an examination of controls on debris flow mobility evidence from coastal british columbia we characterize and consider controls to runout distance of debris slides and debris flows using 1700 field observations supplemented by air photograph interpretation from coastal british columbia we examine the role of slope on deposition and scour and determine that they occur on steeper and flatter slopes respectively than previously reported mean net deposition occurred on slopes between 18 and 24 for open slope failures and between 12 and 15 for channelized debris flows we demonstrate a practical method for estimating both entrainment and runout in the field and in a gis and provide an example entrainment map for vancouver island british columbia we consider other controls to post failure landslide mobility including the role of gullies and stream channels roads and benches and intact forests shallow landslides that hit streams and gullies at acute angles had a high probability of transforming into a channelized debris flow whereas landslides that hit streams and gullies at obtuse angles did not forests played a substantial role in landslide runout debris flows travelling through a logged slope deposited much of their load when hitting a forest boundary and stopped entirely within 50 m of that boundary in 72 of the cases examined roads also tended to stop or reduce the size of open slope debris flows in 52 of the cases the results are expected to be useful to land management applications in regions with frequent shallow landsliding

evolution of the pelagonian carbonate platform complex and the adjacent oceanic realm in response to plate tectonic forcing late triassic and jurassic evvoia greece the late triassic and jurassic platform and the oceanic complexes in evvoia greece share a complementary plate tectonic evolution shallow marine carbonate deposition responded to changing rates of subsidence and uplift whilst the adjacent ocean underwent spreading and then convergence collision and finally obduction over the platform complex late triassic ocean spreading correlated with platform subsidence and the formation of a long persisting peritidal passive margin platform incipient drowning occurred from the sinemurian to the late middle jurassic this subsidence correlated with intra oceanic subduction and plate convergence that led to supra subduction calc alkaline magmatism and the formation of a primitive volcanic arc during the middle jurassic plate collision caused arc uplift above the carbonate compensation depth ccd in the oceanic realm and related thrust faulting on the platform led to sub aerial exposures patch reefs developed there during the late oxfordian to kimmeridgian advanced oceanic nappe loading caused platform drowning below the ccd during the tithonian which is documented by intercalations of reefal turbidites with non carbonate radiolarites radiolarites and bypass turbidites consisting of siliciclastic greywacke terminate the platform succession beneath the emplaced oceanic nappe during late tithonian to valanginian time

origin and emplacement of an inferred late jurassic subduction accretion complex euboea eastern greece in northern euboea central eastern greece an up to 3 km thick polygenetic melange pagondas complex is structurally interleaved between a triassic jurassic carbonate platform pelagonian zone and an overriding harzburgitic ophiolite the melange mainly comprises late triassic shallow water limestone and calciturbidites radiolarites triassic jurassic tholeiites alkaline basalts and minor andesites the units concerned range from kilometre sized thrust sheets and detached blocks to broken formation and structureless or bedded matrix supported conglomerates diamictite the melange includes remnants of neotethyan oceanic lithosphere overlain by radiolarites hemipelagic carbonates and distal calciturbidites derived from a mesozoic carbonate platform tholeiites were erupted at a triassic jurassic spreading axis whilst within plate type alkali basalts are interpreted mainly as seamounts kilometre scale detached blocks of shallow water coralline limestone are identified as collapsed atolls formed within an ocean and or along the rifted continental margin volcaniclastic sediments are locally interbedded with radiolarite and reflect post volcanic erosion of the ocean floor intra oceanic convergence began apparently in late early jurassic time giving rise to the euboea ophiolite above an inferred westwards dipping subduction zone the pagondas complex then developed as an accretionary prism the subduction trench later collided with the pelagonian passive margin driving the hot euobea ophiolite over the accretionary complex to produce amphibolites and greenschists of the metamorphic sole trench margin collision then drove the entire supra subduction zone complex apparently eastwards downflexing the pelagonian carbonate platform to form a foredeep in which late jurassic kimmeridgian tithonian radiolarian sediments accumulated during emplacement the accretionary complex was disrupted and partly resedimented as debris flows turbiditic volcaniclastic sandstone and shale in a foredeep or foreland basin setting

the significance of channel recharge rates for estimating debris flow magnitude and frequency the quantification of debris flow hazard requires estimates of debris flow frequency and magnitude several methods have been proposed to determine the probable volume of future debris flows from a given basin but most have neglected to account for debris recharge rates over time which may lead to underestimation of debris flow volumes in basins with rare debris flows this paper deals with the determination of debris recharge rates in debris flow channels based on knowledge of debris storage and the elapsed time since the last debris flow data are obtained from coastal british columbia and a relation is obtained across a sample of basins with similar terrain and climatic conditions for rennell sound on the west coast of the queen charlotte islands the power law relation for area normalized recharge rate rt versus elapsed time te was rt 0 23te 0 58 with an explained variance of 75 per cent a difference in recharge rates may exist between creeks in logged and unlogged forested terrain the power function for undisturbed terrain was rt 0 20te 0 49 while the function for logged areas was rt 0 30te 0 77 this result suggests that for the same elapsed time since the last debris flow clearcut gullies tend to recharge at a slower rate than creeks in old growth forest this finding requires verification particularly for longer elapsed times since debris flow but would have important implications for forest resource management in steep coastal terrain this study demonstrates that commonly used encounter probability equations are inappropriate for recharge limited debris flow channels copyright 2005 john wiley sons ltd

evidence for neotethys rooted within the vardar suture zone from the voras massif northernmost greece abstract three conflicting models are currently proposed for the location and tectonic setting of the eurasian continental margin and adjacent tethys ocean in the balkan region during mesozoic early tertiary time model 1 places the eurasian margin within the rhodope zone relatively close to the moesian platform a tethyan oceanic basin was located to the south bordering a large serbo pelagonian microcontinent model 2 correlates an integral serbo pelagonian continental unit with the eurasian margin and locates the tethys further southwest model 3 envisages the pelagonian zone and the serbo macedonian zone as conjugate continental units separated by a tethyan ocean that was sutured in early tertiary time to create the vardar zone of northern greece and former yugoslavia these published alternatives are tested in this paper based on a study of the tectono stratigraphy of a completely exposed transect located in the voras mountains of northernmost greece the outcrop extends across the vardar zone from the pelagonian zone in the west to the serbo macedonian zone in the east within the voras massif six east dipping imbricate thrust sheets are recognised of these units 1 4 correlate with the regional pelagonian zone in the west and related almopias sub zone by contrast units 5 6 show a contrasting tectono stratigraphy and correlate with the paikon massif and the serbo macedonian zone to the east these units form a stack of thrust sheets with unit 1 at the base and unit 6 at the top unstacking these thrust sheets places ophiolitic units between the pelagonian zone and the serbo macedonian zone as in model 3 additional implications are first that the paikon massif cannot be seen as a window of pelagonian basement as in model 1 and secondly jurassic andesitic volcanics of the paikon massif locally preserve a gneissose continental basement ruling out a recently suggested origin as an intra oceanic arc we envisage that the almopias vardar ocean rifted in triassic time followed by seafloor spreading the almopias ocean was consumed beneath the serbo macedonian margin in jurassic time generating subduction related arc volcanism in the paikon massif and related units ophiolites were emplaced onto the pelagonian margin in the west and covered by late jurassic pre kimmeridgian conglomerates other ophiolitic rocks formed within the vardar zone ano garefi ophiolite unit 4 in latest jurassic early cretaceous time and were not deformed until early tertiary time the vardar zone finally sutured in the early tertiary creating the present imbricate thrust structure of the voras mountains

mirdita zone ophiolites and associated sediments in albania reveal neotethys ocean origin the mirdita ophiolite zone in albania is associated with widespread melanges containing components of up to nappe size we dated matrix and components of the melange by radiolarians conodonts and other taxa the components consist of radiolarites pelagic limestones and shallow water limestones all of triassic age as well as ophiolites triassic radiolarite as a primary cover of ophiolite material proves middle triassic onset of mirdita ocean floor formation the melange contains a turbiditic radiolarite rich matrix radiolaritic flysch dated as late bajocian to early oxfordian it formed as a synorogenic sediment during west directed thrusting of ophiolite and sediment cover nappes representing ocean floor and underplated fragments of the western continental margin the tectonic structures formed during these orogenic events younger kimmeridian or eohellenic orogeny are sealed by late jurassic platform carbonates the geological history conforms with that of the inner dinarides and adjoining areas we therefore correlate the mirdita pindos ophiolite zone with the vardar zone and explain its present position by far distance west directed thrusting

a novel dynamic impact pressure model of debris flows and its application on reliability analysis of the rock mass surrounding tunnels abstract assessing the influence of the impact pressure exerted on surrounding rock mass by potential debris flows is one of the challenges in a mountain tunnel construction project this paper proposes an effective mathematical model for the assessment of impact pressure exerted by debris flows on obstacles the characteristics of the new model are analyzed and the parameters determination method for the new model are deduced also a new method for dynamic reliability analysis of the rock mass surrounding tunnels is proposed and is constituted into three key steps first by inputting impact pressure of debris flows generated by the aforementioned new model the flac3d is used as the dynamic analysis engine to obtain the time varying stress distribution of surrounding rock mass during the impact of debris flow second the factor of safety fos contours of surrounding rock mass are generated based on element states using the maximum tensile stress criterion and the mohr coulomb yield criterion third by using the time varying contours of the fos a failure probability and a reliability index are obtained from a reliability perspective a case study shows the complete analysis process and confirms the effectiveness of the above methodology in sum this paper provides new ideas new methods and a reference example for evaluating the influence of dynamic impact exerted by debris flows on the rock mass surrounding tunnels

effects of check dams on bed load transport and steep slope stream morphodynamics abstract check dams are transversal structures built across morphologically active streams in mountainous regions these structures have been used widely in torrent hazard mitigation for over 150 years thousands of them are regularly maintained by stream managers and torrent control services the stabilization role of these structures is well known i e they durably constrain the stream bed through the creation of vertical and planar fixed points what is not yet clear is to what extent check dams influence bed load transport how do peak solid discharge or flood transported volume change when check dams are added to a reach to address these questions long lasting small scale experiments were conducted in a 4 8 m long flume with either one three or no structures the results show that the addition of structures creates independent compartments in the bed level which have a strong influence on bed surface armouring and stream morphodynamics the consequence is that instantaneous transport intensities are unchanged but peak solid discharge occur more often and for shorter duration this results in the same total transported volume over the long term but reduced volume for a single transport event it reaffirms the observation of pioneering authors of the mid 19th and early 20th century who conceptualized the possible sediment transport regulation function of check dams in addition to stabilizing the stream bed check dams influence bed load transport through a buffering effect releasing frequently and in small doses what in their absence would be transported abruptly en masse during rare extreme events

a physics based model to derive rainfall intensity duration threshold for debris flow a statistical method to establish an intensity duration curve i d curve for debris flows is highly dependent on a large amount of debris flows and rainfall events and is impossible for a gully lacking observation data to overcome this limitation a physics based model to derive the i d curve is presented in this new model the density of the debris flow is chosen as the key parameter based on which the rainfall intensity and duration necessary for fitting i d curve are obtained the physical model is validated in jiangjia gully a typical debris flow valley with several debris flows each year a series of i d curves under the conditions of different antecedent rainfalls were fitted these derived curves are similar to the shape of the curve from the statistical method but having upper and lower boundary lines related to the necessary conditions for the occurrence of debris flows the precision of the new model is identified as about 80 5 using 63 collected rainfalls in jiangjia gully in yunan province china this value is 27 7 higher than the curve fitted through the statistical method this new physical model is capable of improving the deficiency of the statistical method and has great application potential for predicting debris flows

detection of surface change in complex topography using terrestrial laser scanning application to the illgraben debris flow channel detection of surface change is a fundamental task in geomorphology terrestrial laser scanners are increasingly used for monitoring surface change resulting from a variety of geomorphic processes as they allow the rapid generation of high resolution digital elevation models irrespective of instrument specifics survey design or data processing such data are subject to a finite level of ambiguity in position measurement a consideration of which must be taken into account when deriving change the propagation of errors is crucial in change detection because even very small uncertainties in elevation can produce large uncertainties in volume when extrapolated over an area of interest in this study we propose a methodology to detect surface change and to quantify the resultant volumetric errors in areas of complex topography such as channels where data from multiple scan stations must be combined we find that a commonly proposed source of error laser point elongation at low incidence angles has a negligible effect on the quality of the final registered point cloud instead ambiguities in elevation inherent to registered datasets have a strong effect on our ability to detect and measure surface change similarly we find that changes in surface roughness between surveys also reduce our ability to detect change explicit consideration of these ambiguities when propagated through to volume calculations allows us to detect volume change of 87 5m3 over an area of 4900m2 due to passage of a debris flow down a 300m reach of the illgraben channel in switzerland

mesozoic radiolarites accumulation as a function of sea surface fertility on tethyan margins and in ocean basins radiolarites commonly comprising chert shale couplets feature prominently in the mesozoic stratigraphy of the neotethyan realm the origin and significance of these deposits especially with regard to understanding palaeoproductivity in that region remains controversial this study examines transport processes and accumulation rates of radiolarians radiolarites as well as the chronology of radiolarite sedimentation based on revised data from the southern alps and new data from the balagne nappes alpine corsica results suggest that the spatio temporal distribution of carbonate and silica on tethyan margins was governed by extensive lateral transport of radiolarian tests from topographic highs to basins palaeoclimatic rather than palaeotectonic changes seem to have triggered changes in surface fertility which in turn brought about major facies changes observed in tethyan marginal basins regional platform demise possibly due to eutrophication and onset of radiolarite deposition in the early bajocian can be correlated with a positive shift in the carbon isotope curve whereas platform recovery and the end of radiolarite accumulation correlates with a gradual decline in 13c values the existence of a vigorous trans pangaean equatorial current system that could have produced regional upwelling is questioned because of evidence for middle jurassic to early cretaceous oligotrophic conditions in the proto caribbean and the central atlantic the caribbean river plume model is proposed as a possible alternative to upwelling in the jurassic western tethys dissolved nutrients may have been dispersed in low salinity lids that originated from river plumes of rivers from tropical africa and warm temperate eurasia vast areas of the pre late cretaceous world ocean must have accumulated radiolarites at low rates 50 myr radiolarite sections observed in many circumpacific terranes radiolarian chert and claystone could be the normal pelagic sediment during ordovician to early cretaceous time in far offshore open oceanic settings where dilution by terrigenous material and periplatform shallow water carbonates was absent

noaa atlas 3 the central north atlantic ocean basin and continental margins geology geophysics geochemistry and resources including the trans atlantic geotraverse tag

critical rainfall for typhoon induced debris flows in the western foothills taiwan abstract typhoon morakot devastated taiwan during august 6 11 2009 with a maximum total rainfall of 2884 mm causing 22 000 cases of slope failures rainfall thresholds for debris flow initiation are investigated using the hourly intensity vs duration i d hourly intensity vs cumulative rainfall i r and daily rainfall vs antecedent daily rainfall adr index methods among the 39 well documented cases 32 sites with known date and time of debris flow initiation were focused results reveal that debris flows and debris avalanches occur under a very wide range of rainfall characteristics with return periods ranging from several years to 200 years indicating that the empirical rainfall threshold alone is insufficient for an effective debris flow prediction system a consistent pattern of all i r paths for the investigated sites shows the combined effect of rainfall characteristics and inherent stability features of the slopes suggesting that the i r path is potentially useful in facilitating debris flow predictions it is also suggested that empirical rainfall thresholds should be calibrated using physical models against specific slope conditions to increase the accuracy of debris flow predictions

debris flow release processes investigated through the analysis of multi temporal lidar datasets in north western iceland debris flows are fast moving gravity flows of poorly sorted rock and soil mixed and saturated with water debris flow initiation has been studied using empirical and experimental modelling but the geomorphic changes indicative of different triggering processes are difficult to constrain with field observations only we identify signatures to distinguish two different debris flow release styles by integrating high resolution multi temporal remote sensing datasets and morphometric analysis we analyse debris flows sourced above the town of isafjor ur iceland two debris flow triggering processes were previously hypothesized for this site i slope failure characterised by landslides evolving into debris flows and ii the fire hose effect in which debris accumulated in pre existing steep sided bedrock passages is transported by a surge of water it is unknown which process dominates and determines the local risk to investigate this question we compare airborne lidar elevation models and aerial photographs collected in 2007 with similar data from 2013 we find that two new debris flow tracks were created by slope failures these are characterised by steep sliding surfaces and lateral leveed channels slope failure also occurred in two large recently active tracks creating the preparatory conditions for the fire hose effect to mobilise existing debris these tracks show alternating zones of fill and scour along their length and debris stored below the source area at rest angles 35 our approach allows us to identify and quantify the morphological changes produced by slope failure release process which generated the preparatory conditions for the fire hose effect as debris flows are rarely observed in action and morphological changes induced by them are difficult to detect and monitor the same approach could be applied to other landscapes to understand debris flow initiation in absence of other monitoring information and can improve the identification of zones at risk in inhabited areas near hillslopes with potential for debris flows

monitoring topographic changes through 4d structure from motion photogrammetry application to a debris flow channel the study of fast geomorphic changes in mountain channels and hillslopes driven by intense geomorphic processes requires frequent and detailed topographic surveys in the last two decades high resolution topography hrt has provided new opportunities in the earth sciences these have benefited from important developments in surveying techniques methods sensors and platforms between these the application of structure from motion sfm photogrammetry has become a widely used method to acquire hrt and high resolution orthomosaics at multiple temporal and spatial scales sfm photogrammetry has revolutionized the possibility to collect multi temporal hrt in rugged or inaccessible environments like that observed in debris flow catchments however appropriate workflows incorporating survey planning data acquisition post processing and error and uncertainty assessment are required especially when multi temporal surveys are compared to study topographic changes through time in this paper we present a workflow to acquire and process hrt the workflow was applied in a debris flow channel of the moscardo torrent eastern italian alps due to the topographic complexity of the study area the sfm surveys were carried out integrating photos obtained from an unmanned aerial vehicle and from the ground this integration guarantees high data density and avoids shadows eight photogrammetric surveys were collected between december 2015 and august 2017 in this time interval five debris flows occurred the surveying and data processing procedure described in the workflow permitted to summarize and integrate all the analysis steps and helped to identify and minimize potential sources of error in the multi temporal sfm data what we consider here 4d our case study demonstrates how the developed workflow presented here allows studying the geomorphic effects of debris flows and check dams functionality in mountain environments

defining phases of bedload transport using piecewise regression differences in the transport rate and size of bedload exist for varying levels of flow in coarse grained channels for gravel bed rivers at least two phases of bedload transport with notably differing qualities have been described in the literature phase i consists primarily of sand and small gravel moving at relatively low rates over a stable channel surface transport rates during phase ii are considerably greater than phase i and more coarse grains are moved including material from both the channel surface and subsurface transition from phase i to phase ii indicates initiation and transport of grains comprising the coarse surface layer common in steep mountain channels while the existence of different phases of transport is generally acknowledged the threshold between them is often poorly defined we present the results of the application of a piecewise regression analysis to data on bedload transport collected at 12 gravel bed channels in colorado and wyoming usa the piecewise regression recognizes the existence of different linear relationships over different ranges of discharge the inflection where the fitted functions intersect is interpreted as the point of transition from phase i to phase ii transport this is termed breakpoint a comparison of grain sizes moved during the two phases shows that coarse gravel is rarely trapped in the samplers during phase i transport indicating negligible movement of grains in this size range gravel larger than about d16 of the channel surface is more consistently trapped during phase ii transport the persistence of coarse gravel in bedload samples provides good evidence that conditions suitable for coarse grain transport have been reached even though the size of the sediment approaches the size limits of the sampler 76 mm in all cases a relative breakpoint rbr was defined by the ratio between the discharge at the breakpoint and the 1 5 year flow a surrogate for bankfull discharge expressed as a percentage the median value of rbr was about 80 percent suggesting that phase ii begins at about 80 percent of the bankfull discharge though the observed values of rbr ranged from about 60 to 100 percent variation in this value appears to be independent of drainage area median grain size sorting of bed materials and channel gradient at least for the range of parameters measured in 12 gravel bed channels data archive http dx doi org 10 2737 rds 2007 0003

hydrogeomorphic processes in a steep debris flow initiation zone 1 many debris flows initiate in steep channels 20 degrees yet studies have focused on lower gradient streams where failure is controlled by water height above channel deposits multiple debris flows in a steep channel in ohya landslide central japan were linked to infilling processes i e freeze thaw and dry ravel and partial saturation of accumulated sediment because of very active geomorphic processes in this catchment 39 debris flows were observed in the past 6 yr pre and post event imagery indicates selective transport of finer materials during most debris flows that comprise saturated and unsaturated flows however fluvial sediment processes important in relation to debris flow initiation in gentler channels were minimal critical conditions for the movement of such unsaturated materials are derived by equating shear stress with solid friction of the channel bed

wrenching in the external zone of the betic cordilleras southern spain abstract regional structural trends in the caravaca huescar area forming the central part of the external zone in the betic cordilleras indicate that deformation of the area results from right lateral wrenching subparallel to the paleogeographic zonation the structural trends do not fit the nappe interpretation generally used elsewhere in the external zone arguments for wrenching in the area are the structural inverse symmetry with respect to a central transcurrent fault zone the crevillente fault zone the distributional pattern of stratigraphic anomalies and types of deformation and the outcrop pattern of the paleogeographic zones it is argued that certain tectonic units in the area formerly interpreted as klippes in a nappe configuration form centers of flower structures and are vertically squeezed out blocks a theoretical model is sketched illustrating the evolution of a wrench zone under the stratigraphic conditions of the studied area and resulting in its present characteristics many of the features of the caravaca huescar area are also present elsewhere in the external zone and support the idea that wrenching was a major deformational mechanism it is therefore suggested that the external zone should in general not be described in terms of a nappe structure as has been done so far but in terms of a strike slip orogen or a wrenched continental margin

estimation of debris flow magnitude in the eastern italian alps the estimation of debris ow magnitude is an essential step in the assessment of debris ow hazard although different methods have been developed for the assessment of debris ow magnitude this is still a dif cult task because of the complexity of ow processes and the lack of data to test estimation procedures in many mountainous regions data on debris ow magnitude from 127 basins in the eastern italian alps have been collected from scienti c and technical journals technical reports historical documents gathered from local archives and eld surveys these data were used to develop and test different predictive approaches encompassing regression equations geomorphological surveys and probabilistic analysis of time series regression techniques were used to correlate debris ow magnitude to morphometric parameters and geological characteristics of the basins values of the channel debris yield rate contribution per unit length of channel proposed in the literature were compared with data from the study area for identifying reference values for channel stretches of different morphological characteristics although limited to the few basins in which suf cient data were available the probabilistic analysis of time series of debris ow magnitude provides indications about the relations between magnitude and frequency of debris ows some observations about the capability and drawbacks of considered methods are presented and the combined use of different approaches for the estimation of debris ow magnitude is suggested copyright 2004 john wiley sons ltd

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

landsliding and sediment flux in the central swiss alps a photogrammetric study of the schimbrig landslide entlebuch abstract this study explores the effects of hillslope mass failure on the sediment flux in the waldemme drainage basin central swiss alps over decadal time scales this area is characterized by abundant landslides affecting principally flysch units and is therefore an important sediment source the analysis concentrates on the schimbrig landslide that potentially contributes up to 15 to the sediment budget of the waldemme drainage basin volumetric changes are quantified using high resolution elevation models that were extracted using digital photogrammetric techniques sediment discharge data were used to constrain the significance of the landslide for sediment flux in the channel network the temporal extent of the photogrammetric analysis ranges from 1962 to 1998 including an earth slide event in 1994 the analyses reveal that during periods of low slip rates of the landslide nearly all of the displaced sediments were eroded and supplied to the channel network in contrast during active periods only a fraction of the displaced landslide mass was exported to the trunk stream interestingly the 1994 earth slide event did not disturb the long term sediment discharge pattern of the channel network nor did it influence the sediment flux at a weekly scale however suspended sediment pulses correlate with higher than average precipitation events this was especially the case in august 2005 when a storm event 100 years return period triggered several debris flows and earth flows in the whole drainage basin and in the schimbrig area this storm did not result in a significant increase in the slip rates of the entire landslide s main body it is therefore proposed that debris flows and earth flows perform the connectivity between hillslope processes e g landsliding and the trunk stream during and between phases of landslide activity in this particular setting

erosion and mobility in granular collapse over sloping beds 1 we describe laboratory experiments of granular material flowing over an inclined plane covered by an erodible bed designed to mimic erosion processes of natural flows travelling over deposits built up by earlier events two controlling parameters are the inclination of the plane and the thickness of the erodible layer we show that erosion processes can increase the flow mobility i e runout over slopes with inclination close to the repose angle of the grains r by up to 40 even for very thin erodible beds erosion efficiency is shown to strongly depend on the slope of the topography entrainment begins to affect the flow at inclination angles exceeding a critical angle c r 2 runout distance increases almost linearly as a function of the thickness of the erodible bed suggesting that erosion is mainly supply dependent two regimes are observed during granular collapse a first spreading phase with high velocity followed by a slow thin flow provided either the slope or the thickness of the erodible bed is high enough surprisingly erosion affects the flow mostly during the deceleration phase and the slow regime the avalanche excavates the erodible layer immediately at the flow front waves are observed behind the front that help to remove grains from the erodible bed steep frontal surges are seen at high inclination angles over both rigid or erodible bed finally simple scaling laws are proposed making it possible to obtain a first estimate of the deposit and emplacement time of a granular collapse over a rigid or erodible inclined bed

morphology and sedimentology of a complex debris flow in a clay shale basin coupling morphological sedimentological and rheological studies to numerical simulations is of primary interest in defining debris flow hazard on alluvial fans in particular numerical runout models must be carefully calibrated by morphological observations this is particularly true in clay shale basins where hillslopes can provide a large quantity of poorly sorted solid materials to the torrent and thus change both the mechanics of the debris flow and its runout distance in this context a study has been completed on the faucon stream southeastern french alps with the objectives of 1 defining morphological and sedimentological characteristics of torrential watersheds located in clay shales and 2 evaluating through a case study the scouring potential of debris flows affecting a clay shale basin morphological surveys grain size distributions and petrographic analyses of the debris flow deposits demonstrate the granular character of the flow during the first hectometre and its muddy character from there to its terminus on the debris fan these observations and laboratory tests suggest that the contributing areas along the channel have supplied the bulk of the flow material copyright 2005 john wiley sons ltd

triggering threshold precipitation and soil hydrological characteristics of shallow landslides in granitic landscapes abstract sierra de gredos a mountain range in central spain is prone to the occurrence of shallow landslides which can transform into sediment laden flows as demonstrated by geomorphologic evidence the analyses of these complex processes require reliable design tools for predicting thresholds of triggering precipitation in order to assess the susceptibility characteristics in the sierra de gredos there is a lack of knowledge concerning how weathering mantle properties vary spatially and what effects these spatial patterns have on infiltration surface runoff and shallow subsurface flow in this context this paper is focused on the hydrogeomorphic characterization of a shallow landslide that occurred on december 17 1997 the generalized quasi dynamic model gqdm was implemented to approach the critical rainfall intensity set for different durations and to establish the intensity duration id threshold to this purpose field and laboratory methods such as seismic refraction tomography srt time domain reflectometry tdr and geotechnical tests were applied the use of these field investigations and their combination with the gqdm have allowed us to provide a detailed description of the behavior of the catchment and reproduce the pattern of instability generated by an intense storm which triggered the 1997 shallow landslide furthermore this threshold can be used as a predictive tool for hazard prevention

statistical approaches for the definition of landslide rainfall thresholds and their uncertainty using rain gauge and satellite data abstract models for forecasting rainfall induced landslides are mostly based on the identification of empirical rainfall thresholds obtained exploiting rain gauge data despite their increased availability satellite rainfall estimates are scarcely used for this purpose satellite data should be useful in ungauged and remote areas or should provide a significant spatial and temporal reference in gauged areas in this paper the analysis of the reliability of rainfall thresholds based on rainfall remote sensed and rain gauge data for the prediction of landslide occurrence is carried out to date the estimation of the uncertainty associated with the empirical rainfall thresholds is mostly based on a bootstrap resampling of the rainfall duration and the cumulated event rainfall pairs d e characterizing rainfall events responsible for past failures this estimation does not consider the measurement uncertainty associated with d and e in the paper we propose i a new automated procedure to reconstruct ed conditions responsible for the landslide triggering and their uncertainties and ii three new methods to identify rainfall threshold for the possible landslide occurrence exploiting rain gauge and satellite data in particular the proposed methods are based on least square ls quantile regression qr and nonlinear least square nls statistical approaches we applied the new procedure and methods to define empirical rainfall thresholds and their associated uncertainties in the umbria region central italy using both rain gauge measurements and satellite estimates we finally validated the thresholds and tested the effectiveness of the different threshold definition methods with independent landslide information the nls method among the others performed better in calculating thresholds in the full range of rainfall durations we found that the thresholds obtained from satellite data are lower than those obtained from rain gauge measurements this is in agreement with the literature where satellite rainfall data underestimate the ground rainfall registered by rain gauges

positive feedback and momentum growth during debris flow entrainment of wet bed sediment debris flows typically occur when intense rainfall or snowmelt triggers landslides or extensive erosion on steep debris mantled slopes the flows can then grow dramatically in size and speed as they entrain material from their beds and banks but the mechanism of this growth is unclear indeed momentum conservation implies that entrainment of static material should retard the motion of the flows if friction remains unchanged here we use data from large scale experiments to assess the entrainment of bed material by debris flows we find that entrainment is accompanied by increased flow momentum and speed only if large positive pore pressures develop in wet bed sediments as the sediments are overridden by debris flows the increased pore pressure facilitates progressive scour of the bed reduces basal friction and instigates positive feedback that causes flow speed mass and momentum to increase if dryer bed sediment is entrained however the feedback becomes negative and flow momentum declines we infer that analogous feedbacks could operate in other types of gravity driven mass flow that interact with erodible beds the mechanisms by which debris flows acquire mass and momentum as they entrain material are unclear large scale experiments suggest that the pore pressure of wet bed sediment increases as the flow moves over the bed leading to reduced friction and progressive scouring of the base

cretaceous paleogene tectonics of the pelagonian zone inferences from skopelos island greece we have investigated subduction exhumation processes in the pelagonian zone exposed on the northern sporades islands aegean sea related to successive episodes of ocean continent and continent continent convergence through integrating multiscale structural analysis metamorphic petrology and white mica 40ar 39ar dating two major progressive phases of ductile deformation are documented which are related to distinct episodes of tectonic burial and exhumation of the pelagonian continental margin which was facing the neotethys vardar ocean review of existing data sets from neighboring regions shows that both deformation phases can be correlated along strike up to the dinarides the first phase of tectonic burial and exhumation d1 is characterized by nw se tectonic transport greenschist facies metamorphism and early cretaceous 105 135ma 40ar 39 ar white mica single fusion ages d1 is correlated with the initial closure of the vardar ocean by top to the w to nw ophiolite obduction and the underthrusting of the pelagonian margin below the oceanic upper plate underthrusting was followed by exhumation and the deposition of late cretaceous paleogene sediments the second phase of burial and exhumation d2 is characterized by ne sw tectonic transport greenschist to blueschist facies metamorphism and latest cretaceous early eocene 40ar 39 ar white mica ages of s2 fabrics top to the sw shearing is correlated with the tectonic burial of the pelagonian zone below the eurasian continent rhodopia while top to the ne shearing is attributed to subsequent extensional exhumation d2 fabrics record low grade p t conditions suggesting that the decoupled cover formations exposed on skopelos were incorporated in an accretionary wedge that formed above the subducting pelagonian basement during paleogene times

ten years of debris flow monitoring in the moscardo torrent italian alps abstract field data on debris flows are of utmost importance for improving knowledge of these hazardous phenomena and for the development of attenuation measures in alpine basins debris flows generally occur with a frequency high enough to create serious risk to human settlements and transportation routes but too low to justify monitoring activity capable of providing enough data in a sufficiently short time the moscardo torrent a small stream in the eastern italian alps is an exception to this general situation since it displays a high frequency of debris flows commonly at least one event per year in 1989 this torrent was instrumented and the results of the following 10 years 1989 1998 of debris flow monitoring are presented with an analysis of collected data the equipment installed allowed measurement of rainfall flow stage and ground vibrations caused by debris flows other important debris flow variables that is mean front velocity peak discharge and flowing volume were estimated from instrumental records video pictures have proved to be useful for the visual interpretation of debris flow waves and have made it possible to estimate the surface velocity of debris flows recorded data are compared with other experimental data sets collected and documented worldwide advantages and shortcomings of different types of sensors are discussed with relevance both for research monitoring purposes and for possible use in debris flow warning systems

scaling relationships between bed load volumes transport distances and stream power in steep mountain channels bed load transport during storm events is both an agent of geomorphic change and a significant natural hazard in mountain regions thus predicting bed load transport is a central challenge in fluvial geomorphology and natural hazard risk assessment bed load transport during storm events depends on the width and depth of bed scour as well as the transport distances of individual sediment grains we traced individual gravels in two steep mountain streams the erlenbach switzerland and rio cordon italy using magnetic and radio frequency identification tags and measured their bed load transport rates using calibrated geophone bed load sensors in the erlenbach and a bed load trap in the rio cordon tracer transport distances and bed load volumes exhibited approximate power law scaling with both the peak stream power and the cumulative stream energy of individual hydrologic events bed load volumes scaled much more steeply with peak stream power and cumulative stream energy than tracer transport distances did and bed load volumes scaled as roughly the third power of transport distances these observations imply that large bed load transport events become large primarily by scouring the bed deeper and wider and only secondarily by transporting the mobilized sediment farther using the sediment continuity equation we can estimate the mean effective thickness of the actively transported layer averaged over the entire channel width and the duration of individual flow events this active layer thickness also followed approximate power law scaling with peak streampower and cumulative stream energy and ranged up to 0 57min the erlenbach broadly consistent with independent measurements

spatial estimation of debris flows triggering rainfall and its dependence on rainfall return period abstract forecasting the occurrence of debris flows is fundamental for issuing hazard warnings and often focuses on rainfall as a triggering agent and on the use of empirical rainfall thresholds based on rain gauge observations a recognized component of the uncertainty associated with the use of rainfall thresholds is related to the sampling of strongly varying rainfall variability with sparse rain gauge networks in this work we examine the spatial distribution of rainfall depth in areas up to 10 km from the debris flow initiation points as a function of return period and we exploit this information to analyze the errors expected in the estimation of debris flow triggering rainfall when rain gauge data are used in particular we investigate the impact of rain gauge density and of the use of different interpolation methods high resolution adjusted radar rainfall estimates representing the best available spatially distributed rainfall estimates at the debris flows initiation point and in the surrounding area are sampled by stochastically generated rain gauge networks characterized by varying densities debris flow triggering rainfall is estimated by means of three rainfall interpolation methods nearest neighbor inverse distance weighting and ordinary kriging on average triggering rainfall shows a local peak corresponding to the debris flow initiation point with a decay of rainfall with distance which increases with the return period of the triggering rainfall interpolation of the stochastically generated rain gauge measurements leads to an underestimation of the triggering rainfall that irrespective of the interpolation methods increases with the return period and decreases with the rain gauge density for small return period events and high rain gauge density the differences among the methods are minor with increasing the return period and decreasing the rain gauge density the nearest neighbor method is less biased because it makes use only of the closest rain gauge to the debris flow initiation point on the contrary inverse distance weighting and ordinary kriging which are using rain gauges located farther from the debris flows in addition to the closest one exhibit negative biases that increase with return period the standard deviation of the interpolated values is larger when the nearest neighbor is used with respect to inverse distance weighting and ordinary kriging for large return period and low rain gauge density the differences among the methods are minor

carbonate platform evidence of ocean acidification at the onset of the early toarcian oceanic anoxic event abstract the early toarcian oceanic anoxic event early jurassic 183 myr ago is associated with one of the largest negative carbon isotope excursion cie in the whole phanerozoic 3 7 estimates of the magnitude and rate of co 2 injection in the ocean atmosphere system are compatible with a scenario of ocean acidification many carbonate platforms drowned in the pliensbachian well before the early toarcian event in this paper we test the hypothesis of surface water ocean acidification by presenting data from a resilient carbonate platform the apennine carbonate platform of southern italy the studied sections document a dramatic shift of the carbonate factory from massive biocalcification to chemical precipitation lithiotis bivalves and calcareous algae palaeodasycladus mediterraneus which were the most prolific carbonate producers of pliensbachian carbonate platforms disappear during the first phase of the early toarcian cie before the most depleted values are reached we discuss the local versus supraregional significance of this shift and propose a scenario involving abrupt decline of carbonate saturation forced by co 2 release at the beginning of the early toarcian cie followed by a calcification overshoot driven by the recovery of ocean alkalinity attribution of the demise of carbonate platform hypercalcifiers to ocean acidification is supported by palaeophysiology and reinforced by experimental data on the detrimental effects of ocean acidification on recent shellfishes and calcareous algae

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

geodynamic evolution of ophiolites from albania and greece dinaric hellenic belt one two or more oceanic basins all the geological constraints for an exhaustive reconstruction of the triassic to tertiary tectonic history of the southern dinaric hellenic belt can be found in albania and greece this article aims to schematically reconstruct this long tectonic evolution primarily based on a detailed analysis of the tectonic setting the stratigraphy the geochemistry and the age of the ophiolites in contrast to what was previously reported in the literature we propose a new subdivision on a regional scale of the ophiolite complexes cropping out in albania and greece this new subdivision includes six types of ophiolite occurrences each corresponding to different tectonic units derived from a single obducted sheet these units are represented by 1 sub ophiolite melange 2 triassic ocean floor ophiolites 3 metamorphic soles 4 jurassic fore arc ophiolites 5 jurassic intra oceanic arc ophiolites and 6 jurassic back arc basin ophiolites the overall features of these ophiolites are coherent with the existence of a single though composite oceanic basin located east of the adria pelagonian continental margin this oceanic basin was originated during the middle triassic and was subsequently early jurassic affected by an east dipping intra oceanic subduction this subduction was responsible for the birth of intra oceanic arc and back arc oceanic basins separated by a continental volcanic arc during the early to middle jurassic from the uppermost middle jurassic to the early cretaceous an obduction developed during which the ophiolites were thrust westwards firstly onto the neighboring oceanic lithosphere and then onto the adria margin

channel scour and fill by debris flows and bedload transport abstract in steep channels debris flows are known to dramatically increase in volume under the effect of channel erosion however the critical factors controlling channel erosion by debris flows are not well documented by field studies this is particularly true for the effect of slope on the depth at which erodible beds are scoured during debris flows and during bedload transport this topic has been addressed by intensive cross section resurveys 54 cross sections of debris flows n 5 and flow events n 9 that occurred in two torrents of the french prealps the manival and real torrents between 2009 and 2012 this study provided evidence that debris flow scouring increases with slope whereas this is not the case for bedload transport no slope effect detected during floods a functional relationship defined from a piecewise regression model is proposed as an empirical fit for the prediction of channel erosion by debris flows with a critical slope threshold at 0 19 95 confidence interval 0 17 0 21 this slope threshold is interpreted as the transition between the transport limited and supply limited regimes associated with the upstream decreasing erodible bed thickness the erodible bed was also characterized by quantifying erosion deposition and surface roughness with multidate terrestrial laser scans tlss in a short reach of high sensitivity of the manival torrent debris flow erosion occurred preferentially on smooth surfaces corresponding to the unconsolidated gravel deposits from bedload transport a 20 cm resolution roughness profile from an airborne laser scan als and a slope profile of the whole channel were used to detect the unconsolidated sediment deposits that can potentially feed future debris flows

high frequency monitoring of debris flow propagation along the real torrent southern french prealps abstract the real torrent 2 3 km2 drainage area is a very active debris flow torrent in the french prealps it was equipped with three high frequency monitoring stations in late 2010 to investigate the triggering conditions and propagation of debris flows along the 2 km long torrent channel the monitoring system combines different techniques including rain gauges and measurements of ground vibrations and flow elevations in spring and summer of 2011 five rainfall triggered debris flow events occurred along the torrent most debris fronts deposited in the upstream part of the channel but one large front 1 9 2 0 m high propagated to the catchment outlet with a mean velocity of about 3 m s 1 the volume of this main debris surge was 3900 m3 near the hillslope sources and increased downstream 5500 m3 in the middle part and 8600 m3 near the catchment outlet the debris flow developed a more mature flow pattern as it progressed downstream multiple debris and hyperconcentrated surges were observed upstream while a single debris surge occurred near the catchment outlet the front height remained relatively constant during its propagation whereas its viscosity and velocity tended to decrease downstream as the channel slope decreases the growth of this main debris surge could be explained by the entrainment of in channel sediments and the coalescence of the multiple preliminary surges for the 2011 events rainfall burst duration and intensity were the main factors controlling the occurrence volume and runout distance of debris flows antecedent channel conditions sediment recharge bed wetness and antecedent rainfall are also important factors but further investigations are necessary to better understand the role of these factors regarding the triggering and propagation of debris flows in the real torrent

real time measurement and preliminary analysis of debris flow impact force at jiangjia ravine china impact forces associated with major debris flows jiangjia ravine china august 25 2004 were recorded in real time by a system consisting of three strain sensors installed at different flow depths this provides the first real time and long duration record of impact forces associated with debris flows a comprehensive approach including low pass filtering and moving average methods were used to preprocess the recorded signals the upper limit of impact frequency in the debris flows was estimated at 188 66 hz under the assumption that only coarse grains cause effective impact loadings thus a low pass filter with a 200 hz cut off frequency was needed to denoise the original data in order to extract the impact force then the moving average method was applied to separate long term and random components of the filtered data these were interpreted as respectively the fluid pressure and grain impact loading it was found that the peak grain impacts at different depths were non synchronous within the debris flows the impact loadings were far greater than and not proportional to the fluid pressures analysis of the impact force of 38 debris flow surges gives an empirical value for the ratio of the hydrodynamic pressure to the momentum flow density i e the product of debrisflow density and mean velocity square which provides a very valuable basis for understanding debris flow dynamics and designing debris flow management systems copyright c 2011 john wiley sons ltd

erratum to stratigraphy and tectonics of a time transgressive ophiolite obduction onto the eastern margin of the pelagonian platform from late bathonian until valanginian time exemplified in northern evvoia greece the obduction of an ophiolite sheet onto the eastern pelagonian carbonate platform complex of the hellenides began during the late bathonian and ended with the final emplacement of the ophiolite during valanginian time the early stages of obduction caused subaerial exposure of the platform recorded by an unconformity of callovian age which is marked by laterites overlying folded and faulted karstic substrates the laterites have distinct ophiolitic geochemical signatures indicating that emergent ophiolite had been undergoing lateritic weathering this unconformity coincides with widespread western tethyan callovian gaps indicating that the obduction in the hellenides was probably related to far reaching plate tectonic processes resumed gravitational pull and rollback of the subducted oceanic leading edge of the temporarily exposed ophiolite platform drowning continued into tithonian valanginian time documented initially by reefal carbonates and then by below ccd carbonate free radiolarian cherts and shales subsequently siliciclastic turbidites which apparently originated from uplifted variscan basement were deposited together with and over the radiolarite as the ophiolite nappe sheet advanced the nappe substrate underwent tectonic deformations of varying intensity while polymictic melange and syntectonic sedimentary debris accreted beneath the ophiolite and at the nappe front the provenience of the ophiolite nappe complexes of northern evvoia most probably has to be looked for in the vardar ocean

direct measurement of channel erosion by debris flows illgraben switzerland 1 the timing and magnitude of channel bed erosion by three debris flows was measured in 2008 at the illgraben catchment switzerland using a scour sensor which consisted of a vertical array of erodible sensor elements during the largest debris flow sediment was entrained progressively and stepwise at the flow head within 20 s after front arrival and onset of erosion started before maximum values for flow height and normal and shear stress measured nearby were reached erosion in one of the two smaller debris flows also occurred at the head of the flow but the magnitude of erosion was at the detection limit for the sensor for the other small debris flow we were not able to determine the timing of erosion due to the presence of a sediment layer covering the sensors measurements of pressure fluctuations along the channel sidewall which are produced by interparticle collisions within the flow indicate that the entrainment of sediment is coincident with the largest mean and fluctuating pressures suggesting that interparticle collisions may drive the erosion process at the front of debris flows after erosion at the head of the debris flows sediment was deposited on top of the erosion sensor columns indicating that the bed was reworked to a larger depth than directly visible at the surface after the event observations from elsewhere along the channel support our measurements of the magnitude of net debris flow erosion and indicate that significant erosion can be expected on debris fans when the flow is confined to a channel debris flow entrainment and subsequent bulking of the flow influence the flow dynamics and therefore should be considered in debris flow models and hazard assessment

a dominant tectonic signal in high frequency peritidal carbonate cycles a regional analysis of liassic platforms from western tethys abstract meter scale peritidal carbonate cycles are a common feature of the geological record but debate continues about what processes lead to their formation three conceptual models or a combination thereof are commonly invoked to explain cycle formation eustasy tectonics or autocyclicity these three models are tested with a large new dataset from different early jurassic plate margins from western tethys study of seven logged sections from spain italy greece tunisia morocco and gibraltar enables an analysis of the possible roles of local versus regional patterns and controls on cyclicity within a sinemurian time slice cycle types are diverse and include shallowing upward cycles parasequences but also deepening upward and diagenetic cycles high frequency sequences and subtidal cycles numbers of cycles per section and cycle stacking patterns within this time slice vary from section to section statistical tests runs tests time series and bundling all indicate random stacking of cycles within sections and an absence of any bundling of thicknesses or of facies trends assessment of cycle types by their occurrence and stacking patterns indicates little support for either eustasy or autocyclicity being the dominant cycle forming mechanism however the variability in numbers of cycles per section thickness variations of the sections cycle type variability and randomness of stacking patterns all favor a pulsed tectonic control for the creation and filling of accommodation space this conclusion is further supported by evidence that has largely arisen during the course of this study of syndepositional extensional tectonics in the sinemurian on these rifted tethyan margins although tectonics appears to be the dominant control superimposed eustasy and or autocyclic processes cannot be discounted

initiation conditions for debris flows generated by runoff at chalk cliffs central colorado abstract we have monitored initiation conditions for six debris flows between may 2004 and july 2006 in a 0 3 km 2 drainage basin at chalk cliffs a band of hydrothermally altered quartz monzonite in central colorado debris flows were initiated by water runoff from colluvium and bedrock that entrained sediment from rills and channels with slopes ranging from about 14 to 45 the availability of channel material is essentially unlimited because of thick channel fill and refilling following debris flows by rock fall and dry ravel processes rainfall exceeding i 6 61 d 0 77 where i is rainfall intensity mm h and d is duration h was required for the initiation of debris flows in the drainage basin the approximate minimum runoff discharge from the surface of bedrock required to initiate debris flows in the channels was 0 15 m 3 s colluvium in the basin was unsaturated immediately prior to antecedent and during debris flows antecedent volumetric moisture levels in colluvium at depths of 1 cm and 29 cm ranged from 4 9 and 4 7 respectively during debris flows peak moisture levels in colluvium at depths of 1 cm and 29 cm ranged from 10 20 and 4 12 respectively channel sediment at a depth of 45 cm was unsaturated before and during debris flows antecedent moisture ranged from 20 22 and peak moisture ranged from 24 38 although we have no measurements from shallow rill or channel sediment we infer that it was unsaturated before debris flows and saturated by surface water runoff during debris flows our results allow us to make the following general statements with regard to debris flows generated by runoff in semi arid to arid mountainous regions 1 high antecedent moisture levels in hillslope and channel sediment are not required for the initiation of debris flows by runoff 2 locations of entrainment of sediment by successive runoff events can vary within a basin as a function of variations in the thickness of existing channel fill and the rate of replenishment of channel fill by rock fall and dry ravel processes following debris flows and 3 rainfall and simulated surface water discharge thresholds can be useful in understanding and predicting debris flows generated by runoff and sediment entrainment

sediment entrainment by debris flows in situ measurements from the headwaters of a steep catchment 1 debris flows can dramatically increase their volume and hence their destructive potential by entraining sediment yet quantitative constraints on rates and mechanics of sediment entrainment by debris flows are limited using an in situ sensor network in the headwaters of a natural catchment we measured flow and bed properties during six erosive debris flow events despite similar flow properties and thicknesses of bed sediment entrained across all events time averaged entrainment rates were significantly faster for bed sediment that was saturated prior to flow arrival compared with rates for sediment that was dry bed sediment was entrained from the sediment surface downward in a progressive fashion and occurred during passage of dense granular fronts as well as water rich inter surge flow en massefailure of bed sediment along the sediment bedrock interface was never observed large magnitude high frequency fluctuations in total normal basal stress were dissipated within the upper 5 cm of bed sediment within this near surface layer concomitant fluctuations in coulomb frictional resistance are expected irrespective of the influence of pore fluid pressure or fluctuations in shear stress if the near surface sediment was wet as it was overridden by a flow additional large magnitude high frequency pore pressure fluctuations were measured in the near surface bed sediment these pore pressure fluctuations propagated to depth at subsonic rates and in a diffusive manner the depth to which large excess pore pressures propagated was typically less than 10 cm but scaled as d fi 0 5 in which d is the hydraulic diffusivity and fiis the frequency of a particular pore pressure fluctuation shallow penetration depths of granular normal stress fluctuations and excess pore pressures demonstrate that only near surface bed sediment experiences the full dynamic range of effective stress fluctuations and as a result can be more easily entrained than deeper sediment these data provide robust tests for mechanical models of entrainment and demonstrate that a debris flow over wet bed sediment will be larger than the same flow over dry bed sediment

evidence for jurassic subduction from the northern calcareous alps berchtesgaden austroalpine germany the closure of the western part of the neotethys ocean started in late early jurassic the middle to early late jurassic contraction is documented in the berchtesgaden alps by the migration of trench like basins formed in front of a propagating thrust belt due to ophiolite obduction these basins propagated from the outer shelf area hallstatt realm to the interior continent hauptdolomit dachstein platform realm the basins were separated by nappe fronts forming structural highs this scenario mirrors syn orogenic erosion and deposition in an evolving thrust belt active basin formation and nappe thrusting ended around the oxfordian kimmeridgian boundary followed by the onset of carbonate platforms on structural highs starved basins remained between the platforms rapid deepening around the early late tithonian boundary was induced by extension due to mountain uplift and resulted in the reconfiguration of the platforms and basins erosion of the uplifted nappe stack including obducted ophiolites resulted in increased sediment supply into the basins and final drowning and demise of the platforms in the berriasian the remaining early cretaceous foreland basins were filled up by sediments including siliciclastics the described jurassic to early cretaceous history of the northern calcareous alps accords with the history of the western carpathians the dinarides and the albanides where 1 age dating of the metamorphic soles prove late early to middle jurassic inneroceanic thrusting followed by late middle to early late jurassic ophiolite obduction 2 kimmeridgian to tithonian shallow water platforms formed on top of the obducted ophiolites and 3 latest jurassic to early cretaceous sediments show postorogenic character

combined roles of saturated permeability and rainfall characteristics on surficial failure of homogeneous soil slope abstract both rainfall characteristics rainfall intensity and duration and saturated permeability of soil may influence the type and mechanism of surficial slope failures in general the failures can be initiated by two mechanisms i e loss of matric suction through propagation of wetting front and rise of water table up to date there are still no clear indicators to identify the dominant parameters that control the type of failure for these shallow landslides this paper investigates the hydraulic responses of soils to the variations of rainfall characteristics and soil permeability through numerical analyses the results showed that the hydraulic responses to rainfall for a homogeneous infinite slope underlain by an impermeable layer can be divided into two stages 1 the propagation of wetting front and 2 the rise of water table based on these hydraulic responses the type and mechanism of failures were deduced from the analytical analyses both the rainfall characteristics and saturated permeability were found to be predominant in controlling the hydraulic responses of soil and hence the occurrence time depth of failure plane and type of surficial slope failures

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

a genetic classification of carbonate platforms based on their basinal and tectonic settings in the cenozoic abstract this paper reassesses the usefulness of the morphological classification of carbonate platforms into rimmed shelves and ramps whilst the existing classifications have value in describing platform margin morphology at any one time the terms rimmed shelf and ramp are less successful at categorising the entire morphology and stratigraphy of carbonate platforms research on cenozoic carbonate platforms from a range of different tectono stratigraphic settings indicates that the basinal and tectonic setting of a platform can be used to erect a first order genetic classification of carbonate platforms the basinal and tectonic setting of carbonate platforms is shown to control their occurrence the overall 3 d platform morphology the large scale stratigraphic features and depositional sequences climate ocean chemistry and biological evolution control grain types facies and some elements of platform margins but not the larger scale features considered in this new classification from a review of well exposed outcropping and seismically imaged cenozoic platforms it is proposed that eight types of carbonate platform can currently be recognised and characterised based on their basinal and tectonic setting fault block salt diapir subsiding margin offshore bank volcanic pedestal thrust top delta top and foreland margin carbonate platforms these eight types are described using information from cenozoic platforms worldwide and the controls on their development are discussed many platform types e g subsiding margin offshore bank salt diapir thrust top and foreland margin are typical of particular classes of sedimentary basins others e g fault block volcanic pedestal and delta top are more widespread in their occurrence and occur in a range of basin types the value of this classification is that it is genetic rather than morphological the classification reflects the entire morphology and large scale stratigraphy of the platform and the controls on its development in addition the platform models can be used to understand the details of less well exposed or seismically imaged platforms so that they can be characterised and understood in terms of tectono sedimentary processes conversely the classification also provides valuable information on basin evolution as carbonate platforms house information on palaeoenvironments sea level change and are sensitive recorders of the tectonic environment

low and high frequency sea level changes control peritidal carbonate cycles facies and dolomitization in the rock of gibraltar early jurassic iberian peninsula the rock of gibraltar comprises two tectonically separated limbs of an isolated klippe of liassic gibraltar limestone formation both limbs have similar c 400 m thick sequences of inner carbonate platform facies arranged in high frequency metre scale shallowing upward peritidal cycles with emergent caliche caps four cycle types are recognized on the basis of vertically repeated successions of different sedimentary structures lithologies facies and biota when compared with other liassic cycles from fault bound platforms of the western mediterranean region all are found to be of similar scale facies and cycle type likely common origins are through milankovitch band allocyclicity or autocyclic tidal flat progradation superimposed on regional subsidence within the gibraltar limestone high frequency cycles are superimposed on a low frequency third order cyclicity that is revealed through the use of fischer plots to control the occurrrence of facies biota high frequency cycle types and dolomitization falling sea level and lowstand phases with reduced accommodation space are typified by restricted inner platform facies and cycles and by early reflux dolomitization transgressive and highstand phases with more accommodation space are characterized by the absence of early dolomites the incoming of inner platform microfossils i e foraminifera and calcareous algae and by less restricted marine facies i e oncoids shelly rudstones packstones and grainstones fischer plots have demonstrable value in the correlation and analysis of tectonically separated and geographically isolated cyclic sequences that lack prominent marker beds or stratigraphically useful biotas

a new approach to estimating hazard posed by debris flows in the westfjords of iceland abstract the aim of this study is to improve the assessment of hazard posed by debris flows to the people and settlements of northwest iceland by studying very recent examples from above the town of isafjor ur and other nearby localities debris flows are a recognised hazard in the region above isafjor ur they occur with particularly high frequency and have appreciable volumes up to 14 000 m 3 we have used airborne laser altimeter lidar and differential global positioning system gps data to produce isopach maps of flows that occurred in 1999 2007 and 2008 our data show that these flows begin depositing at higher slope gradients and are also more mobile than hillslope debris flows reported by other authors above a 19 slope erosion is initiated independent of the distance along the flowpath using the isopach maps and associated field observations we have found a relationship between ground slope and patterns in deposition volume we have used this finding as a basis for an empirical model that enables an estimate of the total travel distance and final thickness of future debris flows to be calculated this has enabled us to identify areas of the town which are at risk some of these are not obvious without this analysis this model is notable for its simplicity which allows future debris flow characteristics to be predicted without the need to determine the precise fluid dynamic parameters of the flow such as viscosity and velocity which are required to implement more complex models

bed scour by debris flows experimental investigation of effects of debris flow composition debris flows can grow greatly in size by entrainment of bed material enhancing their runout and hazardous impact here we experimentally investigate the effects of debris flow composition on the amount and spatial patterns of bed scour and erosion downstream of a fixed to erodible bed transition the experimental debris flows were observed to entrain bed particles both grain by grain and en masse and the majority of entrainment was observed to occur during passage of the flow front the spatial bed scour patterns are highly variable but large scale patterns are largely similar over 22 5 35 channel slopes for debris flows of similar composition scour depth is generally largest slightly downstream of the fixed to erodible bed transition except for clay rich debris flows which cause a relatively uniform scour pattern the spatial variability in the scour depth decreases with increasing water gravel grain size and clay fraction basal scour depth increases with channel slope flow velocity flow depth discharge and shear stress in our experiments whereas there is no correlation with grain collisional stress the strongest correlation is between basal scour and shear stress and discharge there are substantial differences in the scour caused by different types of debris flows in general mean and maximum scour depths become larger with increasing water fraction and grain size and decrease with increasing clay content however the erodibility of coarse grained experimental debris flows gravel fraction 0 64 is similar on a wide range of channel slopes flow depths flow velocities discharges and shear stresses this probably relates to the relatively large influence of grain collisional stress to the total bed stress in these flows 30 50 the relative effect of grain collisional stress is low in the other experimental debris flows 5 causing erosion to be largely controlled by basal shear stress

carbonate platform response to the toarcian oceanic anoxic event in the southern hemisphere implications for climatic change and biotic platform demise abstract the toarcian oceanic anoxic event t oae 183 ma was a profound short term environmental perturbation associated with the large scale release of 13c depleted carbon into the global ocean atmosphere system which resulted in a significant negative carbon isotope excursion cie the general lack of characteristic t oae records outside of the northern hemisphere means that the precise environmental effects and significance of this event are uncertain many biotic carbonate platforms of the northern hemisphere western tethys drowned or shifted to non skeletal platforms during the early toarcian however southern hemisphere records of toarcian carbonate platforms are rare and thus the extent and significance of biotic platform demise during the t oae is unclear here we present high resolution geochemical and sedimentological data across two pliensbachian toarcian shallow water carbonate platform sections exposed in the tibetan himalaya these sections were located paleogeographically on the open southeastern tropical tethyan margin in the southern hemisphere the t oae in the tibetan himalaya is marked by a negative cie in organic matter our sedimentological analysis of the two sections reveals an abundance of storm deposits within the t oae interval which emphasizes a close link between warming and tropical storms during the t oae event in line with evidence recently provided from western tethyan sections of the northern hemisphere in addition our analysis also reveals extensive biotic carbonate platform demise by drowning or changing to non skeletal carbonates coincident with the onset of the cie taken together our results suggest that rapid and pervasive seawater warming in response to carbon release likely played a significant role in sudden biotic carbonate platform demise and suppression postponement of biotic platform re development along the whole tropical subtropical tethyan margin

maximum impact force of woody debris on floodplain structures we collided woody debris i e logs with structures using flume and test basin laboratory facilities to investigate the maximum impact force that floodplain structures are exposed to from floating woody debris the tests also investigated the influence of collision geometry determined by the debris orientation on impact on the maximum impact forces we reviewed the three approaches that represent the existing guidance for estimating maximum impact forces each approach estimates the maximum impact force based on the debris velocity and mass we show that all the existing approaches can be derived from a single degree of freedom model of the collision and can be considered to be equivalent the laboratory data show that the maximum impact force was associated with a log striking a rigid structure with its end oblique and eccentric collisions reduced the maximum impact load in a predictable and consistent manner the approach we refer to as contact stiffness a linear one degree of freedom model with no damping was able to reproduce the laboratory results over the entire range of data with an effective contact stiffness of 2 4 mn m

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

neotethyan evolution of eastern greece pagondas melange evia island inferred from radiolarian biostratigraphy and the geochemistry of associated extrusive rocks this paper presents new radiolarian biostratigraphic and igneous metamorphic geochemical data for a mesozoic volcanic sedimentary melange on the island of evia euboea or evvoia eastern greece this melange includes dismembered thrust sheets and blocks of radiolarian chert and basalt biostratigraphic age data show that radiolarites interbedded with basalt derived coarse clastic sediments near the base of a coherent succession were deposited in middle and late triassic time late ladinian carnian norian geochemical evidence shows that associated extrusive rocks of inferred triassic age range from enriched alkaline basalts to transitional basalts and more depleted mid ocean ridge type basalts amphibolite facies meta basalts from the metamorphic sole of the over riding evia ophiolite exhibit similar chemical compositions both the basalts and the meta basalts commonly show an apparent subduction related influence e g relative nb depletion that may have been inherited from a previous subduction event in the region the basalts are interpreted to have erupted during middle late triassic time late ladinian carnian related to initial opening of a neotethyan ocean basin adjacent to a rifted continental margin radiolarites located stratigraphically higher in the coherent succession studied are dated as middle jurassic late bathonian early callovian similar aged radiolarites are depositionally associated with ophiolitic rocks including boninites in some other areas of greece and albania during initial ocean basin closure bajocian bathonian the adjacent shallow water carbonate platform pelagonian zone disintegrated to form basins in which siliceous sediments were deposited and highs on which shallow water carbonates continued to accumulate this facies differentiation is seen as a response to crustal flexure as the neotethyan ocean began to close the over riding pagondas melange and other similar units in the region are interpreted as accretionary prisms related to subduction of neotethyan oceanic crust in middle late jurassic time these melanges were emplaced probably diachronously during oxfordian kimmeridgian time when the passive margin collapsed creating a foredeep ahead of advancing thrust sheets of melange and ophiolites

geomorphic effectiveness of check dams in a debris flow catchment using multi temporal topographic surveys abstract torrent control works such as grade control dams and sediment retention dams are structural measures for controlling debris flows and debris floods in spite of the widespread presence of such hydraulic structures in steep mountain streams worldwide there are still few studies monitoring the effects of check dams on sediment dynamics the use of repeated topographic surveys allows us to characterize debris flow activity at multiple temporal and spatial scales and its interaction with torrent control works structure from motion sfm technique paired with multi view stereo mvs algorithms represents a low cost opportunity to conduct such multi temporal surveys this enables us to better study the effects of individual debris flows track geomorphic changes and evaluate the effectiveness of torrent control works e g check dams the effect of check dams on sediment dynamics is investigated by means of multi temporal topographic surveys before and after debris flow events in the moscardo torrent eastern italian alps where two check dams have recently been built multi temporal sfm based on images taken from the ground in combination with imagery taken by an unmanned aerial vehicle uav is used to obtain dems and to study topographic changes through the comparison of repeat dems dem of difference i e dod the results show that the new check dams considerably modified sediment dynamics in the studied channel but their performance cannot be considered satisfactory the sediment flowed around the upstream check dam on the right wing while deep erosion observed downstream of the check dam threatened to undermine the foundation s stability moreover debris flow lobes deposited upstream of the check dams could act as sources of sediment further increasing downstream debris flow volume the analysis proposed in this work could help improve design strategies and permitting the identification of a proper site for check dam building

influence of bedrock structures on the spatial pattern of erosional landforms in small alpine catchments structural settings and lithological characteristics are traditionally assumed to influence the development of erosional landforms such as gully networks and rock couloirs in steep mountain rock basins the structural control of erosion of two small alpine catchments of distinctive rock types is evaluated by comparing the correspondences between the orientations of their gullies and rock couloirs with 1 the sliding orientations of potential slope failures mechanisms and 2 the orientation of the maximum joint frequency this latter being considered as the direction exploited primarily by erosion and mass wasting processes these characteristic orientations can be interpreted as structural weaknesses contributing to the initiation and propagation of erosion the morphostructural analysis was performed using digital elevation models and field observations the catchment comprised of magmatic intrusive rocks shows a clear structural control mostly expressed through potential wedges failure such joint configurations have a particular geometry that encourages the development of gullies in hard rock e g through enhanced gravitational and hydrological erosional processes in the catchment underlain by sedimentary rocks penetrative joints that act as structural weaknesses seem to be exploited by gullies and rock couloirs however the lithological setting and bedding configuration prominently control the development of erosional landforms and influence not only the local pattern of geomorphic features but the general morphology of the catchment the orientations of the maximum joint frequency are clearly associated with the gully network suggesting that its development is governed by anisotropy in rock strength these two catchments are typical of bedrock dominated basins prone to intense processes of debris supply this study suggests a quantitative approach for describing the relationship between bedrock jointing and geomorphic features geometry incorporation of bedrock structure can be relevant when studying processes governing the transfer of clastic material for the assessment of sediment yields and in landforms evolution models

zircon geochronology of basement rocks from the pelagonian zone greece constraints on the pre alpine evolution of the westernmost internal hellenides the pelagonian zone of greece is the westernmost segment of the internal hellenides comprising widespread crystalline basement exposures of granites and orthogneisses we dated these basement rocks in order to identify the major crust forming episodes and to understand the evolutionary history of the area in our study we investigated granites gneisses meta rhyolites and mylonites from the major occurrences of the pelagonian zone we applied single zircon dating techniques such as pb pb evaporation conventional u pb and shrimp the majority of the basement rocks gave permo carboniferous intrusion ages thus emphasizing the importance of this crust forming event for the internal hellenides of greece triassic intrusion ages were obtained however for a meta rhyolite from the western pelagonian zone and two mylonites from the eastern pelagonian zone these ages are interpreted to reflect magmatism accompanying early rifting that led to the subsequent opening of the pindos ocean to the west and the meliata ocean to the east of the pelagonian zone the geochronological results demonstrate that the magmatic episodes during which most of the pelagonian zone crystalline basement formed are predominantly pre alpine in age

facies cycles and controls on the evolution of a keep up carbonate platform kimmeridgian swiss jura during the late jurassic accelerated ocean floor spreading and associated sealevel rise were responsible for a worldwide transgression which reached its maximum in the late kimmeridgian in many western european basins this major sea level rise led to the formation of marly and condensed sections in the swiss jura however a shallow carbonate platform kept growing and only subtle changes in the stratigraphic record suggest an increasingly open marine influence field observations and thin section analyses reveal that the central swiss jura was at that time occupied by tidal flats and by more or less open marine lagoons where shoals and bioherms developed the evolution through time of sedimentary facies and bed thicknesses permits the definition of small medium and large scale depositional sequences the diagnostic features of these sequences are independent of scale and seem largely controlled by the kimmeridgian second order transgression a high resolution sequencestratigraphic correlation with biostratigraphically well dated hemipelagic and pelagic sections in the vocontian basin in france reveals that i the most important increase in accommodation recorded in the kimmeridgian of the central swiss jura occurs in the eudoxus ammonite zone late kimmeridgian and corresponds to the second order maximum flooding recognized in many sedimentary basins ii the small and medium scale sequences have time durations corresponding to the first and second orbital eccentricity cycle i e 100 and 400 ka respectively suggesting that sedimentation on the platform and in the basin was at least partly controlled by cyclic environmental changes induced by insolation variations in the milankovitch frequency band the comparison of the high resolution temporal framework defined in the swiss jura and vocontian basin with the sequencestratigraphic interpretation realized in other western european basins shows that the large scale sequence boundaries defined in the kimmeridgian of the swiss jura appear in comparable biostratigraphic positions in most western european basins discrepancies that occur are probably because of local or regional tectonics

the triggering of debris flow due to channel bed failure in some alpine headwater basins of the dolomites analyses of critical runoff the debris deposits at the bottom of very steep natural channels and streams in high mountain areas can be mobilized by runoff triggering a water sediment mixture flow known as debris flow the routing of debris flow through human settlements can cause damage to civil structures and loss of human lives the prediction of such an event or the runoff discharge that triggers it assumes an interest in risk analyses and the planning of defence measures the object of this study is to find a method to determine the critical runoff value that triggers debris flow as a result of channel bed failure historical and rainfall data on 30 debris flows that occurred in six watersheds of the dolomites north eastern italian alps were collected from different sources field investigations at the six sites together with the hydrologic response to the rainfalls that triggered the events were performed to obtain a realistic scenario of the formation of the debris flow there occurred field observations include a survey along the channel of the triggering reach of debris flow with measurements of the channel slope and cross section and sampling of debris deposits for grain size distribution simulated runoff discharge values based on the rainfall recorded by pluviometers were then compared with values obtained through experimental criteria on the initiation and formation of debris flow by bed failure the results are discussed to provide a plausible physical based method for the prediction of the triggering of debris flow by channel bed failure copyright 2007 john wiley sons ltd

quantitative analysis of debris torrent hazards for design of remedial measures debris torrents which are rapid flows of soil and organic debris down steep mountain channels are a major natural hazard in many parts of british columbia a series of recent occurrences along the

assessment of debris flow hazards using a bayesian network abstract comprehensive assessment of debris flow hazard risk is challenging due to the complexity and uncertainties of various related factors a reasonable and reliable assessment should be based on sufficient data and realistic approaches this study presents a novel approach for assessing debris flow hazard risk using bn bayesian network and domain knowledge based on the records of debris flow hazards and geomorphological environmental data for the chinese mainland approaches based on bn svm support vector machine and ann artificial neural network were compared bn provided the highest values of hazard detection probability precision and auc area under the receiver operating characteristic curve the bn model is useful for mapping and assessing debris flow hazard risk on a national scale

foredeep tectonics and carbonate platform dynamics in the huon gulf papua new guinea hawaii mr1 side scan sonar and six channel seismic reflection data reveal a history of carbonate platform growth drowning and back stepping in the huon gulf papua new guinea this is one of the few modern sites where active carbonate platform development and foredeep subsidence are linked 230 th methods date aragonitic shallow water corals recovered from a modern depth of 2000 m at 348 10 ka this documents rapid subsidence of the huon gulf in response to the encroaching finisterre mountains at an average rate of 5 7 mm yr for the past 348 k y the highest subsidence rate reported from any foredeep setting carbonate deposition has moved toward the foreland at an average rate of 110 mm yr over the same period comparisons of the measured age with sea level history derived from the oxygen isotope record suggest that the reefs may have formed during sea level lowstands and drowned during rapid rates of sea level rise

scale amplification of natural debris flows caused by cascading landslide dam failures debris flows are typically caused by natural terrain landslides triggered by intense rainfalls if an incoming mountain torrent collapses a series of landslide dams large debris flows can form in a very short period moreover the torrent can amplify the scale of the debris flow in the flow direction the catastrophic debris flows that occurred in zhouqu china on 8 august 2010 were caused by intense rainfall and the upstream cascading failure of landslide dams along the gullies in the wake of the incident a field study was conducted to better understand the process of cascading landslide dam failures and the formation of debris flows this paper looks at the geomorphic properties of the debris flow gullies estimates the peak flow discharges at different locations using three different methods and analyzes the key modes i e different landslide dam types and their combinations of cascading landslide dam failures and their effect on the scale amplification of debris flows the results show that five key modes in luojiayu gully and two modes in sanyanyu gully accounted for the scale amplification of downstream debris flows in the zhouqu event this study illustrates how the hazardous process of natural debris flows can begin several kilometers upstream as a complex cascade of geomorphic events failure of landslide dams and erosion of the sloping bed can scale to become catastrophic discharges neglecting recognition of these hazardous geomorphic and hydrodynamic processes may result in a high cost

initiation and flow conditions of contemporary flows in martian gullies understanding the initial and flow conditions of contemporary flows in martian gullies generally believed to be triggered and fluidized by co2 sublimation is crucial for deciphering climate conditions needed to trigger and sustain them we employ the ramms rapid mass movement simulation debris flow and avalanche model to back calculate initial and flow conditions of recent flows in three gullies in hale crater we infer minimum release depths of 1 0 1 5 m and initial release volumes of 100 200 m3 entrainment leads to final flow volumes that are 2 5 5 5 times larger than initially released and entrainment is found necessary to match the observed flow deposits simulated mean cross channel flow velocities decrease from 3 4 m s 1 to 1 m s 1 from release area to flow terminus while flow depths generally decrease from 0 5 1 m to 0 1 0 2 m the mean cross channel erosion depth and deposition thicknesses are 0 1 0 3 m back calculated dry coulomb friction ranges from 0 1 to 0 25 and viscous turbulent friction between 100 200 m s 2 which are values similar to those of granular debris flows on earth these results suggest that recent flows in gullies are fluidized to a similar degree as are granular debris flows on earth using a novel model for mass flow fluidization by co2 sublimation we are able to show that under martian atmospheric conditions very small volumetric fractions of co2 of 1 within mass flows may indeed yield sufficiently large gas fluxes to cause fluidization and enhance flow mobility

floods in mountain environments a synthesis floods are a crucial agent of geomorphic change in the channels and valley floors of mountains watercourses at the same time they can be highly damaging to property infrastructure and life because of their high energy mountain watercourses are highly vulnerable to environmental changes affecting their catchments and channels many factors have modified and frequently still tend to modify the environmental conditions in mountain areas with impacts on geomorphic processes and the frequency magnitude and timing of floods in mountain watercourses the ongoing climate changes vary between regions but may affect floods in mountain areas in many ways in many mountain regions of europe widespread afforestation took place over the twentieth century considerably increasing the amounts of large wood delivered to the channels and the likelihood of jamming bridges at the same time deforestation continues in other mountain areas accelerating runoff and amplifying the magnitude and frequency of floods in foreland areas in many countries in channel gravel mining has been a common practice during recent decades the resultant deficit of bed material in the affected channels may suddenly manifest during flood events resulting in the failure of scoured bridges or catastrophic channel widening during the past century many rivers in mountain and foreland areas incised deeply the resultant loss of floodplain water storage has decreased attenuation of flood waves hence increasing flood hazard to downstream river reaches on the other hand a large amount of recent river restoration activities worldwide may provide examples of beneficial changes to flood risk attained as a result of increased channel storage or reestablished floodplain water storage relations between geomorphic processes and floods operate in both directions which means that changes in flood probability or the character of floods e g increased wood load may significantly modify the morphology of mountain rivers but morphological changes of rivers can also affect hydrological properties of floods and the associated risk for societies this paper provides a review of research in the field of floods in mountain environments and puts the papers of this special issue dedicated to the same topic into context it also provides insight into innovative studies methods or emerging aspects of the relations between environmental changes geomorphic processes and the occurrence of floods in mountain rivers

alpine debris flows triggered by a 28 july 1999 thunderstorm in the central front range colorado on 28 july 1999 about 480 alpine debris flows were triggered by an afternoon thunderstorm along the continental divide in clear creek and summit counties in the central front range of colorado the thunderstorm produced about 43 mm of rain in 4 h 35 mm of which fell in the first 2 h several debris flows triggered by the storm impacted interstate highway 70 u s highway 6 and the arapahoe basin ski area we mapped the debris flows from color aerial photography and inspected many of them in the field three processes initiated debris flows the first process initiated 11 of the debris flows and involved the mobilization of shallow landslides in thick often well vegetated colluvium the second process which was responsible for 79 of the flows was the transport of material eroded from steep unvegetated hillslopes via a system of coalescing rills the third which has been termed the firehose effect initiated 10 of the debris flows and occurred where overland flow became concentrated in steep bedrock channels and scoured debris from talus deposits and the heads of debris fans these three processes initiated high on steep hillsides 30 in catchments with small contributing areas 8000 m2 however shallow landslides occurred on slopes that were significantly less steep than either overland flow process based on field observations and examination of soils mapping of the northern part of the study area we identified a relation between the degree of soil development and the process type that generated debris flows in general areas with greater soil development were less likely to generate runoff and therefore less likely to generate debris flows by the firehose effect or by rilling the character of the surficial cover and the spatially variable hydrologic response to intense rainfall rather than a threshold of contributing area and topographic slope appears to control the initiation process in the high alpine of the front range because debris flows initiated by rilling and the firehose effect tend to increase in volume as they travel downslope these debris flows are potentially more hazardous than those initiated by shallow landslides which tend to deposit material along their paths

storm rainfall conditions for floods and debris flows from recently burned areas in southwestern colorado and southern california abstract debris flows generated during rain storms on recently burned areas have destroyed lives and property throughout the western u s field evidence indicate that unlike landslide triggered debris flows these events have no identifiable initiation source and can occur with little or no antecedent moisture using rain gage and response data from five fires in colorado and southern california we document the rainfall conditions that have triggered post fire debris flows and develop empirical rainfall intensity duration thresholds for the occurrence of debris flows and floods following wildfires in these settings this information can provide guidance for warning systems and planning for emergency response in similar settings debris flows were produced from 25 recently burned basins in colorado in response to 13 short duration high intensity convective storms debris flows were triggered after as little as six to 10 min of storm rainfall about 80 of the storms that generated debris flows lasted less than 3 h with most of the rain falling in less than 1 h the storms triggering debris flows ranged in average intensity between 1 0 and 32 0 mm h and had recurrence intervals of two years or less threshold rainfall conditions for floods and debris flows sufficiently large to pose threats to life and property from recently burned areas in south central and southwestern colorado are defined by i 6 5 d 0 7 and i 9 5 d 0 7 respectively where i rainfall intensity in mm h and d duration in hours debris flows were generated from 68 recently burned areas in southern california in response to long duration frontal storms the flows occurred after as little as two hours and up to 16 h of low intensity 2 10 mm h rainfall the storms lasted between 5 5 and 33 h with average intensities between 1 3 and 20 4 mm h and had recurrence intervals of two years or less threshold rainfall conditions for life and property threatening floods and debris flows during the first winter season following fires in ventura county and in the san bernardino san gabriel and san jacinto mountains of southern california are defined by i 12 5 d 0 4 and i 7 2 d 0 4 respectively a threshold defined for flood and debris flow conditions following a year of vegetative recovery and sediment removal for the san bernardino san gabriel and san jacinto mountains of i 14 0 d 0 5 is approximately 25 mm h higher than that developed for the first year following fires the thresholds defined here are significantly lower than most identified for unburned settings perhaps because of the difference between extremely rapid runoff dominated processes acting in burned areas and longer term infiltration dominated processes on unburned hillslopes

rainfall induced landslides and debris flows in this preface we introduce the special issue on rainfall induced landslides and debris flows the topic is of high interest for many practical and scientific reasons in fact rainfall is the most relevant factor for the triggering of both shallow and deep seated landslides and rainfall analysis is the most frequently adopted approach for forecasting the occurrence of such phenomena the six papers of the special issue cover most of the key issues relative to rainfall induced landslides starting from the analysis of these contributions we identify and discuss in this paper several main topics that deserve further research in the field of rainfall induced landslide such as the uncertainty of the data the quality of geotechnical analysis the validation of the models and the applicability of results in the framework of natural hazards copyright 2007 john wiley sons ltd

the maliac ocean the origin of the tethyan hellenic ophiolites the hellenides part of the alpine orogeny in greece are rich in ophiolitic units these ophiolites and associated units emplaced during jurassic obduction testify for the existence of one or several tethyan oceanic realms the paleogeography of these oceanic areas has not been precisely described however all the authors now agree on the presence of a main triassic jurassic ocean on the eastern side of the pelagonian zone vardar domain we consider that this maliac ocean is the most important ocean in greece and albania here we limit the detailed description of the maliac ocean to the pre convergence period of approximately 70 ma between the middle triassic rifting to the middle jurassic convergence period a quick overview on the destiny of the different parts of the maliac ocean during the convergence period is also proposed the studied exposures allow to reconstruct 1 the middle to late triassic maliac oceanic lithosphere corresponding to the early spreading activity at a mid oceanic ridge 2 the western maliac margin widely exposed in the othris and argolis areas 3 the eastern maliac margin in the eastern vardar domain peonias and paikon zones we established the following main characteristics of the maliac ocean 1 the middle triassic rifting marked by a rapid subsidence and volcanism seems to be short lived few my 2 the maliac lithosphere is only represented by middle to late triassic units especially the fourka unit composed of wpb oib and morb pillow lavas locally covered by a pelagic middle triassic to middle jurassic sedimentary cover 3 the western margin is the most complete and our data allow to distinguish a proximal and a deeper distal margin 4 the evolution of the eastern margin peonias and paikon series is similar to that of the w margin except for its jurassic terrigenous sediments while the proximal w margin was dominated by calcarenites 5 we show that the w and e margins are not volcanic passive margins and 6 during the middle jurassic convergence period the eastern margin became an active margin and both margins were affected by obduction processes

petrogenesis and tectonic significance of jurassic iat magma types in the hellenide ophiolites as deduced from the rhodiani ophiolites pelagonian zone greece abstract the rhodiani ophiolites are represented by two tectonically superimposed ophiolitic units the lower ultramafic unit and the upper volcanic unit both bearing calcareous sedimentary covers the ultramafic unit consists of mantle harzburgites with dunite pods and chromitite ores and represents the typical mantle section of supra subduction zone ssz settings the volcanic unit is represented by a sheeted dyke complex overlain by a pillow and massive lava sequence both including basalts basaltic andesites andesites and dacites chemically the volcanic unit displays low ti affinity typical of island arc tholeiite iat ophiolitic series from ssz settings having as most distinctive chemical features low ti v ratios the rare earth element and incompatible element composition of the more primitive basaltic andesites from the rhodiani ophiolites can be successfully reproduced with about 15 non modal fractional melting of depleted lherzolites which are very common in the hellenide ophiolites the calculated residua correspond to the depleted harzburgites found in the rhodiani and othrys ophiolites both field and chemical evidence suggest that the whole sequence of the rhodiani volcanic unit from basalt to dacite originated by low pressure fractional crystallization under partially open system conditions the modelling of mantle source melt generation and mantle residua carried out in this paper provides new constraints for the tectono magmatic evolution of the mirdita pindos oceanic basin

velocity and runout simulation of destructive debris flows and debris avalanches in pyroclastic deposits campania region italy the campanian apennines are characterized by the presence of monocline ridges mainly formed by limestone during the periods of volcanic activity of the somma vesuvius and phlegrean fields the ridges were mantled with pyroclastic materials in varying thickness the pyroclastics have been involved in destructive landslides both in historical time and in the recent past 1997 1998 1999 the landslides occur following intense and prolonged rainfalls in some cases landslides extended up to 4 km into the surrounding lowlands and reached towns causing severe destruction and over 200 deaths generally the landslides begin as small debris slides that develop into large shallow debris avalanches or debris flows involving pyroclastic horizons and colluvial soils 0 5 2 m thick on steep and vegetated slopes often at the heads of gullies during motion the landslide materials eroded vegetation and soils from the slope so that the moving material volume tended to increase then proceeding towards and beyond the base of the slopes the phenomena evolved into hyperconcentrated streamflow due to dilution by incorporating water the results of motion analyses are described an empirical rheological relationship was used including two principal terms that depend on the total normal stress and on the flow velocity on this basis the model has simulated the velocity and duration of debris avalanches and the distribution of the deposits the selected areas were those of sarno quindici and cervinara where a large amount of data is available both on the material properties and geomorphological setting it was found that the majority of the cases at the two sites can be simulated successfully with only one specific pair of rheologic parameters this provides the possibility for first order predictions to be made of the motion of future landslides such predictions will be a valuable tool for outlining potential hazard areas and designing remedial measures

rainfall control of debris flow triggering in the real torrent southern french prealps abstract this paper investigates the occurrence of debris flow due to rainfall forcing in the real torrent a very active debris flow prone catchment in the southern french prealps the study is supported by a 4 year record of flow responses and rainfall events from three high frequency monitoring stations equipped with geophones flow stage sensors digital cameras and rain gauges measuring rainfall at 5 min intervals the classic method of rainfall intensity duration id threshold was used and a specific emphasis was placed on the objective identification of rainfall events as well as on the discrimination of flow responses observed above the id threshold the results show that parameters used to identify rainfall events significantly affect the id threshold and are likely to explain part of the threshold variability reported in the literature this is especially the case regarding the minimum duration of rain interruption mdri between two distinct rainfall events in the real torrent a 3 h mdri appears to be representative of the local rainfall regime a systematic increase in the id threshold with drainage area was also observed from the comparison of the three stations as well as from the compilation of data from experimental debris flow catchments a logistic regression used to separate flow responses above the id threshold revealed that the best predictors are the 5 min maximum rainfall intensity the 48 h antecedent rainfall the rainfall amount and the number of days elapsed since the end of winter used as a proxy of sediment supply this emphasizes the critical role played by short intense rainfall sequences that are only detectable using high time resolution rainfall records it also highlights the significant influence of antecedent conditions and the seasonal fluctuations of sediment supply

regionalization of rainfall thresholds an aid to landslide hazard evaluation rainfall soil properties and morphology are major factors controlling shallow landsliding a series of meteorological events that triggered soil slips in northern italy were studied to define rainfall thresholds and to evaluate a possible regionalization soil properties triggering rainfall and local lithological and morphometrical settings of different sites were used as input to an infiltration model the approach allows the recognition of several triggering conditions in the piedmont pre alpine and alpine regions this suggests the need for different rainfall thresholds with respect to those derived with other methods intensity versus rainfall duration relationships become particularly important when related to soil permeability and thickness and demonstrate the role of antecedent precipitation events with exceptional water discharge from obstructed road culverts reveal the role played by anthropic structures in triggering such phenomena different approaches to slope stability analysis are shown taking into account bedrock lithology topography seepage and local saturation conditions

glacial to interglacial fluctuations in productivity in the equatorial pacific as indicated by marine barite an empirical correlation between marine barite baso4 accumulation rate in core top sediment samples from two equatorial pacific transects at 140 w and 110 w and the estimated primary productivity of the overlying water column were used to evaluate glacial to interglacial changes in productivity fluctuations in barite accumulation rates down core indicate that during glacial periods of the past 450 000 years the productivity in the central and eastern equatorial pacific was about two times that during intervening interglacial periods this result is consistent with other evidence that productivity was high in the eastern and central equatorial pacific during the last glacial

coarse sediment transport in mountain streams in colorado and wyoming usa since the early 1990s us forest service researchers have made thousands of bedload measurements in steep coarse grained channels in colorado and wyoming usa in this paper we use data from 19 of those sites to characterize patterns and rates of coarse sediment transport for a range of channel types and sizes including step pool plane bed pool riffle and near braided channels this effort builds upon previous work where we applied a piecewise regression model to 1 relate flow to rates of bedload transport and 2 define phases of transport in coarse grained channels earlier the model was tested using bedload data from eight sites on the fraser experimental forest near fraser colorado the analysis showed good application to those data and to data from four supplementary channels to which the procedure was applied the earlier results were however derived from data collected at sites that for the most part have quite similar geology and runoff regimes in this paper we evaluate further the application of piecewise regression to data from channels with a wider range of geomorphic conditions the results corroborate with those from the earlier work in that there is a relatively narrow range of discharges at which a substantial change in the nature of bedload transport occurs the transition from primarily low rates of sand transport phase i to higher rates of sand and coarse gravel transport phase ii occurs on average at about 80 per cent of the bankfull 1 5 year return interval discharge a comparison of grain sizes moved during the two phases showed that coarse gravel is rarely trapped in the samplers during phase i transport moreover the movement and capture of the d16 to d25 grain size of the bed surface seems to correspond with the onset of phase ii transport particularly in systems with largely static channel surfaces however while there were many similarities in observed patterns of bedload transport at the 19 studied sites each had its own bedload signal in that the rate and size of materials transported largely reflected the nature of flow and sediment particular to that system published in 2005 by john wiley sons ltd