rayleigh waves normally incident at a continental boundary summary some results of a study of the propagation of monochromatic rayleigh waves normally incident on the western ocean continent boundary of the iberian peninsula are described this seismological problem is modelled in two dimensions using the finite element method for periods in the range of 1 5 to 60 0s the following results for ocean continent direction of propagation are presented i the estimate of the reflected and transmitted wavefields ii the phase velocity curves for the fundamental mode in the transition zone iii the transmission and reflection coefficients and iv the seismic energy distribution for transmitted and reflected modes experimental data from porto pto a continental station and ponta delgada pda an oceanic station were compared to ascertain the effect on rayleigh wave propagation across the continental margin comparison of the experimental amplitude ratios and transmission factor suggests a thickness of about 4 km for the sediment layer in the western oceanic zone of the iberian peninsula

impacts of age dependent tree sensitivity and dating approaches on dendrogeomorphic time series of landslides different approaches and thresholds have been utilized in the past to date landslides with growth ring series of disturbed trees past work was mostly based on conifer species because of their well defined ring boundaries and the easy identification of compression wood after stem tilting more recently work has been expanded to include broad leaved trees which are thought to produce less and less evident reactions after landsliding this contribution reviews recent progress made in dendrogeomorphic landslide analysis and introduces a new approach in which landslides are dated via ring eccentricity formed after tilting we compare results of this new and the more conventional approaches in addition the paper also addresses tree sensitivity to landslide disturbance as a function of tree age and trunk diameter using 119 common beech fagus sylvatica l and 39 crimean pine pinus nigra ssp pallasiana trees growing on two landslide bodies the landslide events reconstructed with the classical approach reaction wood also appear as events in the eccentricity analysis but the inclusion of eccentricity clearly allowed for more 162 landslides to be detected in the tree ring series with respect to tree sensitivity conifers and broad leaved trees show the strongest reactions to landslides at ages comprised between 40 and 60 years with a second phase of increased sensitivity in p nigra at ages of ca 120 130 years these phases of highest sensitivities correspond with trunk diameters at breast height of 6 8 and 18 22 cm respectively p nigra this study thus calls for the inclusion of eccentricity analyses in future landslide reconstructions as well as for the selection of trees belonging to different age and diameter classes to allow for a well balanced and more complete reconstruction of past events

autumnal precipitation distribution on the southern flank of the alps a numerical model study of the mechanisms during the autumn there are frequent events of heavy precipitation on the southern slopes of the meso scale alpine chain moreover the accompanying climatology exhibits a distinctive spatial distribution with some meso scale regions of enhanced precipitation such as the wet spot in the vicinity of lago maggiore possible mechanisms to account for the observed spatial distribution are established using a heuristic model based approach it is shown using a mesoscale model that the response to a steady horizontally uniform and moisture laden flow impinging upon a comparatively realistic representation of the alpine chain can reproduce both the overall meso scale precipitation distribution and its meso scale sub structure the nature of the simulated flow regime over around or intermediate is sensitive to the strength of the ambient geostrophic flow and its modification in the planetary boundary layer contrariwise the simulated precipitation distribution in the lago maggiore wet spot is comparatively insensitive to the changes in direction of the incident geostrophic flow from south to south west and in strength in the range 10 30 m s 1 although there is a marked change in the structure of the near alpine flow this systematic precipitation enhancement appears to be related to the relative strength and compensating effects of an easterly barrier jet tracking along the zonally elongated part of the alps and an air stream channelled between the maritime alps and the apennines further evidence to the above interpretation of the meso scale precipitation distribution is given with simulations conducted using a smoothed and schematic representation of the alpine chain likewise the sensitivity to the presence of a lago maggiore like indentation of the topography is tested and evidence is provided of a further indentation induced precipitation enhancement at the local scale copyright 2004 royal meteorological society

dynamics in debris flow activity on a forested cone a case study using different dendroecological approaches dendrogeomorphological analyses of trees affected by debris flows have regularly been used to date past events however this method has always been limited to forested cones where trees registered the impact of previous events the minimum age dating of trees growing in the debris deposits can in contrast provide information on the latest possible moment of past activity in this paper we report on results obtained from a combination of these two approaches on a forested cone in the valais alps switzerland a detailed geomorphic map in a scale of 1 1000 served as a basis for the sampling strategy disturbed larix decidua mill and picea abies l karst trees growing in the deposits allowed reconstruction of 49 events between ad 1782 and 2005 as well as the determination of the spatial extent of events in the debris flow channels where survivor trees are missing we selected the oldest post event trees and assessed their age by counting their growth rings missing rings due to lack of center as well as to sampling height were added so as to determine real tree age the combination of the dendrogeomorphological event reconstruction with the assessment of germination dates of successor trees allowed realistic approximation of the minimum time elapsed since the last debris flow activity in 23 of the 29 channels present on the current day cone surface in general channels in the northern part of the cone and those close to the currently active channel generally show signs of sub recent activity with one last overbank sedimentation event in the 1980s whereas signs of debris flow activity are absent from the channels in the outermost part since the late 19th century as a consequence of the deeply incised channel and the stabilization measures undertaken along the banks signs of debris flows are missing in the tree ring record for the past two decades

differentiating past events on a cone influenced by debris flow and snow avalanche activity a dendrogeomorphological approach dendrogeomorphology was used to investigate past events on a cone affected by both debris flows and snow avalanches we report on results of 520 cores from 251 injured larix decidua mill and picea abies l karst trees sampled on the birchbach cone swiss alps detailed analysis of tree ring sequences allowed dating of 561 growth disturbances in individual trees for a 252 yr period extending from 1750 to 2002 which could be attributed to 30 different event years we then localized the position of rows of traumatic resin ducts trds within the tree ring so as to assess the intra seasonal position of damage in agreement with data on the local growth period trds located at the beginning of the new growth ring were considered the result of avalanche impacts that occurred during the dormant season or in earliest earlywood between late october and early may in contrast trd found in late earlywood or within latewood were considered the result of periglacial debris flow activity as these layers of the tree ring are locally formed between july and early october for nine out of the 30 reconstructed event years the intra seasonal timing of trds indicated that reactions must be the result of past snow avalanche activity in 19 other event years trds showed that damage has been caused between july and early october and thus through debris flows in the birchbach torrent finally the spatial patterns of trees showing reactions as a result of particular events were assessed so as to approximate the extent of past debris flows and snow avalanches copyright 2006 john wiley sons ltd

hyperconcentrated flows on a forested alluvial fan of eastern canada geomorphic characteristics return period and triggering scenarios the assessment of the dominant flow type on alluvial fans usually refers to two categories debris flow fans i e sediment gravity flows and fluvial fans i e fluid gravity flows here we report the results of combined morphometric stratigraphic and sedimentological approaches which suggest that hyperconcentrated flows a transitional process rheologically distinct from debris flows and floods and sometimes referred to as debris floods mud floods or transitional debris flows are the dominant fan building process in eastern canada these flows produce transitional facies between those of debris flows which consist of a cohesive matrix supported diamicton and those of river flows which display more distinct stratification the size of the blocks in the channels and the abrasion scars at the base of several trees attest to the high transport capacity of these flows the fan channels are routed according to various obstacles comprised primarily of woody debris that impede sediment transit however these conditions of sediment storage are combined with readily available sediment due to the friable nature of the local lithology tree ring analysis allowed the reconstruction of eight hydrogeomorphic events which are characterized by a return period of 9 25 years for the period 1934 2008 although most of the analyzed events occurred after 1970 historical weather data analysis indicates that they were related to rare hydrometeorological events at regional and local scales this evidence led to the elaboration of weather scenarios likely responsible for triggering flows on the fan according to these scenarios two distinct hydrologic regimes emerge the torrential rainfall regime and the nival regime related to snowmelt processes hydrogeomorphic processes occurring in a cold temperate climate and particularly on small forested alluvial fans of north eastern north america should receive more attention from land managers given the hazard they represent as well as because of their sensitivity to various meteorological parameters copyright 2014 john wiley sons ltd

dating of geomorphological processes using dendrogeomorphological methods abstract the object of this study was to develop methods for investigating recent geomorphodynamics of aggradation processes by dendrogeomorphological analyses of the stems and the roots of partially buried spruces every accumulation process causes growth reactions in the affected trees which is reflected in the growth rings analysis of the growth rings enables us to determine the time and the magnitude of burial yet the critical burial depth which when exceeded causes the death of the tree is 1 6 to 1 9 m the burial of a spruce stem causes the sprouting of adventitious root horizons a single event may cause simultaneous sprouting of up to six root horizons of which the uppermost horizon usually is the strongest one the dating of the onset of sprouting of the oldest adventitious roots among each root system enables one to establish absolute dates of debris flow events with an accuracy 0 to 3 years yet this method is very time consuming the simplest dating method proved to be the determination of burial events by the onset of a pronounced reduction of increment in the stem wood of the affected trees with only one core to be taken of each tree this method therefore allows a spatiotemporal reconstruction of aggradation processes the information recorded on the stem cross section of stem by the growth ring pattern lessens with increasing burial depth though

upstream effects of mesoscale mountains abstract the alpine experiment alpex has revealed that low level air is typically diverted around the alps without reaching the mountaintop in pursuit of an understanding of the physical basis of this phenomenon and of its generality we have explored the characteristics of orographic blocking of a rotating continuously stratified quid as revealed in a simple model problem retaining full nonlinear and transient effects hydrostatic dynamics is assumed and the obstacle is taken to be an infinitely long ridge with height h x the key questions treated are the strength of the upstream deceleration of cross mountain flow and the length scale over which the decelerated region extends by means of scale analysis the controlling parameters are found to be the rossby number ro u fl and the froude number fr nhm u where u is the speed of the oncoming flow f is the coriolis parameter l the mountain half width n the brunt vaisala frequency and hm is the maximum mountain height the scale analysis also

dendrogeomorphic evidence of debris flow frequency and magnitude at mount shasta california debris flow deposits and woody vegetation adjacent to and growing within the channels of whitney bolam mud ash and panthe creeks provide a 300 year record of debris flow frequency at mount shasta dendrochronologic tree ring dating methods for the debris flows proved consistent with available documented records of debris flows nine debris flows not reported in the historic record were documented and dated dendrochronologically the oldest tree ring date for a mudflow was about 1670

unravelling past flash flood activity in a forested mountain catchment of the spanish central system flash floods represent one of the most common natural hazards in mountain catchments and are frequent in mediterranean environments as a result of the widespread lack of reliable data on past events the understanding of their spatio temporal occurrence and their climatic triggers remains rather limited here we present a dendrogeomorphic reconstruction of past flash flood activity in the arroyo de los puentes stream sierra de guadarrama spanish central system we analyze a total of 287 increment cores from 178 disturbed scots pine trees pinus sylvestris l which yielded indications on 212 growth disturbances related to past flash flood impact in combination with local archives meteorological data annual forest management records and highly resolved terrestrial data i e lidar data and aerial imagery the dendrogeomorphic time series allowed dating 25 flash floods over the last three centuries with a major event leaving an intense geomorphic footprint throughout the catchment in 1936 the analysis of meteorological records suggests that the rainfall thresholds of flash floods vary with the seasonality of events dated flash floods in the 20th century were primarily related with synoptic troughs owing to the arrival of air masses from north and west on the iberian peninsula during negative indices of the north atlantic oscillation the results of this study contribute considerably to a better understanding of hazards related with hydrogeomorphic processes in central spain in general and in the sierra de guadarrama national park in particular

spatial and temporal analysis of mass movement using dendrochronology tree growth and inclination on sloping land is affected by mass movement suitable analysis of tree growth and tree form can therefore provide considerable information on mass movement activity this paper reports a new automated method for studying the temporal and spatial aspects of mass movement activity ringwidth data from only a few cores per tree are required the method uses filtering techniques and statistical time series analysis preliminary results for two landslides in the barcelonnette area of the french alps show a relative stability of movement activity over the last hundred years no trend and short periodicity six to seven year periods of mass movement activity the advantages of the method over other mostly visual methods are its clearness flexibility repeatability and rapidity however further testing is needed to examine its reliability

sediment un balance budget in a high gradient stream on flysch bedrock a case study using dendrogeomorphic methods and bedload transport simulation abstract detailed quantification of material supply into stream channels is crucial for determining sediment un balance budget during flood events unfortunately existing quantification methods require long term field monitoring otherwise there is an insufficient amount of usable data in this study we introduce a new approach based on dendrogeomorphic methods to determine the volume of material supply generated from flysch high gradient stream bank failures this approach was supplemented by 1d sediment transport modelling using a tomsed model we analysed 138 cross sections from the roots of predominantly broad leaved trees which were exposed in bank failures from different floods using the spatial position of the roots and dating the exposure time we determined the volume of material supply into the channel during the last flood in 2010 in channel sediment transport was analysed on 14 cross sections and the channel sediment thickness was estimated using the geophysically based ert electrical resistivity tomography method the total volume of material loss during the 2010 flood within the study area according to the tomsed model was found to be at least 300 m3 this means that the calculated total volume of sediment supply resulting from bank failures during the flood 63 9 m3 based on dendrogeomorphic methods was significantly lower than the calculated bedload transport for the entire study area this finding implies that contemporary sediment sources cannot adequately cover the transport capacity during high magnitude flood events and in general in channel erosion processes prevail

mesoscale simulation of supercritical subcritical and transcritical flow along coastal topography abstract a mesoscale atmospheric model is used to address the characteristics of stratified flow bounded by a side wall along a varying coastline initial froude number values are varied through alteration of marine inversion strength permitting examination of supercritical subcritical and transcritical flow regimes encountering several coastal configurations consistent with shallow water models sharp drops in boundary layer depth and flow acceleration occur in flow rounding convex bends however significant flow response occurs in the stratified layer aloft which is unexplained by conventional shallow water theory the strongest flow acceleration occurs in the transcritical case while regardless of inversion strength the deformation of the isentropes aloft shows general structural similarity advection of horizontal momentum is an important component of the horizontal force balance a simulation having several coastline bends exhibits a detached oblique hydraulic jump upwind of a concave bend t

how different are the results acquired from mathematical and subjective methods in dendrogeomorphology insights from landslide movements abstract knowledge of past landslide activity is crucial for understanding landslide behaviour and for modelling potential future landslide occurrence dendrogeomorphic approaches represent the most precise methods of landslide dating where trees annually create tree rings in the timescale of up to several hundred years despite the advantages of these methods many open questions remain one of the less researched uncertainties and the focus of this study is the impact of two common methods of geomorphic signal extraction on the spatial and temporal results of landslide reconstruction in total 93 norway spruce picea abies l karst trees were sampled at one landslide location dominated by block type movements in the forefield of the orlicke hory mts bohemian massif landslide signals were examined by the classical subjective method based on reaction compression wood analysis and by a numerical method based on eccentric growth analysis the chronology of landslide movements obtained by the mathematical method resulted in twice the number of events detected compared to the subjective method this finding indicates that eccentric growth is a more accurate indicator for landslide movements than the classical analysis of reaction wood the reconstructed spatial activity of landslide movements shows a similar distribution of recurrence intervals ri for both methods the differences maximally 30 of the total ri ranges in results obtained by both methods may be caused by differences in the ability of trees to react to tilting of their stems by a specific growth response reaction wood formation or eccentric growth finally the ability of trees to record tilting events by both growth responses in their tree ring series was analysed for different decades of tree life the highest sensitivity to external tilting events occurred at tree ages from 70 to 80 years for reaction wood formation and from 80 to 90 years for eccentric growth response this means that the ability of p abies to record geomorphic signals varies with not only eccentric growth responses but also with age

frequency and spread of debris floods on fans a dendrogeomorphic case study from a dolomite catchment in the austrian alps growth disturbances in tree ring series have been regularly used to date debris flow events in mountain environments in contrast no studies are available to date that have reconstructed debris floods by means of dendrogeomorphology therefore the aim of this study was to determine the event frequency and the spread of debris floods in the gratzental tyrol austria the analysis of growth disturbances in the tree ring series of 227 picea abies l karst and larix decidua mill allowed the reconstruction of 37 events for the last 200 years the lateral spread and preferable avulsion locations of reconstructed debris flood events were assessed based on the dating of the events and the spatial position of trees affected by an event on the fan results show that the gratzentalbach preferentially avulsed to the east but affected trees were evenly spread over the fan reconstructed data illustrates the high potential of dendrogeomorphology for hazard assessment of debris floods

geomorphic coupling between hillslopes and channels in the swiss alps the coupling relationships between hillslope and channel network are fundamental for the understanding of mountainous landscapes evolution here we applied dendrogeomorphic methods to identify the hillslope channel relationship and the sediment transfer dynamics within an alpine catchment at the highest possible resolution the schimbrig catchment is located in the central swiss alps and can be divided into two distinct geomorphic sectors to the east the schimbrig earth flow is the largest sediment source of the basin while to the west the rossloch channel network is affected by numerous shallow landslides responsible for the supply of sediment from hillslopes to channels to understand the connectivity between hillslopes and channels and between sources and sink trees were sampled along the main rossloch stream on the schimbrig earth flow and on the rossloch depositional area geomorphic observations and dendrogeomophic results indicate different mechanisms of sediment production transfer and deposition between upper and lower segments of the channel network in the source areas upper part of the rossloch channel system sediment is delivered to the channel network through slow movements of the ground typical of earth flow shallow landslides and soil creep contrariwise in the depositional area lower part of the channel network the mechanisms of sediment transfer are mainly due to torrential activity floods and debris flows tree analysis allowed the reconstruction of periods of high activity during the last century for the entire catchment the collected dataset presents a very high temporal resolution but we encountered some limitations in establishing the source to sink connectivity at the catchment wide scale despite these uncertainties for decennial timescales the results suggest a direct coupling between hillslopes and neighbouring channels in the rossloch channel network and a de coupling between sediment sources and sink farther downstream with connections possible only during extraordinary events

deep orographic storms over the sierra nevada part i thermodynamic and kinematic structure abstract two deep orographic storms were documented over the sierra nevada with an instrumented aircraft and with a single doppler radar in both storms the geographic winds were normal to the barrier with speeds of 15 to 30 m s 1 because of blocking the measured wind component normal to the barrier was substantially less than the geostrophic wind component especially below barrier crest height in the very stable case a barrier jet was present below 1 km agl and had peak winds of 28 m s 1 in the slightly stable case a barrier jet was present at 1 km agl and had peak winds of 21 m s 1 other than the speed and altitude of the barrier jet the other measured characteristics of the airflow and thermal fields were rather similar between these two storms the forced ascent of stable air plus the diabatic process of melting caused the isotherms to descend near the barrier the barrier jet can be expressed by the thermal wind relation and is therefore a quasi geostrophic phenomenon the derived vertical

the role of trees in the geomorphic system of forested hillslopes a review abstract forested hillslopes form a special geoecosystem an environment of geomorphic processes that depend strongly on forest ecology including the growth and decay of trees changes in structure disturbances and other fluctuations hence the following various functions of trees are reviewed here their role in both biomechanical and biochemical weathering as well as their importance for the hillslope geomorphic subsystem and for transport of soil material via tree uprooting and root growth special attention is paid to tree uprooting a process considered the most efficient and most frequent biogeomorphological indicator of bio physical activity within forest in complex terrain trees have varied implications for soil formation in different environments boreal to tropical forests and altitudes in this paper an attempt has been made to emphasize how trees not only modulate geomorphic processes but also how they act as a direct or indirect agent of microrelief formation the most striking example of which being widespread and long lasting pit and mound microtopography based on the analyzed literature it seems that some problems attributed to forest ecology can have a fundamental effect on forested hillslope dynamics a relationship which points to the need for its integration and interpretation within the field of geomorphology the biology of individual trees has a key influence on the development of e g rock faces weathering front migration and changes in the soil biomantle within upper and lower forest belts additionally forms and sediments depend largely on the horizontal and vertical extent volume and structure of root systems as well as on active processes taking place in the root zone and rhizosphere furthermore although trees to a large extent stabilize slope surfaces their presence can also have a dual effect on slope stability due to tree uprooting a process which in some circumstances can trigger mass movements e g debris avalanches so far several attempts at quantifying the influence of trees on slopes have been made via the use of mathematical equations enabling researchers to calculate 1 the root plate volume of uprooted trees 2 the amount of soil displacement due to tree root growth and 3 rates of erosion sedimentation and soil creep in light of the reviewed literature the most urgent issue appears to be the need for a thorough study of the interactions and feedbacks occurring between trees and geomorphic systems e g soil mixing and biotransport by trees in different climate zones altitudes and time frames especially in terms of the development of forest ecosystems during the holocene

anomalous surface waves associated with deep earthquakes generated at an ocean ridge summary broad band seismograms observed at regional distances from deep earthquakes display large amplitude rayleigh and love waves with a predominant period of about 20 s although deep earthquakes in laterally homogeneous structures do not generate such surface waves since the propagation direction of the surface waves inferred from particle motion is approximately radial and the group velocity of the surface waves observed at each station is similar it can be assumed that the surface waves have travelled close to the great circle paths back projection allows us to determine the region in which these surface waves are generated manyof the zones from which the surface waves appear to originate are located close to the norfolk ridge where crustal structure has strong lateral heterogeneity this suggests that the surface waves are generated by the interaction of body waves from the deep earthquakes with this strongly heterogeneous crustal structure in order to investigate the eiect of such heterogeneity in crustal structure on seismic wave elds we have modelled the p sv wave eld using a pseudospectral method the results show that surface waves such as those observed can be generated by ridge structures and indicate that sedimentary layer thickness plays a very important role we suggest that such unexpected surface waves from deep earthquakes may prove useful for delineating heterogeneity in shallow structure

dendrogeomorphic approaches for identifying the probable occurrence of debris flows and related torrential processes in steep headwater catchments the hrubý jesenik mountains czech republic abstract culminating parts of mid mountain ranges in central europe are interwoven by a network of high gradient streams these parts together with the surrounding slopes form a coupling system in which hazardous geomorphic processes such as landslides debris flows or flash floods can occur in the case of the hrub jesenik mountains eastern sudetes czech republic we present an evaluation of the debris flows and related torrential processes in the high gradient streams of the selected catchment based on dendrogeomorphic methods in addition to the classical dendrogeomorphic approaches we refined the procedure of identifying certain and probable events using new weighted indexes for event reconstruction additionally because of the steep narrow channels without a characteristic accumulation cone a new spatial approach is defined based on the spacing of disturbed trees for each event random distribution or clustering and location of disturbed trees in an individual section of the valley floor using kernel density analysis for each event and calculating the particular grids in arcgis software we are able to describe the spatial reach and probable nature of an event debris flow or hyperconcentrated flow dendrogeomorphic analysis of 397 sampled trees predominantly coniferous trees revealed 24 torrential events 15 certain nine probable since 1928 with peaks in 1991 1997 and 2010 according to index values in addition the spatial distribution of disturbed trees grouped in clusters in these years indicates debris flow events in the upper parts of the catchment it seems that new dendrogeomorphic approaches should be valuable in remote steep headwater catchments where several types of processes affect the valley floors

the changing ability of norway spruce p abies to record hydro geomorphic processes based on the age and diameter of the tree stem a dendrogeomorphic approach dendrogeomorphic reconstructions of debris flows and related hydro geomorphic processes i e debris floods and flash floods are widely used in territories with incomplete chronologies and potential future hazards in recent years the tree ring analysis of disturbed trees affected by dangerous geomorphic processes has developed into a discipline with sophisticated methodical approaches and with annual up to monthly accuracy of dating field sampling strategies are based on various ranges of sample depth i e different amounts of sampled trees of different age structures the age and diameter of trees influence the ability of trees to respond to geomorphic processes therefore we investigate age dependent and diameter dependent tree sensitivity our study for the first time addresses the sensitivity to hydro geomorphic processes in detail we tested 462 individuals of norway spruce picea abies l karst a very common species used in the dendrogeomorphic reconstructions in the apical part of the medium high mountains where there is widespread occurrence of debris flows and debris floods the tree sensitivity analysis was performed based on the position of growth disturbances within the increment cores of trees original age and original diameter of the tree before the tree was affected p abies shows very high tree sensitivity in the first two decades of the tree lifespan with increasing age and diameter trees are less sensitive recorders of debris flows floods moreover the intensity of growth disturbances significantly decreases with tree age mature trees 51 120 years record the geomorphic events mainly through abrupt growth changes suppression and release and tangential rows of traumatic resin ducts in contrast scars the onset of reaction wood and traumatic resin ducts are dominant growth disturbances in young thin trees 11 30 years diameter 0 15 cm different occurrences of particular growth disturbances as well as the different age and diameter dependent sensitivities emphasize the need for the inclusion of new variable that will take into account the amount of sensitive trees for each year after that adequate mixture of sampled tree i e mixture of age classes which is necessary for the completeness of debris flow flood chronologies could be balanced regarding their sensitivity

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

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

debris flow activity and snow avalanches in a steep watershed of the valais alps switzerland dendrogeomorphic event reconstruction and identification of triggers debris flows and snow avalanches are common processes in the headwaters of steep watersheds worldwide in forested areas dendrogeomorphic analyses of trees affected by debris flows and snow avalanches have regularly been used to date past events previous studies have however almost never focused on both processes at once as snow avalanche impacts cannot easily be distinguished from debris flow scars in a similar way tree ring studies have often been limited to conifers and sites colonized with broad leaved forests have been widely disregarded we report on a case from the valais alps switzerland where past debris flow and snow avalanche activity was dated with intraseasonal precision using different broad leaved and conifer trees in total the analysis of 171 cores 34 wedges and 11 crosssections from 93 trees allowed identification of 20 debris flow and 3 snow avalanche events between a d 1930 and 2008 results also indicate that some of the events would have been missed without the sampling of broad leaved trees

mass movements and tree rings a guide to dendrogeomorphic field sampling and dating abstract trees affected by mass movements record the evidence of geomorphic disturbance in the growth ring series and thereby provide a precise geochronological tool for the reconstruction of past activity of mass movement the identification of past activity of processes was typically based on the presence of growth anomalies in affected trees and focused on the presence of scars tilted or buried trunks as well as on apex decapitation for the analyses and interpretation of disturbances in tree ring records in contrast clear guidelines have not been established with largely differing or no thresholds used to distinguish signal from noise at the same time processes with a large spatial footprint e g snow avalanches landslides or floods will likely leave growth anomalies in a large number of trees whereas a falling rock would only cause scars in one or a few trees along its trajectory based on the above considerations we examine issues relating to the interpretation and dendrogeomorphic dating of mass movements particular attention is drawn to sampling in terms of sample distribution across a study site the actual selection of trees as well as to sample size i e number of trees sampled based on case studies from snow avalanche debris flow and landslide sites we demonstrate that thresholds can indeed improve dating quality and at the same time minimize noise in time series we also conclude that different thresholds need to be used for different processes and different periods of the reconstruction especially for the early stages of the reconstruction when the number of potentially responding trees will be much smaller this paper seeks to set standards for dendrogeomorphic fieldwork analysis and interpretation for different processes of mass movements

application of eccentric growth of trees as a tool for landslide analyses the example of picea abies karst in the carpathian and sudeten mountains central europe abstract a method based on dendrochronology was developed to analyse the spatial and temporal variability of landslide activity as an alternative and complement to methods such as field monitoring of landslide relief aerial photography and remote sensing the method involves a feature of wood anatomy tree ring eccentricity which is used in the dating procedure the degree of eccentricity is used as an indicator of the intensity of the mechanical stress affecting a tree stem in a certain year the objective was to develop a mathematical indicator of tree ring eccentricity for dating the recent dynamics of landslides a method presented in the paper is also designed for practical application in detecting initial landslide activity and allowing the determination of triggering factors the index developed is dimensionless and for this reason is independent of the absolute ring variations of the single trees analysed using reference results from stable slopes as thresholds in dating an objective method for detecting landslide activity was developed the method was used in the carpathian and sudeten mountains on three landslides with different sizes and geological settings it was found that the values of eccentricity index in trees growing on stable slopes rarely exceed at 100 while in trees growing on landslides they can reach hundreds to thousands per cent a spatial analysis of the eccentricity values conducted for a single landslide has revealed that the method developed allows one to identify areas of landslide activation and to observe the down or upslope propagation of instability a comparison of the results obtained regarding the precipitation record has shown that by using the method that has been developed it is possible to detect past mass movement episodes caused by heavy long term rainfall as well as by single short lasting but torrential downpours

on the incidence of debris flows from the early little ice age to a future greenhouse climate a case study from the swiss alps 1 tree ring based reconstructions of 123 debris flow events in a case study area of the swiss alps since ad 1570 show enhanced activity during the wet periods 1864 1895 following the last lia glacier advance and in the early decades of the 20th century in contrast comparably low activity can be observed since 1995 with only one event recorded from the reconstructions and based on rcm simulations there are indications that debris flow frequencies might continue to decrease in a future climate as precipitation events are projected to occur less frequently in summer but become more common in spring or fall

waveform inversion for lateral heterogeneities using multimode surface waves summary we propose a waveform inversion scheme that can be used to invert strong structural heterogeneities the method is based on a ray approximation for surface waves strong structural lateral variations are modelled by vertical discontinuities therefore a geologically heterogeneous region is partitioned into a number of lateral homogeneous subregions synthetic seismograms are calculated by modal summation over incident and transmitted modes with this method the complete waveforms of surface waves including mode cross branch coupling multipathing and scattering are considered in the inversion we test the method with several geophysically realistic structural models an example of waveform inversion for real data a wave path across the iberian peninsula and the oceanic structure off the french coast owing to the gibraltar earthquake ms 5 7 is presented the method allows us to obtain the information represented by different set of structures along the same source receiver minor arc through which the waves have propagated the method is applicable to different models of lateral heterogeneity in its present development it is most appropriate for inverting structures around tectonic scenarios such as continental margins grabens and discontinuities between major plates

reconstructing spatio temporal patterns of debris flow activity using dendrogeomorphological methods debris flows are a major threat in many parts of the alps where they repeatedly cause severe damage to infrastructure and transportation corridors or even loss of life nonetheless the spatial behavior of past debris flow activity and the analysis of areas affected during particular events have been widely neglected in reconstructions so far it was therefore the purpose of this study to reconstruct spatio temporal patterns of past debris flows on a forested cone in the swiss alps bruchji torrent blatten valais the analysis of past events was based on a detailed geomorphic map 1 1000 of all forms related to debris flows as well as on tree ring series from 401 heavily affected trees larix decidua mill and picea abies l karst growing in or next to deposits the samples were analyzed and growth disturbances related to debris flow activity assessed such as tangential rows of traumatic resin ducts the onset of reaction wood or abrupt growth suppression or release in total 960 growth disturbances were identified in the samples belonging to 40 different event years between a d 1867 and 2005 in addition the coupling of tree ring data with the geomorphic map allowed reconstruction of eleven formerly active channels and spatial representation of individual events based on our results we believe that before 1935 debris flows preferentially used those channels located in the western part of the cone whereas the eastern part of the cone remained widely unaffected the spatial representation of the 40 events also allowed identification of five different spatial patterns for debris flows at the study site 2006 elsevier b v all rights reserved

a regional reconstruction of debris flow activity in the northern calcareous alps austria dendrogeomorphic dating of historical debris flow events is a highly valuable tool for improving historical records in the field of natural hazard management previous dendrogeomorphic investigations generally have focused on case studies of single torrents however regional investigations may offer a more accurate reconstruction of regional patterns of activity and therefore may have an advantage over individual cases the aim of the study is to provide a regional reconstruction of debris flow events for a site in the northern calcareous alps of western austria gamperdonatal vorarlberg and to document spatial and temporal morphological changes in individual and neighboring torrents analysis of 442 trees 268 pinus mugo ssp uncinata 164 picea abies and 10 abies alba allowed identification of 579 growth disturbances corresponding to 63 debris flow events since a d 1839 the majority of growth disturbances were in the form of growth suppression or release 76 owing to the nature of both the deposited material and the process characteristics regional patterns of event frequency indicated a paucity of activity in the early to mid twentieth century and increased activity since a d 1948 whereby large events were followed by subsequent years of continued activity of smaller magnitude patterns of frequency could be attributed primarily to spatiotemporal changes in channel morphology but may also be reflective of changes in transport conditions within the valley this study provides the first regional investigation in the austrian alps and contributes to the documentation of tree responses to geomorphic disturbances in calcareous material

structure of the upper mantle in the northeastern atlantic close to the azores gibraltar ridge from surface wave and body wave observations abstract phase velocities of teleseismic rayleigh waves have been measured in the central north atlantic on both sides of the azores gibraltar ridge agr by means of a specially designed long period station network the dispersion data obtained were regionalized and then subjected to a hedgehog inversion which gives a set of upper mantle models compatible with the observational data within specified error bounds reasonable model solutions were selected by using regional body wave observations such as p n and s n wave velocities determined from earthquakes along the agr the s itn velocities measured indicate that the shear wave velocity in the mantle part of the lithosphere is much higher on the northern side of the agr strongly negative p wave residuals in this area indicate faster seismic propagation than implied by the jeffreys bullen travel time tables while propagation is much slower in the gulf of cadiz area furthermore the residuals show a clear difference for paths through oceanic and continental domains and suggest that the transition between these two domains extends much further into the ocean on the southern side of the agr than on the northern side the proposed model for the structure of the upper mantle in that region shows that there exists a pronounced velocity contrast across the agr thickening of the lithospheric plate with increasing plate age is indicated to the south of the ridge the greatest thickness is reached close to the continental margin within a zone about 500 km wide whose velocity close to the canary islands and madeira is significantly lower probably due to the well known volcanic activity there these observations together with the travel time residuals reveal that this zone seems to be of a transitional nature somewhere between a continental and oceanic structure

approximation of surface wave mode conversion at a passive continental margin by a mode matching technique summary at a continental margin sharp structural changes cause strong lateral heterogeneity in s wave velocity p wave velocity and density therefore mode conversion of surface wave modes is expected passive continental margins may be modelled by vertical discontinuities mode conversion is then expressed in terms of re ection and transmission coe cients long period seismograms are calculated by mode summation over incident re ected and transmitted modes re ection and transmission coe cients for surface waves are approximated by a mode matching technique that is adapted to a spherical earth model an orthogonality relation for surface wave eigenfunctions on a spherical earth is given that allows one to simplify the linear system of equations for the determination of re ection and transmission coe cients transmission of fundamental love and rayleigh modes is strongly in uenced by upper crustal heterogeneity for frequencies larger than 40 hz for fundamental love modes and larger than 60 hz for fundamental rayleigh modes mode conversion to neighbouring modes can be strong but mode conversion is not necessarily con ned to neighbouring modes fundamental modes in particular can couple with more distant higher modes in synthetic seismograms calculated for epicentral distances up to 40 0 mode conversion between higher modes and fundamental modes results in shear coupled rayleigh waves

geomorphology and vegetation on hillslopes interactions dependencies and feedback loops article i nfo the linkages between vegetation and hillslope geomorphology have been the subject of serious study for years but traditionally ecologists and geomorphologists have viewed these interactions as unidirectional on the one hand botanists and landscape ecologists have examined the effects of hillslope features processes and materials on vegetation structure composition and dynamics focus has been placed on the effects of topography elevation slope angle slope aspect edaphic factors rock type and geomorphic disturbance mass movement snow avalanches land surface erosion on the other hand geomorphologists have traditionally treated vegetation as an independent variable that affects landforms and sediment routing at limited spatial temporal scales hillslope vegetation and landforms however co evolve one key is to understand the role of time disturbances and feedbacks that link vegetation and geomorphology on hillslopes the effects of vegetation on mass movement and landscape evolution are being studied in new ways many regional studies claim that vegetation becomes less relevant as one moves to larger and larger watershed scales but ecoregion analysis offers a contrasting view whereas these efforts have produced vehicles of understanding that are simple ordered unified and harmonious they often do not reflect the complexity that leads to multiple possible outcomes place dependent results recent perspectives focus on the two way interplay between vegetation and hillslope geomorphology where establishing cause and effect linkages is made difficult by confounding factors spatial temporal scale location convergence divergence nonlinearity thresholds feedbacks vegetation and geomorphology interactions are controlled by a combination of global factors independent of time and place and the local environmental history continued refinement of fine scale deterministic models should be encouraged but the ability to translate these results to larger scales needs to be explored at large scales future research especially those with predictive modeling as the goal should concentrate on how to increase the generality of concepts and models and should seek to reduce the number of variables and factors considered

frequency of debris flows and their relation with precipitation a case study in the central alps italy abstract debris flows are very important and widespread mass movements and represent a remarkable geomorphological hazard this research deals with debris flows in an alpine environment studied using dendrogeomorphological dating techniques outlining their relation with precipitation and analysing possible changes in their frequency and intensity over time the study area is the upper valle del gallo northern italy a typical high mountain environment dominated by mass wasting processes where many debris flow fans occupy the valley bottom dendrogeomorphological research was conducted on twelve of these fans and two channels located on slopes tree growth anomalies abrasion scars compression wood and abrupt growth changes were used as dating methods two hundred and thirty nine debris debris flow events between 1875 and 2003 were dated using 757 trees pinus montana mill analysis between dated events and precipitation suggests that debris flows in the study area could be triggered by 20 30 mm of rain concentrated in a few hours the debris flow frequency tends to increase gradually but the highest value seems to have occurred in the period 1974 1983 this trend agrees with the historical occurrence of flooding events in northern italy as inferred by literature and with similar studies conducted in the swiss alps the results of this research are intended as a contribution for understanding the response of geomorphological processes to climatic changes

tree age control on reconstructed debris flow frequencies examples from a regional dendrogeomorphic reconstruction in the crimean mountains the crimean mountains ukraine are renowned for the highest occurrence of debris flows along the northern coast of the black sea but information on their origin frequency and triggers is widely lacking this study reconstructs a regional time series of debris flows in eight catchments located on the slopes above yalta dendrogeomorphic analyses were performed on 1122 increment cores selected from 566 black pines pinus nigra ssp pallasiana with clear signs of external damage induced by past debris flow activity the trees sampled were divided into old and young trees the sample contains 361 young trees with post 1930 innermost rings and 205 old trees with pre 1930 germination dates the two groups of trees were analyzed separately to identify possible age effects in the reconstructed debris flow series and to assess the ability of p nigra to record geomorphic disturbances over time we date a total of 215 debris flows back to ad 1701 and observe a mean decadal frequency of 6 9 events with a peak in activity during the 1940s 20 events the young trees record an increase in debris flow activity over the last 70 years whereas the frequency of events remained fairly constant in the old trees for the same period by contrast the formation of reaction wood became increasingly scarce with increasing tree age whereas the occurrence of abrupt growth suppression increased copyright 2014 john wiley sons ltd

frequency predisposition and triggers of floods in flysch carpathians regional study using dendrogeomorphic methods abstract dangerous overland flood events in the foothills of the flysch carpathians often result from a cumulative effect of floods in high gradient channels detailed understanding of the origin of floods in these catchments is only possible if the occurrence of these floods in the past has thoroughly been studied yet no gauging stations can be found in the local catchments the reconstruction of floods in ungauged catchments has so far been performed using dendrogeomorphic methods stems or branches floating in the floodwater can affect stems or roots of living trees and injure them trees are able to record these signals in their tree ring series within the flysch carpathians the floods have been reconstructed based on the analysis of 446 cross sections from scarred tree roots and 192 increment cores from the stems of affected trees in the studied area of 10 catchments surrounding the highest peak of the moravskoslezske beskydy mts the lysa hora mt the dating comprised 64 floods in different catchments in 28 flood years for the maximal period of 1883 2012 most catchments nine out of ten were affected by floods in the year 1997 above average frequency of floods has also been found for the last two decades namely thanks to numerous samples taken from young tree roots that revealed more flood impacts by contrast although tree ring series enabled the reconstruction of a longer time series they only recorded the major floods the most significant factor affecting the frequency of floods is the orientation of catchments toward the prevailing wind direction positive influence of catchment gradient on flood frequency and higher occurrence of floods in the period of intensive slope deforestation show that the floods of the 1950s to 1970s could have a character of flash floods this assumption is also supported by the character of probable triggering precipitation high magnitude short duration precipitation of this period generally the most frequent probable triggering factor is however an above average seven day precipitation amount which indicates along with the positive relation between the catchment extent and flood frequency that a majority of floods hardly ever occur as an immediate response to one day precipitation extremes fast spring melting of thick snow cover plays an insignificant role in floods in the studied medium high mountains

fossil and recent debris flows in medium high mountains moravskoslezske beskydy mts czech republic abstract the significance of debris flows for the morphogenesis of the medium high mountains of central europe has long been neglected herein we provide evidence from the moravskoslezske beskydy mountains flysch western carpathians czech republic where fossil pleistocene debris flow events in spite of their low recent activity were important erosion and accumulation agents in shaping the mountainous terrain geomorphological and sedimentological analyses helped to differentiate between two classes of debris flow deposits deposits of the 1st class are relatively voluminous contemporary terraced landforms which originated in the pleistocene transport limited conditions recent activity of debris flows presented by the 2nd class accumulations is characterized by the presence of low magnitude events mostly originated during the reworking of older diamictons the inheritance of large volumes of old debris flow diamictons in steep mountainous terrain is the evidence of slow erosional transformation of the last glacial landforms pointing to the fact that recent topography of the mountains is not in full equilibrium with contemporary climatic and environmental conditions

counting scars on tree stems to assess rockfall hazards a low effort approach but how reliable rockfall is a widespread and hazardous process in mountain environments but data on past events are only rarely available growth ring series from trees impacted by rockfall were successfully used in the past to overcome the lack of archival records dendrogeomorphic techniques have been demonstrated to allow very accurate dating and reconstruction of spatial and temporal rockfall activity but the approach has been cited to be labor intensive and time consuming in this study we present a simplified method to quantify rockfall processes on forested slopes requiring less time and efforts the approach is based on a counting of visible scars on the stem surface of common beech fagus sylvatica l data are presented from a site in the inn valley austria where rocks are frequently detached from an 200 m high south facing limestone cliff we compare results obtained from i the classical analysis of growth disturbances in the tree ring series of 33 norway spruces picea abies l karst and ii data obtained with a scar count on the stem surface of 50 f sylvatica trees a total of 277 rockfall events since a d 1819 could be reconstructed from tree ring records of p abies whereas 1140 scars were observed on the stem surface of f sylvatica absolute numbers of rockfalls and hence return intervals vary significantly between the approaches and the mean number of rockfalls observed on the stem surface of f sylvatica exceeds that of p abies by a factor of 2 7 on the other hand both methods yield comparable data on the spatial distribution of relative rockfall activity differences may be explained by a great portion of masked scars in p abies and the conservation of signs of impacts on the stem of f sylvatica besides data indicate that several scars on the bark of f sylvatica may stem from the same impact and thus lead to an overestimation of rockfall activity

debris flows in glacier national park montana geomorphology and hazards abstract debris flows are one of the many active slope forming processes within glacier national park montana most debris flow landforms exhibit classic morphology with a distinct failure scarp incised channel channel levees and toe deposits that often develop a lobate form the precambrian metasediments that dominate glacier national park s geology weather into angular clasts that range in size from platy gravels to boulders classic debris flows occur in areas where the topographic expression provides a debris source from cliff faces and an accumulation of regolith often in the form of talus slopes many of these debris flows have long runout zones and can travel many hundreds of meters often they cross hiking trails or roads including the main east west highway going to the sun road debris flows impacting the road have resulted in several near fatalities and hikers have been forced to cross active debris flows to reach safe ground the magnitude of debris flows varies between high magnitude channel incising events and low magnitude channel filling and or reworking events the frequency of debris flow events is irregular and appears to be controlled by the hydrology of triggering storms and antecedent moisture conditions not by the debris supply as a result debris flow magnitude is not a function of frequency but is more closely related to the characteristics of antecedent conditions and individual storms

tree ring eccentricity in the dendrogeomorphic analysis of landslides a comparative study abstract the chronological aspects of landslide research are of great interest regarding the hazard assessment of landslide triggers dendrogeomorphic methods provide a good ratio of chronology length and dating resolution an alternative to the standard dendrogeomorphic approaches used in landslide research based on reaction wood analysis a reaction to stem inclination is the analysis of tree ring eccentricity this study tests three frequently used dendrogeomorphic approaches based on tree ring eccentricity and verifies the results by comparing them with the results obtained by the standard dendrogeomorphic expert approach in total 125 individual fagus sylvatica l trees growing on the block type landslide of lipova stra in the foothills of the orlicke hory mts central europe were sampled and used for the analysis the first tested approach identifies landslide signals based on the analysis of mean eccentricity values from two moving windows the second tested approach determines landslide signals from a series of eccentricity values based on the use of an eccentricity threshold from reference trees the last tested approach organizes the eccentricity values into categories and identifies landslide signals based on the defined temporal patterns of the individual categories the limitations of each approach are revealed and recommendations for increasing the robustness of each approach are presented moreover the sensitivity of f sylvatica trees to landslide signals was tested using each approach the obtained results suggest the need for a specific sampling design regarding tree age for each tree ring eccentricity based approach