landslide driven erosion and slope channel coupling in steep forested terrain ruahine ranges new zealand 1946 2011 abstract landslides are an important means of conveying sediment from slopes to channels in steepland environments but landsliding is a discontinuous process this means that any single assessment in time of their contribution to the sediment cascade is of limited value to better understand landscape dynamics and the contribution of landslides to slope channel coupling over time this paper quantifies connectivity over a time span of 65 years in small steep headwater catchments in the southern ruahine range new zealand temporal variability in landsliding and slope channel coupling was assessed using six sets of aerial photography flown between 1946 and 2011 from which over 6900 landslides were mapped in arcgis of which up to 78 connected with the stream network estimates of the volume of material delivered by landslide erosion to headwater channels were based on ground survey measurements of selected landslide scars and suggest that between 1946 and 2011 over 5 million m 3 of sediment was delivered from slopes to channels in the 221 km 2 study area forest cover is not sufficient to prevent this erosion these catchment systems are particularly vulnerable to high magnitude storm events which significantly elevate landslide intensity and enhance sediment delivery as occurred in the mid 1970s the legacy of these events remains in these headwater channels with ongoing consequences for stream and hazard management in and adjacent to the ranges

late pliocene and quaternary glaciations of new zealand abstract evidence of late pliocene glaciations is fragmentary the ross glaciation in northwest south island is correlated with the first marine faunal evidence of marked cooling in the wanganui basin in southern north island it is inferred to be in the 2 6 2 4 ma age range the porika glaciation in a separate area of northwest south island is younger judged by palynology and is correlated with a cooling 2 2 2 1 ma bp inferred from stratigraphic evidence of lowered sea level in the wanganui basin a gap of 1 5 ma in the record of glaciations is largely filled by wanganui basin marine sediments although an unconformity cuts out the record between ca 1 45 and 1 0 ma bp since then the many sedimentary cycles caused by sea level changes are presumed to be glacio eustatic in origin uplifted interglacial marine terraces back to marine oxygen isotope stage 17 and river terraces formed by cold climate aggradation are linked into the cyclic sequence through loess and tephra in their cover beds east of the south island cores from the dsdp site 594 in the southwest pacific record the earliest glaciation and higher in the core nine periods of south island glaciation in the last 0 7 ma onshore because of uplift and erosion only the last four glaciations assigned to oxygen isotope stages 10 8 6 and 4 2 are identified being named nemona waimaunga waimea and otira glaciations they are best known in north westland northwest south island where the relations of glacial outwash and interglacial shoreline deposits are displayed the late otira glaciation stage 2 is radiocarbon dated as beginning somewhat before 22 3 ka bp culminating ca 18 ka bp and ending at ca 14 ka bp when rapid deglaciation began a relatively small advance at ca 12 ka bp may have been followed by little change until after 8 6 ka bp recession was then followed by a period of advance from ca 5 ka bp until recent centuries and a subsequent recession that still continues

ice moraine and landslide dams in mountainous terrain we review recent work on ice moraine and landslide dams in mountainous terrain thus complementing several comprehensive summaries on glacier dams in intracontinental and arctic areas of low relief we discuss the roles of tectonic and climatic forcing on ice moraine and landslide dam formation and sudden drainage and focus on similarities and differences between their geomorphic impacts on confined valleys drained by steep bedrock and gravel bed rivers despite numerous reported failures of natural dams in mountain belts throughout the world their relevance to long term dynamics of mountain rivers remains poorly quantified all types of dams exert local base level controls thus trapping incoming sediment and inhibiting fluvial bedrock incision pervasive geomorphic and sedimentary evidence of outburst events is preserved even in areas of high erosion rates suggesting that sudden dam failures are characterized by processes of catastrophic valley floor aggradation active channel widening and downstream dispersion of sediment during which little bedrock erosion seems to be achieved we find that in the absence of direct evidence of former dams a number of similarities among the geomorphic and sedimentologic characteristics of catastrophic outburst flows may give rise to ambiguous inferences on the dam forming process this is especially the case for tectonically active mountain belts where there is ample and comparable potential for the formation and failure of ice moraine landslide and polygenetic dams concomitant with climatic oscillations or earthquake disturbance hence the palaeoclimatic implications of erroneously inferring the cause of dam formation may be significant we recommend that future research on natural dams in mountainous terrain addresses a climate and earthquake controlled systematics in the pattern of formation and failure b quantification of response of mountain rivers to catastrophic outburst events and their concomitant process sequences c elaboration of a comprehensive classification of natural dams in mountainous terrain with special attention to polygenetic dams d physical based modelling of dam formation failure and routing of water and sediment outbursts and e quantitative controls on the contribution of natural dams to sediment budgets in mountainous terrain

chemical weathering in high sediment yielding watersheds new zealand 1 we have determined the chemical erosion yields for fifteen watersheds in new zealand ranging in size from 12 2 to 2928 km2 these rates coupled with previously measured physical erosion yields allow us to compare these two modes of landscape denudation the physical erosion yields are some of the highest measured in the world although in most instances the chemical erosion yields are only a small fraction of the total erosion yields the absolute values are very high our data strongly support the notion that chemical erosion rates are greatly influenced by the yield of physical erosion and that the rapid production of fresh surfaces as a result of high physical erosion rates and subsequent denudation is critical to the high chemical erosion yields observed

a biomarker perspective on paleoproductivity variations in two late quaternary sediment sections from the southeast atlantic ocean abstract sedimentary inventories of selected molecular biomarkers in two sediment sections from the african continental margin below highly productive surface waters in the southeast atlantic ocean each spanning the last 76 kyr were investigated and compared to each other a principal component analysis of the stratigraphic data separated groups of biomarkers representing different assemblages of biological sources and or different diagenetic histories related to their chemical structures and their metabolic role in the food chain the concentrations of long chain n alkenones n diols the major n ketool and loliolide and its epimer isololiolide are correlated with paleoproductivity estimates that were calculated from organic carbon contents this group of relatively refractory compounds very likely represents those planktonic communities which contributed significantly to surface water productivity and subsequent burial of organic carbon during the considered time interval concentrations of dust transported terrigenous long chain fatty acids c24 to c28 are interpreted to be related to the intensity of upwelling driving winds and are also significantly correlated with high contents of organic matter concentrations of cholesterol and the major short chain fatty acids are not related to the marine paleoproductivity signal most likely as a consequence of their nonspecific origin and their metabolic role during heterotrophic feeding processes abundances of 24 ethylcholest 5 en 3 ol and its saturated counterpart 24 ethyl 5 cholestan 3 ol the major steroid alcohols in both sedimentary environments appear not to be related to any of the above mentioned components and probably represent the contribution of algal species adapted to nutrient conditions different from those of other major primary producers differences between both environments the angola dome and the benguela coastal upwelling are evident in the relative distribution of major components and the stratigraphic behavior of selected compounds relative to other variables these differences are discussed in relation to specific characteristics of both oceanographic environments 1999 elsevier science ltd all rights reserved

revised palaeoclimatic significance of mueller glacier moraines southern alps new zealand a sequence of late holocene moraines on the foreland of the mueller glacier southern alps new zealand forms part of a local moraine age database used to establish a regional glacier chronology and subsequently to investigate potential intra hemispheric and global climate forcing mechanisms we present new sedimentological and geomorphological evidence that a set of these moraine ridges previously considered to represent individual advances constitutes a single moraine complex the mueller memorial moraine formed by supraglacial transport of a large volume of landslide debris to the glacier terminus because a moraine formed in this way is not necessarily associated with an advance triggered by a climate event we question the palaeoclimatic significance of the mueller memorial moraine as well as that of other moraines in comparable settings our findings suggest that the mode of formation and glacio dynamical context of moraines whose ages contribute to existing palaeoclimate reconstructions need to be re examined in order to assess the reliability of these reconstructions copyright 2015 john wiley sons ltd

quantitative identification of erosional lake bonneville shorelines utah abstract although the major shorelines of pleistocene lake bonneville have been recognized for more than 100 years less prominent shorelines have proven difficult to quantitatively identify and correlate since the time of g k gilbert by applying the savitzky golay filter and methodology of hare et al to high resolution lidar data of selected erosional shorelines five distinct correlatable shorelines between the well described bonneville and provo shorelines on the transgressive limb of the lake bonneville hydrograph are documented the results provide a framework for determining whether these transgressive features represent lake oscillations or stillstands during the height of the last glacial maximum in the eastern great basin of the western united states with possible attendant paleoclimate implications

effects of earthquake induced landslides on sediment budget and transport over a 50 yr period landsliding during a magnitude 7 7 earthquake in 1929 in northwestern south island new zealand delivered up to 400 000 m 3 km 2 of sediment to stream channels first to third order channels were buried to depths of as much as 10 m with sedimentary rock debris for distances ranging from 2 of the 92 km 2 study area because of the coarse grain size of the sedimentary rock debris and trapping of sediment in numerous landslide dammed lakes sand and pebble sized debris originating from landslides on a 6 6 km 2 area of granite has been transported downstream no more than 10 km at least 50 to 75 of this granitic debris is retained in the fourth order 92 km 2 catchment 50 yr after the earthquake the long retention times of sediment and the volume of debris supplied by landslides during a large earthquake suggest that earthquake induced landsliding is the principal sediment supply mechanism in the region

supply and removal of sediment in a landslide dominated mountain belt central range taiwan abstract a strong coupling between hillslope and valley systems is often inferred for mountain landscapes dominated by bedrock landsliding we reveal the nature of this link using data sets on landsliding and sediment transport from two montane catchments draining the eastern central range of taiwan here the magnitude frequency distribution of landslides can be modeled by a robust power law but this scale invariance is not mirrored in the sediment discharge at the mountain front instead downstream sediment loads reflect a complex response to both sediment supply and ambient hydraulic conditions the rivers do not transport significant amounts of sediment unless it is provided by hillslope mass wasting in the catchment removal of landslide debris is a function of the transport capacity of the stream at the site of entry thus there is a dual supply and transport control on sediment loads in bedrock floored streams over a monitoring period of 25 yr the bulk of the sediment leaving the mountain bel

sediment transfer by shallow landsliding in the queen charlotte islands british columbia despite the importance of landsliding in routing sediment through mountainous drainage basins few studies have documented landsliding rates over extended time and space scales we have investigated landsliding in surficial material in the queen charlotte islands using a large inventory of events derived from aerial photography covering an area of 166 7 km 2 the mean erosion rate for shallow landsliding is 0 10 mm a 1 which is at the upper end of shallow landsliding rates observed in the pacific northwest and coastal british columbia but several orders of magnitude lower than rock based landsliding rates reported in the literature probability distributions for landslide area and volume are somewhat convex in form flattening of the curve found at low magnitudes may be due to sampling bias or physical mechanisms inhibiting failure and the steepening for high values may exist because the sampling period is not long enough to adequately represent large events landslides generally initiate on hillslope gradients greater than 0 50 0 60 the largest numbers of landslides occur on south to southwest facing slopes and east to northeast facing slopes most events occur on concave and straight hillslopes in upper slope positions landsliding rates were found not to be af fected by rock type hillslopes in the queen charlotte islands are often mantled by weathered quaternary deposits and hence landsliding events are not directly controlled by weathering of bedrock about 31 of landslides identified in this study deposited material in stream reaches with about 83 of these landslides deposited in reaches with gradients between 3 and 10 resume malgre la grande contribution des glissements de terrain a acheminer des sediments a travers des bassins de drainage montagneux peu d etudes ont documente les taux de glissements de terrain sur une longue periode de temps et sur de grandes superficies nous avons fait des recherches sur des glissements de materiaux de surface dans les iles de la reine charlotte en utilisant un grand inventaire d evenements tires de photographies aeriennes couvrant une re

the formation and failure of natural dams of the numerous kinds of dams that form by natural processes dams formed from landslides glacial ice and late neoglacial moraines present the greatest threat to people and property landslide dams form in a wide range of physiographic settings the most common types of mass movements that form landslide dams are rock and debris avalanches rock and soil slumps and slides and mud debris and earth flows the most common initiation mechanisms for dam forming landslides are excessive rainfall and snowmelt and earthquakes landslide dams can be classified into six categories based on their relation with the valley floor type i dams 11 of 184 landslide dams from around the world that we were able to classify do not reach from one valley side to the other type ii dams 44 span the entire valley floor in some cases depositing material high on opposite valley sides type iii dams 41 move considerable distances both upstream and downstream from the landslide failure type iv dams 1 are rare and involve the contemporaneous failure of material from both sides of a valley type v dams 1 also are rare and are created when a single landslide sends multiple tongues of debris into a valley and forms two or more landslide dams in the same reach of river type vi dams 3 involve one or more failure surfaces that extend under the stream or valley and emerge on the opposite valley side many landslide dams fail shortly after formation in our sample of 73 documented landslide dam failures 27 of the landslide dams failed less than 1 day after formation and about 50 failed within 10 days over topping is by far the most common cause of failure the timing of failure and the magnitude of the resulting floods are controlled by dam size and geometry material characteristics of the blockage rate of inflow to the impoundment size and depth of the impoundment bedrock control of flow and engineering controls such as artificial spill ways diversions tunnels and planned breaching by blasting or conventional excavation glacial ice dams can produce at least nine kinds of ice dammed lakes the most dangerous are lakes formed in main valleys dammed by tributary glaciers failure can occur by erosion of a drainage tunnel under or through the ice dam or by a channel over the ice dam cold polar ice dams generally drain supraglacially or marginally by downmelting of an outlet channel warmer temperate ice dams tend to fail by sudden englacial or subglacial breaching and drainage late neoglacial moraine dammed lakes are located in steep mountain areas affected by the advances and retreats of valley glaciers in the last several centuries these late neoglacial dams pose hazards because 1 they are sufficiently young that vegetation has not stabilized their slopes 2 many dam faces are steeper than the angle of repose 3 these dams and lakes are immediately downslope from steep crevassed glaciers and near vertical rock slopes and 4 downstream from these dams are steep canyons with easily erodible materials that can be incorporated in the flow and increase flood peaks the most common reported failure mechanism is overtopping and breaching by a wave or series of waves in the lake generated by icefalls rockfalls or snow or rock avalanches melting of ice cores or frozen ground and piping and seepage are other possible failure mechanisms natural dams may cause upstream flooding as the lake rises and downstream flooding as a result of failure of the dam although data are few for the same potential energy at the dam site ownstream flood peaks from the failure of glacier ice dams are smaller than those from landslide moraine and structed earth fill and rock fill dam failures moraine dam failures appear to produce some of the largest downstream flood peaks for potential energy at the dam site greater than 1011 1012 joules differences in flood peaks natural dam failures appear to be controlled by dam characteristics and failure mechanisms

holocene history of deep seated landsliding in the north fork stillaguamish river valley from surface roughness analysis radiocarbon dating and numerical landscape evolution modeling documenting spatial and temporal patterns of past landsliding is a challenging step in quantifying the effect of landslides on landscape evolution while landslide inventories can map spatial distributions lack of dateable material landslide reactivations or time access and cost constraints generally limit dating large numbers of landslides to analyze temporal patterns here we quantify the record of the holocene history of deep seated landsliding along a 25 km stretch of the north fork stillaguamish river valley washington state usa including the 2014 oso landslide which killed 43 people we estimate the ages of more than 200 deep seated landslides in glacial sediment by defining an empirical relationship between landslide deposit age from radiocarbon dating and landslide deposit surface roughness we show that roughness systematically decreases with age as a function of topographic wavelength consistent with models of disturbance driven soil transport the age roughness model predicts a peak in landslide frequency 1 000 ybp with very few landslide deposits older than 7 000 ybp or younger than 100 ybp likely reflecting a combination of preservation bias and a complex history of changing climate base level and seismic shaking in the study area most recent landslides have occurred where channels actively interact with the toes of hillslopes composed of glacial sediments suggesting that lateral channel migration is a primary control on the location of large deep seated landslides in the valley

frictionite as evidence for a large late quaternary rockslide near kanchenjunga sikkim himalayas india implications for extreme events in mountain relief destruction abstract we present sedimentologic and petrographic field evidence of an extremely large 2 5 109 m3 late quaternary rockslide around dzongri 24 km s of kanchenjunga 8585 m a s l widespread occurrence of shattered leucogranites and migmatites deposited discordantly on top of undisturbed augen gneisses and separated by micro brecciated sliding surfaces indicate rapid movement during a large rockslide event occurrence of frictionite hyalomylonite in mineral samples indicates short term temperatures of 600 c in the moving rockslide mass along a 12 sliding plane from a sw direction of movement we infer a source 8 km ne of the deposit 5 km s of pandim 6691 m a s l where today a thick leucogranite intrusion marks a zone of weakness and failure of a postulated former mountain crest the mechanism of movement the dip of the sliding surface and the deposit preservation along ridge tops require that the dzongri rockslide ran out over an ice filled prek chu valley hence we prefer earthquake shaking over undercutting and glacial debuttressing as a possible trigger mechanism a regional review of other similarly large and catastrophic himalayan rockslides indicates that leucogranite intrusions are highly conducive to large scale failure in the higher himalayan crystalline hhc importantly high erosion rates have rendered this large rockslide deposit undetectable by remote sensing or digital elevation data which are commonly used for identifying evidence of such extreme events quantifying the contribution of such giant landslides in destroying some of the highest relief on earth will thus need further research attention

prolonged impact of earthquake induced landslides on sediment yield in a mountain watershed the tanzawa region japan abstract to determine for how long a landslide affects sediment discharge the sediment yields of 15 check dam basins were compared with the time series of landslide distributions in a mountain basin in the tanzawa region central japan the distribution of sediment yield was quantitatively estimated from deposition in the sediment pools of check dams the relationship between the landslide history and sediment discharge in the nakagawa river basin was examined for an approximately 80 year period two major landslide events occurred during this period the 1923 kanto earthquake and the 1972 disaster caused by heavy rainfall the resulting trend in sediment discharge of the whole basin estimated using reservoir sedimentation in the miho dam at its base was nearly constant with high sediment discharge 2897 m 3 km 2 yr 1 in the intervening quarter century despite the recovery of vegetation on landslide areas in this period comparisons of the landslide distributions resulting from the two disasters the sediment yields of check dam basins and the sediment discharge of the whole basin indicate that recent sediment discharge contains landslide debris that was originated by the kanto earthquake that occurred over 80 years ago thus to understand high sediment discharge it is essential to investigate not only the current basin condition and recent events but also the landslide history of the basin for at least the previous 100 years

sediment generation and delivery from large historic landslides in the southern alps new zealand abstract there is much variability of sediment yield in mountain river systems because it is influenced by both periodic e g snowmelt monsoonal circulation and episodic high intensity rainstorms earthquakes controls in the southern alps of new zealand landslides are dominant mechanisms of conveying large amounts of debris to river channels this paper attempts to quantify catastrophic modes of sediment delivery by presenting three recent examples of large landslides on the western slopes of the southern alps a combination of ground surveys dem based volume calculations and air photo interpretation attributes immediate postfailure sediment yields in excess of 70 000 t km 2 a 1 in the short term such landslide derived sediment pulses pose significant hazards to downstream settlements and infrastructure on alluvial fans where they cause massive aggradation increased flooding frequency and large scale channel avulsion in addition to intramontane valley floor obliteration or channel metamorphosis these geomorphic impacts may thus occur far beyond the initial locations of slope failure these catastrophic off site effects involve apparent net sediment delivery rates in the order of 10 5 10 6 m 3 a 1 the accurate quantification of the relative contribution of debris from the disturbing landslide to overall sediment flux is extremely difficult nonetheless are quantitative estimates of landslide derived sediment production and delivery important data to develop a more comprehensive understanding of the variability in alpine sediment flux such data are essential not only for use in hydraulic engineering or catchment management but also in gauging potential future impacts from rainstorm and earthquake induced landsliding in the southern alps

persistent alluvial fanhead trenching resulting from large infrequent sediment inputs we present laboratory and field evidence that in mountainous catchment fan systems persistent alluvial fanhead aggradation and trenching may result from infrequent large sediment inputs we suggest that the river fan systems along the fault bounded range front of the western southern alps new zealand are likely to be in a dynamic equilibrium on 103 yr timescales superimposed on which their fanheads undergo long term cumulative episodic aggradation these fanheads are active only in rare events do not take part in the usual behaviour of the catchment fan system and require much longer to exhibit dynamic equilibrium than the rest of the fan these findings 1 increase our knowledge of the effects of extreme events on alluvial fan morphodynamics in humid climates 2 question the general applicability of inferring past climatic or tectonic regimes from alluvial fan morphology and stratigraphy and 3 provide a conceptual basis for hazard zonation on alluvial fans copyright 2006 john wiley sons ltd

carbon export from mountain forests enhanced by earthquake triggered landslides over millennia rapid ground accelerations during earthquakes can trigger landslides that disturb mountain forests and harvest carbon from soils and vegetation although infrequent over human timescales these co seismic landslides can set the rates of geomorphic processes over centuries to millennia however the long term impacts of earthquakes and landslides on carbon export from the biosphere remain poorly constrained here we examine the sedimentary fill of lake paringa new zealand which is fed by a river draining steep mountains proximal to the alpine fault carbon isotopes reveal enhanced accumulation rates of biospheric carbon after four large earthquakes over the past 1 100 years probably reflecting delivery of soil derived carbon eroded by deep seated landslides cumulatively these pulses of earthquake mobilized carbon represent 23 5 of the record length but account for 43 5 of the biospheric carbon in the core landslide simulations suggest that 14 5 million tonnes of carbon mtc could be eroded in each earthquake our findings support a link between active tectonics and the surface carbon cycle and suggest that large earthquakes can significantly contribute to carbon export from mountain forests over millennia large earthquakes export significant carbon from mountain forests over millennia according to analyses of sediments mobilized by earthquake triggered landslides in new zealand

the spatial and temporal patterns of aggradation in a temperate upland gravel bed river intensive field monitoring of a reach of upland gravel bed river illustrates the temporal and spatial variability of in channel sedimentation over the six year monitoring period the mean bed level in the channel has risen by 0 17 m with a maximum bed level rise of 0 5 m noted at one location over a five month winter period these rapid levels of aggradation have a profound impact on the number and duration of overbank flows with flood frequency increasing on average 2 6 times and overbank flow time increasing by 12 8 hours this work raises the profile of coarse sediment transfer in the design and operation of river management specifically engineering schemes it emphasizes the need for the implementation of strategic monitoring programmes before engineering work occurs to identify zones where aggradation is likely to be problematic exploration of the sediment supply and transfer system can explain patterns of channel sedimentation the complex spatial seasonal and annual variability in sediment supply and transfer raise uncertainties into the system s response to potential changes in climate and land use thus there is a demand for schemes that monitor coarse sediment transfer and channel response copyright 2009 john wiley sons ltd

fluvial evacuation of landslide material from bedrock confined channels under controlled experimental conditions abstract the supply of sediment from hillslopes to channels is rarely constant with discrete events e g landslides known to transfer large volumes of sediment in geologically short periods of time especially in tectonically active areas understanding the rates and patterns of subsequent sediment evacuation is important for understanding variability of landscape evolution as well as mitigating the risk of geohazards associated with bed aggradation and the loss of channel capacity to convey flood waters here we performed a series of controlled laboratory flume experiments to explore the controls on sediment transport after a single sediment input in scenarios with i different initial input volumes 4 25 kg under constant flow conditions 40 l s ii a constant initial input volume 12 kg under different flow magnitudes 5 60 l s and iii a repeat of the input sediment volumes in scenario i but with the same volume of water delivered using a ramped hydrograph 0 60 0 l s we find the presence of sediment piles impacts the flow hydraulics with a backwater effect developing upstream of the pile that causes a flow acceleration around the location of the pile for a given discharge larger sediment piles have a greater impact on the flow hydraulics which in turn induces higher rates of sediment transport and erosion of the pile in all cases sediment remains at the initial pile input location for the duration of the sediment evacuation acting to protect the bed from erosion we highlight the role of geomorphic hydraulic interactions in controlling the sediment evacuation and suggest there is an optimal combination of pile size and flow conditions flow magnitude and hydrograph shape for accelerated rates of sediment transport which are important for the short term and long term channel dynamics and the landscape evolution variability

rockfall talus slopes and associated talus foot features in the glaciated uplands of great britain and ireland periglacial paraglacial or composite landforms

holocene reactivations of catastrophic complex flow like landslides in the flysch carpathians czech republic slovakia catastrophic complex flow like landslides cflls are characterised by a deep seated retrogressive landslide of structurally unfavourably oriented rocks and earthflows that occupy the lower slope positions and originate due to the liquefaction of material accumulated on the upper slopes these landslides are locally important geomorphic agents of late quaternary mountain evolution in the flysch belt of the outer western carpathians czech republic slovakia most of the cflls dammed and steepened adjacent valleys radiocarbon dating suggests that a majority of them moved repeatedly throughout the holocene namely approx every 1 2 ka dated events occurred during humid phases of the younger dryas holocene transition 11 5 9 4 cal ka bp atlantic chronozone 7 4 6 6 cal ka bp the beginning of the subboreal chronozone ca 4 6 cal ka bp and primarily within the subatlantic chronozone at ca 2 0 8 cal ka bp 50 of all events our study suggests that slopes based on an unfavourable structural setting and affected by long term deep seated gravitational deformations may produce cflls even if they are located in medium high mountains although our chronological dataset is influenced by the erosion of older landforms most of the dated reactivations correlate with regional increase in precipitation identified by previous palaeoenvironmetal studies

characteristics of sediment dynamics following large scale sediment supply events in mountain watersheds in japan abstract large scale sediment supply events lses cause not only a sudden increase in sediment discharge immediately after their occurrence but also a long term condition of elevated sediment yield in japan many lses triggered by heavy rainfall or earthquakes have created high risks for sediment related disaster however the difference between sediment dynamics following a lse triggered by rainfall and one triggered by an earthquake is unclear as the sediment dynamics due to rainfall and those due to earthquakes have not been compared using consistent methodology in this study we estimated the volume of sediment supply vl m3 time series of the volume of sediment yield vy m3year 1 and the non dimensional parameter nvy as estimated by dividing vl by the catchment area and annual maximum 3 day rainfall amount using the same methodology for 16 events in eight study basins in japan we used annual maximum 3 day rainfall amounts as a surrogate for discharge using these parameters we estimated the period over which the effect of a lse continues pls sediment retention time residence time tr1 and time for active sediment yield to recover to the background level recovery time tr2a in addition we estimated the recovery time tr2b based on when the maximum of nvy immediately after the lse decreased to a certain extent this calculation allowed us to estimate the recovery time even when background level was unknown both residence and recovery times ranged from

landsliding and sediment flux in the central swiss alps a photogrammetric study of the schimbrig landslide entlebuch abstract this study explores the effects of hillslope mass failure on the sediment flux in the waldemme drainage basin central swiss alps over decadal time scales this area is characterized by abundant landslides affecting principally flysch units and is therefore an important sediment source the analysis concentrates on the schimbrig landslide that potentially contributes up to 15 to the sediment budget of the waldemme drainage basin volumetric changes are quantified using high resolution elevation models that were extracted using digital photogrammetric techniques sediment discharge data were used to constrain the significance of the landslide for sediment flux in the channel network the temporal extent of the photogrammetric analysis ranges from 1962 to 1998 including an earth slide event in 1994 the analyses reveal that during periods of low slip rates of the landslide nearly all of the displaced sediments were eroded and supplied to the channel network in contrast during active periods only a fraction of the displaced landslide mass was exported to the trunk stream interestingly the 1994 earth slide event did not disturb the long term sediment discharge pattern of the channel network nor did it influence the sediment flux at a weekly scale however suspended sediment pulses correlate with higher than average precipitation events this was especially the case in august 2005 when a storm event 100 years return period triggered several debris flows and earth flows in the whole drainage basin and in the schimbrig area this storm did not result in a significant increase in the slip rates of the entire landslide s main body it is therefore proposed that debris flows and earth flows perform the connectivity between hillslope processes e g landsliding and the trunk stream during and between phases of landslide activity in this particular setting

precipitation landsliding and erosion across the olympic mountains washington state usa abstract in the olympic mountains of washington state landsliding is the primary surface process by which bedrock and hillslope regolith are delivered to river networks however the relative importance of large earthquakes versus high magnitude precipitation events to the total volume of landslide material transported to valley bottoms remains unknown in part due to the absence of large historical earthquakes to test the hypothesis that erosion is linked to precipitation approximately 1000 landslides were mapped from google earth imagery between 1990 and 2015 along a 15 km wide 85 km long 1250 km2 swath across the range the volume of hillslope material moved by each slide was calculated using previously published area volume scaling relationships and the spatial distribution of landslide volume was compared to mean annual precipitation data acquired from the prism climate group for the period 1981 2010 statistical analysis reveals a significant correlation r 0 55 p

deriving a long paleoseismic record from a shallow water holocene basin next to the alpine fault new zealand a sedimentary sequence that was highly sensitive to fault rupture driven changes in water level and sediment supply has been used to extract a continuous record of 22 large earthquakes on the alpine fault the fastest slipping fault in new zealand at hokuri creek in south westland an 18 m thickness of holocene sediments accumulated against the alpine fault scarp from ca a d 800 to 6000 b c we used geomorphological mapping sedimentology and paleoenvironmental reconstruction to investigate the relationship between these sediments and alpine fault rupture we found that repeated fault rupture is the most convincing mechanism for explaining all the features of the alternating peat and silt sedimentary sequence climate has contributed to sedimentation but is unlikely to be the driver of these cyclical changes in sediment type and paleoenvironment other nontectonic causes for the sedimentary alternations do not produce the incremental increase in basin accommodation space necessary to maintain the shallow water environment for 6800 yr our detailed documentation of this near fault sedimentary basin sequence highlights the advantages of extracting paleoearthquake records from such sites the continuity of sedimentation abundance of dateable material and pristine preservation of older events

fluvial transportation and sedimentation of the fu shan small experimental catchments the fu shan long term ecological site is one of taiwan s mid altitude forest drainage basins this study provides an estimation of the denudation rate for two small catchments within that site data upon which the estimation is based include topographic maps site surveys and measurements on bed dissolved and suspended loads over the period from 1998 to 2000 the result indicates that typhoons and storm rainfalls as well as geomorphic and ancestral conditions have major impacts on hydrological and sediment regimes of these drainage basins the total sediment output measured at weir no 1 indicates a denudation rate of 2 7 mm per year which is 53 of the figure calculated from the data measured at weir no 2 since the geological settings in these basins are similar the result is a demonstration of the nonlinear relationship between basin areas and sediment production in basin no 1 90 of the total sediment output is dissolved load however this figure plunges to 42 in basin no 2 in contrast with the fact that the runoff per unit area in basin no 2 is 35 higher than that in basin no 1 the denudation rates of these two drainage basins are relatively high in comparison with those from other areas around the world

management responses to pulses of bedload sediment in rivers abstract rivers can experience sudden pulses of sediment from human and natural erosion processes that can accumulate in the bed abundant studies have examined the sources and dynamics of sediment pulses and problems caused by these pulses particularly flooding avulsions and habitat simplification much less has been written about what managers can do about sediment pulses and that is the purpose of this review the first option for managers is to do nothing and this decision can be informed by many case studies and by theory on the propagation and character of sediment pulses their diffusion translation and celerity doing nothing should be informed by the secondary effects of sediment pulses on channels including widening avulsions and tributary interactions if managers decide that something needs to be done about the sediment they have four options 1 reducing the sediment supply at source 2 trapping sediment in the channel 3 accelerating sediment transport through a reach and 4 directly extracting sediment the most common of these actions is undoubtedly to reduce the supply at source but there are few examples of the consequences of this for sediment pulses there are even fewer examples of trapping accelerating and extracting sediment all of these options have great potential for managing sediment pulses however they also have the potential to trigger incision of tributaries and of the channel behind the passing sediment wave overall the literature equips managers to understand the dynamics of sediment pulses but it does not yet equip them to confidently manage these geomorphic events

landslide impact on organic carbon cycling in a temperate montane forest in humid forested mountain belts bedrock landslides can harvest organic carbon from above ground biomass and soil ocmodern while acting to refresh the landscape surface and turnover forest ecosystems here the impact of landslides on organic carbon cycling in 13 river catchments spanning the length of the western southern alps new zealand is assessed over four decades spatial and temporal landslide maps are combined with the observed distribution and measured variability of hillslope ocmodern stocks on average it is estimated that landslides mobilized 7 6 2 9 tc km 2 yr 1 of ocmodern 30 of which was delivered to river channels comparison with published estimates of ocmodern export in river suspended load suggests additional erosion of ocmodern by small shallow landslides or overland flow in catchments the exported ocmodern may contribute to geological carbon sequestration if buried in sedimentary deposits landslides may have also contributed to carbon sequestration over shorter timescales 100 years 5 4 3 0 tc km 2 yr 1 of the eroded ocmodern was retained on hillslopes representing a net carbon sink following re vegetation of scar surfaces in addition it was found that landslides caused rapid turnover of the landscape with rates of 0 3 of the surface area per decade high rates of net ecosystem productivity were measured in this forest of 94 11 tc km 2 yr 1 which is consistent with rapid landscape turnover suppressing ecosystem retrogression landslide ocmodern yields and rates of turnover vary between river catchments and appear to be controlled by gradients in climate precipitation and geomorphology rock exhumation rate topographic slope copyright 2011 john wiley sons ltd

failure and flow development of a complex slide the 1993 sesa landslide abstract large landslides are often characterised by complex activity resulting from their ability to suddenly change behaviour in fact these landslides can pass from a slump to a flow characterised by relatively high mobility this characteristic is a cause of extremely high severity and hazard in areas affected by such phenomena an interesting case of a large slide in glacial deposits which occurred in 1993 in the valcamonica of the italian alps is presented different approaches both to characterise the coarse frictional materials involved in the slide and to model the slide initiation and its evolution are adopted the initial slide mass had a volume of almost 2 mm 3 and after its initial sliding motion along the slope flowed for about 7 km down the main valley stream voight s method has been used to analyse measured slope displacements recorded for a few years before the slope failure this analysis provided evidence that different times of failure could have been predicted beforehand by rigorous examination of the available data laboratory tests and image processing techniques have been performed to characterise the landslide material as resembling a bimrock block in matrix material slope stability analyses have been performed and a dynamic modelling method has been tested on the flow by comparing its results to those obtained by analysis of eyewitness statements and field observations on the mudline left by the flow finally existing empirical approaches for hazard assessment on an alluvial fan have been applied and modified to produce a hazard zonation map for the alluvial fan area by considering maximum expected discharge local geometry of the channel and the possibility of channel occlusion and subsequent avulsion

large rockslides in the southern central andes of chile 32 34 5 s tectonic control and significance for quaternary landscape evolution abstract the distribution and age of large 0 1 km2 pliocene to recent rockslides in the chilean cordillera principal 32 34 5 s the southern central andes has been analyzed to determine the rockslide triggering mechanisms and impact on regional landscape evolution most of the rockslides appear in the western cordillera principal and cluster along major geological structures variographic analyses show spatial correlation between rockslides geological structures and shallow seismicity a relative chronosequence was calibrated with existing 14c and 40ar 39ar dates and new cosmogenic nuclide exposure ages for selected rockslides rockslide induced sediment yield was estimated with empirical relations for rockslide area distributions throughout the quaternary rockslides have delivered sediment to streams at rates equivalent to denudation rates of 0 10 0 06 mm a 1 while estimates using short term 20 a seismicity records are 0 3 0 2 0 6 mm a 1 the estimates of sediment transfer and the spatial distribution of rockslides reflect a landscape in which tectonic and geological controls on denudation are more significant than climate

assessing the internal structure of landslide dams subject to possible piping erosion by means of microtremor chain array and self potential surveys abstract an integrated geophysical approach comprising microtremor chain array and self potential surveys was used to assess the internal structure of landslide dams subject to possible piping erosion in selected sites in japan and kyrgyzstan the non invasive geophysical approach is cost effective environmentally friendly and portable and hence it has proven to be valuable for the geotechnical assessment of landslide dams where piping can trigger failure of the dam while the microtremor chain array survey results revealed the internal structure of the landslide dam the self potential survey results indicated the path of anomalous seepage zones in the surveyed sites of long existing landslide dams the presence of a seepage path in the dam was confirmed by a good correlation between the areas of low phase velocity and large negative self potential anomalies in summary this integrated geophysical approach could be useful for the early risk assessment of landslide dams and prediction of landslide dam failure by piping

modelling centennial sediment waves in an eroding landscape catchment complexity sediment flux dynamics in fluvial systems have often been related to changes in external drivers of topography climate or land cover it is well known that these dynamics are non linear recently model simulations of fluvial activity and landscape evolution have suggested that self organization in landscapes can also cause internal complexity in the sedimentary record in this contribution one particular case of self organization is explored in the sabinal field study area spain where several dynamic zones of sedimentation and incision are observed along the current river bed whether these zones can be caused by internal complexity was tested with landscape evolution model lem lapsus landscape process modelling at multi dimensions and scales during various 500 year simulations zones of sedimentation appear to move upstream and downstream in eroding river channels waves these waves are visualized and characterized for a range of model settings under constant external forcing and the self organizing process behind their occurrence is analysed results indicate that this process is not necessarily related to simplifications in the model and is more generic than the process of bed armouring that has recently been recognized as a cause for complexity in lem simulations we conclude that autogenic sediment waves are the result of the spatial propagation in time of feedbacks in local transport limited deposition and detachment limited erosion conditions

sediment production and delivery from recent large landslides and earthquake induced rock falls in the upper soca river valley slovenia abstract landsliding not only changes the morphology of the terrain but is also an effective factor in sediment production extreme events such as earthquake induced large rock falls or rainfall induced landslides may during the event itself or in a period after it greatly increase the sediment delivery and river sediment transport the effects of strong earthquakes and large landslides on sedimentation are evident in the upper soca river basin nw slovenia the annual sediment production in the headwaters of this typical alpine valley in western slovenia is estimated to average 1000 m 3 km 2 a 1 in the last few years two large landslides triggered there were of comparable volume but differed regarding sediment delivery to the fluvial network the 2000 sto e landslide at 1 5 million m 3 was a debris flow that delivered more than 1 million m 3 to the koritnica river the strug complex landslide was initiated in 2001 by a rock slide and soon amounted to an estimated volume of 310 000 m 3 in 2002 it released over 20 rainfall induced debris flows on the order of 100 to 1000 m 3 to the fluvial system in mountainous terrain in the headwaters of the upper soca river slope failures may occur during strong earthquakes depending on the event magnitude the earthquake of april 12 1998 m s 5 6 caused more than 100 failures among them 50 rock falls about 260 000 m 3 of rock fall material will remain on hill slopes with no potential of reaching the river network while an estimated volume of 480 000 m 3 may be released to watercourses in a longer period during extreme events about 200 000 m 3 of rock fall debris was deposited in areas from where the material was released to watercourses during rainfall events as a consequence of the 1998 earthquake hyperconcentrated flows were observed during floods in some torrential tributary channels of the upper soca river after the earthquake of july 12 2004 m s 4 9 50 rather superficial slope failures including 38 rock falls were registered from 2000 until 2004 more than 150 000 m 3 sediments were dredged from the upper soca river channel

quaternary moraines vs catastrophic rock avalanches in the karakoram himalaya northern pakistan a history and conception of glacial events for the central karakoram himalaya proposed some 80 years ago by giotto dainelli are largely accepted today however certain deposits identified as terminal moraine complexes marking glacial episodes were actually emplaced by rock avalanches in the skardu and shigar intermontane basins of baltistan at least 15 rock avalanche events were previously mapped as moraine or till criteria used for distinguishing these catastrophic landslide deposits emphasize homogeneous lithology of rubble and matrix clast shape facies characteristics the large scale unity of emplacement and morphological relations to valley topography the deposits of three events at katzarah satpura and the north end of shigar valley have been reconstructed in detail thick supraglacial debris does not result in similar deposits extensive valley fills river terraces large sediment fans and lacustrine sediments formerly attributed to late glacial conditions are reinterpreted as postglacial events involving rock avalanches that interrupted fluvial development existing reconstructions of glaciations are left in doubt especially late glacial events in the central karakoram as are the roles assigned to karakoram main indus valley and western himalayan ice

experimental study on the triggering mechanisms and kinematic properties of large debris flows in wenjia gully debris flows are typically caused by natural terrain landslides triggered by intense rainfalls if an incoming mountain torrent flows along sloping channels at high velocity huge amounts of sediment from landslide dams and eroded channel beds will be entrained into the flows to form debris flows it is likely that large debris flows are due to the failure of many landslide dams of different scales due to bank slides or collapses bed erosion and solid transport the catastrophic debris flows that occurred in wenjia gully wenchuan earthquake area china on august 13 2010 two years after the mega earthquake were caused by intense rainfall and the serious erosion of sloping channels in the wake of the incident experimental tests were conducted to better understand the process of sediment erosion and entrainment on the channel bed and the formation of debris flows the results show that the bed erosion bank collapses and channel widening caused by erosion accounted for the triggering and scale amplification of downstream debris flows in the wenjia gully event this study illustrates how the hazardous process of natural debris flows can begin several kilometers upstream and how such a complex cascade of geomorphic events failure of landslide dams and erosion of the sloping bed can lead to catastrophic discharges neglecting recognition of these hazardous geomorphic and hydrodynamic processes may result in high cost c 2014 elsevier b v all rights reserved

tree ring analysis in the reconstruction of slope instabilities associated with earthquakes and precipitation the crimean mountains ukraine the crimean mountains in ukraine constitute a seismically active region that is abundant in various types of mass movement the limestone escarpments that rise above the black sea coast in the vicinity of the town of yalta are particularly subject to considerable rockfall landslide and debris flow processes that often endanger infrastructure and human life one of these very active slopes is the area of the ancient taraktash rockslide characterised by active block type movements lateral spreading toppling and incipient sliding rockfalls ongoing sliding activities and debris flows the aims of this study were i to employ tree ring analysis to reconstruct a record of slope instabilities mainly block type movements rockfalls landslides and debris flows within the taraktash slope deformation over a period of more than two centuries and ii to establish the degree of correlation between periods of enhanced slope activity and both historical earthquakes and climatic data the temporal frequency of significant slope processes was addressed through a tree ring analysis that took 738 increment cores from 255 crimean pine trees pinus nigra ssp pallasiana the tree ring record reveals periods of increased activity of block type movements rockfalls and landslides during the major earthquakes in 1790 1875 1927 and 1986 although the slope processes studied are predominantly driven by seismic activity their intensity and duration are also dependent on climatic factors this is especially true for landslides and debris flows which occurred mainly in years characterised by high precipitation totals

late quaternary slip rates and slip partitioning on the alpine fault new zealand abstract published geological data on late quaternary offsets on the alpine fault new zealand have been assembled into a common format and analysed with respect to uncertainties uncertainties arise mainly from measurement of offset features relating apparent offsets to actual fault slip and dating the offset features despite the considerable uncertainties the data form a coherent set consistent with a relatively constant rate of strike slip of 27 5 mm year between milford sound and hokitika this rate represents 70 75 of the fault parallel interplate motion north of the confluence with the hope fault the rate drops substantially dip slip rates on the other hand show considerable variation along strike rising to a maximum of more than 10 mm year in the central section and decreasing to zero at the southern end partitioning of c 25 of the interplate slip on to structures east of the alpine fault occurs in the central section consistent with predictions from critical wedge models the partitioning of all the fault normal component of displacement on to other structures in the south may be related in part to a doubling in width of the deforming wedge to the east most probably however the fault normal displacement is mainly accommodated by underthrusting of the australian plate offshore due to a change in the nature of the crust from continental to oceanic

colluvial sediment dynamics in mountain drainage basins abstract colluvial sediment dynamics are examined using a 70 year landslide inventory in formerly glaciated mountain drainage basins of coastal british columbia canada landslide sediment transfer is documented by identifying landslide types and by characterizing preferential sites of landslide initiation delivery and storage across spatial scales data analysis reveals that open slope landslides delivering material to seasonal or perennial channels and fluvial terraces are the dominant mechanisms of sediment transfer this finding suggests high instability of the low order channel network and its ongoing re organization degradation after generalized sediment recharge occurred in the last glacial maximum in the study period landslide activity across the landscape has generated net degradation on planar slopes and first order colluvial channels whereas unchannelled valleys higher order colluvial channels and alluvial channels have accumulated material the scaling relation of the landslide sediment yield appears to be controlled by the spatial arrangement of the relict glacial macro forms landslide yield is highest in unchannelled topography decreases at the scale of channel initiation ad 0 002 km2 and remains constant for drainage areas where length scales of cirque valley walls and hanging valley floors overlap 0 002

seismic cycles earthquakes landslides and sediment fluxes linking tectonics to surface processes using a reduced complexity model in tectonically active mountain ranges landslides triggered by earthquakes mobilise large volumes of sediment that affect river dynamics this sediment delivery can cause downstream changes in river geometry and transport capacity that affect the river efficiency to export this sediment out of the epicentre area the subsequent propagation of landslide deposits in the fluvial network has implications for the management of hazards downstream and for the long term evolution of topography over multiple seismic cycles a full understanding of the processes and time scales associated with the removal of landslide sediment by rivers following earthquakes however is still lacking here we propose a nested numerical approach to investigate the processes controlling the post seismic sediment evacuation at the mountain range scale informed by results from a reach scale model first we explore the river morphodynamic response to a landslide cascade at the reach scale using a 2d modelling approach the results are then used to describe empirically the evacuation of a landslide volume which avoids using a computationally extensive model in catchments which may have thousands of co seismic landslides second we propose a reduced complexity model to quantify evacuation times of earthquake triggered landslide clusters at the scale of a mountain range examining the hypothetical case of a mw 7 9 earthquake and its aftershocks occurring on the alpine fault new zealand our approach combines an empirical description of co seismic landslide clusters with the sediment export processes involved during the post seismic phase our results show that the inter seismic capacity of the mountain range to evacuate co seismic sediment is critical to assess the sediment budget of large earthquakes over one to several seismic cycles we show that sediment evacuation is controlled by two timescales 1 the transfer time of material from hillslopes to channels and 2 the evacuation time of the landslide deposits once it has reached the fluvial network in turn post seismic sediment evacuation can either be connectivity limited when sediment delivery along hillslopes is the main limiting process or transport limited when the transport by rivers is the limiting process despite high values of runoff we suggest that the southern alps of new zealand are likely to be in connectivity limited conditions for connection velocities 2 m yr 1 are sufficient to allow most of co seismic sediments to be mobilised and potentially exported out of the range within less than one seismic cycle because of the poorly constrained rate of sediment transfer along hillslopes our results potentially raise the issue of co seismic sediment accumulation within mountain ranges over several seismic cycles and of the imbalance between tectonic inputs and sediment export we therefore call for renewed observational efforts to better describe and quantify the physical processes responsible for the redistribution and mobilization of sediment from landslide scars and deposits

large landslides and their effect on sediment flux in south westland new zealand landslides and runoff are dominant erosional agents in the tectonically active alpine south westland area of new zealand characterized by high uplift rates and extreme orographic precipitation despite a high density of shallow debris slides and flows the geomorphic imprints of deep seated bedrock failures are dominant and persistent over 50 large 1k m 2 landslides comprising rock slide avalanches complex rotational and rock block slides wedge failures and deep seated gravitational slope deformation were detected on air photos and shaded relief images major long term impacts on alpine rivers include 1 forced alluviation upstream of landslide dams 2 occlusion of gorges and triggering of secondary riparian landslides and 3 diversion of channels around deposits to form incised meandering gorges remnants of large prehistoric i e pre 1840 landslide deposits possibly represent the low frequency in terms of total area affected yet dominant end of the spectrum of mass wasting in the western southern alps this is at odds with high erosion rates in an active erosional landscape large landslides appear to have dual roles of supplying and retaining sediment the implications of these roles are that 1 previous models of shallow landslide derived sediment flux need to be recalibrated and 2 geomorphic effects of earthquake induced landsliding may persist for at least 10 2 years copyright 2005 john

sediment flux from a mountain belt derived by landslide mapping in humid uplands landsliding is the dominant mass wasting process in the western southern alps of new zealand landslides are scale invariant and have a power law magnitude frequency distribution independent studies from other regions suggest that this is a general property of landsliding this observation is of critical importance to the evaluation of the impact of events of different length scales over different time intervals on landscape evolution it is particularly useful when estimating regional geomorphic rates because it constrains the frequency and overall significance of extreme events which cannot otherwise be evaluated by integrating the complete response of the system we estimate the regional denudation rate due to landsliding to be 9 4 mm yr 1 sediment discharge from the western southern alps is dominated by landslide derived material

fluvial response to rapid episodic erosion by earthquake and typhoons tachia river central taiwan abstract analysis of typhoon and earthquake triggered landsliding and fluvial response in the tachia river central taiwan documents highly episodic sediment supply over decade to century timescales landslide data from the chi chi earthquake 1999 and subsequent typhoons 2001 2004 and 2005 quantify the sediment supply from these events fluvial response was investigated by decadal scale and century scale longitudinal river profile data spanning 1904 to 2008 and by sediment delivery recorded in suspended sediment load and reservoir sedimentation data our results show that the different time periods of satellite images and aerial photographs used in previous studies make it difficult to unambiguously identify the causes of landslides previously attributed by some studies to the effects of the chi chi earthquake rather than subsequent high intensity precipitation in response to significant variability in sediment delivery from hillslopes century scale profile variation data indicate substantial bed surface elevation change of 2 6 6 7 m and decade scale bed surface elevation change of 1 1 3 3 m since 1993 the downstream reaches incised in response to bedload sediment trapping by reservoirs while headwater reaches aggraded in response to increased sediment delivery from uplands a tremendous increase in reservoir sedimentation after 2000 likely reflects the effects of the highest decade average daily rainfall since 1900 suspended sediment load data indicate a post chi chi earthquake increase in sediment concentration in low flow events but do not exhibit the clear influence on sediment yields at higher flows as e g typhoons reported by others for fluvial response in the epicentral region

fluvial response to large rock slope failures examples from the himalayas the tien shan and the southern alps in new zealand we describe remnants of large 10 7 10 10 m 3 late pleistocene to holocene rockslides and rock avalanches that block ed rivers and are preserved in the himalayas the tien shan and the new zealand southern alps despite rates of uplift and erosion of up to 10 mm year 1 these natural dams control fluvial response on 10 1 10 4 year timescales by a storing and releasing sediment during forced alluviation and fluvial re incision b relocating river channels through diversion or seepage c inhibiting river erosion into bedrock d formingpersistentlong profileknickpointsandknickslopesassociatedwithsteephigh energy n10 3 wm 2 breachand epigenetic bypass gorges and fluvial hanging valleys and e shaping valley floor morphology sediments indicate that rockslidedammed lakes may persist up to 10 4 years before being drained or infilled several short lived 10 0 10 2 year historical rockslide dams in the indian and nepal himalayas and the southern alps have had marked volumetric impacts on catchment sediment budgets shortly following failure therefore we caution against the linear extrapolation of sediment delivery from prehistoric rockslide dams through time as a response variable we find reach scale changes to channel gradient to be prominent and persistent indicators of fluvial response to large rock slope failures 2006 elsevier b v all rights reserved

effects of punctuated sediment supply on valley floor landforms and sediment transport large infrequent fluxes of sediment to streams by mass wasting are intrinsic to the erosion regime of mountain drainage basins to elucidate the role of mass wasting in the construction and evolution of steep land channel environments it is crucial that we identify the processes involved and recognize their legacy on the valley floor in the winter of 1996 nine storm triggered debris flows carried 18 000 m 3 of coarse debris into the upper reaches of the south fork of gate creek oregon cascade range during flood flow analysis of resulting channel morphologies and bed textures shows that the sediment moved downstream as a wave like pulse or pulses overwhelming the channel and causing it to braid with flooding and alluvial deposition over the valley floor downstream progression of the sediment wave resulted in vertical accretion of the valley floor with sediment carried as bedload the maximum depth of valley floor burial being set by the amplitude of the wave passage of the wave left a channel incised to bedrock inset between coarse grained alluvial terraces this study examines the genesis of these features at gate creek and points to such terraces as field indicators of massive episodic influxes of sediment and the associated formation of fluvially transported sediment waves

coseismic landsliding estimates for an alpine fault earthquake and the consequences for erosion of the southern alps new zealand landsliding resulting from large earthquakes in mountainous terrain presents a substantial hazard and plays an important role in the evolution of mountain ranges however estimating the scale and effect of landsliding from an individual earthquake prior to its occurrence is difficult this study presents first order estimates of the scale and effects of coseismic landsliding resulting from a plate boundary earthquake in the south island of new zealand we model an mw 8 0 earthquake on the alpine fault which has produced large m 7 8 8 2 earthquakes every 329 68 years over the last 8 ka with the last earthquake 300 years ago we suggest that such an earthquake could produce 50 000 20 000 landslides at average densities of 2 9 landslides km 2 in the area of most intense landsliding between 50 and 90 are expected to occur in a 7000 km2 zone between the fault and the main divide of the southern alps total landslide volume is estimated to be 0 81 0 87 0 55 km3 in major northern and southern river catchments total landslide volume is equivalent to up to a century of present day aseismic denudation measured from suspended sediment yields this suggests that earthquakes occurring at century timescales are a major driver of erosion in these regions in the central southern alps coseismic denudation is equivalent to less than a decade of aseismic denudation suggesting precipitation and uplift dominate denudation processes nevertheless the estimated scale of coseismic landsliding is considered to be a substantial hazard throughout the entire southern alps and is likely to present a substantial issue for post earthquake response and recovery

evaluation of different dtms in sediment connectivity determination in the mascarada river watershed southern brazil abstract the study of sediment connectivity based on the geomorphic characteristics of the watershed has gained interest during the last decades the calculation of connectivity indexes for a mountainous watershed that is normally susceptible to landslides allows the recognition of the unstable areas that have higher connection to any point such as the watershed outlet thus the knowledge of spatial patterns of connectivity within the watershed is very useful in the sediment related disaster management because the connectivity provides useful information on sediment pathways the objective of the present study was to test four different global dtms to compute the sediment connectivity index ic in the mascarada river watershed 320 km2 southern brazil by analyzing the land use for each pixel the manning roughness was determined and used for the weighting factor in ic calculation field survey and satellite image analysis showed that 420 landslides occurred in this watershed on january 5th 2017 the calculated ic value maps demonstrated that the hillslopes with landslide occurrences have higher values of ic among the tested dtms the one with the highest resolution 12 5 m resolution dtm showed the best representation of the flow paths with high ic values for all the resolutions the ic mean values of the landslides scars were larger compared to the remaining area of the hillslopes where the landslides occurred which implies higher connectivity of the landslides to the watershed outlet the results also showed that the 12 5 m resolution dtm generated the lowest mean and the largest amplitude of ic values differentiating areas with high and low connectivity it is concluded that the global dtm 12 5 m is capable to provide important information on sediment connectivity and that together with a landslide inventory it can be an important tool for sediment management in mountainous watersheds

differential diagenesis of rhythmic limestone alternations supported by palynological evidence alternating cemented and uncemented fine grained layers from pliocene periplatform carbonates of the great bahama bank have fundamentally different diagenetic features the cemented layers consist predominantly of microspar interpreted as an early marine shallow burial cement the intercalated uncemented softer layers are devoid of microspar cement and exhibit signs of mechanical compac tion precursor sediments of both cemented and uncemented layers apparently consisted largely of aragonite needles the needles in the compacted layers show signs of dissolution suggesting that the calcium carbonate required for cementation of the uncompacted layers was provided by aragonite dissolution within the compacted layers the lack of compaction in the cemented layers shows that cementation and hence aragonite dissolution in the adjacent compacted layers took place in the shallow burial realm the dissolved carbonate was trans ported by diffusion to adjacent layers and reprecipitated as calcite cement thereby preventing significant compaction of these layers these processes are not yet complete in the material examined and some aragonite remains in the compacted layers the sedimentary composition of the two rock types compacted and uncompacted is similar indicating a similar precursor sediment for both between 1 5 and 7 times the concentration of palynomorphs oc curs in the compacted layers apparently the result of passive diage netic enrichment although the trigger for diagenetic differentiation has not been determined the pure limestone succession studied here appears to serve as a clay free analog to limestone marl alternations

source to sink sediment transfers environmental engineering and hazard mitigation in the steep var river catchment french riviera southeastern france steep coastal margins are potentially subject to mass wasting processes involving notable landslide activity and sediment evacuation downstream by steep gradient streams sediment transfer from short source to sink segments coupled with mountain hydrological regimes regulate patterns of river channel aggradation and coastal sediment supply in such geomorphic settings on the steep french riviera margin sediment transfers from existing landslides or from various minor mass wasting processes to stream channels may result following bursts of heavy concentrated rainfall high magnitude flooding and massive sediment transport downstream are generally related to unpredictable extreme rainfalls both mass movements and channel sediment storage pose serious hazards to downvalley settlements and infrastructure a consideration of channel sediment storage patterns in the var river catchment the most important catchment in this area highlights two important shortcomings relative to environmental engineering and hazard mitigation practices in the first place the appreciation of geomorphic processes is rather poor this is illustrated by the undersized nature of engineering works constructed to mitigate hazards in the upstream bedload dominated channels and by the unforeseen effects that ten rock dams constructed in the early 1970s have had on downstream and coastal sediment storage and on sediment dispersal patterns and consequently valley flooding secondly planners and environmental engineers have lacked foresight in valley and coastal management issues on this steep setting notably as regards the reclaimed areas of the lower var channel and delta liable to flooding urbanization and transport and environmental engineering works have progressively affected patterns of storage and transport of fine grained sediments in the lower var channel and delta meanwhile the problems raised by these changes have not been adequately addressed in terms of scientific research a necessary future step in bettering the engineering solutions implemented to contain natural hazards or to harness water and sediment resources is that of fine scale analysis of source to sink sediment transfer processes of sediment budgets of time scales of storage in stream channels and finally of high magnitude hydrometeorological forcing events in this area the way all these aspects have been modulated by engineering practices and socioeconomic development should also be an important part of such an analysis

evolution of a landslide induced sediment wave in the navarro river california a streamside landslide delivered 60 000 m3 of mixed size sediment to the navarro river a sinuous gravel bed channel drainage area 535 km2 at the end of the annual high runoff period in spring 1995 the deposit formed a 9 m high dam that partially breached within several hours but recessional flows entrained little material until the following high runoff season the landslide afforded the opportunity to measure the evolution of a sediment wave from its inception to near obliteration and particularly to test relative tendencies for translation and dispersion of a sediment wave in a natural gravel bed channel this study represents a simple case the wave originated from a single input the preexisting channel was relatively uniform and resistant banks prevented adjustments in width we surveyed channel topography over a 1 5 4 5 km reach centered on the landslide dam each year from 1995 to 1999 and we sampled bed material downstream of the dam in 1995 and 1997 landslide material was coarser than ambient bed material but all sizes were mobilized by subsequent peak flows abrasion of weathered and fractured graywacke sandstone landslide material was roughly an order of magnitude greater than the ambient river gravel the sediment wave dispersed and mostly disappeared within a few years with no measurable translation sediment filled the reservoir created by the eroding landslide dam until throughput of bed load was restored in 1998 the stationary wave crest eroded until in 1999 it was 1 m higher e mail dsutherl fs fed us than the preslide elevation as the wave profile flattened its detectable leading edge extended downstream from 620 m in 1995 to 1600 m in 1997 downstream advance of the wave was associated with coarsening of bed material the sediment wave created a longitudinal disturbance in sediment transport by using the dam as a reference datum of zero bed load transport we computed longitudinal variations in annual bed load and suspended sediment transport rates in 100 m increments downstream of the dam these longitudinal variations were controlled by scour and fill of the bed and by abrasion of bed load particles bed load transport rates in the first and second years after the landslide increased in the landslide vicinity and then decreased downstream as sediment deposited behind the advancing leading edge of the wave the location of peak bed load transport rate advanced from the first year 400 m to the second 800 m we used a physically based one dimensional model cui et al 2002b to hindcast annual changes in transversely averaged bed elevation over the study reach agreement between measured and predicted bed elevations was very good this result supports our conclusion that once emplaced sediment waves in gravel bed rivers tend to disperse with little or no translation

a precipiton based approach to model hydro sedimentary hazards induced by large sediment supplies in alluvial fans mountain ranges are frequently subjected to mass wasting events triggered by storms or earthquakes and supply large volumes of sediment into river networks besides altering river dynamics large sediment deliveries to alluvial fans are known to cause hydro sedimentary hazards such as flooding and river avulsion here we explore how the sediment supply history affects hydro sedimentary river and fan hazards and how well can it be predicted given the uncertainties on boundary conditions we use the 2d morphodynamic model eros with a new 2d hydrodynamic model driven by a sequence of flood a sediment entrainment transport deposition model and a bank erosion law we first evaluate the model against a natural case the 1999 mount adams rock avalanche and subsequent avulsion on the poerua river fan west coast new zealand by adjusting for the unknown sediment supply history eros predicts the evolution of the alluvial riverbed during the first post landslide stages within 30 cm the model is subsequently used to infer how the sediment supply volume and rate control the fan aggradation patterns and associated hazards our results show that the total injected volume controls the overall levels of aggradation but supply rates have a major control on the location of preferential deposition avulsion and increased flooding risk fan re incision following exhaustion of the landslide derived sediment supply leads to sediment transfer and deposition downstream and poses similar but delayed hydro sedimentary hazards our results demonstrate that 2d morphodynamics models are able to capture the full range of hazards occurring in alluvial fans including river avulsion aggradation and floods however only ensemble simulations accounting for uncertainties in boundary conditions e g discharge history initial topography grain size as well as model realization e g non linearities in hydro sedimentary processes can be used to produce probabilistic hazards maps relevant for decision making

scale amplification of natural debris flows caused by cascading landslide dam failures debris flows are typically caused by natural terrain landslides triggered by intense rainfalls if an incoming mountain torrent collapses a series of landslide dams large debris flows can form in a very short period moreover the torrent can amplify the scale of the debris flow in the flow direction the catastrophic debris flows that occurred in zhouqu china on 8 august 2010 were caused by intense rainfall and the upstream cascading failure of landslide dams along the gullies in the wake of the incident a field study was conducted to better understand the process of cascading landslide dam failures and the formation of debris flows this paper looks at the geomorphic properties of the debris flow gullies estimates the peak flow discharges at different locations using three different methods and analyzes the key modes i e different landslide dam types and their combinations of cascading landslide dam failures and their effect on the scale amplification of debris flows the results show that five key modes in luojiayu gully and two modes in sanyanyu gully accounted for the scale amplification of downstream debris flows in the zhouqu event this study illustrates how the hazardous process of natural debris flows can begin several kilometers upstream as a complex cascade of geomorphic events failure of landslide dams and erosion of the sloping bed can scale to become catastrophic discharges neglecting recognition of these hazardous geomorphic and hydrodynamic processes may result in a high cost

landslides affecting sedimentary characteristics of reservoir basin typhoons aere 2004 and matsa 2005 caused high nephelometric turbidity in the shihmen reservoir in northern taiwan jeopardizing the operation of the reservoir for several days and ultimately impacting the living conditions and economy of the downstream residents the torrential rains caused landslides and debris flows in upland areas and flowed into riverbeds likely contributing significantly to the suspended sediment yields in the reservoir this investigation elucidates how upland landslides affect sediment attributes in the reservoir basin study methods including field observations spatial analysis in gis and aerial photo interpretation are adopted to trace the sediment sources and contributing factors to the landslide torrential rains induced landslides and debris flows upland causing river incisions and soil erosion in landslide areas lacking vegetation these factors together with the conditions of the engineered structures and geologic vulnerabilities of the area caused suspended sediment yield in the reservoir the high nephelometric turbidity could potentially reoccur with masses of landslide derived sediment remaining upland and in the riverbed

controls on fluvial evacuation of sediment from earthquake triggered landslides large earthquakes in active mountain belts can trigger landslides which mobilize large volumes of clastic sediment delivery of this material to river channels may result in aggradation and flooding while sediment residing on hillslopes may increase the likelihood of subsequent landslides and debris flows despite recognition of these processes the controls on the residence time of coseismic landslide sediment in river catchments remain poorly understood here we assess the residence time of fine grained 5 mm day 1 together with previous observations from the c e 1999 chi chi earthquake in taiwan our results demonstrate the importance of landslide density and runoff intensity in setting the duration of earthquake triggered landslide impacts on river systems

patterns and controls of sediment production transfer and yield in the illgraben quantification of the volumes of sediment removed by rock slope failure and debris flows and identification of their coupling and controls are pertinent to understanding mountain basin sediment yield and landscape evolution this study captures a multi decadal period of hillslope erosion and channel change following an extreme rock avalanche in 1961 in the illgraben a catchment prone to debris flows in the swiss alps we analyzed photogrammetrically derived datasets of hillslope and channel erosion and deposition along with climatic and seismic variables for a 43 year period from 1963 to 2005 based on these analyses we identify and discuss 1 patterns of hillslope production channel transfer and catchment sediment yield 2 their dominant interactions with climatic and seismic variables and 3 the nature of hillslope channel coupling and implications for sediment yield and landscape evolution in this mountain basin our results show an increase in the mean hillslope erosion rate in the 1980s from 0 24 0 01 m yr 1 to 0 42 0 03 m yr 1 that coincided with a significant increase in air temperature and decrease in snow cover depth and duration which we presume led to an increase in the exposure of the slopes to thermal weathering processes the combination of highly fractured slopes close to the threshold angle for failure and multiple potential triggering mechanisms means that it is difficult to identify an individual control on slope failure on the other hand the rate of channel change was strongly related to variables influencing runoff a period of particularly high channel erosion rate of 0 74 0 02 m yr 1 1992 1998 coincided with an increase in the frequency and magnitude of intense rainfall events hillslope erosion exceeded channel erosion on average indicative of a downslope directed coupling relationship between hillslope and channel and demonstrating the first order control of rock slope failure on catchment sediment yield and landscape evolution

effects of topography lithology rainfall and earthquake on landslide and sediment discharge in mountain catchments of southeastern taiwan abstract from 1996 through 2007 several heavy typhoons and earthquakes precipitated landslide hazards in southeast taiwan in the present study we analyze the impact of topography lithology rainfall and earthquakes on landsliding and sediment transport by quantifying the landslide ratio ratio of landslide area to catchment area and the sediment discharge for the sinwulu and luye upstream catchments of the peinan river the steep topography in these two catchments causes a large proportion of landslide ratios on slopes to exceeding 50 a condition which accelerates the delivery of landslide debris to the downslope channel the landslide ratios of 0 84 2 30 are obviously related to the rock strength and discontinuity density of the terrain but we find the magnitude of landsliding and sediment discharge to vary with the occurrence of earthquakes typhoon induced rainstorms generate the bulk of sediment discharge in the study catchments though the landslide debris is transported by the huge amounts of runoff produced by rainstorms a contributing factor is the recent occurrence of severe earthquakes which weakened the geomaterial leading in turn to further increases of fluvial sediment during subsequent typhoons additionally the finding that eventual reduction of unit sediment concentration after high magnitude earthquake events reveals that the downslope transport of landslide debris associated with earthquake activity and subsequent typhoon events precipitates a relatively short term 1 3 year increase of erosion rates in these two study areas in southeastern taiwan

landslide induced river channel avulsions in mountain catchments of southwest new zealand pulsed or chronic supply of landslide debris to valley floors has historically caused substantial aggradation and channel instability in several alpine catchments of sw new zealand in this regional investigation of landslide impacts on river morphology three types of landslide induced channel avulsion are discerned i upstream backwater avulsions ii contact avulsions and iii downstream loading avulsions the basis for this qualitative geomorphic process response framework is the principal direction of fluvial response with respect to its position relative to the causative landslide emplacement site downstream avulsions have the highest damage potential to land use and infrastructure on unconfined mountain fringe alluvial fans in the wake of such events catastrophic aggradation may obliterate up to several km2 of mature floodplain forests by burial under several metres within a few decades estimates of mean aggradation rates are high 220 mm year 1 and exceed long term 103 year trends of fluvial degradation by an order of magnitude future potential avulsion routeways may be detected by geomorphic mapping of abandoned channels which are preferentially reactivated in the wake of landslide induced sediment waves