effect of groundwater regime on the behaviour of clayey slopes it is well known that many landslides which occur every year in the world are triggered by rainfall the mechanics of slope movements due to pore pressure changes are not completely understood h

formation of large beaches in an area of rapid differential isostatic rebound the three outlet control of lake agassiz abstract shorelines in basins undergoing differential isostatic rebound do not remain geographically fixed for long periods and are either transgressive or regressive during regression a relatively uniform blanket of shoreface sediment may be deposited but unless regression is slow or punctuated by periods of lake level equilibrium large beaches do not form in contrast along transgressive shorelines which migrate upslope large morphostratigraphic features commonly are maintained along the lake s margin these may subsequently be stranded when lake level declines beaches around isostatically rebounding proglacial lakes are commonly considered to have formed during a period of lake regression punctuated by abrupt drops in lake level however in basins that are differentially rebounding large beaches cannot form this way and only periods of transgressing waters allow enough time for large beaches to form and define a continuous shoreline around the basin with this in mind some of the largest and most extensive beaches in the glacial lake agassiz basin the norcross tintah and upper campbell constructed between 10 4 and 9 4 ka 14 c yr bp are reinterpreted as strandlines that were formed by transgression each of these three transgressions followed lower lake phases and resulted from in sequence differential isostatic rebound of the eastern outlet rebound and ice damming of the northwestern outlet and rebound of the northwestern outlet each of these transgressions ended when lake level reached the southern outlet stranding the norcross tintah and upper campbell beaches about 10 2 9 9 and 9 4 ka 14 c yr bp respectively

a model of the western laurentide ice sheet using observations of glacial isostatic adjustment we present the results of a new numerical model of the late glacial western laurentide ice sheet constrained by observations of glacial isostatic adjustment gia including relative sea level ind

characterization of the 3 d fracture setting of an unstable rock mass from surface and seismic investigations to numerical modeling the characterization of the fracturing state of a potentially unstable rock cliff is a crucial requirement for stability assessments and mitigation purposes classical measurements of fracture location and orientation can however be limited by inaccessible rock exposures the steep topography and high rise morphology of these cliffs together with the widespread presence of fractures can additionally condition the success of geophysical prospecting on these sites in order to mitigate these limitations an innovative approach combining non contact geomechanical measurements active and passive seismic surveys and 3 d numerical modeling is proposed in this work to characterize the 3 d fracture setting of an unstable rock mass located in nw italian alps madonna del sasso vb the 3 d fracture geometry was achieved through a combination of field observations and non contact geomechanical measurements on oriented pictures of the cliff resulting from a previous laser scanning and photogrammetric survey the estimation of fracture persistence within the rock mass was obtained from surface active seismic surveys ambient seismic noise and earthquakes recordings were used to assess the fracture control on the site response processing of both datasets highlighted the resonance properties of the unstable rock volume decoupling from the stable massif a finite element 3 d model of the site including all the retrieved fracture information enabled both validation and interpretation of the field measurements the integration of these different methodologies applied for the first time to a complex 3 d prone to fall mass provided consistent information on the internal fracturing conditions supplying key parameters for future monitoring purposes and mitigation strategies

reconstruction of landslide movements by inversion of 4 d electrical resistivity tomography monitoring data reliable tomographic inversion of geoelectrical monitoring data from unstable slopes relies critically on knowing the electrode positions which may move over time we develop and present an innovative inverse method to recover movements in both surface directions from geoelectrical measurements made on a grid of monitoring electrodes for the first time we demonstrate this method using field data from an active landslide to recover sequences of movement over timescales of days to years comparison with gps measurements demonstrated an accuracy of within 10 of the electrode spacing sufficient to correct the majority of artefacts that would occur in subsequent image reconstructions if incorrect positions are used over short timescales where the corresponding subsurface resistivity changes were smaller the constraints could be relaxed and an order of magnitude better accuracy was achievable this enabled the onset and acceleration of landslide activity to be detected with a temporal resolution of a few days

long term fluvial incision rates and postglacial river relaxation time in the french western alps from 10be dating of alluvial terraces with assessment of inheritance soil development and wind ablation effects studying river long profile development as a response to tectonic and climatic controls requires reliable age dating of paleo profile remnants preserved as river terraces cosmic ray exposure cre dating often represents the only method available to date river terraces but the interpretation of cosmogenic nuclide concentrations is complicated by pre depositional inheritance and post depositional disturbance of the terrace deposits through pedogenesis and surface inflation or deflation here we use cosmogenic 10be measurements to date alluvial terraces in the french western alps in order to estimate river incision rates and to infer river response to climatic fluctuations and tectonic forcing we assess inheritance by constructing 10be concentration vs pebble depth profiles and use a monte carlo technique to estimate terrace ages we find that inheritance is negligible on all terraces enabling us to date terraces as young as 5 ky terraces that predate the last glaciation experienced intense pedogenesis and wind ablation which led to significant scatter in the 10be concentrations of surface samples we assess these effects using a model of 10be ingrowth and show that the oldest cre ages of surface clasts are close to the probable terrace age we study two catchments which have undergone varying degrees of glacial disruption the buech river experienced variations in runoff and sediment flux during the last glaciation as well as occasional ice dammings of its outlet its upper terraces record incision rates averaged over 190 ky of 0 8 mm yr consistent with denudation rates estimated in the surrounding areas and suggesting long term stability of river incision rates climatic forcing is well documented for the drac river which was repeatedly dammed by glaciers during cold periods its postglacial incision history was triggered by an 800 m drop in base level following ice dam disappearance long profile development by knickpoint propagation explains the time lag of 2 5 ky between this base level drop and terrace abandonment upstream as well as subsequent peak incision rates of 6 cm yr followed by a gradual decrease in incision rates the present knickpoint location 55 km upstream from the glacial damming site enables us to calculate a fluvial response time of 15 20 ky controlled by knickpoint propagation rates of several meters per year within the drac river

alternative routing of lake agassiz overflow during the younger dryas new dates paleotopography and a re evaluation abstract overflow from glacial lake agassiz has been implicated in affecting late glacial ocean circulation and climate the timing of the diversion of lake agassiz overflow away from its southern routing to the gulf of mexico correlates closely with the younger dryas ca 11 10 14 c ka new models of paleotopography in the eastern outlet region of lake agassiz adjusted for differential isostatic rebound show that overflow to the superior basin would have occurred when the lake formed its herman norcross and tintah beaches just after 10 9 14 c ka if the laurentide ice sheet lis had retreated from the thunder bay ontario region by that time however the absence of coarse flood deposits normally associated with large overflows plus the morphology of possible overflow channels in the thunder bay region suggest that agassiz overflow may not have been routed into the great lakes during the younger dryas as previously believed in addition non carbonate radiocarbon dates in the thunder bay area are all younger than 10 14 c ka suggesting that this area may not have been deglaciated until after the younger dryas thus preventing lake agassiz overflow through this area an alternative route of overflow from lake agassiz during the younger dryas could have been through the northwestern clearwater outlet to the arctic ocean although all research to date shows that this region was covered by ice until 10 14 c ka on the other hand it is possible that older and coarser overflow sediment may now lie buried beneath finer deposits associated with the 10 14 c ka marquette readvance of the lis which ponded waters in valleys between lake agassiz and lake superior or that eastward overflow in this area was not catastrophic

application of time lapse ert imaging to watershed characterization time lapse electrical resistivity tomography ert has many practical applications to the study of subsurface properties and processes when inverting time lapse ert data it is useful to proceed beyond straightforward inversion of data differences andtakeadvantageofthetime lapsenatureofthedata weassess various approaches for inverting and interpreting time lapse ertdataanddeterminethattwoapproachesworkwell thefirst approachismodelsubtractionafterseparateinversionofthedata from two time periods and the second approach is to use the inverted model from a base data set as the reference model or prior information for subsequent time periods we prefer this second approach data inversion methodology should be considered when designing data acquisition i e to utilize the second approach it is important to collect one or more data sets for which the bulk of the subsurface is in a background or relatively unperturbed state athird and commonly used approach to time lapse inversion invertingthedifferencebetweentwodatasets localizes the regions of the model in which change has occurred however varying noise levels between the two data sets can be problematic to further assess the various time lapse inversion approaches weacquiredfielddatafromacatchmentwithinthedry creek experimental watershed near boise idaho u s a we combined the complimentary information from individual static ertinversions time lapseertimages andavailablehydrologicdatainarobustinterpretationschemetoaidinquantifyingseasonalvariationsinsubsurfacemoisturecontent

abandonment chronology of glacial lake agassiz s northwestern outlet abstract spillway scour lakes and basins in northwestern saskatchewan were cored to determine when the spillways were abandoned the cores contained the target contact of organic muck gyttja overlying inorganic sand or silty clay rhythmites new ams radiocarbon dates on terrestrial macrofossils in conjunction with previously published and unpublished data from the area indicate that the spillways were abandoned between 9 07 and 9 59 14c kyr bp 10 220 10 810 cal yr bp of great interest is whether the channels are associated with northwestern drainage from glacial lake agassiz the radiocarbon ages recording spillway abandonment are consistent with previous work which claims that overflow through the northwestern outlet ended 9 5 14c kyr bp 10 700 cal yr bp this is consistent with shifting drainage to the southern outlet at this time the scarcity of dates from the northwestern outlets and other outlets of lake agassiz underscores the need to establish a tighter chronological control on outlet switching before outburst flooding from lake agassiz can be assumed to be the trigger for abrupt climate change

soil engineering properties and failure mechanisms of shallow landslides in soft rock materials abstract tertiary soft rock strata exposed on the eastern side of changbai mountain are landslide prone strata in recent years shallow landslides have frequently occurred along the highway in this region leading to great challenges in highway construction and safe operations national highway 302 which is under construction crosses an old landslide group close to the village of xinyan a shallow landslide that recently occurred in this section the xinyan landslide which occurred in a road embankment composed of soft rock materials is studied herein as a case study the field survey identifies the geological characteristics and current conditions of the landslide area and confirms an inheritance relationship between the xinyan landslide and previous landslides through a laboratory geotechnical test mineral composition analysis and microstructure analysis of landslide soils it is found that the examined soft rock materials exhibit both dispersion and expansion the coupling effect of soil expansion and dispersion contribute to the formation of seepage channels and to the degradation of soil properties under the combined effects of these factors local shear failure first occurs at the weakest toe of the embankment then unloading effects and strain softening lead to the progressive propagation and expansion of the sliding surface finally the failure of the xinyan landslide enters a progressive failure mode from the slope toe to the interior area therefore this study reveals that expansibility dispersivity extremely low shear strength levels softening behavior and preferential flows are the main causes of the repeated failure of the gentle soft rock slopes in this region these results may serve as a good reference for the prevention and treatment of similar soft rock landslides occurring in the yanbian region or worldwide

image based mapping of surface fissures for the investigation of landslide dynamics abstract the development of surface fissures is an important indicator for understanding and forecasting slope movements landslide investigations therefore frequently include the elaboration and interpretation of maps representing their spatial distribution typically comprising intensive field work and instrumentation it is only recently that aerial photography with sub decimetre spatial resolution is becoming more commonly available and opens a window to analyse such features from a remote sensing perspective while these data are in principle helpful to elaborate maps from image interpretation techniques there is still no image processing technique available to extract efficiently these geomorphological features this work proposes a largely automated technique for the mapping of landslide surface fissures from very high resolution aerial images the processing chain includes the use of filtering algorithms and post processing of the filtered images using object oriented analysis the accuracy of the resulting maps is assessed by comparisons with several expert maps in terms of affected area fissure density and fissure orientation under homogenous illumination conditions true positive rates up to 65 and false positive rates generally below 10 are achieved the resulting fissure maps provide sufficient detail to infer mechanical processes at the slope scale and to prioritize areas for more detailed ground investigations or monitoring

prediction of the location of future rupture surfaces of a slowly moving loess landslide by electrical resistivity tomography a slowly moving loess landslide along the river danube in south hungary was studied using electrical resistivity tomography our aim was to determine the fracture system of the study site due to the homogeneous composition of the loess it seems to be the only possibility to get information about the landslide and its further evolution the applicability of the electrical resistivity tomography technique for such a supposedly dense fracture system was studied by numerical modelling and the results have been verified in the field the dip of the fractures could not always been observed and they could not be explored deeply however it was possible to map their surface projection to get the desired information about the structure of the landslide fracture zones could have been especially well localized enabling the prediction of the positions of future rupture surfaces and thus the delineation of the endangered zone although the area outside of the already subsided one is not endangered yet the area which has already started to move is going to break into two parts of the about 5 m wide blocks at the front of the landslide may fall or slide down anytime a large area was assumed to move as one unit most of our predictions have been verified by the mass movements that occurred about one and half years after the measurements the electrical resistivity tomography method proved to be a good tool to characterize the fracture system of such a landslide area enabling the prediction of future rupture surfaces and also delineation of the endangered area its use is therefore highly recommended to monitor landslides to provide early risk warnings to avoid damage to constructions or endangering human life

glacial lake saskatchewan and lake agassiz deltas in east central saskatchewan with special emphasis on the nipawin delta the nipawin delta extends eastward from the town of nipawin in east central saskatchewan the prince albert and fort a la corne deltas formed in lake saskatchewan at the mouths of the south and north saskatchewan rivers whereas the nipawin and mossy vale deltas formed in lake agassiz at the mouth of the saskatchewan river these deltas became lower in elevation and younger eastward clays beneath the nipawin and mossyvale deltas can be traced beneath the prince albert and fort a la corne deltas with little change in thickness suggesting that most of the clays beneath the nipawin and mossyvale deltas were deposited during the formation of the prince albert and fort a la corne deltas the nipawin delta formed between 10 200 and 9500 bp the campbell strandline emerson phase was the shoreline of the nipawin delta the mossyvale delta formed about 9500 bp the surface of the mossyvale delta mccauleyville level is about 40 m below the surface of the nipawin delta campbell level

possible stick slip behavior before the rausu landslide inferred from repeating seismic events a precursory sequence of repeating earthquakes was recorded before the rausu landslide in hokkaido japan on april 24 2015 there were two seismic sequences with each consisting of very similar waveforms and leading up to significant landslide movements the nearly identical waveform shapes indicate similar source locations and mechanisms so repeated events originated on a particular small area this sequence is interpreted as stick slip movement on a small patch leading up to the larger landslide failure our observations show that heterogeneous structure such as asperities on the slip surface can play an important role in the initiation of landslides adding a new aspect to the conventional understanding of mechanisms controlling large mass movements

deglaciation of a soft bedded laurentide ice sheet we present a series of numerical reconstructions of the laurentide ice sheet during the last deglaciation 18 7 14c ka that evaluates the sensitivity of ice sheet geometry to subglacial sediment deformation these reconstructions assume that the laurentide ice sheet flowed over extensive areas of water saturated deforming sediment soft beds corresponding to the st lawrence lowland the great lakes region the western prairies of the u s and canada and the hudson bay and hudson strait regions sediment rheology is based on a constitutive law that incorporates experimental results from late wisconsin till deposited by the laurentide ice sheet which suggest only mildly nonlinear viscoplastic behavior by varying the effective viscosity of till we produced four reconstructions for the ice sheet during the last glacial maximum 18 14c ka and two reconstructions each of the ice sheet at 14 13 12 11 and 10 14c ka we also produced one reconstruction for 9 8 4 8 and 7 14c ka reconstructions that assume a low effective viscosity for all areas of deforming sediment show a multidomed ice sheet with a large bowl shaped depression over hudson bay and thin ice 1000 m above modern sea level over the western and southern margins those reconstructions that assume a higher effective viscosity of till in the hudson bay region than for the western and southern margins also show a multidomed ice sheet but with considerably thicker ice over hudson bay and a more northerly position of the central ice divide these two different geometries may represent ice sheet orographic changes associated with a heinrich event further increases in effective viscosity of till approaching the effective viscosity of ice would result in a high monolithic ice dome centered over hudson bay reinforcing the notion that a multidomed ice sheet reflects the distribution of substrate geology modeled ice surface geometry at the last glacial maximum shows many of the same general features as previous reconstructions that incorporate deformable beds our reconstructions with higher effective till viscosities in hudson bay also agree with the ice 4g reconstructions peltier 1994 which are based on inversion of relative sea level data for the early part of the last deglaciation 18 13 14c ka but then depart significantly from ice 4g beginning at about 12 14c ka due to differing assumptions of the history of deglaciation modeled ice volume for the last glacial maximum suggests a glacioeustatic change of 50 55 m by a soft bedded laurentide ice sheet this would increase as the effective viscosity of till increases subsequent ice volume changes through the last deglaciation generally parallel the trend of eustatic rise recorded at barbados new guinea and tahiti but suggest that the laurentide ice sheet was not the source of meltwater pulse 1a

the tintah campbell gap and implications for glacial lake agassiz drainage during the younger dryas cold interval abstract reconstructions of glacial lake agassiz paleogeography and drainage have been an important contribution to formulating a hypothesis in which glacial lake agassiz drainage to the atlantic ocean initiated the younger dryas cold interval this study evaluates the lake level and outlet history of lake agassiz as recorded by strandlines visible on lidar digital elevation models from north dakota and minnesota the former lake levels are warped due to glacial isostatic adjustment older levels have experienced more uplift and therefore have more curvature the strandline data establish that the moorhead lowstand of lake agassiz was bracketed by the strongly diverging campbell and tintah lake levels which creates a vertical gap between the former lake levels this gap exists due to a lake level drop of 90 m when the laurentide ice sheet retreat opened a lower outlet which must have been a northwest outlet to the arctic ocean by applying an exponential decay rebound model this event dates to 12 180 480 cal yr bp post dating the beginning of the younger dryas at 12 900 cal yr bp eastern drainage outlets to the atlantic ocean through the laurentian great lakes that were contemporaneous with the onset of the younger dryas cannot be ruled out but if these outlets existed their duration of occupation was short lived and not characterized by significant drawdown events within glacial lake agassiz

chronology of glacial lake agassiz meltwater routed to the gulf of mexico abstract sediment cores with new radiocarbon dates from the southern outlet of glacial lake agassiz indicate that meltwater delivery to the mississippi valley was disrupted at 10 800 14 c yr b p and the outlet was abandoned by 9400 14 c yr b p these findings confirm the timing of generally accepted terminations of the lockhart and emerson phases of lake agassiz additionally the radiocarbon chronology indicates that the spillway was fully formed by 10 800 14 c yr b p and that the occupancy in late emerson time was likely short lived with minimal spillway erosion

provenance of freshwater pulses in the gulf of mexico during the last deglaciation during the last deglaciation the decaying laurentide ice sheet lis delivered huge volumes of meltwater toward the gulf of mexico the present investigation of clay mineralogy and grain size characteristics of terrigenous sediments deposited in the orca basin gulf of mexico offers a unique opportunity to link the marine record of these meltwater floods with the reconstructed continental glacial history and the modeled drainage patterns five peculiar sedimentary levels characterized by high smectite content and low caco3 content were identified and occurred simultaneously with major meltwater floods according to recently published clay mineral distribution maps for north america these results help to pinpoint the southwestern margin of the lis as a main contributor to most of the meltwater discharges in addition the peculiar mineralogical composition illite and chlorite rich of the sediments characterizing the meltwater episode associated with heinrich event 1 suggests a provenance from the great lakes area supporting the interpretation of destabilization of the lis southeastern margin during this event decreased terrigenous contribution associated with changing provenance of sediments after 12 9 cal ka bp suggests strong modifications of the continental hydrography in relation to lake agassiz history and changes in the morphology of mississippi delta due to rising sea level

northwest outlet channels of lake agassiz isostatic tilting and a migrating continental drainage divide saskatchewan canada lake cores obtained from the northwest outlet of glacial lake agassiz in northwest saskatchewan canada provide a minimum date for the cessation of the flood from the northwest outlet and a chronology for abandonment of mid holocene channels that presently straddle the mackenzie and churchill drainage divide the stratigraphy of a vibracore taken from long lake consists of a lower pebble gravel fining to massive sand silty clay and then fibrous peat wood fragments from the base of the clay yielded an accelerator mass spectrometry ams date of 9120 bp because the lake is scour in origin and is in the head of the spillway the date is considered to be a minimum estimate for cessation of the flood from the northwest outlet at the beginning of the emerson phase a vibracore taken at haas lake in an abandoned channel surrounded by muskeg with no influent streams consists of 0 8 m of stratified pebble gravel containing abundant shell and wood fragments overlain by 1 62 m of gyttja with a sharp conformable lower contact ams dates range from 5590 bp from the topmost gravel to 3080 bp within the gyttja the gravel is interpreted as fluvial recording a river draining wasekamio lake north into the clearwater river across the present day drainage divide today a drop of 2 m occurs from wasekamio lake southeast to lac ile a la crosse along 150 km of lake basins parallel to the cree lake moraine the dates from haas lake suggest that before 5200 bp the drainage divide was about 100 km further southeast implying that during the emerson phase lake level was controlled by a sill near flatstone lake at about 430 m instead of between wasekamio lake and the clearwater river as was previously proposed holocene differential isostatic uplift caused the flow reversal in the upper churchill basin anastomosed channels at the mouth of rivers flowing north into lakes indicate that uplift is still active in the area today

geophysical investigation of a large landslide in glaciolacustrine clays in the trieves area french alps abstract slope movements in clay deposits are spread all over the world and result from complex deformation processes including internal strains in the landslide body and slipping along rupture surfaces such mass movements are likely to generate changes in the geophysical parameters characterizing the ground which can be used to map the landslide body in the last decade geophysical techniques have been increasingly used for landslide investigation purposes however the success of any geophysical technique is overall controlled by the existence of a geophysical contrast differentiating the body to be mapped for landslides affecting thick clay materials from soft clay to shale or marl electrical and seismic techniques have been mainly applied in the past in this study we attempt to physically characterize the deformation within a large slide avignonet affecting laminated clays which were deposited in a glacially dammed lake during the wurm period clay deposits which cover an area of 300 km2 south of grenoble french alps and have a maximum thickness of 200 m overlay compact alluvial layers and marly limestone of mesozoic age piezometric data at avignonet show that the water table is very shallow implying that the slide developed in saturated clay several seismic and electrical profiles were performed in order to tentatively correlate the variations of p wave vp velocity s wave velocity vs and electrical resistivity with geotechnical data and morphological observations in such saturated and fine material it turned out that only the s wave velocity exhibits significant variations with the displacement rates and the morphological features vs values at shallow depth were found to be inversely correlated with displacement rates measured by gps with a division by at least a factor of 2 between the zones unaffected and strongly deformed by the landslide these results suggest that vs mapping could provide valuable information on the deformation state of the clay material and that the evolution of vs with time could be used as an indicator for characterizing the landslide activity in the subsurface including the evolution into a flow

glacial lake agassiz its northwest maximum extent and outlet in saskatchewan emerson phase abstract six different lines of evidence support the hypothesis that glacial lake agassiz expanded an additional 70 000 km2 over that previously mapped in northwestern saskatchewan and that the lake discharged out the northwestern clearwater outlet then through glacial lake mcconnell and mackenzie river to the arctic ocean elevations of formerly unmapped 1 strandlines and 2 glaciolacustrine sediments between the previously mapped northwest limit of lake agassiz and the clearwater lower athabasca spillway indicate that water extended 170 km farther northwest recently mapped strandlines at elevations up to 60 m above the previously mapped extent of lake agassiz can be traced along 3 isobases to the mouth of the spillway based upon 4 six radiocarbon dates recovered from spillway flood deposits in the athabasca river valley and its late pleistocene delta the 5 clearwater spillway was cut at 9 9 ka bp this date is synchronous with the initiation of the emerson phase 9 9 ka bp in the southern lake agassiz basin and 6 coincides with the position of the laurentide ice sheet at the cree lake moraine 10 ka bp along the northern margin of the lake following closure of the eastern outlets at the onset of the emerson phase lake agassiz transgressed toward the northwest into the deglaciated and isostatically depressed glacial foreland in the churchill river valley to an elevation of 490 m the pre flood elevation of the churchill mackenzie drainage divide at the head of the clearwater lower athabasca spillway the beaver river moraine an earthen drainage divide was breached resulting in lowering lake agassiz 52 m to a stable elevation at 438 m the lake discharged 21 000 km3 of water into the arctic ocean that raised global sea level by 6 cm

bison remains from a lake agassiz spit complex in the swan river valley manitoba depositional environment and paleoecological implications fossil bison remains have been recovered from gravels on an extensive spit complex situated between the upper and lower campbell levels of lake agassiz in swan river valley western manitoba three bone samples yielded radiocarbon dates of 10 300 200 years bp bgs 617 9500 150 years bp bgs 840 and 9400 125 years bp bgs 887 these are the first dates obtained outside the southern basins of lake agassiz for the beginning of the campbell phase local geomorphological evidence and the radiocarbon dates indicate that both campbell beaches formed within a relatively short time during the campbell phase aside from their geological significance the bison remains and their depositional context are important for interpreting early holocene ecology and paleo indian occupation of the swan river valley

the determination of statistical and deterministic hydrological landslide triggering thresholds hydrological landslide triggering thresholds separate combinations of daily and antecedent rainfall or of rainfall intensity and duration that triggered landslides from those that failed to trigger landslides they are required for the development of landslide early warning systems when a large data set on rainfall and landslide occurrence is available hydrological triggering thresholds are determined in a statistical way when the data on landslide occurrence is limited deterministic models have to be used for shallow landslides directly triggered by percolating rainfall triggering thresholds can be established by means of one dimensional hydrological models linked to the infinite slope model in the case of relatively deep landslides located in topographic hollows and triggered by a slow accumulation of water at the soil bedrock contact simple correlations between landslide occurrence and rainfall can no longer be established therefore real time failure probabilities have to be determined using hydrological catchment models in combination with the infinite slope model

use of sentinel 2 images for the detection of precursory motions before landslide failures abstract the sentinel 2 optical satellites provide a global coverage of land surfaces with a 5 day revisit time at the equator we investigate the ability of these freely available optical images to detect precursory motions before rapid landslides a 9 month time series of displacement is derived from sentinel 2 data over a major landslide in the french alps which exhibited a sudden reactivation in june 2016 this analysis reveals a 7 month period of low activity 1 m followed by a sudden acceleration of 3 2 1 2 m in 3 days before the failure of a mass of about 2 to 3 6 106 m3 the location of this precursory motion is consistent with that of the slow motions occurring since 2001 about 1 m year as revealed by aerial photographs and lidar analysis this change in activity over a very short period of time days emphasizes the value of the frequent revisit time of sentinel 2 despite its medium resolution of 10 m we finally simulate the ability of sentinel 2 for detecting these precursory patterns before a rapid landslide occurs based on typical voight s laws for creeping materials characterized by a power law exponent based on this analysis and on global cloud cover maps we compute the probability to detect pre failure motions of landslides using the sentinel 2 constellation this probability is highly heterogeneous at the global scale affected by the revisit time of the satellite and the cloud cover however the main factors controlling this detection ability are the properties of the landslide itself its size and the parameter with almost 100 of detection probability for 1 3 and 0 for 1 8 despite all these limitations probability to detect a motion before a landslide failure often reaches 50 for classical landslide parameters these results open new perspectives for the early warning of large landslide motion from global and open source remote sensing data

evolution of soil wetting patterns preceding a hydrologically induced landslide inferred from electrical resistivity survey and point measurements of volumetric water content and pore water pressure 1 the hydrological state of a hillslope prior to a sprinkling induced shallow landslide was monitored using electrical resistivity tomography ert along a 47 m long transect supplemented by local time domain reflectometry tdr and tensiometer measurements the spatial and temporal evolution of wetting patterns in the soil material indicated attainment of a stationary fully saturated profile in a slope region underlain by shallow sandstone bedrock the significant decrease in spatially averaged standard deviation of water saturation has not been observed during an earlier failed attempt to trigger a landslide by intense sprinkling while for the stable experiment no landslide was triggered water saturation and soil moisture variability were still increasing with time the unstable experiment reached a time invariant state of high pore water pressures and saturations until it finally failed the results indicate that when large and interconnected regions of hillslope are saturated as confirmed by high volumetric water content and low standard deviation of water saturation additional water cannot be redistributed to empty drier regions and may eventually enhance local pore water pressure and seepage force initiating large shear deformation and failure accordingly a transition to such a critical steady state of high average water saturation associated with low and constant spatial standard deviation may serve as additional hydro geophysical indicator for the imminence of a landslide release

geophysical monitoring of moisture induced landslides a review author s whiteley js chambers je uhlemann s wilkinson pb kendall jm abstract 2018 the authors geophysical monitoring of landslides can provide insights into spatial and temporal variations of subsurface properties associated with slope failure recent improvements in equipment data analysis and field operations have led to a significant increase in the use of such techniques in monitoring geophysical methods complement intrusive approaches which sample only a very small proportion of the subsurface and walk over or remotely sensed data which principally provide information only at the ground surface in particular recent studies show that advances in geophysical instrumentation data processing modeling and interpretation in the context of landslide monitoring are significantly improving the characterization of hillslope hydrology and soil and rock hydrology and strength and their dynamics over time this review appraises the state of the art of geophysical monitoring as applied to moisture induced landslides here we focus on technical and practical uses of time lapse methods in geophysics applied to monitoring moisture induced landslide the case studies identified in this review show that several geophysical techniques are currently used in the monitoring of subsurface landslide processes these geophysical contributions to monitoring and predicting the evolution of landslide processes are currently underrealized hence the further integration of multiple parametric and geotechnically coupled geophysical monitoring systems has considerable potential the complementary nature of certain methods to map the distribution of subsurface moisture and elastic moduli will greatly increase the predictive and monitoring capacity of early warning systems in moisture induced landslide settings

hydrological triggering conditions of landslides in varved clays in the french alps abstract in this paper the meteorological and hydrological conditions are analyzed which trigger shallow and deeper landslides in glacio lacustrine deposits varved or laminated clays in the french alps the hydrological system of these landslides consists of a colluvial cover which supplies water into the fissures of the underlying varved clays from these fissures water can infiltrate more or less horizontally into the silt layers of the varved clays a combined reservoirs model was used to simulate the water fluctuations in the colluvial cover and the fissures both the water level in the fissures and the residence time of water in the fissures are mainly controlled by the amount of water storage in the colluvial cover simulations over the last 25 years show that almost each year the fissures are completely filled with water for several months a year infiltration experiments in the field show that infiltration into the varved clays occurs mainly by horizontal infiltration into the silt laminae calculated infiltration rates from these fissures into the silt layers show that the mean yearly residence time of water in the fissures is not sufficient to fully saturate the clay mass each year it is therefore concluded that the triggering of the landslide movements is mainly controlled by the development of positive pore water pressures in the fissure system and that the rise of pore water pressures induced by the matrix system of the varved clays only plays a minor role the calculations also show that drainage of the colluvial cover is a very efficient measure to stabilize the deeper landslides

chemical compositions of mussels and clams from the tangyin and yonaguni knoll iv hydrothermal fields in the southwestern okinawa trough abstract studies of the chemical characteristics of mussels and clams in seafloor hydrothermal fields are important for understanding mass fluxes and elemental partitioning from hydrothermal vents into the biosphere metal bioaccumulation of seafloor hydrothermal ecosystems and the sources and sinks of biogeochemical and fluid cycles we are the first to measure the mineral major trace and rare earth element and carbon and oxygen isotope compositions of mussels bathymodiolus platifrons and clams conchocele bisecta from the tangyin and yonaguni knoll iv hydrothermal fields in the southwestern okinawa trough mineralogical analysis shows that the carbonate shells of the mussel and clam samples are mainly composed of calcite and aragonite metal elements exhibit linear correlations in the shells e g v and u and tissues e g li and rb of the mussels and clams suggesting that not all positive correlations of elements in tissues are inherited by the shells v as ca sr and fe cr ratios in the mussels and clams are close to those in the seawater indicating that element ratios of seawater might be inherited by the mussels and clams in addition the fe cr ratio of the shells of both mussels and clams can be used to trace the local seawater composition the total lree concentrations of mussel and clam tissue samples are higher than those of the mussel and clam shell samples are similar to the hydrothermal fluids exhibit lree enrichment lacn ndcn ratios 1 86 32 1 and no or only slightly negative eu anomalies indicating that benthic animals are a sink of lrees from hydrothermal fluids and that the eu eu ratios of fluids change when fluids are incorporated into the tissues of the mussels and clams in addition the 13c values of mussel shell samples are heavier than those of the clam shell samples in the hydrothermal field indicating that more than one carbon source may be involved in defining the 13c compositions of the shells the majority of the 18o values of clam shell samples fall in the range of 18o values of the mussel shell samples and are close to the hydrothermal fluid 18oh2o values implying that the 18o values of mussel and clam shell carbonate is influenced by the hydrothermal environment magmatic water and fluid dilution with seawater

glacial lake agassiz the northwestern outlet and paleoflood valley morphology and sediment in the fort mcmurray region of alberta indicate that a catastrophic flood discharged down the lower clearwater and athabasca river valleys 9900 yr b p geomorphic and chronologic evidence suggests that glacial lake agassiz emerson phase was the probable water source as the flood incised a drainage divide located near the alberta saskatchewan border the level of glacial lake agassiz decreased by 46 m discharged 2 4 x 106 m3 s for at least 78 days and stabilized at 438 m above sea level in the lake wasekamio area at that time water entered the arctic ocean via glacial lake mcconnell and the mackenzie river rather than the gulf of mexico via the mississippi river as previously thought such a large influx of fresh water 8 6 km3 h into the arctic at the close of the last glaciation may have had an abrupt major influence on northern climate

morphology structure and kinematics of a rainfall controlled slow moving andean landslide peru the large slow moving landslide of maca is located in the upper colca valley southern peru a region characterized by a well pronounced rainy period and intense and recurrent sustained seismicity the landslide developed in deep lacustrine deposits has recently accelerated threatening the maca village this work aims at understanding the rupture mechanism and the causes of the recent landslide reactivation acceleration we present a multidisciplinary characterization of the maca landslide that includes i geological and morphological mapping in the field ii remote sensing analysis using an historical aerial photograph of 1955 and the pleiades satellite images 2013 iii global positioning system gps including time series of surveys over 13 years and continuous measurements over 14 months iv a geophysical campaign with deep electrical resistivity tomography profiles acquired across the landslide mass our study shows that this 60 mm3 landslide which can be classified as a clay silt compound landslide moved by 15 m between 2001 and 2014 with a large inter annual velocity variation up to a factor of 500 depending on the rainfall intensity we suggest that these dramatic changes in velocity are the result of the combination of a threshold mechanism and the short intense rainy season in peru this study reveals three main driving factors acting at different timescales i over several decades the river course has significantly changed causing the maca landslide reactivation in the 1980s due to the erosion of its toe ii at the year scale a minimum amount of rainfall is required to trigger the motion and this amount controls the landslide velocity iii transient changes in slide velocity may occur anytime due to earthquakes this study particularly highlights the non linear behaviour of the motion with rainfall copyright 2016 john wiley sons ltd

age determinations for glacial lake agassiz shorelines west of fargo north dakota usa understanding the evolution of lake agassiz is vital to developing a comprehensive late quaternary history of central north america although many of the geomorphic features of the lake are well known current reconstructions pri marily depend upon relative ages of landforms here we report new optically stimulated luminescence osl ages on a flight of strandlines located 140 km north of the southern outlet strandline ages at this location range from 14 3 0 2 to 10 0 0 2 ka cal spanning 4000 years of lake history using geomorphic relationships and osl age control it is pro posed that the herman through tintah strandlines developed over a period of 1000 years followed by a hiatus of strandline development until the campbell strandline developed at 10 3 0 2 ka cal there is agreement between our new osl dates and osl and radiocarbon ages from geomorphically correlative landforms elsewhere in the lake basin the use of high reso lution lidar imagery greatly aids localized mapping of shoreline features additional site specific field work and osl ages are necessary to further evaluate strandline tracing across the basin resume il est essentiel de comprendre l evolution du lac agassiz pour avoir un historique complet du quaternaire tardif du centre de l amerique du nord bien que plusieurs des caracteristiques geomorphologiques du lac soient bien connues les reconstructions actuelles sont surtout determinees par l ge relatif des formes de terrain dans cet article nous donnons de nouveaux ges determines par luminescence stimulee optiquement osl a d anciennes lignes de plage situees a 140 km au nord de l exutoire sud les ges des anciennes lignes de plage a cet endroit varient entre 14 3 0 2 et 10 0 0 2 ka cal soit 4000 ans d histoire du lac base sur des relations geomorphologiques et le controle de l ge par osl il est propose que les anciennes lignes de plage herman a tintah se soient developpees durant une periode de moins de 1000 ans une periode sans developpement de lignes de plage aurait suivi jusqu au developpement de la ligne de plage campbell vers 10 3 0 2 ka cal il y a concordance entre nos nouvelles dates osl et les ges determines par osl et par radiocar bone sur des formes de terrain correlees par geomorphologie ailleurs dans le bassin du lac l utilisation d imagerie lidar a haute resolution a grandement aide la cartographie locale des caracteristiques des lignes de rivage d autres travaux speci fiques au site et d autres ges osl sont necessaires pour continuer a tracer les anciennes lignes de plage a travers le bassin traduit par la redaction

rapid least squares inversion of apparent resistivity pseudosections by a quasi newton method1 a fast inversion technique for the interpretation of data from resistivity tomography surveys has been developed for operation on a microcomputer this technique is based on the smoothness constrained least squares method and it produces a two dimensional subsurface model from the apparent resistivity pseudosection in the first iteration a homogeneous earth model is used as the starting model for which the apparent resistivity partial derivative values can be calculated analytically for subsequent iterations a quasi newton method is used to estimate the partial derivatives which reduces the computer time and memory space required by about eight and twelve times respectively compared to the conventional least squares method tests with a variety of computer models and data from field surveys show that this technique is insensitive to random noise and converges rapidly this technique takes about one minute to invert a single data set on an 80486dx microcomputer

process identification at a slow moving landslide in the vorarlberg alps a fine grained slope that exhibits slow movement rates was investigated to understand how geohydrological processes contribute to a consecutive development of mass movements in the vorarlberg alps austria for that purpose intensive hydrometeorological hydrogeological and geotechnical observations as well as surveying of surface movement rates were conducted during 1998 2001 subsurface water dynamics at the creeping slope turned out to be dominated by a three dimensional pressure system the pressure reaction is triggered by fast infiltration of surface water and subsequent lateral water flow in the south western part of the hillslope the related pressure signal was shown to propagate further downhill causing fast reactions of the piezometric head at 5 5 m depth on a daily time scale the observed pressure reactions might belong to a temporary hillslope water body that extends further downhill the related buoyancy forces could be one of the driving forces for the mass movement a physically based hydrological model was adopted to model simultaneously surface and subsurface water dynamics including evapotranspiration and runoff production it was possible to reproduce surface runoff and observed pressure reactions in principle however as soil hydraulic functions were only estimated on pedotransfer functions a quantitative comparison between observed and simulated subsurface dynamics is not feasible nevertheless the results suggest that it is possible to reconstruct important spatial structures based on sparse observations in the field which allow reasonable simulations with a physically based hydrological model copyright 2004 john wiley sons ltd

postglacial history and paleoecology of wampum manitoba a former lagoon in the lake agassiz basin a small paleolagoon along the margin of the glacial lake agassiz basin near wampum manitoba 130 km southeast of winnipeg contains an unusually thick and continuous sequence of late glacial and holocene organic sediment cores at 17 sites through this sequence provide insight into the fluctuations of the level of lake agassiz the timing of the construction of the lake9s most extensive strandline the upper campbell beach and the paleoecology of this area during the past 10 000 14 c yr the history of this area is established from 26 new ams radiocarbon dates siliceous microfossils plant macrofossils mineralogy sediment characteristics and stratigraphic relationships following deglaciation at wampum about 11 14 c ka deposition of largely unfossiliferous silty clay with occasional ice rafted clasts represents relatively deep water conditions in lake agassiz overlying this is a spatially and temporally variable mixture of silt sand peat gyttja and marl containing an allochthonous assemblage of siliceous microfossils and plant macrofossils with a wide range of radiocarbon dates these sediments were deposited in an embayment of lake agassiz mainly in shallow quiet waters as the lake transgressed about 10 ka over the moorhead low water phase surface between about 9 7 and 9 3 ka the wampum embayment was progressively isolated from lake agassiz by growth of the upper campbell spit resulting in the formation of a lagoon organic rich deposits on the lakeward side of the lagoon were buried 9 3 9 4 ka by sand and gravel of the spit and a thin overwash of sand marks this event throughout the lagoon at about this time lake agassiz fell below the upper campbell beach level subsequent accumulation at wampum consists mainly of algal gyttja during the early holocene and marl during the middle holocene only minor fluctuations in hydrological conditions occurred except for slightly warmer and drier conditions between 6 2 and 4 0 14 c ka these stable shallow water conditions may be due partly to persistent groundwater contributions to the site progressive encroachment of rooted aquatics led to present day fen conditions peat accumulation across the basin began by about 4 0 ka

influence of landslide geometry and kinematic deformation to describe the liquefaction of landslides some theoretical considerations abstract the generation of excess pore pressure and possible liquefaction can be explained by different mechanisms in literature less attention is given to the effects of landslide geometry and kinematic deformation on the generation of excess pore pressure and possible liquefaction of sliding blocks the objective of this paper is to discuss these factors by proposing a simple analytical model of landslide liquefaction using classic soil mechanics theory the model describes the initial state of failure and solves forces for each slice with the bishop s limit equilibrium method immediately after failure the difference in movement for each slice is calculated assuming a viscous shear band and using the coulomb viscous model the differential movements conduct to differential strains which are transferred to excess pore pressures in slides characterized by curved slip surfaces the lower parts showed compaction and increase in pore pressures during displacement while the upper parts showed dilatation and a decrease in pore pressures the potential liquefaction is then evaluated for each slice in relation to the displacement the model is applied to a slump type failure that occurred on the super sauze mudslide southeast france in compact clay rich material it was observed that the slump completely liquefied into a flow however the model simulations were not able to completely liquefy all the slices of the slump in case a decrease in pore pressures through dilatation was assumed in the upper part of the slump the decrease in pore pressures caused a rapid stabilisation of the remaining sliding body in case a neutral pore pressure was assumed in the upper part with dilatation movement and deformation of the remaining slices could continue leading to a nearly complete liquefaction of the slump model simulations for many geometries of curved slip surfaces reveal that the liquefied volume increases with steeper slopes and more curved slip surfaces it is discussed also how planar slides which in theory show small differential movement of the individual slices and hence no large compaction can completely liquefy through deformation at the toe

using lidar digital elevation model data to map lake agassiz beaches measure their isostatically induced gradients and estimate their ages abstract high resolution lidar digital elevation model dem data were used to create dem mosaics and hillshade maps of a large region in north dakota for better defining and measuring the strandlines of glacial lake agassiz although many of the strandlines in this region had been identified and named more than a century ago by warren upham lidar images clearly reveal their complexity and identify additional small and low relief ridges not previously mapped the elevations of the crests of six well developed strandlines the campbell mccauleyville lower blanchard emerado upper ojata and lower ojata beaches were measured for each of these strandlines north south gradients were calculated which were produced by differential isostatic rebound the steepest gradient is on the uppermost campbell beach in the sequence and the gradient on each beach below is progressively lower confirming that these beaches were deposited in sequence from oldest to youngest as the level of lake agassiz declined because there were no anomalous beach gradients in this sequence the ojata beach formed after 9400 14 c 10 630 cal bp which is when the higher elevation campbell beach was deposited rather than at 10 000 14 c 11 480 cal years ago as some have suggested because of the age of organics below the ojata beach those organics and the subaerial surface on which they lie survived the moorhead transgression to the campbell beach and the ojata beach must have been deposited over the older organic unit later as lake level regressed a simple extrapolation model was used to estimate the ages of beaches in the sequence

landslide monitoring using seismic refraction tomography the importance of incorporating topographic variations abstract seismic refraction tomography provides images of the elastic properties of subsurface materials in landslide settings seismic velocities are sensitive to changes in moisture content which is a triggering factor in the initiation of many landslides however the application of the method to long term monitoring of landslides is rarely used given the challenges in undertaking repeat surveys and in handling and minimizing the errors arising from processing time lapse surveys this work presents a simple method and workflow for producing a reliable time series of inverted seismic velocity models this method is tested using data acquired during a recent novel long term seismic refraction monitoring campaign at an active landslide in the uk potential sources of error include those arising from inaccurate and inconsistent determination of first arrival times inaccurate receiver positioning and selection of inappropriate inversion starting models at our site a comparative analysis of variations in seismic velocity to real world variations in topography over time shows that topographic error alone can account for changes in seismic velocity of greater than 10 in a significant proportion 23 of the data acquired the seismic velocity variations arising from real material property changes at the near surface of the landslide linked to other sources of environmental data are demonstrated to be of a similar magnitude over the monitoring period we observe subtle variations in the bulk seismic velocity of the sliding layer that are demonstrably related to variations in moisture content this highlights the need to incorporate accurate topographic information for each time step in the monitoring time series the goal of the proposed workflow is to minimize the sources of potential errors and to preserve the changes observed by real variations in the subsurface following the workflow produces spatially comparable time lapse velocity cross sections formulated from disparate discretely acquired datasets these practical steps aim to aid the use of the seismic refraction tomography method for the long term monitoring of landslides prone to hydrological destabilization

mineral magnetism and geomagnetic secular variation of marine and lacustrine sediments from central italy timing and nature of local and regional holocene environmental change abstract sediment core palaeomagnetic and mineral magnetic records from two crater lakes in central italy and from the western margin of the adriatic sea have been used to evaluate local and regional responses to holocene environmental change in all cores sediment magnetism reflects the interplay between catchment material and the in situ production of bacterial magnetite magnetotactic bacteria in the lakes the earliest holocene sediments record a waning catchment input that we attribute to rising lake levels and increased tree cover in the catchment from 9000 to 5000 yr bp both lakes become anoxic a consequence of water mass stratification driven by high lake levels bottom water anoxia also developed in the adriatic with sapropel s1 produced between 9000 and 7000 yr bp subsequently the lake and adriatic mineral magnetic records show evidence for increased catchment delivery consistent with pollen evidence for bronze age deforestation in the lakes this evidence is first recorded at 4300 yr bp and a number of distinct clearance events are recorded in comparison at adriatic site rf93 30 lithogenic input increases abruptly at 3500 yr bp and is followed by a slowly changing record of waxing and waning sediment delivery inter site comparisons of palaeomagnetic data point to a possible link between the magnitude of the bacterial magnetite component and the recorded magnetic inclination the sites are at near identical latitudes and have similar sediment accumulation rates but the adriatic sites have a core average magnetic inclination that is some 10 steeper than the lake average values we suggest that the large dipole moment of the magnetosome chains which in life produce the passive alignment of the bacterium along the local geomagnetic field line produce a more faithful albeit smoothed record of the geomagnetic field

problems in predicting the mobility of slow moving landslides abstract this paper discusses problems in predicting the mobility of slow moving landslides three case studies are presented here where research has been carried out by the utrecht university the la valette landslide complex in the french alps the la mure landslide in the french pre alps near grenoble and the hau landslide in switzerland to predict field velocities of these slow moving landslides the viscosity parameters of the material of these landslides were determined by strain controlled tests in a ring shear apparatus based on bishop s design at utrecht university the viscosity parameters from the laboratory proved to be 10 to 1000 times lower than viscosities obtained from back analyses on the observed velocities in the field this discrepancy may be explained by the development of negative pore pressures when the plastic material slides over a rigid wavy slip surface and or by convergent flow effects the associated gain in strength results in a higher apparent viscosity a more detailed analysis is made for the movements of the la valette landslide observed velocities at the la valette landslide are difficult to describe by one parameter set as the response to a change in groundwater level is not the same during a rise or fall in the piezometric level this deviation may be explained by rapid changes in total stresses and consequently changes in pore pressure under partly undrained conditions the emerging hysteresis with local and temporal variations in pore pressure makes it difficult to predict in detail the moving pattern of landslides

electrical resistivity tomography technique for landslide investigation a review abstract in the context of in situ geophysical methods the electrical resistivity tomography ert is widely used for the near surface exploration of landslide areas characterized by a complex geological setting over the last decade the technological improvements in field data acquisition systems and the development of novel algorithms for tomographic inversion have made this technique more suitable for studying landslide areas with a particular attention to the rotational translational and earth flow slides this paper aims to present a review of the main results obtained by applying ert for the investigation of a wide spectrum of landslide phenomena which affected various geological formations and occurred in different geographic areas in particular significant and representative results obtained by applying 2d and 3d ert are analyzed highlighting the advantages and drawbacks of this geophysical technique finally recent applications of the time lapse ert tl ert for landslide investigation and the future scientific challenges to be faced are presented and discussed

application of geophysical measurements for assessing the role of fissures in water infiltration within a clay landslide trieves area french alps rainfall and its consequences are usually considered as the major factor triggering slope instabilities within clay deposits the link between rainfall water infiltration and landslide activity may be complex and comprehensive sets of data are still necessary to understand how water infiltrates in cohesive material on unstable slopes made of fine grained sediments gravitational deformation generates superficial shear ruptures and tension fissures whose continuous opening could be amplified by shrinkage during dry periods this fissure network at the surface can be very dense and strongly controls the water infiltration process however it remains difficult to assess the fissure evolution at depth and its eventual relationship with shallow slip surfaces this work presents the results of a geophysical study which aimed to characterize the fissures that are observed along the unstable clay slopes of the trieves area french alps the site was first investigated combining geomorphological analysis drilling borehole logging geotechnical tests and geophysical experiments this investigation evidenced the presence of at least three rupture surfaces at 5 10 15 and 42 m with a water flow at the second one in a second step permanent instruments were installed piezometers and soil water content probes results indicate high water infiltration velocities down to the water table located at 2 5 m depth that are likely to be linked with sub vertical preferential paths such as fissures geophysical parameters electrical resistivity s wave velocities and rayleigh waves attenuation were monitored geophysical results suggest that fissures are permanently open that they serve as preferential infiltration paths and that they can reach at least a depth of 2 m the methods employed in this research put forward that the system of imbricated fissures drains water from the surface down to the shallow slip surfaces at 5 and 10 15 m this work highlights the role of fissures network in water infiltration in the numerous clay landslides of the trieves area copyright 2011 john wiley sons ltd

glacial lake agassiz a 5000 yr history of change and its relationship to the δ18o record of greenland lake agassiz was the largest lake in north america during the last period of deglaciation the lake extended over a total of 1 5 10 6 km 2 before it drained at ca 7 7 14 c ka 8 4 cal calendar ka new computer reconstructions controlled by beaches isostatic rebound data the margin of the laurentide ice sheet outlet elevations and a digital elevation model dem of modern topographic data show how variable the size and depth of this lake were during its 4000 14 c yr 5000 cal yr history abrupt reductions in lake level ranging from 8 to 110 m occurred on at least 18 occasions when new outlets were opened reducing the extent of the lake and sending large outbursts of water to the oceans three of the largest outbursts correlate closely in time with the start of large 18 o excursions in the isotopic records of the greenland ice cap suggesting that those freshwaters may have had an impact on thermohaline circulation and in turn on climate

testing northwest drainage from lake agassiz using extant ice margin and strandline data extant data on shorelines and ice margins in the glacial lake agassiz basin defines the limits of lake agassiz through deglacial time the ice sheet margin had not retreated far enough northwards by the beginning or end of the younger dryas chronozone for the lake to drain northwest however once lake agassiz reached the campbell beach stage at 10 800 10 300 cal bp then projections of lake agassiz strandlines were higher than the topography allowing for the first possible pathway to the northwest this relationship is used to reject the recent assertion that there was northwest drainage from lake agassiz at the beginning and end of the younger dryas chronozone

slope monitoring an application of time lapse electrical resistivity imaging method in bukit antarabangsa kuala lumpur slope monitoring study using 2 d electrical resistivity imaging method was conducted on a slope where a massive landslide occurred in december 2008 in bukit antarabangsa kuala lumpur malaysia the main objective of the study is to determine the subsurface resistivity distribution of the study area and to map the risk potential zone of landslide in the future to detect the changes in the subsurface resistivity distribution due to variation in water saturation in the subsurface time lapse electrical resistivity imaging method was applied in this study repeated measurements of electrical resistivity over chosen lines at different times were done to monitor the changes in the subsurface resistivity distribution the results obtained from the time lapse electrical resistivity shows that there are significant changes in the subsurface resistivity distribution during different periods locations of possible slope failure are identified along the slope and are divided into zone 1 and zone 2 weak zones are characterized by the large proportion of high water saturation zones and low resistivity values which are highly affected by the supply of water into the subsurface as well as the properties of the subsurface materials these particular regions are more susceptible towards slope failure as high water content will ease the movement of soil in the subsurface thus proper mitigation must be done at the problematic zones to prevent the occurrence of slope failure in the future

strandline analysis in the southern basin of glacial lake agassiz minnesota and north and south dakota usa glacial lake agassiz a large pleistocene lake left behind strandlines at multiple elevations within its basin prior researchers have used these strandlines to identify four relatively stable water level stages but tracing them over long distances is often problematic in this study the elevation of the tintah strandline is returned to its original designation and a newly interpreted stable lake level at 1020 1030 ft 311 314 m is referred to as the upham level based on a concentration of ridges and a spit at that elevation cores from strandline and lagoon complexes from the milnor to tintah beaches reveal a decreasing thickness of strandline sediment associated with shorter aggregate length strandlines this relationship is most likely controlled by sediment starvation greater water level fluctuations and shallower water beaches near the head of the southern outlet spillway indicate that shoreline occupation at the lower campbell level was either very short lived or strandline development was hampered by shallow water the modern day sill elevation between the southern outlet spillway and the lake basin is found to be 3 km south of white rock minnesota at an elevation of 974 ft 297 m all but the campbell strandlines at the southern outlet are interpreted as the result of a regression driven by incision of the southern outlet spillway

reconstructed topography of southern new england prior to isostatic rebound with implications of total isostatic depression and relative sea level abstract topographic models of the late quaternary landscape prior to isostatic rebound aid interpretation of glacial lake water levels and geomorphic features as well as ice thickness mantle viscosity and lithospheric strength the well established limit of glacial marine inundation in central and northern new england provides a test of total isostatic depression relative sea levels reflecting differing magnitudes of isostatic rebound show that published values of isostatic depression in southern new england would inundate the landscape in southern new england with marine water south of the limit of late pleistocene marine inundation this suggests that isostatic depression at the terminal margin of the laurentide ice sheet lis was 50 m a first order estimate of ice thickness based on total isostatic depression and the observed uplift profile in southern new england supports the thin ice models in new england ice thickness ranged from 100 m at the southeastern margin of the lis to 1000 m at a point 300 km north of the terminal margin this regional model places constraints on continental ice sheet and geophysical models that should be considered in the future

deglaciation ages and meltwater routing in the fort mcmurray region northeastern alberta and northwestern saskatchewan canada a field based reconstruction of the deglacial paleogeography in the fort mcmurray area permits 1 constraining the timing of meltwater routing to the arctic from the present hudson bay drainage basin and 2 minimum age estimates for ice margin positions that can be used to constrain ice sheet modeling results a downslope recession of the laurentide ice sheet resulted in a series of proglacial lakes forming between the ice margin and higher land to the southwest the paleogeography of these lakes is poorly constrained in part from the masking effect of boreal forest vegetation and map scale issues however recent space shuttle based dems increase the number and spatial extent of moraines identified within the study area resulting in a coherent pattern of ice margin retreat focused on the athabasca river valley an intensive lake coring program resulted in a minimum ten fold increase in the radiocarbon database used to limit moraine ages results indicate that deglaciation in this region was younger than previously reported and it is likely that the meltwater could not drain northward to the arctic ocean from any source southeast of the fort mcmurray area until approximately 9850 9660 14 cbp

multiple meltwater discharge and ice rafting events recorded in the deglacial sediments along the beaufort margin arctic ocean abstract the first regional model for the deglacial history of the beaufort margin slope in the western arctic is presented the conceptual model was developed using new high resolution chirp seismic reflection multibeam bathymetry and sediment core data acquired along the margin this synthesis provides important constraints on sediment source and dispersal patterns for the last deglaciation the continental slope from barrow canyon to the mackenzie trough is characterized by thick holocene sediments mostly sourced from barrow canyon and continental discharge this acoustically transparent fine grained unit overlies acoustically laminated sediments sourced from the mackenzie river and ice rafting the deglacial history of the margin from mackenzie trough to the amundsen gulf is characterized by many ice rafting and meltwater discharge events ice rafted debris layers were deposited around 14 6 ka and 14 1 ka and likely document enhanced ice shedding events from the amundsen and m clure ice streams as they retreated there are three inferred meltwater discharge events all sourced from the mackenzie region the oldest discharge event had two phases one sometime between 14 5 ka and 14 2 ka and another between 14 0 ka and 13 0 ka this discharge deposited finely laminated sediments more than 7 m thick sourced from proglacial lakes in the area following this was a flood event starting at 12 94 ka which generated high amplitude reflectors deposited coarse debris and caused a lowering in the 18o record this is possibly a major outburst flood from glacial lake agassiz with an additional component of agassiz meltwater that was diverted from its southern drainage pathway down the mississippi to the gulf of mexico finally a third discharge event was initiated by 11 3 ka which deposited coarse laminated sediments focused in the mackenzie trough timing of these second and third events correlates with the onset of the younger dryas cold period and the preboreal oscillation event respectively suggesting that fresh water discharge may have reached a tipping point leading to those climate events

detecting infiltration of water through soil cracks by time domain reflectometry abstract during an experiment where simulated rainfall was applied to cracked soil time domain reflectometry tdr was used to measure the water content of cracks and adjacent soil vs water content at some distance from the cracks at a depth of 10 to 30 cm the rate of wetting of soil immediately adjacent to the cracks was more rapid than thatof the soil at some distance from the cracks independent predictions of when water should begin flowing down the cracks were deduced from knowledge of the applied rainfall rate field measured hydraulic conductivity initial water content and bulk density these predictions checked well with those tdr measurements which indicated when water began to accumulate in and adjacent to the cracks in a clay soil under corn and soybeans more than 1 cm of rainfall at rates greater than 0 1 cm h contributed water to the soil cracks the water content profiles showed the very limited depth of wetting in the soil at some distance away from the cracks as opposed to the much greater depth of wetting within and adjacent to the cracks

geotechnical problems caused by glaciolacustrine clays in the french alps abstract after more than 10 years of observations and monitoring of several landslides in glaciolacustrine clays in the french alps the authors give an account of the physical and mechanical characteristics of these formations the physical and geomechanical properties of the clays are analysed in relation to the main types of instability observed on the natural slopes of the area studied the low plasticity indexes of these clays explain the rapid transformation of the clays into a liquid state leading to innummerable surface flows the clays show a strong anisotropy at peak strength conditions that disappears at residual strength c o o 16 18 natural slopes become unstable if the gradient exceeds 8 10 these types of movement can be distinguished at three different depths 0 5 m 5 10 m and greater than 10 m the displacement rates vary from 1 cm yr for the deep seated slides to as much as 1 m yr for the surficial slides displacement rates in these slides are limited by the viscous properties of the laminated clays however extreme rainfall may cause catastrophic failure in conclusion some recommendations are given from an engineering point of view

tracer test to assess flow and transport parameters of an earth slide the montecagno landslide case study italy abstract subsurface water processes are principle triggering and driving factors during slope movements however the hydraulic properties that drive groundwater flow along the slope remain poorly understood moreover landslide deposits are often characterized by layering and fissures that cause high heterogeneity in the distribution of hydraulic properties this heterogeneity leads to great uncertainty in the prediction of groundwater flow paths this study aimed to improve understanding of hydraulic and transport properties of deep earth slides and to identify preferential flow directions inside the landslide body a dye tracer test was used to estimate transport parameters and characterize groundwater flow paths the results indicate that in the studied landslide two groundwater flow types exist and are related to the presence of fissured rock blocks and debris horizons embedded in a fine matrix the estimated low groundwater flow velocity has rarely been estimated in other studies of this landslide type the groundwater flow direction appears to be mainly influenced by the failure surface shape and differs from the sliding direction our results differ from those in other landslide studies and improve our knowledge of groundwater flow properties in deep earth slides furthermore they offer a new contribution to slope stability analyses and formula and to the effective design of mitigation strategies

large scale infiltration experiments into unsaturated stratified loess sediments monitoring and modeling summary two large scale field experiments were conducted to track water flow through unsaturated stratified loess deposits in the experiments a trench was flooded with water and water infiltration was allowed until full saturation of the sediment column to a depth of 20 m was achieved the water penetrated through a sequence of alternating silty sand and sandy clay loess deposits the changes in water content over time were monitored at 28 points beneath the trench using time domain reflectometry tdr probes placed in four boreholes detailed records were obtained from a 21 day period of wetting followed by a 3 month period of drying and finally followed by a second 14 day period of re wetting these processes were simulated using a two dimensional numerical code that solves the flow equation the model was calibrated using pest the simulations demonstrate that the propagation of the wetting front is hampered due to alternating silty sand and sandy clay loess layers moreover wetting front propagation is further hampered by the extremely low values of the initial unsaturated hydraulic conductivity thereby increasing the water content within the onion shaped wetted zone up to full saturation numerical simulations indicate that above hydrostatic pressure is developed within intermediate saturated layers enhancing wetting front propagation

soil surface characteristics influence on infiltration in black marls application to the super sauze earthflow southern alps france soil surface characteristics sscs have a strong influence on the infiltration properties at the soil surface they can explain spatial variations in the infiltration processes observed under natural rainfall for relatively little differentiated material and can help us to understand the surface and subsurface hydrology of landslides representative of some of black marls landscapes of the french southern alps this paper presents the results of investigations into the influence of sscs using careful morphological description in situ tension disc infiltrometry and statistical analysis hierarchical ascending classification and stepwise discriminant analysis the site studied is the super sauze earthflow the selected infiltration and runoff variables were described for 233 microplots chosen all over the earthflow the results show that an approach based on a description of relevant variables influencing water infiltration can validate a typology based on expert knowledge hydraulic conductivity at saturation was measured on 36 undisturbed soil cores and at low negative pressure heads on 83 microplots the dispersion exceeds three orders of magnitude at each pressure head a statistical analysis of the data set obtained by describing selected variables showed the relevance of the black marl descriptors when defining types of ssc that enable us to distinguish significant hydrodynamical behaviour this leads us to suggest a distribution of hydraulic conductivity curves near saturation for each ssc type which can be used as a key to distribute local hydraulic conductivity values adapted to black marl hillslopes as well as the types of ssc at a microplot scale leading to types of hydrodynamic properties the typology of combinations of sscs at a coarser scale should lead to types of hydrological response and to identification of hydrological and geomorphological response units copyright 2003 john wiley sons ltd

two possible routings for overflow from lake agassiz during the younger dryas a reply to comment by t fisher t lowell h loope on alternative routing of lake agassiz overflow during the younger dryas new dates paleotopography a re evaluation

a warning system for rainfall induced shallow failures abstract it is widely recognised that soil slips and debris flows are triggered by short intense storms owing its geologic geomorphologic and climatic settings the piedmont region nw italy is highly prone to the occurrence of this kind of landslides in the last two centuries in fact a total of 105 severe meteoric events which triggered shallow failures occurred and of these 18 events took place from 1990 to 2002 a fair number of rainfall thresholds have been proposed in the literature defined both on empirical or on physical bases empirical thresholds are defined collecting rainfall data for landslide meteoric events and for events without landslides while physical thresholds are based on numerical models that consider the relation between rainfall pore pressure and slope stability the main objective of this paper is the identification of the empirical triggering thresholds for the piedmont region four meteoric events were selected and analysed november 4 5 1994 july 7 8 1996 april 27 30 2000 october 13 16 2000 because they supply a wide range of variation for both rainfall parameters duration intensity cumulative rainfalls and the number of induced landslides in the intensity duration plot the critical limit is described by the equation i 19d 0 50 where i rainfall intensity expressed in mm h and d rainfall duration expressed in hours such a limit is traced to envelop 90 of the points on the graph in the ni d diagram the triggering thresholds are given by the equations ni 0 76d 0 33 and ni 4 62d 0 79 where ni normalised intensity with respect to the annual precipitation map expressed in mm h pma 100 in the article the different meaning of these thresholds is discussed finally the diagram ni ncr is proposed the triggering threshold is given by the expression ni 0 09ln ncr 0 54 where ncr is the normalised cumulative critical rainfall mm pma 100 the application of the triggering thresholds as a fundamental element in a warning system dedicated to the safeguarding of population in landslide prone areas is discussed in detail an operating procedure which is presently being verified and tested in the studied area is described

the relationship between the landslide frequency and hydrogeological aspects a case study from a hilly region in northern bavaria germany lidar data and other data bases such as geological maps topographical maps and orthophotos were used to build a landslide inventory of more than 1000 landslides in a study area of about 1590 km2 all landslides were tested particularly during extensive field investigations analysis of the landslide inventory reveals a high dependency between the spatial ratio of the landslides and the lithological setting in the study area as almost two thirds of all objects are tied to one lithological setting hard rock overlying alterable rock this condition is fulfilled in three different combinations of geological formations geological settings the analysis of the degree of landslide frequency along the borders linear ratio between the involved formations shows that there is a big difference in their susceptibility to landslides the present study attempts to reveal the basic relationship between the hydrological context of the study area and the observed susceptibility to landslides of the three different geological settings therefore calculated groundwater discharges observed springs within the mapped landslides calculated mean infiltration area for groundwater generation and annual precipitation were included into a more detailed consideration a comparison of the gathered results indicates that there is a strong connection between these different features in the study area

isostatic rebound in the northwestern part of the lake agassiz basin isobase changes and overflow abstract based on new gps elevation data on the upper and lower campbell strandlines in the northwestern part of the glacial lake agassiz basin the trend of isobases representing differential glacio isostatic rebound in that region is shown to bend and assume a nearly west east orientation this differs from the northwest southeast orientation to the southeast of the study area which others had projected into the northwestern corner of the lake agassiz basin this means that there was more isostatic depression than previously thought north of 53 n the difference in slopes on reconstructed water planes of the upper and lower campbell beaches is less with these isobases which better reflects the short period of time between their formation it is likely that the change in orientation of isobases reflects the presence of a thick keewatin ice center to the north our revised west east isobase reconstruction indicates that when the lake was at the campbell beach levels 9900 9400 14c b p lake agassiz overflowed across the paleo divide at wycherley lake saskatchewan which controlled flow through the northwestern outlet of lake agassiz during part of its history overflow would not have occurred through the wycherley lake channels at this time using the old isobase projections

temporal occurrence and activity of landslides in the area of cortina d ampezzo dolomites italy abstract this article shows the results of research on landslides carried out in the area of cortina d ampezzo dolomites italy within the framework of the epoch project of the european community the investigated area where tourism activities and infrastructures are highly developed has been affected by several landslides since the retreat of the wurnian glaciers and is at present still affected by active slides and flows which endanger some villages after a geological and geomorphological description the distribution in space and time of landslides which occurred in the surroundings of cortina d ampezzo is presented the type activity frequency and when possible the age of mass movements have been outlined furthermore special attention is focused on the landslides active at present which are reactivations of ancient movements the results from the monitoring systems which were installed in order to survey kinematic and hydrogeologic parameters and define the movement rate are shown the research enables the reconstruction of the post wurmian geomorphological evolution of a site in the dolomites that appears to be very peculiar both on account of the wide distribution of landslides and the intense human activity

seasonal variation of moisture content in unsaturated sandstone inferred from borehole radar and resistivity profiles understanding the processes controlling recharge to aquifers is critical if accurate predictions are to be made on the fate of contaminants in the subsurface environment in order to understand fully the hydrochemical mechanisms in the vadose zone it is essential that the dynamics of the hydrology can be suitably characterised the correlation between moisture content and both bulk dielectric and resistivity properties of porous media is well established using suitably placed sensors in boreholes detailed depth profiles of dielectric and resistivity behaviour have been monitored over a period of two years at a triassic sherwood sandstone aquifer field site at hatfield england the borehole borehole transmission radar and borehole resistivity profiles show a significant correlation through appropriate petrophysical relationships derived from core samples seasonal dynamics of the vadose zone are seen to illustrate the migration of wetting and drying fronts over the monitoring period at a second field site in eggborough located 17 km from hatfield similar temporal changes in moisture content in the sandstone were observed using borehole radar profiles travel times of seasonal wetting fronts through the sandstone at both sites appear to be approximately 2 m per month the retardation of this front propagation in the top 3 m is also common to both sites suggesting that pollutant transport may be principally controlled by near surface sediments the results have important consequences to existing groundwater modelling programmes that are being utilised to predict transfer of agricultural chemicals through the vadose zone

geotechnical aspects of soil slips in alpine regions abstract slope movements are due to many different causes numerous investigations carried out during the last ten years have led to the supposition that almost all slope movements and particularly those occurring in soils are conditioned by a significant combination of factors for the alpine regions quantity duration and kind of precipitation have to be considered as direct mechanical causes combined with such contributing factors as geological and soil mechanical properties aspect vegetation slope inclination and slope morphology they will determine the type dimensions and process of slope movements the detailed investigation of 140 slope movements in slightly cohesive soils show that the process of movement is represented by sliding and flow events in particular it was found out that shallow scars with planar slides predominate so that the supposition of an infinite slope model for slope stability appears to be justified in many cases debris flows and debris avalanches continued downslope of the source area of the scars

analysis of time varying rainfall infiltration induced landslide a case study of rainstorm induced landslide is modeled following the hourly rainfall time series from the stage of infiltration caused by induced slope movement and soil saturated to excess pore pressures transient rainfall infiltration and grid based regional slope stability analysis trigrs the grid based landslide stability analysis was conducted to model the increased pore pressures and runoff in the study area under the specified rainfall conditions the generated time variances of pore pressures help determine landslide characteristics and mechanisms under rainfall conditions inputs of soil properties and permeability parameters for landslide stability analysis in the study area were prepared by trigrs adopted for transient infiltration analysis results of the analyses show that under heavy rainfall conditions the infiltrated slope is unstable and the time of debris masses movement initiated is correlated to the recorded time in the initiated landslide characteristics and effects are considered and reflected in the numerical modeling under combinations of topography land use climatic and geological conditions results reveal that there is a plane failure surface and a potential circular failure surface at the study site besides the rock topple failures in the crest a grid based slope stability analysis incorporated with the gis spatial functions is more advantageous than the traditional two dimensional analysis for specified slope profiles to determine the whole behavior of a slope

electrical resistivity tomography ert based subsurface characterisation of pakhi landslide garhwal himalayas india pakhi landslide is one of the major debris slides of retrogressive nature along national highway nh 58 corridor from rishikesh to badrinath in garhwal himalayas india the present work is the first such attempt in one of the landslides in indian himalayas and in the present case study the subsurface characterization of the landslide was carried out with an aim to correlate the subsurface lithology slip surface and geometry of the landslide using borehole investigation and electrical resistivity tomography ert techniques the results from ert survey along and across the landslide could help to delineate different strata layers thereby deciphering the probable slip surface of the landslide activity further based on the landslide model drawn from the ert interpretations it can be stated that the crown portion of the right flank is more vulnerable to sliding phenomenon and that of the left flank is more prone to erosion the results obtained from both the borehole investigation and ert techniques are observed to be in great agreement and could complement each other for subsurface detailed investigation of landslide the integration of both these techniques provides useful information about the landslide activities and defines the geometry of the landslide hence it will be quite helpful in planning mitigation strategies as well as usefulness of each of these techniques