hydraulic physical and rheological characteristics of rain triggered lahars at semeru volcano indonesia lahars volcanic debris flows have been responsible for 40 of all volcanic fatalities over the past century mount semeru east java indonesia is a persistently active composite volcano that threatens approximately one million people with its lahars and pyroclastic flows despite their regularity the behaviour and the propagation of these rain triggered lahars are poorly understood in situ samples were taken from lahars in motion at two sites in the curah lengkong river on the southeast flank of semeru providing estimates of the particle concentration grain size spectrum grain density and composition this enables us to identify flow sediment from three categories of lahars a hyperconcentrated flow b non cohesive clast and matrix supported debris flow and c muddy flood to understand hyperconcentrated flow sediment transport processes it is more appropriate to sample the active flows than the post event lahar deposits because in situ sampling retains the full spectrum of the grain size distribution rheometrical tests on materials sampled from moving hyperconcentrated flows were carried out using a laboratory vane rheometer despite technical difficulties results obtained on the 63 180 and 400 m fractions of the sampled sediment suggest a purely frictional behaviour importantly and contrary to previous experiments conducted with monodisperse suspensions our results do not show any transition towards a viscous behaviour for high shear rates these data provide important constraints for future physical and numerical modelling of lahar flows copyright 2010 john wiley sons ltd

flow behaviour and runout modelling of a complex debris flow in a clay shale basin identification of debris flow hazard areas necessitates the knowledge of the flow thickness and the runout distance both have been investigated using a numerical runout model on the faucon stream south french alps representative of clay shale basins results of various rheological tests and numerical experiments are presented and discussed the calibration of the model was undertaken using the results of both geomorphological surveys and sedimentological analyses rheological tests using either a parallel plate rheometer a coaxial rheometer slump tests and an inclined plane were carried out on several samples results have shown that the flow behaviour could be described by an herschel bulkley constitutive equation the rheological responses of several natural suspensions collected from surficial deposits sandstones moraines weathered black marls were also investigated in order to model the runout of the flow the model bing was used the model describes well the influence of each type of sediment on the behaviour runout distance deposit thickness of the flow although the velocities were significantly overestimated different risk scenarios are tested and discussed copyright 2005 john wiley sons ltd

the viscosity of fine grained sediments a comparison of low to medium activity and high activity clays abstract viscosity is generally recognized as an indicator of landslide mobilization viscous behavior at relatively low high shear rates is an important predictor of the motion of slow fast moving landslides the viscosity in a modified bingham model at low and high shear rates was examined the viscous characteristics are primarily dependent on the physico chemical properties of the materials in question e g grain size mineralogy salinity in this context the viscous characteristics of low to medium activity and high activity clays bentonite with different salinities were compared empirical relationships exist between the liquidity index and the plastic viscosity regardless of the mineralogical composition this study also demonstrated a positive relationship between the liquidity index and the viscosity in a modified bingham model with n 1 the results showed that low to medium activity and high activity clays fall into a similar range for fine grained sediments mixed with salt water 30 g l however an effect of salinity was evident when using high activity clays mixed with fresh water modified bingham model is a useful and powerful tool for describing pre and post yield viscosity in engineering practice by correlating the geotechnical and rheological properties of fine grained sediments index properties can help to estimate the appropriate values for the rheological parameters of these soils

insights into subduction related uplift along the hikurangi margin new zealand using numerical modeling 1 we investigate the causes of regional uplift along the hikurangi margin north island new zealand late quaternary rock uplift rates and postglacial fluvial incision rates delineate broad changes in rock uplift pattern along the margin comparison with the neogene rock uplift rates the erosion surface on basement and the margin morphology suggests that these uplift patterns are long lived and relate to deep seated subduction processes we use two dimensional numerical finite element models to place constraints on margin geometry and uplift rates resulting from subduction processes inferred to drive regional uplift the models indicate that subduction of relatively buoyant and thick hikurangi plateau crust is the most likely mechanism for low rates 1 mm yr 1 of uplift along the entire margin sediment underplating is probably the major cause of higher rates of uplift of the central and northern axial ranges 2 4 mm yr 1 seamount subduction could account for short wavelength zones of higher uplift rate on the order of 1 mm yr 1 and could contribute to tectonic erosion which may be driving uplift in the northern margin this study shows the value of using numerical models to link regional patterns of rock uplift and surface morphology to deep seated subduction processes

a new mesozoic isochron chart of the northwestern pacific ocean paleomagnetic and tectonic implications a new mesozoic isochron chart of the northwestern pacific ocean has been completed by utilizing all the currently available data from 357 cruises our chart provides the first whole view of the mesozoic magnetic anomaly lineations in the northwestern pacific ocean and yields essential information for understanding the problems of the mesozoic magnetostratigraphic time scale and the evolutional history of the pacific plate the mesozoic magnetostratigraphic time scale must be recalibrated using not only the hawaiian lineation set but also other mesozoic lineation sets the lack of lineation m0 in the lineation sets other than the hawaiian lineation set indicates that a reorganization of the ridges except the pacific farallon ridge occurred between chrons m1 and m0 nearly 120 ma the eruption rate of the shatsky hotspot seems to be comparable to that of the reunion hotspot at their initial stage the growth of the pacific plate began in a small triangular region at about 190 ma

two dimensional water flood and mudflow simulation flo 2d is a two dimensional finite difference model that simulates clear water flood hazards mudflows and debris flows on alluvial fans and urban floodplains interactive flood or mudflow routing between channel street and floodplain flow is performed using a uniform grid system to describe complex floodplain topography a quadratic rheological model developed from field and laboratory mudflow data enables appropriate simulations of flooding conditions ranging from clear water to hyperconcentrated sediment flows computer aided design cad graphics of predicted time sequenced flood depths automates the delineation of flood hazards replication of the 1983 rudd creek mudflow in utah demonstrates the capability of the model

determining rheological parameters of debris flow material abstract a 2 0 m diameter steel 30 inverted cone and plate viscometer rheometer was designed constructed and used to test the behaviour of coarse grained debris flow materials a 1 5 scale model machine was also constructed and used to test the internal flow dynamics of the viscometer rheometer and to obtain results for fluids grain fluid mixtures and debris flow fines for fluids and grain fluid mixes our results were similar to those obtained earlier using standard viscometric systems derived rheological parameters for debris flow materials and clay slurries agreed well with those determined from calculation direct measurement and field observation apparent viscosities were shear rate dependent extremely sensitive to water content and as high as 6000 pa s instantaneous stresses within shearing debris flow material varied over a wide range debris flow materials with bimodal grain size distributions had a dilatant plastic rheology those with a low content of coarse material and unimodal grain size distribution or exceptionally high fines content had a plastic or viscoplastic rheology

the development mechanism of gravel bars in rivers the development stability and growth direction of gravel mid channel bars in rivers were studied by analyzing sediment distribution and vegetation development along the bars field studies and sediment sampling were conducted in the source region of the yellow and lancang rivers on the qinghai plateau the results showed that the gravel bars in rivers always grow in the upstream direction because gravel and sand are deposited at the upstream end of the bars gravel bedload stopped at the bar head sand and silt moved as suspended load during the flood season and were deposited at the bar tail due to vegetation resistance consequently sediment size varied from gravel to sand and silt along the bars from the head to the tail on the bar surface dense vegetation coverage normally grew at the bar tail while only pioneer species occurred at the bar head the prevalent phenomena demonstrated the upstreamward growth of mid channel bars

the mesozoic tectonic history of the magellan microplate in the western central pacific magnetic lineation mapping in the western central pacific has revealed a pair of opposite sensed fanned lineation patterns that define the accretionary boundaries of the fossil magellan microplate this tectonic synthesis results from extensive magnetic mapping of two new lineation patterns over a large area and extended mapping of previously identified lineations the entire evolutionary history of the magellan microplate is well constrained to a 9 m y period in the early cretaceous by synchronous spreading patterns and associated geologic data during this period the microplate grew and evolved as a generally rectangular structure to a final size of 700 km 600 km with spreading centers on two opposing sides and transform faults on the other two sides the lifetime and size of the magellan microplate are somewhat longer and larger respectively than presently active microplates on the east pacific rise however these modern structures are still evolving and growing and the tectonic behavior of the modern and cretaceous systems appears to be similar study of both active and fossilized microplates should provide additional insights on their common tectonic histories in particular we show that the magellan trough spreading center behaved as an asymmetric accretionary plate boundary that can be described with two separate poles of motion very close to this spreading center during much of its history the magellan trough spreading center then failed as a result of a larger ridge reorganization at the triple junction of the pacific farallon and phoenix plates at ml0n time microplate activity ceased when the microplate became welded to the pacific plate at m9 time

the effects of an addition of force free particles on the rheological properties of fine suspensions this study provides some elements for understanding the behavior of water debris mixtures containing clay silt sand and boulders at high solid concentrations accurate simple shear rheometrical results for various clay water mixtures and fine debris flow fractions with different added sand concentrations in the shear rate range from 10 2 to 10 2 s 1 are presented in this shear rate range the behavior of these fluids is similar to the behavior of the initial fluid without sand i e it may be well represented by a herschel bulkley model with a power parameter close to 1 3 with the initial fluids yield stress from 20 to 200 pa the suspension yield stress increases exponentially with the increase in sand diameter between 100 and 200 m concentration as long as the latter does not exceed 30 however the rate of increase is less than the corresponding rate for the initial fluid and is correspondingly smaller as the grain size distribution is less well sorted diagrams showing the increase of

the post glacial downcutting history in the waihuka tributary of waipaoa river gisborne district implications for tectonics and landscape evolution in the hikurangi subduction margin new zealand abstract determining the spatial and temporal deliveries of sediment from the waipaoa river catchment in the post glacial period is a major goal of integrated source to sink landscape evolution studies in the region in a 2 2 km long section of the waihuka tributary 217 km 2 of the waipaoa river 2150 km 2 in eastern north island new zealand a sequence of at least ten fluvial terraces and abandoned meanders up to 45 m above the present river records rates and times of post glacial downcutting dateable organic and tephra horizons in the terrace and meander infill stratigraphy indicate that downcutting at this location on the waihuka tributary was dominated by a short lived event in the early holocene from 10 8 ka bp when as much as half of the downcutting was accomplished in only 10 15 of post glacial time the large downcutting event is interpreted to record the passing of a succession of major knickpoints or a knickzone through this tributary the initiation of knickpoint retreat in the catchment was primarily a consequence of reduction in sediment supply at the end of mis 2 based on the timing of rapid downcutting in the waipaoa river mainstem we estimate that the rate of knickpoint retreat along the waihuka tributary was about 2 km kyr in the period before and after rapid downcutting in the waihuka tributary modest incision rates averaging 1 2 mm yr probably represent the regional tectonic uplift rate

channel changes in badlands stripping of the vegetation and soil from a 13 hectare site in virginia underlain by coastal plain sediments created a rapidly evolving badland topography two types of channels developed 1 sand bed alluvial channels were graded to transport the bed material load supplied from slope erosion with available runoff but they also generally eroded their beds slowly and 2 steeper bedrock floored channels incised rapidly in bedrock channels the erosion rate was proportional to the 4 9ths power of drainage area and the 2 3rds power of gradient these exponents are consistent with a model in which the erosion rate is proportional to the bed shear during high flows due to rapid mass wasting and reduced runoff the alluvial channels became as much as 50 steeper during the winter than the summer with an attendant yearly cycle of winter aggradation and summer entrenchment the gradients their seasonal variability and their downstream hydraulic geometry were consistent with the predictions of total load transport formulas for sand beds and high loads the hydraulic geometry of alluvial channels in the virginia badlands were similar to that on the morrison formation in the western united states

field observations rheological testing and numerical modelling of a debris flow event debris flows generated from landslides are common processes and represent a severe hazard in mountain regions due to their high mobility and impact energy we investigate the dynamics and the rheological properties of a 90 000 m3 debris flow event triggered by a rapid regressive landslide with high water content field evidence revealed a maximum flow depth of 7 8 m with an estimated peak discharge of 350 400 m3 s 1 depositional evidence and grain size distribution of the debris pose the debris flow in an intermediate condition between the fluid mud and grain flow behaviour the debris flow material has silt clay content up to 15 per cent the rheological behaviour of the finer matrix was directly assessed with the ball measuring system the measurements performed on two samples at 45 63 per cent in sediment concentration by volume gave values of 3 5 577 pa for the yield strength and 0 6 27 9 pa s for the viscosity based on field evidence we have empirically estimated the yield strength and viscosity ranging between 4000 200 pa and 108 134 pa s respectively we used the flo 2d code to replicate the debris flow event we applied the model with rheological properties estimated by means of direct measurements and back analyses the results of these models show that the rheological behaviour of a debris flow mass containing coarse clasts can not be assessed solely on the contribution of the finer matrix and thus neglecting the effects of direct grain contacts for debris flows composed by a significant number of coarse clasts a back analysis estimation of the rheological parameters is necessary to replicate satisfactorily the depositional extent of debris flows in these cases the back estimated coefficients do not adequately describe the rheological properties of the debris flow copyright 2006 john wiley sons ltd

from mountain source to ocean sink the passage of sediment across an active margin waipaoa sedimentary system new zealand abstract the joint us nz source to sink initiative aims to unravel the tectonic climatic and other processes that shape the landscape from the mountains to deep ocean of two focus areas chosen world wide the waipaoa sedimentary system wss of north eastern new zealand was identified as an example of a mid latitude high sediment input system it resides within the westerly wind belt and extends across the convergence zone of the australian and pacific plates accordingly the tectonic and climatic drivers are prominent and their influences on the wss are decipherable as is documented in the suite of source to sink studies presented in this special issue of marine geology the wss is forced at several temporal and spatial scales which collectively appear as short term events storms earthquakes and volcanic eruptions superimposed on long term behavioural shifts tectonic uplift and eustatic sea level change overall the wss is undergoing uplift which has been contributing to valley incision since the last glacial maximum uplift is both gradual and intermittent the latter relating to fault and subduction related earthquakes such seismic activity destabilises the landscape and together with frequent storms generates large amounts of sediment as this sediment passes through the system part is captured in traps formed by local subsidence of the coastal plain and middle continental shelf where large thicknesses of holocene and probably older sediment are sequestered e g 200 m under the coastal plain nevertheless substantial sediment still reaches the continental slope to accumulate in canyon heads and slope basins with other deposits redistributed down slope in mass flows major volcanic eruptions also affect the sediment flux via direct input from ash fall and by enhanced erosion following volcanic destruction of terrestrial vegetation frequent storms of varying intensity play a key role in the generation and transfer of sediment major events such as cyclone bola of 1988 inundated the shelf with sediment but identifiable flood deposits were preserved only locally attesting to the effectiveness of shelf physical and biological mixing regimes despite the storms earthquakes and volcanic eruptions the largest perturbation of the wss at least in the last 2400 years has been the human deforestation of the landscape the resultant influx of sediment overwhelmed the shelf s storage capacity instead of capturing 90 the fluvial input as in pre human times the modern shelf retains only 25 the remainder escaping to the slope and elsewhere

flow of variably fluidized granular masses across three dimensional terrain 1 coulomb mixture theory rock avalanches debris flows and related phenomena consist of grain fluid mixtures that move across three dimensional terrain in all these phenomena the same basic forces govern motion but differing mixture compositions initial conditions and boundary conditions yield varied dynamics and deposits to predict motion of diverse grain fluid masses from initiation to deposition we develop a depth averaged three dimensional mathematical model that accounts explicitly for solid and fluid phase forces and interactions model input consists of initial conditions path topography basal and internal friction angles of solid grains viscosity of pore fluid mixture density and a mixture diffusivity that controls pore pressure dissipation because these properties are constrained by independent measurements the model requires little or no calibration and yields readily testable predictions in the limit of vanishing coulomb friction due to persistent high fluid pressure the model equations describe motion of viscous floods and in the limit of vanishing fluid stress they describe one phase granular avalanches analysis of intermediate phenomena such as debris flows and pyroclastic flows requires use of the full mixture equations which can simulate interaction of high friction surge fronts with more fluid debris that follows special numerical methods described in the companion paper are necessary to solve the full equations but exact analytical solutions of simplified equations provide critical insight an analytical solution for translational motion of a coulomb mixture accelerating from rest and descending a uniform slope demonstrates that steady flow can occur only asymptotically a solution for the asymptotic limit of steady flow in a rectangular channel explains why shear may be concentrated in narrow marginal bands that border a plug of translating debris solutions for static equilibrium of source areas describe conditions of incipient slope instability and other static solutions show that nonuniform distributions of pore fluid pressure produce bluntly tapered vertical profiles at the margins of deposits simplified equations and solutions may apply in additional situations identified by a scaling analysis assessment of dimensionless scaling parameters also reveals that miniature laboratory experiments poorly simulate the dynamics of full scale flows in which fluid effects are significant therefore large geophysical flows can exhibit dynamics not evident at laboratory scales

knickpoint initiation and distribution within fluvial networks 236 waterfalls in the waipaoa river north island new zealand if knickpoints transmit signals of base level fall in river networks then improvements in our understanding of their retreat rate and basin wide distribution helps constrain the transient response following perturbation many studies of knickpoint retreat focus on the response of trunk streams to base level fall here we examine the response of an entire fluvial network as recorded by 236 active knickpoints distributed within the waipaoa river on the north island of new zealand base level fall within the waipaoa catchment initiated 18 000 years ago in response to a climatically triggered and tectonically exacerbated pulse of incision using observations from field work aerial photo analysis and a digital elevation model dem we study the knickpoint positions within the network we find that 70 of the knickpoints are located at drainage areas between 1 10 5 m 2 and 1 10 6 m 2 and more than half are b1 km upstream of a large change in drainage area for the knickpoints b1 km upstream of large tributary junctions we find that the retreat distances were well correlated with the tributaries drainage areas in order to determine how a pulse of incision distributes itself throughout a fluvial network we develop two simple end member models and compare their behavior to the observed knickpoint distribution in the waipaoa in the first model we propose that a knickpoint initiated at the basin outlet retreats upstream and distributes the signal throughout the network at a rate that is a power law function of drainage area in the second model we propose that knickpoints form near a threshold drainage area below which channels cannot incise with the same efficiency as possible in downstream reaches though neither model addresses the along stream variability in substrate or knickpoint form the misfit between the modeled and the observed knickpoints along stream positions are surprisingly low b1 km 1 25 of the total stream length for knickpoints with drainage areas b1 10 6 m 2 large misfits up to 3 5 km are observed for knickpoints with present day drainage areas greater than 1 10 6 m 2 the large single step in channel elevation that characterizes knickpoints presently observed in tributaries of the waipaoa river may not characterize the base level fall signal that propagated through the trunk streams evidence for progressive rather than instantaneous incision in the trunk streams the knickpoints vicinities to tributary junctions and the equivalent success of the two end member models lead us to conclude that the present positions of the 236 observed knickpoints are largely a consequence of thresholds in channel incision at low drainage areas

numerical modeling of mudflows to predict mudflow dynamics a numerical model based on shallow water equations is developed previous work has shown that mudflow behavior can be well represented by a herschel bulkley model in a laminar regime generally observed in practice a wall friction force expression has been theoretically deduced for steady uniform flows for unsteady flows the wall friction force is assumed to be equal to the resistance of a steady uniform flow with the same depth and mean velocity the numerical model parameters directly deduced from herschel bulkley model are determined independently by rheological measurements because of the lack of precise field data experimental results obtained on a physical model are used in order to validate the numerical model the main features of the experimental transient flows carried out in a laboratory flume are for some identified conditions in fairly good agreement with numerical model predictions without any additional parameter fitting

characterization and rheology of krishna godavari basin sediments abstract the krishna godavari offshore basin to the east of india is a proven reserve rich in natural gas hydrate the impact of sediment characteristics on the hydrate formation has already been well established in open literature in the present study we have attempted to investigate the mineralogy of sediments collected from kg basin by elemental analysis energy dispersive spectroscopy and x ray diffraction various physicochemical characteristics of the clayey sediments such as tds salinity ph conductivity and resistivity were analysed at various concentrations and compared together also this paper highlights the rheological behavior of the sediment samples with concentrations of 20 35 and 50 wt at different experimental temperatures 278 15 k 283 15 k and 288 15 k viscosity measurements were performed for a wide range of shear rates for all concentrations and comparative studies have been conducted on their exhibited behavior the viscosity of sediment sample were found to be varying from 76 3 to 0 003 pa s depending on the sediment concentration temperature and shear rate in addition viscoelastic measurements were carried out at various angular frequencies for all the sediment samples the work aims to characterise the sediments of kg basin and analyse the rheological behavior of sediment solution which has not yet been reported in open literature this will provide vital information for possible methane recovery from kg basin hydrate reservoir by manipulating the host sediment behavior

pacific microplate and the pangea supercontinent in the early to middle jurassic comment and reply reply we thank nazario pavoni for pointing out his previous observations of approximate bipolar symmetry in present day global tectonics and deep mantle seismic velocities pavoni 1991 1 the latter observation has been generally confirmed especially by more recent analyses of teleseismic s waves

intra event scale bar bank interactions and their role in channel widening channel bars and banks strongly affect the morphology of both braided and meandering rivers accordingly bar formation and bank erosion processes have been greatly explored there is however a lack of investigations addressing the interactions between bed and bank morphodynamics especially over short timescales one major implication of this gap is that the processes leading to the repeated accretion of mid channel bars and associated widenings remain unsolved in a restored section of the drau river a gravel bed river in austria mid channel bars have developed in a widening channel during mean flow conditions the bars divert the flow towards the banks one channel section exhibited both an actively retreating bank and an expanding mid channel bar and was selected to investigate the morphodynamic processes involved in bar accretion and channel widening at the intra event timescale we repeatedly surveyed riverbed and riverbank topography monitored riverbank hydrology and mounted a time lapse camera for continuous observation of riverbank erosion processes during four flow events the mid channel bar was shown to accrete when it was submerged during flood events which at the subsequent flow diversion during lower discharges narrowed the branch along the bank and increased the water surface elevation upstream from the riffle which constituted the inlet into the branch these changes of bed topography accelerated the flow along the bank and triggered bank failures up to 20 days after the flood events four analysed flow events exhibited a total bar expansion from initially 126 m2 to 295 m2 while bank retreat was 6 m at the apex of the branch the results revealed the forcing role of bar accretion in channel widening and highlighted the importance of intra event scale bed morphodynamics for bank erosion which were summarized in a conceptual model of the observed bar bank interactions copyright 2015 john wiley sons ltd

rheological properties of fine grained sediment the roles of texture and mineralogy rheological properties of fine grained sediments depending on index properties and salinity were examined to characterize flow behaviors as a function of soil type groups were made for convenienc

laboratory analysis of mudflow properties a rotational viscometer has been designed for laboratory measurements of the rheological properties of natural mudflow deposits in colorado the mudflow matrices comprised of silt and clay particles are sheared under temperature controlled conditions at volumetric sediment concentrations ranging from 0 10 0 45 this study stresses the importance of conducting rheological measurements at low rates of shear because 1 those are the conditions found in natural channels and 2 they avoid the slippage problems observed at large sediment concentrations at low rates of shear the bingham model is fitted to the measured rheograms and both the viscosity and yield stress increase exponentially with the sediment concentration of the fluid matrix both the yield stress and the viscosity increase by three orders of magnitude as the volumetric concentration of sediments in the fluid matrix changes from 10 to 40 the addition of sand particles does not significantly alter the rheological properties of the matrix unless the volumetric concentration of sands exceeds 0 20

a dynamic model for rainfall induced landslides on natural slopes assessment of landslide hazard often requires a good knowledge of the landslide characteristics and runout mechanics in this paper a quasi three dimensional model using lagrangian finite element method lfem is formulated to reproduce the dynamic runout process caused by landslides a case study of rainfall induced landslide on a natural slope in 1993 in lantau island hong kong is presented voellmy rheology is adopted to characterize the multi dimensional runout behaviour for engineering applications the selection of appropriate rheology and the determination of relevant key parameters associated with the failure mechanisms and runout mechanics are highlighted details of the mathematical formulation particularly with respect to the stability of the numerical scheme and quality control of the mesh are provided the close correlation between the calculation results and the field observations shows that if an appropriate rheological relationship is selected for the simulation a reasonable description of the runout behaviour can be obtained using the present model implications of the potential hazard from natural terrain landslides to downslope development are also discussed used in conjunction with geographical information system gis database the model can also be applied to the preliminary hazard zoning of terrain and land use management in mountainous areas

a debris avalanche at suphan stratovolcano turkey and implications for hazard evaluation the quaternary suphan debris avalanche deposit is located in eastern anatolia turkey the avalanche formed by the sector collapse of a major stratovolcano towards the north possibly during a single catastrophic event the deposit has an estimated volume of 4 km3 and ran out over 25 km to cover an area of approximately 200 km2 products of the collapse are overlain by younger eruptive units from the suphan volcano we have tested the numerical code volcflow to first reproduce the emplacement of the quaternary suphan debris avalanche and then to develop a hazard assessment for potential future sector collapses and subsequent emplacement of debris avalanches and associated tsunami the numerical model captures the main features of the propagation process including travel distance lateral spread and run up the best fit obtained for the existing flow has a constant retarding stress of 50 kpa and a collapse scar volume of 4 km3 analysis of potential future collapse scenarios reveals that northern sector debris avalanches up to 6 km3 could affect several towns in the case of a sector collapse towards the south a tsunami will reach the city of van and several of the biggest towns on the southern shoreline of lake van cities most affected by the larger amplitude waves would be van edremit gevas tatvan and to a lesser extent ercis with wave amplitudes first waves after the onset of the collapse between 8 and 10 m

quantitative models of sedimentary basin filling summary quantitative modelling of the filling of sedimentary basins was begun in earnest in the 1960s dozens of themes and variations have been proposed since then and have yielded an abundance of idealized stratigraphic patterns as functions of both imposed changes and basin properties post plate tectonic modelling began with rigid lid models which show the stratigraphic signature of subsidence variation this work introduced the connection between stratigraphy and the rheology of the lithosphere rigid lid models are the simplest type of geometric model in which the sediment surface is assigned prescribed geometries usually corresponding to different depositional environments these can reproduce many aspects of overall stratal geometry but are formally restricted to relatively long timescales for which quasi steady surface topography can be assumed so called dynamic models attempt to represent the morphodynamics of the sediment surface by abstracting and averaging short term transport processes most of the dynamic models proposed to date can be seen as special cases of a single general morpho dynamic equation the most important result of the first wave of quantitative basin filling models is that even relatively simple models can produce reasonable stratal patterns we now have a wide array of tools for exploring scenarios searching for general behaviours and effects and making initial quantitative predictions we have also learned that basin response to external forcing as recorded in stratigraphy can be as sensitive to the characteristics of the basin as to the forcing the main brake on the development of basin modelling is not computing power but lack of methods and data for testing the models we have already developed physical experiments which are only just beginning are one means of doing this experimental stratigraphy is a bridge to quantitative field tests which will require collaboration among academic researchers from a wide range of areas and between academia and industry on projects of greater scale and degree of integration than we have seen so far the advancement of quantitative sedimentary geology will also require significant changes in the way the subject is taught at all levels

propagation and deposition of stony debris flows at channel confluences the fluid dynamics of stony debris flows generated in two small tributaries adjacent to each other and flowing into a main receiving channel was analyzed experimentally at a laboratory scale the analysis on the propagation along the tributaries and deposition in the main channel provide information about sediment water mobility dangerous damming and potential hazard debris flows were generated by releasing a preset water discharge over an erodible layer of saturated gravels material as a consequence the debris flow sediment concentration varied accordingly to the entrainment rate which in turn was strongly controlled by the tributary slope the data collected by acoustic level sensors pore fluid pressure transducers and a load cell were used to characterize the evolution of bulk density and solid concentration of the sediment water mixture these two parameters were relevant to assess the stony debris flow mobility which contributes to determine the shape of sediment deposits in the main channel the detailed bed topography surveys carried out in the main channel at the end of each experiment provided information on the morphology of these deposits and on the interplay of adjacent confluences the influences of confluence angle tributary slopes and triggering conditions have been investigated for a total of 18 different configurations within the investigated range of parameters the slope angle was the parameter that mainly influences the stony debris flow mobility while for adjacent confluences the degree of obstruction within the receiving channel was strongly influenced by the triggering scenario

can the discharge of a hyperconcentrated flow be estimated from paleoflood evidence 1 many ood events involving water and sediments have been characterized using classic hydraulics principles assuming the existence of critical ow and many other simplications in this paper hyperconcentrated ow discharge was evaluated by using paleo ood reconstructions based on paleostage indicators psi combined with a detailed hydraulic analysis of the critical ow assumption the exact location where this condition occurred was established by iteratively determining the corresponding cross section so that specic energy is at a minimum in addition all of the factors and parameters involved in the process were assessed especially those related to the momentum equation existing shear stresses in the wetted perimeter and nonhydrostatic and hydrostatic pressure distributions the superelevation of the hyperconcentrated ow due to the ow elevation curvature was also estimated and calibrated with the psi the estimated peak discharge was established once the iterative process was unable to improve thet between the simulated depth and the depth observed from the psi the methodological approach proposed here can be applied to other higher gradient mountainous torrents with a similar geomorphic conguration to the one studied in this paper likewise results have been derived with fewer uncertainties than those obtained from standard hydraulic approaches whose simplifying assumptions have not been considered

holocene coastal evolution and uplift mechanisms of the northeastern raukumara peninsula north island new zealand abstract the coastal geomorphology of the northeastern raukumara peninsula new zealand is examined with the aim of determining the mechanisms of holocene coastal uplift elevation and coverbed stratigraphic data from previously interpreted coseismic marine terraces at horoera and waipapa indicate that despite the surface morphology there is no evidence that these terraces are of marine or coseismic origin early holocene transgressive marine deposits at hicks bay indicate significant differences between the thickness of preserved intertidal infill sediments and the amount of space created by eustatic sea level rise therefore uplift did occur during early holocene evolution of the estuary the palaeoecology and stratigraphy of the sequence shows no evidence of sudden land elevation changes beach ridge sequences at te araroa slope gradually toward the present day coast with no evidence of coseismic steps the evolution of the beach ridges was probably controlled by sediment supply in the context of a background continuous uplift rate no individual dataset uniquely resolves the uplift mechanism however from the integration of all evidence we conclude that holocene coastal uplift of this region has been driven by a gradual aseismic mechanism an important implication of this is that tectonic uplift mechanisms do vary along the east coast of the north island this contrasts with conclusions of previous studies which have inferred holocene coastal uplift along the length of the margin was achieved by coseismic events this is the first global example of aseismic processes accommodating uplift at rates of 1 mm yr 1 adjacent to a subduction zone and it provides a valuable comparison to subduction zones dominated by great earthquakes

formation of fluvial hanging valleys theory and simulation 1 although only recently recognized hanging tributary valleys in unglaciated tectonically active landscapes are surprisingly common stream power based river incision models do not provide a viable mechanism for the formation of fluvial hanging valleys thus these disequilibrium landforms present an opportunity to advance our understanding of river incision processes in this work we demonstrate that thresholds apparent in sediment flux dependent bedrock incision rules provide mechanisms for the formation of hanging valleys in response to transient pulses of river incision we simplify recently published river incision models in order to derive analytical solutions for the conditions required for hanging valley formation and use these results to guide numerical landscape evolution simulations analytical and numerical results demonstrate that during the response to base level fall sediment flux dependent incision rules may create either temporary or permanent hanging valleys these hanging valleys form as a consequence of 1 rapid main stem incision oversteepening tributary junctions beyond some threshold slope or 2 low tributary sediment flux response during the pulse of main stem incision thus limiting the tributary s capacity to keep pace with main stem incision the distribution of permanent and temporary hanging valleys results from four competing factors the magnitude of base level fall the upstream attenuation of the incision signal the lag time of the sediment flux response and the nonsystematic variation in tributary drainage areas within the stream network the development of hanging valleys in landscapes governed by sediment flux dependent incision rules limits the transmission of base level fall signals through the channel network ultimately increasing basin response time

rheology of concentrated granular suspensions and possible implications for debris flow modeling 1 granular suspensions are of major relevance for many geophysical flows we investigated the rheological behavior of three samples taken from a debris flow deposit at varying solid concentration from 38 0 to 54 2 by volume and grain size distribution experiments were performed first on the fraction finer than 0 075 mm and then on suspensions with fine sand up to 0 425 mm in size and percentages varying from 10 to 50 a vane apparatus connected to a rotational rheometer was used and experiments showed a reproducibility within 12 results were processed by the tikhonov regularization method in order to convert the shear stress versus rotation velocity curves to shear stress versus shear rate flow curves at shear rates lower than 3 5 s 1 shear stress is rate independent at higher shear rates the shear stress increases depending on the maximum grain particles included within the suspension we used the herschel bulkley and bingham models to describe the monotonous increase of the flow curves varying the grain size distribution of the samples the power and consistency indexes range within 0 75 1 35 and 0 44 40 8 pa s n where n is the exponent of the viscosity coefficient varies from 1 0 to 47 2 pa s and the shear stress varies from 28 to 1959 pa for materials mainly composed of silt and clay with a variable sand content 1 an increase in the particle size changes the rheological behavior from shear thinning to shear thickening and 2 the percentage of sand affects both the frictional character of the flow and the magnitude of the rheological parameters

geotechnical and rheological characteristics of waste rock deposits influencing potential debris flow occurrence at the abandoned imgi mine korea mass movements associated with abandoned mines are dangerous and destructive local communities near abandoned mine sites are often threatened by the effect of extreme precipitation events on these sites in this study the geotechnical and rheological characteristics of mine deposits were examined to delimit the hazardous areas near abandoned mines waste rock materials were collected from a pyrophyllite mine deposit in the mountainous region of korea and a sieve analysis was performed to determine the grain size distribution the yield stress in the debris flow modeling was determined using fall cone and rheometric tests rheological tests were performed on materials finer than 4 75 mm using a ball measuring system rheometer these samples were mainly composed of gravels and sands with small clay content the waste materials typically exhibited a shear thinning behavior within a given shear rate ranging between 10 5 and 102 s 1 the yield stresses obtained from the rheometric tests agreed well with those obtained from the fall cone tests for the input parameter we selected the yield stresses ranging from 100 to 500 pa as a case study the debris flow mobility associated with the abandoned mine was examined using a one dimensional flow dynamic model the runout distance and velocity of the waste materials are strongly dependent on the yield stress both factors significantly increase with decreasing yield stress however even under the highest yield stress i e 500 pa the failed mass can flow into the mountain stream thus the physico chemical contaminations of areas downslope of abandoned mines may be unavoidable with respect to extreme rainfall events

flow behavior and mobility of contaminated waste rock materials in the abandoned imgi mine in korea abstract incomplete mine reclamation can cause ecological and environmental impacts this paper focuses on the geotechnical and rheological characteristics of waste rock materials which are mainly composed of sand size particles potentially resulting in mass movement e g slide or flow and extensive acid mine drainage to examine the potential for contaminant mobilization resulting from physicochemical processes in abandoned mines a series of scenario based debris flow simulations was conducted using debris 2d to identify different hazard scenarios and volumes the flow behavior of waste rock materials was examined using a ball measuring rheometric apparatus which can be adapted for large particle samples such as debris flow bingham yield stresses determined in controlled shear rate mode were used as an input parameter in the debris flow modeling the yield stresses ranged from 100 to 1000 pa for shear rates ranging from 10 5 to 102 s 1 the results demonstrated that the lowest yield stress could result in high mobility of debris flow e g runout distance 700 m from the source area for 60 s consequently the material contaminants may easily reach the confluence of the suyoung river through a mountain stream when a fast slide or debris flow occurs at or near an abandoned mine area it may result in extremely dynamic and destructive geomorphological changes even for the highest yield stress of debris flow simulation i e y 2000 pa the released debris could flow into the mountain stream therefore people living near abandoned mines may become exposed to water pollution throughout the day to maintain safety at and near abandoned mines the physicochemical properties of waste materials should be monitored and proper mitigation measures post mining should be considered in terms of both their physical damage and chemical pollution potential

an opportunity to connect the morphodynamics of alternate bars with their sedimentary products field investigations that help clarify local sedimentary processes involved in the migration of alternate bars as a consequence of flood events are lacking a simple approach combining scour chains stratigraphy and frequent bathymetric surveys is proposed to connect the dynamics of free migrating alternate bars present in disconnected channels of large sandy gravelly rivers with their sedimentary products and vice versa the results show that the spatial distribution of bars before a flood partly governs the scour and fill processes and that the sediment transport rates vary significantly on a single cross section this can be due to preferential axes of the migration of the bars determined by their location on the cross section the bank direction and the discharge the approach allows the reconstruction of local sedimentary processes involved in alternate bar migration by combining maximum scour depths reached during a flood with frequent channel bed topography surveys and post flood stratigraphy it is also possible to distinguish deposited and preserved sediments compared with sediments by passed during the flood copyright 2011 john wiley sons ltd

evolution of debris flow properties and physical interactions in debris flow mixtures in the wenchuan earthquake zone abstract the 2008 wenchuan earthquake triggered an exceptional number of landslides the large amount of loose landslide materials on the steep terrains can easily turn into debris flows by heavy rainfall during the wet seasons from 2008 to 2011 five destructive debris flows occurred repeatedly in yingxiu the study area near the epicenter this paper presents the evolution of debris flow properties and physical interactions in the debris flow mixtures in the past few years seven dimensionless numbers are used to describe the physical interactions the evolution of the physical interactions over time was influenced by changes in debris flow compositions which in turn affected the runout characteristics of the debris flows significantly grain contact friction was the most important physical interaction for the five debris flows in the study area with gradual loss of fine particles over time the viscosity of the debris flow mixtures became lower and lower leading to a change from the dominance of viscous shear over solid fluid interactions and inertial grain collision to the dominance of solid fluid interactions and inertial grain collision over viscous shear with inertial grain collision being more and more important the flow resistance of the debris flows increased the mobility of the future debris flows may become smaller and smaller