anthropogenic influence on sedimentation and intertidal mudflat change in san pablo bay california 1856 1983 analysis of a series of historical bathymetric surveys has revealed large changes in morphology and sedimentation from 1856 to 1983 in san pablo bay california in 1856 the morphology of the bay was complex with a broad main channel a major side channel connecting to the petaluma river and an ebb tidal delta crossing shallow parts of the bay in 1983 its morphology was simpler because all channels except the main channel had filled with sediment and erosion had planed the shallows creating a uniform gently sloping surface the timing and patterns of geomorphic change and deposition and erosion of sediment were influenced by human activities that altered sediment delivery from rivers from 1856 to 1887 high sediment delivery 14 1 10 6 m 3 yr to san francisco bay during the hydraulic gold mining period in the sierra nevada resulted in net deposition of 259 14 10 6 m 3 in san pablo bay this rapid deposition filled channels and increased intertidal mudflat area by 60 37 4 3 4 to 60 6 6 2 km 2 from 1951 to 1983 23 3 10 6 m 3 of sediment was eroded from san pablo bay as sediment delivery from the sacramento and san joaquin rivers decreased to 2 8 10 6 m 3 yr because of damming of rivers riverbank protection and altered land use intertidal mudflat area in 1983 was 31 8 3 9 km 2 similar to that in 1856 intertidal mudflat distribution in 1983 however was fairly uniform whereas most of the intertidal mudflats were in the western part of san pablo bay in 1856 sediment delivery through its affect on shallow parts of the bay was determined to be a primary control on intertidal mudflat area san pablo bay has been greatly affected by human activities and will likely continue to erode in the near term in response to a diminished sediment delivery from rivers 2007 elsevier ltd all rights reserved

yangtze river derived sediments in the southwestern south yellow sea provenance discrimination and seasonal transport mechanisms abstract the southwestern south yellow sea sys is influenced by tremendous sediment loads derived from the yellow river huanghe and the yangtze river changjiang however the influence of yangtze river sediments and their transport mechanism in this area remain unresolved in this study we present the grain size clay minerals and elemental compositions of surface sediments from the southwestern sys together with an analysis of field observation seawater salinity and suspended sediment data to investigate the provenance and transport mechanism of the sediments discrimination diagrams of clay minerals cr th vs sc al and rare earth elements rees indicate that the southwestern sys sediments are mainly derived from the old yellow river subaqueous delta and the yangtze river interestingly yangtze sediments enter the sys in ways that differ seasonally in summer yangtze sediments may be transported into the central sys by the dispersion of changjiang diluted water cdw and may also be transported northwestward by the subei coastal current scc to the area off the jiangsu coast in winter the yangtze derived sediments deposited off the jiangsu coast in summer are transported into the central and or even north sys under the combined effects of the scc yellow sea coastal current yscc and yellow sea warm current yswc throughout the transport processes there is an alternation between a source and sink of yangtze sediments off the jiangsu coast the coast serves as a sink of yangtze sediments in summer but as a source of sys sedimentation in winter the depositional and transport mechanisms of yangtze derived sediments are closely associated with seasonal variations in the circulation system of the sys

cretaceous tertiary and permian triassic boundary events compared abstract the cretaceous tertiary k t and permian triassic p tr events differ in many more aspects than they are similar this alone makes it unlikely that they are parts of a common web of periodic mass extinction events mee unlike the k t most mee have no ir anomalies and where in the comparatively complete section of the p tr at gartnerkofel austria weak ir concentrations are found their ratios to siderophile elements co ni cr are far less than chondritic in contrast ratios to chalcophile elements as sb zn never approach chondritic even in k t peaks and locality differences suggest local depositional processes that may also affect the siderophiles profiles of isotopes 13ccarb 87 sr 86 sr and possibly 18ocarb across these boundaries also differ radically whereas the k t profile of surface ocean 18ocarb has been shown to be mainly a drop in primary productivity the p tr profile is interpreted at least in part to be a consequence of a large and accelerating oxidation of previously stored corg with greatly differing consequences for climate these and other differences of proximate forcings for these two mee lead us to a hypothesis that such external exigencies were ever intermittently and severally with us but were effective only when the biotic web had already internally unravelled in some crucially strained patch gaia became antigaia

influence of kinematics on landslide mobility and failure mode geometry of discontinuities greatly influences the kinematic behavior of slopes and landslides discontinuous deformation analysis dda is used here to analyze two typical examples of slope failure demonstrating that accurate representation of the geometry of the discontinuities is essential for identification of kinematically correct failure modes then static stability analyses of the vaiont italy landslide of october 9 1963 are used to show that the dda results compare favorably with previously published limit equilibrium studies using similar geometries and that the location and number of discontinuities have a significant effect on the predicted stability and failure velocities of the landslide dynamic dda simulations of the vaiont landslide show that the peak velocity increases up to 50 as the number of blocks increases indicating that internal disintegration of the landslide mass results in increasing acceleration and higher peak velocity dda analyses simulating pore pressure rise resulting from frictional heating of the basal slide plane show that the peak velocity similarly increases up to 50 as the number of blocks increases the magnitude of the increase in peak velocity as a result of disintegration i e increasing number of blocks suggests that as much attention should be paid to the geometry of discontinuities as is typically paid to shear strength and pore pressure

dynamic analysis of the multi staged ice rock debris avalanche in the langtang valley triggered by the 2015 gorkha earthquake nepal abstract on april 25 2015 a disastrous rock avalanche was triggered by the gorkha earthquake in the langtang valley of central nepal that buried a touristic village and killed 350 people this was a dual phase avalanche comprising of glacier snow ice and rock debris mixture which interacted in multiple paths from different source areas in this study the runout and deposition process of the langtang avalanche were analyzed using a two phase mass flow model pudasaini 2012 with the r avaflow software to recreate the flow heights velocity and deposition structure and sequence the simulation results indicated that the duration of the total failure process was 140 s and the avalanche flowed with an average velocity of 36 m s the interaction of the avalanche material from two different stages deflected its path directing it toward the downstream end of the valley and generating a splashing air blast which caused significant damage in that direction parameter calibration model performance and verification were performed numerically and based on field observations this study gave insight into the failure mechanisms of the dual phase and multi staged avalanche occurring in the snowline regions and explained the path deflections due to the stage interactions the results provide a reference for hazard zonation in such mountainous regions

numerical analysis of a landslide in soils with strain softening behaviour the results of an analysis concerning a landslide of great dimensions which occurred at senise southern italy on 26 july 1986 are presented the landslide was of a translational type and the failure developed within a thin clayey silt layer interbedded by a slightly cemented sand formation both these soils experienced a pronounced strain softening behaviour during laboratory tests from the analyses performed using the traditional limit equilibrium approach it has been found that the average operational resistance along the sliding surface was less than that of the peak and greater than the residual resistance deduced from the laboratory tests as a consequence it has been postulated that a progressive failure had occurred such a failure process can be appropriately studied using methods that are capable of simulating the formation and development of shear zones where strain is localised from a computational point of view this presents many difficulties because the numerical procedures current

seasonal variations of sediment discharge from the yangtze river before and after impoundment of the three gorges dam abstract over the past decades 50 000 dams and reforestation on the yangtze river changjiang have had little impact on water discharge but have drastically altered annual and particularly seasonal sediment discharge before impoundment of the three gorges dam tgd in june 2003 annual sediment discharge had decreased by 60 and the hysteresis of seasonal rating curves in the upper reaches at yichang station had shifted from clockwise to counterclockwise in addition the river channel in middle lower reaches had changed from depositional to erosional in 2002 during the four years 2003 2006 after tgd impoundment 60 of sediment entering the three gorges reservoir was trapped primarily during the high discharge months june september although periodic sediment deposition continues downstream of the tgd during most months substantial erosion has occurred supplying 70 million tons per year mt y of channel derived sediment to the lower reaches of the river if sand extraction 40 mt y is taken into consideration the river channel loses a total of 110 mt y during the extreme drought year 2006 sediment discharge in the upper reaches drastically decreased to 9 mt only 2 of its 1950 1960s level because of decreased water discharge and tgd trapping in addition dongting lake in the middle reaches for the first time changed from trapping net sediment from the mainstem to supplying 14 mt net sediment to the mainstem severe channel erosion and drastic sediment decline have put considerable pressure on the yangtze coastal areas and east china sea

a model for the analysis of rapid landslide motion across three dimensional terrain a new numerical model for the dynamic analysis of rapid flow slides debris flows and avalanches has been developed the model is an extension of an earlier algorithm and is implemented using a nu

stability of steep slopes in cemented sands the analysis of steep slope and cliff stability in variably cemented sands poses a significant practical challenge as routine analyses tend to underestimate the actually observed stability of existing slopes the presented research evaluates how the degree of cementation controls the evolution of steep sand slopes and shows that the detailed slope geometry is important in determining the characteristics of the failure mode which in turn guide the selection of an appropriate stability analysis method detailed slope profile cross sections derived from terrestrial lidar surveying of otherwise inaccessible cemented sand cliffs are used to investigate failure modes in weakly cemented unconfined compressive strength ucs30 kpa and moderately cemented 30ucs400 kpa sands and their role in the evolution of the geometry of the slopes the results show that high resolution slope topography such as can be obtained with terrestrial lidar is essential for identifying altogether different failure modes in weakly cemented shear mode and moderately cemented tensile mode sand slopes analyses show that the standard culmann method for steep slopes is inappropriate for modeling the stability of cemented sand slopes since it tends to overpredict expected crest retreat and underestimate failure plane angle instead a simplified analysis using infinite slope assumptions but applied to a slope with finite dimensions subject to changing geometric conditions such as toe erosion and slope steepening is suggested for analysis of weakly cemented sand slopes for moderately cemented sand slopes a limit equilibrium analysis directly comparing the cliff tensile stress and cemented sand tensile strength is shown to reasonably predict failure conditions and timing as a result of either slope steepening or tensile strength loss presumably from wetting in most cases doi 10 1061 ascegt 1943 5606 0000396 ce database subject headings slope stability sand soil type limit equilibrium tensile strength failure modes author keywords slope stability cemented sand limiting equilibrium tensile strength lidar cliffs failure mode

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

application of the material point method to simulate the post failure runout processes of the wangjiayan landslide abstract the first part of the paper presents a brief description of the material point method mpm including the governing equations solution scheme and a benchmark problem of soil collapse simulated using the method in the second and third part of the paper the post failure runout process of the wangjiayan landslide is simulated and analyzed the landslide s final topography and information from post failure in situ survey and laboratory tests are used to constrain the accuracy of computational results the kinematic behaviors of the failure mass are investigated in terms of displacement velocity effective plastic strain fields and topography changes during the movement comparisons are made between conditions with and without buildings on the deposition area numerical computations demonstrate that the presence of buildings on the sliding path strongly governs the flow regime run out distance velocity strain field and final deposition topography of the landslide so it is very essential to incorporate the effects of buildings in the modelling and analyses numerical results considering buildings show that the slide lasts about 30 s with the most rapid phase occurring between 6 and 12 s and that the maximum simulated velocity among the sliding particles in the landslide is 43 5 m s indicates that the moving of the landslide mass was very fast the run out distance simulated with mpm matches the measured post earthquake topography well whereas the shape of the simulated deposition zone is a little differs the buildings influence the sliding by shortening the overall run out distance decelerating the movement of the bottom layer and increasing the internal deformation and mixing among deposition layers

a conservative and consistent lagrangian gradient smoothing method for earthquake induced landslide simulation abstract numerical study of earthquake induced landslides plays an important role in the disaster prevention and post earthquake managements thanks to its mesh free feature the sph smoothed particle hydrodynamics method has significant advantages over the traditional grid based methods in dealing with extremely large deformation problems such as high speed fluid like landslides however sph is unstable when the material is in tension which is widely known as the tensile instability problem in sph although the instability issue can be removed to certain stand by particular ad hoc techniques the root cause of the problem is not addressed in addition such ad hoc techniques require additional user defined parameters which is difficult to make universally applicable in this study a conservative and consistent lagrangian gradient smoothing method l gsm is proposed for fluid like landslide simulations based on the recently developed meshfree l gsm in the present l gsm the strong form of governing equations is discretized using the gsm gradient operator in a conservative and consistent manner moreover a simple and accurate boundary treatment for free surface and solid boundary is newly proposed for l gsm to handle the complicated free surface and solid boundary existed in the landslide problems finally the proposed conservative and consistent l gsm framework is validated by a soil column collapse benchmark and three real landslide problems results show that our l gsm can give an accurate and reliable solution to the fluid like landslide problem with a high efficiency the treatments for free surface and solid boundary are also proven very effective in producing desired boundary conditions both cohesive soil column collapse example and wangjiayan landslide example demonstrate that l gsm is indeed free from the tensile instability problem

post failure stage simulation of a landslide using the material point method abstract traditional numerical methods such as the finite element method are usually used to analyse the slope response in the pre failure and failure stages under the assumption of small deformations however these methods are generally unsuitable for simulating the post failure stage of landslides due to the occurrence of large deformations the material point method mpm is a numerical technique capable to overcome this limitation in the present study mpm is used to carry out a two dimensional analysis of the run out process of the senise landslide that occurred in southern italy in 1986 accuracy of the method is assessed by comparing the final geometry of the landslide observed just after the event and the magnitude of the measured displacements to those provided by the numerical simulation the calculation results match fairly well the observed ones when two slip surfaces detected by the inclinometers are accounted for in the analysis an additional improvement of simulation is achieved taking into account the presence of some buildings and retaining walls existing in that area kinematics of the landslide is also investigated the results show that the senise landslide was a translational slide moving along two planar slip surfaces located in thin layers of clayey silt in addition these results demonstrate that a suitable analysis of the post failure stage can lead to a better understanding of the complex mechanical processes that characterise some landslides and thereby help in establishing the most effective stabilization measures

modeling the evolution of natural cliffs subject to weathering 2 discrete element approach the evolution of slopes subjected to weathering has been modeled by assuming mohr coulomb behavior and by using a numerical approach based on the discrete element method dem according to this method soil and or rock are represented by an assembly of bonded particles particle bonds are subject to progressive weakening and so the material weathering and removal processes are modeled slope instability and material movement follow the decrease of material strength in space and time with the only assumption concerning the weathering distribution within the slope first the case of cliffs subject to strong erosion weathering limited conditions and uniform weathering was studied to compare the results of the dem approach with the limit analysis approach second transport limited slopes subject to nonuniform slope weathering were studied results have been compared with experimental data and other geomorphologic models from the literature fisher lehmann and bakker le heux the flux of material from the slope is modeled assuming degradation both in space and time

an assessment of sediment transport processes in the lower mekong river based on deposit grain sizes the cm technique and flow energy data abstract the lower mekong river has been an important research topic for at least 15 years notably in the fields of hydrology fluvial geomorphology and the impact of dams recent papers refer mostly to the impact of the lancang chain of hydroelectric dams constructed on the chinese section of the river among the pending scientific questions are 1 the upstream downstream variations in the concentration and yield of suspended sediment and 2 the relative importance of sand in the total yield the general consensus among the scientific community is that the relative importance of sand in suspended load is not the main scientific concern despite its extensive presence in the mekong river channel as noted by geomorphologists and despite its extreme importance for the stability of the delta shoreline in viet nam this paper contradicts the general consensus its objective is to present new information on the processes of sand transport in the lower mekong channel imagery field observations sampling on the river banks and grain size analysis of sand deposits have been carried out between chiang sean downstream of the chinese border and the delta the c m image technique served to discriminate between the various transport processes bedload and different types of suspension this technique helps in understanding the changing processes responsible for downstream sediment transfer in river channels the results of this study are the following 1 discrepancies in the values of annual suspended sediment load detected by different gauging stations have not yet been satisfactorily explained the cm image technique indicates that grain size and the quantity of sand transiting in suspension vs bedload vary from upstream to downstream 2 these upstream downstream differences may be related to the energy of floods energy helps to explain longitudinal variations in the relative importance of the different modes of transport and serves to distinguish between bedload graded and uniform suspension and wash load 3 the mekong is seen as a river carrying mostly silt and clay however the results suggest that sand plays a major role in downstream sediment transfer during floods this result is in line with the large amounts of sand present in the channel its relative importance in the total yield must be reassessed as suggested by walling 2005 2008 as may be expected the role of sand in the stability of the delta shoreline is of prime importance

dynamic simulation of the motion of partially coherent landslides abstract rock avalanches are catastrophic landslides that threaten people and property worldwide the only way to mitigate the hazard posed by these events is to anticipate their impact area and velocity before they occur fluid dynamic models are one tool used to perform this kind of analysis when these models are applied to some rock avalanche case histories it has been found that the impact area is often over predicted this is due to the fact that the models assume that the landslide fluidizes immediately when in reality the landslide begins as a sliding of a relatively rigid block which progressively fragments during motion and only gradually turns flow like this work details the derivation implementation validation and verification of dan3d flex a dynamic model that can simulate the initially rigid phase of rock avalanche motion this model has been interfaced with an existing equivalent fluid model to allow for all stages of rock avalanche motion to be simulated dan3d flex only requires one additional parameter which can be constrained based on an examination of the pre failure topography the back analysis of two rock avalanche case histories is presented to demonstrate the utility of the new model

spatial patterns of scale effect on specific sediment yield in the yangtze river basin abstract this paper examines the spatial variation of sediment yield in the yangtze basin in china a large basin with complex geology climate land use history and extensive sediment monitoring 287 stations with drainage area less than 10 000 km2 were used to study the scale effects of sediment yield in order to develop scale relations for regional sediment yield the whole study area was divided into eight sub basins relation between specific sediment yield and drainage basin area was built for each sub basin regional scaling relation was analyzed based on landforms geology lithology and land use of each sub basin three regional trends were identified in relation to the drainage area 1 a declining trend due to soil erosion on heavily cultivated steep land and the storage of sediment in floodplains 2 a flat trend due to mass movement on the upper reach and heavy agricultural disturbance on the middle and lower reaches and 3 an increasing trend due to downstream recruitment of sediment from land downstream where slope farming and deforestation occurred using these developed relations areally adjusted sediment yield maps were created over the entire yangtze basin

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

dda validation of the mobility of earthquake induced landslides abstract this paper studies the run out of earthquake induced landslides there are more than 20 mechanical models to explain long run out of rapid landslides including some earthquake induced landslides however notably few of them considered the effect of seismic loading on the run out of landslides in a previous study we have proposed a model which is called the multiplex acceleration model mam to interpret the long run out mechanism and a shaking table test has been performed to verify the mam because the previous mam is a conceptual model and only a single stone has been examined under sine waves by the shaking table test the mam needs to be extended and further verified in this paper the mam was extended by introducing the movement change that was induced by the so called trampoline effect of earthquake loading and the latest practical numerical simulation program discontinuous deformation analysis dda was used to verify the mobility of earthquake induced landslides after a conceptual landslide model was used to verify the effect of seismic loading on the mobility the donghekou landslide which was a typical long run out landslide that was induced by the 2008 wenchuan earthquake was analyzed the results show that the seismic loading could be one of the factors that could eventually help increase the run out of landslides

provenance structure and formation of the mud wedge along inner continental shelf of the east china sea a synthesis of the yangtze dispersal system surficial grain size and down core clay mineralogical data show that sediment along the inner most part of the continental shelf in east china sea is mainly derived from the yangtze river changjiang spanning from the yangtze mouth 33 degrees n similar to 1000 km southward to the southwestern corner of the taiwan strait 24 degrees n high resolution chirp seismic profiles reveal an elongated mud wedge extending along the inner shelf with a northern depocenter on the modern yangtze delta and a southern depocenter at 27 5 degrees n four distinct acoustic units are delineated within the mud wedge from bottom up unit i late pleistocene mainly valley fills unit ii formed by transgressions thin strata unit iii 11 2 kyr bp downlapping strata and unit iv 2 0 kyr bp flat and opaque strata incised valleys up to 15 m deep are filled by flat lying or inclined strata in unit i the thin 3 m and acoustically transparent unit ii is only seen between 30 and 26 degrees n in water depths between 40 and 90 m separated by acoustically opaque strata or unconformities units iii and iv are widely distributed during the past 11 kyr yangtze sediment accumulation has been unsteady showing two high and one low accumulation rate periods the high accumulation period at 5 8 kyr bp may be related to maximum east asian summer monsoon precipitation in the yangtze basin the other high accumulation period 0 2 kyr bp probably reflects intensive human activities in the river s watershed the low accumulation rate period at 2 5 kyr bp which is seen in both northern and southern yangtze depocenters is probably related to low river discharge and or intensified taiwan warm current and china coastal current c 2011 elsevier b v all rights reserved

recent human impacts on the morphological evolution of the yangtze river delta foreland a review and new perspectives abstract this paper reviews the morphological change in the yangtze river delta due to increasing human impacts from three major aspects the first is the reduction of sediment supply to the ocean due to dam construction soil conservation and sand mining within the yangtze river basin the reduced sediment supply has decreased the progradation rate of the delta and triggered erosion in the front of the delta the second impact relates to the reclamation of intertidal wetlands by human activities since the 1950s approximately 1100 km 2 of intertidal land has been embanked resulting in the disappearance of salt marshes and even the entire intertidal zone along some sections of the coastline the third change in the delta due to human interference is the construction of deep waterway structures at the mouth bar which has greatly modified the local hydrodynamics and morphology sediment accretion has increased significantly in these areas as a result of sheltering by these deep waterway structures this review shows that human activities have severely altered the natural balance among the hydrodynamics and sediment supply affecting the morphological features of the yangtze river watershed and delta human impacts on the morphological evolution of deltaic coasts in general are becoming an increasingly concern and more attention should be paid to the management and mitigation of these effects

characteristics and runout behaviour of the disastrous 28 august 2017 rock avalanche in nayong guizhou china abstract on 28th august 2017 a disastrous rock avalanche occurred in nayong guizhou china this catastrophic event killed 35 people and destroyed 23 houses in this study the failure process of the avalanche was analyzed using uav video footage and seismic signal recordings obtained for the pre and post failure stages of the landslide to better understand the possible mechanism of the avalanche and its dynamic characteristics a numerical simulation was conducted using a dynamic model dan3d to simulate the runout behaviour of the displaced materials simulated results indicate that the failure process of the nayong rock avalanche lasted approximately 30 s the duration of the failure process is close to that from the uav video footage and seismic signal recordings 35 s the duration of movement during the landslide process is estimated to be approximately 90 s with a maximum velocity of 40 m s the combined frictional voellmy model delivered the most accurate results when simulating this event the selected models and parameters are expected to aid in clarifying the propagation processes of similar rock avalanches and thus improve the accuracy of hazard prediction in mountainous karst areas

dynamic deformation of quartz and feldspar clues to causes of some natural crises abstract indications of natural catastrophes and crises are preserved in some geologic strutures and in the stratigraphic record emphasizing the dynamic nature of the earth s evolution the crises may result either from exogenic or endogenic energy sources distinguishing between these sources is a complex multidisciplinary problem in the earth sciences shock deformation by impact has been well studied both in shock recovery experiments and in known impactites but only recently has the possibility of generation of shock waves by high temperature internal explosions been seriously considered an optically based reconaissance survey of microstructures in quartz and feldspar in some explosive silicic volcanics suggests that they may have been induced by dynamic deformation at high temperature in some respects the character of the microstructures differs greatly from those induced by room temperature shock whereas in others the differences are subtle results from recent shock recovery experiments on quartzite preheated to 440 and shocked to 28 gpa support this contention for two classic cretaceous tertiary sections at gubbio italy it is shown that shock mosaicism and shock lamellae occur over a 4 m interval bisected by the boundary in a pattern approximately correlatable with an independently established iridium enrichment these data are incompatible with any single event and are most plausibly interpreted as reflecting a period 0 5 my of intense probably episodic volcanism with a culmination at the k t transition multiple dynamic events may also account for macroscopic and microscopic structures developed during the evolution of the vredefort structure south africa

sediment sources and the flood record from wanghu lake in the middle reaches of the yangtze river a sediment core was collected from the centre of wanghu lake in the middle reaches of the yangtze river the recent part of the core was dated using a combination of pb 210 and spheroidal carbonaceous particle scp techniques extrapolating this chronology dated the laminated section of the core between 723 and 881 mm to the first half of the 18th century and this section was selected for detailed study the thicknesses of the laminae were measured using reflecting and polarizing microscopes whilst geochemistry was determined by an electron probe the thickness of the dark layers was found to be positively correlated with titanium concentrations and negatively correlated with aluminium and potassium concentrations the thickness of the light layers was found to be negatively correlated with the concentrations of titanium it is concluded that the dark layers were deposited from the fushui river a tributary of the yangtze river under periods of normal flow whilst the light layers were mainly deposited from the yangtze river itself during flood periods documentary evidence for floods occurring in the take catchment corresponded with thick laminations of high titanium concentration further two of the three thickest light laminations with low titanium concentrations were found to be synchronous with recorded flood dates of the main yangtze river in its middle reaches but one was synchronous with a local drought these data suggest that the lake sediment provides an archive of the relative water levels of the yangtze and wanghu including floods of both the main yangtze river and the local hydrological regime c 2006 elsevier b v all rights reserved

land use effects on sediment yields and soil loss rates in small basins of triassic sandstone near sydney nsw australia abstract sedimentation surveys of dams in small sandstone drainage basins near sydney australia demonstrate that land use is the dominant factor determining sediment yields and soil loss rates cultivated basins produce an average sediment yield of 7 1 t ha year whereas grazed pasture and forest woodland basins export averages of only 3 3 and 3 1 t ha year respectively nevertheless these yields are high by australian standards sediment exports from grazed pasture and forest woodland basins are similar because the forest woodland basins are also grazed dam sediments are enriched in clay and organic matter in comparison to topsoils gullies and bank erosion are not active geomorphic processes in the drainage basins investigated so that the measured sediment yields could be validly compared to soil loss rates determined by empirical soil loss equations modified universal soil loss equation musle soiloss and revised universal soil loss equation rusle which do not account for gully and channel erosion these equations accurately predicted the measured sediment yields with musle being the most accurate although soiloss is the only empirical equation to use australian data musle performed marginally better despite being a simplified version of the universal soil loss equation usle that is used for teaching rusle predictions of soil loss rates were also closely correlated with measured sediment yields

numerical simulation of qiaotou landslide deformation caused by drawdown of the three gorges reservoir china landslides located beside reservoirs tend to be unstable or are characterized by large deformation during the drawdown process this has been accepted by many experts in this paper we use qiaotou landslide which is located beside the three gorges reservoir tgr as a typical case study to investigate and predict the deformation mechanism during the drawdown process of tgr in detail according to field investigation the landslide mass is mainly composed of thick loose silt and clay mixed with fragments of rock bedrock is mainly composed of silty sandstone field and laboratory tests indicate that the landslide mass has a high permeability coefficient if the water level declines fast intense seepage force may result based on these data we establish a three dimensional geological model of qiaotou landslide by flac3d and perform a numerical simulation using the saturated unsaturated fluid solid coupling theory for the simulation we assume that the drawdown from 175 to 145 m takes place with a speed of 25 cm day which is based on the extreme water level regulation program of tgr the simulation shows that this causes a significant deformation in the landslide mass and that the maximum displacement within the landslide is 24 2 cm during the drawdown process the maximum displacement zone is shifting from the upper part of the landslide where bedrock surface is steeper and thickness of loose deposits is less to the middle part of the landslide where bedrock surface is less steep and thickness of loose deposits is higher the deformation mechanism indicates that in the early stage of the drawdown the deformation of the landslide mass is mainly caused by seepage and in the later stage mainly by consolidation

three dimensional material point method modeling of runout behavior of the hongshiyan landslide this study presents a field scale simulation of the hongshiyan landslide in china it uses an advanced numerical approach material point method or mpm and a constitutive model the drucker prager model rheological relation for the 3d simulation the performance of the developed mpm model is validated with laboratory scale experimental data on granular collapse before being applied to field scale analyses arcgis data are used to create a 3d mpm model of the soil body with complicated geometry although the developed model can describe the multiple phases of granular flow it focuses on the runout behavior of the landslide in this work the landslide is assumed to have occurred suddenly due to an earthquake and global sudden failure rather than progressive failure is modeled the mpm simulation results match reasonably well with the measured post earthquake topography e g deposit height of about 120 m and stretch length of about 900 m in the river and landslide duration of about 1 min the veloci

early palaeocene palaeoclimatic inferences from fossil floras of the western interior usa abstract twenty one early palaeocene floral assemblages were collected from a variety of alluvial depositional environments from sites in the williston powder river and raton basins of the western interior of the usa leaf fossils were assigned to morphotypes and their physiognomy was quantified for palaeoclimatic analysis two methods were used climate leaf analysis multi variate program clamp and leaf margin analysis lma temperature estimates and trends derived from clamp and lma indicate that early palaeocene palaeotemperatures decreased from the latest cretaceous particularly in northern areas of north america climatic zones shifted southwards from their latest cretaceous positions resulting in a steepened north south temperature gradient and decreased equability in the early palaeocene sub tropical conditions prevailed as far north as the raton basin with the 20 c mean annual temperature isotherm megathermal mesothermal boundary located at approximately 45 n palaeolatitude the 13 c mean annual temperature isotherm mesothermal microthermal boundary was located at approximately 55 n palaeolatitude to the south of the williston basin clamp estimates indicate that precipitation increased significantly in all areas sampled directly after the k t boundary event especially in the southern rockies precipitation levels decreased somewhat after this initial peak but remained high throughout the early palaeocene evidence from this and other studies suggests that seasonality increased from the latest cretaceous into the palaeocene and was most pronounced in central and northerly areas of the north american continent

sediment transport from the yangtze river china into the sea over the post three gorge dam period a discussion sediment loads from the yangtze river into the sea experienced a major increase in the late holocene when sand beaches along the deltaic coast changed into tidal flats sediment transport averaged about 472 million tons a year between the 1950s and the mid 1980s and decreased by 124 million tons a year after the mid 1980s followed by a dramatic drop since the closure of the three gorge dam tgd this paper discusses the major processes for the decline of sediment discharge since the 1950s and discusses the method for evaluating its future development over the post tgd period sediment loads in the post tgd period will be mainly determined by the major processes that may significantly contribute to the following three components i e 1 the sediment input from the upper basin into the three gorge reservoir tgr 2 the ratio of sediment export from the tgr relative to the input and 3 the amount of sediment recovery downstream the tgd restrained by available sediment sources an integrated evaluation shows that the annual sediment loads over the post tgd period will possibly vary from 1 12 to 1 32 million tons a year or less in ordinary years

the mechanism of high speed motion and damming of the tangjiashan landslide abstract understanding the mechanisms of landslide failure and resulting damming processes is crucial for constraining the hazard chain associated with landslide damming events on may 12 2008 the wenchuan earthquake caused a large number of secondary hazardous events such as landslides and collapses most of which occurred in high mountain gorges in these areas the sliding distance of landsides is often very short and the landslides are often characterized by high speed short distance and damming using the tangjiashan landslide damming events induced by the wenchuan earthquake as a model this paper reconstructs the three dimensional failure and associated damming caused by the landslide based on a detailed geological investigation of the landslide area and using the dynamic finite element technique the study proposes a four stage model for the failure and damming process of the tangjiashan landslide earthquake induction and progressive destruction of the slide body destruction and high speed sliding of the slide body slide body impact disintegration and river blockage for the formation of a damming body and vibration compression the average speed of the tangjiashan landslide reached a maximum value of 22 m s about 30 s after the earthquake and the landslide reached stability about 60 s later

influence of the three gorges dam on downstream delivery of sediment and its environmental implications yangtze river 1 water and sediment supplies from ungauged areas were calculated and combined with datasets from gauging stations to establish sediment budgets using sediment budgets and regression relationships the influence of the three gorges dam tgd on downstream delivery of sediment was quantified we found that 151 mt yr 1 mt 10 6 tons of sediment has been retained by tgd since it began operation 2003 2005 in response to this significant erosion has occurred in the downstream riverbed this erosion did not offset the sediment lost in the reservoir and the sediment flux into the estuary decreased by 85 mt yr 31 this decrease has lead to conversion from progradation to recession in the delta front in combination with other anthropogenic impacts tgd was expected to decrease the sediment flux into the estuary for centuries which is of great importance for delta ecosystem and human development citation yang s l j zhang and x j xu 2007 influence of the three gorges dam on downstream delivery of sediment and its environmental implications yangtze river geophys res lett 34 l10401

the impacts of the three gorges dam upon dynamic adjustment mode alterations in the jingjiang reach of the yangtze river china abstract dam operation profoundly modifies downstream flow sediment regimes resulting in a variety of geomorphologic responses without uniform laws the jingjiang reach of the middle yangtze river has undergone significant adjustment mode alterations with intensive channel erosion and major adjustment area changing from the bankfull channel to the medium flow channel at the time boundary of the three gorges dam tgd impoundment while these changes have received some attention little work has been undertaken to reveal the reason in this study based on 172 cross sections measured in the post flood period from 2003 to 2015 different river patterns longitude and reach averaged channel dimensions were assessed to reflect the channel adjustment characteristics of the jingjiang reach an index has been proposed to measure the cumulative water transport capacity of each discharge interval and to assess the relationship with reach scale medium flow channel dimensions the results indicate that the channel adjustment changes are directly driven by the alterations of flow duration and sediment transport capacity with the deficiency of floods medium flow channels respond quite well to small and medium discharges of under approximately 16 500 m3 s a discharge of 16 500 m3 s which can be regarded as a critical threshold corresponds to the average top levels of braided and meandering channel bars which are of morphological significance in constraining the passing flow in the medium flow channel small and medium discharges under the critical threshold associate with relatively larger reductions in sediment loads and hold increased geomorphic impacts qmjp eventually resulting in adjustment mode alterations the results present herein for the jingjiang reach of the yangtze river can provide a better understanding of dam operation and the corresponding impacts on downstream channel morphology

3d numerical modeling using smoothed particle hydrodynamics of flow like landslide propagation triggered by the 2008 wenchuan earthquake abstract the extremely strong wenchuan earthquake triggered thousands of landslides in sichuan province china flow like landslides such as the tangjiashan wangjiayan and donghekou landslides were among the most destructive causing many casualties and serious economic damage it is therefore important to identify the flow mechanisms and investigate the specific characteristics of these flow like landslides this paper presents a three dimensional model based on smoothed particle hydrodynamics sph to simulate rapid landslide motion across 3d terrain the navier stokes equations in a cfd framework are used as governing equations and artificial viscosity is incorporated into the pressure terms in the momentum equation to dissipate energy to avoid numerical oscillation and particle penetration thus improving the stability of the numerical results a non newtonian fluid model the bingham model has proven suitable for describing the relationship between the shear strain rate and the shear stress in highly deformed soil materials in the proposed model it is used as the constitutive model to describe the fluidization characteristics of flow like landslides combined with the mohr coulomb yield criterion the model incorporates a no slip boundary condition to consider the effect of a solid boundary on slope movement ghost particles are created and assigned an artificial velocity the viscous force caused by the solid boundary is calculated using the relative velocities between the fluid and the boundary particles open multiprocessing openmp an api for multi platform shared memory parallel programming is used to improve the efficiency of the sph code running to show the validity of the proposed approach a benchmark problem of 3d dam break was simulated the calculated distances of the surge front at different times agree well with the test results numerical modeling of the propagation of the tangjiashan wangjiayan and donghekou landslides was performed by the application of sph models to real flow like landslides the whole flow processes of these flow like landslides across the 3d terrain are represented the landslides change direction split or join in and spread or contract in their flow path in response to the local topography time history curves of the velocity and displacement were obtained to analyze the movement characteristics of the landslide mass the shapes of the deposition zones after slide occurrence were investigated comparisons of the sph simulated geometry and the surveyed landslide configurations for the tangjiashan wangjiayan and donghekou landslides were conducted and show a high degree of similarity this indicates that the proposed 3d sph model can accurately represent the evolution of the final slide shape the prediction of the fluidization characteristics of earthquake induced flow like landslides can notably reduce sudden loss of life as it provides a means for mapping hazardous areas for estimating the hazard intensity and for identification and design of appropriate protective measures

application of virtual earth in 3d terrain modeling to visual analysis of large scale geological disasters in mountainous areas sudden large scale geological disasters can be triggered in mountainous areas by events such as earthquakes rainfall volcanic eruptions or human activity leading to serious loss of life and property generating digital elevation model dem for such geological disasters allows the rapid identification of affected areas which is essential for emergency response and hazard mitigation the main aim of this study is to propose a low cost and efficient method based on virtual earth to generate a three dimensional 3d dem based on the terrain model numerical simulations can be conducted and the results integrated with virtual earth to perform 3d visualization and visual analysis the method proposed in this study may solve some limitations existing in other more traditional methods for example historical topographic maps exist mostly in paper format which is not conducive to spatial analysis while interpretation of remote sensing images generally requires professional knowledge at a high cost the emergence of the virtual earth platform of google earth ge provides new possibilities for generating terrain models terrain information can be extracted efficiently and freely from ge using an application programming interface api and then used to generate dem in this paper the donghekou landslide debris flow triggered by the 2008 wenchuan earthquake was selected as a case study 3d visualization of the temporal spatial dynamic process of a natural disaster was carried out by combination of the numerical results and ge imaging the comparison of the study case with field survey data proves the validity of the proposed method as it describes the real terrain shape and determines the slide distance accurately although the elevation error may be large the free and easy to use method proposed here can provide an intuitive basis for hazard assessment and rapid responses to geological disasters

paleoenvironmental significance of clay mineral associations at the cretaceous tertiary passage abstract the clay mineral stratigraphy at the cretaceous tertiary transition is considered by the study of new sections walvis ridge maud rise central italy northern tunisia which are compared with results of previous investigations increased contents of smectite and or kaolinite or substrate derived species e g illite group depending on the areas investigated are observed near the boundary these diversified modifications indicate increased erosion and predominance of local detrital supply including that of volcanic rocks over general related causes most probably these modifications of clay mineral associations express a major geodynamic disruption characterized by tectonic instability and sea level drop those events began prior to the cretaceous tertiary boundary i e prior to the major iridium anomaly recorded in sediments this could explain why a catastrophic event at the cretaceous tertiary boundary is hardly evidenced in the clay sedimentological record which is extremely sensitive to the global changes in the earth s terrestrial environment

a sph depth integrated model for popocatepetl 2001 lahar mexico sensitivity analysis and runout simulation abstract lahars are debris flows of volcanic origin which can endanger or even destroy communities located near the flanks of volcanoes lahars are not always triggered by eruptions they can form during heavy rainfall or after hydrothermal alteration and volcanic edifice collapse decision makers need lahar hazard maps to devise hazard prevention measures that will prevent casualties so lahar modelling is an important tool for assessing flow behavior and determining inundation areas the depth integrated numerical model used in this study is derived from the velocity pressure of the biot zienkiewicz model and was discretized using the smoothed particle hydrodynamics sph method to simulate a lahar that occurred at popocatepetl volcano in 2001 in order to investigate the convergence of the model we used a range of different sph mesh resolutions once the optimum mesh resolution was bounded we analyzed the model s sensitivity to the initial lahar volume the density of the geomaterial and the rheological parameter of the bingham fluid the results show that the sph depth integrated model produced a highly accurate simulation of the distribution and velocity of the 2001 lahar the study also shows the effects of sph mesh resolution and the relevant influence of rheological parameters

the impact of watershed management on coastal morphology a case study using an integrated approach and numerical modeling abstract coastal morphology evolves as the combined result of both natural and human induced factors that cover a wide range of spatial and temporal scales of effect areas in the vicinity of natural stream mouths are of special interest as the direct connection with the upstream watershed extends the search for drivers of morphological evolution from the coastal area to the inland as well although the impact of changes in watersheds on the coastal sediment budget is well established references that study concurrently the two fields and the quantification of their connection are scarce in the present work the impact of land use changes in a watershed on coastal erosion is studied for a selected site in north greece applications are based on an integrated approach to quantify the impact of watershed management on coastal morphology through numerical modeling the watershed model swat and a shoreline evolution model developed by the authors pelncon m are used evaluating with the latter the performance of the three longshore sediment transport rate formulae included in the model formulation results document the impact of crop abandonment on coastal erosion agricultural land decrease from 23 3 to 5 1 is accompanied by the retreat of 35 m in the vicinity of the stream mouth and show the effect of sediment transport formula selection on the evolution of coastal morphology analysis denotes the relative importance of the parameters involved in the dynamics of watershed coast systems and through the detailed description of a case study is deemed to provide useful insights for researchers and policy makers involved in their study

analysis of the chiufengershan landslide triggered by the 1999 chi chi earthquake in taiwan abstract a disastrous earthquake rocked taiwan on september 21 1999 with magnitude m l 7 3 and an epicenter near the small town of chi chi in central taiwan the chi chi earthquake triggered landslide on the dip slope at the chiufengershan in this study a review of the topography and geology of this area was followed by field investigations laboratory testing was applied to understand the geomaterial composing the slope then based on a series of limit equilibrium analyses the failure mechanism of this landslide and the risk of the residual slope were studied according to the stability analyses the pre quake slope is quite stable with factor of safety of 1 77 dry to 1 35 full groundwater level explaining why there is no written record of a landslide here for the past 100 years in contrast a back analysis shows that the chi chi earthquake induced dynamic loading is far more than the dip slope can sustain due in part to the short distance to the epicenter a monte carlo type probability analysis suggests that the residual slope is more dangerous than the pre quake slope and needs more attention

yangtze river of china historical analysis of discharge variability and sediment flux hydrological records covering a 100 year period from the upper middle and lower yangtze river were collected to examine the temporal and spatial distribution of discharge and sediment load in the drainage basin the yangtze discharge as expected increases from the upper drainage basin downstream only an estimated 50 of the discharge is derived from the upper yangtze with the rest being derived from the numerous tributaries of the middle and lower course however the distribution of sediment load along the yangtze is the reverse of that observed for discharge with most of the sediment being derived from the upper basin a dramatic reduction in sediment load by 0 8 108 tons year occurs in the middle yangtze because of a marked decrease in slope and the change to a meandering pattern from the upper yangtze rock sections considerable siltation also occurs in the middle yangtze drainage basin as the river cuts through a large interior dongting lake system sediment load in the lower yangtze while significantly less than that of the upper river is somewhat higher than the middle yangtze because of additional load contributed by adjacent tributaries a strong correlation exists between the discharge and sediment load along the yangtze drainage basin during the dry season as lower flows carry lower sediment concentration during the wet season a strong correlation is also present in the upper yangtze owing to the high flow velocity that suspends sand on the bed however a negative to poor correlation occurs in the middle and lower yangtze because the flow velocity in these reaches is unable to keep sand in suspension transporting only fine grained particles downstream hydrological data are treated for 30 years 1950 1980 when numerous dams were constructed in the upper yangtze drainage basin at yichang and hankou hydrological stations records revealed a decreasing trend in annual sediment load along with slightly reduced annual discharge at the same stations this can be interpreted as the result of water diversion primarily for agriculture sediment load at datong further downstream is quite stable and not influenced by slightly reduced discharge furthermore sediment concentration at the three hydrological stations increased which can be attributed to sediment loss in association with intensifying human activity especially in the upper drainage basin such as deforestation and construction of numerous dams mean monthly sediment load of these 30 years pulses about 2 months behind discharge implying dam released sediment transport along the entire river basin during the high water stage

predicting the terrestrial flux of sediment to the global ocean a planetary perspective a new model for predicting the long term flux of sediment from river basins to the coastal ocean is applied to a global data set of 340 river basins the model is based on relief basin area or averaged discharge and basin averaged temperature basinaveraged temperature is determined from basin location latitude longitude and the lapse rate across the basin relief hypsometric approximation the sediment flux model incorporates climate through basin temperature and hydrologic runoff solutions are provided for each of the major hemispheric climate regions polar temperate and tropic the model successfully predicts the pre anthropogenic flux of sediment to within the uncertainties associated with the global observations within a factor of two for 75 of rivers that range across five orders of magnitude in basin area and discharge most of the problem rivers are associated with low observational loads often smaller rivers where anthropogenic impacts are often magnified and temporal variability is high model predictions provide a baseline for researchers 1 to question the quality of observational data where available and disagreement is greatest 2 to examine a river basin for unusually large anthropogenic influences i e causes of erosion or causes of hinterland sediment retention and 3 to uncover secondary factors not addressed by our model lithology lakes the model provides a powerful tool to address the impact of paleo climate fluctuations warmer colder wetter drier on the impact of sediment flux to the coastal ocean d 2003 elsevier b v all rights reserved

on characteristics and dynamic analysis of the niumian valley rock avalanche triggered by the 2008 wenchuan earthquake sichuan china on may 12 2008 a large catastrophic rock avalanche was triggered by the wenchuan earthquake on niumian valley in yingxiu town wenchuan county china the displaced landslide materials traveled about 2 640 m with a descent of about 850 m and buried several houses and caused nearly 20 casualties based on detailed field investigation some basic characteristics of this landslide are introduced field investigation showed that the displaced landslide materials experienced three times of run up and twice of superelevation along the run out path and downslope enlargement due to the entrainment of run out path materials a numerical model dan3d is used to simulate the landsliding process by means of trial and error it can be seen that the voellmy model and values of friction coefficient f 0 19 dimensionless and turbulent coefficient xi 2 000 m s2 can provide the best performance in the prediction of sliding and depositing areas the simulated results show that the duration of the rock avalanche is about 120 s with an average velocity of 22 m s

tidal impacts on the subtidal flow division at the main bifurcation in the yangtze river delta flow division at bifurcations in the yangtze estuary has received ample attention since it may control the pathways of terrestrial sediments over downstream river branches including the 12 5 m deepwater navigation channel while some efforts have been made to interpret flow division at the bifurcations of the yangtze estuary little attention has been paid to the role of tides flow division at estuarine bifurcations is made complicated by tides that propagate from the outlet of the tidal channels into the delta to quantify the tidal influence on the distribution of river discharge and more generally to understand the mechanisms governing the subtidal flow division at the tidally affected bifurcation in the yangtze river delta a two dimensional hydrodynamic model is employed in this model the landward boundary is chosen beyond the tidal limit where the tidal motion has faded out entirely the seaward boundary is chosen such that the river discharge does not influence the water level subtidal discharges are decomposed using the method of factor separation to distinguish between the effects of tides river discharge and river tide interactions on the subtidal flow division results indicate that tides modify the river discharge distribution over distributary channels in the yangtze river delta particularly in the dry season a significant difference in the subtidal flow division during spring tide and neap tide shows that the tidally averaged flow division over the distributaries in the delta greatly depends on tidal amplitude by varying the river discharge at the landward boundary and amplitudes and phases of the principal tidal constituents at the seaward boundary of the established model the sensitivities of the subtidal flow division to the river discharge and tidal amplitude variation were investigated in detail generally the tidal impacts on the subtidal flow division are around 12 to 22 with river discharge varying from 30 000 m3s 1 to 20 000 m3s 1 this effect on the flow distribution can even overwhelm the effects induced by river discharge based on geometry only when the flow discharge is lowest furthermore the fortnightly tidal cycle plays an important role in enhancing the inequality of the subtidal flow division caused by the m2 tidal component solely at the tidal bifurcation in the yangtze river delta during low flow

temporal and spatial variations in magnetic properties of suspended particular matter in the yangtze river drainage and their implications abstract as the largest river of china the yangtze river transports large amounts of sediments to the adjacent oceans provenance of these ancient marine sediments can only be deciphered when the source to sink process of modern sediments in the yangtze river is fully understood many methods have been used to study the provenance of river sediment and an environmental magnetic method is applied in this study because of its fast nondestructive advantages magnetic properties of suspended particulate matter spm along the yangtze river were measured to provide a holistic understanding about magnetic properties of sediments in this river and its controlling factors the results indicate that the dominant magnetic mineral in spm is magnetite with a small contribution of hematite and goethite significant spatial variation was observed in most of the magnetic parameters which primarily reflects the distribution of major geologic units along the drainage area of the river anthropogenic influences are also recorded in the magnetic parameters the three gorges dam results in a dramatic decrease of magnetic minerals in the downstream reaches since its construction in 2003 in addition small variations in magnetic properties of spm are found along water depth together with a clear seasonal shift at datong station this seasonal variation of magnetic properties of spm is driven by variability in both hydrology and source contributions this complicates the use of magnetic parameters for provenance studies magnetic properties of sediments in rivers are capable of tracing provenance areas but caution must be taken into account

paleomagnetic constraints on the structure of the deccan traps abstract new paleomagnetic results from two widely separated areas of the deccan traps allow one to test the simple normal reversed normal nrn magnetostratigraphic model previously proposed the new data from the mandla region to the northeast of the main outcrop of the deccan traps together with earlier apparently conflicting results are all compatible with the nrn stratigraphy provided the flows are not strictly horizontal but have a synform antiform structure with 500 m amplitude and 150 km wavelength the structure parallels the paleozoic narmada son rift system with slopes never exceeding 0 5 sampling in rajahmundry a remote southeastern outlier of the deccan with well constrained age allowed identification of the rn boundary in an area where only normal polarities had been reported it has also been possible to correlate the detailed geochemical stratigraphy in the western ghats with the nrn magnetic stratigraphy a compilation of 35 magnetic studies together with the above findings confirms the general applicability of the nrn model and reveals the large scale topography of the rn boundary which is an isochron over most of the deccan the rn isochron surface displays a boomerang shape with topography ranging from sea level to above 1600 m this observed topography is consistent with a simple model in which doming and renewed rifting and dyke intrusion resulted from impingement 70 65 ma ago of the reunion plume under the indian lithosphere the narmada son rift was rejuvenated and a continental rift system with minor extension with a triple junction in the cambay graben resulted and was subsequently covered by the deccan flows although in places tectonic faulting and volcanism continued to interfere the rajahmundry outcrops constrain the original extent and southeastward dip away from the triple junction of much of the traps a significant part of which has now been removed by erosion and rifting away of the seychelles

constitutive flow behavior of a municipal solid waste simulant at post failure experimental and numerical investigations flow slides are relatively common environmental disasters that occur in municipal solid waste msw landfills and can result in serious consequences in surrounding regions this study presents experimental and numerical investigations into the constitutive flow behavior of a msw stimulant at post failure stage first a series of ring shear tests on msw simulant are conducted under varying shear rates the residual shear strength is observed to grow linearly as the shear rate increased which behaves like a kind of viscous fluid based on the results the concept of viscosity coefficient is introduced and a viscous fluid model is established to describe the constitutive behavior of the msw simulant at post failure stage this model is finally incorporated into a smoothed particle hydrodynamics sph code to simulate a flow slide model test the numerical results agree well with the test data thus verifying the applicability and reliability of the viscous fluid model to describe flow slide disasters in landfills

vajont disaster smoothed particle hydrodynamics modeling of the postevent 2d experiments abstractthe vajont disaster was caused in 1963 by a landslide of about 270 million cubic meters that fell into a hydroelectric reservoir and generated a wave about 200 m high which overtopped the dam and caused 1917 casualties with the aim of assessing why the real wave height was underestimated a series of two dimensional experiments were performed at the university of padua in 1968 considering a scale characteristic cross section of the vajont basin near the dam the landslide was pushed into the stored water by a moving plate over the sliding surface and the maximum wave run up along the opposite mountain side was measured as a function of the landslide falling time some of these results have been compared to smoothed particle hydrodynamics numerical simulations in which both water and noncohesive sediment are simulated as weakly compressible fluid water is treated as newtonian fluid while a proper rheological model is adopted for the landslide to mimic its non newtonian behavior the computed fall

the role of seismic triggering in a deep seated mudstone landslide china historical reconstruction and mechanism analysis abstract deep seated mudstone landslides are widely distributed in northwest china the zhengjiamo landslide occurred in 734 ce near taijing tianshui region it was triggered by the main shock of the historical ms 7 0734 ce earthquake the earthquake also induced a wide range of landslides in this area with hundreds of fatalities and many houses destroyed by landslide debris based on a detailed field survey borehole data and mapping a detailed geological reconstruction of the slope was achieved and the geo mechanical features of the claystone involved in the landslide were obtained using the particle flow code to simulate the mechanism of the zhengjiamo landslide the features of the landslide dynamics were obtained using a 5 stage model during the landslide process the slip mass at the front and upper edges exhibited higher mobility than at the rear and bottom edges furthermore the contact bond strength of the sliding body gradually weakened the model indicates that the particle bond strength has a larger influence on the maximum runout distance and landslide debris morphology than the type of weak intercalated layers the slip mass presented a rotational slide pattern and remained on the slip plane throughout the sliding process finally the earthquake uplifted the slope toe which prevented the slip mass from gliding the modelled scenario provided a reasonably good fit to the actual topography verifying the modelling results after the historical earthquake with the clay minerals swelling and shrinking under rainfall and efflorescence conditions the structure of the soft rock changed contributing to the weakening of the sliding rock mass the landslide gradually crept and evolved to its current topography

tracing acidification induced by deccan phase 2 volcanism abstract the deccan volcanic province dvp was built up by three major phases of eruptions the most voluminous of which the deccan phase 2 encompassed the cretaceous palaeogene kt boundary deccan eruptions have been implicated as a contributor to the end cretaceous mass extinction however mechanism by which volcanic activity affected biota remains poorly understood we applied a combination of rock magnetic techniques scanning electron microscopy to characterize mineral assemblages of three sections of intertrappean lacustrine sediments from the north western maharashtra deccan volcanic provinces our results indicate that in sediments deposited during the early stages of the deccan phase 2 the daiwal river and dhapewada sequences iron bearing mineral association is dominated by detrital iron oxides magnetite and hematite sourced from the weathering of the surrounding basaltic bedrocks with minor contribution form authigenic iron sulphides framboidal pyrite pyrrhotite and or greigite the sediments deposited during the final stages of phase 2 the podgawan sequence differ significantly in their characteristics in particular the podgawan sediments have 1 very low magnetic susceptibility values but higher terrigenous fraction clays and shales content 2 more complex assemblage of magnetic minerals 3 ubiquitous presence of fe ca ce vanadates and 4 unusual lithological variations in the middle part of the section represented by a charcoal rich level that is capped by a red clay layer containing fossilized bacterial colonies we suggest that these unusual characteristics reflect increased acidity in the region during the deposition of the podgawan sequence likely due to cumulative effects of volcanic aerosols released during the deccan phase 2 eruptions the combination of these features may be used to recognize episodes of increased acidity in the geological record our results also contribute to understanding of local vs global effects of the deccan volcanism

three dimensional run out analysis and prediction of flow like landslides using smoothed particle hydrodynamics many landslides can often be characterized as a sort of landslides which move rapidly like flowing fluid and thus have a long run out they usually cause large damage and casualties especially when they are trigged by an earthquake or heavy rain numerical simulations of flow like landslides are difficult due to the existence of free surface and large flow deformations in this work the smoothed particle hydrodynamics sph method is applied to model two and three dimensional flow like landslides for the run out analysis this is because sph method is a meshfree lagrangian particle method and is believed to be superior to conventional numerical methods in treating free surfaces moving interfaces and large deformations hence it is ideal in describing the complex fluidization characteristics in flow like landslides in this paper a bingham flow model and navier stokes equations are incorporated into the sph frame work in which fluids are discretized by flow particles and 3d terrain topography from gis is represented by surface or solid wall particles an improved sph method is first applied to simulate the whole run out processes of three flow like landslides which were triggered by wenchuan earthquake that occurred in china in 2008 the effectiveness of the improved sph method in modeling flow like landslides is demonstrated by the good agreement of the 3d profile simulation results obtained from the present sph simulation with field observation and results from other open sources the sph method is then used to predict the run out area of jinpingzi landslide

modelling of fast catastrophic landslides and impulse waves induced by them in fjords lakes and reservoirs abstract catastrophic landslides can cause impulsive waves in reservoirs fjords and other water bodies this work presents a methodology for modelling such phenomena we split the analysis into i initiation and ii propagation of the landslide iii entering of the wave in the water near field and iv far field propagation concerning initiation we use a coupled model in displacements and pore pressures together with a suitable constitutive model of the generalized plasticity type describing soil behaviour propagation is analyzed with a depth integrated model incorporating the fluidized soil rheology the third phase interaction of landslide and water is modelled with a level set algorithm which keeps track of the interfaces between solid air and water propagation in the far field is performed using a depth integrated model we will also present the results obtained with a double layer depth integrated model

evolution of the large landslide induced by typhoon morakot a case study in the butangbunasi river southern taiwan using the discrete element method abstract in 2009 typhoon morakot delivered high intensity rainfall and triggered many sites of large landslide which projected areas were larger than 10 000 m 2 from the satellite image especially in southern taiwan according to dtm analysis the material volume of the large landslide in butangbunasi river was more than four times larger than that of the nearly famous landslide disaster in hsiaolin village nevertheless the different movement of these two large landslides led to different disaster impacts based on literatures and field works the large hsiaolin landslide was a catastrophic landslide which had high velocity and less energy loss in the kinematic process the source area of the large landslide in the butangbunasi river on the other hand was composed of several landslide events and the kinetic energy dissipated when the landslide materials attained to riverbed in sequence in this study we divided the butangbunasi river large landslide into five slope units namely a b c d and e landslide events to recognize the mechanism of the large landslide and the simulation by using the particle flow code 3d pfc3d which is based on the discrete element method provided the kinematic process of the large landslide in the butangbunasi river it is noticed that most of the initial energy dissipated during the movement which the fist happening landslide event counteracted the crash of the follow up events and the residual energy gradually declined by the collision interaction of landslide blocks until the end of the large landslide the result helps to reconstruct the evolution of the large landslide from small scale landslide events and contributes to predict the affected region of the disaster it also reveals that even though the impact of the large landslide is reduced by sequent small scale landslide events there still remain secondary disasters such as landslide dam which show a high potential risk in the river valley and midstream

sediment budget of the yangtze river the sediment budget is a method to study the distribution of sediment in different parts of a river basin this paper studies the sediment budget of the yangtze river by analyzing the data on soil erosion size distributions of sediment deposits sediment load and fluvial process a method to determine the sediment budget for the yangtze river is proposed in which the total soil erosion from the upstream reaches and tributaries is divided into two parts sediment load transported to the yichang station and sediment storage in the tributaries and gullies furthermore the sediment load is divided into three parts bed material load deposited in the middle and lower reaches for the fluvial process wash load transported to the estuary and sediment deposition in tongting lake the sediment transported into the estuary is further divided into two parts very fine sediment drifting to the ocean and sediment deposition in the estuary for land creation there is a large sediment demand for 1 the fluvial process to reach the minimum stream power in the middle and lower reaches 2 sediment mining for building material and 3 land creation in the estuary the riverbed profile in the middle and lower reaches is developing toward the equilibrium profile defined by the minimum stream power but the impoundment of the three gorges reservoir interrupts and modifies this fluvial process the annual sediment load in the yangtze river has reduced due to various human activities by about 100 x 10 6 t in the past 15 years thus there is a sediment shortage for land creation in the river mouth

geotechnical assessment of the 2005 kuzulu landslide turkey in this study a complex landslide which occurred on 17 march 2005 near koyulhisar town of sivas province of turkey is presented the landslide resulted in 15 deaths and the destruction of about thirty houses at kuzulu village the main aims of this study are to assess the landslide in terms of engineering geology and geotechnics to back analyze the landslide in the source area and to estimate its motion and destructive forces on structures furthermore the effect of a future earthquake on stability condition of the mobilized but not completely failed mass adjacent to the right flank of the landslide is also investigated field observations eyewitnesses geomechanical laboratory tests interpretations on pre event aerial photographs and analyses using different approaches have been fundamentals of this study site observations indicate that the initial landslide in the source area occurred in highly weathered volcanics along a failure surface passing through the volcanics and along the interface between the volcanics and underlying limestone then the movement transformed into an earth flow and moved down through a v shaped channel in the underlying limestone about 2 km until it stopped at a small settlement which is called kuzulu site observations and back analysis of the initial slide suggest that the most likely cause should be water pressure increase as it is the season of snow melting and thawing of the groundwater interpretations on pre event aerial photographs and the information obtained from eyewitnesses indicated that slope movements in the study area where old landslide topography is evident were continuing for many years the simulation of the landslide with consideration of bingham type yielding criterion together with water pressure variation suggested that the maximum velocity of the earth flow was 14 4 m s and 13 6 m s when it reached kuzulu furthermore this evaluation showed that the earth flow reached kuzulu after 300 s which is consistent with the information obtained from local people the impact of the earth flow on the structures could be about 170 kpa against which only reinforced concrete structures may resist dynamic analyses suggested that a future earthquake which may occur in the region may result in a complete failure of the unstable mass remaining at the source area

dam impacts on the changjiang yangtze river sediment discharge to the sea the past 55 years and after the three gorges dam 1 in 5 recent years 2000 2004 the changjiang yangtze river has discharged past datong 600 km from the river mouth an average of 250 million tons mt of sediment per year a decrease of more than 40 since the 1950s and 1960s whereas water discharge at datong has increased slightly water and sediment discharge data from the upper middle and lower reaches of the river suggest that the reduction of the changjiang sediment load has occurred in two phases between 1950 and 2002 following the closure of the danjiangkou reservoir on the hanjiang tributary in 1968 and following the installation of numerous dams and water soil conservation works in the jialingjijang catchment after 1985 as the three gorges dam tgd started operating in 2003 the changjiang entered a third phase of sediment reduction with annual sediment loads at datong less than 200 mt yr upon completion of the three gorges dam tgd in 2009 the sediment load at datong will decrease to 210 mt yr for the first 20 years then will recover to 230 mt yr during 2030 2060 and will reach 310 mt yr during 2060 2110 from the sediment budget and sediment erosion data for the changjiang subaqueous delta it can be assumed that the delta will be eroded extensively during the first five decades after tgd operation and then will approach a balance during the next five decades as sediment discharging from tgd again increases

the consequences of land cover changes on soil erosion distribution in slovakia abstract soil erosion is a complex process determined by mutual interaction of numerous factors the aim of erosion research at regional scales is a general evaluation of the landscape susceptibility to soil erosion by water taking into account the main factors influencing this process one of the key factors influencing the susceptibility of a region to soil erosion is land cover natural as well as human induced changes of landscape may result in both the diminishment and acceleration of soil erosion recent studies of land cover changes indicate that during the last decade more than 4 11 of slovak territory has changed the objective of this study is to assess the influence of land cover and crop rotation changes over the 1990 2000 period on the intensity and spatial pattern of soil erosion in slovakia the assessment is based on principles defined in the universal soil loss equation usle modified for application at regional scale and the use of the corine land cover clc databases for 1990 and 2000 the c factor for arable land has been refined using statistical data on the mean crop rotation and the acreage of particular agricultural crops in the districts of slovakia the l factor has been calculated using sample areas with parcels identified by landsat tm data the results indicate that the land cover and crop rotation changes had a significant influence on soil erosion pattern predominately in the hilly and mountainous parts of slovakia the pattern of soil erosion changes exhibits high spatial variation with overall slightly decreased soil erosion risks these changes are associated with ongoing land ownership changes changing structure of crops deforestation and afforestation

deccan volcanism at the cretaceous tertiary boundary the accuracy with which one can claim that deccan trap volcanism occurred at the cretaceous tertiary boundary ktb over a very short time interval is of key importance in deciding whether a volcanic origin of the ktb events should be taken seriously in the two years since paleomagnetic paleontological and geodynamic evidence was published further data have become available and the case now appears to be well constrained the ar 40 ar 39 results from six labs have yielded some 24 reliable plateau ages that narrow the age range to 65 to 69 ma moreover it appears that a significant part of this range results from inter lab spread and possible minor alteration paleontology demonstrates that volcanism started in the maestrichtian more precisely in the a mayaroensis zone paleomagnetism shows that volcanism spanned only 3 chrons and only one correlation remains possible that of the main central reversed chron with 29r therefore whereas ar 40 ar 39 is able only to restrict the duration of volcanism to some 4 ma paleomagnetism restricts it to 0 5 ma using some geochemical indicators such as c 13 as proxy it is suggested that volcanism actually consists of a few shorter events of unequal magnitude extrusion rates may be as high as 100 cu km yr and fissure lengths as long as several 100 km such a scenario appears to be at least as successful as others in accounting for most anomalies observed at the ktb particularly important are iridium and other platinum group elements pge profiles sr 87 sr 86 c 13 0 18 other exotic geochemical signatures spherules soot shocked minerals selective and stepwise extinctions the environmental impact of co2 possibly released during explosive phases of volcanism and so2 released during effusive phases and the ability of volcanism to ensure worldwide distribution of ktb products are now all addressed in conclusion the case for a causal link between internal hotspot activity birth of the reunion hotspot itself as the deccan and ktb events appears to rest on an increasingly stronger basis