sediment dynamics over sand ridges on a tideless mid outer continental shelf abstract a sand ridge field with crests oriented ne sw 52 located between 55 and 85 m water depth on the valencia continental shelf spain was mapped with multibeam swath bathymetry and characterized with seismic profiling and sediment sampling boundary layer hydrodynamic measurements conducted over a sand ridge at 66 m depth show evidence of wave and current sediment resuspension during a major storm event with a three year recurrence period from the measured intrawave sediment concentration profiles it is shown that the suspended sediment time evolution is related not only to mean currents but also to the wave field the near bottom shear stress generated during storm conditions reached around 1 n m2 and was able to resuspend and transport sandy and muddy sediments for more than 32 h the total suspended sediment transport in a layer of 1 m above the bottom was around 4000 kg per meter width and directed 160 it is argued that these sand ridges were developed in a shallow environment and there is no evidence of present day ridge migration or morphological degradation it is hypothesized that sediment dynamics affecting sand ridges during storms favors the maintenance of their morphology

sediment budget analysis of slope channel coupling and in channel sediment storage in an upland catchment southeastern australia abstract slope channel coupling and in channel sediment storage can be important factors that influence sediment delivery through catchments sediment budgets offer an appropriate means to assess the role of these factors by quantifying the various components in the catchment sediment transfer system in this study a fine

slope deposits in the upper nalon river basin nw spain an approach to a quantitative comparison the upper nalon river basin cantabrian mountains nw spain exhibits a variety of slope processes and deposits including landslides rockfall and soil creep geomorphic maps were used to quantitatively ascertain the relationships between these deposits and topographic characteristics of exposure gradient and altitude at the nodes of a square grid with 250 m spacing n 926 a correspondence analysis allows the analysis of qualitative variables lithology and origin of deposit and quantitative variables altitude with a class interval of 200 m and gradient in 10 classes the results suggest that lithology is the main conditioning factor of the differences and similarities between deposits

structure and contents of a new geomorphological gis database linked to a geomorphological map with an example from liden central sweden this paper presents the structure and contents of a standardised geomorphological gis database that stores comprehensive scientific geomorphological data and constitutes the basis for processing and extracting spatial thematic data the geodatabase contains spatial information on morphography morphometry hydrography lithology genesis processes and age a unique characteristic of the gis geodatabase is that it is constructed in parallel with a new comprehensive geomorphological mapping system designed with gis applications in mind this close coupling enables easy digitalisation of the information from the geomorphological map into the gis database for use in both scientific and practical applications the selected platform in which the geomorphological vector raster and tabular data are stored is the esri personal geodatabase additional data such as an image of the original geomorphological map dems or aerial orthographic images are also included in the database the structure of the geomorphological database presented in this paper is exemplified for a study site around liden central sweden

bed load and suspended load contributions to migrating sand dunes in equilibrium dunes dominate the bed of sand rivers and are of central importance in predicting flow roughness and water levels the present study has focused on the details of flow and sediment dynamics along migrating sand dunes in equilibrium using a recently developed acoustic system acoustic concentration and velocity profiler new insights are obtained in the behavior of the bed and the suspended load transport along mobile dunes our data have illustrated that due to the presence of a dense sediment layer close to the bed and migrating secondary bedforms over the stoss side of the dune toward the dune crest the near bed flow and sediment processes are significantly different from the near bed flow and sediment dynamics measured over fixed dunes it was observed that the shape of the total sediment transport distribution along dunes is mainly dominated by the bed load transport although the bed load and the suspended load transport are of the same order of magnitude this means that it was especially the bed load transport that is responsible for the continuous erosion and deposition of sediment along the migrating dunes whereas the bed load is entirely captured in the dune with zero transport at the flow reattachment point a significant part of the suspended load is advected to the downstream dune depending on the flow conditions for the two flow conditions measured the bypass fraction was about 10 for flow with a froude number fr of 0 41 and 27 for flow with froude number of 0 51 this means that respectively 90 for the fr 0 41 flow and 73 for the fr 0 51 flow of the total sediment load that arrived at the dune crests contributed to the migration of the dunes

geomorphological and sedimentological analysis of a catastrophic flash flood in the aras drainage basin central pyrenees spain abstract on august 7th 1996 an intense and short duration convective storm occurred over the 18 6 km 2 aras drainage basin central pyrenees spain this high relief basin is composed of three subbasins aso betes and la selva and feeds the aras alluvial fan in the gallego river valley this alluvial fan had been drained by an artificial channel about 125 m 3 s at bank full capacity more than 30 check dams in its feeder channel the aras barranco had been previously filled by earlier sediments the heaviest rain was over the betes subbasin total rainfall 178 4 mm maximum rainfall intensity of 153 mm h for a 10 min time interval was estimated most of the rainfall fell in a 70 min period this storm resulted in high runoff causing catastrophic damage and significant geomorphic changes in the drainage basin especially in the betes subbasin the high discharge concentrated in the aras barranco destroyed most of the check dams flushing out a great amount of debris major channel trenching and widening occurred in this barranco when the confined sediment laden flash flood reached the basin mouth it sheet flooded the southern sector of the aras fan depositing a massive amount of debris on this fan 87 people lost their lives and the direct physical damage has been estimated at 55 million dollars two stages in the development of the flood have been differentiated from the sedimentological and morphological analysis of the flooded fan lobe a first stage peak discharge of sheet flooding deposited a coarse boulder lobe burying the artificial channel at the fan head and causing a darnming effect on the water flood during the second stage discharge decline the flood made its way through the fan head incising the previous debris accumulation and splitting into two main flow paths

a new symbol and gis based detailed geomorphological mapping system renewal of a scientific discipline for understanding landscape development this paper presents a comprehensive and flexible new geomorphological combination legend that expands the possibilities of current geomorphological mapping concepts the new legend is presented here at scale of 1 10 000 and it combines symbols for hydrography morphometry morphography lithology and structure with colour variations for process genesis and geologic age the piece by piece legend forms a geomorphological alphabet that offers a high diversity of geomorphological information and a possibility for numerous combinations of information this results in a scientific map that is rich in data and which is more informative than most previous maps but is based on a simple legend the system is developed to also be used as a basis for applications in gis the symbol based information in the geomorphological maps can be digitally stored as a powerful database with thematic layers and attribute tables by combining and further developing aspects of different classical mapping systems and techniques into expanded data combinations new possibilities of presentation and storage are developed and thus a strong scientific tool is provided for landscape configuration and the reconstruction of its development in turn the combination paves the way for specific thematic applications the new system is illustrated for two contrasting landscape types the first is located on the border of vorarlberg western austria and liechtenstein in a glacially influenced high altitude alpine setting that is strongly modified by various degradation processes the second area represents a formerly glaciated region in dalarna central sweden near mora an area that is characterized by a variety of aeolian fluvial glaciofluvial and lacustrine depositional and erosional landforms and also reflects isostatic uplift the new method functions well for both areas and results in detailed scientific outlines of both landscape types

spatial distribution of sediment storage types and quantification of valley fill deposits in an alpine basin reintal bavarian alps germany spatial patterns of sediment storage types and associated volumes using a novel approach for quantifying valley fill deposits are presented for a small alpine catchment 17 km 2 in the bavarian alps the different sediment storage types were analysed with respect to geomorphic coupling and sediment flux activity the dominant landforms in the valley in terms of surface area were found to be talus slopes sheets and cones followed by rockfall deposits and alluvial fans and plains more than two thirds of the talus slopes are relict landforms completely decoupled from the geomorphic system notable sediment transport is limited to avalanche tracks debris flows and along floodplains sediment volumes were calculated using a combination of polynomial functions of cross sections seismic refraction and gis modelling a total of 66 seismic refraction profiles were carried out throughout the valley for a more precise determination of sediment thicknesses and to check the bedrock data generated from geomorphometric analysis we calculated the overall sediment volume of the valley fill deposits to be 0 07 km 3 this corresponds to a mean sediment thickness of 23 3 m the seismic refraction data showed that large floodplains and sedimentation areas which have been developed through damming effects from large rockfalls are in general characterised by shallow sediment thicknesses 20 m by contrast the thickness of several talus slopes is more than twice as much for some locations e g narrow sections of valley the polynomial generated cross sections resulted in overestimations of up to one order of magnitude whereas in sections with a moderate valley shape the modelled cross sections are in good accordance with the obtained seismic data for the quantification of valley fill deposits a combined application of bedrock data derived from polynomials and geophysical prospecting is highly recommended d 2003 elsevier b v all rights reserved

near bed hydrodynamics and turbulence below a large scale plunging breaking wave over a mobile barred bed profile detailed measurements are presented of velocities and turbulence under a large scale regular plunging breaking wave in a wave flume measurements were obtained at 12 cross shore locations around a mobile medium sand breaker bar they focused particularly on the dynamics of the wave bottom boundary layer wbl and near bed turbulent kinetic energy tke measured with an acoustic concentration and velocity profiler acvp the breaking process and outer flow hydrodynamics are in agreement with previous laboratory and field observations of plunging waves including a strong undertow in the bar trough region the wbl thickness matches with previous studies at locations offshore from the bar crest but it increases near the breaking wave plunge point this relates possibly to breaking induced tke or to the diverging flow at the shoreward slope of the bar outer flow tke is dominated by wave breaking and exhibits strong spatial variation with largest tke above the breaker bar crest below the plunge point breaking induced turbulence invades the wbl during both crest and trough half cycle this results in an increase in the time averaged tke in the wbl with a factor 3 and an increase in peak onshore and offshore near bed reynolds stresses with a factor 2 from shoaling to breaking region a fraction of locally produced tke is advected offshore over a distance of a few meters to shoaling locations during the wave trough phase and travels back onshore during the crest half cycle the results imply that breaking induced turbulence for large scale conditions may significantly affect near bed sediment transport processes

velocity measurements close to rippled beds in oscillatory flow the results are reported of velocity measurements in oscillatory flow over rippled beds velocities were measured with a laser doppler anemometer in both an oscillating tray rig and an oscillatory flow water channel both self formed and artificial ripples were examined in addition some measurements were made with an apparently plane bed with intense sediment motion the experimental results were compared with the predictions of kalkanis 1964 kajiura 1968 bakker 1973 1974 and sleath 1974 the closest agreement between theory and experiment was obtained with the method of sleath measurements of the eulerian drift velocities showed drift towards the adjacent ripple crest in the immediate vicinity of the bed and away from the crest further out

advances in swash zone research small scale hydrodynamic and sediment transport processes abstract extensive research efforts in the last decade have improved knowledge of swash zone processes this paper reviews and synthesizes from 2004 onward the research advances of small scale hydrodynamics and sediment transport processes considering field laboratory and numerical modeling efforts swash zone hydrodynamics are examined by means of shoreline motions fluid velocities pressure gradients flow structure bed shear stress friction coefficients and turbulence subsequently advances related to sediment transport mechanisms and morphological changes are described detailed descriptions of measuring techniques novel findings and the strengths and weaknesses of the different approaches are discussed the review also acknowledges the major advances in the development of instrumentation to collect highly resolved flow and sediment concentration measurements in direct proximity of the bed and the experimental framework for analyzing local dynamics on a wave by wave time scale e g dam break

suspension and near bed load sediment transport processes above a migrating sand rippled bed under shoaling waves the present study focuses on the fine scale flow and sand transport processes above onshore migrating ripples below skewed surface gravity waves in the shoaling zone a set of acoustic instruments was deployed in the shoaling region of the large scale wave channel at canal d investigacio i experimatacio maritima universitat poltiecnica de catalunya barcelona spain in order to provide high resolution velocity and sediment concentration profiles with an acoustic concentration and velocity profiler acvp measurements are analyzed relative to the positions of the measured nonmoving sand bed and the interface separating the suspension from the near bed load layer this interface is detected here by the application of a novel acoustic bed echo detection method furthermore the use of the dual frequency inversion proposed in the work of hurther et al 2011 allows for the calculation of the sediment concentration profile across both the suspension and near bed load layers the sand bed was covered by quasi two dimensional suborbital ripples migrating onshore as proposed by o donoghue et al 2006 the occurrence of quasi two dimensional ripples is attributed to the fine size sand of d50 250 mm used in the present study under full scale forcing conditions in order to determine the effect of shoaled wave skewness on the ripple vortex entrainment and sediment transport the instantaneous and mean measurements of the flow sediment concentration and sediment flux along the ripple profile are discussed in terms of 1 the occurrence of ripple vortex entrainment on either side of the ripple crest 2 the wave velocity phase lagging driven by the ripple vortex entrainment process and the turbulent bed friction effects in the wave boundary layer 3 phase lagging between velocity and maximum concentration and sediment flux events 4 the structure of bed friction and ripple driven turbulence across the suspension and the near bed load layers and 5 the streaming components the results on these aspects strongly support that the wave velocity skewness effect under shoaling waves is fairly similar to the one obtained in skewed oscillatory water tunnel flows furthermore it is found that the onshore oriented net bed load sediment transport is at the origin of the onshore ripple migration this flux is roughly twice as much as the opposite offshore oriented net suspension flux dominated by the ripple vortex entrainment processes

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

measuring bedload sediment transport with an acoustic doppler velocity profiler abstractacoustic doppler velocity profilers advp measure the velocity simultaneously in a linear array of bins they have been successfully used in the past to measure three dimensional turbulent

the use of landslide units in geomorphological mapping an example in the italian dolomites the mapping of processes and landforms found in a particular territory is usually achieved by means of methods and instruments which are universally accepted and adopted such as those of geomorphological mapping in some cases however these methods do not always give complete understanding of a landscape s evolution in particular this happens in environments with a large number of deposits resulting from gravitational processes this paper aims at illustrating an innovative method for mapping gravitational deposits by considering in particular their spatial and temporal relationships and by grouping them into homogeneous units called landslide units the use of these landslide units would facilitate landscape analysis and allow better understanding of areas which are rather complex from the geomorphological standpoint this type of approach is particularly important for application purposes and the dissemination of results on landslide research especially for non specialists within the framework of the teslec project funded by the european union this investigation method has been applied to the area of cortina d ampezzo italian dolomites where more than thirty landslides have been identified and grouped in 12 landslide units these landslide units also incorporate superficial deposits alluvial and lacustrine deposits scree slopes etc genetically linked to the main landslide phenomena each landslide unit includes lower ranked units which may be either landslide bodies or other deposits directly or indirectly related to them as an example the case of the cortina d ampezzo landslide unit is illustrated and discussed

planetary science bedrock formation at meridiani planum reply squyres 1 contend that our proposed volcanic origin for meridiani planum2 is inconsistent with more recently obtained data3 but although the new data reveal some variation in chemical composition this variation is small fig 1a and mainly due to modest variations in magnesium and sulphur with concentrations of the other elements remaining essentially constant3 in a volcanic model this variation can be readily explained by mobilization of highly soluble magnesium sulphate salts during the later stages of alteration and diagenesis fig 1a as in the sedimentary evaporite model in which sediments that were initially deposited with uniform composition are subsequently modified3 4 5 although morphological features in the bedrock may be consistent with aeolian and fluvial origins6 this interpretation is not unique particularly as features with similar grain size sorting and morphology are seen in base surge deposits2 7 8 9 neither chemical nor morphological data therefore preclude a volcanic origin

paraglacial response of steep sediment mantled slopes to post little ice age glacier recession in the central swiss alps this research assesses the morphological consequences of recent post little ice age paraglacial reworking of valley side sediment mantles in the european alps it aims to identify the extent and conditioning factors of slope adjustment at sites in the swiss alps model the temporal pattern and assess the rates of sediment reworking involved gully systems have cut into steep high level lateral moraines and debris cones have accumulated downslope debris flow is the dominant agent of sediment transfer factors controlling the extent of this activity include moraine slope gradient relief and moisture availability gullies appear to have reached their maximum dimensions within ca 50 yr of deglaciation after which gully relief is reduced by removal of inter gully slopes and gully infilling within 80 140 yr on the most recently deglaciated terrain minimum erosion rates average ca 95 mm yr 1 since gully initiation greatly exceeding normal erosion rates in other environments mean annual accumulation of a single debris cone since ice retreat was calculated to be ca 30 mm yr 1 implications of these findings are applied to patterns of paraglacial sediment mantled slope adjustment conceptualising paraglacial landscape response in terms of a sediment release exhaustion model and paraglacial landform succession copyright 2005 john wiley sons ltd

geochemical and nd isotope composition of detrital sediments on the north margin of the south china sea provenance and tectonic implications a major re organization of regional drainages in eastern tibet and southwestern china took place in the cenozoic as deformation from the growing himalayas and tibetan plateau affected an increasingly wider area the effects of these changes on the regional sediment routing systems is not well constrained this study examines the geochemical and nd signatures of sedimentary rocks from the ying qiong and nanxiong basins on the northern margin of the south china sea to constrain and identify any significant changes in sediment source upper cretaceous to lower eocene sedimentary rocks in the nanxiong basin show higher th sc la sc th cr and th co ratios and lower eu eu ratios than paas post archaean australian shale which indicates that palaeozoic sedimentary rocks of the south china block were the main basin sediment source in contrast oligocene to pleistocene sedimentary rocks of the ying qiong basin show an abrupt change in these trace element ratios between 16ae3 and 10ae4 ma indicating a mid miocene shift in provenance end values from the ying qiong basin range 11ae 1t o 2ae1 reinforce this with pre 13ae8 ma sedimentary rocks having average end of 5ae6 range 2ae 1t o 7ae4 and post 13ae8 ma sedimentary rocks having average end of 9ae3 range 8ae 7t o 11ae1 during the oligocene the centre of rifting transferred south and basins on the north margin of the south china sea experienced rapid subsidence further uplift and erosion then exposed mesozoic and cenozoic granites that supplied large amounts of granitic detritus especially to the ying qiong basin then a change occurred at ca 13 ma resulting in less input from local sources i e the fault blocks formed by mesozoic cenozoic tectonics and magmatism to an increasing contribution of older continental material mostly from indochina to the west of the south

the role of debris supply conditions in predicting debris flow activity debris flow frequency and magnitude were determined for 33 basins in southwest british columbia basins were first classifiedaseitherweathering limitedortransport limitedusingadiscriminantfunctionbasedondebris contributingarea an area weighted terrain stability number and drainage density multiple regression was used to predict magnitude peak discharge frequency and activity frequency times magnitude within each group of basins model performance was improved by stratifying the total sample of debris flow basins into weathering and transport limited groups explained varianceincreasedbyanaverageof15percentinthetransport limitedsample indicatingthatsedimentsupplyconditionsin themoreactivebasinsarefundamentalinpredictingdebrisflowactivity anindependenttestoftheregressionmodelswith 11basinsyieldedgenerallygoodresultsfordebrisflowmagnitudeandpeakdischarge predictionofdebrisflowfrequency provedproblematicalinweathering limitedbasins themethodsdevelopedhereprovideestimatesofdebrisflowattributes in basins for which few data on past events are available copyright 1999 john wiley sons ltd

intrawave observations of sediment entrainment processes above sand ripples under irregular waves 1 measurements of intrawave sediment entrainment processes are reported above ripples under irregular waves generated in a large scale flume facility the data consist of substantive observations of small scale processes collected at high spatial and temporal resolution under irregular wave forcing typical of coastal environments acoustic measurements were made of water velocities bed forms and suspended sediment concentration over plane and rippled beds during each rippled bed experiment measurements were taken over the crests of steep sided ripples above which flow separation was considered likely to occur above the ripple crests a strong intrawave variation in the near bed suspended sediment indicative of vortex formation and shedding was observed to dominate wave half cycles where the orbital diameter was greater than 1 2 times the ripple wavelength l the irregular waves were parameterized with a significant wave height hs and a significant orbital diameter d0s thus during irregular wave conditions and over steep ripples where d0s l 1 2 vortex shedding was deemed as the dominant sediment entrainment process furthermore the percentage of wave half cycles where vortex shedding was observed was found to scale as 26 d0s l these results demonstrate for under irregular waves the existence of a clear suspended sediment structure consistent with vortex shedding previously observed under regular waves citation o hara murray r b p d thorne and d m hodgson 2011 intrawave observations of sediment entrainment processes above sand ripples under irregular waves j geophys res 116 c01001 doi 10 1029 2010jc006216

variability in sediment supply transfer and deposition in an upland torrent system iron crag northern england research into torrent erosion has focused on bedload transport dynamics debris flow propagation during flood events and fan sedimentation studies have frequently been biased towards specific events and have not considered sediment delivery in the catchment as a whole the aim of this study is to examine spatial variations and process controls on sediment transfer in an upland torrent system hillslopes channel and fan the study site is iron crag a small torrent system catchment area 2 4 ha situated in the northern lake district uk particle size analysis of hillslope sediments trapped during transport suggests sediment calibre is controlled primarily by sediment source freeze thaw and rainfall processes impart a weak but recognizable size sorting signature on the trapped sediments however these variations are less significant in determining sediment supply to the basal fan than those operating in the channel system channel sediment movement is strongly influenced by storm events the type of flow process debris flow or fluvial flow the sediment characteristics and the local channel topography the importance of the channel fan coupling is clearly demonstrated in that more than 90 per cent of fan sedimentation is derived from channel sediment sources copyright 2006 john wiley sons ltd

experimental evidence for turbulent sediment flux constituting a large portion of the total sediment flux along migrating sand dunes accurate estimation of sediment transport is critical for many fluvial processes but remains challenging due to high frequency dynamics using novel acoustic flow instrumentation we quantified the contribution of turbulent bed and suspended sediment fluxes to the total sediment fluxes along an entire dune profile and over the full flow depth we found that over the dune stoss side and in the bed load layer the turbulent mean streamwise flux is negative and reaches up to 40 of the total mean streamwise flux over the lee side where turbulent intensities are highest the contribution of the turbulent mean streamwise flux to the total mean streamwise flux is larger and reaches up to 50 the mean vertical turbulent flux along the entire dune bed and in the bed load layer reaches nearly 30 of the total mean vertical flux turbulent sediment flux may thus constitute a large component of the total flux

bedload and suspended load contributions to breaker bar morphodynamics abstract this study presents measurements of sheet flow processes grain sorting and bedload plus suspended load transport rates around a medium sand breaker bar in a large scale wave flume the results offer insights in effects of wave breaking on bedload and grain sorting processes and in the quantitative contributions by bedload and suspended transport to breaker bar morphodynamics sheet flow layer dynamics are highly similar to observations under non breaking waves revealing clear effects by velocity asymmetry but no evident effects by breaking generated turbulence bed slope or the cross shore non uniform flow the sheet flow layer thickness can be predicted using existing empirical formulations based on local hydrodynamic forcing at locations covering the shoaling region up to the bar crest the cross shore variation in bedload transport rates is explained by variations in wave shape i e velocity skewness and asymmetry at locations between bar crest and bar trough bedload transport rate magnitudes correlate positively with bed slope and turbulent kinetic energy bedload and suspended load transport rates are of similar magnitude but of opposite sign bedload transport is onshore directed and dominates in the shoaling zone but after wave breaking the offshore directed suspended sediment transport increases in magnitude and exceeds bedload transport rates in the breaking and inner surf zones bedload and suspended load transport contribute notably differently to bed profile evolution bedload transfers sand grains from the offshore slope to the bar crest and additionally leads to erosion of the shoreward bar slope and deposition at the bar trough while suspended load transport induces an opposite pattern of erosion at the bar trough and accretion at the bar crest grain size analysis of suspended sediment samples reveals size selective entrainment and vertical size segregation in the inner surf zone but suggest size indifferent entrainment and vertical mixing by energetic vortices in the breaking region size selective transport by bedload and suspended load leads to a cross shore coarsening of the bed from shoaling to inner surf zone with local additional sorting mechanisms around the breaker bar due to bed slope effects

a sharp view on river dune transition to upper stage plane bed sandy river beds are dominated by rhythmic features known as dunes experimental investigations of turbulent flow and sediment transport over dunes have predominantly focused on equilibrium flows that are rare in natural rivers using a novel acoustic instrument over migrating dunes in a laboratory setting we quantify a number of dynamical properties that are crucial in our understanding and modeling of dune morphology and kinematics particularly under nonequilibrium flows during dune transition to upper stage plane bed measured sediment transport distributions reveal a positive spatial lag between dune crest and maximum sediment transport rate that eventually caused washing out of dunes bed load was entirely captured in dune troughs contributing to dune translation where most of suspended load was advected further downstream contributing to dune deformation measured bypass fraction was about 76 which means that only 24 of the total sediment load at the dune crest contributed to dune migration

comparing models of debris flow susceptibility in the alpine environment abstract debris flows are widespread in val di fassa trento province eastern italian alps where they constitute one of the most dangerous gravity induced surface processes from a large set of environmental characteristics and a detailed inventory of debris flows we developed five models to predict location of debris flow source areas the models differ in approach statistical vs physically based and type of terrain unit of reference slope unit vs grid cell in the statistical models a mix of several environmental factors classified areas with different debris flow susceptibility however the factors that exert a strong discriminant power reduce to conditions of high slope gradient pasture or no vegetation cover availability of detrital material and active erosional processes since slope and land use are also used in the physically based approach all model results are largely controlled by the same leading variables overlaying susceptibility maps produced by the different methods statistical vs physically based for the same terrain unit of reference grid cell reveals a large difference nearly 25 spatial mismatch the spatial discrepancy exceeds 30 for susceptibility maps generated by the same method discriminant analysis but different terrain units slope unit vs grid cell the size of the terrain unit also led to different susceptibility maps almost 20 spatial mismatch maps based on different statistical tools discriminant analysis vs logistic regression differed least less than 10 hence method and terrain unit proved to be equally important in mapping susceptibility model performance was evaluated from the percentages of terrain units that each model correctly classifies the number of debris flow falling within the area classified as unstable by each model and through the metric of roc curves although all techniques implemented yielded results essentially comparable the discriminant model based on the partition of the study area into small slope units may constitute the most suitable approach to regional debris flow assessment in the alpine environment

stereophotogrammetry of archive data and topographic approaches to debris flow torrent measurements calculation of channel sediment states and a partial sediment budget for manival torrent isere france this paper focuses on a topographic methodology to characterize the amount of sediment stored in channels and the use of historical photographs for aerial survey by stereophotogrammetry as part of wider research on debris flow magnitude prediction the topographic methodology uses equidistant four point cross sections along the long profile of the channel each cross section is representative of a 50 m reach of the channel to calculate the volume of each reach the difference is calculated between a reference level and the topographic surface the reference level is the lowest level where the debris flow can erode and in the current method this level is estimated from fixed points along the long profile of the channel the accuracy of the method has been estimated by comparing results of a detailed topographic survey with a standard deviation corresponding to about 6 per cent of the total calculated sediment volume this topographic methodology has been used on aerial photographs by photogrammetry this tool was applied to photographs taken on 12 past dates the scales of the archive photographs used range from 1 3000 to 1 30 000 but results are consistent and permit us to calculate sediment states of the channel for different past dates with an uncertainty of about 6 per cent of the total volume the application of the technique to the manival debris flow torrent has permitted us to propose some partial sediment budgets and erosion rate estimates copyright 2006 john wiley sons ltd

observations and analysis of sediment diffusivity profiles over sandy rippled beds under waves acoustic measurements of near bed sediment diffusivity profiles are reported the observations were made over two sandy rippled beds classified as medium and fine in terms of sand grain size under slightly asymmetric regular waves for the medium sand the ripples that formed had relatively steep slopes while for the fine sand the slopes were roughly half that of the medium sand in the medium sand case the form of the sediment diffusivity profiles was found to be constant with height above the bed to a height equal approximately to the equivalent roughness of the bed ks while above this the sediment diffusivity increased linearly with height for the case of the fine sand there was no constant region the sediment diffusivity simply increased linearly with height from the bed to understand the difference between the respective diffusivity profiles advantage has been taken of the high temporal spatial resolution available with acoustic systems using intra wave ensemble averaging detailed images have been built up of the variation in concentration with both the phase of the wave and also height above the bed these intra wave observations combined with measurements of the bed forms and concepts of convective and diffusive entrainment have been used to elucidate the mixing mechanisms that underlie the form of the diffusivity profiles observed over the two rippled beds these mechanisms centre on coherent vortex shedding in the case of steeply rippled beds and random turbulent processes above ripples of lower steepness

a multi method approach to study the stability of natural slopes and landslide susceptibility mapping abstract in this paper a multi method approach for the assessment of the stability of natural slopes and landslide hazard mapping applied to the dakar coastal region is presented this approach is based on the effective combination of geotechnical field and laboratory works of gis and of mechanical deterministic and numerical stability analysis by using this approach valuable results were gained regarding instability factors landslide kinematics simulation of slope failure and coastal erosion this led to a thorough assessment and strong reduction in the subjectivity of the slope stability and hazard assessment and to the development of an objective landslide danger map of the sw coast of dakar analysis of the results shows that the slides were influenced by the geotechnical properties of the soil the weathering the hydrogeological situation and the erosion by waves the landslide susceptibility assessment based on this methodological approach has allowed for an appropriate and adequate consideration of the multiple factors affecting the stability and the optimization of planning and investment for land development in the city

a multi frequency acoustic concentration and velocity profiler acvp for boundary layer measurements of fine scale flow and sediment transport processes the use of acoustics to measure sediment transport boundary layer processes has gained increasing acceptance over the past two decades this has occurred through the development of increasingly sophisticated measuring systems and theoretical developments which have enabled flow and suspended sediment parameters to be obtained from acoustic data with a high degree of accuracy until relatively recently separate acoustic systems were used to measure flow and suspended sediment concentration over the past few years however the technology has become sufficiently advanced so that flow and sediment measurements can be integrated into a single system this integration provides quasi instantaneous non intrusive co located high temporal spatial resolution measurements of benthic flow and sediment processes here the development of such an instrument the acoustic concentration and velocity profiler acvp is described the theory underpinning its application is outlined new approaches to velocity de aliasing and suspended sediment inversion instabilities using multi frequency capabilities are presented and the application of the system to sediment transport processes over a sandy ripple bed is illustrated the observations clearly show the value of such instrumentation for studying the dynamical interaction between the bed the flow and the sediments at and within the bottom boundary layer

the effectiveness of hillshade maps and expert knowledge in mapping old deep seated landslides large deep seated landslides with a shear surface deeper than 3 m and a mean affected area of 4 2 ha are common features in the flemish ardennes none of these deep seated landslides are dated but they are assumed to be rather old 100 years because most of these landslides are located under forest aerial photo interpretation commonly used for the creation of landslide inventories is not a suitable tool to map the landslides in the flemish ardennes therefore an intensive 100 day field survey was carried out by two geomorphologists in a 430 km 2 study area this resulted in a landslide inventory map indicating the location of 135 large deep seated landslides but field surveys are time consuming and thus very expensive therefore a cheaper and faster mapping technique was tested a hillshade map was constructed for the study area in a gis idris132 from a 5 m resolution digital elevation model dem seven experts were given 1 h to indicate all the hillslope sections which they suspected to be possible landslides on a copy of the aforementioned map scale 1 100 000 in total this exercise took only 1 day i e 7 person hours large differences in the number of presumed landslides and the extent of the hillslopes thought to be affected by landslides were reported among the seven experts the polygon and pixel efficiency were introduced to estimate the quality of the landslide maps based on hillshade maps and expert knowledge compared to the field survey based landslide inventory the quality of the landslide inventories based on the hillshade maps and expert knowledge was relatively low experts familiar with the study area obtained somewhat better results than experts who visited the study area only once a combination of the seven expert maps did not result in a good inventory map because too many unaffected hillslopes were incorrectly indicated as affected by landslides the results obtained in this study are comparable to an investigation carried out by wills c j mccrink t p 2002 comparing landslide inventories the map depends on the method environmental and engineering geoscience 8 279 293 although the tested method can never replace a detailed field survey taking into account the proposed improvements it can be used for the creation of a regional inventory map of old landslides in a densely forested area where light detection and ranging lidar data are unavailable c 2004 elsevier b v all rights reserved

magnitude frequency relationships of debris flows and debris avalanches in relation to slope relief abstract probability of occurrence hazard intensity and encounter probability are key parameters in the quantitative risk analysis qra of landslides all are strongly dependent on magnitude of the landslides as a result magnitude frequency analysis should be a part of qra deriving representative magnitude frequency relationships for debris avalanches and debris flows however is difficult one key problem is illustrated with the example of a unique database from the coastal region of british columbia canada which was compiled entirely from detailed ground investigations the magnitude of debris avalanches and debris flows is not an independent statistical quantity but a function of the scale of a given slope as characterized by the slope length thus attempting to derive probability and magnitude for a given location or sub region from a regionally derived magnitude frequency curve may lead to incorrect predictions the same problem is pertinent to the application of the same approach to any type of landslide in which the largest combined dimension of the source volume including entrainment is of the same order as the length of the slope it is recommended that greater emphasis be placed on site specific geological observations at the expense of generalized statistics

full scale observations of wave induced vortex generation over a rippled bed 1 our understanding of vortex generation over rippled beds is largely based on small scale laboratory studies the insight provided by such studies has been considerable although questions remain regarding the applicability to the field this paper presents observations from a full scale investigation of wave induced vortex generation events over a movable sediment bed observations of the two dimensional time varying velocity field were obtained with a submersible particle image velocimetry piv system in a field scale experimental environment at the o h hinsdale wave research laboratory the observations were obtained over an irregularly rippled bed with ripple height and wavelength of roughly 0 01 m and 0 1 m respectively the vortices generated during offshore directed flow over the steeper bed form slope were regularly ejected into the water column and were consistent with conceptual models of the oscillatory flow over a backward facing step the observations allowed for an examination of the generation and subsequent ejection of individual vortical structures vortical structures are identified with a measure of the flow field that estimates the time for a complete revolution of a vortex called swirling strength an analysis of these structures reveals that the swirling strength nondimensionalized by the wave period is correlated to the keulegan carpenter these results offer new insight into fluid sediment interaction over rippled beds

wave bottom boundary layer processes below irregular surfzone breaking waves with light weight sheet flow particle transport the present work investigates the structure of the near bed flow below irregular surfzone breaking waves inducing light weight sheet flow particle transport the experiments are carried out in the legi flume under steady equilibrium conditions between the wave forcing and the underlying bed morphology synchronized acvp and video images provide detailed information about the mean wave and current characteristics and the coupled flow regimes across the entire wave breaking region including the outer and the inner surfzones an analysis of the impact of breaking eddies in the wave boundary layer wbl is undertaken at the beginning of the inner surfzone subsequently the intrawave variation of several contributions of the total shearing force per unit area and the net values of the reynolds stress related to phase averaged velocities are analyzed it is found that the wave component is the dominant term the turbulent reynolds stress the low frequency and the mean terms are at least 1 order of magnitude lower due to the irregular wave forcing the net values are separated into the net wave by wave reynolds stress and the wave reynolds stress averaged over the entire irregular wave sequence all these measured bed shear stress terms are then compared to estimations obtained with two different parameterized models in order to evaluate their prediction performances the values of the model parameters are discussed in comparison to those found in the literature finally the vertical profile of net reynolds shear stress exhibits a nearly constant value across the sheet flow layer

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

mapping geomorphology a journey from paper maps through computer mapping to gis and virtual reality abstract maps are integral components of research in geomorphology and quaternary geology visual presentation of the spatial and temporal distribution of a phenomenon often provides clues to the process es that generated the phenomenon compiling information on maps interpreting spatial patterns and using standard topographic maps were fundamental parts of the undergraduate experience why have such experiences been slowly disappearing from undergraduate curricula how are geology majors taught map scale map projections and the pitfalls associated with the display of spatial information neglect in preserving the mapping tradition places the geology major at a disadvantage the use of maps and mapping is undergoing a renaissance use in the classroom has a bright future because of digital scanning computer cartography geographic information systems gis and virtual reality pen and ink techniques should be relegated to museums pencil sketches can be scanned and perfect products generated every time these techniques however do not eliminate the need for basic map knowledge such as scale projections and generalization what assumptions about map projections have been built into the software how are spatial data and attribute data integrated into the resultant map in a geographic information system gis because the application of virtual reality to geomorphic processes looms on the horizon geologists must recognize how the current spatial revolution can help with the assessment of geologic phenomena and teach students to function with the new technology

detailed measurements of velocities and suspended sand concentrations over full scale ripples in regular oscillatory flow the knowledge and modeling of wave induced sand transport over rippled beds still has significant shortcomings which is partly related to a lack of measurements of the detailed processes from controlled laboratory experiments we have carried out new measurements of the detailed time dependent velocity and suspended sand concentration field around vortex ripples for regular oscillatory flow conditions the fact that the ripples were mobile and the flow conditions were full scale makes these measurements unique we made velocity measurements for 14 different flows and concentration measurements for three of these flows the velocity and concentration field above ripples are dominated by the generation and ejection of vortices on the ripple flanks around the time of flow reversal vortex formation results in near ripple flow reversals ahead of free stream reversals and velocity maxima near the ripple crest that are much higher than the free stream maxima asymmetry in the free stream produces steady circulation cells with dominant offshore mean flow up the ripple lee slope balanced by weaker onshore streaming up the ripple stoss slope as well as higher up in the flow the time and bed averaged horizontal velocity profile comprises an offshore streaming near the bed and an onshore drift higher up in the flow the vortices are responsible for three main concentration peaks one just after on offshore flow reversal associated with the passage of a sand laden vortex followed by two smaller peaks due to advected suspension clouds generated by vortex action at the neighboring onshore ripples the sand flux field measured for one typical asymmetric flow condition is dominated by an offshore flux associated with the suspended sand cloud generated by vortex shedding from the ripple s lee slope around the time of on offshore flow reversal the net time averaged current related and wave related horizontal sand fluxes are generally offshore directed and mostly contained within 1 5 ripple heights above the ripple crest the wave related suspended transport component is larger but the contribution of the current related suspended sand transport cannot be neglected in addition to the measured offshore net transport of suspended sand there is an onshore directed transport very close to the ripple surface the total net transport is in the offshore direction for this specific asymmetric flow condition

triggering conditions and mobility of debris flows associated to complex earthflows landslides on black marl slopes of the french alps are in most cases complex catastrophic failures in which the initial structural slides transform into slow moving earthflows under specific hydrological conditions these earthflows can transform into debris flows due to their sediment volume and their high mobility debris flow induced by landslides are far much dangerous than these resulting from continuous erosive processes a fundamental point to correctly delineate the area exposed to debris flows on the alluvial fans is therefore to understand why and how some earthflows transform into debris flow while most of them stabilize in this paper a case of transformation from earthflow to debris flow is presented and analysed an approach combining geomorphology hydrology geotechnics and rheology is adopted to model the debris flow initiation failure stage and its runout postfailure stage using the super sauze earthflow alpes de haute provence france as a case study the objective is to characterize the hydrological and mechanical conditions leading to debris flow initiation in such cohesive material results show a very good agreement between the observed runout distances and these calculated using the debris flow modeling code cemagref 1 d the deposit thickness in the depositional area and the velocities of the debris flows are also well reproduced furthermore a dynamic slope stability analysis shows that conditions in the debris source area under average pore water pressures and moisture contents are close to failure a small excess of water can therefore initiate failure seepage analysis is used to estimate the volume of debris that can be released for several hydroclimatic conditions the failed volumes are then introduced in the cemagref 1 d runout code to propose debris flow hazard scenarios results show that clayey earthflow can transform under 5 year return period rainfall conditions into 1 km runout debris flow of volumes ranging between 2000 to 5000 m 3 slope failures induced by 25 year return period rainfall can trigger large debris flow events 30 000 to 50 000 m 3 that can reach the alluvial fan and cause damage

expert driven semi automated geomorphological mapping for a mountainous area using a laser dtm in this paper a semi automated method is presented to recognize and spatially delineate geomorphological units in mountainous forested ecosystems using statistical information extracted from a 1 m resolution laser digital elevation dataset the method was applied to a mountainous area in austria first slope angle and elevation characteristics were determined for each key geomorphological unit occurring in the study area second a map of slope classes derived from the laser dtm was used in an expert driven multilevel object oriented approach the resulting classes represent units corresponding to landforms and processes commonly recognized in mountain areas fluvial terrace alluvial fan slope with mass movement talus slope rock cliff glacial landform shallow incised channel and deep incised channel the classification result was compared with a validation dataset of geomorphological units derived from an analogue geomorphological map for the above mentioned classes the percentages of correctly classified grid cells are 69 79 50 64 32 61 23 and 70 respectively the lower values of 32 and 23 are mainly related to inaccurate mapping of rock cliffs and shallow incised channels in the analogue geomorphological map the accuracy increased to 76 and 54 respectively if a buffer is applied to these specific units it is concluded that high resolution topographical data derived from laser dtms are useful for the extraction of geomorphological units in mountain areas

landslide susceptibility zonation in the rio mendoza valley argentina a qualitative landslide susceptibility zonation map scale 1 100 000 of a sector of the rio mendoza valley was prepared by overlapping thematic maps of conditioning factors the main parameters affecting the distribution of landslides in the area were ranked according to slope instability geomorphological surveys and field observations enabled identification of 300 historical or prehistoric landslides a landslide inventory was developed classifying the processes involved in slope instability and analysing the degree of activity the two most influential factors in decreasing slope stability were lithology and slope angle

reconstructing spatio temporal patterns of debris flow activity using dendrogeomorphological methods debris flows are a major threat in many parts of the alps where they repeatedly cause severe damage to infrastructure and transportation corridors or even loss of life nonetheless the spatial behavior of past debris flow activity and the analysis of areas affected during particular events have been widely neglected in reconstructions so far it was therefore the purpose of this study to reconstruct spatio temporal patterns of past debris flows on a forested cone in the swiss alps bruchji torrent blatten valais the analysis of past events was based on a detailed geomorphic map 1 1000 of all forms related to debris flows as well as on tree ring series from 401 heavily affected trees larix decidua mill and picea abies l karst growing in or next to deposits the samples were analyzed and growth disturbances related to debris flow activity assessed such as tangential rows of traumatic resin ducts the onset of reaction wood or abrupt growth suppression or release in total 960 growth disturbances were identified in the samples belonging to 40 different event years between a d 1867 and 2005 in addition the coupling of tree ring data with the geomorphic map allowed reconstruction of eleven formerly active channels and spatial representation of individual events based on our results we believe that before 1935 debris flows preferentially used those channels located in the western part of the cone whereas the eastern part of the cone remained widely unaffected the spatial representation of the 40 events also allowed identification of five different spatial patterns for debris flows at the study site 2006 elsevier b v all rights reserved

within catchment variability in landscape connectivity measures in the garang catchment upper yellow river abstract the degree of landscape connection has wide ranging implications for sediment availability frequency of transport and the nature of sediment storage within a basin two methodological approaches for assessing landscape connectivity are applied within the garang subcatchment of the upper yellow river a gis based geomorphometric index was calculated for the catchment and compared to a methodology linking interpretation of satellite imagery and field mapping of sediment storage to slope threshold analysis landscapes of the garang catchment are highly contrasting and can be separated into three zones i a highly disconnected upper catchment of low relief with large inactive sediment stores ii a transitional zone where present landscape dynamics are controlled in large part by past incisional processes in the form of large alluvial fan terrace deposits and iii a highly connected and highly dissected landscape within the lower catchment that has little accommodation space for sediment storage the geomorphometric index shows general agreement with the patterns in landscape connectivity observed through imagery and field investigations however it estimates similar levels of connectivity in landscapes with observed dis connectivity reflecting limitations of the calculation while rapidly calculated geomorphometric indices of landscape connectivity provide useful appraisals of relative within catchment variability in systems such as the garang catchment caution is urged in conducting broader scale analyses using the same tools findings from this study highlight the importance of field informed appraisals of landscape dynamics site specific characteristics and the imprint of historical evolutionary context in making such comparative assessments

comparison of measurements and models of bed stress bedforms and suspended sediments under combined currents and waves abstract this study presents an analysis of data collected in an embayment off a sandy beach protected by shore parallel breakwaters observations were carried out over a forty day period including spring and neap tidal cycles and low and high wave activity measurements were collected on the waves currents bedforms and suspended sediments and these were used to derive estimates of the bed shear stresses ripple dimensions reference concentrations and suspended sediment profiles the aim of the present study was to use the measurements to assess commonly employed empirical formulations applied to sediment modelling in the coastal marine environment assessments are made of four ripple predictors two formulations of reference concentration and power law and exponential suspended sediment shape functions in some cases predicted parameters are well represented during low wave conditions whilst other parameters are better predicted under high wave events the outcome from the work is an evaluation of the predictive capability of the selected empirical formulae at the sandy location and discussions on the comparison between the observations and predictions

suspended sediment transport around a large scale laboratory breaker bar this paper presents novel insights into suspended sediment concentrations and fluxes under a large scale laboratory plunging wave measurements of sediment concentrations and velocities were taken at 12 locations around an evolving breaker bar covering the complete breaking region from shoaling to inner surf zone with particular high resolution near the bed using an acoustic concentration and velocity profiler wave breaking evidently affects sediment pick up rates which increase by an order of magnitude from shoaling to breaking zone time averaged reference concentrations correlate poorly with periodic and time averaged near bed velocities but correlate significantly with near bed time averaged turbulent kinetic energy the net depth integrated suspended transport is offshore directed and primarily attributed to current related fluxes undertow at outer flow elevations i e above the wave bottom boundary layer the wave related suspended transport is onshore directed and is generally confined to the wave bottom boundary layer cross shore gradients of sediment fluxes are quantified to explain spatial patterns of sediment pick up and deposition and of cross shore sediment advection suspended particles travel back and forth between the breaking and shoaling zones following the orbital motion leading to local intra wave concentration changes at locations between the breaker bar crest and bar trough intra wave concentration changes are due to a combination of horizontal advection and of vertical exchange with the bedload layer sediment is entrained in the bar trough during the wave trough phase almost instantly advected offshore and deposited near the bar crest during the wave crest phase finally these results are used to suggest improvements for suspended sediment transport models

the contribution of geomorphological mapping to sediment transfer evaluation in small alpine catchments the assessment of sediment transfer processes is necessary to understand the hydro geomorphological functioning of small alpine watersheds prone to channelised debris flows because their occurrence often depends on the amount of debris available in the gully systems therefore sediment budgets should be studied through the identification of erosion transport and deposition processes sediment transfer processes were investigated in a small catchment by field measurements and more specifically through the application of a process based geomorphological mapping method the proposed methodology is based on data directly derived from gis analysis using high resolution dem field measurements and aerial photograph interpretations it has been conceived to estimate sediment transfer dynamics taking into account the role of different sediment stores in the torrential system the proposed geomorphological mapping methodology is quite innovative in comparison with most legend systems that are not adequate for mapping comprehensively active and complex geomorphological systems such as debris flow catchments maps representing the various sediment storages and their relationships can be used for hydro geomorphological hazard mitigation

gis based landslide susceptibility mapping for the 2005 kashmir earthquake region abstract the m w 7 6 october 8 2005 kashmir earthquake triggered several thousand landslides throughout the himalaya of northern pakistan and india these were concentrated in six different geomorphic geologic anthropogenic settings a spatial database which included 2252 landslides was developed and analyzed using aster satellite imagery and geographical information system gis technology a multi criterion evaluation was applied to determine the significance of event controlling parameters in triggering the landslides the parameters included lithology faults slope gradient slope aspect elevation land cover rivers and roads the results showed four classes of landslide susceptibility furthermore they indicated that lithology had the strongest influence on landsliding particularly when the rock is highly fractured such as in shale slate clastic sediments and limestone and dolomite moreover the proximity of the landslides to faults rivers and roads was also an important factor in helping to initiate failures in addition landslides occurred particularly in moderate elevations on south facing slopes shrub land grassland and also agricultural land were highly susceptible to failures while forested slopes had few landslides one third of the study area was highly or very highly susceptible to future landsliding and requires immediate mitigation action the rest of the region had a low or moderate susceptibility to landsliding and remains relatively stable this study supports the view that 1 earthquake triggered landslides are concentrated in specific zones associated with event controlling parameters and 2 in the western himalaya deforestation and road construction contributed significantly to landsliding during and shortly after earthquakes

properties of debris flow deposits and source materials compared implications for debris flow characterization in the alps debris flow deposits generally contain 5 clay size particles and the role of the surface charged 2 mu m particles is often neglected although these particles may have a significant impact on the rheological properties of the interstitial fluid the objective of this study was to compare debris flow deposits and parent materials from two neighbouring catchments of the swiss alps with special emphasis on the colloidal constituents the catchments are small in area 4 km 2 2 5 km long similar in morphology but different in geology the average slopes are 35 40 the catchments were monitored for debris flow events and mapped for surface aspect and erosion activity debris flow deposits and parent materials were sampled the clay and silt fractions extracted and the bulk density 2 mm fraction bulk density particle size distribution chemical composition cation exchange capacity cec and mineralogy analysed the results show that the deposits are similar to the parent screes in terms of chemical composition but differ in terms of i particle size distribution and ii mineralogy reactivity and density of the 2 mm fraction in this fraction compared with the parent materials the deposits show dense materials enriched in coarse monocrystalline particles of which the smallest and more reactive particles were leached the results suggest that deposit samples should not be considered as representative of source or flow materials particularly with respect to their physical properties

lithologic control of debris torrent occurrence a field based investigation into the frequency and magnitude of debris torrent systems reveals that lithology controls the spatial and temporal occurrence of debris torrents in the tsitika watershed vancouver island british columbia we identified 125 debris torrent systems in the watershed for half these basins we used dendrochronology historical air photographs and field surveys to estimate debris torrent frequency and magnitude for a 30 year period we find that the volcaniclastic half of the watershed contains more than twice as many debris torrent systems in which debris torrents occur over seven times more frequently and the deposits have a higher rate of delivery of sediment to the mainstem river than the intrusive half lithologic differences in weathering rates weathering product grain size and rock texture can explain the observed differences in debris torrent behaviour because debris torrents are the main sediment transport path from hilltop to valley bottom in the region these results confirm an important lithologic control on regional sediment transport while the exact numbers are uncertain we estimate that the sediment flux of volcaniclastic debris torrents in the watershed is five times higher than that of the intrusive debris torrents

conditions for generation of fire related debris flows capulin canyon new mexico comparisonoftheresponsesofthreedrainagebasinsburnedbythedomefireof1996innewmexicoisusedtoidentifythe hillslope channelandfirecharacteristicsthatindicateasusceptibilityspecificallytowildfire relateddebrisflow summer thunderstorms generated three distinct erosive responses from each of three basins the capulin canyon basin showed widespreaderosivesheetwashandrillingfromhillslopes andseverefloodingoccurredinthechannel thenorthtributary basin exhibited extensive erosion of the mineral soil to a depth of 5 cm and downslope movement of up to boulder sized material andatleastonedebrisflowoccurredinthechannel negligiblesurfacerunoffwasobservedinthesouthtributary basin thenegligiblesurfacerunoffobservedinthesouthtributarybasinisattributedtothelimitedextent andseverityof the fire in that basin the factors that best distinguish between debris flow producing and flood producing drainages are drainage basin morphology and lithology a rugged drainage basin morphology an average 12 per cent channel gradient andsteep roughhillslopescoupledwithcolluviumandsoilweatheredfromvolcaniclasticandvolcanicrockspromotedthe generation of debris flows a less rugged basin morphology an average gradient of 5 per cent and long smooth slopes mantled with pumice promoted flooding flood and debris flow responses were produced without the presence of waterrepellentsoils thecontinuityandseverityoftheburnmosaic theconditionoftheriparianvegetation theconditionofthe fibrous root mat accumulations of dry ravel and colluvial material in the channel and on hillslopes and past debris flow activity appearedtohavelittlebearingonthedistinctiveresponsesofthebasins publishedin2000byjohnwiley sons ltd

volumetric analysis and hydrologic characterization of a modern debris flow near yucca mountain nevada abstract on july 21 or 22 1984 debris flows triggered by rainfall occurred on the southern hillslope of jake ridge about 6 km east of the crest of yucca mountain nevada rain gages near jake ridge recorded 65 mm and 69 mm on july 21 and 20 mm and 17 mm on july 22 rates of rainfall intensity ranged up to 73 mm h on the twenty first and 15 mm h on the twenty second digital elevation models with 2 0 m grid node spacing measured from pre storm and post storm aerial stereo photographs were used to map hillslope erosion and the downslope distribution of debris volumetric calculations indicate that about 7040 m 3 of debris was redistributed on the 49 132 m 2 hillslope study area during the two day storm period about 4580 m 3 65 of the eroded sediment was deposited within the study area and the remaining 35 was deposited outside the study area in a short tributary to fortymile wash and in the wash itself the maximum and mean depths of erosion in the study area were about 1 8 m and 5 cm respectively the mean depths of erosion on the upper and middle hillslope were 27 cm and 4 cm respectively the mean depth of deposition on the lower hillslope was 16 cm analysis of the values of cumulative precipitation in the context of the precipitation frequency atlas of the national oceanic and atmospheric administration indicates that precipitation from the main storm on july 21 was more than double that expected on average once during a 100 year period the relations of precipitation intensity duration developed from data recorded at a nearby precipitation gage indicate a storm interval of 500 years or greater the amount of erosion caused by such a storm is primarily dependent on three variables storm intensity development of the drainage network on the hillslope and the amount of available colluvium additionally the erosive ability of successive storms of equal intensity will decrease because such storms would tend to progressively isolate and reduce the amount of colluvium available the preservation of pleistocene deposits on hillslopes of yucca mountain in general indicates that erosional events that strip 5 of the available hillslope colluvium must be quite rare we conclude that the recurrence interval of an erosional event comparable to the july 1984 event is probably much longer than 500 years

coherent doppler profiler measurements of near bed suspended sediment fluxes and the influence of bed forms 1 this paper reports on remote acoustic observations of vertical turbulence intensity and vertical suspended sediment flux profiles on a planar beach in 3 4 m water depth the measurements of suspended sediment concentration and velocity are colocated and simultaneous and extend through the wave bottom boundary layer to the bed with 0 7 cm vertical resolution normalized cospectra of the suspended sediment flux and the vertical velocity for different bed states irregular ripples cross ripples linear transition ripples and flat bed indicate a small but significant peak at incident wave frequencies but are otherwise rather flat with weak redness estimates of the vertical flux components indicate a general balance between upward fluxes due to waves and turbulence and downward settling two exceptions to this balance are found immediately above the bed and for nonmigrating irregular ripples the contribution from the high frequency turbulent component is small wave phase averages for low energy bed states exhibit near bed peaks in the suspended sediment flux following wave phase reversal wave phase averages for the high energy cases do not exhibit a diffusive signature observed vertical profiles of turbulence intensity for different bed states reveal that the near bed turbulence levels are relatively independent of bed state friction velocity predictions from presently available models including a bed stress model and a sediment eddy diffusion model are compared to measured values of near bed turbulence intensity reasonable agreement is found between measured and predicted bottom friction velocities when wave friction factors from tolman 1994 are used

frost weathering and rockwall erosion in the southeastern swiss alps long term 1994 2006 observations abstract rates and processes of frost weathering in the alps were investigated by visual observations of intensively shattered rocks continuous monitoring of frost wedging and rock temperatures in bedrock and measurements of rockfall activity rapid frost weathering of hard intact rocks occurs along lakes and streams where seasonal freezing promotes ice segregation in the rock otherwise rocks require pre existing weakness or a long exposure period for intensively shattered automated monitoring shows that crack opening occurs at three scales including small opening accompanying short term frost cycles slightly larger movements during seasonal freezing and occasional large opening originating from refreezing of snow melt water during seasonal thawing the opening events require at least partial water saturation in the crack the repetition of crack opening frost wedging results in permanent opening and finally debris dislocation debris collections below fractured rockwalls show that pebble falls occur at an average rate of about 0 1 mm a 1 with significant spatial and inter annual variations occasional large boulder falls significantly raise the rockwall erosion rates controlled by such factors as the joint distribution in the bedrock repetition of annual freeze thaw cycles and extraordinary summer thaw

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

sediment concentration changes in runoff pathways from a forest road network and the resultant spatial pattern of catchment connectivity hydrological connectivity is a term often used to describe the internal linkages between runoff and sediment generation in upper parts of catchments and the receiving waters in this paper we identify two types of connectivity direct connectivity via new channels or gullies and diffuse connectivity as surface runoff reaches the stream network via overland flow pathways using a forest road network as an example of a landscape element with a high runoff source strength we demonstrate the spatial distribution of these two types of linkages in a 57 km 2 catchment in southeastern australia field surveys and empirical modelling indicate that direct connectivity occurs primarily due to gully development at road culverts where the average sediment transport distance is 89 m below the road outlet the majority of road outlets were characterised by dispersive flow pathways where the maximum potential sediment transport distance is measured as the available hillslope length below the road outlet this length has a mean value of 120 m for this catchment reductions in sediment concentration in runoff plumes from both pathways are modelled using an exponential decay function and data derived from large rainfall simulator experiments in the catchment the concept of the volume to breakthrough is used to model the potential delivery of runoff from dispersive pathways of the surveyed road drains n 218 only 11 are predicted to deliver runoff to a stream and the greatest contributor of runoff occurs at a stream crossing where a road segment discharges directly into the stream the methodology described here can be used to assess the spatial distribution and likely impact of dispersive and gullied pathways on in stream water quality 2005 elsevier b v all rights reserved