if a tree falls in an urban stream does it stick around mobility characteristics and geomorphic influence of large wood in urban streams in northeastern ohio usa abstract large wood influences geomorphological ecological and biogeochemical functions of streams but in urban areas it is also considered an unaesthetic hazard quantifying the abundance and mobility of in stream wood along an urban intensity gradient and understanding the relationship between wood dynamics and stream reach network and watershed characteristics allows for a stronger understanding of the potential benefits and hazards of wood in urban streams repeat wood surveys were conducted at 11 stream reaches in the cleveland ohio area where wood removal is not practiced and forested riparian zones exist study reaches span a gradient of impervious surface cover and extent of the stream network with a forest buffer channel morphology and sediment size were also measured stream hydrology does not change when imperviousness is 12 40 in this region so quantification of impervious surfaces stands in for a broader suite of urban impacts wood abundance decreases and mobility increases as urban intensity in the watershed and along the stream network increases jams become smaller and less stable but the size and orientation of individual wood pieces do not change along an urban gradient over the 6 month study period wood mobility exceeded 100 in some of the most urbanized streams and transport distances are inferred to be on the order of 100s of meters there was a positive correlation between jam spacing and pool spacing and finer sediment sizes occurred in some wood associated deposits but overall geomorphic effects are limited where reaches are confined wood abundance is suppressed but impervious surfaces and the extent of forest along the stream network are stronger predictors of wood dynamics than reach scale characteristics these results emphasize the importance of situating understanding of reach scale wood dynamics in the context of larger scale phenomena

processes and rates of sediment and wood accumulation in headwater streams of the oregon coast range usa channels that have been scoured to bedrock by debris flows provide unique opportunities to calculate the rate of sediment and wood accumulation in low order streams to understand the temporal succession of channel morphology following disturbance and to make inferences about processes associated with input and transport of sediment dendrochronology was used to estimate the time since the previous debris flow and the time since the last stand replacement fire in unlogged basins in the central coast range of oregon debris flow activity increased 42 per cent above the background rate in the decades immediately following the last wildfire changes in wood and sediment storage were quantified for 13 streams that ranged from 4 to 144 years since the previous debris flow the volume of wood and sediment in the channel and the length of channel with exposed bedrock were strongly correlated with the time since the previous debris flow wood increased the storage capacity of the channel and trapped the majority of the sediment in these steep headwater streams in the absence of wood channels that have been scoured to bedrock by a debris flow may lack the capacity to store sediment and could persist in a bedrock state for an extended period of time with an adequate supply of wood low order channels have the potential of storing large volumes of sediment in the interval between debris flows and can function as one of the dominant storage reservoirs for sediment in mountainous terrain copyright 2003 john wiley sons ltd

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 giant oil seep at a salt induced escarpment of the sao paulo plateau espirito santo basin off brazil host rock characteristics and geochemistry abstract an international research cruise named iata piuna took place on the sao paulo plateau on may 2013 in the campos and espirito santo basins off brazil the cruise was carried ou on board the research vessel r v yokosuka that hosts the human operated vehicle hov shinkai 6500 it aimed at finding chemosynthetic communities composed of organisms capable of generating their own vital energy by metabolizing organic and inorganic compounds related to seeps identification of these organisms could provide information for understanding the origin of life since they may resemble primitive organisms that existed in the initial stages of life on earth during leg 2 may 10 24 2013 however dives on the northern part of the sao paulo plateau at the espirito santo basin led to the discovery of a giant oil seep the seep ca 3 nautical miles ca 5 6 km in length is located along an outcrop of eocene rocks on a salt induced escarpment of the plateau and at a water depth of ca 2700 m the 200 m relief of the seafloor suggests that the seep takes place along an active fault system driven by salt diapirism the oil was analyzed and identified as a severely biodegraded marine oil generated by carbonate rocks within a minibasin located to the east of the escarpment this represents valuable exploratory information because it proves that an active petroleum system is present in the context of minibasins associated with salt diapirism in the area

a transtensional basin model for the organya basin central southern pyrenees based on magnetic fabric and brittle structures summary the purpose of this paper is to explain the kinematics of the inverted extensional organy basin centralsouthernpyrenees duringitsextensionalevolution thestudyoftheanisotropy of magnetic susceptibility ams and the study of brittle mesostructures are the instruments used to decipher the extensional kinematics separation of magnetic subfabrics analyses of ams at low temperature and anisotropy of the anhysteretic remanence aarm has been also done to properly interpret the obtained magnetic fabric data the combination of all magnetic fabric and brittle mesostructures analyses has provided new information to clarify thestructuralevolutionofthebasin whichsupportanewtectonicmodelfortheaptian albian basinal stage 20 sites for the magnetic fabric analysis were sampled in aptian lower albian marls the ams ellipsoids obtained at room temperature show their kmin axes perpendicular to bedding and kmax axes oriented nw se in 70 per cent of the samples n s in 15 per cent and ne sw in 15 per cent analyses of ams at low temperature show a better clustering of the axes of the magnetic ellipsoid pointing out that phyllosilicates constitute the carriers of the ams whereas the analyses of the aarm confirm the scattering of the ferromagnetic grains these results suggest that the obtained ams in the organy a basin was acquired during or shortly after deposition of the aptian lower albian marls without any subsequent overprint the direction of the magnetic lineation obtained from the ams at room and low temperatures agrees with the orientation of the stress axes obtained from the analysis of brittle mesostructures mainly faults and calcite filled tension gashes indicating its tectonic origin we interpret the orientation of the magnetic ellipsoids related to the transtensional movements linked to the formation of the organy a basin during the aptian albian interval which are consistent with the eastward displacement and rotation of iberia with respect to europe analysis oftensiongashesalsoindicatesamainnw seextensiondirection whereaspalaeostressanalysis of striated faults shows a more n s trending 3 the transtensional model proposed from magnetic fabric and brittle mesostructures for the organy a basin during the aptian albian is consistent with the creation of a strongly subsiding area south of the axial zone during the cretaceous and implies that rotation and separation of iberia respect to europe took place simultaneously

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

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

cretaceous tertiary tectonic inversion of the cotiella basin southern pyrenees spain the cotiella nappe includes one of the most important mesozoic basins of the southern pyrenees which was subsequently inverted during the tertiary compression the late cretaceous cotiella basin is here interpreted as the western sector of the cretaceous cotiella boixols basin 100 20 km wide located in the central part of the southern pyrenees the present day complex structure of the cotiella nappe is the result of the inversion process linked to the emplacement of basement thrust sheets of the axial zone in its western sector the cotiella nappe consists of several superimposed thrust sheets with complex geometry becoming simpler towards the east with a single thrust surface and smaller displacements the cotiella boixols basin underwent strong subsidence during the early cretaceous at its eastern sector and its depocentre migrated westward during the late cretaceous the reconstruction of the sedimentary basin to the pre compressional stage shows that during the mesozoic the cotiella boixols basin was located to the south of a basement high which later became the pyrenean axial zone from a balanced cross section it can be inferred that the cotiella north verging extensional system was connected with the north pyrenean rift by means of a 10 km deep horizontal detachment the compressional tertiary detachment within the upper crust was shallower than the extensional detachment and individualised four basement thrust sheets which form the axial zone antiform

mapping the spatial and temporal distributions of woody debris in streams of the greater yellowstone ecosystem usa the objectives of this study were 1 to document spatial and temporal distributions of large woody debris lwd at watershed scales and investigate some of the controlling processes and 2 to judge the potential for mapping lwd accumulations with airborne multispectral imagery field surveys were conducted on the snake river soda butte creek and cache creek in the greater yellowstone ecosystem usa the amount of woody debris per kilometer is highest in 2nd order streams widely variable in 3rd and 4th order streams and relatively low in the 6th order system floods led to increases in woody debris in 2nd order streams floods redistributed the wood in 3rd and 4th order streams removing it from the channel and stranding it on bars but appeared to generate little change in the total amount of wood throughout the channel system the movement of woody debris suggests a system that is the reverse of most sediment transport systems in mountains in 1st and 2nd order tributaries the wood is too large to be moved and the system is transport limited with floods introducing new material through undercutting but not removing wood through downstream transport in the intermediate 3rd and 4th order channels the system displays characteristics of dynamic equilibrium where the channel is able remove the debris at approximately the same rate that it is introduced the spatial distribution and quantity of wood in 3rd and 4th order reaches varies widely however as wood is alternatively stranded on gravel bars or moved downstream during periods of bar mobilization in the 6th order and larger channels the system becomes supply limited where almost all material in the main stream can be transported out of the central channel by normal stream flows and deposition occurs primarily on banks or in eddy pool environments attempts to map woody debris with 1 m resolution digital four band imagery were generally unsuccessful primarily because the imagery could not distinguish the narrow logs within a pixel from the surrounding sand and gravel background and due to problems in precisely coregistering imagery and field maps

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

tree roots as a dominant agent of streambed habitat profile pattern and grade control abstract tree roots are a ubiquitous biotic agent in numerous fluvial settings but their role in controlling streambed habitat and profile patterns is understudied although their importance in resisting bank erosion is more widely reported tree roots also have the potential to span the channel bed particularly in narrower first to third order streams this enables tree roots to drive profile patterns and maintain important habitat elements such as steps that induce deep pools in both perennial and ephemeral systems in a study across two humid temperate ecoregions tree roots were associated with more abundant and larger steps than large wood lw forming 91 of the steps in the high gravel load setting and 40 of the steps in the steeper coarser low sediment supply setting when combined with lw a majority of the steps in both settings were formed by biotic agents 97 and 55 respectively furthermore 70 of the deepest pools across all 40 study reaches were associated with biotic controls with root steps being the most dominant driver 45 of the deepest pools in all study reaches including the maximum pool depths measured in both ecoregions 0 57 m and 0 38 m respectively many questions need further exploration for example what tree sizes and species are most likely to form root steps i e trunk diameters 40 cm and american sycamore platanus occidentalis in this study however even this somewhat limited study has clear implications to land use planning and stormwater management for example on land developments draining to root step dominated streams maintaining the integrity of the riparian zone would seem to be as important as ensuring hydrologic mimicry if channel integrity is to be preserved the study also has insights to the stream restoration industry where conventional practice typically involves large tree clearing operations to facilitate stream regrading

channel reach morphology in mountain drainage basins a classification of channel reach morphology in mountain drainage basins synthesizes stream morphologies into seven distinct reach types colluvial bedrock and five alluvial channel types cascade step pool plane bed pool rime and dune ripple coupling reach level channel processes with the spatial arrangement of reach morphologies their links to hillslope processes and external forcing by confinement ripar ian vegetation and woody debris defines a process based framework within which to assess channel condition and response potential in mountain drainage basins field investigations demonstrate character istic slope grain size shear stress and roughness ranges for different reach types observations consistent with our hypothesis that alluvial channel morphologies reflect specific roughness configurations ad justed to the relative magnitudes of sediment supply and transport ca pacity steep alluvial channels cascade and step pool have high ratios of transport capacity to sediment supply and are resilient to changes in discharge and sediment supply whereas low gradient alluvial channels pool rime and dune ripple have lower transport capacity to supply ra tios and thus exhibit significant and prolonged response to changes in sediment supply and discharge general differences in the ratio of transport capacity to supply between channel types allow aggregation of reaches into source transport and response segments the spatial distribution of which provides a watershed level conceptual model linking reach morphology and channel processes these two scales of channel network classification define a framework within which to in vestigate spatial and temporal patterns of channel response in moun tain drainage basins

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

influence of vertical channel change associated with wood accumulations on delineating channel migration zones washington usa we combine hydraulic modeling and field investigations of logjams to evaluate linkages between wood mediated fluctuations in channel bed and water surface elevations and the potential for lateral channel migration in forest rivers of washington state in the eleven unconfined rivers we investigated logjams were associated with reduced channel gradient and bank height detailed river gauging and hydraulic modeling document significant increases in the water surface elevation upstream of channel spanning wood accumulations logjams initiated lateral channel migration by increasing bed or water surface elevations above adjacent banks because the potential for a channel to avulse and migrate across its floodplain increases with the size and volume of instream wood the area of the valley bottom potentially occupied by a channel over a specified timeframe the channel migration zone cmz is dependent on the state of riparian forests the return of riparian forests afforded by current land management practices will increase the volume and caliber of wood entering washington rivers to a degree unprecedented since widespread clearing of wood from forests and rivers nearly 150 years ago a greater supply of wood from maturing riparian forests will increase the frequency and spatial extent of channel migration relative to observations from wood poor channels in the period of post european settlement we propose conceptual guidelines for the delineation of the cmzs that include allowances for vertical fluctuations in channel elevation caused by accumulations of large woody debris

morphological organization of a steep tropical headwater stream the aspect of channel bifurcation abstract channel characterization and instream wood surveys demonstrate the spatial complexity of an ungauged tropical headwater stream hws in the tilaran mountains of costa rica throughout the stream course we characterized 29 individual reaches based on their morphological organization and instream wood occurrences bifurcated reaches were the most numerous and consistently distributed they also had the highest values of wood abundance and loading and contained the majority of unattached instream wood we selected two bifurcated reaches for ultrahigh resolution terrestrial laser scanning tls surveys orthographic tls produced millimeter resolution point cloud data sets from which 2 cm planimetric resolution digital elevation models dems of the channel surface were derived for both reaches cross sectional surveys of these dems using the river bathymetry toolkit rbt produced hydraulic geometries at two flow levels high and low for every meter length of channel reach we input these geometries into a one dimensional analytical model to demonstrate the downstream evolution of mean stream power through varying morphology elements mean stream power variation displays a regular pattern through the vertical modulation of step pool sequences but this regular pattern is lost through channel widening and bifurcation reach geometric data indicates that increasing width to depth ratio is the most notable feature of channel bifurcation and corresponds to a reduction in slope and roughness variation this primary understanding of channel dynamics denotes the complex organization of a tropical hws and promotes further research into tropical hws systems

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

fluvial processes in a forested anastomosing river flood partitioning and changing flow patterns in an effort to further our understanding of multiple channel systems this paper presents data on the flood response of channels in one of the last wooded semi natural anastomosing systems in europe the gearagh ireland is characterized by hundreds of small islands separated by interconnected channels of low slope these include channels that cross islands at right angles to the main flow and blind anabranching channels islands are relatively stable and wooded with evidence of division by channel erosion and growth by in channel sedimentation four active zone cross profiles were surveyed each containing between seven and 13 channels velocities were measured in several channels before and during two separate floods from these observations channels have been categorised into three types fast shallow and trapezoidal slow deep and more irregular and flood channels during the floods interchannel flows were caused by variations in water surface elevations due to backing up behind debris dams and it is suggested that this is the origin of the anomalous cross island channels and one cause of island division another potential cause of island division blind anabranching channels is the result of concentrated bank scour between root masses biotic components such as debris dams tree root masses and tree throw pits play a key role in the partitioning of flow and cause variations in channel velocities and the overbank velocity distribution the implications of these observations for channel pattern maintenance are briefly discussed

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

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

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

reach scale characterization of large woody debris in a low gradient midwestern u s a river system abstract addition of large woody debris lwd to rivers has increasingly become a popular stream restoration strategy particularly in river systems of the midwestern united states however our knowledge of lwd dynamics is mostly limited to high gradient montane river systems or coastal river systems the lwd related management of low gradient midwestern river systems is thus largely based on higher gradient analogs of lwd dynamics this research characterizes fluvial wood loads and investigates the relationships between fluvial wood channel morphology and sediment deposition in a relatively low gradient semiconfined alluvial river the lwd and channel morphology were surveyed at nine reaches along the big river in southeastern missouri to investigate those relationships in comparison to other regions wood loads in the big river are low 3 114 m 3 100 m relative to those of higher gradient river systems of the pacific northwest but high relative to lower gradient river systems of the eastern united states wood characteristics such as size and orientation suggest that the dominant lwd recruitment mechanism in the big river is bank erosion also ratios of wood geometry to channel geometry show that the big river maintains a relatively high wood transport capacity for most of its length although lwd creates sites for sediment storage the overall impact on reach scale sediment storage in the big river is low

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

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

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

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

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

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