general to be positive that is jams trap more sediment than they mobilise this suggests that lwd probably accelerates rather than retards recovery of a stable longitudinal profile and channel configuration following incision field typing of lwd jams based on their impacts on the flow pattern reveals that jam type is a function of the size of large key elements in the jam in relation to the channel width a debris jam classification scheme is proposed on this basis with the spatial relationship between jam type and drainage basin area expressed using a dimensionless function of the ratio between channel width and average riparian tree height the scheme features four jam types underflow dam deflector and flow parallel bar head each of which has a different morphological impact on local channel geometry these jam types may be used to classify lwd jams as an aid in determining appropriate management strategies according to their location within the drainage basin

tracking log displacement during floods in the tagliamento river using rfid and gps tracker devices large pieces of in channel wood can exert an important role on the ecological and morphological properties of gravel bed rivers on the other side when transported during flood events large wood can become a source of risk for sensitive structures such as bridges however wood displacement and velocity in river systems are still poorly understood especially in large gravel bed rivers this study focuses on log transport in a valley reach of tagliamento river italy log displacement during flood events of different magnitudes recorded from june 2010 to october 2011 has been analysed thanks to the installation of 113 radio frequency identification rfid tags and 42 gps tracker devices in logs of different dimensions recovery rates of logs equipped with rfid and gps trackers were about 43 and 42 respectively the gps devices allowed us to analyse in details the log displacement and transport overtime indicating a higher log entrainment during rising limb of hydrographs the threshold for the entrainment of logs from low bars is around 40 of bankfull water stage no clear relationship was found between the peak of flood and log displacement length and velocity however log displacement length and velocity appear significantly correlated to the ratio between the peak of flow and the water stage exceeding the flow duration curve for 25 of time i e the ratio hmax h25 ratio log deposition was observed to occur at the peak flow and logs transported during ordinary events are preferably deposited on low bars this study reveals the potentials of gps tracker devices to monitor the entrainment and movements of logs in large gravel bed rivers during floods these observations could be useful for better planning of river management practices and strategies involving the use of large wood pieces and could help for calibrating wood budgets at the reach scale

three dimensional mapping of geomorphic controls on flood plain hydrology and connectivity from aerial photos abstract the nyack flood plain of the middle fork flathead river mt usa is a 9 km anastomosed alluvial montane flood plain upstream from the flood plain the river is unregulated and the catchment virtually pristine a patchy mosaic of vegetation and channels exists on the flood plain surface the surface and subsurface geomorphic structures of the flood plain facilitate high hydrologic connectivity water flux between the channel and flood plain marked by complex seasonal patterns of flood plain inundation extensive penetration of channel water laterally into the alluvial aquifer and springbrooks formed by ground water erupting onto the flood plain surface after delineating and classifying flood plain elements vegetation patches and channel reaches on the flood plain we analyzed field based elevation survey data to identify expected relationships among flood plain element type surface scour frequency and flood plain elevation data analyses show that scour frequency was inversely proportional to the elevation of the flood plain above river stage except when localized geomorphic controls such as natural levees prevent normal high flows from inundating and scouring relatively low flood plain elements further while different flood plain element types occupy distinct elevation zones on the flood plain the elevation of each zone above the river channel varies with localized channel entrenchment we found that topographic variation among flood plain elements is greater than the variation within elements suggesting that coarse scale flood plain topography can be characterized by delineating flood plain elements field data document strong associations between specific classes of flood plain elements and preferential ground water flow paths in the upper alluvial aquifer combined with preexisting ground penetrating radar gpr surveys these data intimate a sinuous lattice of preferential ground water flow paths buried abandoned streambeds in the upper alluvial aquifer at approximately the same elevation as the main channel s streambed using aerial photo interpretation and the identified relationships among element types elevation and preferential ground water flow paths we developed a quantitative three dimensional characterization of surface and subsurface geomorphology across the entire flood plain to support a heuristic modeling effort investigating the influence of flood plain geomorphology on spatio temporal patterns of surface and ground water flow and exchange under dynamic hydrologic regimes

using structure from motion photogrammetry to assess large wood lw accumulations in the field abstract river systems in forested catchments are strongly influenced by wood and sediment loading from both natural e g mass wasting and anthropogenic forestry sources in order to effectively manage impacts on property infrastructure and the broader ecosystem as well as to better assess the interactions between large wood lw channel morphology and flow hydraulics more efficient and accurate surveying techniques are required we present an evaluation of structure from motion sfm photogrammetry and point cloud based techniques for capturing the geometry and volume of lw in the field wood accumulations can be notoriously complex 3d objects with multi scalar features and thus difficult to quantify with photogrammetric methods we introduce a novel workflow to generate volumetric information of organic material accumulations using sfm and a suite of meshing algorithms the volumes of two accumulations are assessed individually using several meshing techniques and are compared with more conventional volume estimates results show volumetric variations of

dynamic single thread channels maintained by the interaction of flow and vegetation most rivers on earth today flow as a single channel in some cases with occasional islands and follow a more or less sinuous course however single thread channels have proven difficult to reproduce and study experimentally experimental self formed channels tend to widen and subdivide leading to a braided pattern cohesive sediment has been the main mechanism studied for stabilizing banks and producing a single thread channel we show how laboratory experiments using vegetation to stabilize banks can organize the flow and convert the planform morphology from braided to single thread our experimental strategy a repeated cycle of short periods of high water discharge alternating with longer periods of low discharge accompanied by plant seeding and growth leads to the evolution of a dynamic self maintaining single thread channel with well defined banks and floodplain by eliminating weak flow paths the vegetation corrals the water into a single dominant channel until the reduction in total wetted width leads to a new self organized state in which the flow removes vegetated area as fast as it is produced the new channel is deeper and has a broader distribution of depths than the braided one with channel size adjusted to carry almost all the flood flow the resulting system maintains a dynamic steady state via similar mechanisms to those that operate in meandering channels in the field specifically erosion at the outside of bends bend growth and bar development our methodology provides a basis for experimental development of self sustaining high amplitude meanders and has applications for river management and basic research purposes