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

reconstructing recent landslide activity in relation to rainfall in the llobregat river basin eastern pyrenees spain abstract a chronology of recent landslides in the upper basin of the llobregat river eastern pyrenees has been reconstructed from technical reports field reconnaissance and dendrogeomorphological analysis the precipitation conditions responsible for triggering and reactivating landslides have been deduced by analysis of rainfall records from two rain gauges located in the area two different rainfall patterns relate to landslide occurrence i without antecedent rainfall high intensity and short duration rains trigger mostly debris flows and shallow slides developed in colluvium and weathered rocks a rainfall threshold of around 190 mm in 24 h initiates failures whereas more than 300 mm in 24 48 h are needed to cause widespread shallow landsliding ii with antecedent rain moderate intensity precipitation of at least 40 mm in 24 h reactivates mudslides and both rotational and translational slides affecting clayey and silty clayey formations in this case several weeks and 200 mm of precipitation are needed to cause landslide reactivation dendrochronological analysis shows that landslide activity in the eastern pyrenees was relatively low between 1926 and 1959 but has since increased significantly with reactivation now occurring about every 3 years

can tree tilting be used for paleoflood discharge estimations paleoflood hydrology typically deals with the reconstruction of floods in ungauged and poorly gauged basins by combining different sources of indirect evidence botanical indicators have been used repeatedly in the past mostly through the study of scars in trees or germination dates of plants on newly created surfaces in this paper we test the hypothesis that the inclination of trees as induced by floods can provide information on flood magnitude and that this source of information can therefore be used for flood reconstructions we used a mechanical root plate rotational stiffness model in three gauged river reaches in central spain to test our hypothesis and combine approaches typically applied in dendrogeomorphic dendrometric mechanical structure and hydraulic research results show a correlation between modeled and observed deformation at the stem base of trees induced by floods coefficient of correlation 0 58 for all observations however they also point to a clear underestimation of peak discharge reconstructions we used different efficiency criteria to test the reliability of results and differences between river reaches in addition we carried out a sensitivity analysis and discussed sources of uncertainties which may reach up to 112 mainly due to difficulties to determine the rotational stiffness of the root plate system a posteriori the approach presented here is promising but more research is clearly required to improve the quality of peak discharge estimations based on stem tilting

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

classic and new dating methods for assessing the temporal occurrence of mass movements abstract establishing landslide chronologies is essential both for understanding causes of mass movements as part of fundamental geomorphological research and for the assessment of landslide hazards as part of applied geomorphology we discuss the applicability of different methods for determining landslide chronologies frequencies and dynamics in relation to the type of material being dated sampling location and type of mass movement the emphasis is on the possibilities and limitations of the different dating methods established methods such as radiocarbon dating lichenometry and dendrochronology are briefly discussed the paper focuses however on 1 new analytical techniques like accelerator mass spectrometry ams thermally ionising mass spectrometry tims and laser fusion which have led to significant improvements of established dating methods and on 2 new dating methods like optically stimulated luminescence osl dating and alpha recoil track art dating

contribution of dendrochronology to the determination of magnitude frequency relationships for landslides abstract the determination of magnitude frequency m f relationships is necessary for landslide hazard assessment ideally this is achieved by using inventories of past landslide events recorded by technical units or aerial photo interpretation however direct sources of landslide data are often unavailable dendrogeomorphological techniques allow us to determine the frequency of events but few attempts have been made to estimate landslide magnitude by analysing the spatial distribution of disturbed trees this paper addresses m f determination for rockfalls debris flows and complex slides obtained by dendrogeomorphology the cases presented require the appropriate understanding of both the geomorphological context and the disturbance caused by landslide motion on trees both small and large rockfalls can be identified and dated by reconstructing the trajectories in the forest stand the larger the rockfall size the longer the path the higher the number of affected trees and the greater the area of deposition of rock fragments the area of damaged trees is proposed as an indicator of the rockfall magnitude the frequency and extent of a series of debris flows were reconstructed by mapping their deposits using relative dating criteria and by dating damaged trees local and global mudslide reactivations were deduced by sampling various tree generations and by analysing the location of the disturbed trees in the landslide units magnitude cumulative frequency curves were determined for the three cases

dendrogeomorphological analysis of mass movement a technical note on the research method dating of mass movement events by examining the course of eccentricity of the annual rings of trees inclined as a result of these movements can be a problem in the case of multiple inclined trees showing compound trunk curvature and complex reaction wood these problems however can be solved when sampling of ring width cores is based on accurate analysis of the form of the trunk

complex landslide terrain in the kamienne mountains middle sudetes sw poland dense forest hides a complex landslide terrain in the kamienne mountains a part of the sudetes range in central europe combined geomorphological geophysical and dendrochronological research was carried out in three representative localities in order to decipher patterns of landslide evolution to determine the extent of slope deformations and to assess the contemporary activity of landslide terrain field mapping revealed the very complex nature of slope failures both in space and time deep seated sliding was the principal type of movement and was followed by rock wall retreat by fall in the depletion zone and earthflows in the toe area electric resistivity survey proved useful in constraining geometry of landslide units and suggests an occurrence of underground voids in the lesista landslide area dendrochronological research focused on tree ring reduction reaction wood wound and scar analysis that helped to unravel the pattern of debris supply and movement subsequent to the main events which includes free fall talus creep and sliding over snow cover today landslide complexes are at different stages of evolution whereas in some places the activity has been largely completed in others we have found the evidence for failure surfaces ready to accommodate movement hence although some landslides may be relict it is unjustified to extend this notion to all signs of hillslope instability in the area

tree ring based assessment of rockfall frequency on talus slopes at sola d andorra eastern pyrenees abstract the determination of the frequency of rockfall events continues to challenge quantitative hazard assessments in most mountain areas dendrogeomorphological analysis was used to assess rockfall frequency on talus slopes at sola d andorra eastern pyrenees andorra rockfall events were dated at two sites one at the outlet of a chute and the other below a rock wall the impact wounds visible on the tree surface were analyzed with a seasonal temporal resolution at each site trees were sampled in three forest strips 15 to 30 m wide located at different heights on the talus all the trees with visible injuries in the strips were sampled rockfall frequency cannot be assessed by a simple analysis of time series of tree damage a satisfactory assessment requires a prior interpretation of the location of the damaged trees in relation to a number of rockfall events at sola d andorra the rockfall chronology was reconstructed for the last 25 years by dating visible wounds for older periods the tree wound record of rockfalls is incomplete owing to progressive closure of wounds wounds exceeding 40 years in age had already disappeared from the tree surface in the study area our results show a clear reduction of the rockfall frequency down the talus a noticeable lateral change in frequency and an influence of source morphology chute or wall on rockfall activity on the talus

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

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

annually laminated lake sediments and environmental changes in bashang plateau north china abstract angulinuo lake is the biggest lake on the bashang plateau north china and is 47 6 km2 in area and 2 6 m in depth a core from the inner part of angulinuo lake was sliced and the sediment was observed by scanning electronic microscope sem annual laminations characterized by variable color and grain size were found and interpreted as recording the cyclic deposition of lacustrine clay and aeolian dust the results of chemical analysis of coarse grains conducted by sem edax and grain size analysis of modern aeolian dust in the ice on angulinuo lake support an aeolian origin for the light coarse layers image analysis technique was used to calculate the size and number of coarse grains in each layer the coarse grains were fractionated into four classes 42 m 14 42 m 14 4 2 m and 1 4 4 2 m in general the abundance of the four classes shows similar temporal variation patterns around angulinuo lake the winter monsoon is strong and transports aeolian dust into the lake when the winter monsoon is strong the size and amount of coarse grains are expected to increase we infer that the winter monsoon was weaker during 8430 5440 year bp and was unstable in the later part of this period from 5440 year bp the winter monsoon became stronger and then weaker from 3250 to 2490 year bp during 2490 1170 year bp the winter monsoon was slightly stronger but since 1170 year bp it has become weaker again the changes of the winter monsoon intensity recorded in the annual laminations in angulinuo lake sediments correspond well to environmental changes in north china and to changes in sea level during the same period periods of weaker winter monsoon correspond to times of higher sea levels while the periods of stronger winter monsoon correspond to the neoglaciation stage in china and the periods of lower sea levels

depositional systems and sequence architecture of the oligocene dongying formation liaozhong depression bohai bay basin northeast china the sequence stratigraphic framework and depositional systems of an oligocene lacustrine rift succession in the liaozhong depression of bohai bay basin in northeastern china were investigated using seismic profiles complemented by well logs and cores seven sequences are identified on the basis of unconformities on basin margins and correlative conformities in the basin center depositional systems are associated with systems tracts within sequences lowstand systems tracts are dominated by sublacustrine fans transgressive systems tracts are mainly composed of beach bar deposits and highstand systems tracts are characterized by deep lacustrine fan or braid delta deposits episodic tectonic movement was the principal factor that controlled the development of the sequences lake level changes resulting from climatic oscillations may have controlled the development of these sequences the balance between tectonic subsidence and sediment supply controlled the type of lake basin the bohai bay basin was a balanced fill basin in the early and middle stages of the dongying formation and evolved into an overfilled basin at the end of deposition of the dongying formation this study enhances the understanding of depositional system configuration and systems tracts in a typical rift basin and proposes that the most favorable sandstone reservoirs are developed in sublacustrine fan deposits relative lowstand sublacustrine fan deposits capped by relative highstand prodelta or deep lacustrine mudstones form the highest potential lithostratigraphic traps

the sensitivity of dendrogeomorphic approaches to assessing landslide movements abstract an understanding of past landslide behaviour is crucial for the estimation of future landslide activity in this respect methods of absolute dating are frequently used for landslide history assessment dendrogeomorphic tree ring based approaches are standard methods for the spatio temporal reconstruction of landslide activity with annual to even sub annual resolution and timespans of several centuries depending on the tree age nevertheless the verification of the effectiveness sensitivity and precision of these dendrogeomorphic approaches has not been addressed in more detail despite their wide spectrum of limitations this study makes an assessment of tree ring based chronologies of landslides based on a comparison with the independent data of past landslide activity from instrumental monitoring the chronology of past landslide events was created from 528 tree ring series from 132 individuals of norway spruce picea abies l karst growing on a monitored landslide in the outer western carpathians the ond ejnik mt and was expressed as the yearly variation in the standard event response index the landslide was monitored at two sites via technical levelling since 2007 and an automated wire extensometer since 2014 the obtained results show a high sensitivity of reaction wood formation to movements on the order of several mm e g the abrupt acceleration of movements in february 2017 as recorded by the extensometer moreover a one year delay in the growth response to movement occurring in the middle part of the growing season of the previous year was detected this fact fully supports the introduction of the dendrological year to dendrogeomorphic research the partial lack of correspondence between tree ring records and data from more distant monitoring sites suggests the need for separate dendrogeomorphic analyses of the individual homogenous parts of landslide areas finally the use of four instead of two increment cores per tree did not provide any extra event years but increased the values of the event response index of the dated events

probability maps of landslide reactivation derived from tree ring records pra bellon landslide southern french alps probability maps of landslide reactivation are presented for the pra bellon landslide located in the southern french alps based on results obtained with dendrogeomorphic analysis spatiotemporal patterns of past landslide activity was derived from tree ring series of 403 disturbed mountain pine trees growing in the landslide body in total 704 growth disturbances were identified in the samples indicating 22 reactivation phases of the landslide body between 1910 and 2011 the mean return period was 4 5 years given the spatiotemporal completeness of the reconstruction probabilities of landslide reactivation were computed and illustrated using a poisson distribution model and for 5 20 50 and 100 years probability of landslide reactivation is highest in the central part of the landslide body and increases from 0 13 for a 5 year period to 0 94 for a 100 year period conversely probabilities of reactivation are lower at its margins the proposed method differs from conventional approaches based on statistical analyses or physical modeling that have demonstrated to have limitations in the prediction of spatiotemporal reactivation of landslides our approach is in contrast based on extensive data on past landslides and therefore allowed determination of quantitative probability maps of reactivation derived directly from the frequency of past events this approach is considered a valuable tool for land managers in charge of protecting and forecasting people and their assets from the negative effects of landslides as well as for those responsible for land use planning and management it demonstrates the reliability of dendrogeomorphic mapping that should be used systematically in forested shallow landslides

high resolution quantitative reconstruction of erosion rates based on anatomical changes in exposed roots at draix alpes de haute provence critical review of existing approaches and independent quality control of results extensive areas of french alps are underlain by jurassic black marls wherever these terres noires crop out they become subject to intense erosion causing major sedimentation in regional reservoirs and river systems in the badlands near draix alpes de haute provence france measured sediment rates were obtained at the plot scale by surface elevation change based methods and at the catchment scale by monitoring sedimentation in dams in this study we use a dendrogeomorphic approach based on anatomical changes in exposed roots of pinus sylvestris l to accurately quantify continuous denudation rates a total of 123 cross sections 75 from buried and 48 from exposed roots of 23 trees were sampled in the moulin basin the size and position of roots at the time of exposure was determined via anatomical variations in the annual growth rings of roots in cross sections of buried roots a sharp reduction of earlywood tracheid lumen area a growth signature which has traditionally been used to determine the moment of root denudation was observed as soon as erosion reduced soil cover to 3 cm as a consequence estimates of eroded soil thickness had to be adjusted to take account of this bias bias adjusted averaged medium term erosion rates derived from exposed roots vary between 6 and 7 mm y 1 at moulin basin depending on the importance accorded to the uplift of roots after exposure values are significantly correlated to slope angle and match with erosion rates derived from monitored iron stakes 5 7 mm y 1 or measurements of sediment yield in retention dams 4 7 mm y 1 at the outlet of the moulin basin besides demonstrating that the interpretation of anatomical signatures in tree roots to erosion have to be revised this paper also shows that dendrogeomorphic analyses of roots are indeed a powerful tool for the quantification of minimal rates of soil erosion in environments where measurements of past activity are not available

coupling between landslides and eroding stream channels reconstructed from spruce tree rings examples from the carpathians and sudetes central europe the analysis of the positive feedback between landslides and erosion requires determination of the precise temporal and spatial relations between events of colluvium delivery and fluvial erosion in our study we use decennial datasets on the occurrence of landsliding and erosion achieved through dendrochronological methods four sites covering areas of landslide slopes and adjacent valley floors with stream channels were studied landsliding on slopes was dated from the tree ring eccentricity developed in stems tilted due to bedrock instability erosion in channels was dated using the wood anatomy of roots exposed by erosion of the soil cover analysis of the temporal relations between dated landsliding erosion and precipitation record has revealed that two types of repeating sequences can be observed 1 rainfall landsliding erosion 2 rainfall erosion landsliding these sequences are an indication of the occurrence of slope channel positive feedback in the sites studied in the first type landsliding triggered by rainfall delivers colluvia into the valley floor and causes its narrowing which in turn causes increased erosion in the second type erosion triggered by rainfall disturbs the slope equilibrium and causes landsliding landsliding and erosion once triggered by precipitation can occur alternately in years with average precipitation and reinforce one another bidirectional coupling between landsliding and channel erosion was shown notably through the effects of channel shifting and forced sinuosity and by increased erosion of the slopes opposite the active landslides observations also suggest that the repetition of sequences described over longer periods of time can lead to a general widening of the valley floor at the expense of slopes and to a gradual change of the valley cross profile from narrow v shaped into a wide flat bottomed thus landsliding erosion coupling positive feedback was recognized as an important factor shaping hillslope valley topography of the mid mountain areas studied copyright 2014 john wiley sons ltd

spatio temporal patterns of recurrent slope instabilities affecting undercut slopes in flysch a dendrogeomorphic approach using broad leaved trees abstract the undercut slope of the skalicka stra nice vrchy hill situated in the piedmont of the carpathian mountains czech republic is a regional landslide hotspot notorious for its repeated recent and historical sliding reactivations we performed tree ring analysis of a large number n 274 of broad leaved trees to reconstruct the spatio temporal patterns of landslide reactivation for a period spanning more than one hundred years 1884 2011 although tree rings of broad leaved trees are less reliable archives of landslide activity than those of conifers the application of a methodology based on the weighting of disturbance signals within eccentricity series generated a usable dataset of sliding activity affecting anisotropic flysch bedrock although some known landslide years could not be found or were expressed by only weak signals in the reconstructed dataset the majority of landslide events reconstructed from the tree ring series coincide with hydrometeorological data revealing a correlation with heavy summer rainfalls lasting from two to ten days the spatial distribution of landslide recurrence derived from the tree ring records together with electrical resistivity tomography and a kinematic analysis of slope failures suggest a close link between the concentration of landslide activity and the presence of faulted or fractured flysch bedrock

dendrochronological study of the canal del roc roig avalanche path first results of the aludex project in the pyrenees historical data about ancient avalanches are scarce in the pyrenees dendrochronology can provide new data about past avalanches and their return period but up to now little research has been carried out with this purpose the aludex project aims to obtain information about the frequency and extent of extreme avalanches using a dendrochronological and a nivo meteorological approach in this paper we present the results of a dendrochronological study of the canal del roc roig avalanche path which was affected by two extreme avalanches in february 1996 this first dendrochronological study has permitted us to assess the tree ring signals due to avalanche events in 53 out of 132 dated trees the trees presented a variety of responses to the 1996 avalanche events it is shown that the type of tree ring signal depends on tree age the methodology has proved successful in detecting the 1996 and 1972 documented avalanche events and pro vided outstanding evidence of undocumented past events such as one in 1930

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