large amplitude mountain waves in the mesosphere observed on 21 june 2014 during deepwave 1 wave development scales momentum fluxes and environmental sensitivity

the climatology of zonal wave numbers 1 and 2 planetary wave structure in the mlt using a chain of northern hemisphere superdarn radars the zonal wave components 1 and 2 were extracted from the meridional wind along the latitude band of 51 66 n for the years 2000 2008 using eight super dual auroral radar network superdarn radars spanning longitudes from 25 e to 150 w each extracted zonal component represents the superposition of all temporal periods with that zonal structure and indicates the total planetary wave energy available with that wave number the hovmoller diagrams show stationary as well as eastward and westward traveling planetary waves propagating in the background wind the method used to detect the zonal planetary wave components in the superdarn data are detailed and validated using uk meteorological office data which allows the evolution of s1 and s2 planetary wave energy between the stratosphere and mesosphere to be assessed the climatology of zonal wave number 1 and 2 planetary wave activity in the mesosphere lower thermosphere mlt is presented and compared to the activity in the stratosphere the mlt climatology of the mean wind anomalies shows stronger planetary wave activity during winter and weaker activity during summer with enhancement around midsummer and autumn equinox the climatology of the mean wind displays similar amplitudes apart from very strong s1 planetary wave amplitudes during summer in addition planetary wave activity during winters with major and minor stratospheric warming events are examined and contrasted

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

river damming late quaternary rockslides in the otz valley region tyrol austria abstract the otz valley and adjacent regions in tyrol austria have been repeatedly affected by large rockslope failures following deglaciation six rockslides each over 107 m3 in volume were emplaced into the otz and inn valleys five of which formed persistent rockslide dams even though catastrophic rockslope failures are short lived events commonly minutes they can have long lasting impacts on the landscape for example large fans have built in the otz valley and knickpoints persist at the former dam sites even though the otz river has eroded through the deposits during the past thousands of years exact age constraints of rockslide dam failure however are still scarce empirical geomorphic stability indices from the literature successfully identified the least and the most stable dams of this group whereas the rest remain inconclusive with some indices variably placing the dams in the stable unstable and uncertain categories this shows a that further index calibrations and b better age constraints on dam formation and failure are needed and c that the exact processes of dam failure are not always trivial to pinpoint for ancient partially breached dams this study is a contribution towards better constraining the nature and landscape impact of dam formation following large rockslope failures

prediction of the behaviour of landslide dams using a geomorphological dimensionless index landslide dams are a common phenomenon they form when a landslide reaches the bottom of a river valley causing a blockage the first effect of such a dam is the infilling of a lake that inundates the areas upstream while the possibility of a sudden dam collapse with a rapid release of the impounded waters poses a higher flood risk to the downstream areas the results of the main inventories carried out to date on landslide dams have been examined to determine criteria for forecasting landslide dam evolution with particular emphasis on the assessment of dam stability not all landslides result in the blockage of a river channel this only occurs with ones that can move a large amount of material with moderate or high velocities in most cases these landslides are triggered by rainfall events or high magnitude earthquakes a relationship also exists between the volume of the displaced material and the landslide dam stability several authors have proposed that landslide dam behaviour can be forecast by defining various geomorphological indexes that result from the combination of variables identifying both the dam and the dammed river channel further developments of this geomorphological approach are presented in this paper by the definition of a dimensionless blockage index starting with an analysis of 84 episodes selected worldwide it proved to be a useful tool for making accurate predictions concerning the fate of a landslide dam copyright 2002 john wiley sons ltd

magma reflection imaging in krafla iceland using microearthquake sources the details of magma plumbing beneath active volcanoes remain a major challenge in geochemistry geophysics and volcanic hazard evaluation here we apply a relatively novel variation of seismic interferometry which we call virtual reflection seismic profiling vrsp to produce a high resolution image of a known crustal magma body the technique takes advantage of recent advances in both seismic instrumentation dense arrays and seismic analysis seismic interferometry we have applied this technique to data recently acquired at an iconic volcanic system krafla which lies on the mid atlantic ridge as exposed in northern iceland what make this particular site exceptional are encounters with rhyolitic magma in two drillholes k 39 and iceland deep drilling project 1 iddp 1 these known magma bodies represent a unique calibration opportunity for surface geophysical measurements of magma distribution at depth in this study we produced a stacked seismic reflection section by applying common depth point processing techniques to virtual shot gathers derived from interferometry of p waves from microearthquakes generated by tectonic magmatic and or geothermal activity we observe a strong coherent reflection on the seismic section at a travel time corresponding to the depth at which magma was encountered in the iddp 1 wellbore we interpret this reflection to be from magma or magma related fluids additional coherent reflections may correspond to other components of the magma plumbing beneath krafla these results represent a promising new technique for structural imaging with natural sources that can be applied to a wide array of geologic and energy problems that involve natural or induced seismic clusters

osl dating of the massive landslide damming event in the jishixia gorge on the upper yellow river ne tibetan plateau frequent natural hazards cause huge damage to human life and society in the mountainous regions along the eastern rim of the tibetan plateau a massive landslide damming event has been reported in

catchment response to lava damming integrating field observation geochronology and landscape evolution modelling combining field reconstruction and landscape evolution modelling can be useful to investigate the relative role of different drivers on catchment response the geren catchment 45 km2 in western turkey is suitable for such a study as it has been influenced by uplift climate change and lava damming four middle pleistocene lava flows 40ar 39ar dated from 310 to 175 ka filled and dammed the gediz river at the gediz geren confluence resulting in base level fluctuations of the otherwise uplift driven incising river field reconstruction and luminescence dating suggest fluvial terraces in the geren catchment are capped by middle pleistocene aggradational fills this showed that incision of the geren trunk stream has been delayed until the end of mis 5 subsequently the catchment has responded to base level lowering since mis 4 by 30 m of stepped net incision field reconstruction left us with uncertainty on the main drivers of terrace formation therefore we used landscape evolution modelling to investigate catchment response to three scenarios of base level change i uplift with climate change rainfall and vegetation based on arboreal pollen ii uplift climate change and short lived damming events iii uplift climate and long lived damming events outputs were evaluated for erosion aggradation evolution in trunk streams at two different distances from the catchment outlet climate influences erosion aggradation activity in the catchment although internal feedbacks influence timing and magnitude furthermore lava damming events partly control if and where these climate driven aggradations occur damming thus leaves a legacy on current landscape evolution catchment response to long duration damming events corresponds best with field reconstruction and dating the combination of climate and base level explains a significant part of the landscape evolution history of the geren catchment by combining model results with fieldwork additional conclusions on landscape evolution could be drawn

the internal structure of a rockslide dam induced by the 2008 wenchuan mw7 9 earthquake china abstract the internal structure of landslide dams plays a key role in their stability however it has not been much studied probably due to the difficulty in obtaining information on internal structure in most cases here we examined the shear wave velocity structure of a rockslide dam by a surface wave technique called multichannel analysis of surface waves masw during the 2008 wenchuan earthquake m w 7 9 more than 60 000 landslides were triggered and 800 landslide dams formed those dams with a high risk of collapse threatened rescue activities and almost all of the large landslide dams were treated by digging a sluiceway immediately after the earthquake although the risk of collapse of many landslide dams was removed or lowered not all of the countermeasures were based on well controlled methods to analyze the internal of landslide dams to assist in carrying out reliable countermeasures we made detailed investigations on some of the dams and here describe one landslide dam that occurred in the tianchi area grain size analysis revealed that the displaced landslide materials experienced fragmentation and segregation during the long movement the shear wave velocity profile of the dam revealed that the dam consisted of three facies carapace body and basal facies the boundary between facies is distinct the body facies had a greater shear wave velocity compared to those landside dams that had suffered collapse failure during the construction of a sluiceway showing that the dam consisted of more densely deposited materials this kind of dam body had a lower permeability capable of retarding seepage that triggers collapse failure of the dam body due to piping big blocks on the surface also enabled the dam body to have greater resistance to overflow and thus reducing possible collapse failure in the immediate aftermath of overtopping

300 mw baspa ii india s largest private hydroelectric facility on top of a rock avalanche dammed palaeo lake nw himalaya regional geology tectonic setting and seismicity article i nfo this study aims for the characterization of the geological setting of 300 mw baspa ii india s largest private hydroelectric facility which was built on top of a relict rock avalanche dammed palaeo lake baspa valley nw himalaya geologically the hydroelectric installation is located in the higher himalayan crystalline just above the active karcham normal fault which is reactivating the early miocene main central thrust one of the principal himalayan faults the area is seismically active and mass movements are common at ca 8200 yr bp the baspa river was blocked behind a 142 10

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

analysis of landslide dams induced by the 2008 wenchuan earthquake abstract landslide dams caused by earthquakes are extremely hazardous disruptions of the flow of water and sediment in mountain rivers capable of delivering large outburst floods that may devastate downstream areas we analyzed a unique inventory of 828 landslide dams triggered by the m w 7 9 2008 wenchuan tectonic earthquake china constituting 1 4 of the 60 000 coseismic slope failures mapped and attributed to this event while 501 landslides blocked the rivers completely the remainder caused only partial damming or channel diversion the spatial distribution of landslide dams follows the same trend of that of the total landslide distribution with landslide dams being most abundant in the steep watersheds of the hanging wall of the yingxiu beichuan thrust fault and in the northeastern part of the strike slip fault near qingchuan besides the co seismic landslide density the river width also played a key role in determining the landslide dam formation narrow rivers are more prone to be dammed than the wide rivers the correlation between river width and landslide dam volume follows a linear relation which can be used to roughly estimate the dam formation possibility however the applicability of this correlation needs to be validated in other regions the decay failure rate of dams defined here as the percentage of the number and area of landslide dams that have failed over time shows that 25 of dams accounting for 30 of total landslide dam area failed one week after the earthquake these percentages increased to 60 within 1 month and to 90 within 1 year the geomorphometric parameters were analyzed revealing power law relations between landslide area and dam width landslide source area and dam area as well as lake area and lake volume the inventory presented in this study will enrich the worldwide earthquake induced landslide dam database and will also contribute to a better understanding of the post earthquake dam decay

discriminant analysis of the geomorphic characteristics and stability of landslide dams article i nfo landslides can cause the formation of dams but these dams often fail soon after lake formation thus rapidly evaluating the stability of a landslide dam is crucial for effective hazard mitigation this study utilizes discriminant analysis based on a japanese dataset consisting of 43 well documented landslide dams to determine the significant variables including log transformed peak flow or catchment area and log transformed dam height width and length in hierarchical order which affect the stability of a landslide dam the high overall prediction power 88 4 of the 43 training cases are correctly classified and the high cross validation accuracy 86 demonstrate the robustness of the proposed discriminant models phwl with variables including log transformed peak flow and log transformed dam height width and length and ahwl with variables including log transformed catchment area and log transformed dam height width and length compared to a previously proposed dbi index based graphic approach the discriminant model ahv which uses the log transformed catchment area dam height and dam volume as relevant variables shows better ability to evaluate the stability of landslide dams although these discriminant models are established using a japanese dataset only the present multivariate statistical approach can be applied for an expanded dataset without any difficulty when more completely documented worldwide landslide dam data are available

application and evaluation of a rapid response earthquake triggered landslide model to the 25 april 2015 mw 7 8 gorkha earthquake nepal abstract the 25 april 2015 m w 7 8 gorkha earthquake produced strong ground motions across an approximately 250 km by 100 km swath in central nepal to assist disaster response activities we modified an existing earthquake triggered landslide model based on a newmark sliding block analysis to estimate the extent and intensity of landsliding and landslide dam hazard landslide hazard maps were produced using shuttle radar topography mission srtm digital topography peak ground acceleration pga information from the u s geological survey usgs shakemap program and assumptions about the regional rock strength based on end member values from previous studies the instrumental record of seismicity in nepal is poor so pga estimates were based on empirical ground motion prediction equations gmpes constrained by teleseismic data and felt reports we demonstrate a non linear dependence of modeled landsliding on aggregate rock strength where the number of landslides decreases exponentially with increasing rock strength model estimates are less sensitive to pga at steep slopes 60 compared to moderate slopes 30 60 we compare forward model results to an inventory of landslides triggered by the gorkha earthquake we show that moderate rock strength inputs over estimate landsliding in regions beyond the main slip patch which may in part be related to poorly constrained pga estimates for this event at far distances from the source area directly above the main slip patch however the moderate strength model accurately estimates the total number of landslides within the resolution of the model landslides 0 0162 km 2 observed n 2214 modeled n 2987 but the pattern of landsliding differs from observations this discrepancy is likely due to the unaccounted for effects of variable material strength and local topographic amplification of strong ground motion as well as other simplifying assumptions about source characteristics and their relationship to landsliding

frequency and hazard of large rock avalanches in the central southern alps new zealand forty two rock avalanche deposits with volumes ranging from a chosen lower threshold of 1 10 6 m 3 up to 500 10 6 m 3 have been identified in a 10 000 km 2 area of the central southern alps new zealand the observed frequency of one per 244 yr over 10 250 yr is biased by erosion a nearly complete sample of the past 1 700 yr indicates a frequency of 1 per 94 yr on the average the largest rock avalanche in any century is 56 10 6 m 3 and in any millennium 103 10 6 m 3 at about one per century most large rock avalanches are probably triggered by large earthquakes and only a few by large storms the risk of rock avalanche debris reaching a specified distance from a source of known elevation is given by a simple stochastic model locally calibrated to assess rock avalanche hazard

effect of slope failures on river network pattern a river piracy case study from the flysch belt of the outer western carpathians abstract landslides are important geomorphic agents in various mountainous settings we document here a case of river piracy from the upper part of the mala brodska valley in the vsetinske mts czech republic raca unit of the flysch magura group of nappes flysch belt of the outer western carpathians controlled by mass movement processes based on the field geological geomorphological and geophysical data we found out that the landslide accumulations pushed the more active river of out of two subparallel river channels with different erosion activity westwards and forced intensive lateral erosion towards the recently abandoned valley apart from the landslide processes the presence of the n striking fault accentuated by higher flow rates of the eastern channel as a result of its larger catchment area were the most critical factors of the river piracy as a consequence of the river piracy intensive retrograde erosion in the elbow of capture and also within the upper portion of the western catchment occurred deposits of two landslide dams document recent minimum erosion rates to be 18 8 mm ky 1 in the western captured catchment and 3 6 mm ky 1 in the eastern catchment respectively the maximum age of the river piracy is estimated to be of the late glacial and or the early holocene

gravity wave induced anomalous potential vorticity gradient generating planetary waves in the winter mesosphere abstractthis study shows that gravity wave gw forcing gwf plays a crucial role in the barotropic baroclinic instability that is frequently observed in the mesosphere and considered an origin of planetary waves pws such as quasi 2 day and quasi 4 day waves simulation data from a gw resolving general circulation model were analyzed focusing on the winter northern hemisphere where pws are active the unstable field is characterized by a significant potential vorticity pv maximum with an anomalous latitudinal gradient at higher latitudes that suddenly appears in the midlatitudes of the upper mesosphere this pv maximum is attributed to an enhanced static stability that develops through the following two processes 1 strong pws from the troposphere break in the middle stratosphere causing a poleward and downward shift of the westerly jet to higher latitudes and 2 strong gwf located above the jet simultaneously shifts and forms an upwelling in the midlatitudes causing a significant increase in

sediment transport in an alpine river before and after a dambreak flood event fluvial sediment transport in the high mountain partnach river reintal valley bavarian alps was investigated during a 10 year observation period 2001 2010 during this period the downstream reach of the partnach river was decoupled from upstream sediment throughput by a rockslide deposit until 2005 in august 2005 the dam was partially breached during a flood event resulting in renewed sediment coupling between the upstream and downstream reaches a comparison of pre and post dambreak river sediment load data showed that the dissolved load dominated sediment transport prior to august 2005 with a switch to the dominance of bedload transport post dambreak the higher post dambreak bedload rates were particularly evident during the first years after the dam failure due to significant coarse material coupling between active sediment sources undercut banks talus cones and the partnach river in the last years of the observation period 2009 and 2010 the dominance of dissolved load transport was re established copyright 2011 john wiley sons ltd

influence of diversion channel section type on landslide dam draining effect the present study focuses on the emergency response measures for landslide dams this work presents a series of centrifuge model tests conducted on the draining processes of barrier dams that are based on the grain composition of the tangjiashan landslide dam the effects of diversion channels with trapezoid triangular and compound sections on the discharge process and size of the residual dam are discussed the characteristics of the flow erosion during the process of discharge in the different channels are analyzed based on hydrodynamics the results suggest that a diversion channel with a compound section has a higher initial discharge efficiency and lower peak flow and the flow process curve corresponds to a chunky type the draining from this type of a diversion channel could clearly reduce the flood pressure of the river downstream and make the entire process smoother thus the excavation of a diversion channel with a compound section is an efficient and safe method for landslide dam emergency mitigation

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

transient water and sediment storage of the decaying landslide dams induced by the 2008 wenchuan earthquake china article earthquake triggered landslide dams are potentially dangerous disrupters of water and sediment flux in mountain rivers and capable of releasing catastrophic outburst flows to downstream areas we analyze an inventory of 828 landslide dams in the longmen shan mountains china triggered by the mw 7 9 2008 wenchuan earthquake this database is unique in that it is the largest of its kind attributable to a single regional scale triggering event 501 of the spatially clustered landslides fully blocked rivers while the remainder only partially obstructed or diverted channels in steep watersheds of the hanging wall of the yingxiu beichuan fault zone the size distributions of the earthquake triggered landslides landslide dams and associated lakes a can be modeled by an inverse gamma distribution b show that moderate size slope failures caused the majority of blockages and c allow a detailed assessment of seismically induced river blockage effects on regional water and sediment storage monte carlo simulations based on volumetric scaling relationships for soil and bedrock failures respectively indicate that 14 18 of the estimated total coseismic landslide volume of 6 4 14 6 10 9 m 3 was contained in landslide dams representing only 1 4 of the 60 000 slope failures attributed to the earthquake these dams have created storage capacity of 0 6 10 9 m 3 for incoming water and sediment about 25 of the dams containing 2 of the total river blocking debris volume failed one week after the earthquake these figures had risen to 60 20 and 90 90 within one month and one year respectively thus also emptying 92 of the total potential water and sediment storage behind these dams within one year following the earthquake currently only 0 08 10 9 m 3 remain available as natural reservoirs for storing water and sediment while 0 19 10 9 m 3 i e about a third of the total river blocking debris volume has been eroded by rivers dam volume and upstream catchment area control to first order the longevity of the barriers and bivariate domain plots are consistent with the observation that most earthquake triggered landslide dams were ephemeral we conclude that the river blocking portion of coseismic slope failures disproportionately modulates the post seismic sediment flux in the longmen shan on annual to decadal timescales

quasi biennial oscillation of short period planetary waves and polar night jet in winter antarctica observed in saber and merra 2 and mechanism study with a quasi geostrophic model

climatology of the stationary planetary waves seen in the saber timed temperatures 2002 2007 1 the paper focuses on the global spatial structure seasonal and interannual variability of the stationary planetary waves spw with zonal wavenumber s 1 spw1 and s 2 spw2 derived from the saber timed temperature measurements for 6 full years january 2002 december 2007 the monthly mean climatological multiyear average 2002 2007 depictions of spw temperature field extending between 20 and 120 km altitude and 50 latitude are derived a special attention is paid to the spw temperature field in the lower thermosphere where the spw1 amplifies in may and december january in the northern hemisphere nh and in april may and november in the southern hemisphere sh amplitudes in both hemispheres are similar in strato mesosphere however in the lower thermosphere sh amplitudes are significantly larger 30 k than those in nh 20 k the nh spw1 is able to propagate up to 115 km altitude contributing to the winter amplification of the lower thermospheric spw1 but that from the sh cannot penetrate above 90 100 km in the lower thermosphere above h 100 km mainly trapped spw signal is observed the spw1 are almost out of phase in both hemispheres the average 2002 2007 phases are 100 w in nh and 120 e in sh strong evidence indicates that auroral heating is a main origin of the lower thermospheric spw temperature field

sedimentary facies and depositional processes of the diexi ancient dammed lake upper minjiang river china abstract landslide events causing rivers to become dammed are common natural disasters in mountainous area based on the sedimentary facies analysis of 44 sections between proximal and distal parts of a dammed lake this study reveals the sedimentary facies distribution of the diexi ancient dammed lake located in the upper minjiang river on the southeastern margin of the tibet plateau fluvial gravels and sand were deposited in the proximal part of the dammed lake rhythmically bedded silt and horizontally laminated silt to clay were deposited in the distal part of lake due to the deep and steady water conditions after progradation of the fluvial system flood sediments were deposited in the middle part of the lake the flood carried a large amount of sediments into the lake and the decelerating flow generated successively alternating layers of gravels and sand followed by alternating layers of silt with low angle cross stratification parallel bedding and climbing ripples downstream gravel layers formed by four fluvial progradations were found based on the distribution of sedimentary facies in 44 sections after the first fluvial progradation lacustrine sediments at the highest point emerged from the water surface the interval between the second and third fluvial progradation is relatively short and only a terrace was formed namely terrace vi after the fourth fluvial progradation terrace iv was formed although gravel layers formed by fluvial progradations corresponding to terraces ii iii and v were not found it can be determined that a terrace level does not necessarily correspond to a period of fluvial progradation therefore the analysis of sedimentary facies upstream of landslide dams can be used as a supplementary method for inferring the evolution of the dammed lake

analyzing successive landslide dam formation by different triggering mechanisms the case of the tangjiawan landslide sichuan china abstract the catastrophic tangjiawan landslide triggered by the 2008 wenchuan earthquake blocked the duba river impounding one of the most dangerous coseismic barrier lakes in beichuan china the lake was drained by an artificial spillway within one month after the earthquake to minimize the potential dam breach flooding risk however on september 5 2016 this landslide was reactivated and dammed the river again creating a 20 m high dam at the same location and resulting in the formation of a barrier lake with a volume of 0 6 million m3 the day after the event we carried out a field investigation of the landslide and obtained a high resolution image and dem using uav the satellite images from 2005 2008 2010 and 2015 were also collected to analyze the evolution of the landslide together with multi temporal dems the geometry and volumes of the displaced mass and the landslide dams and barrier lakes were calculated using image interpretation and 3d spatial analysis with gis this landslide is of great scientific interest as it presents a good example of multiple reactivation of a pre historical giant landslide under different triggering conditions a reactivation of an older landslide during the wenchuan earthquake and a second reactivation during a rainfall event several years later meanwhile from the hazard assessment and prevention perspective it is also representative as it dammed the river twice in 2008 and 2016 posing threats to both upstream and downstream areas we infer that the successive landslides in this region could be caused by the strong tectonic activities including earthquakes and high average uplifting rate the results of landslide volume analysis using multi temporal dems contribute to the landslide mechanism analysis and suggest that the landslide volume estimation is effected by the landslide type landslide rupture surface location and resolution of dem we also compare the performance of different empirical models of landslide stability and dam breach flood parameters and discuss their application during the quick assessment of the potential hazard of the landslide dams generally the successive landslide dams at the tangjiawan site are caused by the successive landslide reactivations on an anti dip slope controlled by strong tectonic activity and river erosion involve with a mass of loose materials of previous landslide deposition and possess high flood risk to the downstream area the experience gained in this work can be used to assist the hazard assessment and the planning of the emergency measures for similar landslide dams in the future

landslide activity as a geoindicator in italy significance and new perspectives from remote sensing landslide activity responds to rapid environmental changes and represents a relevant geoindicator in mountainous or hilly areas this paper discusses the socio economic relevance of landslide hazard in italy and the problems encountered in establishing relationships between landslide frequency climate and vegetation changes at different time scales landslides blocking a river channel have been carefully taken into account because they are usually characterized by high intensities with regard to the involved masses and movement velocities and their occurrences are often datable via radiocarbon dating this is due to the recovery of organic matter in the landslide dammed lakes for these reasons they can be considered important geoindicators in the wider category of slope failures the marked effects of the anthropogenic activity on slope instability processes in the last 50 years are discussed with reference to two case histories the chianti hills in tuscany and the cinque terre national park in liguria finally two novel techniques of remote sensing are proposed as tools for a systematic monitoring of slope instability at different time and spatial scales both techniques are based on the interferometric synthetic aperture radar sar technology and differ on the type of platform satellite and ground based used to acquire data

signature of rhine valley sturzstrom dam failures in holocene sediments of lake constance germany abstract landslide dammed lakes that form upstream of large scale rockslide avalanches sturzstroms present an enormous potential hazard to downstream areas such failures are recorded in the early holocene sediments of upper lake constance germany by the presence of two clastic layers that were emplaced around 9400 cal ybp the sedimentology of these layers contrasts sharply with the typical late glacial and holocene lacustrine sediments present beneath the floor of the lake sedimentary structures and the magnetic fabric of these clastic deposits strongly suggest that they were emplaced by hyperpycnal underflows related to catastrophic floods that entered the lake from the rhine river from stratigraphic and geologic data it is inferred that the hyperpycnite deposits are directly related to the failure of two sturzstrom dams and the draining of the dammed lakes that developed upstream from them these lakes were dammed by the flims and the tamins sturzstrom deposits respectively sedimentologic data from lake constance indicate that the two successive events occurred within a very short time interval probably not exceeding several years consequently these lacustrine deposits provide essential information about the morphogenic evolution of the rhine river valley during the early holocene and about the sturzstrom events that occurred during the same time interval

analysis of past and future dam formation and failure in the santa cruz river san juan province argentina abstract around 11 5 106 m3 of rock detached from the eastern slope of the santa cruz valley san juan province argentina in the first fortnight of january 2005 the rockslide debris avalanche blocked the course resulting in the development of a lake with maximum length of around 3 5 km the increase in the inflow rate from 47 000 74 000 m3 d between april and october to 304 000 m3 d between late october and the first fortnight of november accelerated the growing rate of the lake on 12 november 2005 the dam failed releasing 24 6 106 m3 of water the resulting outburst flood caused damages mainly on infrastructure and affected the facilities of a hydropower dam which was under construction 250 km downstream from the source area in this work we describe causes and consequences of the natural dam formation and failure and we dynamically model the 2005 rockslide debris avalanche with dan3d additionally as a volume 24 106 m3of rocks still remain unstable in the slope we use the results of the back analysis to forecast the formation of a future natural dam we analyzed two potential scenarios a partial slope failure of 6 5 106 m3 and a worst case where all the unstable volume remaining in the slope fails the spreading of those potential events shows that a new blockage of the santa cruz river is likely to occur according to their modeled morphometry and the contributing watershed upstream the blockage area as the one of 2005 the dams would also be unstable this study shows the importance of back and forward analysis that can be carried out to obtain critical information for land use planning hazards mitigation and emergency management

layered internal structure and breaching risk assessment of the higashi takezawa landslide dam in niigata japan the internal structure and geotechnical properties of landslide dams have rarely been examined in detail although they largely control the longevity and potential failure mechanisms of the dams during the 2004 mid niigata prefecture earthquake thousands of landslides were triggered and many landslide dams were formed in the imo river basin among these landslides dams the biggest one that occurred in the higashi takezawa district threatened both the upstream and downstream areas emergency and eventual permanent countermeasures were successfully performed to mitigate the hazards presented by the dam the preserved landslide dam provides a good field study area for improving understanding of the formation and stability of similar features to characterize its internal structure and to provide more reliable information for stability analysis we used a multiple channel surface wave technique and microtremor array measurements to survey the dam s s wave velocity v s profile our results show that the integrated use of these methods is an effective approach for determining the s wave velocity structure of landslide dams irrespective of the mountainous environment in which they typically occur the v s profile suggests that the displaced landslide materials had been little disturbed during movement although movement was rapid and over a long distance we also discuss herein the landsliding mechanism and assess the breaching risk of the landslide dam due to overtopping c 2016 elsevier b v all rights reserved

time gcm study of the ionospheric equatorial vertical drift changes during the 2006 stratospheric sudden warming this modeling study quantifies the daytime low latitude vertical e b drift changes in the longitudinal wave number 1 wn1 to wn4 during the major extended january 2006 stratospheric sudden warming ssw period as simulated by the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm and attributes the drift changes to specific tides and planetary waves pws the largest drift amplitude change approximately 5 m s is seen in wn1 with a strong temporal correlation to the ssw the wn1 drift is primarily caused by the semidiurnal westward propagating tide with zonal wave number 1 sw1 and secondarily by a stationary planetary wave with zonal wave number 1 pw1 sw1 is generated by the nonlinear interaction of pw1 and the migrating semidiurnal tide sw2 at high latitude around 90 100 km the simulations suggest that the e region pw1 around 100 130 km at the different latitudes has different origins at high latitudes the pw1 is related to the original stratospheric pw1 at midlatitudes the model indicates pw1 is due to the nonlinear interaction of sw1 and sw2 around 95 105 km and at low latitudes the pw1 might be caused by the nonlinear interaction between de2 and de3 the time evolution of the simulated wn4 in the vertical e b drift amplitude shows no temporal correlation with the ssw the wn4 in the low latitude vertical drift is attributed to the diurnal eastward propagating tide with zonal wave number 3 de3 and the contributions from se2 te1 and pw4 are negligible

late holocene evolution of a floodplain impounded by the smrduta landslide carpathian mountains czech republic we present here a detailed study of the sedimentary archive within a landslide controlled impounded floodplain smrduta site czech flysch carpathians using geochronological 14c and 137cs sedimentological and pollen evidence a sedimentary sequence deposited above the landslide dam points to three highly discontinuous and instantaneous depositional events dated to 4 6 and 2 0 cal ka bp whereas the last cycle started approximately in the 17 18th centuries and has continued to recent times stages of mass movement activity revealed by the smrduta landslide correlate well with major humid late holocene oscillations suggesting its high sensitivity to century scale climatic deteriorations the character of lithological units forming individual sedimentary pulses erosional hiatuses and sedimentary traces caused by the july 1997 extreme flood indicate a decisive role of large flood events during accretion and erosion of the floodplain impounded section

landscape evolution modelling of naturally dammed rivers natural damming of upland river systems such as landslide or lava damming occurs worldwide many dams fail shortly after their creation while other dams are long lived and therefore have a long term impact on fluvial and landscape evolution this long term impact is still poorly understood and landscape evolution modelling lem can increase our understanding of different aspects of this response our objective was to simulate fluvial response to damming by monitoring sediment redistribution and river profile evolution for a range of geomorphic settings we used lem lapsus which calculates runoff erosion and deposition and can deal with non spurious sinks such as dam impounded areas because fluvial dynamics under detachment limited and transport limited conditions are different we mimicked these conditions using low and high erodibility settings respectively to compare the relative impact of different dam types we evaluated five scenarios for each landscape condition one scenario without a dam and four scenarios with dams of increasing erodibility results showed that dam related sediment storage persisted at least until 15 000years for all dam scenarios incision and knickpoint retreat occurred faster in the detachment limited landscape than in the transport limited landscape furthermore in the transport limited landscape knickpoint persistence decreased with increasing dam erodibility stream capture occurred only in the transport limited landscape due to a persisting floodplain behind the dam and headward erosion of adjacent channels changes in sediment yield variation due to stream captures did occur but cannot be distinguished from other changes in variation of sediment yield comparison of the model results with field examples indicates that the model reproduces several key phenomena of damming response in both transport limited and detachment limited landscapes we conclude that a damming event which occurred 15 000years ago can influence present day sediment yield profile evolution and stream patterns copyright c 2014 john wiley sons ltd

a conjugate study of mean winds and planetary waves employing enhanced meteor radars at rio grande argentina 53 8 s and juliusruh germany 54 6 n 1 two meteor radars with enhanced power and sensitivity and located at closely conjugate latitudes 54 6 n and 53 8 s are employed for interhemispheric comparisons of mean winds and planetary wave structures at periods of 8 to 20 days our study uses data from june 2008 through may 2010 during which both radars provided nearly continuous wind measurements from 80 to 100 km monthly mean winds at 53 8 s exhibit a stronger westward zonal jet in spring and early summer at lower altitudes and no westward winds at higher altitudes in contrast westward mean winds of 5 10 ms 1 at 54 6 n extend to above 96 km during late winter and early spring each year equatorward mean winds extend approximately from spring to fall equinox at both latitudes with amplitudes of 5 10 ms 1 meridional mean winds are more variable at both latitudes during fall and winter with both poleward and equatorward monthly means indicating longer period variability planetary waves seen in the 2 day mean data are episodic and variable at both sites exhibit dominant periodicities of 8 10 and 16 20 days and are more confined to late fall and winter at 54 6 n at both latitudes planetary waves in the two period bands coincide closely in time and exhibit similar horizontal velocity covariances that are positive negative at 54 6 n 53 8 s during peak planetary wave responses

climate and other factors in the development of river and interfluve profiles in bhutan eastern himalayas abstract the longitudinal profiles of the main n s aligned rivers and the crests of the interfluve mountain ranges of bhutan have been plotted against latitude the river profiles are highly variable even between branches of the same system the main rivers in eastern bhutan are antecedent and rise in tibet they have irregular concave bed profiles in deep steeply sided valleys the rivers further west rise on the southern slopes of the high himalaya they have stepped profiles with steep concave sections in gorges through the southern mountains and one or more concave sections upstream separated by knickpoints all of the n s interfluve ranges rise steeply from the piedmont some then dip to major passes before again rising irregularly northwards to the high himalaya whilst others continue to climb northwards as irregular monoclines the combination of various types of river and interfluve profiles creates a range of valley forms the heterogeneity means that it is not possible to generalise about a typical bhutanese river interfluve or valley relief profile there is no indication that the rivers of bhutan have more knickpoints than those of the central and western himalayas rainfall and runoff data soils and natural vegetation have been examined for indications of significantly drier conditions in eastern bhutan the rainfall data show an eastwards decrease in the southern foothills probably due to the rainshadow cast by the meghalaya plateau to the south but mean annual totals are about or above three metres throughout and the whole of this zone has a wet climate there is no marked e w climatic trend in the drier interior of bhutan we attribute the general topographic structure of bhutan and the variability of river and interfluve profiles and valley forms more to tectonic factors than to climatic variation

a stationary planetary scale feature in the tropical mesopause temperature field three years of daily global temperature grids at 5 7 9 and 12 scale heights have been retrieved from nimbus 6 pressure modulator radiometer measurements a stationary pattern is observed in the tropical 12 scale height about 82 km altitude seasonal and monthly mean temperatures that has an approximately wavenumber four zonal structure this pattern has warm centers located near the equator and cold centers positioned some 10 to 20 degrees of latitude away towards the winter pole the amplitude of this pattern varies in a semiannual fashion with maxima occurring during late winter and late summer the structure and behavior of the feature compares well with the seasonal changes in tropical deep convective storms leading to speculation that the feature may be driven by tropospheric gravity waves

some features of the climatology of the middle atmosphere revealed by nimbus 5 and 6 abstract a scheme for deriving three dimensional horizontal and vertical velocity fields from global satellite temperature data is described and applied to the new cospar international reference atmosphere cira to illustrate some features of the climatology of the stratosphere and mesosphere the scheme produces horizontal winds that compare well with existing mesospheric climatologies derived from radar and rocket data this is because the drag on the zonal flow is taken into account the drag is large in the mesosphere and is consistent with that produced by breaking gravity waves calculations of qy indicate the possibility of unstable waves in the summer and winter mesosphere in the stratosphere the scheme yields diagnostics of planetary wave propagation which are sometimes similar to those produced by winds from schemes based on just the horizontal momentum equations but in the october southern stratosphere for example there are occasions when the effects of the drag on the zonal flow are requ

stationary planetary waves in upper mesospheric winds abstract quasi stationary planetary scale longitudinal variations are found in the upper mesospheric winds measured during winter by the hrdi satellite instrument these are negatively correlated with eddy winds in the stratosphere two different mechanisms are proposed to explain the mesospheric perturbation winds and their anticorrelation with stratospheric winds 1 planetary waves propagate through the stratosphere and into the mesosphere with a phase shift of one half cycle and 2 mesospheric perturbations are forced in situ by gravity waves whose spectrum has longitudinal asymmetries due to filtering by planetary waves in the stratosphere the first mechanism is more consistent with the observations during southern hemisphere late winter august and also may explain the observations during northern hemisphere early winter december the second mechanism gives a more consistent explanation for the northern hemisphere late winter observations as previously shown by the author the hemispheric diff

global temperature stationary planetary waves extending from 20 to 120 km observed by timed saber version 1 07 temperature measurements from saber instrument on board of timed satellite during 2006 2007 are used to study the temperature stationary planetary waves spws from 20 to 120 km to cover the high latitudes in both hemispheres 80 degrees s 80 degrees n and most local times 120 day data are combined together into one data set the most pronounced spw features are the large amplitudes in the upper mesosphere and lower thermosphere umlt while the spws below 90 95 km share common features with previous observations in both hemispheric umlt spws amplitudes are large at middle and high latitudes throughout the year while their amplitudes in tropics are small wave 1 activity is generally stronger than the corresponding wave 2 activity with maximum amplitudes larger than 15 k occurring at about 60 degrees 70 degrees north or south at the altitudes between 112 km and 119 km wave 1 amplitudes are larger in the southern hemisphere sh than in the northern hemisphere nh their phases are normally tilt westward with increasing height below similar to 110 km above this altitude the wave 1 and wave 2 phases remain nearly unchanged with height indicating the in situ generations and no propagations comparisons between the observed spw structures and those from the nrlmsise 00 model have been done result shows their consistent features below similar to 80 km and that nrlmsise 00 model gives no spw information from 95 to 125 km but does have longitudinal variations above similar to 125 km that are similar to the observed spw features above similar to 110 km

momentum flux estimates accompanying multiscale gravity waves over mount cook new zealand on 13 july 2014 during the deepwave campaign observations performed with a rayleigh lidar and an advanced mesosphere temperature mapper aboard the national science foundation national center for atmospheric research gulfstream v research aircraft on 13 july 2014 during the deep propagating gravity wave experiment deepwave measurement program revealed a large amplitude multiscale gravity wave gw environment extending from 20 to 90 km on flight tracks over mount cook new zealand data from four successive flight tracks are employed here to assess the characteristics and variability of the larger and smaller scale gws including their spatial scales amplitudes phase speeds and momentum fluxes on each flight a large scale mountain wave mw having a horizontal wavelength 200 300 km was observed smaller scale gws over the island appeared to correlate within the warmer phase of this large scale mw this analysis reveals that momentum fluxes accompanying small scale mws and propagating gws significantly exceed those of the large scale mw and the mean values typical for these altitudes with maxima for the various small scale events in the range 20 105 m2 s 2

on the composite response of the mlt to major sudden stratospheric warming events with elevated stratopause based on a climate chemistry model constrained by reanalyses below 50 km the zonal mean composite response of the mesosphere and lower thermosphere mlt to major sudden stratospheric warming events with elevated stratopauses demonstrates the role of planetary waves pws in driving the mean circulation in the presence of gravity waves gws helping the polar vortex recover and communicating the sudden stratospheric warming ssw impact across the equator with the ssw onset strong westward pw drag appears above 80 km primarily from the dissipation of wave number 1 perturbations with westward period of 5 12 days generated from below by the unstable westward polar stratospheric jet that develops as a result of the ssw the filtering effect of this jet also allows eastward propagating gws to saturate in the winter mlt providing eastward drag that promotes winter polar mesospheric cooling the dominant pw forcing translates to a net westward drag above the eastward mesospheric jet which initiates downwelling over the winter pole as the eastward polar stratospheric jet returns this westward pw drag persists above 80 km and acts synergistically with the return of westward gw drag to drive a stronger polar downwelling that warms the pole adiabatically and helps reform the stratopause at an elevated altitude with the polar wind reversal during the ssw onset the westward drag by the quasi stationary pw in the winter stratosphere drives an anomalous equatorial upwelling and cooling that enhance tropical stratospheric ozone along with equatorial wind anomalies this ozone enhancement subsequently amplifies the migrating semidiurnal tide amplitude in the winter midlatitudes

cosmogenic dating of rock avalanches constraining quaternary stratigraphy and regional neotectonics in the argentine central andes 32 s abstract this paper provides a comprehensive review of the chronostratigraphy of six rock avalanches clustered in the northern extreme of the cordon del plata range these rock avalanches are stratigraphically related to pleistocene glacial drifts and valley fill deposits documenting the regional neotectonic activity we used cosmogenic dating tcn to directly date block surfaces of rock avalanche deposits as well as optically stimulated luminescence dating osl of paleo lakes dammed by these rock avalanches our new direct dates 17 tcn and 4 osl determine the middle to late pleistocene age of these collapses these are in contrast to the previously established chronostratigraphy based on relative dating techniques paleontological context and tephrochronology these new data help to redefine the geomorphological evolution of the mendoza river valley especially the new data indicate that the glacial stratigraphy earlier proposed must be reconsidered we redefine this stratigraphy as far as possible with our data and discuss the data in relation with other recently published results however it becomes clear that the glacial history of the mendoza valley has to be studied anew by using modern dating techniques in addition our data suggest that the carrera fault system bounding the valleys of the cordillera del plata has been active more recently than proposed earlier

empirical prediction of coseismic landslide dam formation in this study we develop an empirical method to estimate the volume threshold for predicting coseismic landslide dam formation using landscape parameters obtained from digital elevation models dems we hypothesize that the potential runout and volume of landslides together with river features determine the likelihood of the formation of a landslide dam to develop this method a database was created by randomly selecting 140 damming and 200 non damming landslides from 501 landslide dams and 60 000 landslides induced by the mw 7 9 2008 wenchuan earthquake in china we used this database to parameterize empirical runout models by stepwise multivariate regression we find that factors controlling landslide runout are landslide initiation volume landslide type internal relief h and the h l ratio between h and landslide horizontal distance to river l in order to obtain a first volume threshold for a landslide to reach a river the runout regression equations were converted into inverse volume equations by taking the runout to be the distance to river a second volume threshold above which a landslide is predicted to block a river was determined by the correlation between river width and landslide volume of the known damming landslides the larger of these two thresholds was taken as the final damming threshold this method was applied to several landslide types over a fine geographic grid of assumed initiation points in a selected catchment the overall prediction accuracy was 97 4 and 86 0 for non damming and damming landslides respectively the model was further tested by predicting the damming landslides over the whole region with promising results we conclude that our method is robust and reliable for the wenchuan event in combination with pre event landslide susceptibility and frequency size assessments it can be used to predict likely damming locations of future coseismic landslides thereby helping to plan emergency response copyright 2014 john wiley sons ltd

plugs or flood makers the unstable landslide dams of eastern oregon abstract landslides into valley bottoms can affect longitudinal profiles of rivers thereby influencing landscape evolution through base level changes large landslides can hinder river incision by temporarily damming rivers but catastrophic failure of landslide dams may generate large floods that could promote incision dam stability therefore strongly modulates the effects of landslide dams and might be expected to vary among geologic settings here we investigate the morphometry stability and effects on adjacent channel profiles of 17 former and current landslide dams in eastern oregon data on landslide dam dimensions former impoundment size and longitudinal profile form were obtained from digital elevation data constrained by field observations and aerial imagery while evidence for catastrophic dam breaching was assessed in the field the dry primarily extensional terrain of low gradient volcanic tablelands and basins contrasts with the tectonically active mountainous landscapes more commonly associated with large landslides all but one of the eastern oregon landslide dams are ancient likely of order 10 3 to 10 4 years old and all but one has been breached the portions of the oregon landslide dams blocking channels are small relative to the area of their source landslide complexes 0 4 33 6 km 2 the multipronged landslides in eastern oregon produce marginally smaller volume dams but affect much larger channels and impound more water than do landslide dams in mountainous settings as a result at least 14 of the 17 82 large landslide dams in our study area appear to have failed cataclysmically producing large downstream floods now marked by boulder outwash compared to a 40 70 failure rate for landslide dams in steep mountain environments morphometric indices of landslide dam stability calibrated in other environments were applied to the oregon dams threshold values of the blockage and dimensionless blockage indices calibrated to worldwide data sets successfully separate dam sites in eastern oregon that failed catastrophically from those that did not accumulated sediments upstream of about 50 of the dam sites indicate at least short term persistence of landslide dams prior to eventual failure nevertheless only three landslide dam remnants and one extant dam significantly elevate the modern river profile we conclude that eastern oregon s landslide dams are indeed floodmakers but we lack clear evidence that they form lasting plugs

interactions between gravity waves and planetary scale flow simulated by the gfdl skyhi general circulation model abstract in order to study interactions between gravity waves and planetary flow in the middle atmosphere a 3 latitude by 3 6 longitude version of the 40 level gfdl skyhi general circulation model is analyzed using bihourly sampled output data it is shown by a space time spectral analysis that gravity waves in the mean zonal westerlies easterlies mainly consist of westward eastward moving components and carry easterly westerly momentum upward and decelerate the mean zonal westerlies easterlies in the mesosphere zonal momentum flux convergence due to gravity waves accounts for nearly all of the eliassen palm e p flux divergence in the summer mesosphere this convergence accounts for 30 50 of that in the winter upper mesosphere however this percentage is probably an underestimate since the convergence is significantly enhanced in a high resolution 1 1 2 model currently being integrated vertical propagation of gravity waves is affected not only by the mean zonal wind but also

the origin of stationary planetary waves in the upper mesosphere abstract satellite observations indicate that quasi stationary planetary waves often exist to at least 100 km in the winter mesosphere waves are also seen in the summer upper mesosphere a three dimensional numerical model was used to simulate these waves and to diagnose the physical processes involved the waves simulated in the model closely resemble observed waves several model runs that isolate specific processes are used to determine the relative importance of two forcing mechanisms in the model planetary waves that propagate from below are significantly damped at the altitude where gravity wave drag becomes large about 75 km in the winter midlatitudes or below if a reversal in the mean wind is encountered momentum forcing associated with breaking gravity waves that have been filtered by planetary scale wind variations below acts to generate planetary waves in the middle and upper mesosphere the amplitude from in situ forcing by gravity wave breaking exceeds the amplitude from the upward prop

laboratory experiments on the failure of coarse homogeneous sediment natural dams on a sloping bed we present the results of a systematic series of 168 laboratory experiments that examine the critical conditions for the failure of landslide dams which obstruct the course of mountain rivers the experiments were carried out by using three different sediment materials with a quasiuniform grain size distribution and with a flume bed slope angles that ranged between 0 and 5 71 0 10 three main typologies of dam failure were observed for increasing values of the dam s downstream face angle 1 overtopping 2 headcutting which led to the formation of an erosion channel on the dam s downstream face that progressively migrated up to the dam crest and 3 initial slide of large part of superficial layer of the dam s downstream face which was followed by headcutting the experiments focused on the second type of failure to provide a safety criterion based on the upstream reservoir level the quantities that govern this phenomenon have been identified and a functional relationship is proposed based on

longitudinal variations in mesospheric winds evidence for gravity wave filtering by planetary waves abstract mesospheric horizontal wind data from the high resolution doppler image hrdi satellite instrument are used to investigate the longitudinal variation of nontidal winds in the upper mesosphere and their relationship with winds in the stratosphere the period covered by the study is late winter february mid march for 1992 1994 the results indicate that there is a negative correlation between longitudinal variations of the zonal winds in the stratosphere and those in the mesosphere and between longitudinal variations of the meridional winds in the stratosphere and mesosphere the data are examined to determine which of several possible causes is responsible the possibilities are 1 that planetary scale disturbances are produced in situ by gravity wave drag in the mesosphere that is not zonally symmetric because of filtering by the planetary waves in the stratosphere 2 that asymmetries are caused by longitudinal variations in gravity wave drag due to azonal source distributions that are coinc

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

modeling of natural dam failure modes and downstream riverbed morphological changes with different dam materials in a flume test abstract landslide dam failure modes are influenced by dam geometry material characteristics and riverbed conditions the different characteristics of earthquake and rainfall induced natural dams and the effects of riverbed conditions on dam failure have not attracted much attention from researchers in the past this study used flume tests to simulate earthquake and rainfall induced landslide dam failures for various combinations of dam geometry materials and riverbed conditions the 64 flume test combinations thus included two discharge rates two dam shapes triangular and trapezoidal with two heights two types of riverbed conditions and two types of dam material with two different water contents the experimental results show that dam geometry the amount of inflow hydraulic conductivity of the dam material and riverbed conditions have considerable effect on dams lifespan and their corresponding failure mode the hydraulic conductivity of the dam material affected the dam lifespan and its corresponding failure mode the four observed failure modes of dam breaks in rigid and mobile riverbeds constitute progressive erosion overtopping erosion slope slide and complex failure the complex failure mode which involves headward erosion slope slide and overtopping can occur in highly hydraulically conductive dams with high discharge progressive erosion occurs in highly hydraulically conductive dams with low discharge dam material with low hydraulic conductivity tends to fail by pure overtopping regardless of the dam shape and material dams in a mobile riverbed had a longer lifespan than those in a rigid riverbed the composition of the dam material affected the peak outflow discharge after dam break compared with rigid riverbeds dams in mobile riverbeds delay the arrival time of peak sediment discharge failure modes triggering flash floods and sediment transport after a dam break involved a series of sandbars and an armoring layer in the downstream riverbed earthquake induced dry material forming highly hydraulically conductive dams generally fail through complex when failure was subjected to a high discharge dams composed of wet materials tend to fail by overtopping in flume tests dam failure mode and inflow changed downstream mobile riverbed morphology in ways similar to those seen in full scale model tests conducted in the field

3d dem investigation on the morphology and structure of landslide dams formed by dry granular flows abstract large scale landslide dams triggered by earthquakes or rainfall can cause disasters due to inundation upstream and outburst floods downstream after dam failure landslide dams formed by rock debris avalanches are loose in structure and have a lack of stability thus they are more susceptible to breaking the morphological and structural features of landslide dams directly depend on the formation process and greatly affect the dam stability as well as the dam failure modes this study presents the transportation and deposition characteristics of dry granular flows with grains of mixed sizes during the formation of landslide dams via 3d discrete element method dem simulations mainly taking into consideration of the influence of the sliding area length angle and roughness the results show reverse segregation during grain transportation and deposition processes the position of the particles forming the initial deposited layers was also reversed it was found that when the sliding area angle was larger the crest surface frontal angle and deposit width increased with the increment of the sliding area length for lower sliding area angles the deposit width and crest surface frontal angle showed little change the increase of sliding length and base friction coefficient as well as the decrease of the sliding area angle will enhance the size segregation as the slope angle increases the dominant direction of the force chains shifts significantly and the sliding length mainly influences the magnitude of the normal contact force in the other directions these considerations can contribute to a better understanding of the landslide dam morphology and structure after their formation

earthquake dammed lakes in new zealand eleven small lakes were formed by landslides caused by the 1929 buller earthquake four others were formed by other historic earthquakes in new zealand at least nine other new zealand lakes are also dammed by landslides and were probably formed by prehistoric earthquakes when recognized by morphology synchronous age and areal distribution earthquake dammed lakes could provide an estimate of paleoseismicity for the past few hundred or thousand years

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

modeling and analysis of the structure and generation of the terdiurnal tide the terdiurnal or 8 h tide has been seen in a number of midlatitude radar measurements and has recently been mapped globally at 95 km a series of calculations and model simulations are used to examine the processes responsible for generating this tide and for its strong hemispheric asymmetry the model tidal structure deviates significantly from the structure of a single hough mode in contrast to the diurnal tide the dominant cause of the hemispheric asymmetry is the sensitivity of the propagation to the background state particularly the static stability several conceptual views of the tide are explored to give a heuristic view of this asymmetry this analysis predicts that particular modes are prohibited from propagating in large regions of the summer mesosphere the tide occurs naturally in a three dimensional nonlinear model extending from the tropopause to the lower thermosphere the model tide shows a number of features in common with observations including amplitude maxima in midlatitudes a wintertime peak and zonal winds larger than meridional winds the tidal amplitude in the model is weaker than observed at 95 km several interactive model integrations are performed to determine the forcing mechanism for the tide these calculations indicate that the direct solar forcing of the terdiurnal tide is the dominant mechanism occurring in the model at middle and high latitudes nonlinear interactions contribute to the low latitude tide

forecasting landslide hazard by the 3d discrete element method a case study of the unstable slope in the lushan hot spring district central taiwan abstract catastrophic landslides and related phenomena are commonly facilitated by the subtropical climate with frequent typhoons and recurrent earthquakes in taiwan s mountainous areas one area susceptible to potentially catastrophic landslides is located at lushan in central taiwan which is famous for its hot springs and tourism the northern slope above the hot spring district slips gradually and frequently due to heavy rainfall for safety reasons the slip affected area has been under constant borehole monitoring by government agencies and a controversial public debate has arisen over permanent evacuation of the hot spring district in this study we attempt to simulate possible scenarios of catastrophic slope failure using slip geometries derived from the monitoring data and assess potential landslide impact areas by a discrete element method using the pfc3d code in the worst case scenario the lushan hot spring district is predicted to be destroyed by debris in 20 s besides the planned regional emergency refuge is rapidly jeopardized by flooding resulted from landslide dammed lakes this study addresses catastrophic slope failure under heavy rainfall conditions given a range of friction coefficients and varied continuity of the failure surfaces it is noted that the pfc3d code has limitations in modeling all complex mechanisms of landslide particularly in modeling loss of material shear strength due to increases in pore pressure nevertheless the numerical simulation results by the 3d discrete element method provide scenario based runout paths particle velocities and landslide affected areas which are useful information for decision support and future landslide hazard assessment

characteristics of the landslide dams induced by the 2008 wenchuan earthquake and dynamic behavior analysis using large scale shaking table tests abstract the ms 8 0 wenchuan earthquake triggered at least 257 landslide dams more than 300 aftershocks with the magnitudes higher than ms 4 0 occurred after the formation of these landslide dams which might largely influence the structure and soil properties of these dams this paper aims to comprehensively investigate the characteristics of the landslide dams induced by the 2008 wenchuan earthquake and study the dynamic behaviors of the landslide dams under aftershocks using large scale shake table tests first the characteristics of the landslide dams including the distribution geometric parameters stability and longevity mitigation measures and the influence of the aftershocks are proposed then two groups of shaking table tests to simulate the dynamic behaviors of two types of landslide dams under aftershocks are illustrated one with quartz sand contained 10 kaolin dam i and the other with quartz sands all dam ii finally the results of the tests including the acceleration distribution dam deformation and dam breaching process are discussed through this study it is found that the landslide dams caused by high magnitude earthquakes have distinctive characteristics which may largely influence the stability breach process and risks of these dams in the model tests the accelerations are generally higher on the surface of the dams either on the crest or on the both upstream and downstream slopes the dam i was prone to settlement and cracking the aftershocks may not directly trigger the failures of landslide dams but accelerate the overtopping failures by lowering the dam crest with settlement and cracking

effects of tectonic deformation and landslides in the erosion of a mountain plateau in the transitional zone between the central and patagonian andes

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

high altitude 0 100 km global atmospheric reanalysis system description and application to the 2014 austral winter of the deep propagating gravity wave experiment deepwave abstracta data assimilation system das is described for global atmospheric reanalysis from 0 to 100 km altitude we apply it to the 2014 austral winter of the deep propagating gravity wave exper

observations and modeling of the 6 hour tide in the upper mesosphere 1 this paper presents observations and modeling of the 6 hour tide radar observations of horizontal winds at esrange 68 n 21 e indicate that this tidal periodicity is a consistent part of the diurnal variation and is largest during midwinter vertical structure and phase coherence provide strong support that the observed oscillations are tidal model simulations generate a tide that has many similarities to the observed tide at esrange diagnostic model tests indicate that the tide is forced primarily by the 6 hour component of solar heating globally the monthly mean simulated tide is dominated by the migrating component except near the poles although the contribution from nonmigrating modes is not negligible according to the model both migrating and nonmigrating 6 hour tides have small amplitude in low latitudes

the evolution of the samaoding paleolandslide river blocking event at the upstream reaches of the jinsha river tibetan plateau abstract a large number of landslides have occurred in the upstream reaches of the jinsha river tibetan plateau due to the intensity of tectonic movement in the area remote sensing and field investigation indicate that one of them the samaoding paleolandslide previously blocked the river various river blocking phenomena are well preserved including the old landslide dam and deposits fluvial sediments and hydrostatic sandy sediment to better understand the evolution of the samaoding landslide the authors carried out thermoluminescence tl dating and numerical simulations the tl analysis shows that the landslide occurred at 10 6 0 5 ka bp discrete element method dem simulation of the landslide based on landform restoration provided results that are consistent with field observations the simulation indicates that the entire landslide process lasted for 80 s and the sliding mass reached a maximum velocity of 64 m s the landslide formed a landslide dam with a length of 1900 m a width of 600 m and a depth of 200 m the simulation results show that the level of the riverbed at that the time of the landslide was at least 25 m higher than it is today on the combined basis of the simulation results and field observations the authors propose explanation that the following valley evolution sequence occurred after river blocking the landslide dam experienced flood overtopping and then was eroded until it had mostly had been transported away by river flow and the river then rapidly incised the bedrock to form the present day landform based on the field investigations the authors summarize the failure mechanism of steep inclined antidip rockslides and found that tectonics play an important role in the formation of landslide dams or trigger of landslides and the failure of landslide dams in an active tectonic environment of tibetan plateau

large scale landslides in toyama prefecture central japan and their probable relationship with earthquakes large scale landslides along the kubusu and besso rivers in toyama prefecture are developed in the miocene iwaine formation which is composed of andesitic lava tuff and tuff breccia in the middle member of this formation the tuff is easily altered to montmorillonite bearing rock and subsequently plays an important role in the development of landslides events which tend to be large scale events as the massive lava of the upper member forms a cap rock over the tuff the kiritani and koinami basins which are flat intermontane basins located along the kubusu and besso rivers respectively are interpreted as landslide dammed lakes later filled with sediment accelerator mass spectrometry 14c ages show that the landslides forming each dam occurred simultaneously at approximately 2500 bp these ages were measured from wood fragments embedded in the landslide material of kiritani and from an in situ stump drowned during the impoundment of koinami if the trigger of these landslides was an earthquake it is most likely to have been the penultimate event along the atotsugawa fault zone

the whole atmosphere response to changes in the earth s magnetic field from 1900 to 2000 an example of top down vertical coupling we study the effects of changes in the earth s magnetic field between 1900 and 2000 on the whole atmosphere 0 500 km altitude based on simulations with the whole atmosphere community climate model extension magnetic field changes directly affect the temperature and wind in the upper atmosphere 110 km via joule heating and the ion drag force however we also find significant responses in zonal mean temperature and zonal wind in the southern hemisphere sh middle to high latitude troposphere stratosphere and mesosphere of up to 2 k and 2 m s as well as regionally significant changes in northern hemisphere nh polar surface temperatures of up to 1 3 k in december january february in the sh changes in gravity wave filtering in the thermosphere induce a change in the residual circulation that extends down into the upper mesosphere where further changes in the mean wind climatology are generated together with changes in local planetary wave generation and or amplification and gravity wave filtering this induces further changes to a residual circulation cell extending down into the troposphere however inaccuracies in the simulated sh upper mesospheric wind climatology probably mean that the simulated temperature and wind responses in the sh lower and middle atmosphere are also inaccurate the nh middle atmosphere response is zonally asymmetric consisting of a significant change in the positioning and shape of the upper stratospheric polar vortex which is dynamically consistent with the surface temperature response however the downward coupling mechanism in the nh is generally less clear

first observations of short period eastward propagating planetary waves from the stratosphere to the lower thermosphere 110 km in winter antarctica unique fe lidar observations in may 2014 at mcmurdo combined with aura microwave limb sounder mls measurements lead to a new discovery that the amplitudes of 4 day and 2 5 day planetary waves pws grow rapidly from 1 2 k at 100 km to over 10 k at 110 km this report is also the first observation of short period 1 5 days eastward propagating pws from 30 km all the way to 110 km the specified dynamics whole atmosphere community climate model reproduces the observed three dominant peaks of amplitudes in temperature and coherent vertical phase structures the data model comparison indicates a possible mechanism after pws originated from the stratosphere dissipate along the critical level the surviving waves are amplified by in situ instability in the mesosphere and lower thermosphere resulting in the second third peak in geopotential temperature this third peak in temperature explains the pw amplitude growth from 100 to 110 km

influence of textural properties on the failure mode and process of landslide dams abstract the failure of a landslide dam is a sudden geo hazard which can significantly threatens the lives and property of local residents in this study 11 experiments were designed to reproduce the failure process of landslide dams with different grain size distributions and hydrodynamic conditions in order to fully consider the influence of seepage on the stability of landslide dams with different textural properties the inflow discharge was small in these tests by analyzing the experimental data we found that the textural properties plays a key role in the failure modes and process of landslide dams the eleven tests produced five different results the landslide dam in experiment 1 and 8 remained stable the landslide dam in experiment 2 partially failed in experiments 3 6 the dams failed due to overtopping and erosion while in experiment 7 the dam failed due to overtopping and soil collapse in experiment 9 11 the dams failed due to piping overtopping and erosion in addition the evolution of the outflow discharge and density also varied for the different textural properties of the dam materials based on the experimental results the landslide dam materials were classified as coarse matrix controlled medium particle controlled fine matrix controlled and balanced composition the failure modes and process as well as the evolution characteristics of the outflow discharge and flow density were all summarized providing a scientific reference for disaster prevention and mitigation research of landslide dams

laboratory scale investigation of the 3 d geometry of landslide dams in a u shaped valley abstract landslide dams form when a landslide obstructs narrow and steep valleys in mountainous areas since these dams may fail over a short time and cause secondary geological disasters in the downstream area the stability of such dams must be assessed in an accurate and timely manner the three dimensional 3 d geometry of a landslide dam which is one of the essential indices for stability analyses is highly influenced by the landslide dam formation conditions including the sliding surface dip angle and the valley topography however few studies have focused on the correlation between the 3 d geometry and formation conditions of a landslide dam a photogrammetric system was used to develop a laboratory apparatus to simulate the formation process of a landslide dam and construct a digital model for the 3 d geometry of a landslide dam in a u shaped valley then a series of experiments were designed to systematically investigate the formation process and the 3 d geometry of landslide dams under different combinations of valley bed inclinations 0 4 8 and 12 and sliding surface dip angles 30 45 60 and 75 the results indicate that the sliding surface dip angle has a significant effect on the length and height of a landslide dam whereas the valley bed inclination has a limited effect on the length and height compared with its effect on the relative angles of a landslide dam in addition the cross sectional profiles of landslide dams can be classified into three categories namely symmetric asymmetric and flat shapes and these profiles are predominantly affected by the sliding surface dip angle instead of the valley bed inclination subsequently a mathematical model for predicting the 3 d geometry of a landslide dam was presented according to the experimental results and it was verified by the experimental data and 42 historical cases of landslide dams based on the proposed model the predicted 3 d geometry of the tangjiashan landslide dam triggered by the wenchuan earthquake of 2008 was consistent with its actual geometry which confirmed the reliability of the prediction model in practical applications the findings of our study contribute to the establishment of evidence based disaster prevention and mitigation measures for landslide dams

the largest prehistoric landslide in northwestern slovakia chronological constraints of the kykula long runout landslide and related dammed lakes abstract this study deals with the chronology of the largest long runout landslide in the northwesterrn part of the western flysch carpathians kysucke beskydy mts slovakia despite the impossibility of using direct radiocarbon dating method time constraints for the evolution of the landslide were determined on the basis of the dating of various sedimentological geomorphological elements situated on and adjacent to the landslide body the results show that the landslide evolved between 10 3 and 9 0 ka 14 c bp i e in the wider transitional phase between the late glacial lg and the holocene the main mass movement activity took place at the turn of the younger dryas preboreal chronozones whereas retrogressive activity continued up to the preboreal boreal transition radiocarbon dating together with pollen analysis and sedimentology of landslide dammed palaeolakes and colluvial peat bogs revealed almost continuous holocene palaeogeographical records between 10 3 and 3 3 ka 14 c bp periods of enhanced sediment supply to the reservoirs in 9 9 9 0 8 4 8 2 6 9 6 5 and 4 5 ka 14 c bp correlate well with palaeogeomorphic and palaeohydrological records from nearby polish carpathians the study confirms that the lg holocene transition represented a favourable period for the evolution of large landslides not only in glaciated high mountain areas but also in medium high mountains of central europe

bedload to suspended load ratio and rapid bedrock incision from himalayan landslide dam lake record about 5400 cal yr bp a large landslide formed a n400 m tall dam in the upper marsyandi river central nepal the resulting lacustrine and deltaic deposits stretched n7 km upstream reaching a thickness of 120 m 14 c dating of 7 wood fragments reveals that the aggradation and subsequent incision occurred remarkably quickly 500 yr reconstructed volumes of lacustrine 0 16 km 3 and deltaic 0 09 km 3 deposits indicate a bedload to suspended load ratio of 1 2 considerably higher than the 1 10 that is commonly assumed at the downstream end of the landslide dam the river incised a new channel through 70 m of greater himalayan gneiss requiring a minimum bedrock incision rate of 13 mm yr over last 5400 yr the majority of incision presumably occurred over a fraction of this time suggesting much higher rates the high bedload ratio from such an energetic mountain river is a particularly significant addition to our knowledge of sediment flux in orogenic environments 2007 university of washington all rights reserved

stationary planetary waves inferred from windii wind data taken within altitudes 90 120 km during 1991 96 abstract a climatology of stationary planetary waves spws in horizontal winds at latitudes 70 s 70 n and altitudes 90 120 km is obtained from wind imaging interferometer windii green line measurements in december january and march april of 1991 96 the observed solstitial spw fields are relatively stronger and dominated by zonal wavenumber 1 variations in contrast the equinoctial spw fields are weaker and characterized by zonal wavenumber 2 variations the zonal amplitude maxima of 10 25 m s 1 are generally centered at the midlatitudes of 35 40 in both hemispheres around 96 km with the eastward perturbation velocity maxima around 90 e for wavenumber 1 and 60 and 240 e for wavenumber 2 the meridional amplitude maxima are about 5 15 m s 1 and show more variabilities in their latitude height distributions the meridional phases indicated that eliassen palm ep fluxes were downward poleward for the winter maxima vertically varying poleward for the summer maxima and more variable during march apr

seasonal variation of diurnal perturbations in mesopause region temperature zonal and meridional winds above fort collins colorado 40 6 n 105 w 1 on the basis of lidar observations from may 2002 through april 2003 covering both day and night we performed a harmonic analysis to extract the diurnal perturbations in mesopause region temperature zonal and meridional winds over fort collins colorado 40 6 n 105 w binned every 2 months the results were compared to predictions of the 2000 and 2002 versions of global scale wave model gswm00 and gswm02 the diurnal tidal period oscillations showed a mixture of propagating and evanescent trapped modes but the propagating modes dominated for most of the year the agreement in temperature diurnal phases between observation and gswm prediction is marginal on the other hand other than july august meridional winds the observed diurnal phases in both wind components are in good agreement with gswm predictions for most of the altitude range reported the diurnal amplitude predictions of gswm00 were reasonably close to lidar observations while other than january february the gswm02 amplitude prediction overestimated the observations typically by a factor of two we also conducted comparisons on tidal perturbations in zonal wind between radar campaigns and our lidar observations the lidar data agreed reasonably well with the mf radar data from 2000 to 2001 at nearby platteville colorado 40 2 n 104 7 w but showed considerable differences with the data from other midlatitude stations from 1992 to 1993 the dominance of the evanescent mode in the temperature diurnal tidal oscillation during the early winter november and december which reached a peak value at midnight was interesting and anomalous by invoking the more recent data november and december in 2003 as well as the diurnal temperature observations from december 1998 we report that the evanescent trapped diurnal tidal perturbations were robust and persisted from one year to the next

case studies of the mesospheric response to recent minor major and extended stratospheric warmings 1 we have studied the mesospheric response to two recent stratospheric warmings by performing short term forecasts at medium 1 5 and high 0 5 spatial resolution under different gravity wave drag gwd scenarios we validated our models with our high altitude analysis that extends from 0 to 90 km for the minor warming of january 2008 reduced upper level orographic gwd weakened the downward residual circulation and cooled the mesosphere parameterized nonorographic gwd increased the simulated mesospheric cooling for the prolonged major warming of 2006 heavily attenuated orographic gwd led to pronounced cooling near 50 km during the extended phase of this event an unusually strong westerly polar vortex reformed in the lower mesosphere which allowed westward propagating nonorographic gravity waves to reach the mesosphere and break with net westward accelerations of over 50 m s 1 d 1 this in turn forced a strong residual circulation yielding descent velocities over 2 cm s 1 between 65 n and 85 n consistent with previous reports of enhanced downward transport of trace constituents the resulting adiabatic heating as evidenced by the unusually vertically displaced stratopause at 80 km is likely a direct consequence of this enhanced gravity wave driven descent high resolution simulations without parameterized gwd were closer to the analysis than medium resolution simulations with parameterized orographic gwd only but still did not fully simulate the mesospheric thermal response specifically the 80 km temperature enhancement was still underestimated in these simulations this suggests that higher spatial resolution is needed to adequately resolve extratropical gravity wave momentum fluxes

methods for predicting peak discharge of floods caused by failure of natural and constructed earthen dams floods from failures of natural and constructed dams constitute a widespread hazard to people and property expeditious means of assessing flood hazards are necessary particularly in the case of natural dams which may form suddenly and unexpectedly we revise statistical relations derived from data for past constructed and natural dam failures between peak discharge qp and water volume released v0 or drop in lake level d but assert that such relations even when cast into a dimensionless form are of limited utility because they fail to portray the effect of breach formation rate we then analyze a simple physically based model of dam breach formation to show that the hydrograph at the breach depends primarily on a dimensionless parameter kv0 gl 2d7 2 where k is the mean erosion rate of the breach and g is acceleration due to gravity the functional relationship between qp and takes asymptotically distinct forms depending on whether 1 relatively slow breach formation or small lake volume or 1 relatively fast breach formation or large lake volume theoretical predictions agree well with data from dam failures for which k and thus can be estimated the theory thus provides a rapid means of predicting the plausible range of values of peak discharge at the breach in an earthen dam as long as the impounded water volume and the water depth at the dam face can be estimated

the formation and breach of a short lived landslide dam at hsiaolin village taiwan part i post event reconstruction of dam geometry abstract in this paper technologies from multiple disciplines are used to reconstruct the shape of the hsiaolin landslide dam a short lived landslide dam sld that was triggered by typhoon morakot here the formation failure mode and breaching process of this sld are investigated the results indicate that the overtopping time and the debris budget constrained the dam geometry the inferred volume of the hsiaolin landslide dam 15 4 million m3 is much smaller than the actual landslide volume 25 2 million m3 even considering the rock mass dilation and debris entrainment meanwhile a 46 error could be induced if an over simplified equation a function of the dam height length and width is used to calculate the dam volume the saddle of the dam crest which is where overtopping occurred could be used as a reference to measure the dam height and length accordingly the determined dam dimensions of height 44 m length 370 m and width 1500 m are suggested to be the representative geometrical indices that influenced the stability of the hsiaolin landslide dam the flow rate of the dammed river another variable relevant to dam stability was determined from a run off simulation it is suggested that instead of the peak flow before the dam formation the flow rate during the blockage period 2974 m3 s should be used as the training data for building a statistical model for stability predictions finally the low hydraulic gradient at the toe of the dam s surface and the high safety factor of the dam slope indicate that the piping and slope instability were irrelevant to the failure of the hsiaolin short lived landslide dam it is postulated that overtopping about one hour after the blockage dominated the failure process of this heavy rainfall induced landslide dam