debris flows and debris torrents in the southern canadian cordillera in canada debris torrents also referred to as channelized debris flows occur in parts of british columbia alberta and the yukon at least 17 deaths and an estimated 100 million of damage to bridges and property can be attributed to this natural hazard the debris mainly comprises large boulders rock fragments gravel to clay sized material tree and wood mulch materials that accumulate in the mountain creeks to be susceptible to a debris torrent a creek must have a drainage area within a critical range a profile that is sufficiently steep an accumulation of debris and some form of triggering mechanism the most common triggering mechanism is an extreme water discharge which may result from a very intense rainfall or a temporary damming of the creek in western canada the resulting torrents involve masses of debris typically less than 50 000 m3 that travel down creeks at speeds between 3 and 12 m s several passive and active forms of mitigation can be used to reduce the impact of debris to

miocene extension and extensional folding in an anticlinal segment of the black mountains accommodation zone colorado river extensional corridor southwestern united states 1 recent studies demonstrate that rifts are characterized by linked tilt domains each containing a consistent polarity of normal faults and stratal tilt directions and that the transition between domains is typically through formation of accommodation zones and generally not through production of throughgoing transfer faults the mid miocene black mountains accommodation zone of southern nevada and western arizona is a well exposed example of an accommodation zone linking two regionally extensive and opposing tilt domains in the southeastern part of this zone near kingman arizona east dipping normal faults of the whipple tilt domain and west dipping normal faults of the lake mead domain coalesce across a relatively narrow region characterized by a series of linked extensional folds the geometry of these folds in this strike parallel portion of the accommodation zone is dictated by the geometry of the interdigitating normal faults of opposed polarity synclines formed where normal faults of opposite polarity face away from each other whereas anticlines formed where the opposed normal faults face each other opposed normal faults with small overlaps produced short folds with axial trends at significant angles to regional strike directions whereas large fault overlaps produce elongate folds parallel to faults analysis of faults shows that the folds are purely extensional and result from east northeast stretching and fault related tilting the structural geometry of this portion of the accommodation zone mirrors that of the black mountains accommodation zone more regionally with both transverse and strike parallel antithetic segments normal faults of both tilt domains lose displacement and terminate within the accommodation zone northwest of kingman arizona however isotopic dating of growth sequences and crosscutting relationships show that the initiation of the two fault systems in this area was not entirely synchronous and that west dipping faults of the lake mead domain began to form between 1 m y to 0 2 m y prior to east dipping faults of the whipple domain the accommodation zone formed above an active and evolving magmatic center that prior to rifting produced intermediate composition volcanic rocks and that during rifting produced voluminous rhyolite and basalt magmas

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

prediction of debris flow inundation areas using empirical mobility relationships abstract a method proposed for delineating lahar hazard zones in volcanic valleys is adapted to debris flows the original method is based on two predictive equations that relate the lahar volume to the cross sectional inundated area and to the planimetric inundated area these predictive equations were derived by combining a scaling analysis of lahar kinematics with the statistical analysis of data for 27 historical lahars this paper tests the applicability of this approach to debris flow fans forty debris flow basins in the italian alps were surveyed and data on 27 historical debris flow events were collected in the field or by means of aerial photo analysis collected data reveal that the flow area a and the planimetric area b of a debris flow are linearly correlated to the debris flow volume v on a logarithmic scale with high statistical significance moreover the computed regression equations are very similar to those obtained from other published datasets on debris flows leading to the global fitting equations a 0 08 v 2 3 and b 17 v 2 3 these predictive equations are then implemented in an automated code dflowz that delineates the inundated area on a debris flow fan on the basis of a user specified debris flow volume taking the statistical uncertainty in the prediction into account dflowz is simple reproducible and it can handle both confined and unconfined flow the model is tested against 10 historical debris flow events providing a satisfactory agreement between observed and computed inundated areas in spite of the limitations due to dem accuracy and statistical uncertainty of the regression parameters test results show that the method can be useful for practical applications

stream aquifer interactions and hyporheic exchange in gaining and losing sinuous streams 1 the irregular planform morphology of rivers leads to formation of hyporheic zones along its banks this study investigates how hyporheic exchange in stream banks whose planform is idealized as sinusoidal is affected by net gains from and net losses of water to the adjacent aquifer these effects are studied via numerical modeling of groundwater flow adjacent to sinuous channels across a broad range of sinuosity and gain loss magnitude hyporheic zone areas and fluxes both decrease exponentially with increasing magnitude of net gain or loss relative to the case where the stream has no net flux of water neutral residence time through the hyporheic zone also decreases with gain loss magnitude the hyporheic zones become constrained near the apex of bends indicating that these areas could be hot spots for mixing and biogeochemical processing hyporheic zones in channels with smaller sinuosity are more prone to hyporheic flux and area reduction while very sinuous channels are able to maintain a hyporheic zone even under largely losing or gaining conditions equations fitted to the suite of simulation results allow for prediction of hyporheic flux area and residence time on the basis of aquifer hydraulic conductivity channel sinuosity and the ratio of along valley and across valley mean head gradients

role of hydraulic diffusivity in the decrease of weathering rates over time summary springs emerging within massifs of crystalline rocks were monitored for discharge rate q and the q values combined with geomorphic and hydrographic parameters in a hydrologic model to calculate hydraulic conductivity k and effective porosity n e of the spring watersheds the spring waters several borehole waters and rain water were analyzed for major dissolved compounds strontium and isotopes 18 o 2 h 13 c and 87 sr 86 sr with a shift to less negative values 18 o and 2 h were fitted by a line approximately parallel to the gmwl but no significant dependence on altitude was found the 18 o and 2h values correlate better with those of precipitation amount the 87 sr 86 sr ratios in drilled well waters correlate positively with the depth of water circulation reported in the borehole logs the corresponding regression equations were used to extrapolate the depth of hydraulic circuits within the spring watersheds the previous data together with groundwater travel times calculated by a water balance model and with reactions of granite metassediment plagioclase and biotite precipitating halloysite gibbsite and vermiculite were assembled in a mass balance model to calculate solute flux weathering rates of plagioclase w pl the w pl s were described as a function of d k n e where d is the hydraulic diffusivity the discrepancies between the w pl values and solid state rates based on the differences between elemental isotopic and mineral compositions measured in present day regoliths and in the assumed protolith were assigned to a decrease in d over time from values in the protolith to values in the weathered aquifer

transient modeling of regional rainfall triggered shallow landslides this study investigates the transient modeling of regional rainfall triggered shallow landslides in unsaturated soil using the richards equation to model shallow landslides within a distributed regional scale framework infinite slope stability analysis coupled with the hydrological model with consideration of the fluctuation of time dependent pore water pressure and the soil water characteristic curve proposed by van genuchten was developed the validity of the proposed model is established through several test problems by comparing the numerical results with the analytical solutions a new procedure to set up wide range shallow landslide analysis and to integrate regional distribution variations for input data such as geology groundwater level hydrogeological characteristics and rainfall intensity and duration was presented the results obtained demonstrate that the computed distribution of the safety factor is consistent with the distribution of actual landslides in addition the fluctuation of pore water pressure in unsaturated soil dominates the stability of landslides during typhoons accompanied by heavy rainfall the findings observed in this study are a fundamental contribution to environmental effects for landslides in areas with higher occurrence and vulnerability to extreme precipitation

hydrometeorological and landuse attributes of debris flows and debris floods during typhoon toraji july 29 30 2001 in central taiwan abstract the 921 chi chi earthquake a 7 5 m earthquake with center located near chi chi of nan tou county occurred on september 21 1999 and caused more than 2400 fatalities and totaling billions of dollars losses due to destruction and damages to private and public buildings roads bridges and hydraulic structures in central taiwan this 921 chi chi earthquake also triggered close to 26 000 landslides with a total area of 15 977 ha and severely disturbed mountain slopes thus setting the conditions for occurrence of more landslides and other related disasters post earthquake watershed restoration works progressed without disruptions by major typhoon rainstorms until july 29 30 2001 when typhoon toraji hit eastern and central taiwan with heavy rainfall having peak hourly intensity exceeding 70 mm h this rainstorm caused several major debris flows and debris floods that destroyed or severely damaged dams roads bridges dikes and houses in addition to causing 103 casualties 111 missing presumed dead 189 injured this study 1 explores the characteristics and impacts of debris flows floods and 2 investigates hydrometeorological and land use attributes of debris flows and debris floods associated with this typhoon toraji in central taiwan debris floods different from more familiar debris flows are extreme peak streamflows containing large quantities of muds rocks and debris normally occurring in third and fourth order watersheds data analysis and field investigations revealed that the disastrous debris flows and debris floods during typhoon toraji were essentially caused by very heavy rainfalls on inherently unstable mountain slopes that were loosened further earlier by the 921 chi chi earthquake the extremely intense rainfall of typhoon toraji provided not only additional materials by creating new and reactivating or enlarging old landslides but also high peak stream flows required for occurrence of debris flows and debris floods the destruction and damaging power of debris flows and debris floods witnessed during typhoon toraji suggests that the effectiveness of engineering structures for disaster prevention is limited for disaster mitigation it is required to have more comprehensive strategies such as 1 land use zoning that regulates and restricts human encroachment on hazardous areas and 2 implementation of evacuation drills and relocation plan for people currently living in the hazardous zones

displacement geometry in the volume containing a single normal fault fault displacements measured in coal mines and from seismic data are used to develop a model describing the near field displacements associated with an ideal single normal fault displacement on a fault surface ranges from a maximum at the center of the fault to zero at the edge or tip line the tip line is elliptical with the shorter axis of the ellipse parallel to the displacement direction contours of equal displacement form concentric ellipses centered on the point of maximum displacement displacement gradients vary with fault size and with mechanical properties of host rock fault radius to maximum displacement ratios range from 5 to 500 plotting of displacement contour diagrams and knowledge of displacement gradients are useful in interpreting seismic reflectio data both for quality control of interpretations and for quantitative extrapolation of limited data displacements associated with faulting decrease systematically with increasing distance along the normal to the fault surface this decrease is seen as reverse drag in both hanging wall and footwall hanging wall rollover and tilting of the reflectors cannot be used to distinguish listric from planar normal faults even where fault block rotation can be demonstrated neither listric fault geometry nor a flat detachment surface is geometrically necessary because faulting is accommodated by ductile deformation rigid fault bounded blocks cannot exist except in some special circumstances related to a free surface the displacements within the rock volume affected by a single fault are not simply related to regional extension apparent horizontal extension by faulting varies from one layer to another and a significant proportion of the extension in a basin may be due to ductile deformation

effects of jackson lake dam on the snake river and its floodplain grand teton national park wyoming usa in 1906 the bureau of reclamation created jackson lake dam on the snake river in what later became grand teton national park the geomorphic hydrologic and vegetation adjustments downstream of the dam have yet to be documented after a larger reservoir was completed further downstream in 1957 the reservoir release schedule from jackson lake dam was changed in a manner that lowered the magnitude and frequency of floods the stability of the snake river exhibited a complex response to the change in flow regime close to major tributaries the snake river increased in total sinuosity and rates of lateral channel migration away from the influence of tributaries the river experienced fewer avulsions and a decrease in sinuosity vegetation maps were constructed from 1945 and 1989 aerial photography and field surveys using these data we determined how vegetation is directly related to the number of years since each portion of the floodplain was last occupied by the channel the vegetation has changed from a flood pulse dominated mosaic to a more terrestrial like pattern of succession changes in the snake river and its floodplain have direct implications on bald eagle habitat moose habitat fish habitat safety of rafting and canoeing and biodiversity at the community and species levels

hydraulic head response of a confined aquifer influenced by river stage fluctuations and mechanical loading summary the response to river stage fluctuation of a drilled well penetrating a confined aquifer was simulated using a stream aquifer interaction algorithm because the confined aquifer is overlaid by a water table aquifer the algorithm was coupled with formulae used to correct the heads for mechanical loading the coupling of stream aquifer interaction and mechanical loading models was tried for the first time in this study the test site was a drilled well installed on the montalto uffugo aquifer located at the calabria university groundwater test field calabria region south of italy this aquifer comprises a 44 m thick sand bank bounded on bottom and top by clay layers and covered by a 7 m thick sandy conglomerate being adjacent to the mavigliano river overall the head changes caused by a river stage raise represented a contribution of 49 3 57 8 to the total head while mechanical loading accounted for the remaining 50 7 32 2 the loading was triggered by a sequence of short spaced rainfall events lasting for a total of 167 days which caused recharge to the unconfined aquifer thickening the water column by some 3 1 m

evolution of the hourglass structures in the laminaria high timor sea implications for hydrocarbon traps abstract in cross section an hourglass structure can be visualized as an older horst block and superimposed younger graben bounding faults of the horst and graben blocks represent separate conjugate fault systems formed by two distinct episodes of extension in the timor sea during late jurassic early cretaceous 1st phase and middle miocene pliocene 2nd phase with an 120 my hiatus of limited or no fault activity in between horst blocks were formed by the 1st phase of extension and buried post deformation with the onset of the 2nd phase of extension the hourglass geometry began to form by nucleation of the graben bounding faults in the shallow sedimentary section in isolation from the horst bounding faults location of the graben is biased by the buried horst block and graben bounding faults grew down dip from the shallow locus of nucleation toward the underlying horst block on which only minor reactivation occurred detachment of the two systems in this way was predominantly controlled by the first order mechanical layering a thick shale rich ductile layer separates the horst and graben bounding fault systems and acts as a barrier to vertical fault propagation confinement of the graben bounding faults into the shallow section was also facilitated by outer arc style extension due to lithospheric flexure controlling the 2nd phase strain in the region the complex evolution history and the composite nature of the hourglass structures resulted in systematic along dip variation of displacement this variation predominantly relates to syn kinematic deposition and location of fault tips that are controlled by the ductile layer the presented evolution model of the hourglass structures concentrates fault tips and related stress perturbation onto the top seal and is likely to be detrimental to top seal integrity

occurrence and development of folding related to normal faulting within a mechanically heterogeneous sedimentary sequence a case study from inner moray firth uk folds associated with normal faults are potential hydrocarbon traps and may impact the connectivity of faulted reservoirs well calibrated seismic reflection data that image a normal fault system from the inner moray firth basin offshore scotland show that folding was preferentially localized within the mechanically incompetent lower middle jurassic pre rift interval comprising interbedded shales and sandstones and within upper jurassic syn rift shales upward propagation of fault tips was initially inhibited by these weak lithologies generating fault propagation folds with amplitudes of c 50 m folds were also generated or amplified by translation of the hanging wall over curved convex upward fault planes these fault bends resulted from vertical fault segmentation and linkage within mechanically incompetent layers the relative contributions of fault propagation and fault bend folding to the final fold amplitude may vary significantly along the strike of a single fault array in areas where opposite dipping conjugate normal faults intersect the displacement maxima are skewed upwards towards the base of the syn rift sequence i e the free surface at the time of fault initiation and significant fault propagation folding did not occur these observations can be explained by high compressive stresses generated in the vicinity of conjugate fault intersections which result in asymmetric displacement distributions skewed towards the upper tip with high throw gradients enhancing upward fault propagation our observations suggest that mechanical interaction between faults in addition to mechanical stratigraphy is a key influence on the occurrence of normal fault related folding and controls kinematic parameters such as fault propagation slip ratios and displacement rates

climate change effects on landslides along the southwest coast of british columbia abstract antecedent rainfall and short term intense rainfall both contribute to the temporal occurrence of landslides in british columbia these two quantities can be extracted from the precipitation regimes simulated by climate models this makes such models an attractive tool for use in the investigation of the effect of global warming on landslide frequencies in order to provide some measure of the reliability of models used to address the landslide question the present day simulation of the antecedent precipitation and short term rainfall using the daily data from the canadian centre for climate modelling and analysis model cgcm is compared to observations along the south coast of british columbia this evaluation showed that the model was reasonably successful in simulating statistics of the antecedent rainfall but was less successful in simulating the short term rainfall the monthly mean precipitation data from an ensemble of 19 of the world s global climate models were available to study potential changes in landslide frequencies with global warming most of the models were used to produce simulations with three scenarios with different levels of prescribed greenhouse gas concentrations during the twenty first century the changes in the antecedent precipitation were computed from the resulting monthly and seasonal means in order to deal with models suspected difficulties in simulating the short term precipitation and lack of daily data a statistical procedure was used to relate the short term precipitation to the monthly means the qualitative model results agree reasonably well and when averaged over all models and the three scenarios the change in the antecedent precipitation is predicted to be about 10 and the change in the short term precipitation about 6 because the antecedent precipitation and the short term precipitation contribute to the occurrence of landslides the results of this study support the prediction of increased landslide frequency along the british columbia south coast during the twenty first century

stress triggering of conjugate normal faulting late aftershocks of the 1983 ms 7 3 borah peak idaho earthquake the 1984 devil canyon sequence was a late aftershock sequence of the 28 october 1983 ms 7 3 borah peak idaho earthquake the sequence began on 22 august 1984 with the ml 5 8 devil canyon earthquake which nucleated at a depth of 12 8 0 7 km between the surface traces of two normal faults the challis segment of the lost river fault and the lone pine fault two hundred thirty seven aftershocks were recorded by a temporary array during a 3 week period their focal mechanisms and hypocenter distribution define a cross sectional v pattern whose base corresponds to the ml 5 8 event whose tips correspond to the exposed fault traces and whose sides define two planar fault zones oriented n25 w 75 sw challis fault segment and n39 w 58 ne lone pine fault this pattern describes a graben bounded by conjugate normal faults temporal aspects of the devil canyon sequence provide strong evidence that slip on conjugate normal faults occurs sequentially aftershocks occurred primarily along the challis segment until the occurrence of the 8 september 1984 ml 5 0 earthquake along the lone pine fault after which aftershocks primarily occurred along this fault these observations are consistent with worldwide seismologic and geologic observations and with physical andmore numerical models of conjugate normal faulting aftershocks of the devil canyon sequence occurred immediately northwest of the ml 5 8 devils canyon earthquake which itself was immediately northwest of the thousand springs segment of the lost river fault the fault that slipped in association with the ms 7 3 borah peak earthquake coulomb failure stress analysis indicates that stress increases resulting from both the borah peak mainshock and devil canyon ml 5 8 earthquake were sufficient to induce failure on the lone pine fault these space time patterns suggest that conjugate normal faults may transfer stress or accommodate stress changes at the terminations of major normal faults in the basin and range province less

predicting the probability and volume of postwildfire debris flows in the intermountain western united states empirical models to estimate the probability of occurrence and volume of postwildfire debris flows can be quickly implemented in a geographic information system gis to generate debris flow hazard maps either before or immediately following wildfires models that can be used to calculate the probability of debris flow production from individual drainage basins in response to a given storm were developed using logistic regression analyses of a database from 388 basins located in 15 burned areas located throughout the u s intermountain west the models describe debris flow probability as a function of readily obtained measures of areal burned extent soil properties basin morphology and rainfall from short duration and low recurrence interval convective rainstorms a model for estimating the volume of material that may issue from a basin mouth in response to a given storm was developed using multiple linear regression analysis of a database from 56 basins burned by eight fires this model describes debris flow volume as a function of the basin gradient aerial burned extent and storm rainfall applications of a probability model and the volume model for hazard assessments are illustrated using information from the 2003 hot creek fire in central idaho the predictive strength of the approach in this setting is evaluated using information on the response of this fire to a localized thunderstorm in august 2003 the mapping approach presented here identifies those basins that are most prone to the largest debris flow events and thus provides information necessary to prioritize areas for postfire erosion mitigation warnings and prefire management efforts throughout the intermountain west

volcaniclastic debris flows at la fossa volcano vulcano island southern italy insights for erosion behaviour of loose pyroclastic material on steep slopes abstract this paper describes a qualitative model of erosion of loose volcaniclastic material on steep slopes of la fossa cone vulcano island italy that generates small volume debris flows the loose volcaniclastic cover rests on an almost impermeable substratum which comprises a fine grained hydromagmatic tuff morphologically three sectors were distinguished 1 a water supply zone slope 32 where rain water is enriched in mud and concentrated in the initiation zone 2 an initiation zone or source area sensu stricto slope with 30 where debris flows form and 3 a transport and deposition zone where debris flows deposited levees and terminal lobes slope 30 main episodes of erosion of loose volcaniclastic cover and debris flow generation occur in response to thunderstorms the erosion of tuff from superficial water added a significant amount of fines mud fraction to the initiating flows debris flow stoppage on steep slopes was interpreted as the result of a loss of mass estimated between 35 and 53 of total mass to form levees from field and laboratory data the density of debris flows was estimated at about 1950 kg m3 morphological data matrix texture mass number nm and clay content of debris flow deposits suggest that they were deposited by saturated granular slurries

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

gully recharge rates and debris flows a combined numerical modeling and field based investigation haida gwaii british columbia abstract rainfall snowmelt and or other mass movements are possible triggers to initiate debris flows in supply limited landscapes clastic and organic materials together termed debris accumulate in the gully via various geomorphic processes that occur on gully sidewalls the conceptualization of this phenomenon has been termed the gully recharge rate with several recent field studies measuring such rates in coastal british columbia in the present study a simple numerical model is introduced to estimate debris flow volumes in haida gwaii british columbia based on debris flow recurrence intervals gully recharge rates and factors affecting deposition of debris flow material debris flow volumes obtained in model runs are somewhat lower than field based values by about half which is a reasonable result for this exploratory study the annual erosion rate clastic material for debris flows in the model run is 0 031 mm yr 1 this value is about 0 57 of the field based value and is lower than the erosion rate for debris slides in haida gwaii of 0 1 mm yr 1 deposition of debris flows in the model occurs in 60 of cases due to a decrease in channel gradient with deposition resulting from high stream junction angles being less common locations for initiation of debris flow deposition were situated in stream orders 3 and 4 in 60 of cases sensitivity analysis shows that in comparison to other model variables recharge rate has the greatest effect on the statistics and frequency distributions of debris flow volumes and total debris flow volume summation of all debris activity in a basin over the study time period

on the use of the boussinesq equation for interpreting recession hydrographs from sloping aquifers 1 the method of recession analysis proposed by brutsaert and nieber 1977 remains one of the few analytical tools for estimating aquifer hydraulic parameters at the field scale and beyond in the method the recession hydrograph is examined as dq dt f q where q is aquifer discharge and f is an arbitrary function the observed function f is parameterized through analytical solutions to the one dimensional boussinesq equation for unconfined flow in a homogeneous and horizontal aquifer while attractive in its simplicity as originally presented it is not applicable to settings where slope is an important driver of flow or where hydraulic parameters vary greatly with depth we compare analytical solutions to the linearized one dimensional boussinesq equation for a sloping aquifer to numerical solutions of the full nonlinear equation the behavior of the nonlinear boussinesq equation is also assessed when the aquifer is heterogeneous wherein the lateral saturated hydraulic conductivity k varies as a power law with height z above the impermeable layer k zn n constant 0 all of the analytical solutions differ in key aspects from the nonlinear solution when plotted as dq dt f q and thus are inappropriate for a brutsaert and nieber type analysis however new analytical solutions for a sloping aquifer are derived empirically from the numerical simulations that are applicable during the late period of recession when the recession curve converges to dq dt aqb where b 2n 1 n 1 and a is a function of the dimensions and hydraulic properties of the aquifer

geomorphic coupling between hillslopes and channels in the swiss alps the coupling relationships between hillslope and channel network are fundamental for the understanding of mountainous landscapes evolution here we applied dendrogeomorphic methods to identify the hillslope channel relationship and the sediment transfer dynamics within an alpine catchment at the highest possible resolution the schimbrig catchment is located in the central swiss alps and can be divided into two distinct geomorphic sectors to the east the schimbrig earth flow is the largest sediment source of the basin while to the west the rossloch channel network is affected by numerous shallow landslides responsible for the supply of sediment from hillslopes to channels to understand the connectivity between hillslopes and channels and between sources and sink trees were sampled along the main rossloch stream on the schimbrig earth flow and on the rossloch depositional area geomorphic observations and dendrogeomophic results indicate different mechanisms of sediment production transfer and deposition between upper and lower segments of the channel network in the source areas upper part of the rossloch channel system sediment is delivered to the channel network through slow movements of the ground typical of earth flow shallow landslides and soil creep contrariwise in the depositional area lower part of the channel network the mechanisms of sediment transfer are mainly due to torrential activity floods and debris flows tree analysis allowed the reconstruction of periods of high activity during the last century for the entire catchment the collected dataset presents a very high temporal resolution but we encountered some limitations in establishing the source to sink connectivity at the catchment wide scale despite these uncertainties for decennial timescales the results suggest a direct coupling between hillslopes and neighbouring channels in the rossloch channel network and a de coupling between sediment sources and sink farther downstream with connections possible only during extraordinary events

three dimensional geometry and growth of conjugate normal faults abstract good quality 2 d and 3 d seismic reflection data from the timor sea are used to determine the threedimensional geometry displacement patterns and development of intersecting conjugate normal faults these data are supplemented by data from previous physical modelling studies conjugate structures which comprise two intersecting opposed dipping normal faults or fault sets form synchronously on a geological time scale and develop due to the incidental intersection of the faults factors which affect both the formation and imaging of these structures include the fault density the spatial distribution of opposed dipping faults the seismic resolution and the vertical extent of the imaged fault data large conjugate structures grow from smaller ones larger conjugates are associated with more numerous and larger faults than small structures on the scale of the seismic data fault throws range from ca 10 400 m synchronous fault movements are accommodated by a reduction of displacements on discrete fault surfaces towards the fault intersection zone and a corresponding increase in ductile strain of this region high strains in the volume proximal to the fault intersection zone are expressed as thinning of stratigraphic units between the conjugate faults and are believed to be accommodated by numerous small sub seismic faults intersection of two opposed dipping faults does not prevent their continued synchronous movement and does not result in mechanical locking of the system

an empirical approach to studying debris flows implications for planetary modeling studies 1 high resolution images acquired by the mars global survey mars orbiter camera show gullies on the walls of impact craters and valley systems on mars depositional aprons associated with these gullies have been interpreted by malin and edgett 2000 to be characteristic of debris flow and to indicate the presence of sources of liquid water at shallow depths below the martian surface by focusing on a terrestrial debris flow we test the application of chezy type modeling to provide more direct estimates of the dynamics of proposed debris flows on mars traditionally planetary scientists constrained by available remotely sensed data have used a range of flow models to gain insights from deposits into the behavior and rheologic nature of features such as lava flows debris flows and gravity driven flows on the basis of these model results broad interpretations of the physics governing flows of granular materials have been tempting based on limited field derived data this study tests and validates the extent to which the absolute value and relative variations of empirical parameters derived from the chezy type models describe the behavior of the general s slide debris flow 38 24 n 78 23 w in madison county virginia the results indicate that extreme caution must be taken when interpreting model results for turbulent flows of granular materials we obtained high precision topographic profiles superelevation data sedimentary facies and sedimentary textural properties over the debris flow this study focuses on the empirical parameter c whose value gauges energy dissipation in a flow thereby called flow resistance using field observations both variations and absolute values of c along the debris flow have been computed using two approaches 1 assuming constant volumetric flow rate q where only topography and high resolution images are required to compute channel dimensions and 2 a variable q calculated using field derived data assuming near newtonian flow conditions in the debris flow estimated values of c range from 0 035 to 0 099 when q is fixed c decreases as a function of distance downstream when q varies and c is computed from field derived flow speeds its value tends to increase downstream slightly these opposite results have been compared to the field observations to determine which best describes the behavior of the flow the variations in c downstream obtained using the flow speeds are most consistent with the geomorphic evidence for erosion of material by the debris flow and the presence of bends in the channel the average values of c 0 036 0 33 for the general s slide have been compared with computed c values for newtonian and near newtonian flows to assess the rheology of the flow during emplacement our terrestrial study demonstrates that advances in understanding of the dynamics of debris flows on the mars depends on obtaining debris flow speeds in addition to channel topography and flow thickness rather than just on channel topography flow thickness and the assumption that q is constant mars orbiter camera moc and mars observer laser altimeter mola data can be used to derive channel topography flow thickness and possibly flow speeds such data will provide more direct estimates of the dynamics of debris flows on mars than are currently available

pattern of normal faulting in the gediz graben sw turkey hanging wall deformation of the fault systems controlling the southern margin of the gediz graben were investigated separately within the plio quaternary and neogene predominantly miocene deposits of the graben fill fault styles observed in both packages share many similarities in terms of geometry and comprise conjugate fault sets that show clustering of strike orientations predominantly around wnw ese but also sw ne and nw se directions the main difference between the two units is observable in terms of fault dips and rake of the slickenside lineations measured on the exposed fault planes both measurements show a uni modal distribution for the plio quaternary deposits but a tri modal distribution for the neogene deposits this variation is probably related to the geometrical modification of the older faults by the process of domino style back rotation in the hanging wall of higher order faults similarities among the two units are not limited to geometrical aspects of the fault systems but also counts for the orientation of the principal stress axes that controlled the deformation during the deposition of each sedimentary package inversion of the fault slip data showed that approximately n s oriented extension which varies in the range of nnw sse and nne ssw controlled the faulting during the accumulation of the entire graben fill with almost no evidence of change in the state of stress during the graben evolution however some heterogeneity in terms of stress field is observable among the fault systems formed within the same time frame this heterogeneity is probably related to poorly defined direction of extension in the graben indeed low ratio in the order of 0 25 suggests that 2 and 3 are close in magnitudes and the direction of extension is not well constraint with a potential of 2 3 axes permutations local stress field anomalies related to fault segment interaction could also contribute to the observed heterogeneity

the impact of climate change human interference scale and modeling uncertainties on the estimation of aquifer properties and river flow components summary within the period 1978 2006 climate change and human interferences produced noticeable impacts on the hydrology of a small watershed known as the beca river basin climate change was characterized by a persistent raise in temperature 0 78 c decade 1 and a drop in the annual rainfall 300 mm decade 1 human interferences included the construction of a dam for electric power generation in 1998 and since then the transference of beca river flows from the dam lake to the adjacent t mega river the impacts on catchment hydrology comprised a decline of aquifer hydraulic conductivity and effective porosity by approximately one order of magnitude related to a water table lowering of about 17 m within the bedrock aquifer composed of weathered and fractured hercynian granites and paleozoic metassediments and of saprolite layers derived therefrom aquifer property estimates were compared across spatial scales namely the beca river and the nested sub basins scale sub basin aquifers are more porous and permeable than the basin aquifer because corresponding hydraulic circuits are shallower comparisons were also made between aquifer properties derived from measured and simulated stream flows which revealed effects of modeling uncertainties on the results river flows also suffered a substantial decrease in the course of climate change and human interference especially the overland flows 4 5 decrease and the base flows 2 3 decrease the inter flows were less affected 1 3 decrease because they were partly fed with water from the aquifer storage which in turn underwent depletion the hydrologic changes in the beca river basin anticipate important impacts on the local use of natural water in this context the aforementioned water table lowering may have caused limited access to shallow groundwater for activities such as crop irrigation from dug wells whereas the severe decline in overland flows and base flows had certainly reduced the availability of surface water for the refilling of dam lakes and of groundwater for the supply of public and private boreholes

dams and geomorphology research progress and future directions dams impose changes of flow and sediment transfer that drive changes of channel form along the downstream regulated river these changes have been described for more than 50 years but process form relationships have only been advanced with the establishment of a conceptual framework during the 1970s and then the extension of monitoring data and advancement of remote sensing technologies particularly over the past 20 years this paper reviews these developments and identifies three influential themes i channel dynamics ii the role of riparian vegetation and iii channel change as the driver of ecological change changes can be rapid in semi arid regions but elsewhere relaxation periods may extend to millenia in these latter cases regime or steady state models should be replaced by models of transient states applied to the reach scale in order to respond to the needs of river managers over decadal timescales

listric versus planar normal fault geometry an example from the eisenstadt sopron basin e austria in a gravel pit at the eastern margin of the eisenstadt sopron basin a satellite of vienna basin austria neogene sediments are exposed in the hanging wall of a major normal fault the anticlinal structure and associated conjugated secondary normal faults were previously interpreted as a rollover anticline above a listric normal fault the spatial orientation and distribution of sedimentary horizons and crosscutting faults were mapped in detail on a laser scan of the outcrop wall subsequently in order to assess the 3d distribution and geometry of this fault system a series of parallel ground penetrating radar gpr profiles were recorded behind the outcrop wall both outcrop and gpr data were compiled in a 3d structural model providing the basis for a kinematic reconstruction of the fault plane using balanced cross section techniques however the kinematic reconstruction results in a geologically meaningless normal fault cutting down and up section additionally no evidence for a weak layer serving as ductile detachment horizon i e salt or clay horizon can be identified in stratigraphic profiles instead the observed deflection of stratigraphic horizons may be caused by a displacement gradient along a planar master fault with a maximum displacement in the fault centre decreasing towards the fault tips accordingly the observed deflection of markers in the hanging wall and in a nearby location in the footwall of the normal fault is interpreted as large scale fault drag along a planar fault that records a displacement gradient instead of a rollover anticline related to a listric fault

a new model for assessing trap integrity and oil preservation risks associated with postrift fault reactivation in the timor sea based on comparisons between structural histories and the distribution of current and paleo oil accumulations it is proposed that the partitioning of postrift strain between faults in relation to trap geometry was critical in determining oil preservation during neogene fault reactivation in the timor sea most of the trap bounding faults in the region have been reactivated however the distribution of postrift displacements is heterogeneous and depends heavily on rift phase fault size location and interaction with nearby faults preferential localization of postrift strain onto larger faults in the population resulted in the partial protection of some fault bound traps with favorable geometries but promoted breaching of others oil columns tend to be preserved where the crest of the trap is bound by a fault segment that has accommodated relatively low postrift displacements less than about 60 m 196 ft during reactivation typically where smaller rift faults are overlapped by larger rift faults complete loss of oil column is generally observed where the crest of the trap is bound by a typically large fault with high postrift displacements greater than about 60 m 196 ft where faults with high postrift displacements are located downdip of the trap crest hydrocarbon columns are preserved down to the depth of the intersection between this fault and the top reservoir horizon a simple trap integrity model based on these observations was found to be largely consistent with a database of 69 drilled traps in the region the mechanisms and models discussed in this study are likely to apply to other petroleum systems where fault reactivation represents a risk to hydrocarbon preservation

modeling rock weathering in small watersheds summary many mountainous watersheds are conceived as aquifer media where multiple groundwater flow systems have developed toth 1963 and as bimodal landscapes where differential weathering of bare and soil mantled rock has occurred wahrhaftig 1965 the results of a weathering algorithm pacheco and van der weijden 2012a 2014 which integrates topographic hydrologic rock structure and chemical data to calculate weathering rates at the watershed scale validated the conceptual models in the river sordo basin a small watershed located in the marao cordillera north of portugal the coupling of weathering groundwater flow and landscape evolution analyses as accomplished in this study is innovative and represents a remarkable achievement towards regionalization of rock weathering at the watershed scale the river sordo basin occupies an area of approximately 51 2 km 2 and was shaped on granite and metassediment terrains between the altitudes 185 1300 m the groundwater flow system is composed of recharge areas located at elevations 700 m identified on the basis of 18 o data discharge cells comprehend terminations of local intermediate and regional flow systems identified on the basis of spring density patterns infiltration depth estimates based on 87 sr 86 sr data and spatial distributions of groundwater ph and natural mineralization intermediate and regional flow systems defined where infiltration depths 125 m develop solely along the contact zone between granites and metassediments because fractures in this region are profound and their density is very large weathering is accelerated where rocks are covered by thick soils being five times faster relative to sectors of the basin where rocks are covered by thin soils differential weathering of bare and soil mantled rock is also revealed by the spatial distribution of calculated aquifer hydraulic diffusivities and groundwater travel times

geomorphological origin of recession curves 1 we identify a previously undetected link between the river network morphology and key recession curves properties through a conceptual physical model of the drainage process of the riparian unconfined aquifer we show that the power law exponent of dq dt vs q curves is related to the power law exponent of n l vs g l curves which we show to be connected to hack s law where l is the downstream distance from the channel heads n l is the number of channel reaches exactly located at a distance l from their channel head and g l is the total length of the network located at a distance greater or equal to l from channel heads using digital terrain models and daily discharge observations from 67 us basins we find that geomorphologic estimates match well the values obtained from recession curves analyses finally we argue that the link between recession flows and network morphology points to an important role of low flow discharges in shaping the channel network

estimating the mud depth of debris flow in a natural river channel a theoretical approach and its engineering application mud depth of debris flow is an essential parameter for assessing the hazard magnitude in an event however direct prediction of mud depth in a natural river channel is a scientific challenge because current methods often treat the complex relief of bed surface as a rectangular one which makes the prediction illogical in this paper we propose a new theoretical approach the so called numerical integral method based approach for estimating the maximum mud depth of debris flow at a complex cross section in a natural river channel given a predefined peak discharge of the debris flow event the numerical integral method based iteration algorithm uses the riemann method to search for an approximate mud depth in contrast to the previous methods the presented approach addresses an important issue namely it takes into account the complex shape of the bed surface and superelevation at the bend for natural channels two cases are used to illustrate the performance and advantages of the presented approach one is a well documented event in the previous study and the other is a debris flow event after ms 8 0 wenchuan earthquake an engineering application regarding the rational design of a debris flow canal is subsequently discussed the canal was completely destroyed in a debris flow event in 2008 we used the proposed method to back analyze the mud depth and velocity in the canal it was found that the abrupt decrease of mud depth from the natural channel to the concrete canal significantly reduced the transportation capability thereby causing blockage in the canal the canal was modified and reconstructed in 2009 with suggested improvements from the proposed method and successfully transported subsequent debris flow in 2011

theoretical and experimental estimation of geometric relationship of non parallel conjugate normal faults abstract intersecting and crossing conjugate normal faults develop at different scales equations of geometric parameters of non parallel conjugate normal faults can be deduced from their trigonometric relations physical models can also be used to verify the theoretical calculations and compared with natural examples in this study we have used a theoretical approach to outline some key geometric parameters of conjugate normal faults intersection angles plunge of intersection line and vertical and horizontal distances of the intersection point etc and compared them to equivalent geometric values in scaled analogue models the comparison shows that theoretical plots used for geometric estimation of conjugate normal faults constrain reasonably the geometric parameters in natural cases data from the lufeng sag of pearl river mouth basin in the northern part of south china sea where conjugate non parallel basement faults propagate and intersect in cover units are compatible with the theoretical geometric estimation

contribution of correlation and spectral analyses to the regional study of a large karst aquifer charente france the purpose of the study is to demonstrate that correlation and spectral analyses can contribute to the regional study of a large karst aquifer an example is presented for the la rochefoucauld karst aquifer charente france different types of spatially distributed time series provide valuable spatio temporal information for the karst aquifer the available time series consist of the spring flow rates the flow rates at different locations in sinking streams the piezometric levels the electrical conductivity and temperature of the water the atmospheric pressure and the precipitation the analysis of the flow rates at the springs shows that the aquifer empties very slowly and has a large storage capacity hydrodynamic links were established between three of the four rivers flowing on the aquifer and the springs the results also demonstrate the important spatial heterogeneity of the aquifer and indicate that the most rapid flow occurs in the northern part of the aquifer hourly piezometric and electrical conductivity time series indicate that the transmissivity of the aquifer varies when some conductive channels become desaturated during the low water period the delays between the distributed recharge and the piezometric level between the localized river input and the flow rates at the springs and between the electrical conductivities in rivers and the main spring provide information on the travel times in the aquifer the observation of earth tides and barometric effects indicate that this apparently unconfined aquifer has a confined behaviour

analysis of normal fault populations in the kumano forearc basin nankai trough japan 1 multiple orientations and generations of faults from 3 d coherency mapping 1 analyses of normal faults in the kumano forearc basin of the nankai trough reveal multiple normal fault populations in a region generally thought to be under compression most faults have offsets of less than 20 m and dips of 60 70 and show no growth structures indicating that the faults were active for short periods of time the oldest generation of faults is older than 0 9 ma and strikes 50 60 the next oldest faults strike 160 170 are older than 0 44 ma and are related to local uplift along the western edge of the region the youngest faults cut the seafloor shallow faults near the se margin of the basin curve from 100 in the middle of the survey area to 145 at the se corner of the area the pattern of the two youngest fault populations is consistent with the regional stress pattern maximum horizontal stress subparallel to the trench orientations of older fault populations are caused by uplift of the underlying accretionary prism implying that the forearc basin region is not as stable as previously thought reconstruction of displacements on the youngest faults shows that the overall horizontal extension is less than 2 concentrated near the seaward edge of the basin the active normal faults distributed throughout the basin support the idea that the horizontal stress parallel to the plate convergence direction does not reach the critical stress to activate or form thrust faults and produce horizontal shortening within the shallow portion of the inner wedge

integrating topography hydrology and rock structure in weathering rate models of spring watersheds weathering rate models designed for watersheds combine chemical data of discharging waters with morphologic and hydrologic parameters of the catchments at the spring watershed scale evaluation of morphologic parameters is subjective due to difficulties in conceiving the catchment geometry besides when springs emerge from crystalline massifs rock structure must be accounted in formulas describing the area of minerals exposed to the percolating fluids for a realistic evaluation of the rates these particular features are not included in the available approaches and for that reason a new model was developed coined throw model this is a lumped approach that integrates t opography h ydrology ro ck structure and w eathering in a single algorithm the study area comprises several stream watersheds and spring sites of the vouga river basin northern portugal shaped on granites firstly the throw model couples a terrain modeling analysis with hydrologic models based on discharge rates to determine hydraulic conductivities k effective porosities ne and annual recharges vr at the stream watershed scale subsequently these parameters are used in a water balance model to estimate concomitant groundwater travel times t the mean k 4 7 3 2 10 7 m s 1 and ne 2 0 1 3 10 2 values are adopted as proxies for the spring watersheds and a firm regression equation is defined between time and stream watershed area a secondly two more runs of terrain modeling analysis are executed to extrapolate morphologic parameters for the spring watersheds the first run hinges on scaling properties of the drainage networks known as horton laws and is used to scale watershed areas across stream orders i the scaling function is described by another regression equation the second run evaluates the order of a spring watershed defined as equivalent order ieq and equated to the mean order of the surrounding stream watersheds having calculated the ieq spring watershed areas and travel times were downscaled using the regression equations a 10 km2 and t 1 4 2 8 year standing on the physical and hydrologic parameters of the spring watersheds the throw model finally calculates plagioclase weathering rates in the vicinity of the spring sites the sib model pacheco and van der weijden 1996 was used before to estimate the contribution of plagioclase dissolution to the chemical composition of these springs van der weijden and pacheco 2006 the chemical data were now coupled with k ne and t in a rate equation to estimate chemical weathering rates of plagioclase in the basin in the throw model the rate equation describes the exposed surface area as a function of fracture spacings openings and porosities pacheco and alencoao 2006 the calculated rates wpl 2 5 1 2 10 14 mol m 2 s 1 are consistent with previous reports and with results of experimental kinetic models the sib results predict formation of halloysite and gibbsite along the flow path which were indeed close to equilibrium with the dissolved al and si activities o develop a weathering model that incorporates rock structure in the rate equation o conceive a weathering model especially designed for fracture artesian springs o create a model that integrates topography hydrology rock structure and weathering

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

confluence and intersection of interacting conjugate faults a new concept based on analogue experiments abstract examination of the interaction area of conjugate faults yields evidence of a yet unknown structural pattern analogue experiments revealed the evolution of this pattern during the interaction process a fault propagating towards the highly active section of another conjugate fault becomes increasingly deflected towards the obtuse angle side of the conjugate system while approaching until joining it during this process the tip of the curved propagating fault retains its shear sense until immediately before joining with the highly active fault a process called confluence in this report under constant remote stress the deflected fault now becomes dominant a fault branch splits off at the point where deflection commences propagating straight ahead of the original direction and may dissect the former master fault alternating activity at both of the faults finally produces the known intersection patterns further studies of the proposed concept on natural examples are recommended due to the close geometric similarity of the evolutionary structural stages and natural fault patterns

relationship between polarity of extensional fault arrays and presence of detachments abstract extensional fault arrays are often dominated by a single fault vergence forming domino fault blocks the polarity of faults can be defined as synthetic or antithetic in relation to the overall shear sense across the fault system observations of the geometry of a number of field examples of extensional fault arrays vs the lithologies as a proxy for strength profile show that synthetic extensional arrays from the north sea and bristol channel basin detach on salt layers whereas examples of antithetic arrays from the north sea are found to pin out downwards and no basal detachment is present in the sacramento mountains core complex of the basin and range the major low angle detachment fault post dates antithetic shears that evolved at mid crustal level and are preserved in the granitic footwall these antithetic shears were cut by the main low angle detachment whose hanging wall disintegrated into an array of synthetic faults the kinematics of synthetic vs antithetic arrays dictate that faults within synthetic arrays must branch onto a basal detachment whereas faults within antithetic arrays may die out downwards therefore the results emphasise that fault polarity in domino arrays may be related to the boundary conditions of the fault blocks and therefore may be diagnostic of the strength profile of the faulted stratigraphy

impacts of large dams on downstream fluvial sedimentation an example of the three gorges dam tgd on the changjiang yangtze river summary under the influence of climate and human activities fluvial systems have natural ability to make adjustments so that the river hydrology sediment movement and channel morphology are in dynamic equilibrium taking the changjiang yangtze river for example in the early stages after the three gorges dam tgd began operational ten years ago the suspended sediment content ssc and fluxes in the middle and lower reaches of the river decreased noticeably at present they appear to be in a stable state on the decadal scale although the river runoff has not shown any trends the water level in the river decreased appreciably in time in the meantime channel down cutting along the thalweg almost existed throughout the river course the riverbed has turned from depositional before the dam construction to erosional afterwards in other words the riverbed had turned from being sediment sinks to sediment sources in the main channel of the changjiang between yichang and nanjing a distance of 1300 km the riverbed sedimentation mode displays strong intermediate and weak erosion depending on the closeness to the tgd

ground surface slope as a basin scale parameter a simple and relatively rapid method of determining the characteristic or typical slope of a basin is proposed the expression for the parameter which is given by savg l hsu hso2 a cos was developed from considerations of basin geometry and basic geomorphologic facts and involves only quantities that can be easily extracted from topographic maps characteristic basin slope values of 19 appalachian plateau watersheds which range in size from 7 4 to 178 2 km2 were determined by the proposed method these values were compared with corresponding values obtained by horton s intersection line method and with those derived from county soil survey reports and maps the comparisons showed very close agreement between the three sets of values indicating the high accuracy of the method developed here similar comparisons involving values determined by previous slope methods indicated that these values are at best poorly related to actual average basin slope and that most of them are incapable of detecting small differences in slope between similar watersheds moreover the proposed method significantly reduces the amount of work required by other slope methods of comparable accuracy

volcaniclastic debris flows in the clanio valley campania italy insights for the assessment of hazard potential abstract the rugged and steep slopes of the clanio valley campania southern italy mantled by volcaniclastic deposits from explosive eruptions of somma vesuvius and phlegraean fields volcanoes have a great potential for generating volcaniclastic debris flows during the well known meteorological event of may 5 6 1998 which triggered tens of debris flows causing enormous damage and casualties in the area of sarno quindici siano bracigliano sqsb the clanio valley was also affected by these hazardous phenomena debris flows were triggered by the failure of the volcaniclastic cover of the carbonate relief in the form of soil slips mainly on the sides of steep valleys slope between 26 and 45 a map of the hazard potential was created on the basis of both field and computer assisted morphometric data three classes characterised by a high medium and low hazard potential were distinguished within the higher class a better and more detailed zonation was obtained by studying the shape of the disrupted and undisrupted basins during the may 5 6 1998 event in the nearby sarno quindici siano bracigliano area this type of morphometric analysis can be applied rapidly by using a digital elevation model dem which allows a rapid investigation of large scale areas such an approach can be useful in areas characterised by similar geological and geomorphological settings

sedimentological processes in lahars insights from optically stimulated luminescence analysis abstract a lahar is a sediment laden flow capable of major destructive impacts on infrastructure and human life how lahars transport sediment is thus a key issue for understanding lahar sedimentology and behavior especially in terms of the lahar s hydraulic and rheological properties which can be substantially altered as the lahar gains or loses material during its travel in this research we analyze lahar entrainment processes by evaluating luminescence signals total photon counts from lahar sediments using blue luminescence signals blsl a portable osl reader that analyzes several grams of polymineral and polygrain size samples was applied we use data from three lahars in the tenenepanco and huiloac gorges on popocatepetl volcano mexico to elucidate the ways in which lahars may gain lose and transport sediment during flow sediment samples for luminescence analysis were taken through the full thickness of the lahar deposits at eight different sites for two lahars 1997 and 2001 and at one site for a lahar that occurred 500 yrs ago mean luminescence values obtained for the 1997 lahar help to evaluate the relationship between the lahar entrainment processes and the drainage at the different sites for the 2001 lahar this relationship was also established taking into account the channel slope the main conclusion is that luminescence signals total photon counts can be used to detect entrained material in the flow because the bulked materials modify the final osl signals the application of this type of luminescence analysis thus has the potential to provide a better understanding of sediment entrainment in these sediment laden flows

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

volume loss and deformation around conjugate fractures comparison between a natural example and analogue experiments abstract in well stratified sedimentary rocks measurement of the bedding offsets along fractures gives a value for the relative displacement at each location to restore the undeformed geometry of the layers the offset along each fracture must be cancelled restoration of the geometry enables the location of places where shortening is concentrated to be established namely at the fracture intersection and at fracture tips slow displacement during deformation is demonstrated by the growth of fibres on the fault surfaces pressure solution inside the layers is responsible for the internal strain with associated volume loss this mechanism is compatible with low strain rates giving aseismic displacements along the fractures to model rock rheology dominated by pressure solution a viscous material paraffin wax has been employed in the analogue model volume loss in nature is represented by area changes during the analogue experiments in the experiments shortening is concentrated around the fractures in exactly the same geometrical positions as in nature when the amount of displacement is different on each of the two fractures one of the fractures is observed to offset its conjugate fracture when this is the case relative timing of displacement along conjugate fractures cannot be determined without ambiguity from the observation of fracture offsets

drainage of a horizontal boussinesq aquifer with a power law hydraulic conductivity profile 1 solutions to the boussinesq equation describing drainage into a fully penetrating channel have been used for aquifer characterization two analytical solutions exist for early and late time drainage from a saturated homogeneous and horizontal aquifer following instantaneous drawdown the solutions for discharge q can be expressed as dq dt aq b where a is constant and b takes on the value 3 and 3 2 for early and late time respectively though many factors can contribute to departures from the two predictions we explore the effect of having permeability decrease with depth as it is known that many natural soils exhibit this characteristic we derive a new set of analytical solutions to the boussinesq equation for k oc z n where k is the saturated hydraulic conductivity z is the height above an impermeable base and n is a constant the solutions reveal that in early time b retains the value of 3 regardless of the value of n while in late time b ranges from 3 2 to 2 as n varies from 0 to oo similar to discharge water table height h in late time can be expressed as dh dt ch d where d 2 for constant k and d oo as n in theory inclusion of a power law k profile does not complicate aquifer parameter estimation because n can be solved for when fitting b to the late time data whereas previously b was assumed to be 3 2 however if either early or late time data are missing there is an additional unknown under appropriate conditions water table height measurements can be used to solve for an unknown parameter

assessing the potential for change in the middle yangtze river channel following impoundment of the three gorges dam abstract the geomorphic impacts of dams on downstream river channels are complex not readily predictable for specific cases but widely reported in the literature for the three gorges dam on the yangtze changjiang river in china no studies of the impact of the changed flow and sediment conditions below the dam on the behaviour of the channel were included in the pre dam feasibility report we have assembled a database of flow and sediment data for the middle yangtze river from yichang to hankou and used this to analyse changes following the closure of the dam while total flow is little affected the operating strategy for the dam that provides for storage of part of the summer high flows to maintain hydroelectric power generation in winter the low flow season is reflected in changes to the seasonal distribution of flow below the dam we calculated potential sediment carrying capacity and compared it with measured sediment concentrations for both pre and post dam conditions while channel sedimentation is indicated along the middle yangtze for pre dam conditions scour is indicated for post dam conditions highest at yichang immediately below the dam and decreasing downstream

displacement gradients on fault surfaces abstract the maximum displacements and the dimensions of single faults are systematically related and the variation in displacement from a maximum at the centre of a fault to zero at an elliptical tip line loop is described by a simple theoretically derived expression these relationships are used to examine the theoretical ranges and distributions of rates of change of displacement on fault surfaces the dimensions and maximum displacement of a fault can be estimated from a limited number of displacement gradient measurements estimates are further constrained by a knowledge of the effective shear modulus of the rocks containing a fault an understanding of displacement gradients can be applied to problems commonly encountered in mining operations and in the interpretation and use of seismic reflection data in addition to field problems a comparison of theoretical displacement gradients with measured displacement gradients from british coalfield faults shows that i fault surface ellipticities are between 1 5 and 2 5 and ii gross displacement gradients expressed as the ratio of maximum displacement long axis radius of the fault ellipse range from 0 02 to 0 002 the measured displacement gradients indicate that the shear moduli of the faulted rocks range from 3 to 11 gpa which is within the known range for coal measure rocks displacement gradients along an array of fault segments are similar to those of single faults for analysis of displacement gradients it is necessary to sum the discontinuous and continuous components of displacement in extreme cases all the displacement may be accommodated by continuous deformation

the concept of transport capacity in geomorphology the notion of sediment transport capacity has been engrained in geomorphological and related literature for over 50 years although its earliest roots date back explicitly to gilbert in fluvial geomorphology in the 1870s and implicitly to eighteenth to nineteenth century developments in engineering despite cross fertilization between different process domains there seem to have been independent inventions of the idea in aeolian geomorphology by bagnold in the 1930s and in hillslope studies by ellison in the 1940s here we review the invention and development of the idea of transport capacity in the fluvial aeolian coastal hillslope debris flow and glacial process domains as these various developments have occurred different definitions have been used which makes it both a difficult concept to test and one that may lead to poor communications between those working in different domains of geomorphology we argue that the original relation between the power of a flow and its ability to transport sediment can be challenged for three reasons first as sediment becomes entrained in a flow the nature of the flow changes and so it is unreasonable to link the capacity of the water or wind only to the ability of the fluid to move sediment secondly environmental sediment transport is complicated and the range of processes involved in most movements means that simple relationships are unlikely to hold not least because the movement of sediment often changes the substrate which in turn affects the flow conditions thirdly the inherently stochastic nature of sediment transport means that any capacity relationships do not scale either in time or in space consequently new theories of sediment transport are needed to improve understanding and prediction and to guide measurement and management of all geomorphic systems

conjugate relay zones geometry of displacement transfer between opposed dipping normal faults abstract overlapping opposed dipping normal faults can have complementary displacement distributions indicating transfer of displacement between them in the same way as at relay zones between faults with the same dip direction we constrain the mechanism by which displacement is transferred between opposed dipping faults by examining the geometries of faulted horizons and fault throw distributions at these conjugate relay zones structure contour maps of horizons offset by overlapping opposed dipping faults from different extensional settings display a consistent pattern above the line of intersection between the conjugate faults the deformed horizon is flat between converging faults and displacement transfer is reflected in changes in footwall elevation below the line of fault intersection the mutual footwall is flat and elevation changes occur in the hanging walls of the divergent faults these elevation changes can be explained as a simple superposition of the deformation fields of two faults that have retarded lateral propagation due to the presence of the other synchronous fault irrespective of whether the two faults actually intersect the observed patterns of horizon elevation strongly resemble those seen at boundaries between adjacent basin scale half graben of opposed polarity

strain and scaling of faults in the chalk at flamborough head u k analysis has been made of the orientations displacements and spacings of 1340 extensional faults with displacements of up to 6 m along an almost completely exposed 6 km length of cliff this data set has been used to study how fault populations account for strain in a region and to study relationships between different scales of fault strains have been estimated the maximum and intermediate extensions are sub horizontal with approximately equal extension e 0 01 in all horizontal directions it can be inferred that the minimum extension maximum compression was sub vertical but that the wide variety of fault orientations and cross cutting relationships resulted from variable horizontal extensions some faults have oblique slip slickenside lineations which imply a period of later dominantly nnw sse extension which possibly developed as the exposure scale faults linked up e w striking larger scale normal faults effectively forming a single wide fault zone graphs of displacement per unit distance are used to illustrate variations in displacement the scaling of fault displacement appears to follow a power law relationship the differences in orientation between the small scale and large scale faults precludes a simple estimation of the total strain over all scales

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

zipper junctions a new approach to the intersections of conjugate strike slip faults intersecting pairs of simultaneously active faults with opposing slip sense present geometrical and kinematic problems such faults rarely offset each other but usually merge into a single fault even when they have displacements of many kilometers the space problems involved are solved by lengthening the merged fault zippering up the conjugate faults or splitting it unzippering this process can operate in thrust normal and strike slip fault settings examples of conjugate pairs of large scale strike slip faults that may have zippered up include the garlock and san andreas faults in california usa the north and east anatolian faults turkey the karakoram and altyn tagh faults tibet and the tonale and giudicarie faults southern alps intersecting conjugate ductile shear zones behave in the same way on outcrop and micro scales zippering may produce complex and significant patterns of strain and rotation in the surrounding rocks depending on the angle between the faults and the relative strength of the blocks they bound a zippered fault will have a slip rate equal to the vector sum of the slip rates on the merging faults unless that displacement is transferred into or out of the system by distributed strain in the surrounding rocks

vadose zone influences on aquifer parameter estimates of saturated zone hydraulic theory aquifer drainage was numerically simulated by a coupled unsaturated saturated flow equation the effect of the vadose zone on aquifer parameter predictions of classical hydraulic theory was investigated saturated zone hydraulic theory was shown to be fairly robust in estimating the saturated hydraulic conductivity but less so in estimating drainable porosity mainly because of the much tighter possible range for the latter application of the coupled flow equation may explain discrepancies between predictions of classical saturated zone theory and observations

on the pullout resistance of geosynthetics pullout tests are reported on geosynthetic test specimens embedded in a relatively dense coarse sand sample the tests are displacement controlled and are performed at different vertical effective

landslide inventory in a rugged forested watershed a comparison between air photo and field survey data abstract landslide inventories are routinely compiled by means of aerial photo interpretation api when examining photo pairs the forest canopy notably in old growth forest hides a population of not visible landslides in the present study we attempt to estimate how important is the contribution of landslides not detectable from aerial photographs to the global mass of sediment production from mass failures on forested terrain of the capilano basin coastal british columbia api was coupled with intensive fieldwork for identification and measurement of all landslides a 30 year framework was adopted we show that not visible landslides can represent up to 85 of the total number of failures and account for 30 of the volume of debris mobilised such percentages display high sub basin variability with rates of sediment production varying by one order of magnitude between two sub basins of the study area this is explained qualitatively by gis based analysis of slope frequency distributions drainage density and spatial distribution of surficial materials such observations find further support in the definitions of transport limited and supply limited basins as a practical consideration to land managers we envisage that supplementary fieldwork for landslide identification is mandatory in transport limited systems only fieldwork has demonstrated that gully related failures have a greater importance than one could expect from api

strains at the intersections of synchronous conjugate normal faults abstract processes accommodating the mutual offsetting of intersecting conjugate faults are investigated by outcrop examination of three pairs of conjugate normal faults with maximum throws from 5 mm to 10 cm in two cases resolved fault throws decrease sharply towards the intersection zones which on the scale of observation are zones of ductile thinning of inter fault layers that accommodate the throw reductions strain within the intersection zone of conjugate faults in fluvio glacial sands is accommodated by inter grain slip and layer thinning is complemented by layer parallel extension at constant volume in a second example strain within the intersection zone of conjugate faults in inter layered chalk and marl is accommodated by volume reduction without layer extension in a third example also in fluvio glacial sands strain in the intersection zone is accommodated by small faults throws 1 mm when throws on all resolvable faults are aggregated there is no decrease in throw towards the conjugate intersection the presence or absence of a decrease in resolved throw towards conjugate intersections and of a complementary ductile zone accommodating the change in throw is a function not only of the resolution limit of the observations but also of the scale of the deformation process within the conjugate zone

3d seismic characterisation of an array of blind normal faults in the levant basin eastern mediterranean the geometry throw distribution and kinematics of an array of blind normal faults were investigated using a high resolution 3d seismic dataset located in the levant basin offshore israel to establish criteria allowing true blind faults to be distinguished from minor synsedimentary faults a detailed analysis of throw distribution on the fault planes shows that the displacement exhibits a crudely concentric pattern about a maximum region located centrally on a fault plane as expected for ideal blind faults however vertical displacement profiles do not exhibit classical linear or triangular profiles but are mostly flat topped or hybrid in type comparison of unrestricted blind faults to those that interacted with a mechanical boundary or another structure suggests that such interactions significantly modify the throw spatial distribution on a fault plane to distinguish small synsedimentary faults from blind faults we use a combination of three criteria to assess whether a fault grew by blind propagation 1 plunging upper tip region and complementary pattern in the throw contours 2 presence of upper tip propagation fold and 3 absence of stratigraphic evidence that the fault interacted with the free surface

effects of layering and anisotropy on fault geometry the geometry and orientation of faults are examined using several field examples of small scale 1 with dihedral angles usually of about 50 as predicted by the coulomb theory of failure in layered rocks the geometry of faults varies with the orientation of layering with respect to the stress field where 1 is approximately normal to layering or anisotropy conjugate faults also develop symmetrically about 1 where rocks have interbedded layers with different mechanical behaviours however faults tend to initiate orthogonal to the more brittle layers i e originate as extension fractures sub parallel to 1 but oblique to the less brittle layers as the fault steps through the layering pull aparts are developed which may reduce the dihedral angle where 1 is oblique c 25 75 to anisotropy one set of faults is developed at a high angle to layering with another at a low angle usually showing a ramp flat geometry large dihedral angles up to 90 may result and 1 does not bisect this angle where 1 is approximately parallel to layering two cases can be recognized where 3 is approximately normal to layering faults with layer parallel flats and contractional ramps develop where 2 is approximately normal to layering conjugate faults develop which are symmetrical about 1 the geometry resembling that in isotropic rocks these observations are in agreement with rock deformation experiments which show the strong effect of anisotropy on fault orientation but the observations incorporate the effects of layering of materials with different deformation characteristics

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

sediment connectivity a framework for understanding sediment transfer at multiple scales a major challenge for geomorphologists is to scale up small magnitude processes to produce landscape form yet existing approaches have been found to be severely limited new ways to scale erosion and transfer of sediment are thus needed this paper evaluates the concept of sediment connectivity as a framework for understanding processes involved in sediment transfer across multiple scales we propose that the concept of sediment connectivity can be used to explain the connected transfer of sediment from a source to a sink in a catchment and movement of sediment between different zones within a catchment over hillslopes between hillslopes and channels and within channels using fluvial systems as an example we explore four scenarios of sediment connectivity which represent end members of behaviour from fully linked to fully unlinked hydrological and sediment connectivity sediment travel distance when combined with an entrainment parameter reflecting the frequency magnitude response of the system maps onto these end members providing a coherent conceptual model for the upscaling of erosion predictions this conceptual model could be readily expanded to other process domains to provide a more comprehensive underpinning of landscape evolution models thus further research on the controls and dynamics of travel distances under different modes of transport is fundamental copyright 2014 john wiley sons ltd

fault kinematics in supradetachment basin formation menderes core complex of western turkey abstract the neogene alasehir supradetachment basin in western turkey occurs in the footwall of the modern alasehir gediz graben and is a major component of the aegean extensional province in anatolia that developed during the late cenozoic exhumation of the menderes core complex the size geometry accommodation space and internal structure stratigraphy of this basin were strongly controlled by the kinematics and interplay of four different fault generations throughout its early miocene pleistocene evolution the e w striking nne dipping 10 30 alasehir detachment fault separates the high grade crystalline rocks of the core complex below from the neogene deposits of the basin in the hanging wall above the basin parallel synthetic and antithetic high angle normal faults represent a block faulting stage of the continued horizontal extension that terminated the northerly slip along the detachment surface and produced horst graben structures in and across the basin these faults were also responsible for the back tilting of the basinal strata into steeper dips and the rotation of the previously formed faults into gently dipping planes the mutually crosscutting relationships between the intra basinal low angle and basement involved high angle and normal faults indicate their contemporaneous development and operation the nne striking basin perpendicular oblique slip hinge faults are reminiscent of transfer cross faults in both continental and oceanic extension and divide the supradetachment basin into a series of fault blocks with their own internal structure and stratigraphy differential uplift and exhumation of the core complex rocks along these hinge faults and the varied displacement and slip along and across them within the basinal strata caused differential extension and block uplift leading to the formation of local unconformities in the supradetachment basin significant changes in the dip directions and strike orientations of the sedimentary beds and the observed deviations from the inferred direction of maximum extension in the adjacent fault blocks resulted from rotational deformation due to hinge faulting fault segmentation of the alasehir basin as a result of extension parallel hinge faulting is a characteristic feature of its supradetachment basin evolution

the unit response of groundwater outflow from a hillslope subsurface flow from a hillslope can be described by hydraulic groundwater theory as formulated by the boussinesq equation solution of its linear version brings out some of the essential features of this phenomenon arbitrary inputs can be accommodated by simple convolution of the sudden drawdown problem the relative magnitude of the driving mechanisms namely the streamwise pressure gradient resulting in diffusion and gravity i e slope resulting in advection can be determined by a simple dimensionless parameter

the formation of conjugate normal fault systems in folded sandstone by sequential jointing and shearing waterpocket monocline utah 1 we report conjugate normal fault development by the formation and subsequent shearing of joints during flexure and associated extension of the jurassic wingate and navajo sandstones at the core of the waterpocket monocline utah geometry and structural components across fault zones were quantified from an incipient stage to a relatively well developed stage where the zone is 120 m wide and accommodates more than 3 5 m of slip shearing of joints leads to the formation of splay fractures near the joints tip subsequently these splay fractures are sheared and a new generation of splay fractures forms multiple generations of splay fractures cause the width of the fault damage zone to expand into the surrounding host rock producing unusually wide fault damage zones with respect to fault offset these extensive fault damage zones are stratigraphically confined and develop with low strains at small bed dips during folding the faults formed by this sequential process develop a characteristic fault architecture distinguished by the type of component structures their geometric relationships and their distribution we conclude that cyclic joint formation shearing accompanied by splay fracture formation and repeated shearing produce a geometric pattern similar to a classical conjugate fault system however the mechanism identified here has different implications for fault intersection angles stress inversion and fault architecture

a new hierarchical bayesian approach to analyse environmental and climatic influences on debris flow occurrence abstract how can debris flow occurrences be modelled at regional scale and take both environmental and climatic conditions into account and of the two which has the most influence on debris flow activity in this paper we try to answer these questions with an innovative bayesian hierarchical probabilistic model that simultaneously accounts for how debris flows respond to environmental and climatic variables in it full decomposition of space and time effects in occurrence probabilities is assumed revealing an environmental and a climatic trend shared by all years catchments respectively clearly distinguished from residual random effects the resulting regional and annual occurrence probabilities evaluated as functions of the covariates make it possible to weight the respective contribution of the different terms and more generally to check the model performances at different spatio temporal scales after suitable validation the model can be used to make predictions at undocumented sites and could be used in further studies for predictions under future climate conditions also the bayesian paradigm easily copes with missing data thus making it possible to account for events that may have been missed during surveys as a case study we extract 124 debris flow event triggered between 1970 and 2005 in 27 catchments located in the french alps from the french national natural hazard survey and model their variability of occurrence considering environmental and climatic predictors at the same time we document the environmental characteristics of each debris flow catchment morphometry lithology land cover and the presence of permafrost we also compute 15 climate variables including mean temperature and precipitation between may and october and the number of rainy days with daily cumulative rainfall greater than 10 15 20 25 30 40 mm day 1 application of our model shows that the combination of environmental and climatic predictors explained 77 of the overall variability of debris flow occurrences in this data set occurrence probabilities depend mainly on climatic variables which explain 44 of the overall variability through the number of rainy days and maximum daily temperature this important time component in the variability of overall debris flow occurrence is shown to be responsible for a significant increase in debris flow activity between 1970 and 2005 at regional scale environmental variables which account for 33 of the overall variability includes mostly the morphometric variables of the debris flow catchments

geomorphology in context dispatches from the field abstract field research enables a researcher to view geomorphic systems in broader contexts than those envisioned while at a desk and can yield unanticipated insights that change the course of an investigation or affect the interpretation of results geomorphological field research often produces aha moments epiphanies that enhance understanding and lead toward more complete explanation of the processes and landforms under study this paper uses examples from aha moments in the field to demonstrate the importance of field observation as a way of gaining information about the broader contexts of research sites especially in process geomorphology spatial contexts include the scales of processes and features linkages between a study site and its surroundings and information observed in the field about other processes anthropogenic activities or unexpected factors that might affect a study temporal contexts not as evident in the field place a research site in a longer term history of changes and adjustments finally exploring an abstract set of mental contexts reveals reasons that expectations differ from the realities encountered in the field constraints and biases that a researcher may not have noted and the possibility that the unexpected can potentially advance geomorphic research time spent in the field complements scientific reductionism and provides opportunities to appreciate the richness and complexity of earth surface systems

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

intersection patterns of normal faults in the lufeng sag of pearl river mouth basin china insights from 4d physical simulations abstract interpretation of seismic data from the lufeng sag of the pearl river mouth basin prmb in the northern part of south china sea shows that different intersection patterns developed in the cover units above basement normal faults a series of analogue models are used to investigate the intersection patterns and deformation in the sedimentary cover sequences above a basement horst bounded by two non parallel faults modelling results show that during their upward propagation the basement faults may intersect within the cover sequences and form a graben above the basement horst length and width of the graben increase with cover thickness the strike and dip intersection points are controlled directly by the thickness of the cover sequences dip and strike of the basement faults and width of the basement horst the intersection point migrates along the axis of the graben toward the wide end of the basement horst when the cover sequence thickens in contrast it migrates toward the narrow end of the basement horst where both fault dip and angle of strike difference increase the intersection point moves upward with increasing width of the basement horst crest model profiles also indicate that in the presence of a ductile layer between the cover and basement such intersection patterns do not form interpretation of seismic data and model results show that the intersection pattern developed in the lufeng sag is a result of propagation of basement faults into cover units during different extension stages of the basin results of this study can be applied to many other sedimentary basins where such fault intersection patterns are likely to form when non parallel conjugate basement faults are active during sedimentation