temporal patterns of mass movements in the french alps abstract in massmovement hazard assessment it is important to include a temporal dimension in order to give a better insight into the activity of landslides in the french alps the temporal pattern of active landslides in varved clays and terres noires marls was studied as well as the temporal occurrence of debris flows the active landslides in varved clays and terres noires show in detail quite different patterns of movement which is ascribed to the different hydrological conditions in the landslide bodies the activity of debris flows is controlled by the occurrence of exceptionally high intensity rainstorms this means that the temporal pattern of debris flow activity will reflect the variability of storm rainfall activity as a first approach an average recurrence interval of some ten years was detected based on dendrochronological and lichenometrical evidence

analysis of landslide frequencies and characteristics in a natural system coastal british columbia two hundred and one debris slides and debris ows were analyzed in a 286 km2 study area on the west coast of vancouver island british columbia canada the study area remains essentially untouched by humans and therefore affords a natural setting in which to examine slope processes landslides were identi ed and characterized on aerial photographs from 1 15 000 to 1 31 680 and were then mapped and transferred to a gis for analysis based on detailed landslide surveys we propose a new method to accurately determine volume of landslides of this type by measured total area results indicate average denudation rates of 56 m3 y 1 km 2 and higher natural rates of failure than analogous regions in coastal british columbia in contrast the landslide rates are substantially less than those from forested watersheds landslide distribution is spatially clustered in air photograph epochs and we propose intense storm cells within regional events as the causal mechanism further failures occurred preferentially over the west coast crystalline complex by 1 4 times a metamorphic assemblage of gabbros schists and amphibolites but 1 5 times less often over the island plutonic suite a granitic intrusive formation the former result represents a new nding while the latter corroborates ndings of previous authors we examined magnitude frequency relationships of the data set and present for the rst time a strong argument that the rollover effect is not merely an artefact but is instead a consequence of the physical characteristics of the landslides themselves we subsequently analyzed magnitude frequency relationships from two other complete data sets from coastal british columbia and produced a family of curves corroborating this result copyright 2004 john wiley sons ltd

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

fluvial geomorphology and paleohydrology in japan abstract an introduction to fluvial geomorphology and paleohydrology in japan is provided for researchers who are unfamiliar with these topics studies by japanese geomorphologists are reviewed including those published only in japanese language journals emphasis is placed upon the following aspects 1 abundant sediment yields from steep watersheds subjected to frequent heavy rains despite heavily vegetated conditions 2 extensive sedimentation in mountain piedmonts and coastal fluvial plains especially during the holocene 3 catastrophic hydro geomorphological events associated with earthquakes and volcanic eruptions and 4 the impacts of the increased heavy rainfall during the pleistocene holocene transition on the post glacial development of hillslopes and alluvial fans these geomorphological characteristics differ from those in continental regions such as europe and north america indicating that research on japanese fluvial systems can contribute a great deal to the understanding of the global variety of fluvial geomorphology recent work on paleohydrological reconstruction in japan is also reviewed

landslides induced by the wenchuan earthquake and the subsequent strong rainfall event a case study in the beichuan area of china abstract the wenchuan earthquake on may 12 2008 triggered massive landslides and a subsequent strong rainfall prompted the development of new landslides as well as the reactivation of some pre existing landslides the highest seismic intensity zone of the wenchuan earthquake in beichuan china was selected as a case study to analyze the influence of the earthquake and the subsequent heavy rains on landslide evolution we selected this study area 414 km 2 since it was close to the coseismic surface rupture and because it suffered strong ground motion based on the interpretation of high resolution aerial photographs and remote sensing imagery combined with field investigation 40 pre earthquake landslides and 2221 coseismic landslides were identified with total landslide areas of 2 68 km 2 and 30 81 km 2 respectively there were 134 large over 50 000 m 2 co seismic landslides that covered a surface area of 15 54 km 2 and represented approximately 50 4 of the total area of the co seismic landslides the coseismic landslides were mainly located on the hanging wall of the causative fault and on the steep valley sides of the jian river and its tributaries a strong rainfall event occurred four months after the wenchuan earthquake and induced 969 new landslides which covered a 6 90 km 2 area and enlarged 169 existing landslides 2 48 km 2 the landslides were identified in spot5 images ultimately we found that earthquake tremors and the subsequent rainstorm severely disturbed the surface strata resulting in a large number of landslides

linking landslide susceptibility to sediment yield at regional scale application to romania abstract it is generally accepted that catchment sediment yield sy t km 2 y 1 can be strongly influenced by landsliding nevertheless due to data requirements only few studies investigated this effect at a regional scale the objective of this study is therefore to explore the potential of a landslide susceptibility map for explaining the spatial variation of sy in romania we selected 133 catchments in romania for which sy was measured during a period of at least 10 years for each catchment we derived a variety of proxies that potentially explain sy including several indicators of landslide occurrence the latter were derived from a published landslide susceptibility map results show that sy is significantly correlated with mean landslide susceptibility r 2 0 30 estimates of average sheet and rill erosion rates showed a much weaker correlation with sy r 2 0 06 further analyses showed that the strong correlation between sy and landslide susceptibility is mainly attributed to regional variations in lithology and seismicity especially the latter may play a crucial role in understanding denudation rates at regional scales e g by facilitating the occurrence of landslides using landslide proxies that also account for sediment connectivity did not result in stronger correlations overall our results show that landslide susceptibility maps can be a highly useful tool to predict sy at regional scales provided that they incorporate all relevant factors

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

development and controlling factors of gullies and gully complexes east coast new zealand sequential aerial photographs of a small headwater catchment in the waiapu basin east coast region north island new zealand were interpreted to measure and analyse temporal changes in active area of gullies and gully complexes for a longer time span 1939 2003 and with higher temporal resolution compared to previous studies we focus on the conditions leading to the development of gullies and gully complexes under pasture and forest by using topographic thresholds slope area relationships of catchments for the initiation of gullies and gully complexes in addition the influence of two different lithologies as well as the occurrence of major rainfall events was related to gully activity twenty gullies and four gully complexes occupying 62 5 ha or 12 5 per cent of the catchment area occurred in the study catchment between 1939 and 2003 however the majority of these were not active at all of the dates studied gullies developed in the sandstone dominated tapuwaeroa formation tended to attain their maximum size by 1957 with a mean catchment area of 2 1 ha gullies developed in mudstone of the whangai formation attained their maximum size in 1939 with a mean catchment area of 4 31 ha exceptions are gullies which developed into mass movement deposits or into an earth flow deposit as well as gullies developed under indigenous forest topographic threshold values for gullies under pasture and indigenous forest show that values for gullies under forest plot far above the threshold line of gullies under pasture indicating that the topographical threshold for gully development under forest is higher compared to under pasture a threshold value of 9 4 ha in catchment area is needed for the development of gully complexes under pasture all located in the whangai formation and with the same orientation as the strike of the mudstones gully complex area and dominance of mass movement erosion increased with larger catchment area a decreasing distance to the threshold line for gullies under pasture indicates a later development for gully complexes no gully complexes developed under indigenous forest indicating that the threshold value for gully complex development is higher than for gully complexes under pasture and was not reached in the study area a model of shifting topographical threshold for gully development for a given catchment is developed which depends on land use when a catchment has an indigenous forest cover the topographical threshold is very high after conversion to pasture threshold values decrease drastically with the invasion of scrub the threshold slowly increases and returns to a similar level to that under indigenous forest after reforestation development of gullies and gully complexes is a highly dynamic phenomenon and phases of expansion and inactivity indicate that models describing only unidirectional advancing stages without periods of inactivity are not suitable therefore this study adds more phases to models of gully and gully complex development in the east coast region the threshold line for gully initiation under pasture and a value of 9 4 ha in catchment area for gully complex initiation permits one to predict which catchments under similar environmental settings develop gullies and gully complexes on a physical basis this enables land managers to implement sustainable land use strategies to reduce erosion rates of gullies and gully complexes copyright 2006 john wiley sons ltd

landslides caused by the m 7 6 tecoman mexico earthquake of january 21 2003 abstract the tecoman mexico earthquake also called the colima earthquake of january 21 2003 m 7 6 triggered several hundreds of landslides in the coastal cordilleras of colima state near the earthquake source and several thousands in the volcanic highlands north and northwest of colima city these landslides mostly shallow and disrupted failures caused minor damage to roads to a railroad and to irrigation systems in one area extensive post earthquake rock fall activity indicates a possible long term instability that could threaten dwellings and other infrastructure located nearby in the coastal cordilleras most of the landslides were generated by failures of artificially cut slopes especially along roads the rocks of the coastal cordilleras are generally well indurated and landslides occurred only where the rocks were made locally susceptible by weathering the presence of prominent discontinuities with unfavorable orientations or intense fracturing or shearing in contrast to the coastal cordilleras the volcanic rocks to the north were more susceptible to the occurrence of seismically triggered landslides the greatest number and concentrations of landslides occurred there and the landslides were larger than those in the coastal cordilleras even though this volcanic terrain was farther from the earthquake source here stretches of river bluffs several hundred meters long had been stripped of vegetation and surficial material by coalescing landslides and several days after the main shock thousands of small rock falls were still occurring each day indicating an ongoing hazard the high susceptibility of volcanic materials to earthquake generated landslides conforms to findings in other recent earthquakes

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

lake sediments record cycles of sediment flux driven by large earthquakes on the alpine fault new zealand large earthquakes in mountain regions commonly trigger extensive landsliding and are important drivers of erosion but the contribution of this landsliding to long term erosion rates and seismic hazard remains poorly understood here we show that lake sediments record postseismic landscape response as a sequence of turbidites that can be used to quantify erosion related to large moment magnitude m w 7 6 earthquakes on the alpine fault new zealand alpine fault earthquakes caused a threefold increase in sediment flux over the 50 yr duration of each postseismic landscape response this represents considerable delayed hazard following earthquake induced strong ground motion earthquakes were responsible for 27 of the sediment flux from the lake catchment over the past 1100 yr leading us to conclude that alpine fault earthquakes are one of the most important drivers of erosion in the range front of the southern alps

channel response to an extreme flood and sediment pulse in a mixed bedrock and gravel bed river we exploit a natural experiment caused by an extreme flood 500 year recurrence interval and sediment pulse derived from more than 2500 concurrent landslides to explore the influence of valley scale geomorphic controls on sediment slug evolution and the impact of sediment pulse passage and slug deposition and dispersion on channel stability and channel form sediment slug movement is a crucial process that shapes gravel bed rivers and alluvial valleys and is an important mechanism of downstream bed material transport further increased bed material transport rates during slug deposition can trigger channel responses including increases in lateral mobility channel width and alluvial bar dominance pre and post flood lidar and aerial photographs bracketing the 2007 flood on the chehalis river in south western washington state usa document the channel response with high spatial and temporal definition the sediment slug behaved as a gilbert wave with both channel aggradation and sequestration of large volumes of material in floodplains of headwaters reaches and reaches where confined valleys enter into broad alluvial valleys differences between the valley form of two separate sub basins impacted by the pulse highlight the important role channel and channel floodplain connectivity play in governing downstream movement of sediment slug material finally channel response to the extreme flood and sediment pulse illustrate the connection between bed material transport and channel form specifically the channel widened lateral channel mobility increased and the proportion of the active channel covered by bars increased in all reaches in the study area the response scaled tightly with the relative amount of bed material sediment transport through individual reaches indicating that the amount of morphological change caused by the flood was conditioned by the simultaneous introduction of a sediment pulse to the channel network copyright 2015 john wiley sons ltd

earthquake induced chains of geologic hazards patterns mechanisms and impacts large earthquakes initiate chains of surface processes that last much longer than the brief moments of strong shaking most moderate and large magnitude earthquakes trigger landslides ranging from small failures in the soil cover to massive devastating rock avalanches some landslides dam rivers and impound lakes which can collapse days to centuries later and flood mountain valleys for hundreds of kilometers downstream landslide deposits on slopes can remobilize during heavy rainfall and evolve into debris flows cracks and fractures can form and widen on mountain crests and flanks promoting increased frequency of landslides that lasts for decades more gradual impacts involve the flushing of excess debris downstream by rivers which can generate bank erosion and floodplain accretion as well as channel avulsions that affect flooding frequency settlements ecosystems and infrastructure ultimately earthquake sequences and their geomorphic consequences alter mountain landscapes over both human and geologic time scales two recent events have attracted intense research into earthquake induced landslides and their consequences the magnitude m 7 6 chi chi taiwan earthquake of 1999 and the m 7 9 wenchuan china earthquake of 2008 using data and insights from these and several other earthquakes we analyze how such events initiate processes that change mountain landscapes highlight research gaps and suggest pathways toward a more complete understanding of the seismic effects on the earth s surface

the importance of earthquake induced landslides to long term slope erosion and slope failure hazards in seismically active regions abstract this paper describes a general method for determining the amount of earthquake induced landsliding that occurs in a seismically active region over time this determination can be used as a quantitative measure of the long term hazard from seismically triggered landslides as well as a measure of the importance of this process to regional slope erosion rates and landscape evolution the method uses data from historical earthquakes to relate total volume of landslide material dislodged by an earthquake to the magnitude m and seismic moment m0 of the earthquake from worldwide data a linear regression relation between landslide volume v and m0 is determined as v m0 1018 9 0 13 where v is measured in m3 and m0 is in dyn cm to determine the amount of earthquake generated landsliding over time this relation is combined with data on seismic moment release for a particular region which may be derived from either earthquake history or fault slip data the form of the m0 v relation allows the rate of production of earthquake induced landslides over time to be determined from total rate of seismic moment release without regard to the distribution of individual events thus simplifying and generalizing the determination application of the method to twelve seismically active regions with areas ranging from 13 275 to 2 308 000 km2 shows that erosion rates from earthquake induced landslides vary significantly from region to region of the regions studied the highest rates were determined for the island of hawaii new zealand western new guinea and the san francisco bay region of california significantly lower rates were determined for iran tibet the sierra nevada great basin region of california and central japan for the time period from 715 ad to the present intermediate rates were determined for peru southern california onshore california turkey and central japan for the time period from 1586 ad to the present to determine the relative long term importance of seismically triggered landslides these erosion rates are compared to erosion rates calculated for other slope processes and to rates calculated from fluvial sediment discharge comparisons with other slope processes indicate that earthquake induced landslides are the predominant agents of slope erosion on the island of hawaii in the san francisco bay region and in western new guinea for hawaii the san francisco bay region and sierra nevada great basin region of california the erosion rates calculated for earthquake induced landslides also exceed the regional erosion rates calculated from fluvial sediment discharge

sediment yield mapping using small dam sedimentation surveys southern tablelands new south wales summary sediment yield estimates from sedimentation surveys of small farm dams are a cost effective method of obtaining long term data suitable for use in catchment management in this study the results of a number of such surveys on the southern tablelands of new south wales are used to derive empirical equations for sediment yield in relation to catchment characteristics the equations are used to estimate the distribution of sediment yield in an adjacent catchment of similar morphology in areas where numerous such dams have been built this approach can be used to derive sediment yield data for a wide variety of terrain and land use types which can then be extrapolated to larger areas for which no data exist

channel bed adjustments following major aggradation in a steep headwater setting findings from oyabu creek kyushu japan abstract a typhoon in 1993 induced major aggradation along oyabu creek a steep gravel bed mountain stream in kyushu japan processes of sediment reworking are inferred from a 7 year monitoring program that measured adjustments to channel cross sections the longitudinal profile and the extent distribution of bedrock outcrops along a 3 km study reach over time the reach adopted a riffle and pool structure with notable increase in the area of exposed bedrock on the bed this adjustment process was characterised by progressive reduction in sediment storage change per unit flow the relaxation pathway following disturbance induced by the typhoon was shaped by the magnitude and frequency of subsequent rainfall events the capacity of these events to transport available sediments and physical linkages between reaches adjacent subreaches demonstrated differing relaxation pathways in response to these influences induced by spatial and temporal variability in threshold conditions along the channel longer term evidence indicates that responses to major disturbance such as the 1993 typhoon occur as cycles of around 20 year duration a relaxation period of 7 years is required to attain a quasi equilibrium bed configuration and rate of sediment flux the timeframe of cycles is considered to reflect changes to hillslope channel bed coupling marking the period required to generate sufficient sediment stores to reactivate phases of aggradation and subsequent degradation

the recent history of erosion and sedimentation on the southern tablelands of southeastern australia sediment flux dominated by channel incision abstract as in other regions colonised from europe within the last few centuries australia s vegetation and soils have been dramatically changed by clearing cropping and grazing in southeastern australia particularly on the southern tablelands the impacts of european settlement are clearly manifested by channel incision by using stratigraphic and documentary evidence in conjunction with aerial photographs sediment budgets for the post settlement period have been constructed to define the fluxes and stores of sediment for each of the major geomorphic components of the 136 km2 catchment of jerrabomberra creek near canberra using these budgets and some plausible assumptions it has been possible to approximate the history of both the sediment delivery ratio and sediment yield for this catchment while the quantities estimated in this analysis are approximations the trends through time are credible sediment yield increased rapidly to a peak after european settlement and has returned to a level between the peak and the pre european value the delivery ratio has followed a similar trend the most general conclusion to emerge is that in this landscape both the total sediment flux and the sediment yield of the catchment have been dominated by channel erosion this result is contrary to the findings in many parts of the world where sheet and rill erosion dominates the fluxes the soil conservation implication of these results is clear to control off site effects of erosion the focus must be on the channels

dynamic environment in the ta chia river watershed after the 1999 taiwan chi chi earthquake abstract the 1999 chi chi earthquake mw 7 6 induced a tremendous number of landslides in central taiwan and about 1 5 million m3 of earth was driven from broken slopes in the ta chia river watershed the impact of this earthquake not only made the geomaterial more fractured but also changed the river morphology of the western foothill area the main purpose of this study was to investigate the dynamic environment of the ta chia river watershed after the 1999 chi chi earthquake the study comprised three major parts a landslide inventory a landslide analysis and a time effect study a conceptual model was developed to investigate the time effect of the earthquake impact on the landslide rainfall correlation the study focused on the major typhoon events after the 1999 chi chi earthquake including toraji 2001 mindulle 2004 and sinlaku 2008

landslides triggered by the 1994 northridge california earthquake abstract the 17 january 1994 northridge california earthquake m w 6 7 triggered more than 11 000 landslides over an area of about 10 000 km 2 most of the landslides were concentrated in a 1000 km 2 area that included the santa susana mountains and the mountains north of the santa clara river valley we mapped landslides triggered by the earthquake in the field and from 1 60 000 nominal scale aerial photography provided by the u s air force and taken the morning of the earthquake these mapped landslides were subsequently digitized and plotted in a gis based format most of the triggered landslides were shallow 1 to 5 m thick highly disrupted falls and slides within weakly cemented tertiary to pleistocene clastic sediment average volumes of these types of landslides were less than 1000 m 3 but many had volumes exceeding 100 000 m 3 the larger disrupted slides commonly had runout paths of more than 50 m and a few traveled as far as 200 m from the bases of steep parent slopes deeper 5 m thick rotational slumps and block slides numbered in the tens to perhaps hundreds a few of which exceeded 100 000 m 3 in volume most of these were reactivations of previously existing landslides the largest single landslide triggered by the earthquake was a rotational slump block slide having a volume of 8 10 6 m 3 analysis of the mapped landslide distribution with respect to variations in 1 landslide susceptibility and 2 strong shaking recorded by hundreds of instruments will form the basis of a seismic landslide hazard analysis of the los angeles area

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

linkage of sediment supply and transport processes in miyagawa dam catchment japan 1 linkages between sediment supply by episodic geomorphic processes obtained from aerial photographs and field surveys and sediment transport estimated from changes in sediment deposition behind a large dam were investigated in the miyagawa dam catchment central japan a total of 6667 landslides were confirmed in the period from 1965 to 2000 on the basis of seven temporal pairs of aerial photographs both the occurrence of landslides and discharge into the dam lake affect sediment yield indicating that fluvial systems in miyagawa dam catchment are supply limited with respect to sediment sediment yields are affected by not only the initial failed volume of landslides but also the mobility of landslides and debris flows in miyagawa dam catchment percentages of landslides reaching channels varied from 56 in 1997 2000 to 75 in 1976 1981 and were correlated with maximum hourly rainfall in addition the mobility of debris flows was higher during periods with high maximum instantaneous discharge compared to lower discharge suggesting that the water content both in initially failed materials and transported sediment controlled their mobility topography also affected the mobility of landslides debris flows for catchments 0 1 km2 the percentage of channel network length impacted by debris flows decreased with increasing catchment area due to reduced channel gradient thus both the magnitude of rainfall runoff events and the catchment topography affect how landslide sediment contributes to sediment yield at the large catchment scale

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

geological and geomorphological characteristics of landslides triggered by the 2004 mid niigta prefecture earthquake in japan abstract the 2004 mid niigta prefecture earthquake mjma 6 8 triggered more than one thousand landslides in the miocene to quaternary sedimentary rocks in japan the most common landslides were shallow disrupted landslides on steep slopes which has been common in many previous disastrous earthquakes in the world the mid niigta prefecture earthquake also triggered more than one hundred deep landslides providing valuable information on the conditions for their occurrence a field investigation and the interpretation of aerial photographs taken before and after the earthquake suggest that reactivation of existing landslides and undercutting of slopes are the most important factors for deep landslides to be triggered by earthquakes in addition planar sliding surfaces seem to be essential for the generation of catastrophic landslides triggered by this earthquake planar bedding parallel sliding surfaces were formed at the boundary between the overlying permeable sandstone and underlying siltstone or along the bedding planes of alternating beds of sandstone and siltstone sliding surfaces along the slope parallel oxidation front were formed in the area of black mudstone new landslides rockslide avalanches occurred with the sliding surfaces in a several cm thick tuff interbedded in siltstone one rockslide avalanche occurred on a slope where buckling deformation preceded the earthquake gentle valley bottom sediments were mobilized in many locations probably because they were saturated and partial liquefaction had occurred due to the earthquake shaking

large quaternary landslides in the central appalachian valley and ridge province near petersburg west virginia abstract geological mapping and photointerpretation of side looking airborne radar images and color infrared aerial photographs reveal two large quaternary landslides in the valley and ridge province of the central appalachians near petersburg w va the elkhorn mountain rock avalanche occurs on the thrust faulted northwestern flank of the elkhorn mountain anticlinorium a minimum of 7 106 m3 of quartzite colluvium was transported more than 3 km from a 91 m high escarpment of silurian tuscarora quartzite the extensively vegetated deposit may owe in part its transport and weathering to periglacial conditions during the pleistocene in contrast the gap mountain rock block slide is a single allochthonous block that is 1 2 km long 0 6 km wide and at least 60 m thick the 43 106 m3 block is composed of limestone of the helderberg group and the oriskany sanstone of early devonian age planar detachment probably occurred along a dissolution bedding plane near the shriver chert and the oriskany sandstone contact failure probably was initiated by downcutting of the south branch potomac river during the pleistocene landslides of this magnitude suggest accelerated erosion during periglacial climates in the pleistocene the recognition of these large slope failures may provide evidence of paleoclimatic conditions and thereby increase our understanding of the geomorphologic development of the valley and ridge province

changes in land cover and shallow landslide activity a case study in the spanish pyrenees the pyrenees like many other mountain areas in europe have experienced depopulation and land abandonment during the 20th century this has encouraged vegetation recovery in formerly occupied areas including reforestation to promote woodland the objective of this study is to analyse the effects of these changes on shallow landsliding a process responsible for erosion and land degradation in many mountain areas a sequence of aerial images reveals a slight decrease in the landslide occurrence rate in the last half of the 20th century and a parallel increase in the landslide extinction rate i e the rate at which evidence of landslide activity is removed by vegetation colonisation a logistic regression routine was used to assess the influence of land use and vegetation recovery in the occurrence of shallow landslides the result shows that the former arable fields on the valley slopes still facilitate landsliding even after land abandonment and revegetation by shrubs or trees a shift in the topographic location of landslides was also detected pointing to an increased importance of water redistribution in the slopes after prolonged rainfall periods

evolution of a sediment wave in an experimental channel the routing of bed material through channels is poorly understood we approach the problem by observing and modeling the fate of a low amplitude sediment wave of poorly sorted sand that we introduced into an experimental channel transporting sediment identical to that of the introduced wave the wave essentially dispersed upstream and downstream without translation although there was inconclusive evidence of translation late in the experiment when the wave was only 10 20 grain diameters high alternate bars migrated through zones of differing bed load transport rate without varying systematically in volume celerity or transport rate sediment that overpassed migrating bars was apparently responsible for dispersion of the wave the evolution of the wave was well predicted by a one dimensional model that contains no adjusted empirical constants numerical experiments demonstrate however that the theory does not predict sediment waves that migrate long distances downstream such waves can only be explained by the following processes not represented by the theory selective bed load transport spatial variations in bar and other form roughness the mechanics of mobile armor and perhaps other mechanisms

the formation and impact of landslide dams state of the art abstract the blocking of river courses by mass movements is very common in mountainous areas with deep and narrow valleys landslide dams may pose serious threats to people and their livelihoods downstream in the case of abrupt dam failure since the publication of benchmark reviews of costa and schuster 1988 and korup 2002 there is a growing number of studies focusing on the formation stability and short term impacts of landslide dams this review combines the insights of all these studies builds on current concepts of landslide dams and suggests ways to unify terminologies and classifications we furthermore present a new worldwide database compiled from literature data it contains 410 landslide dams 1 million m3 in volume that were formed since 1900 since these have the most complete data entries these data show that dam longevity is among other factors correlated with the type of landslide forming the dam those formed by rock debris avalanches and rockslides have longest lifespans however the influence of landslide type or material on dam longevity decreases with time after dam formation to ensure consistency in the next database generation we suggest guidelines for data collection to provide a solid basis for evaluating dam stability and governing factors a preliminary classification matrix for landslide dam stability that combines topographic setting and the internal structure of the dam body is another outcome of our review furthermore an evaluation of the various geomorphic stability indices proposed in the literature regarding their suitability and limitations in assessing dam formation and stability shows that they predict the probability of dam formation reasonably well but that their application to longevity estimates requires further assessment the geomorphic impacts of landslide dams in the short medium and long term are summarized and illustrated with key examples finally for a better understanding of the factors controlling dam stability we recommend to 1 include dam composition and sedimentary structures in future case studies 2 maintain and update the worldwide database for sound statistical analyses 3 refine landslide dam stability indices and test them for different landslide types and 4 study hazard cascades related to multiple dams in one watershed for long term landscape evolution studies we suggest to 5 quantify terrestrial sediment flux related to landslide dams 6 detect ancient landslide dams in river profiles and 7 further exploit the sediment archives in former impoundment areas

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

a statistical model for the impact of the 1999 chi chi earthquake on the subsequent rainfall induced landslides a statistical model is proposed for the temporal impact of the 1999 chi chi earthquake on the subsequent rainfall induced new landslides in the choushui river watershed of central taiwan based on daily precipitation records from 1996 to 2008 and the landslide inventories obtained from satellite images taken in this period the parameters of the model functions were obtained by genetic algorithm the proposed model estimates new landslide density from daily precipitation with an average error of 13 91 to the variation analysis result from landslide inventory over 15 image dates the model estimation reveals a continuously decaying pattern of earthquake impact on the subsequent rainfall induced new landslides an average daily 0 004 background new landslide density and a 4 97 new landslide density caused by the earthquake directly within the study area also the model suggests that there are impacts and latency of antecedent precipitation among the occurrence of new landslides

channel response to sediment wave propagation and movement redwood creek california usa redwood creek north coastal californa usa has experienced dramatic changes in channel confguation since the 1950s a series of large floods in 1955 1964 1972 and 1975 combined with the advent of widespread commercial timber harvest and road building resulted in extensive erosion in the basin and contributed high sediment loads to redwood creek since 1975 no peak flows have exceeded a 5 year recurrence interval twenty years of cross sectional survey data document the downstream movement of a sediment wave in the lower 26 km of this gravel bedded river at a rate of 800 to 1600 m a i durng this period of moderately low flows higher transit rates are associated with reaches of higher unit stream power the wave was initially deposited at a site with an abrupt decrease in channel gradient and increase in channel width the amplitude of the wave has attenuated more than i m as it moved downstream and the duration of the wave increased from eight years upstream to more than 20 years downstream channel aggradation and subsequent degradation have been accommodated across the entire channel bed channel width has not decreased significantly after initial channel widening from large 25 year recurrence interval floods three sets of longitudinal surveys of the streambed showed the highest increase in pool depths and frequency in a degrading reach but even the aggrading reach exhbited some pool development through time the aggraded channel bed switched from functioning as a sediment sink to a significant sediment source as the channel adjusted to high sediment loads from 1980 to 1990 sediment eroded from temporary channel storage represented about 25 per cent ofthe total sediment load and 95 per cent of the bedload exported from the basin

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

recent rainfall induced landslides and debris flow in northern taiwan this paper discusses the factors initiating landslides and a large scale debris flow in the chonho area of taipei county northern taiwan which resulted from heavy rainfall during typhoon xangsane in november 2000 the morphology and triggering mechanism of the landslides and the debris flow were investigated using aerial photographs taken over the past 20 years field measurement of channel cross sections laboratory assessment of slope material properties and slope stability analysis a large landslide that occurred in the source area was the initial source of material for the debris flow the majority of the landslide debris entered the main stream where it mixed with water and became a debris flow eroding the sidewalls of the stream the debris flow entrained additional material and traveled downstream into chonho village our findings indicate that the november 2000 landslides and the debris flow were strongly influenced by the physical properties of the underlying pyroclastic substrate and the pattern of bedrock discontinuities within the valleys

a long term estimate of bedload and suspended sediment yield derived from reservoir deposits abstract the draw down of pinmacher reservoir ayrshire west scotland in 1988 exposed sedimentary sequences entrapped since impoundment in 1903 the sole surface influent an ungauged second order stream drains a mainly undisturbed upland catchment most of the floor of the small basin is coated with mud however below the inflow a normally subaqueous delta of gravelly sand has accumulated examination of sections has enabled the construction of an isopachyte map from which the volume of deposits has been evaluated taking account of trap efficiency sediment water content and bulk densities the total sediment yield from the pinmacher catchment is 51 1 t km 2 year 1 on the assumption that the deltaic and lacustrine sequences respectively represent the bed and suspended fractions of the influent stream load long term 85 years average yields for the two components of 23 3 t km 2 year 1 and 27 8 t km 2 year 1 may be discriminated thus bedload accounts for ca 46 of the total load whilst the quantification of long term bedload transport remains elusive this study provides an unusually long record moreover analysis of the delta stratigraphy demonstrates two major and 21 additional flood events during the history of impoundment

can low magnitude earthquakes act as a triggering factor for landslide activity examples from the western carpathian mts poland abstract there are numerous examples of the impact of strong earthquakes on landslide activity there is however very little information about the ability of low magnitude earthquakes m

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

effects of entrainment phenomenon on the rapid and long runout movement of landslides in wenjia gully sichuan china as a common phenomenon in landslides entrainment of loose bed material along the sliding path can enhance both the volume and mobility of the sliding mass posing a great threat to the life and property safety of people in the affected area for the purpose of revealing the mechanism of entrainment phenomenon of sliding material in the runout process a dynamic slice based model was firstly proposed in the present study in this model the motion of landslide body is assumed to follow the rheological law proposed by voellmy additionally through voellmy model the increase in kinetic energy mass and volume of landslide body and entrainment depth caused by the entrainment phenomenon were taken into consideration subsequently on the basis of the dynamic slice based model back analyses were performed on the wenjia gully landslide the effect of entrainment phenomenon on the post failure motion was analyzed the calculated results shows that the travel distance obtained from proposed model is closer to field data than that resulted from scheidegger s empirical method moreover the peak value of the maximum velocity calculated by this model is in good agreement with that get from the dynamic analysis model dan3d when considering the entrainment phenomenon the volume of sliding mass increases greatly in post failure motion this paper provides a new method for analyzing the entrainment phenomenon in landslide motion

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

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

composition and sources of atmospheric dusts in snow at 3200 meters in the st elias range southeastern alaska usa abstract dusts in snow from the accumulation zone in the st elias range appear from their chemical compositions to have come from terranes of rocks of ferromagnesian composition these dusts with respect to their composition and to the moderate degree of variation that occurs through a depositional year are similar those deposited in greenland the high portion of the st elias range is isolated from dominance by any local dust source terranes because of altitude and the extent of the surrounding glacierized and snow covered region in greenland the altitude is typically lower but local sources are even less likely to dominate the character of the dusts deposited into the ice record there the similar compositions and moderate compositional variations of dusts from these two places bear on the question of whether the dusts that are transported over long distances by the atmosphere under modern and glacial period conditions are uniform and representative of a broad regional or even hemispheric background dust the dusts in the snow were measured by means of a suite of major minor and trace rock forming metals chosen to give information about rock types their constituent minerals degree of degradation weathering and energies of atmospheric uptake from source the variations in amounts of rock dust through the year in the st elias range snowpack have no time stratigraphic correspondence to the also large variations in concentrations of other species that are not constituents of rock derived dusts such the anions chloride sulfate and nitrate the highs and lows of the two types of materials are apparently completely independent the structure revealed by the moderately fine scale sampling of the present study 10 increments y serves as a background for the interpretation of analysis of ice core samples in which annual layers may be too compressed to permit analysis of sub annual samples

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

blanket peat erosion and sediment yield in an upland reservoir catchment in the southern pennines uk this paper investigates temporal variations in fluxes of peat and other sediment in the catchment of march haigh reservoir west yorkshire long term estimates of sediment yield were derived from a study of reservoir sediments magnetic properties were used to correlate ten cores to a master profile dated using 210pb and 137cs a 14c date suggests that most of the organic component of the sediment is allochthonous and derived from peat eroded from the catchment organic sediment yields suggest low catchment erosion rates between 1838 and 1963 blanket peat erosion increased significantly after 1963 and peaked between 1976 and 1984 estimates of total sediment yield range between 2 and 28 t km 2 a 1 these yields are significantly lower than those from some previous studies examining reservoir sedimentation in other blanket peat covered catchments the low yield estimates may be due to relatively low rates of erosion in the basin but may also be partly explained by maintenance of silt traps during the early life of the reservoir and removal of sediment by scouring sedimentation within the reservoir is spatially variable and bathymetry and sediment source appear to be the dominant controls on sedimentation patterns within the reservoir

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

earthquake triggered increase in sediment delivery from an active mountain belt in tectonically active mountain belts earthquake triggered landslides deliver large amounts of sediment to rivers we quantify the geomorphic impact of the 1999 mw 7 6 chi chi earthquake in taiwan which triggered 20 000 landslides coseismic weakening of substrate material caused increased landsliding during subsequent typhoons most coseismic landslides remained confined to hillslopes downslope transport of sediment into the channel network occurred during later storms the sequential processes have led to a factor of four increase in unit sediment concentration in rivers draining the epicentral area and increased the magnitude and frequency of hyperpycnal sediment delivery to the ocean four years after the earthquake rates of hillslope mass wasting remain elevated in the epicentral area

dynamics of a complex mass movement triggered by heavy rainfall a case study from nw turkey abstract following a period of heavy precipitation a large and complex mass movement namely the dagkoy landslide occurred in the west black sea region of turkey on may 21 1998 this paper describes the conditioning factors of the landslide and interprets the mass transport processes in terms of a movement scenario geology geomorphology and vegetation cover were considered as the conditioning factors of the failure observations showed that the gently sloping about 10 area is mostly covered by dense forest trees at the crown where the motion initiated significant intersection of the collapsed slope with dip of the local marls seems to have contributed to the formation and geometry of the landslide the distance from the crown down to the toe of the landslide measured more than 600 m with about 0 6 km 3 total earth material displaced the landslide has both a block sliding characteristics in the upper portions and a debris flow soil flow component around the margins of the sliding blocks in the middle parts and at the toe the proposed scenario for the landslide reveals that the movement was initiated near crown as a result of the excess water content in the marls at the end of 3 days of heavy rainfall the early perturbations transverse cracks ridges etc lasted for 6 7 h after which the central part of the zone started to move as a soil flow in which very large intact blocks were transported even though the movement was very rapid 1 2 m min there was no loss of life however the movement destroyed 38 houses one mosque and a considerable amount of farmland

large rock avalanches triggered by the m 7 9 denali fault alaska earthquake of 3 november 2002 the moment magnitude m 7 9 denali fault alaska earthquake of 3 november 2002 triggered thousands of landslides primarily rock falls and rock slides that ranged in volume from rock falls of a few cubic meters to rock avalanches having volumes as great as 20 10 6 m 3 the pattern of landsliding was unusual the number and concentration of triggered slides was much less than expected for an earthquake of this magnitude and the landslides were concentrated in a narrow zone about 30 km wide that straddled the fault rupture zone over its entire 300 km length despite the overall sparse landslide concentration the earthquake triggered several large rock avalanches that clustered along the western third of the rupture zone where acceleration levels and ground shaking frequencies are thought to have been the highest inferences about near field strong shaking characteristics drawn from interpretation of the landslide distribution are strikingly consistent with results of recent inversion modeling that indicate that high frequency energy generation was greatest in the western part of the fault rupture zone and decreased markedly to the east d 2005 elsevier b v all rights reserved

geological and morphological study of the jiufengershan landslide triggered by the chi chi taiwan earthquake the jiufengershan rock and soil avalanche is one of the largest landslides triggered by the chi chi earthquake taiwan 1999 the landslide destabilized the western limb of the taanshan syncline along a weak stratigraphic layer it involved a flatiron remnant which was almost entirely mobilized during the earthquake the avalanche was slowed down by ns trending ridges located downstream along the jiutsaihu creek the landslide affected a 60 m thick and 1 5 km long sedimentary pile composed of shales and sandstones which dip 228se toward a transverse valley the triggering mechanism and the sliding process were analyzed by means of geological and morphological data from aerial photographs and observed in the field a high resolution airborne light detection and ranging lidar image taken 2 5 years after the landslide allows the identification of morphological structures along the sliding surface and the landslide accumulation the sliding surface shows several deformation structures such as fault scarps and folds these structures are interpreted in terms of basal shear stresses created during the avalanche three major joint sets were identified at the sliding surface the isopach map of the landslide was calculated from the comparison between elevation models before and after the earthquake the coseismic volume of mobilized material and landslide deposit data are 4210 6 m 3 and 5010 6 m 3 respectively the geometry of the landslide accumulation in the field has an irregular star shape the morphology of the deposit area shows a sequence of smooth reliefs and depressions that contrast with the neighboring ridges d 2005 elsevier b v all rights reserved

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

some analytical methods for converting thermochronometric age to erosion rate 1 an analytical method is presented for converting thermochronometric ages to surface erosion or equivalently exhumation rate the method incorporates the two most important thermal processes during cooling by erosion the dependence of closure temperature on cooling rate and the advection of heat by rock motion toward the earth s surface two thermal models are considered 1 a steady state model valid for low erosion rates and 2 an eroding half space model which has no steady state but captures the transient increase of geothermal gradient with erosion in each case it is assumed that data consist of one or more thermochronometric ages present day surface geothermal gradient and topographic information including the elevation at which the age was obtained analytical solutions are provided to derive the erosion rate from these data either as an explicit expression for the steady case or as a root finding problem for the transient case a graphical method for plotting age against erosion rate and geothermal gradient is presented as a method for solving the root finding problem and for tracking analytical errors in observations of age and surface geothermal gradient the graphical method is also appropriate for comparing data from different elevations or from different thermochronometric systems examples are provided using synthetic data or published data from the literature

frequency and spatial distribution of landslides in a mountainous drainage basin western foothills taiwan maps from 1904 and 1915 and air photographs from 1963 1980 1985 1993 and 1996 provide a record of landslide incidence in a 92 1 km2 drainage basin a headwater tributary of the cho shui river in taiwan interpretation of landslide patterns from the early maps indicate that in four sub basins 36 km2 structural geological factors control chronic landsliding regularly reactivated by intense rains within these four sub basins all later air photographs reveal a continuing high incidence of landslides with landslide densities of 3 11 ha km2 air photographs taken in 1963 following extensive logging in 1985 following highway construction and in 1996 following the very large typhoon herb event demonstrate the short term effects of disturbance in these structurally weak sub basins air photographs from 1980 and 1993 demonstrate recovery of the land surface from logging and highway construction impacts respectively for the adjacent sub basins 56 km2 two modes of response to perturbations were identified six sub basins 48 km2 showed direct response to logging road construction and typhoon herb and five sub basins 8 km2 were more buffered and showed some lagged responses even this last category of sub basins is more active than the average for taiwan where the mean landslide density is 0 84 ha km2 it is proposed that for the 92 1 km2 hoshe basin the formative event sensu brunsden z geomorphol suppl 79 1990 1 is one that produces approximately 200 ha of landslides a value that has been equaled or exceeded in each of the periods of study 1963 1980 1980 1985 1985 1993 and 1993 1996 logging activity major road construction and extreme typhoon and earthquake events produce short term acceleration of landslide incidence in principle recovery rates of the land from pulsed perturbations of about 20 years for logging activity and about 8 years for major road construction may also be suggested

decadal vegetation succession from modis reveals the spatio temporal evolution of post seismic landsliding after the 2008 wenchuan earthquake abstract strong earthquakes especially in continental mountainous areas can trigger extensive mass wasting producing large amounts of debris that accumulates along the hillslopes or in drainage channels the coseismic deposits and disturbed slopes are prone to be reactivated or remobilized by heavy rainfalls in the subsequent years after the earthquake predicting how long post seismic landslide activity will return to the pre earthquake level is a key to risk assessment and management however this is still poorly understood and lacks quantitative prediction approach the 2008 wenchuan earthquake triggered an unprecedented number of landslides creating an extraordinary natural laboratory to investigate the evolution of post seismic landslides and their impacts on environment using the vegetation recovery rate as an indicator we present the observational evidence of the post seismic landslide evolution based on modis ndvi time series between 2000 and 2018 using a simple vegetation recovery rate vrr function we quantify the rate of vegetation regrowth in the wenchuan earthquake affected area and discuss the decaying trend of post seismic landslide activities our findings show that 83 of the co seismic landslides become inactive within a decade the ndvi trend suggests that landslide activity may return to the pre earthquake level within 18 years the sensitivity of vegetation regrowth to post seismic landsliding thus offers a great potential to improve our understanding of the spatio temporal evolution of the post seismic landslide activities

repeated catastrophic valley infill following medieval earthquakes in the nepal himalaya geomorphic footprints of past large himalayan earthquakes are elusive although they are urgently needed for gauging and predicting recovery times of seismically perturbed mountain landscapes we present evidence of catastrophic valley infill following at least three medieval earthquakes in the nepal himalaya radiocarbon dates from peat beds plant macrofossils and humic silts in fine grained tributary sediments near pokhara nepal s second largest city match the timing of nearby m 8 earthquakes in 1100 1255 and 1344 c e the upstream dip of tributary valley fills and x ray fluorescence spectrometry of their provenance rule out local sources instead geomorphic and sedimentary evidence is consistent with catastrophic fluvial aggradation and debris flows that had plugged several tributaries with tens of meters of calcareous sediment from a higher himalayan source 60 kilometers away

exploring the effects of seismicity on landslides and catchment sediment yield an italian case study abstract recent studies showed that contemporary average catchment sediment yields sy t km 2 y 1 at regional and continental scales are often strongly correlated to spatial patterns of seismic activity nonetheless we currently have little insights into the mechanisms that explain these correlations we investigated how spatial patterns of sy in italy are linked to patterns of seismic activity for a dataset of 103 italian catchments with average sy measured over a period of years to decades we extracted tectonic and none tectonic variables that potentially explain observed differences in sy these include proxies for vertical uplift rates and cumulative seismic moments csm associated with historic earthquakes of different ranges of magnitude results showed that also across italy sy is significantly correlated to seismicity however sy showed much stronger correlations with proxies of seismicity relating to small but frequent earthquakes 2 m w m w 4 analyses of a dataset of about 500 000 landslides across italy showed very comparable trends spatial patterns of landslides within similar lithological units generally show a significant positive correlation with csm of weak but frequent seismicity and generally not with csm of large earthquakes these results suggest that on a decadal time scale and at a regional continental spatial scale frequent but relatively weak seismicity may exert a more important geomorphic impact than large earthquake events or tectonic uplift

disaster chains initiated by the wenchuan earthquake the wenchuan earthquake caused numerous landslides and avalanches which initiated causal chains of geological and ecological disasters field investigations and field experiments were performed in the earthquake area in 2008 and 2009 to study the disaster chains four types of disaster chains have been identified and seven cases have been studied in the disaster chains each episode was caused by the previous episode or the causal episode in the first chain landslide created a quake lake which was followed by landslide dam failure flood and very intensive fluvial process the last episode of the chain was loss of habitats and destruction of aquatic biocommunities the tangjiashan and huoshigou landslides initiated such a type of disaster chain the second chain consisted of landslide drainage system burying debris flows and development of new drainage system and intensive fluvial process the wenjiagou landslide initiated such a type of disaster chain the third chain consisted of avalanches grain erosion unusual erosion of bare rocks due to insolation and temperature change slope debris flows and flying stones many such disaster chain events occurred on the mountains by the minjiang river section from yingxiu to wenchuan the fourth chain has only two episodes avalanches during the earthquake occurring on elevation between 100 and 800 m from the riverbed and rock falls or new avalanches due to increased slope angle of high mountains 400 1 500 m from the riverbed the chediguan bridge was broken by such avalanches in july 2009 in which six were killed and more than 20 were injured for all the disaster chains the volume of mass movement in each episode was much less than the causal episode previous episode in other words there was an attenuation along the causal chains the attenuation factor is defined as the ratio of the volume of mass movement or affected area in one episode of a chain to the volume or affected area in the causal episode the study concluded that the attenuation factor ranges from 0 02 to 0 3 macroinvertebrates were used as indicator species to evaluate the ecological effect of the disaster chains the number of species was greatly reduced by the causal chains although the river section was not directly affected by landslides

study on coseismic and postseismic crustal movements associated with the 1923 kanto earthquake abstract the kanto earthquake of 1923 m 7 9 occurred in the southern part of the kanto district japan this earthquake was accompanied by the transient crustal movements which follow instantaneous elastic deformations at the time of faulting the coseismic and postseismic crustal movements associated with the kanto earthquake are well interpreted by a dislocation source model in a composite medium which consists of an elastic surface layer lithosphere an intervening maxwellian viscoelastic layer asthenosphere and an elastic substratum an optimum fault model of the kanto earthquake is obtained from the coseismic crustal movements by using a method of inversion analysis in which effects of systematic errors caused by the movements of reference points in geodetic measurement are taken into account it is found that the fault motion of this earthquake is a reverse right lateral slip of 4 8 m with a slip angle of 140 on a fault plane which dips 25 towards n24 e where the slip angle is measured counterclockwise from the fault strike the fault length the fault width and the depth to the upper fault edge are determined as 95 km 54 km and 2 0 km respectively the postseismic transient crustal movements are considered to be controlled by a quasi static relaxation process of stress changes due to faulting in the earth s asthenosphere in such a quasi static problem the surface motion caused by a dislocation source consists of instantaneous elastic deformation at the time of faulting and transient viscoelastic movement after the event the viscoelastic part of the surface displacement field is calculated for the optimum fault model in a three layered composite medium with an intervening viscoelastic layer and compared with the observed data the transient crustal movements after the kanto earthquake are adequately explained by the present model taking the thickness of the lithosphere as 60 km and the thickness and viscosity of the asthenosphere as 180 km and 1020 poise respectively