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

experimental modelling of debris flow behaviour using a geotechnical centrifuge physical modelling of debris flows has been carried out in the geotechnical drum centrifuge at eth zurich a new apparatus to model debris flows in the centrifuge is described the apparatus permits the final reach of a typical debris flow to be modelled within the centrifuge with unconsolidated material flowing down a slope to deposit as a fan around the drum experiments are described for both fixed base conditions and erodible bases tests to examine the verification modelling of models show that debris flow behaviour is governed mainly by friction and consolidation processes although some resolution is required between flow behaviour downslope and flow arrest during runout the results are compared with bulk parameters determined for field scale debris flows it is found that some important flow mechanisms such as contact dominated behaviour and high pore pressures are developed that are closer to those developed at field scale than tests conducted at 1g velocity profiles for erodible beds are

a probabilistic model of debris flow delivery to stream channels demonstrated for the coast range of oregon usa debris flows are important geomorphic agents in mountainous terrains that shape channel environments and add a dynamic element to sediment supply and channel disturbance identification of channels susceptible to debris flow inputs of sediment and organic debris and quantification of the likelihood and magnitude of those inputs are key tasks for characterizing spatial and temporal patterns found in channel conditions and associated habitats in a river network widely available digital elevation and land cover data 10 m dems and 25 m satellite imagery offer the potential to assess debris flow runout paths over regional extents this paper presents a model for using these data to calculate empirical probabilities for debris flow runout over dem determined flow paths and shows how these probabilities can be combined over all sources to estimate the potential for debris flow delivery to stream reaches throughout entire channel networks the model is calibrated and model predictions are compared to field mapped debris flow travel paths from study sites in the coast range of oregon usa this model predicts debris flow probability over channel reach scales that can be aggregated to basin scale measures of debris flow potential it offers unprecedented ability to characterize debris flow effects over channel networks providing a tool for risk assessment and for generating hypotheses that relate topographic and forest cover controls on debris flow runout to the types and abundance of channel habitats in a river basin

on the assessment of the management priority of sediment source areas in a debris flow catchment in many alpine catchments the monitoring and hazard mitigation of debris flow events require enormous economic and social resources to confront these problems a subjective estimation of the most hazardous zones of the basin could be useful in the best sustainable planning of protective measures in this paper a new methodology is proposed that develops a management priority index mpi to rank sediment source areas by their quantitative capability to deliver debris flow volumes to a point of interest within the catchment the mpi sets the intervention priority based on a combination of three sub indicators a susceptibility indicator evaluating the overall catchment predisposition to generate debris flow a triggering indicator and a volume budget indicator assessing the rate of deliverable volume to a selected outlet mpi was applied to the basin of the rio gadria catchment venosta valley bolzano italy an alpine basin with an unlimited sediment supply that is characterized by multiple very active shallow landslides and bare soil zones the proposed ranking method was successfully verified using post event surveys and through evidence from consolidation check dams built over many years in the basin copyright 2014 john wiley sons ltd

an empirical statistical model for debris flow travel distance an empirical model is presented for analysis of debris flows based on field observations of landslides from clear cuts in the queen charlotte islands british columbia given an initial failure volume changes in event magnitude arising from entrainment and deposition along the path of movement are used to establish the point at which the cumulative flow volume diminishes to zero and therefore the total travel distance hillslope morphology is used to assign three types of flow behaviour unconfined confined and transition flow flow behaviour and slope angle determine the occurrence of entrainment or deposition in the model for every reach of the event path volume change in a reach is calculated from regression analysis of the queen charlotte islands field observations predictor variables are reach length width of entrainment and or deposition and slope angle together with a bend angle function and the incoming flow volume key words slope stability debris flow travel distance runout ris

exceptionally preserved ostracodes from a middle miocene palaeolake california usa abstract exceptionally well preserved specimens of a new cypridid ostracode crustacea raepula ira sp nov are described from palaeolake sediments of the middle miocene barstow formation of the mud hills southern california this is only the second occurrence of exceptionally preserved ostracodes from the miocene based on ages obtained from associated volcanic tuffs the palaeolake sediments were deposited between 16 3 and 15 8 ma the ostracodes form one element of a diverse lake community dominated by fairy shrimps copepods diatoms larvae of diving beetles flies and mosquitoes and body fossils and ephippia of branchiopods and anomopods the ostracodes are preserved three dimensionally with their soft anatomy replicated in microcrystalline silica submicron scale details such as sensory setae are preserved surpassing the resolution of most other ostracode bearing lagerstatten and allowing their biology to be compared with extant taxa supplementary material red blue anaglyphs of the exceptionally preserved ostracodes are available at http www geolsoc org uk sup18407

fan surface evidence for debris flow avulsion controls and probabilities saline valley california debris flow fans form by shifts of the active channel termed avulsions field and experimental evidence suggest that debris flow avulsions may be induced by depositional lobes that locally plug a channel or super elevation of the channel bed above the surrounding fan surface by analogy to fluvial fans to understand debris flow avulsion processes we differentiate between these controls by quantifying the spatial distribution of debris flow lobe and channel dimensions along with channel bed super elevation on nine debris flow fans in saline valley california usa channel beds are generally super elevated by 2 5 channel depths above the fan surface and locally by more than 7 channel depths thereby substantially exceeding super elevation on fluvial fans depositional lobe thickness and channel depth decrease with distance from the fan apex although both are highly variable across the fans median channel depths roughly correspond to the 50 75th percentiles of lobe thicknesses while minimum channel depths roughly correspond to the 10 25th percentiles in contrast the thicknesses of lobes that have triggered avulsions roughly equal local channel depths and are on average twice as thick as the local median lobe thickness the spatial correspondence between avulsion locations and thick lobe deposits and the lack of correlation with channel bed super elevation leads us to infer that avulsions on these fans are mostly caused by thick lobes forming channel plugs although results may vary with climatic and tectonic setting our findings indicate that avulsion hazard assessment on populated fans should include mapping and monitoring of channel depths relative to typical deposit thicknesses on a given fan

identifying post earthquake debris flow hazard using massflow catastrophic debris flows are common after large earthquakes and pose a significant risk for recovering communities the depositional volume of these large debris flows is often much greater than the initiation volume suggesting that bulking of the flow plays an important role in determining their volume speed and runout distance observations from recent earthquakes have driven progress in understanding the relationship between triggering rainfall events and the timing of post earthquake debris flows however we lack an adequate mechanism for quantifying bulking and applying it within a hazard context here we apply a 2d dynamic debris flow model massflow that incorporates a process based expression of basal entrainment to understand how debris flow bulking may occur within post earthquake catchments and develop hazard maps focussing on catchments in the epicentral area of the 2008 mw 7 9 wenchuan earthquake we first parameterised the model based on a large debris flow that occurred within the hongchun catchment before applying the calibrated model to adjoining catchments a model sensitivity analysis identified three main controls on debris flow bulking the saturation level of entrainable material along the flow pathway and the size and position of initial mass failures the model demonstrates that the difference between small and very large debris flows occur across a narrow range of pore water ratios below 0 65 flows falter at the base of hillslopes and come to rest in the valley bottom above 0 70 they build sufficient mass and momentum to sustain channelised flow and transport large volumes of material beyond the valley confines finally we applied the model across different catchments to develop hazard maps that demonstrate the utility of massflow in post earthquake planning within the wenchuan epicentral region

erosional effects on runout of fast landslides debris flows and avalanches a numerical investigation the mechanism of mass changes in debris transportation process is an important topic in the study of fast landslides debris flows and avalanches basal erosion is recognised as a dynamic interaction between the original moving material and the entrained basal topsoil shearing along their non slip contact surface in this paper we propose a new concept of yield rate and establish the erosional relationship to bridge these two systems a pertinent mathematical model and numerical implementation are formulated parametric numerical experiments are conducted to compare the erosional effects the simulated results are consistent with available experimental and field observations the influence of the involvement of the erosive material on runout behaviour and the global mobility of the moving material are elucidated the proposed method is then employed to analyse a recent debris flow event in northern italy the excellent match to the field data gives it a plausible potential application to the analysis of this type of gravity driven flow with significant erosion defined in a dimensionless form the proposed yield rate can be estimated conveniently in general geotechnical practices

material sources supplying debris flows in jiangjia gully debris flow susceptibility is usually evaluated through material supplies and topographic features and the formation of debris flow is ascribed to the factors over the whole valley almost ignoring detailed distribution of material sources and variety of behaviors in different tributaries so far there is not a comprehensive picture of debris flow developing from source tributaries to mainstream channel debris flow in jiangjia gully jjg exhibits diversity of surges and vivid scenarios concerning the forming and developing mechanisms this study takes jjg as an example to explore how the materials are distributed in the valley and how the spatial heterogeneity of material distribution and tributary evolution influence the forming of variety of debris flow surges it is found that most materials are distributed in tributaries of active stages with evolution index between 0 55 and 0 65 the occurrence of debris flow relies more on the spatial distribution of source tributaries than on the quantity of the material local conditions of tributaries such as the concentration of materials the granular structure of soils and the locations receiving frequent rainfalls are the very factors governing a debris flow event it is the spatial heterogeneity of sources and material supplies that result in the variety of debris flow surges in jjg similar mode is believed to occur in debris flows in other regions

linkage of sediment supply and transport processes in miyagawa dam catchment japan 1 linkages between sediment supply by episodic geomorphic processes obtained from aerial photographs and field surveys and sediment transport estimated from changes in sediment deposition behind a large dam were investigated in the miyagawa dam catchment central japan a total of 6667 landslides were confirmed in the period from 1965 to 2000 on the basis of seven temporal pairs of aerial photographs both the occurrence of landslides and discharge into the dam lake affect sediment yield indicating that fluvial systems in miyagawa dam catchment are supply limited with respect to sediment sediment yields are affected by not only the initial failed volume of landslides but also the mobility of landslides and debris flows in miyagawa dam catchment percentages of landslides reaching channels varied from 56 in 1997 2000 to 75 in 1976 1981 and were correlated with maximum hourly rainfall in addition the mobility of debris flows was higher during periods with high maximum instantaneous discharge compared to lower discharge suggesting that the water content both in initially failed materials and transported sediment controlled their mobility topography also affected the mobility of landslides debris flows for catchments 0 1 km2 the percentage of channel network length impacted by debris flows decreased with increasing catchment area due to reduced channel gradient thus both the magnitude of rainfall runoff events and the catchment topography affect how landslide sediment contributes to sediment yield at the large catchment scale

geological evolution of the marine selenium cycle insights from the bulk shale δ82 76se record and isotope mass balance modeling bulk 82 76se values of representative marine shales from the paleoarchean to the present day vary between approximately 3 and 3 with only local deviations beyond this range this muted se isotope variability in the shale record contrasts with the relatively large fractionations associated with abiotic and microbial se oxyanion reduction seen in experimental studies long term temporal trends in the bulk shale data do not directly correlate with changes in redox conditions of the global ocean although a minor but significant shift towards more negative formation averaged 82 76se values appears to track oxygenation of the deep ocean at the end of the proterozoic we hypothesize that extensive 82 76se variability in the shale data was suppressed due to the early emergence of biological assimilatory uptake and the resulting persistence of low seawater se concentrations coupled with small authigenic se outputs throughout most of geological time in the modern ocean se is an essential micronutrient with a relatively short residence time of about 11 500 yrs the marine se cycle is dominated by assimilation into biomass and subsequent recycling in the water column and surface sediments i e processes that result in only minimal isotopic fractionation we suggest that similar processes dominated back through the geological record to archean times our model shows that paleoceanographic information could in principle be extracted from proxy data on the se isotopic composition of seawater once isotopic differences can be readily discerned between individual sedimentary se pools

hillslope channel sediment transfer in a slope failure event wet swine gill lake district northern england this paper describes and analyses a hillslope channel slope failure event that occurred at wet swine gill lake district northern england this comprised a hillslope slide 180 m3 c 203 36 t which coupled with the adjacent stream resulting in a channelized debris flow and fluvial flood the timing of the event is constrained between january and march 2002 the hillslope failure occurred in response to a rainfall snowmelt trigger on ground recently disturbed by a heather moorland fire and modified by artificial drainage slide and flow dynamics are estimated using reconstructed velocity and discharge values along the sediment transfer path there is a rapid downstream reduction in both maximum velocity from 9 8 to 1 3 m s 1 and maximum discharge ranging from 33 5 to 2 4 m3 s 1 a volumetric sediment budget quantified a high degree of coupling between the hillslope and immediate channel 92 167 m3 but virtually all of the sediment was retained in the first order tributary channel approximately 44 81 m3 of the slide volume was retained in the run up deposit and termination of the debris flow prior to the main river meant that the remainder did not discharge into the fluvial system downstream these results suggest poor transmission of sediment to the main river at the time of the event but importantly an increase in available material for post event sediment transfer processes within the small upland tributary

debris flow runout predictions based on the average channel slope acs prediction of the runout distance of a debris flow is an important element in the delineation of potentially hazardous areas on alluvial fans and for the siting of mitigation structures existing runout estimation methods rely on input parameters that are often difficult to estimate including volume velocity and frictional factors in order to provide a simple method for preliminary estimates of debris flow runout distances we developed a model that provides runout predictions based on the average channel slope acs model for non volcanic debris flows that emanate from confined channels and deposit on well defined alluvial fans this model was developed from 20 debris flow events in the western united states and british columbia based on a runout estimation method developed for snow avalanches this model predicts debris flow runout as an angle of reach from a fixed point in the drainage channel to the end of the runout zone the best fixed point was found to be the mid point elevation of the drainage channel measured from the apex of the alluvial fan to the top of the drainage basin predicted runout lengths were more consistent than those obtained from existing angle of reach estimation methods results of the model compared well with those of laboratory flume tests performed using the same range of channel slopes the robustness of this model was tested by applying it to three debris flow events not used in its development predicted runout ranged from 82 to 131 of the actual runout for these three events prediction interval multipliers were also developed so that the user may calculate predicted runout within specified confidence limits

linking rainfall induced landslides with debris flows runout patterns towards catchment scale hazard assessment abstract debris flows and landslides induced by heavy rainfall represent an ubiquitous and destructive natural hazard in steep mountainous regions for debris flows initiated by shallow landslides the prediction of the resulting pathways and associated hazard is often hindered by uncertainty in determining initiation locations volumes and mechanical state of the mobilized debris and by model parameterization we propose a framework for linking a simplified physically based debris flow runout model with a novel landslide hydro mechanical triggering lht model to obtain a coupled landslide debris flow susceptibility and hazard assessment we first compared the simplified debris flow model of perla 1980 with a state of the art continuum based model ramms and with an empirical model of rickenmann 1999 at the catchment scale the results indicate that predicted runout distances by the perla model are in reasonable agreement with inventory measurements and with the other models predictions of localized shallow landslides by lht model provides information on water content of released mass to incorporate effects of water content and flow viscosity as provided by lht on debris flow runout we adapted the perla model the proposed integral link between landslide triggering susceptibility quantified by lht and subsequent debris flow runout hazard calculation using the adapted perla model provides a spatially and temporally resolved framework for real time hazard assessment at the catchment scale or along critical infrastructure roads railroad lines

a probabilistic multidimensional approach to quantify large wood recruitment from hillslopes in mountainous forested catchments abstract large wood lw plays a key role in physical chemical environmental and biological processes in most natural and seminatural streams however it is also a source of hydraulic hazard in anthropised territories recruitment from fluvial processes has been the subject of many studies whereas less attention has been given to hillslope recruitment which is linked to episodic and spatially distributed events and requires a reliable and accurate slope stability model and a hillslope channel transfer model the purpose of this study is to develop an innovative lw hillslope recruitment estimation approach that combines forest stand characteristics in a spatially distributed form a probabilistic multidimensional slope stability model able to include the reinforcement exerted by roots and a hillslope channel transfer procedure the approach was tested on a small mountain headwater catchment in the eastern italian alps that is prone to shallow landslide and debris flow phenomena the slope stability model that had not been calibrated provided accurate performances in terms of unstable areas identification according to the landslide inventory auc 0 832 and of lw volume estimation in comparison with lw volume produced by inventoried landslides 7702 m3 corresponding to a recurrence time of about 30 years in the susceptibility curve the results showed that most lw potentially mobilised by landslides does not reach the channel network only about 16 in agreement with the few data reported by other studies as well as the data normalized for unit length of channel and unit length of channel per year 0 116 m3 km and 0 4 m3 km y 1 this study represents an important contribution to lw research a rigorous and site specific estimation of lw hillslope recruitment should in fact be an integral part of more general studies on lw dynamics for forest planning and management and positioning in channel wood retention structures

a spectral clustering search algorithm for predicting shallow landslide size and location the potential hazard and geomorphic significance of shallow landslides depend on their location and size commonly applied one dimensional stability models do not include lateral resistances and cannot predict landslide size multidimensional models must be applied to specific geometries which are not known a priori and testing all possible geometries is computationally prohibitive we present an efficient deterministic search algorithm based on spectral graph theory and couple it with a multidimensional stability model to predict discrete landslides in applications at scales broader than a single hillslope using gridded spatial data the algorithm is general assuming only that instability results when driving forces acting on a cluster of cells exceed the resisting forces on its margins and that clusters behave as rigid blocks with a failure plane at the soil bedrock interface this algorithm recovers predefined clusters of unstable cells of varying shape and size on a synthetic landscape predicts the size location and shape of an observed shallow landslide using field measured physical parameters and is robust to modest changes in input parameters the search algorithm identifies patches of potential instability within large areas of stable landscape within these patches will be many different combinations of cells with a factor of safety less than one suggesting that subtle variations in local conditions e g pore pressure and root strength may determine the ultimate form and exact location at a specific site nonetheless the tests presented here suggest that the search algorithm enables the prediction of shallow landslide size as well as location across landscapes

interplay of rheology and entrainment in debris avalanches a numerical study flow type landslides are a major global hazard they occur worldwide and are responsible for a large number of casualties significant structural damage to property and infrastructure and economic losses the features of debris avalanches are particularly important as they involve open slopes and affect triangular source areas when initial slides turn into avalanches through further failures or eventual soil entrainment in this paper the propagation stage of debris avalanches is numerically modelled to provide information such as the propagation pattern of the mobilized material and its velocity thickness and run out distance the use of a depth integrated model has the following advantages i it adequately accommodates the irregular topography of real slopes which greatly affects the evolution of the propagation stage and ii it is less time consuming than full three dimensional approaches the model is named geoflow sph and has previously been applied to theoretical experimental and re

predicting deposition of debris flows in mountain channels an empirical model for predicting deposition of coarse textured debris flows in confined mountain channels is developed based on field measurements of 14 debris flows in the pacific northwest u s a the model uses two criteria for deposition channel slope less than 3 5 and tributary junction angle greater than 70 the model is tested by predicting travel distances of 15 debris flows in the oregon coast range and six debris flows in the washington cascades u s a the model is further tested on 44 debris flows in two lithological types in the oregon coast range using aerial photos and topographic maps on these flows only the approximate travel distance is known the model can be used by resource professionals to identify the potential for impacts from debris flows key words debris flow deposition travel erosion

a model for the runout analysis of rapid flow slides debris flows and avalanches runout analyses are used for risk assessment and design of remedial measures against rapid landslides such as debris flows debris avalanches rockslide avalanches large scale liquefaction failure

visualization of dominant stress transfer mechanisms in experimental debris flows of different particle size distribution physical modelling of debris flow in a small scale flume has been carried out to investigate the internal stress transfer mechanisms within unsteady saturated and segregating granular free surfac

debris flows some physical characteristics and behaviour field observations on 449 debris flows in the queen charlotte islands british columbia are summarized movement of debris is classified according to seven characteristic types designated for the purposes of the study data on the physical characteristics of the events are presented an analysis of the data is made with reference to event initiation yield and deposition using both mechanistic and morphological criteria for those events which initiate on an open slope the infinite slope model is used to establish a relationship between field drainage class and slope angle for assumed frictional and cohesive soil strength parameters the field drainage classes are directly related to the postulated location of the groundwater surface within the depth of the rupture plane deposition of channelized events is found to be influenced by the ratio of channel width to channel gradient with the onset of deposition expected when the ratio exceeds unity five classes of depositional area are proposed the mag

effects of debris flow composition on runout depositional mechanisms and deposit morphology in laboratory experiments predicting debris flow runout is of major importance for hazard mitigation apart from topography and volume runout distance and area depends on debris flow composition and rheology but how is poorly understood we experimentally investigated effects of composition on debris flow runout depositional mechanisms and deposit geometry the small scale experimental debris flows were largely similar to natural debris flows in terms of flow behavior deposit morphology grain size sorting channel width depth ratio and runout deposit geometry lobe thickness and width in our experimental debris flows is largely determined by composition while the effects of initial conditions of topography i e outflow plain slope and channel slope and width and volume are negligible we find a clear optimum in the relations of runout with coarse material fraction and clay fraction increasing coarse material concentration leads to larger runout however excess coarse material results in a large accumulation of coarse debris at the flow front and enhances diffusivity increasing frontal friction and decreasing runout increasing clay content initially enhances runout but too much clay leads to very viscous flows reducing runout runout increases with channel slope and width outflow plain slope debris flow volume and water fraction these results imply that debris flow runout depends at least as much on composition as on topography this study improves understanding of the effects of debris flow composition on runout and may aid future debris flow hazard assessments

geohazards of slope mass movement and its prevention in hong kong rapid urban development in hilly terrain coupled with tropical storms with heavy rainfall has led to the frequent occurrence of disastrous landslides in hong kong this paper outlines several case histories of such disastrous landslides in hong kong and the major efforts that have been made to mitigate landslide hazards in hong kong since the mid 1970s factors that contributed to such landslides and their causative mechanisms are analyzed methods of predicting the runout distance and lateral extent of rainfall induced slope failures are summarized slope maintenance requirements and stabilization measures are delineated including the stabilization of loose fill slopes

evaluation of approaches to calculate debris flow parameters for hazard assessment abstract many different runout prediction methods can be applied to estimate the mobility of future debris flows during hazard assessment the present article reviews the empirical analytical simple flow routing and numerical techniques all these techniques were applied to back calculate a debris flow which occurred in 1982 at la guingueta catchment in the eastern pyrenees a sensitivity analysis of input parameters was carried out while special attention was paid to the influence of rheological parameters we used the voellmy fluid rheology for our analytical and numerical modelling since this flow resistance law coincided best with field observations the simulation results indicated that the basal friction coefficients rather affect the runout distance while the turbulence terms mainly influence flow velocity a comparison of the velocity computed on the fan showed that the analytical model calculated values similar to the numerical ones the values of our rheological parameters calibrated at la guingueta agree with data back calculated for other debris flows empirical relationships represent another method to estimate total runout distance the results confirmed that they contain an important uncertainty and they are strictly valid only for the conditions which were the basis for their development with regards to the simple flow routing algorithm this methods could satisfactorily simulate the total area affected by the 1982 debris flow but it was not able to directly calculate total runout distance and velocity finally a suggestion on how different runout prediction methods can be applied to generate debris flow hazard maps is presented taking into account the definition of hazard and intensity the best choice would be to divide the resulting hazard maps into two types final hazard maps and preliminary hazard maps only the use of numerical models provided final hazard maps because they could incorporate different event magnitudes and they supplied output values for intensity calculation in contrast empirical relationships and flow routing algorithms or a combination of both could be applied to create preliminary hazard maps the present study only focussed on runout prediction methods other necessary tasks to complete the hazard assessment can be looked up in the guidelines for landslide susceptibility hazard and risk zoning included in this special issue

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

momentum transfer and friction in the debris of rock avalanches when a mass of loose dry purely frictional material slides down an incline after release at a given velocity the runout the distance the centre of gravity of the displaced mass moves from its initial position depends on momentum transfer within the mass this can be estimated from the profile of the debris accumulation which also allows more accurate calculation of apparent angles of sliding friction in rockfall avalanches the apparent extreme mobility of the elm and frank slides typical rockfall avalanches is explained by momentum transfer in a loose dry purely frictional material with an angle of friction of 30 key words mass wasting momentum transfer landslide accumulation rock avalanche runout distance

field measurement of basal forces generated by erosive debris flows 1 it has been proposed that debris flows cut bedrock valleys in steeplands worldwide but field measurements needed to constrain mechanistic models of this process remain sparse due to the difficulty of instrumenting natural flows here we present and analyze measurements made using an automated sensor network erosion bolts and a 15 24 cm by 15 24 cm force plate installed in the bedrock channel floor of a steep catchment these measurements allow us to quantify the distribution of basal forces from natural debris flow events that incised bedrock over the 4 year monitoring period 11 debris flow events scoured the bedrock channel floor no clear water flows were observed measurements of erosion bolts at the beginning and end of the study indicated that the bedrock channel floor was lowered by 36 to 64 mm the basal force during these erosive debris flow events had a large magnitude up to 21 kn which was approximately 50 times larger than the concurrent time averaged mean force high frequency greater than 1 hz fluctuating component we interpret these fluctuations as flow particles impacting the bed the resulting variability in force magnitude increased linearly with the time averaged mean basal force probability density functions of basal normal forces were consistent with a generalized pareto distribution rather than the exponential distribution that is commonly found in experimental and simulated monodispersed granular flows and which has a lower probability of large forces when the bed sediment thickness covering the force plate was greater than 20 times the median bed sediment grain size no significant fluctuations about the time averaged mean force were measured indicating that a thin layer of sediment 5 cm in the monitored cases can effectively shield the subjacent bed from erosive impacts coarse grained granular surges and water rich intersurge flow had very similar basal force distributions despite differences in appearance and bulk flow density these results demonstrate that debris flows can have strong control on rates of steepland evolution and contribute to a foundation needed for modeling debris flow incision stochastically

field and laboratory investigations of runout distances of debris flows in the dolomites eastern italian alps abstract the estimation of runout distances on fans has a major role in assessing debris flow hazards different methods have been devised for this purpose volume balance limiting topographic methods empirical equations and physical approaches data collected from field observations are the basis for developing testing and improving predictive methods while laboratory tests on small scale models are another suitable approach for studying debris flow runout under controlled conditions and for developing predictive equations this paper analyses the problem of assessing runout distance focusing on six debris flows that were triggered on july 5th 2006 by intense rainfall near cortina d ampezzo dolomites north eastern italy detailed field surveys were carried out immediately after the event in the triggering zone along the channels and in the deposition areas a fine scale digital terrain model of the study area was established by aerial lidar measurements total travel and runout distances on fans measured in the field were compared with the results of formulae from the literature empirical statistical and physically oriented and samples of sediment collected from deposition lobes were used for laboratory tests the experimental device employed in the tests consists of a tilting flume with an inclination from 0 to 38 on which a steel tank with a removable gate was installed at variable distances from the outlet a final horizontal plane works as the deposition area samples of different volumes and variable sediment concentrations were tested multiple regression analysis was used to assess the length of the deposits as a function of both the potential energy of the mass and the sediment concentration of the flow our comparison of the results of laboratory tests with field data suggests that an energy based runout formula might predict the runout distances of debris flows in the dolomites

influence of topography and volume on mobility of loess slides within different slip surfaces mobility of loess slides has been evaluated using an empirical approach based on a detailed field investigation and remote sensing image interpretation for all the loess slides the affected area increases with increasing loess slides volume from the statistical analysis it is seen that the travel distance has an increasing trend while the coefficient of friction has a decreasing trend with the increase in landslide volume landslide volume determine its travel distance and coefficient of friction that can be shown with a regression equation having simple power law form which indicates that the mobility of loess slides increases with increasing volumes by analogy the greater the energy of the sliding loess mass the stronger is the mobility of loess slide a plot of the travel distance of loess slide versus fall height shows a significant positive power law correlation indicating the increase in mobility of loess slide with fall height the negative power law correlation observed between the travel distance and slope inclination implies that the mobility decreases with the increase of slope inclination three datasets of loess slides characterized by different slip surfaces were distinguished the red clay contact landslides have the strong mobility than landslides in loess and bedrock contact

biographical sketch of a giant deciphering recent debris flow dynamics from the ohya landslide body japanese alps abstract debris flow frequency discharge and travel distance are highly catchment dependent and typically controlled by topography hydrological conditions and sediment supply as a consequence detailed and case specific investigations are needed to decipher debris flow histories in order to improve hazard mitigation this study documents past ca 10 years debris flow occurrences originating from the ohya landslide central japan by using a large set of methods including field monitoring repeat airborne lidar orthophoto interpretation and tree ring reconstructions we demonstrate that the different approaches generally agree on the occurrence of debris flows but that mismatches may exist when it comes to the assessment of areas affected by individual events these differences may even exceed the usual errors in precision inherent to each of the methods used in the present case high resolution orthophoto interpretation tends to underestimate areas affected by debris flows especially in the vertical direction in the absence of lateral movement of the channel bed and as a result of shade and areas under trees on the other hand we realize that lidar data cannot necessarily be used to distinguish local changes in topography from noise tree ring analyses can help to improve the temporal resolution of the analysis but may have limitations when it comes to the definition of areas affected by an event because of the point type nature of data we conclude that the best and most complete results are obtained by combining multiple methods to improve the spatial and temporal resolution of past debris flows and to delimit areas affected by individual events

runout analysis and mobility observations for large open pit slope failures objectively forecasting the runout of a potential open pit slope failure in addition to identifying the failure itself is a critical component of a mine s risk management plan recent losses arising from large open pit slope failures demonstrate shortcomings in current practice a dataset of 105 pit slope failures was compiled to compare open pit runout trends against established empirical runout relationships for natural landslides fahrboschung angle versus volume and fahrboschung angle versus slope angle relationships provide reasonable runout estimates open pit slopes have the advantage of removing the influence of morphological features vegetation and liquefiable substrates while controlling the travel path angle and roughness in such a controlled environment landslide mobility has a strong sensitivity to slope angle material properties and fall height and is only modestly sensitive to volume a grouping of highly mobile open pit slope cases involving weathered saturated collapsible rock

an empirical statistical model for predicting debris flow runout zones in the wenchuan earthquake area abstract rainstorm induced debris flows were remobilized from landslide debris triggered by the may 12 2008 wenchuan earthquake the resulting debris flows had very high energy and transported large amounts of loose material their peak discharge reached levels several times normal notably during the rainstorm induced debris flows of september 24 2008 in beichuan county in the wenchuan earthquake area this phenomenon was due to the presence of large amounts of loose material deposited by the earthquake induced landslides in the debris flow catchments therefore errors will occur if existing debris flow runout models are employed to assess the hazardous zones connected with debris flows in earthquake affected areas for this reason it is necessary to establish an appropriate model to predict the possible debris flow runout zones on the alluvial fans after the wenchuan earthquake debris flows triggered by the september 24 rainstorm were selected and investigated using high resolution aerial photography and spot5 imagery to extract a set of landslide deposit volumes in the debris flow catchment areas and also the dimensions of the deposition fans applying multivariate regression analysis a mathematical model was established to estimate the maximum runout distance and the width of the debris flows the validation showed that the established model was suitable for the prediction of the debris flow runout zones in the wenchuan earthquake area the results of the study will help authorities select safe sites for rehabilitation and relocation in the future and can also be used as an important basis for debris flow risk management

modelling the location of shallow landslides and their effects on landscape dynamics in large watersheds an application for northern new zealand in this study we propose a model to assess the location of shallow landslides and their impact on landscape development within a timeframe of years to decades processes that need to be incorporated in the model are reviewed then followed by the proposed modelling framework the capabilities of the model are explored through an application for a forested 17 km2 study catchment in northern new zealand for which digital elevation data are available with a grid resolution of 25 25 m the model predicts the spatial pattern of landslide susceptibility within the simulated catchment and subsequently applies a spatial algorithm for the redistribution of failed material by effectively changing the corresponding digital elevation data after each timestep on the basis of a scenario of triggering rainfall events relative landslide hazard and trajectories with runout criteria for failed slope material the resulting model will form a landslide module within the dynamic landscape evolution model lapsus the model forms a spatially explicit method to address the effects of shallow landslide erosion and sedimentation because digital elevation data are adapted between timesteps and on and off site effects over the years can be simulated in this way by visualization of the modelling results in a gis environment the shifting pattern of upslope and downslope in stability triggering of new landslides and the resulting slope retreat by soil material redistribution due to former mass movements can be simulated and assessed