bed waves at the basin scale implications for river management and restoration an extensive literature about fluvial sediment waves slugs or pulses has emerged in the past 20 years the concept has been useful in many respects but has been applied to diverse phenomena using a variety of definitions moreover inferred linkages between channel bed changes and sediment loads are often not justifiable this paper reviews concepts of large fluvial sediment waves at scales extending to several tens of kilometres it points out constraints on the inferences that can be made about sediment loads based on changes in channel bed elevation at this scale where channel sediment interacts with storage in floodplain and terrace deposits the type area of g k gilbert s initial sediment wave concept is re examined to show that neither wave translation nor dispersion occurred in the simple manner commonly assumed channel aggradation and return to graded conditions provide an alternative theory explaining gilbert s observed bed elevation changes recognizing the evidence and implications of the former passage of a large scale bed wave is essential to the accurate diagnosis of catchment conditions and the adoption of appropriate river restoration goals or methods sediment loads water quality channel morphologic stability and aquatic ecosystems often reflect changes in sediment storage long after the channel bed has returned to grade copyright 2006 john wiley sons ltd

active channel width as a proxy of sediment supply from mining sites in new caledonia although the channel morphology of upland fluvial systems is known to be strongly controlled by sediment supply from hillslopes it is still difficult to isolate this effect from the other controlling factors of channel forms such as the sediment transport capacity depending notably on the size of the catchment and local conditions e g confinement riparian vegetation valley floor slope the rivers in new caledonia offer an interesting field laboratory to isolate the morphological effect of contrasted sediment supply conditions some of these rivers are known to be highly impacted by the coarse sediment waves induced by the mining of nickel deposits that started in the early 1870s which was particularly intensive between the 1940s and 1970s the propagation of the sediment pulses from the mining sites can be traced by the presence of wide and aggraded active channels along the stream network of nickel rich peridotite massifs a first set of 63 undisturbed catchments in peridotite massifs distributed across the grande terre was used to fit a classic scaling law between active channel width and drainage area a second set of 86 impacted sites where the presence of sediment waves was clearly attested by recent aerial imagery showed systematically wider active channels with a width ratio around 5 established from the intercept ratio of width area power laws more importantly this second set of disturbed sites confirmed that the residual of active channel widths computed from the scaling law of undisturbed sites is statistically positively related to the catchment scale relative area of major mining sediment sources it is therefore confirmed that the characterization of sediment supply conditions is crucial for the understanding of spatial patterns of active channel width and this should be more thoroughly considered in morphological studies of rivers draining environments with contrasted geomorphic activities on hillslopes

downstream fining in a rapidly aggrading gravel bed river downstream changes in particle size that occur in the waipaoa river a 104 km long gravel bed river in which rapid aggradation in the historic post 1800 period was triggered by the conversion of native forest to pasture are summarized in this paper the textural data presented are unique for a field situation not only because of the spatial resolution and extent of the sampling program but also because they provide information about the pattern of fining at different points in time they are supported by equally comprehensive topographic survey data from which local rates of aggradation can be derived despite variability induced by lateral sediment inputs there is an essentially continuous pattern of fining along the entire length of the river fining occurs in both the fine and coarse size fractions of the bed material the highest rates of fining occur in the larger percentiles of the subsurface bed material and in the surface bed material downstream fining in the waipaoa river appears to be a response to changes in flow hydraulics that are regulated by the concave configuration of the long profile the fining gradient developed rapidly in 45 years it does not appear to be influenced by the rate of aggradation nor the overall rate of sediment supply to the channel system because in the short term aggradation has a negligible impact on the inherited form of the long profile

channel response to an extreme flood and sediment pulse in a mixed bedrock and gravel bed river we exploit a natural experiment caused by an extreme flood 500 year recurrence interval and sediment pulse derived from more than 2500 concurrent landslides to explore the influence of valley scale geomorphic controls on sediment slug evolution and the impact of sediment pulse passage and slug deposition and dispersion on channel stability and channel form sediment slug movement is a crucial process that shapes gravel bed rivers and alluvial valleys and is an important mechanism of downstream bed material transport further increased bed material transport rates during slug deposition can trigger channel responses including increases in lateral mobility channel width and alluvial bar dominance pre and post flood lidar and aerial photographs bracketing the 2007 flood on the chehalis river in south western washington state usa document the channel response with high spatial and temporal definition the sediment slug behaved as a gilbert wave with both channel aggradation and sequestration of large volumes of material in floodplains of headwaters reaches and reaches where confined valleys enter into broad alluvial valleys differences between the valley form of two separate sub basins impacted by the pulse highlight the important role channel and channel floodplain connectivity play in governing downstream movement of sediment slug material finally channel response to the extreme flood and sediment pulse illustrate the connection between bed material transport and channel form specifically the channel widened lateral channel mobility increased and the proportion of the active channel covered by bars increased in all reaches in the study area the response scaled tightly with the relative amount of bed material sediment transport through individual reaches indicating that the amount of morphological change caused by the flood was conditioned by the simultaneous introduction of a sediment pulse to the channel network copyright 2015 john wiley sons ltd

response and recovery of a subalpine stream following a catastrophic flood the july 15 1982 lawn lake flood in rocky mountain national park colorado was caused by the failure of a 79 yr old earthen dam peak discharges of the flood far exceeded naturally occurring flows and it caused severe channel disturbance along most of roaring river and some parts of fall river this study documents the geomorphic response of a 5 km reach of fall river in the 5 yr following the flood in 1983 the first year after the lawn lake flood snowmelt flows were well above average these high flows together with very high sediment yields from roaring river resulted in significant geomorphic changes on reaches of fall river downstream during the 1983 snowmelt runoff 15 5 x 106 kg of bed load sediment was eroded from the upper part of the study area these loads were at least 1 000 times higher than before the lawn lake flood most of this sediment was then deposited in a highly sinuous reach of fall river in the lower part of the study area this reach had not been much affected by the lawn lake flood but sedimentation during the period of high flow in 1983 completely filled in the channel resulting in the formation of a continuous 2 3 km long depositional zone in 1984 sediment yield from roaring river declined dramatically and this trend continued for the next 3 yr by 1987 the bed load sediment yield in the upper reaches of fall river was only about 0 4 x 106 kg yr the decline in sediment loads resulted in progressive erosion and recovery of the original channel of fall river in the depositional zone reach recovery in the upstream part of the depositional zone was complete by 1985 recovery in the downstream part of the depositional zone took longer because of the continued supply of sediment and because the sediment was mobile less of the time as of 1987 about 80 of the material initially stored in the sedimentation zone had been eroded bed load sediment yields at a sampling site 1 km downstream of the terminus of the depositional zone ranged from 5 x 106 to 11 x 106 kg yr but showed no significant decline over the 5 yr study period the average rate of bed load transport through this reach was at least 100 times greater than before the lawn lake flood but few discernible channel changes resulted from the higher loads

an integrated approach for investigating geomorphic response to extreme events methodological framework and application to the october 2011 flood in the magra river catchment italy a high magnitude flash flood which took place on 25 october 2011 in the magra river catchment 1717 km2 central northern italy is used to illustrate some aspects of the geomorphic response to the flood an overall methodological framework is described for using interlinked observations and analyses of the geomorphic impacts of an extreme event the following methods and analyses were carried out i hydrological and hydraulic analysis of the event ii sediment delivery by event landslide mapping iii identification and estimation of wood recruitment deposition and budgeting iv interpretation of morphological processes by analysing fluvial deposits v remote sensing and geographic information system gis analysis of channel width changes in response to the high magnitude hydrological event a large number of landslides occurred consisting of earth flows soil slips and translational slides and a large quantity of wood was recruited in most part deriving from floodplain erosion caused by bank retreat and channel widening the most important impact of the flood event within the valley floor was an impressive widening of the overall channel bed and the reactivation of wide portions of the pre event floodplain along the investigated unconfined or partly confined streams total investigated length of 93 5 km the channel width after the flood was up to about 20 times the channel width before the event the study has shown that a synergic use of different methods and types of evidence provides fundamental information for characterizing and understanding the geomorphic effects of intense flood events the prediction of geomorphic response to a flood event is still challenging and many limitations exist however a robust geomorphological analysis can contribute to the identification of the most critical reaches copyright 2016 john wiley sons ltd

the elastic anisotrophy of shales shales constitute about 75 of the clastic fill sedimentary basins and have a decisive effect on fluid flow and seismic wave propagation because of their low permeability and anisotropic microstructure the elastic stiffnesses of a shale with partially oriented clay particles is expressed in terms of the coefficients w sub lmn in an expansion of the clay particle orientation distribution function in generalized legendre functions application is made to the determination of the anellipticity of shales for transverse isotrophy the anellipticity quantifies the deviation of the p wave slowness curve from an ellipse and is shown to depend on a single coefficient w sub 400 in the expansion of the clay particle orientation distribution function if w sub 400 is small the anellipticity may be neglected as is apparently the case for a near surface late tertiary shale studied by winterstein and paulson strongly aligned clay particles result in a positive value of w sub 400 and a positive anellipticity in agreement with the majority of the field measurements however less well ordered shales could have a significantly positive second moment w sub 200 but only a small positive or even negative value of w sub 400 for such shales the anellipticity would be small or negative despite amore preferred alignment of clay particles in the bedding plane numerical examples of clay particle orientation distribution functions leading to zero or negative anellipticity are given less

experiments on folding in spreading gliding nappes abstract a small scale model of spreading gliding nappe was used to study the development of folds which are controlled by the geometry of external boundaries throughout in the model the deformation combines pure shear and simple shear recumbent folds are produced above irregularities of the base the cylindricity of folds is directly dependant on the cylindricity of basal irregularities models with homogeneous rheological properties produce only recumbent folds whereas models of contrasting rheological properties produce recumbent folds and en echelon upright folds in the zones of lateral shear the experiments demonstrate that 1 a large scale recumbent folds in nappes can result from passive amplification processes in unsteady shear flow 2 b upright folds and coaxial refolding result from mechanical instability due to contrasting rheological properties between layers and develop during a unique progressive deformation these laws can be directly applied to a spreading gliding nappe but also on a larger scale to all nappes in which the shear component dominates the deformation

regional bankfull geometry relationships for southern california mountain streams and hydrologic applications abstract this study develops and intercompares regional relationships for bankfull channel width hydraulic depth and cross sectional area for southern california mountain streams based on several data sources surveyed streams us geological survey stream survey reports and existing literature although considerable uncertainty exists in estimating bankfull conditions the relationships developed from the varying data sources show significant agreement for small watersheds with drainage area ranging from 15 to 2000 km 2 the estimates of bankfull top width ranged from 7 2 to 44 5 m and hydraulic depth estimates ranged from 0 35 to 1 15 m the utility of the developed bankfull geometry regional curves is demonstrated for southern california catchments through a the computation of the bankfull discharge and b the estimation of the surface runoff response necessary to produce bankfull conditions in the streams at the outlet of these catchments for selected locations with instantaneous flow records the occurrence frequency of events exceeding bankfull flow was examined for the available 10 15 year span of observational records bankfull discharge estimates for all small watersheds in the region ranged from 1 3 to 74 m 3 s while the range at the selected gauged stream locations was from 2 6 to 16 4 m 3 s stream locations along the transverse mountains of southern california showed an average occurrence frequency of less than 1 year whereas along the peninsular mountains the average return period tended to be greater than 1 year the application of the regional curves to the estimation of the surface runoff response necessary to produce bankfull conditions at the channel outlets of small catchments may be used as an index for conditions of minor flooding with saturated soils this surface runoff response index ranges from 2 0 to 5 5 mm for a 3 hour rainfall duration for southern california watersheds greater than 15 km 2 in area differences between the values for the peninsular and transverse mountain ranges are linked to geological climatic and geomorphologic differences the developed regional geometry relationships are suitable for use in various hydrologic modeling applications including distributed modeling with high resolution pertinent to flash flood forecasting

causes of 20th century channel narrowing in mountain and piedmont rivers of southeastern france extensive channel narrowing in southeastern france provides an illustration of geomorphic response to land use changes the study region comprises a range of environments from large piedmont and intramountain gravel bed rivers to small mountain streams field measurements and analysis of historical data demonstrate two distinct periods of channel change from 1850 to 1950 channel narrowing is interpreted to be the result of a recovery process in response to widespread channel destabilization induced by major floods during the second half of the 19th century at the time the largely deforested basins were highly responsive to flooding whereas the recovery process was accelerated by floodplain and basin scale land use changes afforestation and torrential control works which in turn reduced sediment delivery and enabled vegetation development in channels from 1950 to 1970 channel narrowing accelerated in most of the studied rivers this recent phenomenon is considered as a human induced fluvial adjustment directly related to forest development on river margins and human abandonment of intensive floodplain land uses at the same time long profile degradation occurred as a result of long term bedload supply decrease in small mountain streams channel narrowing is mainly explained by channel incision which seems to progress from upstream where sediment sources are progressively stabilized by afforestation copyright 2002 john wiley sons ltd

a multiresolution index of valley bottom flatness for mapping depositional areas 1 valley bottoms function as hydrological buffers that significantly affect runoff behavior distinguishing valley bottoms from hillslopes is an important first step in identifying and characterizing sediment deposits for hydrologic and geomorphic purposes valley bottoms occur at a range of scales from a few meters to hundreds of kilometers in extent this paper describes an algorithm for using digital elevation models to identify valley bottoms based on their topographic signature as flat low lying areas the algorithm operates at a range of scales and combines the results at different scales into a single multiresolution index this index classifies degrees of valley bottom flatness which may be related to depth of deposit the index can also be used to identify groundwater constrictions and to delineate hydrologic and geomorphic units

changes in braided river morphology resulting from aggradation and degradation forty three experiments were completed in a large flume 1 8 x 18 3 m to examine the effects of sediment load sediment size and channel gradient on braided river morphology the laboratory results were supported by field research and analogs from the published literature subaerially exposed braid bars were formed by the dissection and further accretion of stalled linguoid dunes which are actively migrating bedforms bar forming processes and channel dynamics were the same in both sand and gravel bed channels however linguoid dunes stalled and were transformed into braid bars more frequently in gravel bed channels and therefore gravel bed channels were more intensely braided aggradation resulted in the development of more bars rather than in an increase in the size of preexisting braid bars the number of actively migrating linguoid dunes also increased with sediment load in the highly mobile sand bed channels conversely in degrading channels the number of braid bars decreased and average bar

gravel sediment routing from widespread low intensity landscape disturbance current river basin missouri during the last 160 years land use changes in the ozarks have had the potential to cause widespread low intensity delivery of excess amounts of gravel sized sediment to stream channels previous studies have indicated that this excess gravel bedload is moving in wave like forms through ozarks drainage basins the longitudinal areal distribution of gravel bars along 160 km of the current river missouri was evaluated to determine the relative effects of valley scale controls tributary basin characteristics and lagged sediment transport in creating areas of gravel accumulations the longitudinal distribution of gravel bar area shows a broad scale wave like form with increases in gravel bar area weakly associated with tributary junctions secondary peaks of gravel area with 1 8 4 1 km spacing disturbance reaches are superimposed on the broad form variations in valley width explain some but not all of the short spacing variation in gravel bar area among variables describing tributary drainage basin morphometry present day land use and geologic characteristics only drainage area and road density relate even weakly to gravel bar areal inventories a simple channel network based sediment routing model shows that many of the features of the observed longitudinal gravel distribution can be replicated by uniform transport of sediment from widespread disturbances through a channel network these results indicate that lagged sediment transport may have a dominant effect on the synoptic spatial distribution of gravel in ozarks streams present day land uses are only weakly associated with present day gravel inventories and valley scale characteristics have secondary controls on gravel accumulations in disturbance reaches copyright 1999 john wiley sons ltd

downstream variation in bankfull width of wadeable streams across the conterminous united states abstract bankfull channel width is a fundamental measure of stream size and a key parameter of interest for many applications in hydrology fluvial geomorphology and stream ecology we developed downstream hydraulic geometry relationships for bankfull channel width w as a function of drainage area a w a dhg wa for nine aggregate ecoregions comprising the conterminous united states using 1588 sites from the u s environmental protection agency s national wadeable streams assessment wsa including 1152 sites from a randomized probability survey sample sampled stream reaches ranged from 1 to 75 m in bankfull width and 1 to 10 000 km 2 in drainage area the dhg wa exponent which expresses the rate at which bankfull stream width scales with drainage area fell into three distinct clusters ranging from 0 22 to 0 38 width increases more rapidly with basin area in the humid eastern highlands encompassing the northern and southern appalachians and the ozark mountains and the upper midwest great lakes region than for the west both mountainous and xeric areas the southeastern coastal plain and the northern plains the dakotas and montana stream width increases least rapidly with basin area in the temperate plains cornbelt and southern plains great prairies in the heartland the coefficient of determination r 2 was least in the noncoastal plains 0 36 0 41 and greatest in the appalachians and upper midwest 0 68 0 77 dhg wa equations differed between streams with dominantly fine bed material silt sand and those with dominantly coarse bed material gravel cobble boulder in six of the nine analysis regions where dhg wa equations varied by sediment size fine bedded streams were consistently narrower than coarse bedded streams within the western mountains ecoregion where there were sufficient sites to develop dhg wa relationships at a finer spatial scale and ranged from 1 23 to 3 79 and 0 23 to 0 40 respectively with r 2 0 50 for 10 of 13 subregions range 0 36 to 0 92 enhanced dhg equations incorporating additional data for three landscape variables that can be derived from gis mean annual precipitation elevation and mean reach slope significantly improved equation fit and predictive value in several regions most notably the western mountains and the temperate plains channel width was also related to human disturbance we examined the influence of human disturbance on channel width using several indices of local and basinwide disturbance contrary to our expectations the data suggest that the dominant response of channel width to human disturbance in the united states is a reduction in bankfull width in streams with greater disturbance particularly in the western mountains where population density road density agricultural land use and local riparian disturbance were all negatively related to channel width and in the appalachians and new england where urban and agricultural land cover and riparian disturbance were all negatively associated with channel width

a centennial tribute to g k gilbert s hydraulic mining debris in the sierra nevada abstract g k gilbert s 1917 classic monograph hydraulic mining debris in the sierra nevada is described and put into the context of modern geomorphic knowledge the emphasis here is on large scale applied fluvial geomorphology but other key elements e g coastal geomorphology are also briefly covered a brief synopsis outlines key elements of the monograph followed by discussions of highly influential aspects including the integrated watershed perspective the extreme example of anthropogenic sedimentation computation of a quantitative semidistributed sediment budget and advent of sediment wave theory although gilbert did not address concepts of equilibrium and grade in much detail the rivers of the northwestern sierra nevada were highly disrupted and thrown into a condition of nonequilibrium therefore concepts of equilibrium and grade for which gilbert s early work is often cited are discussed gilbert s work is put into the context of complex nonlinear dynamics in geomorphic systems and how these concepts can be used to interpret the nonequilibrium systems described by gilbert broad basin scale studies were common in the period but few were as quantitative and empirically rigorous or employed such a range of methodologies as pp105 none demonstrated such an extreme case of anthropogeomorphic change

channel response to sediment wave propagation and movement redwood creek california usa redwood creek north coastal californa usa has experienced dramatic changes in channel confguation since the 1950s a series of large floods in 1955 1964 1972 and 1975 combined with the advent of widespread commercial timber harvest and road building resulted in extensive erosion in the basin and contributed high sediment loads to redwood creek since 1975 no peak flows have exceeded a 5 year recurrence interval twenty years of cross sectional survey data document the downstream movement of a sediment wave in the lower 26 km of this gravel bedded river at a rate of 800 to 1600 m a i durng this period of moderately low flows higher transit rates are associated with reaches of higher unit stream power the wave was initially deposited at a site with an abrupt decrease in channel gradient and increase in channel width the amplitude of the wave has attenuated more than i m as it moved downstream and the duration of the wave increased from eight years upstream to more than 20 years downstream channel aggradation and subsequent degradation have been accommodated across the entire channel bed channel width has not decreased significantly after initial channel widening from large 25 year recurrence interval floods three sets of longitudinal surveys of the streambed showed the highest increase in pool depths and frequency in a degrading reach but even the aggrading reach exhbited some pool development through time the aggraded channel bed switched from functioning as a sediment sink to a significant sediment source as the channel adjusted to high sediment loads from 1980 to 1990 sediment eroded from temporary channel storage represented about 25 per cent ofthe total sediment load and 95 per cent of the bedload exported from the basin

river adjustment to changes in sediment load the effects of tin mining on the ringarooma river tasmania 1875 1984 the mining of alluvial tin in the ringarooma basin began in 1875 reached a peak in 1900 20 and had virtually ceased by 1982 during that time 40 million m3 of mining waste were supplied to the main river quickly replacing the natural bed material and requiring major adjustments to the channel based on estimates of sediment supply from more than 50 widely scattered mines and the frequency of flows capable of transporting the introduced load the river s transport history is reconstructed using a mass conservation model because of the lengthy time period 110 years and river distance 75 km involved the model cannot predict detailed change but it does reproduce the main pattern of sediment movement in which successive phases of aggradation and degradation progress downstream peak storage is predicted in that part of the river where braiding and anastomosis are best developed aggradation was most rapid in the upper reaches close to major supply points becoming slower and later with distance downstream channel width increased by up to 300 per cent where the valley floor was broad and braiding became relatively common bridges had frequently to be replaced while bed levels were still rising in lower reaches degradation began in upper ones notably after 1950 and by 1984 had progressed downriver over 30 km rates of incision reached 0 5 m yr 1 especially in the early 1970s when record high flows occurred as a result of degradation the bed material became gravelly through either reexposure of the original bed or lag concentration of coarser fractions also a narrower unbraided channel has developed the river is beginning to heal itself and upper reaches now have reasonably stable beds but at least another 50 years will be required for the river to cleanse its channel of mining debris

hydro geomorphic hazards and impact of man made structures during the catastrophic flood of june 2000 in the upper guil catchment queyras southern french alps the guil river valley queyras southern french alps is prone to catastrophic floods as the long historical archives and holocene sedimentary records demonstrate in june 2000 the upper part of this valley was affected by a b30 yearq recurrence interval r i flood although of lower magnitude and somewhat different nature from that of 1957 n100 year r i flood the 2000 event induced serious damage to infrastructure and buildings on the valley floor use of methods including high resolution aerial photography multi date mapping hydraulic calculations and field observations made possible the characterisation of the geomorphic impacts on the guil river and its tributaries the total rainfall 260 mm in four days and maximum hourly intensity 17 3 mm h 1 aggravated by pre existing saturated soils explain the immediate response of the fluvial system and the subsequent destabilisation of slopes abundant water and sediment supply landsliding bank erosion particularly from small catchment basins cut into slaty schist bedrock resulted in destructive pulses of debris flow and hyperconcentrated flows the specific stream power of the guil and its tributaries was greater than the critical stream power thus explaining the abundant sediment transport the guil discharge was estimated as 180 m 3 s 1 at aiguilles compared to the annual mean discharge of 6 m 3 s 1 and a june mean discharge of 18 m 3 s 1 the impacts on the guil valley floor flooding aggradation generalised bank erosion and changes in the river pattern were widespread and locally influenced by variations in the floodplain slope and or channel geometry the stream partially reoccupied former channels abandoned or modified in their geometry by various structures built during the last four decades as exemplified by the aiguilles case study where the worst damage took place a comparative study of the geomorphic consequences of both the 1957 and 2000 floods shows that despite their poor maintenance the flood control structures built after the 1957 event were relatively efficient in contrast to unprotected places the comparison also demonstrates the role of land use changes conversion from traditional agro pastoral life to a ski hikingbased economy construction of various structures in reducing the guil channel capacity and more generally in increasing the vulnerability of the human installations the efficiency of the measures taken after the 2000 flood narrowing and digging out of the channel is also assessed final evaluation suggests that in such high mountainous environments there is a need to keep

floodplain stages in the braided ngaruroro river new zealand this study investigates floodplain deposits in the braided ngaruroro river new zealand to characterize and quantify the spatial extent of deposits at different stages of development using a sequence of aerial photography depositional surfaces were mapped and then assigned a floodplain development stage based on age the discharge causing inundation and field observations of sediment and vegetation characteristics the ensemble of floodplain deposits makes up 40 of the river valley the remainder being the active river bed stabilizing bars and mature floodplains dominate the floodplain ensemble while the existence of stabilizing bars points to a recent shift or fluctuation in controlling conditions the extent and location of mature units suggest an earlier change in hydrologic and sediment supply conditions that limited braidtrain mobility mosaics of different aged deposits range from simple two stage mosaics to more complex arrangements of three and four stages in the rapid evolution from stabilized bars to mature floodplains a large amount of fine grained sediment is stored in the ngaruroro river valley highlighting the possibility of finding extensive fine grained facies in the ancient sedimentary record of braided systems understanding floodplain ensembles and their controls will contribute to effective restoration of braided rivers

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

channel response to increased and decreased bedload supply from land use change contrasts between two catchments abstract the catchments of pine creek idaho usa 200 km 2 and the drome river in the drome department france 1640 km 2 illustrate contrasting changes in land use bedload sediment production and channel response hard rock mining began in the catchment of pine creek near the end of the 19th century and together with road construction timber harvest and historically heavy grazing of uplands resulted in increased tributary bedload yield increased bedload migrating to the channel combined with removal of large cedar trees on the floodplain resulted in channel instability which propagated downstream over a period of decades on many reaches of pine creek active channel width has increased by over 50 since 1933 over roughly the same time period the drome river catchment was extensively reforested after at least one century of denudation and heavy grazing and numerous check dams were constructed on torrents to reduce erosion as a result the drome river has experienced a reduction in bedload sediment supply since the late 19th century in addition gravel has been extracted from some reaches consequently the channel has degraded and gravel bars have been colonized with woody riparian vegetation channel widths in wide braided reaches decreased from 1947 to 1970 by 60 on pine creek channel instability has resulted in bank erosion exposing contaminated mine tailings and increased flood hazard on the drome river degradation has undermined bridges and embankments and lowered the water table in areas dependent on groundwater for irrigation resulting in loss of 6 million m 3 of groundwater storage since 1960 though they differ in drainage area by nearly an order of magnitude pine creek and the drome river provide an excellent contrast in that they represent two sides of an epicycle of alluvial sedimentation set off in each case by land disturbance in both cases the most recent channel changes though in opposite directions were viewed as negative by river managers on pine creek managers have removed or protected from erosion mine tailings and have attempted to train the stream into a more stable channel and most rock waste piles the principal sediment sources have recently been controlled on the drome river managers have prohibited gravel mining and adopted new policies to permit coarse sediment to migrate through the river system

fluvialcorridor a new arcgis toolbox package for multiscale riverscape exploration abstract both for scientists and river basin managers development of automated geographic information system gis tools is essential today to characterize riverscapes and explore biogeomorphologic processes over large channel networks since the 1990s gis toolboxes and add in programs have been used to characterize catchments however there is currently no equivalent to a planimetric and longitudinal characterization of fluvial corridor networks at multiple scales this paper describes fluvialcorridor a new gis toolbox this package allows the user i to extract a large set of riverscape features such as the main components of fluvial corridors from dem and vector layers e g stream network or valley bottom and ii to aggregate spatial features into homogeneous segments and metrics characterizing each of them the methodological frameworks involved have been previously described by alber and piegay 2011 leviandier et al 2012 and bertrand et al 2013 and this contribution focuses on the gis tools allowing the user to automatically operate them a case study on the drome river france is provided to illustrate the potential of the package both for geomorphologic understanding and target management actions fluvialcorridor has been developed for arcgis with the related native python library named arcpy and tested on arcgis 10 0 and 10 1 obviously each component of the package can be used separately however it also provides a complete workflow for fluvial corridor characterization even as the toolbox is continually under development and revision case study database fluvialcorridor package and guidelines are available online at http umrevs isig fr