tree roots methodological review and new development in dating and quantifying erosive processes exposed roots have been used in dendrogeomorphology since the 1960s to determine erosion rates this was done by using the root axis as the relative position of the former soil layer and then relating this measure to the age of the root in order to quantify the amount of soil erosion over time recently wood anatomical research revealed the possibility of determining the first year of exposure of roots due to specific anatomical changes within the respective annual ring as a consequence using exposed roots that are still in contact to the soil surface it is possible to reconstruct the size and position of the root at the time of exposure consequently a new equation is presented to calculate the thickness of the eroded soil layer allowing a detailed reconstruction of erosion rates the technique also helps to determine if the root was exposed by erosional processes or just by its ongoing secondary growth without any erosion involved

the geomorphic impacts of culverts at paved forest roads examples from carpathian headwater channels czech republic abstract road stream crossings constructed with culverts have the potential to alter geomorphic processes in adjacent stream channels we examined changes in channel geometry and bed sediments in longitudinal profiles related to culverts at five paved forest road crossings with perennial headwater streams and two gullies initiated by point releases of water through ditches a dendrogeomorphic approach was used for dating of exposed tree roots and estimation of bank erosion rates in incised cross sections downstream of road crossings the studied forest road crossings concentrate surface runoff from the road net act as stabilizing elements in stream longitudinal profiles and decelerate bedload transport in the case of culvert clogging which caused notable upstream and downstream changes in fluvial processes notable fining of the coarsest fraction in upstream cross sections was observed only for two culverts with the highest depositional tendencies much lower width depth ratios 1 and the erosion occurred over 2 5 year intervals depending on the studied location the highest number of observed changes in cross sectional geometry caused by channel erosion were connected with relatively high magnitude flow events with recurrence intervals 10 years specific discharge 1500 l s km 2 whereas more frequent flows with recurrence intervals of 2 10 years were not always recorded by exposed tree roots

mapping of erosion rates in marly badlands based on a coupling of anatomical changes in exposed roots with slope maps derived from lidar data black marls form very extensive outcrops in the alps and constitute some of the most eroded terrains thus causing major problems of sedimentation in artificial storage systems e g reservoirs and river systems in the experimental catchments near draix france soil erosion rates have been measured in the past at the plot scale through a detailed monitoring of surface elevation changes and at the catchment scale through continuous monitoring of sediment yield in traps at basin outlets more recently erosion rates have been determined by means of dendrogeomorphic techniques in three monitored catchments of the draix basin a total of 48 exposed roots of scots pine have been sampled and anatomical variations in annual growth rings resulting from denudation analysed at the plot scale average medium term soil erosion rates derived from exposed roots vary between 1 8 and 13 8 mm yr 1 average 5 9 mm yr 1 and values are significantly correlated with slope angle the dendrogeomorphic record of point scale soil erosion rates matches very well with soil erosion rates measured in the draix basins based on the point scale measurements and dendrogeomorphic results obtained at the point scale a linear regression model involving slope angle was derived and coupled to high resolution slope maps obtained from a lidar generated digital elevation model so as to generate high resolution soil erosion maps the resulting regression model is statistically significant and average soil erosion rates obtained from the areal erosion map 5 8 5 2 and 6 2 mm yr 1 for the roubine moulin and laval catchments respectively prove to be well in concert with average annual erosion rates measured in traps at the outlet of these catchments since 1985 6 3 4 1 and 6 4 mm yr 1 this contribution demonstrates that dendrogeomorphic analyses of roots clearly have significant potential and that they are a powerful tool for the quantification and mapping of soil erosion rates in areas where measurements of past erosion is lacking copyright 2011 john wiley sons ltd

late quaternary large scale rotational slides induced by river incision the arroyo de gor area guadix basin se spain the arroyo de gor is a highly incised stream up to 200 m that has eroded into the pliocene pleistocene infill of the guadix basin in the betic cordillera se spain this paper concentrates on a particular reach of this stream namely the cenascuras gorafe reach where abundant inactive rotational slides can be recognized on both hillslopes of the canyon shaped valley the rotational slides have surface areas of 5 15 ha and volumes of mobilized material of 5 15 hm3 these rotational slides can be recognized by their main scarps which are still well featured at both margins of the valley as well as by the counter hillslope rotation of the strata in their bodies the surfaces of rupture are concave their width being greater than their length i e the landslides are elongated in a direction perpendicular to the landsliding displacement and parallel to the stream at depth the surfaces of rupture developed on fine grained sediments mostly clays underlying the conglomerates and sands affected by the rotational slides the clays at the surface of rupture are smectite rich and show several features produced by the landsliding such as striations and sigmoidal shaped structures the cenascuras gorafe canyon has been developed by a combination of entrenchment fracturing and landsliding initial deep entrenchment of the stream is attributed to a base level lowering related to the capture of the former endorheic basin by the gualdalquivir river in the late pleistocene this river incision created a canyon with subvertical unstable walls which due to gravitational instability would give way to vertical open tension cracks some distance from the canyon edge the tension cracks would end at depths equal to the base of the canyon which also coincides with the contact between the conglomerates and the underlying clays the rotational slides are thought to have occurred during heavy rains by a combination of piping which would have lengthened the tension cracks and infiltration which would reduce the shear strength along the gently dipping contact between conglomerates and the underlying clays thus the blocks bounded by the tension cracks and the subhorizontal lithological contact would slide under their own weight on the subhorizontal surfaces of reduced shear strength several age constraints lead us to tentatively assign the landslides to the isotope stage 5 around 32 ka an interglacial period agreed to be wetter and slightly warmer than the present day semi arid climate

holocene coastal environments and processes in subantarctic temperate cold tierra del fuego argentina chile fil bujalesky gustavo gabriel consejo nacional de investigaciones cientificas y tecnicas centro austral de investigaciones cientificas argentina

analysis of changes in the step pool morphology and channel profile of a steep mountain stream following a large flood abstract the step pool morphology of steep mountain streams is reorganized during large floods by the removal of steps scouring of the channel bed and the formation of a new step pool sequence by the re deposition of step forming grains in this paper we document these changes caused by the largest recorded flood return period 50 years in the steep mountain stream erlenbach in central switzerland in 2007 by comparing pre flood and post flood surveys of a 650 m long study reach we show that the flood led to statistically significant changes in the distributions of step height and spacing most notably an increase in the variance of both variables organization at the river reach scale is not apparent and the correlations between step properties both pre and post flood are generally weak the flood led to widespread erosion of the river bed locally up to 2 3 m of vertical channel change was observed at least 60 of the steps moved even the largest ones however they remained constrained to the parts of the study reach where landslides on the adjacent hillslopes are most active detailed changes in bed structure were analyzed from the pre and post flood profiles with a statistical scaling approach which identifies the complexity of the spatial organization of sediment in the longitudinal profile multiscaling found in both step and pool sequences reflects the complex spatial structure which is the result of the superposition of steps formed by the history of flood events

effective discharge in rocky mountain headwater streams summary whereas effective discharge q eff in mountain streams is commonly associated with a moderate flow such as bankfull discharge q bf this study found that the maximum discharge q max and not bankfull discharge is the channel forming or effective flow for gravel transport in plane bed streams where partial bed mobility causes steep gravel transport rating curves q eff may approach bankfull flow in some step pool channels where gravel moves over a static cobble boulder bed our conclusions are based on magnitude frequency analyses conducted at 41 gauged rocky mountain headwater streams because these gauged streams lacked gravel transport data as is typical comparable streams with measured transport rates were used to develop scaling relations for rating curve exponents with stream and watershed characteristics those scaling relations were then used to estimate the steepness of gravel rating curves at the 41 gauged but unsampled sites the measured flow frequency distributions were characterized by two fitted power functions the steepness of the flow frequency distributions and the estimated steepness of gravel transport relations were combined in magnitude frequency analyses to compute q eff

medium term effects of two landsliding episodes on channel storage of sediment two landsliding episodes between late 1973 and early 1975 delivered about 60000 m3 of sediment to six small deeply incised streams draining a 2 7 km2 area about 4700 m3 of logs in the landslide debris formed major log jams in five streams which impounded large volumes of landslide derived sediment five years after the landsliding 42 per cent 25000 m3 of sediment was still in storage behind 35 log jams ranging from 1 4 8 2 m high the landsliding episodes have produced multi stepped stream profiles aggradation of channel reaches up to 150 m long to mean depths between 1 2 and 4 1 m reductions in gradient fining of bed material size and related changes in bedforms and channel width depth ratios that seem likely to persist for at least several decades sediment presently stored behind log jams is equivalent to between 50 and 220 years normal supply of sediment from hillslopes to stream channels long delayed large magnitude impacts on higher order channels may occur if sudden failure of log jams is induced by a large storm at some future date

coarse sediment connectivity in river channel systems a conceptual framework and methodology identification of coarse sediment connectivity down river channel systems is important for understanding the linkages between river reaches the influence of sediment sources on channel morphology and the mechanisms and liability to propagation of morphological change a conceptual framework is developed in which several types and degrees of connectivity are proposed it is hypothesised that sediment connectivity varies with sediment sources and with stream competence to transport the coarse fractions a method of identifying the status of reaches is developed based on field mapping of morphology and sedimentology the analysis is exemplified by two channels one an ephemeral channel in se spain the other a perennial channel in nw england questions arise over whether reaches that lack channel stores transfer coarse sediment three scenarios are suggested 1 lack of flux due to lack of competence of the reach 2 flushing through of sediment due to high competence and 3 potential transport of coarse sediment but exhaustion or lack of availability changes in connectivity will take place over different time scales depending on the nature of exchange and time scales of storage short term variations in connectivity can be identified by repeated mapping

geomorphic effects flood power and channel competence of a catastrophic flood in confined and unconfined reaches of the upper lockyer valley southeast queensland australia flooding is a persistent natural hazard and even modest changes in future climate are believed to lead to large increases in flood magnitude previous studies of extreme floods have reported a range of geomorphic responses from negligible change to catastrophic channel change this paper provides an assessment of the geomorphic effects of a rare high magnitude event that occurred in the lockyer valley southeast queensland in january 2011 the average return interval of the resulting flood was similar to 2000 years in the upper catchment and decreased to similar to 30 years downstream a multitemporal lidar derived dem of difference dod is used to quantify morphological change in two study reaches with contrasting valley settings confined and unconfined differences in geomorphic response between reaches are examined in the context of changes in flood power channel competence and degree of valley confinement using a combination of one dimensional 1 d and two dimensional 2 d hydraulic modelling flood power peaked at 9800 w m 2 along the confined reach and was 2 3 times lower along the unconfined reach results from the dod confirm that the confined reach was net erosional exporting similar to 287 000 m 3 of sediment whilst the unconfined reach was net depositional gaining similar to 209 000 m 3 of sediment 70 of the amount exported from the upstream confined reach the major sources of eroded sediment in the confined reach were within channel benches and macrochannel banks resulting in a significant increase of channel width in the unconfined reach the benches and floodplains were the major loci for deposition whilst the inner channel exhibited minor width increases the presence of high stream power values and resultant high erosion rates within the confined reach is a function of the higher energy gradient of the steeper channel that is associated with knickpoint development dramatic differences in geomorphic responses were observed between the two adjacent reaches of contrasting valley configuration the confined reach experienced large scale erosion and reorganisation of the channel morphology that resulted in significantly different areal representations of the five geomorphic features classified in this study c 2013 elsevier b v all rights reserved

sediment un balance budget in a high gradient stream on flysch bedrock a case study using dendrogeomorphic methods and bedload transport simulation abstract detailed quantification of material supply into stream channels is crucial for determining sediment un balance budget during flood events unfortunately existing quantification methods require long term field monitoring otherwise there is an insufficient amount of usable data in this study we introduce a new approach based on dendrogeomorphic methods to determine the volume of material supply generated from flysch high gradient stream bank failures this approach was supplemented by 1d sediment transport modelling using a tomsed model we analysed 138 cross sections from the roots of predominantly broad leaved trees which were exposed in bank failures from different floods using the spatial position of the roots and dating the exposure time we determined the volume of material supply into the channel during the last flood in 2010 in channel sediment transport was analysed on 14 cross sections and the channel sediment thickness was estimated using the geophysically based ert electrical resistivity tomography method the total volume of material loss during the 2010 flood within the study area according to the tomsed model was found to be at least 300 m3 this means that the calculated total volume of sediment supply resulting from bank failures during the flood 63 9 m3 based on dendrogeomorphic methods was significantly lower than the calculated bedload transport for the entire study area this finding implies that contemporary sediment sources cannot adequately cover the transport capacity during high magnitude flood events and in general in channel erosion processes prevail

initial stages and evolution of recently abandoned meanders revealed by multi proxy methods in the odra river czech republic abstract oxbow lakes represent important geomorphic and depositional units of meandering river systems whose rates of sediment accumulation may significantly exceed those of surrounding floodplains natural and artificial oxbow lakes may differ considerably although both can offer unique sedimentary records of recent past events in river catchments we provide an insight into the initial stages of oxbow lake evolution in terms of morphology dynamics sediment accumulation rates sediment architecture and switching between sediment source areas the study is based on a combination of geomorphic observations multi proxy stratigraphic analysis and geochemistry of sediment cores in four abandoned meanders of the odra river in the northeastern part of the czech republic two of the meanders were formed in non regulated parts of the floodplain following a flood in 2010 in addition two abandoned meanders formed by the artificial shortening of an upstream section of the odra river were studied in order to compare processes in both sections several site specific factors controlled the sedimentation patterns in the naturally abandoned meanders the initial stages of oxbow lake succession were characterised by extremely high sediment accumulation rates up to 32 cm yr which caused the stara b la abandoned meander to completely fill up over the course of several years relative to natural oxbow lakes artificial lake successions revealed much slower sedimentation rates and higher levels of organic sedimentation and eutrophic conditions the accumulation rates were influenced by both local oxbow lake size position and geometry and catchment wide factors sediment yield the annual occurrence of low magnitude floods was an important factor in the natural reaches of the odra river the geochemical composition of sediments in naturally and anthropogenically formed abandoned meanders also differed due to the fact that the river tributaries drain two geologically contrasting areas the variscan bohemian massif and the cretaceous cenozoic outer western carpathians respectively

bankfull width and morphological units in an alpine stream of the dolomites northern italy abstract this research examines variations in bankfull cross sections along a steep stream of the dolomites cordevole stream belluno northern italy field measurements were conducted to determine variations in the channel top width at bankfull stage in relation to the drainage area and to the length of the flow path after grouping the bed morphologies according to the montgomery and buffington montgomery d r buffington j m 1997 channel reach morphology in mountain drainage basins geol soc of am bull 109 5 596 611 classification we analyzed the increase in bankfull width for the dominant stream units cascades step pools isolated pools and colluvial reaches at the head of the basin we observed that the morphologies more related to the drainage area are colluvial reaches and pools the less adaptable are steps and cascades these differences likely result from the absence of lateral constriction in the colluvial reaches and pools whereas the presence of coarser sediments in the bed can affect the transverse adjustments in steps and reaches dominated by cascades linkages between cross section geometry and parameters related to flow i e drainage area and stream power have been analyzed together with the distribution of surface grain sizes and its coarsening pattern the existence of distinctive bankfull widths between different morphological units points out the degree of susceptibility to be modeled according to the channel slope reference diameter d90 and contributing area

sediment budgets for two mountainous basins affected by a catastrophic storm blue ridge mountains virginia on june 27th 1995 a catastrophic storm generated thousands of slope failures in mountainous portions of madison county va usa within a 129 km2 area 16 h rainfall totals reached 775 mm using direct field measurements sediment budgets were constructed for two drainage basins impacted by the event teal and jenkins hollows lengthwise distributions of channel erosion and deposition were examined by taking measurements within incremental 30 m long channel segments comparison of sediment budgets reveals that the two hollows responded very differently to the storm event these differences are largely due to differences in soil types failure volumes and natures of the resulting flows within jenkins hollow the kinetic energy of a 4200 m3 liquefied slope failure scoured the channel of virtually all sediment and vegetation and resulted in a sediment retention rate of 5 in contrast slope failures that reached the central channel of teal hollow failed to generate a large flow track and erosion features are coupled with deposition features the sediment retention rate in teal hollow was 27 single storm denudation rates for the basins exceed the regional 1 ka area normalized denudation rate of 25 5 mm ka 1 denudation was 27 mm in teal hollow and 38 mm in jenkins hollow following catastrophic events considerable attention has been paid to those channels dramatically modified by debris flows the high denudation rate for teal hollow attributed to liquefaction of fine grained soils easily transported as washload suggests that extremely high denudation rates are possible even in low order mountainous basins that appear relatively undisturbed by catastrophic storms

geomorphic impact and system recovery following an extreme flood in an upland stream thinhope burn northern england uk abstract quantitative assessments of the impacts of extreme floods on channel morphology are rare real time kinematic rtk gps surveys of a 500 m reach of the thinhope burn an upland gravel bed stream in the uk taken in 2003 and 2004 permitted an assessment of geomorphic work whilst the channel was at steady state a large flood that occurred on 17 july 2007 resulted in a catastrophic impact to the thinhope burn valley floor the reach was re surveyed after the event in 2007 and again in 2008 and in 2011 digital elevation models were produced from the survey data which allowed the spatial patterns of erosion and deposition and volumetric changes between surveys to be established a total of 5202 m3 of deposition and 2125 m3 of erosion was recorded in the reach following the flood event field walking of the catchment and comparison of aerial photographs for 2003 and 2007 suggested that most of the material mobilised had originated from existing sediment held in terraces and paleoberms on the valley floor although slope failures were evident including peat slides in the headwaters delivery of sediment from coupling zones to the channel was thought to play a secondary role in the geomorphic response shown by the channel similarly large volumes of erosion and deposition were found after resurveys in 2008 and 2011 suggesting that the system was still in its relaxation phase the results obtained in this investigation coupled with historical information on the flood history of thinhope burn dating back to 1766 suggested that rare large floods are the geomorphically effective flows in the catchment

sediment supply grain protrusion and bedload transport in mountain streams 1 steep streams occupy a large fraction of mountainous drainage basins and partially control the sediment supplied to downstream rivers in these channels sediment transport equations typically over predict bedload flux by several orders of magnitude because they do not account for sediment supply limited conditions thus accurate predictions of bedload flux require an estimate of the sediment available for transport in a given event we demonstrate through field measurements that boulder step protrusion is a proxy for sediment availability protrusion is also a function of the time elapsed since an extreme event and this simple relationship can be used to estimate the relative sediment availability at any given time in addition bedload transport predictions in a steep channel were only accurate if they included this variable protrusion predictions of sedimentation hazards water quality river restoration success long term channel network evolution and channel stability may therefore require estimates of sediment availability for transport

chronology of processes in high gradient channels of medium high mountains and their influence on the properties of alluvial fans abstract high gradient channels are the locations of the greatest geomorphological activity in medium high mountains the channels frequency and character influence the contemporary morphology and morphometry of alluvial fans there is currently no detailed information regarding the frequency of these processes in high gradient channels and the evolution of alluvial fans in medium high mountains in central europe this study in the moravskoslezske beskydy mts analysed 22 alluvial fans 10 debris flow fans and 12 fluvial fans the processes occurring on the fans were dated using dendrogeomorphological methods a total of 748 increment cores were taken from 374 trees to reconstruct 153 geomorphological process events 60 debris flow and 93 floods the frequency of the processes has been considerably increasing in the last four decades which can be related to extensive tree cutting since the 1970s processes in high gradient channels in the region affecting the alluvial fans across the mountain range are predominantly controlled by cyclonal activity during the warm periods of the year probable triggers of local events are heavy downpours in the summer in addition spring snowmelt has been identified as occasionally important this study of the relations affecting the type and frequency of the processes and their effect on the properties of alluvial fans led to the creation of a universal framework for the medium high flysch mountains of central europe the framework particularly reflects the influence of the character of hydrometeorological extremes on the frequency and type of processes and their reflection in the properties of alluvial fans

holocene reactivations of catastrophic complex flow like landslides in the flysch carpathians czech republic slovakia catastrophic complex flow like landslides cflls are characterised by a deep seated retrogressive landslide of structurally unfavourably oriented rocks and earthflows that occupy the lower slope positions and originate due to the liquefaction of material accumulated on the upper slopes these landslides are locally important geomorphic agents of late quaternary mountain evolution in the flysch belt of the outer western carpathians czech republic slovakia most of the cflls dammed and steepened adjacent valleys radiocarbon dating suggests that a majority of them moved repeatedly throughout the holocene namely approx every 1 2 ka dated events occurred during humid phases of the younger dryas holocene transition 11 5 9 4 cal ka bp atlantic chronozone 7 4 6 6 cal ka bp the beginning of the subboreal chronozone ca 4 6 cal ka bp and primarily within the subatlantic chronozone at ca 2 0 8 cal ka bp 50 of all events our study suggests that slopes based on an unfavourable structural setting and affected by long term deep seated gravitational deformations may produce cflls even if they are located in medium high mountains although our chronological dataset is influenced by the erosion of older landforms most of the dated reactivations correlate with regional increase in precipitation identified by previous palaeoenvironmetal studies

impact of a large flood on mountain river habitats channel morphology and valley infrastructure abstract the biala river polish carpathians was considerably modified by channelization and channel incision in the twentieth century to restore the biala establishing an erodible corridor was proposed in two river sections located in its mountain and foothill course in these sections longer unmanaged channel reaches alternate with short channelized reaches and channel narrowing and incision increases in the downstream direction in june 2010 an 80 year flood occurred on the river and this study aims at determining its effects on physical habitat conditions for river biota channel morphology and valley floor infrastructure surveys of 10 pairs of closely located unmanaged and channelized cross sections performed in 2009 and in the late summer 2010 allowed us to assess the flood induced changes to physical habitat conditions a comparison of channel planforms determined before 2009 and after 2012 the flood provided information on the degree of channel widening as well as changes in the width of particular elements of the river s active zone in eight stretches of the biala the impact of the flood on valley floor infrastructure was confronted with the degree of river widening in unmanaged and channelized river reaches before the flood unmanaged cross sections were typified by finer bed material and greater lateral variability in depth averaged and near bed flow velocity than channelized cross sections the flood tended to equalize habitat conditions in both types of river cross sections obliterating differences in particular physical habitat parameters between channelized and unmanaged channel reaches river widening mostly reflected an increase in the area of channel bars whereas the widening of low flow channels was less pronounced a comparison of channel planform from 2009 and 2012 indicated that intense channel incision typical of downstream sections limited river widening by the flood active channel width increased by half in the unmanaged cross sections and by one third in the channelized cross sections however damage to the valley floor infrastructure was practically limited to the channelized river reaches with reinforced channel banks this indicates incompetent management of riparian areas rather than the degree of river widening as a principal reason for the economic losses during the flood

the potsdam beekmantown group boundary nepean formation type section ottawa ontario a cryptic sequence boundary not a conformable transition there are two unreconciled interpretations for the age and character of the boundary separating the cambrian ordovician potsdam and beekmantown groups that underlie the ottawa embayment in eastern ontario these stratal groups consist of interior facies of the central laurentian platform as exposed in the type section of the nepean formation upper potsdam group located in the city of ottawa the boundary was previously interpreted to be conformable and of early ordovician age this intepretation was of enormous impact on subsequent regional geology compilations that showed a diachronous boundary across the platform interior from recent subsurface analysis across eastern ontario the contact was interpreted to be disconformable a sequence boundary separating late cambrian and early ordovician strata this paper reexamines the type section lithologically the group boundary should be repositioned downsection by 1 5 m the contact now lies coincident with a disconformity that has a paleorelief of 10 cm the proposed revision is geologically significant previous collections of early ordovician conodonts from the type section used to define the age of what had been interpreted to be upper potsdam strata now fall entirely within the lower beekmantown group nepean potsdam strata exposed in the type section remain undated regional correlation of the disconformity across the laurentian platform suggests that nepean strata at the type section are likely of late cambrian age there now exists a regionally coherent separation of cambrian and ordovician sedimentation patterns in the ottawa embayment

spatiotemporal analysis of channel wall erosion in ephemeral torrents using tree roots an example from the patagonian andes this paper presents absolute ages for fl ash fl oods and related sediment entrainment in headwater catchments to construct a spatiotemporal framework of process dynamics and locations of major areas of channel wall erosion the most reliable method for dating erosion is through dendrogeomorphic studies of exposed tree roots based on the analysis of erosion signals in root ring records we documented a time series of channel wall erosion and successfully dated 21 erosive fl ash fl ood events since a d 1870 in an ephemeral gully in the patagonian andes the study was performed with roots from austrocedrus chilensis nothofagus dombeyi and pseudotsuga menziesii results demonstrate the potential of root analyses for the determination of major areas of sediment entrainment in addition we show that the position of damage within individual root rings allows inferences about the seasonal timing of fl ash fl ood effects and thus an assessment of possible meteorological triggers of erosive events short intense storms occurring primarily in austral fall and late winter in this case the approach presented adds signifi cantly to the documentation of sediment entrainment and facilitates identifi cation of areas of rapid erosion in small remote headwater catchments with ephemeral fl ash fl ood activity

slope channel coupling in steepland terrain a field based conceptual model from the tarndale gully and fan waipaoa catchment new zealand abstract connectivity between an actively eroding gully complex and upper waipaoa catchment via a steep 1 km long alluvial fan is assessed using digital elevation models dems of the tarndale fan derived from 10 high resolution gps surveys between 2004 and 2008 repeat dem analysis provides a means of assessing transfer of sediment supplied from the tarndale gully through the fan to the te weraroa stream and thus inferring connectivity between these landscape components from which a conceptual coupling model is derived analysis indicates the operation of two critical junction switches at the i gully fan and ii fan stream nexus which contribute to considerable complexity in patterns of erosion and deposition on the fan as it responds to sediment supply or starvation from the tarndale gully and evacuation to the te weraroa stream described in fuller and marden 2010 the fan does not respond as a coherent unit each of six fan feeder tributaries behaves independently according to sediment supplied from six discrete source areas within the gully complex this reflects sediment production within specific activity zones of tarndale gully mass movements triggered by single rainstorm events and or wet periods contingent upon sediment availability and intrinsic slope mechanics frequently deliver sediment to the upper fan tributaries this enhanced gully fan coupling during storms or wetter periods promotes rapid fan aggradation with each feeder tributary responding to its discrete source zone infilling may propagate down fan in response to upper fan incision once the gully fan switch deactivates transferring sediment as far as the te weraroa stream coupling the fan with the stream system floods generated in the te weraroa stream may also activate the junction switch at the fan stream nexus by trimming the lower fan prompting up fan incision via head cutting in response to changed local base level slope channel coupling in this environment is a function of a range of slope and channel processes responding to discrete storms and intrinsic gully dynamics the high rates of geomorphic activity in this environment mean the tarndale system provides a natural laboratory in which to assess key slope channel coupling processes beyond the plot or discrete event scale

holocene sea level changes along the strait of magellan and beagle channel southernmost south america abstract radiocarbon dated marine sediments from five coastal sites along the strait of magellan and beagle channel in southernmost chile permit construction of a curve of relative sea level fluctuations during the holocene morphologic and stratigraphic data point to coastal submergence during the early holocene as the sea rose to a maximum level at least 3 5 m higher than present about 5000 yr ago progressive emergence then followed during the late holocene data from widely separated localities define a smooth curve the form of which is explainable in terms of isostatic and hydroisostatic deformation of the crust resulting from changing ice and water loads apparently anomalous data from one site located more than 100 km behind the outer limit of the last glaciation may reflect isostatic response to deglaciation the sea level curve resembles one derived by clark and bloom 1979 in proceedings of the 1978 international symposium on coastal evolution in the quaternary sao paulo brasil pp 41 60 sao paulo using a spherical earth model both in amplitude and in the timing of the maximum submergence

dendrogeomorphic approaches for identifying the probable occurrence of debris flows and related torrential processes in steep headwater catchments the hrubý jesenik mountains czech republic abstract culminating parts of mid mountain ranges in central europe are interwoven by a network of high gradient streams these parts together with the surrounding slopes form a coupling system in which hazardous geomorphic processes such as landslides debris flows or flash floods can occur in the case of the hrub jesenik mountains eastern sudetes czech republic we present an evaluation of the debris flows and related torrential processes in the high gradient streams of the selected catchment based on dendrogeomorphic methods in addition to the classical dendrogeomorphic approaches we refined the procedure of identifying certain and probable events using new weighted indexes for event reconstruction additionally because of the steep narrow channels without a characteristic accumulation cone a new spatial approach is defined based on the spacing of disturbed trees for each event random distribution or clustering and location of disturbed trees in an individual section of the valley floor using kernel density analysis for each event and calculating the particular grids in arcgis software we are able to describe the spatial reach and probable nature of an event debris flow or hyperconcentrated flow dendrogeomorphic analysis of 397 sampled trees predominantly coniferous trees revealed 24 torrential events 15 certain nine probable since 1928 with peaks in 1991 1997 and 2010 according to index values in addition the spatial distribution of disturbed trees grouped in clusters in these years indicates debris flow events in the upper parts of the catchment it seems that new dendrogeomorphic approaches should be valuable in remote steep headwater catchments where several types of processes affect the valley floors

impact of coarse sediment supply from hillslopes to the channel in runoff dominated dryland fluvial systems sediment supply from hillslopes to channels is an important control on basin functioning and evolution however current theoretical frameworks do not adequately consider processes of runoff driven hillslope sediment supply which affect river channels spatially and temporally mountainous dryland basins exhibit an important manifestation of these processes because their debris mantled hillslopes produce coarse sediment and because rainfall is delivered as infrequent high intensity short duration rainstorms this paper combines field measurements and modeling to explore runoff driven coarse sediment supply from hillslopes to the channel and assesses a range of plausible storms on the longitudinal patterns of sediment load and its caliber over a dryland basin reach our results show that modeled sediment load and its grain size distribution are determined by the nonlinear interaction between rainfall characteristics and hillslope attributes resulting in longitudinal fluctuations in sediment supply the relative magnitude and location of which varies between storms results suggest that long hillslopes are most sensitive to rainfall and they exhibit large variations in supplied sediment load and grain size for different runoff characteristics short and steep hillslopes are less sensitive to rainfall variations as gradient effects dominate over the role of length in modulating runoff accumulation furthermore the signal of the median fraction d50 of modeled sediment supplied by the hillslope is preserved in the coarse fraction of the measured in channel grain sizes d90 finally we propose a simple index which provides new insights into the effectiveness of different rainstorms in terms of the impact of hillslope sediment supply on the channel

hillslope deposits in gravel bed rivers and their effects on the evolution of alluvial channel forms a case study from the sudetes and carpathian mountains this paper describes initiation and development of specific alluvial channel forms connected with the supply of coarse grained hillslope sediment the study was carried out in gravel bed rivers located in mid mountain areas the sudetes and the carpathian mountains in central europe in the river channels studied where input of hillslope material is abundant patterns of sedimentation and erosion are determined by hillslope processes two types of primary sediment source in mountain temperate rivers with flat valley floors were identified mass movements in particular landslides and supply of angular coarse grained slope material to streams from cut bank sections the introduced coarsest hillslope sediment is only entrained during floods which destabilize the river systems downstream of the supply points at these river channel sections development of new and transformation of existing alluvial channel forms is observed sediment accretion and progradation of bars downstream of the hillslope sediment delivery zones hsd zones is connected with activity of these zones frequency of hillslope sediment supply size of coarse grained angular deposits introduced into the river channels and frequency of flood events the largest depositional forms such as gravel rich debris longitudinal bars lateral bars with a rock block core and lateral bars downstream of an hsd zone comprise coarse usually gravel sized sediment the main feature of their initiation and progradation is deposition of large rock blocks within or at a short distance downstream of the supply points lateral sediment accretion of the bars leads to river channel constriction during subsequent floods and development of other alluvial channel forms such as transverse gravel rich debris ribs diffuse gravel rich debris sheets side debris bars and small sandy rich gravel separation bars these forms create depositional complexes which are observed in the river channel within the zone of the hillslope sediment supply and for a few hundred meters downstream

influence of sediment supply on mountain streams bedload transport abstract sediment transport and storage in mountain stream channels are closely dependent on hillslope activities and bank erosion this paper analyses bedload measured in 13 mountain streams 989 values with slope higher than 5 in an attempt to investigate how much the sediment supply condition impacts bedload transport rates first the sediment supply condition of each stream was evaluated qualitatively using information available in the original studies in the second step the data set was analysed by comparing bedload transport rates considering a shields stress ratio and by comparing transport rate efficiency with consideration of a dimensionless stream power the two analyses indicate higher sediment transport rates for the streams identified as connected to an active source the consequences for bedload transport prediction are discussed with a nonthreshold bedload equation even though predicting the exact sediment supply condition and the associated transport rate is not yet possible this study suggests that defining an envelope delimiting minimum and maximum transport for a given river reach should be possible

downstream coarsening in headwater channels 1 field data from four mountain drainage basins in western washington document systematic downstream coarsening of median bed surface grain size d50 and a subsequent shift to downstream fining at a drainage area of about 10 km2 analyses of network wide patterns of unit stream power derived from both channel surveys and digital elevation models reveal maximum unit stream power that in all four study areas roughly corresponds with both the grain size maxima and an inflection in the drainage area slope relation thought to represent the transition from debris flow dominated channels to fluvially dominated channels our results support the hypothesis that basin wide trends in d50 are hydraulically controlled by systematic variations in unit stream power in addition to lag deposits forced by mass wasting processes the similar relations found in our four study areas suggest that the tendency for downstream coarsening may be ubiquitous in headwater reaches of mountain drainage basins where debris flow processes set the channel gradient

coupling between hillslopes and channels in upland fluvial systems implications for landscape sensitivity illustrated from the howgill fells northwest england abstract the sensitivity of upland fluvial systems depends on the magnitude and frequency of sediment and flood producing events modified by the internal coupling characteristics of the system this paper assesses the role of hillslope channel coupling for the sensitivity of upland geomorphic systems using evidence from a 30 year monitoring programme of geomorphic change in the carlingill valley howgill fells northwest england in the hillslope zone there is little sediment supply to the stream system locally slope failures occur in response to extreme events six such events in 30 years within the ca 6 km 2 carlingill valley in the footslope coupling zone basally induced gullies are major sediment sources to the stream sediment production events occur ca 30 times per year feeding sediment to basal debris cones stream floods which can entrain these sediments occur once every ca 2 5 years stream channel morphology is adjusted to this regime downstream of gullies channels are wide and braided elsewhere they are narrow and single thread as the gullies develop however this coupling weakens and the eroding slopes eventually stabilise by revegetation over the 30 year monitoring period there has been a progressive trend towards gully stabilisation and an associated reduction in channel instability massive destabilisation may occur in response to rare extreme flood events such an event return period 100 years occurred in neighbouring langdale and bowderdale valleys in june 1982 that event destabilised the system causing slope failures fan deposition and in some places a switch in channel style to wide braided channels since 1982 there has been a progressive recovery by slope stabilisation and single thread sinuous channels have become reestablished a different style of extreme event occurred in carlingill in october 1998 in response to the wettest week in the 30 year period a slope failure fed debris flows 400 m downslope almost coupling with the channel system future climatic change could render the system prone to destabilisation through either extreme flood events or through major slope failures

do the coarsest bed fractions and stream power record contemporary trends in steep headwater channels abstract three stream channels that were devoid of evidence of past debris flows and one headwater channel that contained debris flow deposits in the flysch western carpathians czech republic were selected to test relationships between in channel processes bed sediments and unit stream power calculated for bankfull and q 20 flows contemporary depositional or erosional trends in the examined headwaters were linked with bed sediments that were represented by the coarsest cobble and boulder fraction with a mean calculated from the five largest particles the downstream trends of the unit stream power were derived for a bankfull discharge and a well documented 20 year flood event in addition the flow competences during the discharges were calculated using indirect bedload transport measurements downstream fining of the cobble and boulder fraction was observed in all of the studied headwaters and unique downstream variations of the unit stream power were calculated for the longitudinal profiles the single thread streams that were devoid of evidence of debris flow events exhibited direct relations between the coarsest sediment size and the unit stream power especially as calculated for the 20 year flood event and for erosional depositional trends of the channel the downstream coarsening of the bed material that was accompanied by an increase in the unit stream power was usually observed in the case of deeply incised 0 5 m above the assumed bankfull depth channel reaches the calculated competence of the 20 year flow was up to twofold higher than that required to entrain the largest bed particle diameters in those channel reaches and even the bankfull flow was potentially capable of transporting the coarsest bed particles in certain of the reaches on the other hand some depositional channel reaches evidently led to the disconnectivity of transport of the coarsest bed material even in the case of the 20 year flood event the longitudinal profile of the channel that had evidence of past debris flows did not clearly show a direct relationship between boulder size and calculated unit stream power and contemporary channel trends this finding reflected the presence of significantly coarser bed material which points to a higher stability of the debris flow influenced channel during ordinary floods when compared to fluvially dominated headwaters that are devoid of debris flows

sediment transfer processes in two alpine catchments of contrasting morphological settings summary coarse sediment transport processes in steep headwater streams may vary between bedload and debris flows events depending on basin geomorphology and sediment supply this paper compares two small catchments drainage area 4 5 km 2 located in the eastern italian alps where the dominant sediment transport processes differ substantially i e debris flows in the moscardo torrent and bedload events in the rio cordon the two basins were selected because they provided the unique opportunity to analyze long term data of debris flow and bedload volumes respectively the two basins are compared in terms of peak discharge event duration and magnitude frequency characteristics of transported sediment volumes additional bedload data from two more alpine experimental basins are also considered the results show that for comparable recurrence intervals debris flow volumes are 2 3 orders of magnitude larger than bedload volumes this contrasting sediment transfer activity can be attributed to different basin and channel morphologies which are analyzed in terms of sediment supply conditions longitudinal profiles and slope area curves

the influence of landsliding on sediment supply and channel change in a steep mountain catchment abstract rates of sediment supply by landsliding to an alluvial channel in a small catchment in central switzerland were estimated over an 11 month study period fluvial sediment transport in the channel is independently monitored at the upstream and downstream ends of the study reach yielding a unique opportunity to quantitatively compare the volume of sediment supplied to the channel with the volume in fluvial transport landslide derived sediment discharge to the channel was greatest during the winter and spring months while most of the fluvial sediment transport occurred during short intense summer storms approximately 98 m 3 of sediment was delivered directly to the study reach by landsliding 80 m 3 was transported into the reach from upstream and 70 m 3 was transported out of the reach thus there was a net accumulation of 100 m 3 of sediment during the 11 month study decadal scale channel aggradation was independently assessed by comparing channel longitudinal profiles in 1993 and 2004 during this 11 year period a total of 1500 m 3 of sediment has accumulated in the study reach aggradation has occurred largely in two broad zones that correspond with both the locations of major landslide complexes and reaches of high channel slope indicating that hillslope sediment input left an imprint on the morphology of the channel bed that appears to be stable over at least decadal time scales

gravel drift and wind effects on the macrotidal san sebastian bay tierra del fuego argentina abstract in northeastern tierra del fuego the holocene mean sea level msl fluctuation reworked much pre wisconsin glacial drift into sand gravel beaches and spits and sand mud tidal flats for the last 7000 years sea level has been falling a southwards wave induced longshore transport of sand and gravel has constructed the 17 km long el paramo spit which partly encloses the wide san sebastian bay semidiurnal tides with a range of up to 10 m enter the bay from the south causing a dominance of flood currents and wave action in the southern part of the bay ebb currents predominate in the north this segregation of flows conditioned sedimentation and is thus responsible for the south north transition of welded gravel ridges sand flats mixed flats and mud flats on the southern coast of the bay wave action constructed discrete sets of gravel ridges which diverted the san mar in river inlet northwards over the tidal flats north of this inlet where gravels are not yet available storms produce chenier systems discrete deposits of shells and sands the lengths of which progressively shortened as the inlet of the bay became narrower and the bay infilled because storms affect both the bay and the atlantic beach washover fans cut these cheniers and the gravel ridges on the narrower part of the spit the fossil gravel ridges in the northern and southern parts of san sebastian bay are not the only supratidal environments fossil and active marshes evolve conditioned by the strong and persistent wind action seasonal ponds are produced by intense deflation salicornia marsh occurs as circular structures 2 3 m diameter clustered over the supratidal flats on the intertidal mud flats wind causes deflation during neap tides and silting during spring tides north of the bay the eastward migration of straight tidal channels or rills is conditioned by winds the effects of strong and persistent winds from the pacific influence not only the tidal flats but also the gravel spit if ocean waves induce a southward drift of gravels within the bay the wind induced gravel drift is to the north during winter there are no aeolian effects over the iced tidal flats

bedload transport measurements at the erlenbach stream with geophones and automated basket samplers in the erlenbach stream a pre alpine steep channel in switzerland sediment transport has been monitored for more than 25 years near the confluence with the main valley river stream flow is monitored and sediment is collected in a retention basin with a capacity of about 2000 m3 the basin is surveyed at regular intervals and after large flood events in addition sediment transport has been continuously monitored with piezoelectric bedload impact and geophone sensors since 1986 in 2008 2009 the measuring system in the erlenbach stream was enhanced by installing an automatic system to obtain bedload samples movable metal baskets are mounted on a rail at the downstream wall of the large check dam above the retention basin and they can be moved automatically into the flow to take bedload transport samples the wire mesh of the baskets has a spacing of 10 mm to sample all sediment particles coarser than this size which is about the limiting grain size detected by the geophones the upgraded measuring system permits to obtain bedload samples over short sampling periods and to measure the grain size distribution of the transported material and its variation over time and with discharge the analysis of calibration relationships for the geophone measuring system confirms findings from very similar measurements which were performed until 1999 with piezoelectric bedload impact sensors there is a linear relationship between impulse counts and bedload mass passing over the sensors findings from flume experiments are used to discuss the most important factors which affect the calibration of the geophone signal the bedload transport rates as measured by the moving baskets are among the highest measured in natural streams with values of the order of several kilograms per meter per second copyright 2012 john wiley sons ltd

erosion and channel change as factors of landslides and valley formation in champlain sea clays the chacoura river quebec canada the champlain sea clays of eastern canada are incised by numerous rivers their slopes have been modified by landslides on the chacoura river near trois rivieres quebec several large landslide scars more or less recent are visible the role of erosion channel incision lateral channel migration and erosion of slopes due to agricultural drainage as a trigger of these landslides is important the aim of this study is to understand how erosion and landslides are related to valley development from a detailed analysis of aerial photographs and dems a map of the phenomena has been drawn by identifying various elements such as landslides limits of the slope position of the channel and the area covered by forest it is shown that channel change and erosion are strongly linked to landslides by the fact that they change the bank morphology in an unstable way a slide in itself is a natural way for the slope to achieve stability but when it occurs in a stream it creates a disturbance to the stream flow enhancing local erosion which may change the river path and generate more erosion downstream or upstream resulting in more slides cross valley sections and a longitudinal profile show that landslides are a major factor of valley formation it appears that the upper part of the chacoura river valley is still unaffected by landslides and has v shaped sections the lower part has been subject to intense erosion and many landslide scars can be seen this shows that the valley morphology is transient and that future activity is more likely to occur in the upper part of the river therefore the identification of areas prone to erosion will help determine the possible location of future large landslides just like the ones that occurred in the lower part

catena linking of landscape geochemical processes and reconstruction of pedosedimentogenesis a case study of defensive constructions of the mid 17th century south russia abstract the catena concept along with previously proposed meanings of this term has recently acquired a soil evolutionary content the prospects of wider special and chronological study of dated pedotopocatenas include the possibility of a more detailed analysis of the mutual dependence of soil geomorphological relationships through distinguishing relatively homogeneous climatic stages of pedogenesis and denudation with this purpose the present study comprised earthen defensive constructions which within the rampart ditch system combine erosive trans accumulative catenas and accumulators of pedolithosediments the goal was to develop a system of the most information rich pedogenetic indicators to reconstruct the dynamics of erosion accumulative processes on the basis of dated earthen defensive constructions of a historical period using the example of a frontier rampart within a ditch from the mid 17th century soil samples were collected within the limits of the erosion and trans accumulative catenas as well as in the closing alignment of the ditch over the vertical profile in eight strata of pedosediments of up to 1 m high the granulometric composition concentration of macroelements and trace elements 25 metals and oxides in soils and in particles with sizes 0 01 mm in size the content of organic carbon and its qualitative composition the sum of the elements accumulated in the soil p ca k mg mn cu as well as the geochemical ratios which reflect the processes of leaching can serve as palaeogeographic tracers of the climatic variability at the level of intra secular changes under forest steppe conditions the history of the formation of pedosediments over 3 5 centuries in the forest steppe zone of eastern europe comprises two wet periods 1890 1935 1976 2013 when the average annual rates of pedosedimentogenesis were similar 2 80 2 85 mm yr 1 and two periods of geomorphological lull and a xeromorphic climatic condition span 1821 1890 and 1666 1741 these periods correspond to diminution of the average rate of accumulation of sediments down to 2 47 mm yr 1 the results of the present study suggest the need for purposeful research and wide inclusion of dated sites of the anthropogenic relief formation with flow geochemical series over the topographic gradient into studies of soil geomorphologic interrelations and calibration of mathematic models of natural processes using on site data

high resolution quantitative reconstruction of erosion rates based on anatomical changes in exposed roots at draix alpes de haute provence critical review of existing approaches and independent quality control of results extensive areas of french alps are underlain by jurassic black marls wherever these terres noires crop out they become subject to intense erosion causing major sedimentation in regional reservoirs and river systems in the badlands near draix alpes de haute provence france measured sediment rates were obtained at the plot scale by surface elevation change based methods and at the catchment scale by monitoring sedimentation in dams in this study we use a dendrogeomorphic approach based on anatomical changes in exposed roots of pinus sylvestris l to accurately quantify continuous denudation rates a total of 123 cross sections 75 from buried and 48 from exposed roots of 23 trees were sampled in the moulin basin the size and position of roots at the time of exposure was determined via anatomical variations in the annual growth rings of roots in cross sections of buried roots a sharp reduction of earlywood tracheid lumen area a growth signature which has traditionally been used to determine the moment of root denudation was observed as soon as erosion reduced soil cover to 3 cm as a consequence estimates of eroded soil thickness had to be adjusted to take account of this bias bias adjusted averaged medium term erosion rates derived from exposed roots vary between 6 and 7 mm y 1 at moulin basin depending on the importance accorded to the uplift of roots after exposure values are significantly correlated to slope angle and match with erosion rates derived from monitored iron stakes 5 7 mm y 1 or measurements of sediment yield in retention dams 4 7 mm y 1 at the outlet of the moulin basin besides demonstrating that the interpretation of anatomical signatures in tree roots to erosion have to be revised this paper also shows that dendrogeomorphic analyses of roots are indeed a powerful tool for the quantification of minimal rates of soil erosion in environments where measurements of past activity are not available

coupling between landslides and eroding stream channels reconstructed from spruce tree rings examples from the carpathians and sudetes central europe the analysis of the positive feedback between landslides and erosion requires determination of the precise temporal and spatial relations between events of colluvium delivery and fluvial erosion in our study we use decennial datasets on the occurrence of landsliding and erosion achieved through dendrochronological methods four sites covering areas of landslide slopes and adjacent valley floors with stream channels were studied landsliding on slopes was dated from the tree ring eccentricity developed in stems tilted due to bedrock instability erosion in channels was dated using the wood anatomy of roots exposed by erosion of the soil cover analysis of the temporal relations between dated landsliding erosion and precipitation record has revealed that two types of repeating sequences can be observed 1 rainfall landsliding erosion 2 rainfall erosion landsliding these sequences are an indication of the occurrence of slope channel positive feedback in the sites studied in the first type landsliding triggered by rainfall delivers colluvia into the valley floor and causes its narrowing which in turn causes increased erosion in the second type erosion triggered by rainfall disturbs the slope equilibrium and causes landsliding landsliding and erosion once triggered by precipitation can occur alternately in years with average precipitation and reinforce one another bidirectional coupling between landsliding and channel erosion was shown notably through the effects of channel shifting and forced sinuosity and by increased erosion of the slopes opposite the active landslides observations also suggest that the repetition of sequences described over longer periods of time can lead to a general widening of the valley floor at the expense of slopes and to a gradual change of the valley cross profile from narrow v shaped into a wide flat bottomed thus landsliding erosion coupling positive feedback was recognized as an important factor shaping hillslope valley topography of the mid mountain areas studied copyright 2014 john wiley sons ltd

application of ash fraxinus excelsior l roots to determine erosion rates in mountain torrents abstract due to the effect of global change the potential risk of natural hazards occurring in alpine areas is expected to increase to an even higher risk level than has been recorded during the last century these global changes potentially also have distinct influences on fluvial processes in torrents causing erosion on slopes and riverbanks in forested areas dating the time of root exposure along riverbanks combined with common dendrogeomorphic analysis applied to tree trunks helps to reconstruct the erosion dynamics leading to a potential destabilization of adjoining trees the advantage of using exposed roots compared to common erosion measurement techniques is that the erosion rates can be quantified with annual resolution the first year of exposure can be determined precisely by the characterization of the wood anatomical changes in the microscopic structure of the root this study is the first to concentrate on the analysis of wood anatomical features of exposed roots of angiosperm trees aiming to reconstruct erosional processes two mountain torrents were selected as study sites based on a preliminary evaluation of various swiss alpine areas sites of special interest concerning erosive processes were classified and examined in five different geomorphological groups representing different processes the analysis comprised the examination of the exposed tree roots in each group the project shows the potential of roots in general and in particular roots of deciduous angiosperm trees for geomorphological research especially concerning erosion studies

frequency predisposition and triggers of floods in flysch carpathians regional study using dendrogeomorphic methods abstract dangerous overland flood events in the foothills of the flysch carpathians often result from a cumulative effect of floods in high gradient channels detailed understanding of the origin of floods in these catchments is only possible if the occurrence of these floods in the past has thoroughly been studied yet no gauging stations can be found in the local catchments the reconstruction of floods in ungauged catchments has so far been performed using dendrogeomorphic methods stems or branches floating in the floodwater can affect stems or roots of living trees and injure them trees are able to record these signals in their tree ring series within the flysch carpathians the floods have been reconstructed based on the analysis of 446 cross sections from scarred tree roots and 192 increment cores from the stems of affected trees in the studied area of 10 catchments surrounding the highest peak of the moravskoslezske beskydy mts the lysa hora mt the dating comprised 64 floods in different catchments in 28 flood years for the maximal period of 1883 2012 most catchments nine out of ten were affected by floods in the year 1997 above average frequency of floods has also been found for the last two decades namely thanks to numerous samples taken from young tree roots that revealed more flood impacts by contrast although tree ring series enabled the reconstruction of a longer time series they only recorded the major floods the most significant factor affecting the frequency of floods is the orientation of catchments toward the prevailing wind direction positive influence of catchment gradient on flood frequency and higher occurrence of floods in the period of intensive slope deforestation show that the floods of the 1950s to 1970s could have a character of flash floods this assumption is also supported by the character of probable triggering precipitation high magnitude short duration precipitation of this period generally the most frequent probable triggering factor is however an above average seven day precipitation amount which indicates along with the positive relation between the catchment extent and flood frequency that a majority of floods hardly ever occur as an immediate response to one day precipitation extremes fast spring melting of thick snow cover plays an insignificant role in floods in the studied medium high mountains

spatio temporal patterns of recurrent slope instabilities affecting undercut slopes in flysch a dendrogeomorphic approach using broad leaved trees abstract the undercut slope of the skalicka stra nice vrchy hill situated in the piedmont of the carpathian mountains czech republic is a regional landslide hotspot notorious for its repeated recent and historical sliding reactivations we performed tree ring analysis of a large number n 274 of broad leaved trees to reconstruct the spatio temporal patterns of landslide reactivation for a period spanning more than one hundred years 1884 2011 although tree rings of broad leaved trees are less reliable archives of landslide activity than those of conifers the application of a methodology based on the weighting of disturbance signals within eccentricity series generated a usable dataset of sliding activity affecting anisotropic flysch bedrock although some known landslide years could not be found or were expressed by only weak signals in the reconstructed dataset the majority of landslide events reconstructed from the tree ring series coincide with hydrometeorological data revealing a correlation with heavy summer rainfalls lasting from two to ten days the spatial distribution of landslide recurrence derived from the tree ring records together with electrical resistivity tomography and a kinematic analysis of slope failures suggest a close link between the concentration of landslide activity and the presence of faulted or fractured flysch bedrock

channel reach morphology controls of headwater streams based in flysch geologic structures an example from the outer western carpathians czech republic a detailed measurement of 93 channel reaches that were classified with an adjusted montgomery buffington 1997 reach scale system provided comprehensive information of approximately 9 at a reach parameters the channel gradient the bankfull width the bankfull depth d90 the percentage of resistant rocks in the bed sediment the number of pieces of large woody debris valley confinement direct sediment inputs and the presence of fluvial accumulations in the stream channel in addition the quantified intensity of sediment transport i e ratio between sediment supply and transport capacity in longitudinal stream profiles during flood events has been estimated by the one dimensional bedload transport model tomsed which was validated in two local streams the principal component analysis of the at a reach parameters did not reveal significant groups of channel reach morphologies thus the selected parameters that exclude sediment transport dynamics within stream longitudinal profile cannot reliably distinguish or predict individual channel reach morphologies nevertheless the channel gradient represented the most significant single explanatory variable for stepped bed morphologies the addition of bedload transport parameters demonstrated that limited sediment supply streams and streams with limited transport capacities featured different successions of the channel reach morphologies in terms of the channel gradient and subsequently the fluvial continuity the bedrock cascades and step pools were significant for the first case whereas cascade and step rapid morphology often occurred in higher sediment supply conditions

landslide induced river channel avulsions in mountain catchments of southwest new zealand pulsed or chronic supply of landslide debris to valley floors has historically caused substantial aggradation and channel instability in several alpine catchments of sw new zealand in this regional investigation of landslide impacts on river morphology three types of landslide induced channel avulsion are discerned i upstream backwater avulsions ii contact avulsions and iii downstream loading avulsions the basis for this qualitative geomorphic process response framework is the principal direction of fluvial response with respect to its position relative to the causative landslide emplacement site downstream avulsions have the highest damage potential to land use and infrastructure on unconfined mountain fringe alluvial fans in the wake of such events catastrophic aggradation may obliterate up to several km2 of mature floodplain forests by burial under several metres within a few decades estimates of mean aggradation rates are high 220 mm year 1 and exceed long term 103 year trends of fluvial degradation by an order of magnitude future potential avulsion routeways may be detected by geomorphic mapping of abandoned channels which are preferentially reactivated in the wake of landslide induced sediment waves