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

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

interannual kinetics 2010 2013 of large wood in a river corridor exposed to a 50 year flood event and fluvial ice dynamics abstract semi alluvial rivers of the gaspe peninsula quebec are prone to produce and transport vast quantities of large wood lw the high rate of lateral erosion owing to high energy flows and noncohesive banks is the main process leading to the recruitment of large wood which in turn initiates complex patterns of wood accumulation and reentrainment within the active channel the delta of the saint jean river sjr has accumulated large annual wood fluxes since 1960 that culminated in a wood raft of 3 km in length in 2014 to document the kinetics of large wood on the main channel of sjr four annual surveys were carried out from 2010 to 2013 to locate and describe 1000 large wood jams lwj and 2000 large wood individuals lwi along a 60 km river section airborne and ground photo video images were used to estimate the wood volume introduced by lateral erosion and to identify local geomorphic conditions that control wood mobility and deposits video camera analysis allowed the examination of transport rates from three hydrometeorological events for specific river sections results indicate that the volume of lw recruited between 2010 and 2013 represents 57 of the total lw production over the 2004 2013 period volumes of wood deposited along the 60 km section were four times higher in 2013 than in 2010 increases in wood amount occurred mainly in upper alluvial sections of the river whereas decreases were observed in the semi alluvial middle sections observations suggest that the 50 year flood event of 2010 produced large amounts of lw that were only partly exported out of the basin so that a significant amount was still available for subsequent floods large wood storage continued after this flood until a similar flood or an ice breakup event could remobilise these lw accumulations into the river corridor ice jam floods transport large amounts of wood during events with fairly low flow but do not contribute significantly to recruitment rates ca 10 to 30 early it is fairly probable that the wood export peak observed in 2012 at the river mouth where no flood occurred and which is similar to the 1 in 10 year flood of 2010 is mainly linked to such ice break events that occurred in march 2012

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

chromite typology and composition characterized through multispectral specular reflectance abstract determination of multispectral specular reflectance is an important tool for ore identification in reflected light microscopy and may be used for automated characterization of ores however reflectance values can be affected by compositional variations in a way that is seldom understood the aim of the present work is to investigate this problem in chromite an ore whose composition may show typically large natural variations as member of the spinel family and whose relatively high reflectance variations are apparently unpredictable for this research eighteen samples of chromian spinel covering a large range of compositions in the base of the hagerthy prism were selected for microprobe analysis and reflectance measure on polished sections the samples belong to a variety of deposits and types ultramafic massif ophiolitic and metamorphosed types ojen and ronda massifs spain mayari moa baracoa camaguey and sagua de tanamo cuba golyamo kemenyane avren and yakovitsa bulgaria the specular reflectances are characterized as multispectral values measured at thirteen intervals 50 nm each in the vnir region visible and near infrared 400 1000 nm using the automated cameva system the relationship between compositional and reflectance values is studied by multivariate analysis and subsequently tested on independent samples for this purpose the samples have been grouped in two sets a larger population of fifteen samples constitutes the initial data set for mathematical processing while a selection of three samples of widely differing compositions is used to test the resulting functions so as to gain a critical appraisal of their validity the results obtained show that the specular reflectance of chromite depends on composition and can be used to estimate compositional parameters as cr cr cr al or mg mg mg fe2 but this relationship is complex and does not allow simple direct determinations due to the multiplicity of possible changes and coupled substitutions e g al cr fe3 or mg fe2 ni zn ti in the chromian spinel family on the other hand the relationship of chromite composition with deposit type is also detectable through the reflectance values but with a higher uncertainty reflectance increases with increasing cr and fe3 contents in all cases but the relationship of reflectance with mg seems to be specific of the deposit type while reflectance increases with increasing mg in the ojen chromites it shows the opposite behaviour in podiform chromites although these results should be regarded as preliminary until further studies on larger sample populations can be achieved they are suggestive of possible practical applications for exploration e g to approach cr spinel compositions or chromite deposit typology early in an exploration campaign by inexpensive reflected light determination of specular reflectance in a few samples

the influence of organic debris on channel morphology and bedload transport in a new zealand forest stream the behaviour and form of and bedload sediment transport through a 3 5 m wide forest stream have been monitored for nearly three years bedload transport is highly episodic and spatially variable and is controlled less by water discharge than by sediment availability organic debris in the channel creates temporary base levels and sites at which coarse sediment may remain stored for long periods collapse or disruption of log and debris jams makes sediment available for transport in only a small proportion of the runoff events that are actually competent to move the material even then sediment travels only a short distance before being redeposited frequently behind debris accumulations further downstream rates of sediment transport during a given runoff event can vary markedly over short distances along the stream again depending on whether sediment was made available for transport by log jam collapse upstream organic debris is therefore a major constraint on the application of physical laws and theories to explaining sediment movement in and the morphology of this stream

structure and hydraulics of natural woody debris jams 1 numerous studies exist on the hydraulics of woody debris jams and the mechanisms driving their geomorphic influence while most hydraulic studies treat jams as single solid objects jams are clearly not individual cylindrical logs but rather an accumulation of pieces ranging in size from leaves and twigs to entire trunks here we treat debris jams as complex and porous accumulations of heterogeneous material to understand the relative importance of the different size fractions comprising a jam we systematically dismantled three deflector debris jams in four stages removing a total of 17 783 individual wood pieces to experimentally manipulate jam porosity we measured the surrounding velocity shear stress and drag force fd the assumption of nonporosity can result in a 10 20 overestimation of fd back calculated values of the combined drag coefficient and frontal area term cdaf calc represented the drag characteristics of natural debris jams whereas separating frontal area af emp and drag coefficient cd contributions in natural jams is misleading values of cdaf calc for each jam at each stage of removal captured the effects of size and composition of the jam wood piece size in debris jams dictates the surface area to volume relationship this association in turn determines the rate at which fd and cdaf calc change with the addition of material only low porosity jams produce the geomorphic and hydraulic characteristics commonly associated with deflector jams our results on natural debris jams also illustrate the importance of employing variable wood size fractions when using woody debris jams for river restoration

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

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

downstream variation in stream power abstract stream power has a significant influence on many form and process attributes of the fluvial system using a similar approach to that suggested by d m lawler in 1992 and 1995 a model is developed to explore how stream power might vary in the downstream direction based on the assumption that the longitudinal profile of the river has an exponential form no particular discharge is necessarily specified but near bankfull flows are regarded as significant morphologically and one such discharge is the focus here total stream power per unit channel length qs is predicted to peak at an intermediate location the position of which depends on the ratio b where b and are the downstream rates of change of discharge and slope respectively if b is a relatively conservative quantity then the form of the longitudinal profile and in particular its degree of concavity will have the major influence on the position of maximum stream power specific stream power w is even more sensitive to and is expected to peak closer to the headwaters about half way between source and the location of the stream power maximum although this will depend on how channel width w varies with distance from source the model is tested along three connected streams of different size in the catchment of the river trent taking advantage of a relationship between mean annual flood and link magnitude which enables this near bankfull discharge to be estimated at any point within the network the model is verified in so far as stream power does attain a mid basin maximum but the observed and predicted locations of the maxima do not always correspond largely because of the distinctive variation in discharge and especially slope along individual pathways for example maximum power lies far downstream along the trent because of the large increase in mid basin discharge associated with a series of large closely spaced tributaries the importance of slope is borne out by the near headwater locations for specific power maxima which tend to be further upstream than predicted along all three rivers as a result of the steepness of upper reaches the variety of geomorphic settings produces deviations from expectation which has implications for the movement and storage of material in the fluvial system

factors controlling large wood transport in a mountain river as with bedload transport wood transport in rivers is governed by several factors such as flow regime geomorphic configuration of the channel and floodplain or wood size and shape because large wood tends to be transported during floods safety and logistical constraints make field measurements difficult as a result direct observation and measurements of the conditions of wood transport are scarce this lack of direct observations and the complexity of the processes involved in wood transport may result in an incomplete understanding of wood transport processes numerical modelling provides an alternative approach to addressing some of the unknowns in the dynamics of large wood in rivers the aim of this study is to improve the understanding of controls governing wood transport in mountain rivers combining numerical modelling and direct field observations by defining different scenarios we illustrate relationships between the rate of wood transport and discharge wood size and river morphology we test these relationships for a wide multithread reach and a narrower partially channelized single thread reach of the czarny dunajec river in the polish carpathians results indicate that a wide range of quantitative information about wood transport can be obtained from a combination of numerical modelling and field observations and from document contrasting patterns of wood transport in single and multithread river reaches on the one hand log diameter seems to have a greater importance for wood transport in the multithread channel because of shallower flow lower flow velocity and lower stream power hydrodynamic conditions in the single thread channel allow transport of large wood pieces whereas in the multithread reach logs with diameters similar to water depth are not being moved on the other hand log length also exerts strong control on wood transport more so in the single thread than in the multithread reach in any case wood transport strongly decreases with increasing piece volume although this relation is not linear we also document a nonlinear relationship between wood transport and flood magnitude a threshold discharge was identified below which wood transport is negligible this threshold is higher in the multithread reach while in the single thread reach floods of lower magnitude are able to transport wood downstream wood transport ratio increases with discharge until it reaches an upper threshold or tipping point and then decreases or increases much more slowly this threshold is clearly related to bankfull discharge but it is much higher for the multithread reach than for the single thread one although modelling input and field observations were taken from a specific river our findings and conclusions are likely to be applicable to a much larger suite of mountain rivers

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

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

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

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

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

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

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

changes in the magnitude and transformation of flood waves subsequent to the channelization of the raba river polish carpathians alterations in flood flows of the raba river are examined to determine the influence exerted on flood waves by changing morphological conditions with stable vertical channel position the river increased its sinuosity during the 1920s to 1940s and the change was accompanied by a growing tendency to flood wave attenuation the temporal change in flood wave transformation is typical of a developing low flow system subsequently streambed degradation has been induced due to channnelization works which straightened and narrowed the river flood waves became progressively more flashy as channel incision progressed the increase in magnitude of flood waves passing the deepened reach was greatest for bankfull flows and diminished for lower in bank flows and higher overbank flows the tendency to magnification of peak discharges has been also found in other carpathian rivers which were considerably degraded in the 20th century in response to channelization introducing an empirically found correcting factor into the analysis of the ratio of outflow to inflow peak discharges shows how the conditions of peak flow transformation in a reach have changed since the beginning of the study period a marked coincidence between changes in vertical channel location and variations in the corrected peak discharge ratio proves channel changes to be a very important reason for the growing flood hazard in southern poland gradient oversteepening and channel narrowing caused by channelization lead to formation of a river system having a steep straight narrow and deep channel such a morphology distinguishes the system from natural low flow and high flow systems reduced floodplain water storage and self acceleration of flow concentrated in a channel zone make flood waves progressively more flashy on their way down the channelization formed system

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

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