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

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

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

a paleomagnetic constraint on the late cretaceous paleoposition of northwestern baja california mexico we present palaeomagnetic data for cretaceous sedimentary rocks from the el rosario formation of northwestern baja california which imply a northward displacement of 15 0 3 8 and a 30 8 4 2 clockwise rotation for the baja peninsula relative to the north american craton since late cretaceous time paired irm acquisition x ray diffraction and mossbauer spectra indicate that fine grained magnetite is the dominant magnetic mineral present with goethite and other more oxidized phases rare to absent biochemical evidence constrains the amount of diagenesis undergone by the sediments we subjected oriented samples to both progressive alternating field and thermal demagnetization and in general found univectorial magnetizations yielding a mean inclination of 44 6 and declination of 5 3 with an 95 of 2 0 the corresponding paleolatitude for these values is 26 3 1 6 most of the samples were of normal polarity which is consistent with their deposition within the upper campanian chron 33n we collected samples from younger maastrichtian sediments which yield consistent reversed directions

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

archaean basic volcanism in the eastern goldfields province yilgarn block western australia abstract petrographic petrological and geochemical studies have demonstrated the presence of three distinctive basic volcanic suites in the eastern goldfields province yilgarn block western australia these are termed the high magnesian series basalts hmsb the low magnesian series basalts lmsb and the siliceous high magnesian series basalts shmsb the hmsb and shmsb constitute differentiation series which contain both high mgo 9 5 14 wt and low mgo the hmsb and lmsb were derived from source mantle regions which were variably depleted in the incompatible elements archaean komatiites were derived from similarly depleted source regions and it is argued that the main petrogenetic difference between these three volcanic suites was the degree of partial melting from which they were derived the depleted nature of the source regions may have been induced by earlier small degree source mantle regions of the shmsb were variably enriched in the incompatible elements and water and parental magmas of the shmsb were derived from moderately hydrous conditions of partial melting the relative proportions of each basalt suite varies considerably between the layered successions examined for example the basic volcanics overlying the komatiites at kambalda are shmsb while the footwall volcanics consist predominantly of hmsb with subordinate lmsb however the norseman succession where no ultramafic volcanics are known to occur is comprised mainly of lmsb with a smaller proportion of hmsb

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

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

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

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

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

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