tree roots methodological review and new development in dating and quantifying erosive processes exposed roots have been used in dendrogeomorphology since the 1960s to determine erosion rates this was done by using the root axis as the relative position of the former soil layer and then relating this measure to the age of the root in order to quantify the amount of soil erosion over time recently wood anatomical research revealed the possibility of determining the first year of exposure of roots due to specific anatomical changes within the respective annual ring as a consequence using exposed roots that are still in contact to the soil surface it is possible to reconstruct the size and position of the root at the time of exposure consequently a new equation is presented to calculate the thickness of the eroded soil layer allowing a detailed reconstruction of erosion rates the technique also helps to determine if the root was exposed by erosional processes or just by its ongoing secondary growth without any erosion involved

analyzing rockfall activity 1600 2002 in a protection forest a case study using dendrogeomorphology for the first time dendrogeomorphology has been used to investigate spatial and temporal variations of rockfall activity in a protection forest we report results of 564 cores from 135 severely injured larix decidua mill trees on the west facing taschgufer slope swiss alps while trees sampled reached an age of 297 years on average the oldest one attained breast height in ad 1318 for reasons of sample depth the analysis was limited to the period 1600 2002 in total we reconstructed 741 growth disturbances gd during the last four centuries impacts were most commonly found in trees located in the southern part of the slope where gd recurred more than once per decade in contrast trees in the northern part were less frequently disturbed by rockfall and define recurrence intervals of more than 150 years throughout the last four centuries rockfall has caused gd to the trees sampled on the taschgufer slope most frequently in the form of low magnitude high frequency events in addition we identified one high magnitude low frequency event in 1720 which displaced the forest fringe of the northern sector a considerable distance downslope and eliminated an entire forest stand to analyze past rockfall activity we introduce a brateq defined as the number of impacts per meter width of all tree surfaces sampled per decade results clearly demonstrate that this rockfall brateq continually decreased in both sectors after the large 1720 rockfall event significantly low rockfall bratesq can be observed during the 1850s 1960s and 1970s in the northern and during the 1820s in the southern sector in contrast high rockfall bratesq were identified during the 1870s and 1990s in the northern and during the 1770s in the southern sector reconstructed data further show that the forest recolonizing the southern sector after the 1720 event gradually improved its protective function reducing bratesq by a factor of 13 between the 1740s and the 1990s in the recent past bratesq oscillated around 0 7 gd 1 meter width 1 10 years 1 in the well established forest of the northern sector the efficacy of the protective forest was temporarily reduced by the rockfalls in 1720 resulting in increased rockfall bratesq since then the protective

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

interpreting rockfall activity on an outcrop talus slope system in the southern japanese alps using an integrated survey approach abstract understanding relationships between meteorological conditions and rockfall activity is important for the management of rockfall risks as well as for the estimation of future rockfall activity under climate change seasonal activity of rockfall on talus slopes depends on the actual triggers of rockfall which in turn may vary as well between outcrops because of different rockfall sources and the influence of topography in this study we interpret spatial and temporal variations in rockfall activity and related sediment transfer processes in an outcrop talus slope system in central japan through monitoring using rock temperature and moisture sensors sediment traps and time lapse cameras in addition tree ring analysis has been added to understand possible changes of rockfall activity over longer time periods results suggest that the frequency of grouped gravel transport i e soil creep was higher than that of individual transport i e rockfall and dry ravel on the talus slope whereas rockfall likely is the predominant process from the outcrops observations from sediment traps showed that coarse gravel is characterized by higher bounce heights and that it travelled longer distances than fine gravel rockfall from the outcrops was most active during dormancy of trees which locally lasts from autumn to early spring and can be related to freeze thaw cycles in contrast rockfall and other sediment transfer processes were monitored on the talus slope all year round secondary movement of gravels on the talus slope such as soil creep during rainfall events likely triggers rockfall during times when the outcrops are not producing rockfall i e from late spring to summer consequently our results suggest that the spatio temporal rockfall activity varies substantially between outcrops and talus slopes and that differences in process behavior should be taken into account in future disaster mitigation measures

biogeomorphology revisited looking towards the future although biogeomorphological research is well established with many studies on a range of two way interrelations between organisms and geomorphology in different environments there is little consensus over what constitutes biogeomorphology why it might be useful and where it is heading starting with definitions of core biogeomorphic processes we consider the need for future biogeomorphological studies to evaluate the crucial links between bioprocesses biological community dynamics and inorganic earth surface processes five key applications of biogeomorphological research are identified the roles of organisms in environmental reconstruction trace fossil analysis extraterrestrial geomorphology environmental engineering and the built environment some key research directions and methodological challenges for future biogeomorphological research include expanding the spatial and temporal coverage of datasets investigating the role of bioprocesses in landform development tackling scale issues investigating the relevance of nonlinear dynamical ideas to biogeomorphology and developing better sampling and monitoring techniques for bioprocesses

surface wave focusing and acoustic communications in the surf zone the forward scattering of acoustic signals off of shoaling surface gravity waves in the surf zone results in a time varying channel impulse response that is characterized by intense rapidly fluctuating arrivals in some cases the acoustic focusing by the curvature of the wave crest results in the formation of caustics at or near a receiver location this focusing and the resulting caustics present challenges to the reliable operation of phase coherent underwater acoustic communications systems that must implicitly or explicitly track the fluctuations in the impulse response the propagation physics leading to focusing are studied with both experimental data and a propagation model using surface wave profiles measured during the collection of the experimental data the deterministic experimental and modeled data show good agreement and demonstrate the stages of the focusing event and the impact of the high intensity arrivals and rapid fluctuations on the ability of an algorithm to accurately estimate the impulse response the statistical characterization of experimental data shows that the focusing by surface gravity waves results in focused surface reflected arrivals whose intensity often exceeds that of the direct arrival and the focusing and caustic formation adversely impacts the performance of an impulse response estimation algorithm

spatio temporal analysis of a complex landslide in the northern apennines italy by means of dendrochronology dendrochronology is used to determine the spatial and temporal development of movements in a complex landslide located in the northern apennines the analysis of trees growing on the landslide body enabled us to date their colonisation pattern which starts from the 1920s and increases mainly after 1950 since then sampled trees recorded with growth anomalies the movements involving the landslide body in 1956 1957 1982 1983 1990 1995 and 1998 these movements are reactivations of the main landslide that probably occurred in the last decades of the 19th century in 1980 trees on the upper landslide body were involved in a rock fall due to the expansion of the main scarp microsections cut out from selected tree ring sequences allowed seasonal dating of the highlighted movements which mostly occurred in early spring meteorological and seismic time series were analyzed in order to relate them with reactivations and to search for correlations and triggering events the seismic activity although characterized by low magnitudes could be able either to trigger the movements 1990 or to destabilize the ground where rainfalls could have been playing the first role in triggering the reactivation probably in 1982 1983 and 1995 the other reactivations seem to be linked either to long lasting rainfalls or to monthly rainfall peaks mostly following dry periods

evaluation of meteorological controls of reconstructed rockfall activity in the czech flysch carpathians the spatio temporal characteristics of rockfall activity were studied at four localities representative of old landslides in the highest part of the czech flysch carpathians moravskoslezske beskydy mountains historical activity chronology and spatial context of rockfall activity were reconstructed using dendrogeomorphic techniques and rockfall rate index rr a total of 1132 increment cores from 283 trees growing in the rockfall transport and accumulation zones enabled the dating of 989 rockfall events reconstruction of a 78 year long rr chronology suggests similar rockfall histories and trends at all study sites indicating the existence of major common factors driving rockfall dynamics in the region temporal analysis and correlation of the rr series obtained with monthly mean temperatures numbers of days with temperature transitions through 0 deg c and monthly precipitation totals show that meteorological characteristics have evident but variable influence on rockfall activity

rockfall analysis along transportation corridors in high hill slopes the paper discusses the problems pertinent to rockfall activities in highly jointed rock cut slopes excavated without detailed geotechnical and geological investigations along the right bank of river sutlej luhri himachal pradesh india the cut slopes are near vertical to sub vertical and overhangs are ubiquitous at several locations initially probable zones of slope failure were identified from field inspection and kinematic analysis the study then uses 2d rockfall analysis for estimating loss of energy due to the impact of falling blocks on the slope face and subsequently on the road several parameters were also assessed from the study viz bounce height travel distance kinetic energy and translational velocity the result from rockfall analysis shows that the energy and velocity achieved by the falling blocks are considerably high capable enough to cause severe damage in relation to energy and velocity bounce height achieved is not very large because of removal of trees from the slopes face and no measures to capture falling blocks the problems have been aggravated and therefore most of the rock covers very large distance to reach up to the valley crossing the roadways endangering travelers and infrastructures based on the results preventive measures have been suggested to prevent future rockfall hazards

tree ring analysis and quaternary geology principles and recent applications abstract variations in annual growth rings can be utilized to assign precise calendar dates to the study of quaternary geologic or geomorphic events such as earthquakes mass movements glaciations and flooding living trees may provide the necessary absolute dates of events or minimum ages for surfaces crossdating among living trees and with subfossil wood can identify missing rings and extend tree ring chronologies further back in time these methods can lead to the accurate dating of tree rings in both living and dead trees that may have been affected by a geomorphic process the dating of partial to complete ring growth compression and release as well as dating externally apparent responses such as tree scarring or root sprouting can often lead to the identification of the season and the year an event occurred ring width patterns when compared with control chronologies can reveal the growth anomalies in witness trees that may be related to geomorphic events examples of the application of tree rings to quaternary geology and geomorphology are varied and numerous root shearing topping of trees and missing rings tie a rupture along the san andreas fault to the year 1812 a d narrow tree rings linked to defoliation and tephra fallout differentiated distinct eruptions of mt st helens in 1480 and in 1482 a d ring analysis has helped unravel glacial chronologies and tree ring linkages with climate have also verified that late holocene ice advances in argentina correlated with intervals of cool wet summers in another application an 1818 a d quebec landslide has been tied to the growing season whereas slides dated to 1834 and 1846 a d occurred during the spring

tree ring correlation between prehistoric landslides and abrupt tectonic events in seattle washington radiocarbon ages of submerged trees on landslide deposits in lake washington seattle indicate that the most recent slides in three separate areas may have occurred simultaneously about 1000 years ago tree ring crossdating shows that seven bark bearing trees from one of these recent slides and a tree 23 kilometers to the northwest in a probable tsunami deposit on the shore of puget sound died in the same season of the same year the close coincidence among the most recent lake landslides a probable tsunami abrupt subsidence and other possible seismic events gives evidence for a strong prehistoric earthquake in the seattle region

tree ring based reconstruction of rockfalls at cofre de perote volcano mexico in this study dendrogeomorphic techniques are employed to analyse the temporal frequency and spatial distribution of rockfalls on a talus slope of la teta valley located on the nw slopes of cofre de perote volcano at 4000 m above sea level based on the interpretation of disturbance signals in growth rings of old growth pinus hartwegii lindl trees we identify 100 growth disturbances related with rockfall events dated between 1780 and 2011 with slightly more than half of these events being dated to the last 50 years the sectors most susceptible to rockfall correspond with the young rock lobes located at the foot of scarps roughly three in ten events has been triggered by regional m 6 earthquakes whereas half of the events activity coincides with periods characterized by severe prolonged summer rainfalls such as the ones occurred in 1995 1998 2005 and 2011

dendrogeomorphological analysis of a slope near lago calabria italy dendrogeomorphology first introduced by alestalo 1971 has been applied successfully in the spatial and temporal analysis of mass movements by many authors shroder 1978 investigated landslides in the table cliffs plateau of utah finding peak periods of mass movement reactivation many authors terasme 1975 shroder 1978 hupp 1984 strunk 1992 denneler and schweingruber 1993 found that trees subject to stress due to mass movement have manifested strong and sudden decreases in ring growth this effect on tree growth was also found by orombelli and gnaccolini 1972 in dating the vajont landslide in italy through the study of tilted conifers another important kind of information on the causes of landslide movement was pointed out in the papers of jibson and keefer 1988 and filion et al 1991 those authors discovered coincidence between the dating of tree disturbances and past strong earthquakes in the mississippi valley and riviere du gouffre respectively dendrochronology was used by hupp 1984 van asch and van steijn 1991 and strunk 1992 to evaluate the frequency of landslide activity kashiwaya et al 1989 have investigated the relationship between tree ring width and heavy rainfall in the landslide prone area of kobe district in japan

potential of two submontane broadleaved species acer opalus quercus pubescens to reveal spatiotemporal patterns of rockfall activity long term records of rockfalls have proven to be scarce and typically incomplete especially in increasingly urbanized areas where inventories are largely absent and the risk associated with rockfall events rises proportionally with urbanization on forested slopes tree ring analyses may help to fill this gap as they have been demonstrated to provide annually resolved data on past rockfall activity over long periods yet the reconstruction of rockfall chronologies has been hampered in the past by the paucity of studies that include broadleaved tree species which are in fact quite common in various rockfall prone environments in this study we test the sensitivity of two common yet unstudied broadleaved species quercus pubescens willd qp and acer opalus mill ao to record rockfall impacts the approach is based on a systematic mapping of trees and the counting of visible scars on the stem surface of both species data are presented from a site in the vercors massif french alps where rocks are frequently detached from valanginian limestone and marl cliffs we compare recurrence interval maps obtained from both species and from two different sets of tree structures i e single trees vs coppice stands based on cohen s k coefficient and the mean absolute error a total of 1230 scars were observed on the stem surface of 847 a opalus and q pubescens trees both methods yield comparable results on the spatial distribution of relative rockfall activity with similar downslope decreasing recurrence intervals yet recurrence intervals vary significantly according to tree species and tree structure the recurrence interval observed on the stem surface of q pubescens exceeds that of a opalus by n20 years in the lower part of the studied plot similarly the recurrence interval map derived from a opalus coppice stands dominant at the stand scale does not exhibit a clear spatial pattern differences between species may be explained by the bark thickness of q pubescens which has been demonstrated to grow at twice the rate of a opalus thus constituting a mechanical barrier that is able to buffer low energy rockfalls and thus can avoid damage to the underlying tissues the reasons for differences between tree structures are related to the clustered coppice specific spatial stem distribution in clumps that could result on one hand in bigger gaps between clumps which in turn decreases the probability of tree impacts for traveling blocks on the other hand data also indicate that several scars on the bark of coppice stands may stem from the same impact and thus may lead to an overestimation of rockfall activity

combining field and modelling techniques to assess rockfall dynamics on a protection forest hillslope in the european alps adequate management of a mountain forest that protects downslope areas against impacts of rockfall requires insight into the dynamics of the hillslope environment therefore we applied a combined approach using field and modelling techniques to assess the determining factors for rockfall source areas rockfall tracks and rockfall runout zones on a forested slope in mountainous terrain the first objective of this study was to understand why rockfall occurs in the study area the second objective was to translate the knowledge obtained in the field into a model that simulates rockfall dynamics on a forested slope realistically the third objective was to assess which hillslope characteristics primarily determine the distribution of active rockfall tracks to achieve these objectives we made a geomorphological map of the whole study area and we measured the major discontinuity planes in the bedrock that are exposed in the rockfall source areas furthermore a test site for simulation modelling within the larger study area was defined in which both a forest and a hillslope inventory were carried out the available data and our developed rockfall simulation model allowed us to assess the slope characteristics that mainly determine the distribution of areas affected by rockfall we found that in decreasing order of importance both standing and felled trees the surface roughness and rockfall resistant shrubs primarily determine the distribution of rockfall affected areas simulation tests without a forest cover produced similar rockfall runout zones as fossil rockfall events identified in the field we believe that the combined field and modelling approach is a prerequisite for understanding how forests can protect against rockfall

parameterization of rockfall source areas and magnitudes with ecological recorders when disturbances in trees serve the calibration and validation of simulation runs on forested talus slopes which have been build up by rockfall a strong interaction exists between the trees and the falling rocks while the presence and density of vegetation have a profound influence on rockfall activity the occurrence of the latter will also exert control on the presence vitality species composition and age distribution of forest stands this paper exploits the interactions between biotic tree growth and abiotic rockfall processes in a mountain forest to gather and obtain reliable input data on rockfall for the 3d process based simulation model rockyfor3d we demonstrate that differences between the simulated and observed numbers of tree impacts can be minimized through i a careful definition of active source areas and ii a weighted distribution of block sizes as observed in the field as a result of this field based optimized configuration highly significant values can be obtained with rockyfor3d for the number of impacts per tree so that results of the model runs can be converted with a high degree of certainty into real frequencies the combination of the field based dendrogeomorphic with the modeling approaches is seen as a significant advance for hazard mapping as it allows a reliable and highly resolved spatial characterization of rockfall frequencies and a realistic representation of past rockfall dynamics at the slope scale

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

significance of rockfall magnitude and carbonate dissolution for rock slope erosion and geomorphic work on alpine limestone cliffs reintal german alps abstract the proportional contribution of low mid and high magnitude rock slope failure orchestrates rock slope erosion and rockfall hazard in alpine and arctic environments in this study we compare sediment yield geomorphic work and rock wall retreat of carbonate dissolution and five different magnitudes of rock slope failure in the steep alpine reintal trough valley we combine a four year rockfall collector measurement of 140 mg of fragmental rockfall a 20th century scientific record of mid magnitude rockfall as well as carbon dating and a historical record of 15th to 19th century rock avalanche activity the total rockfall sediment yield of 8 6 3 4 10 3 m 3 year 1 is dominated by high magnitude rock avalanches 10 6 m 3 62 and low magnitude debris falls 3 18 while mid magnitude boulder block and cliff falls are less important the magnitude signal contradicts studies on siliceous rocks where mid magnitude rockfall dominates rock slope erosion the geomorphic work released in the 17 3 km 2 large catchment by rockfalls 123 47 w km 2 i e 0 38 0 15 mm year 1 and solute transport 34 18 w km 2 i e 0 05 0 03 mm year 1 exceeds previously published alpine values by one to multiple orders of magnitude we hypothesise that the magnitude signal of enhanced small and high magnitude rockfall is characteristic for carbonate cliffs the elevated porosity related susceptibility to fragmentation and persistent carbonate dissolution along potential sliding planes are likely to favour both low and high magnitude rock slope failures here we show how the magnitude signal of rock slope failure influences rock wall retreat geomorphic work rockfall deposition and sediment connectivity

vertical coherence and forward scattering from the sea surface and the relation to the directional wave spectrum results of an experiment to measure vertical spatial coherence from acoustic paths interacting once with the sea surface but at perpendicular azimuth angles are presented the measurements were part of the shallow water 2006 program that took place off the coast of new jersey in august 2006 an acoustic source frequency range 6 20 khz was deployed at depth 40 m and signals were recorded on a 1 4 m long vertical line array centered at depth 25 m and positioned at range 200 m the vertical array consisted of four omni directional hydrophones and vertical coherences were computed between pairs of these hydrophones measurements were made over four source receiver bearing angles separated by 90 during which sea surface conditions remained stable and characterized by a root mean square wave height of 0 17 m and a mixture of swell and wind waves vertical coherences show a statistically significant difference depending on source receiver bearing when the acoustic frequency is less than about 12 khz with r

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 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

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

a data based landslide susceptibility map of africa abstract our understanding of the spatial patterns of landslides in africa is limited with available landslide studies typically focusing on only one or a few study areas moreover africa is clearly underrepresented in terms of available landslide inventories this study aims to produce a first continent wide landslide susceptibility map for africa calibrated with a well distributed landslide dataset we reviewed the literature on landslides in africa and compiled all available landslide inventories ca 10 800 landslides supplemented by additional landslide mapping using google earth imagery in underrepresented regions ca 7250 landslides this resulted in a dataset of approximately 18 050 landslides various environmental variables were investigated for their significance in explaining the observed spatial patterns of landslides to account for potential mapping biases in the dataset we used monte carlo simulations that selected different subsets of mapped landslides to test the significance of the considered environmental variables based on these analyses we constructed two landslide susceptibility maps for africa one for all landslide types and one excluding the known rockfalls in both maps topography is by far the most significant variable we evaluated the performance of the fitted multiple logistic regression models using independent subsets of landslides selected from the total dataset overall both maps perform very well in predicting intra continental patterns of landslides in africa and explain about 80 of the observed variance in landslide occurrence to further test the robustness and sensitivity to mapping biases we also modelled landslide susceptibility while excluding regions with arid climates as landslides in these environments are expected to be better preserved over time and therefore likely relatively overrepresented despite this potential bias the effect on the landslide susceptibility model is limited based on the constructed database and our analyses we further discuss potential research gaps for landslide prediction in africa and at continental scales for example analysis of the african countries mean landslide susceptibility shows a lack of landslide research in various countries prone to landsliding e g guinea gabon lesotho madagascar apart from the intrinsic value of this landslide susceptibility map as a natural hazard risk management tool the map and compiled database are highly promising for other applications for example we explored the potential significance of landslides as a geomorphic process by confronting our landslide susceptibility map with an available database of measured catchment sediment yield for 500 rivers in africa overall a significant positive but relatively weak relation between landslide susceptibility and sediment yield is observed

interpretation of recent alpine landscape system evolution using geomorphic mapping and l band insar analyses abstract alpine landscapes are typically characterized by inherited features of past glaciations and for the more recent past by the interplay of a multitude of types of geomorphic processes including permafrost creep rockfalls debris flows and landslides these different processes usually exhibit large spatial and temporal variations in activity and velocity the understanding of these processes in a wide alpine area is often hindered by difficulties in their surveying in this study we attempt to disentangle recent changes in an alpine landscape system using geomorphic mapping and l band dinsar analyses alos palsar in the zermatt valley swiss alps geomorphic mapping points to a preferential distribution of rock glaciers on north facing slopes whereas talus slopes are concentrated on south facing slopes field based interpretation of ground deformation in rock glaciers and movements in talus slopes correlates well with the ratio of insar images showing potential ground deformation moraines formed during the little ice age rock glaciers and talus slopes on north facing slopes are more active than landforms on south facing slopes implying that the presence of permafrost facilitates the deformation of these geomorphic units such deformations of geomorphic units prevail also at the elevation of glacier termini for rock cliffs the ratio of images indicating retreat is affected by slope orientation and elevation linkages between sediment supply from rock cliffs and sediment transport in torrents are different among tributaries affected by relative locations between sediment supply areas and the channel network we conclude that the combined use of field surveys and l band dinsar analyses can substantially improve process understanding in steep high mountain terrain

dendrogeomorphic dating of rockfalls on low latitude high elevation slopes rodadero iztaccihuatl volcano mexico dynamics and rates of rockfalls have been repeatedly studied in mountain environments with archival records as well as lichenometric radiocarbon or dendrogeomorphic approaches in this study we test the potential of conifers growing at a low latitude high elevation site as a dendrogeomorphic tool to reconstruct to calendar dates associated rockfall activity analysis is based on tree ring records of mexican mountain pine pinus hartwegii lindl growing at timberline 4000 m above sea level a s l and at the runout fringe of a north northeast nne facing slope of the dormant iztaccihuatl volcano mexico which is subject to frequent rockfalls the potential and limitations of tree ring data are demonstrated based on 67 rockfall impacts dated in the increment ring series of 24 trees since ad 1836 while findings of this paper are site specific the study clearly shows the potential of dendrogeomorphic approaches in extra alpine low latitude environments and for the understanding of rockfall processes in space and time copyright 2011 john wiley sons ltd

observations and modeling of angular compression and vertical spatial coherence in sea surface forward scattering measurements and modeling of vertical spatial coherence and related angular spreading associated with forward scattering from the sea surface are presented the van cittert zernike theorem is used in the modeling the measurements were conducted in waters 80 m deep off the north american continental shelf shallow water 06 aug 2006 acoustic signals were recorded on a moored array system moray consisting of three arrays each 1 4 m two vertical line arrays at depth 25 m and 50 m and one horizontal array at depth 27 m the source 1 20 khz was deployed at depth 40 m from the r v knorr at ranges 50 500 m from the moray conditions were characterized by a downward refracting profile e g sound speed going from 1530 m s at the surface to 1490 m s at depth 25 m refraction modifies the vertical angular vertical spread due to scattering which can understood from snell s law the snell mapping is smooth and a taylor expansion around the mean grazing angle provides a functional relation between the

rockfall activity from an alpine cliff during thawing periods abstract rockfall activity during thawing periods was investigated by collecting rockfall debris fallen on the snow covered talus slope in a cirque in the japanese alps near surface rock temperature was also monitored on the cirque wall maximum rockfall activity occurs on average about 10 days after the meltout of the cirque wall the intensive activity is rarely associated with precipitation events or diurnal frost cycles on the rockface a thermal conduction model suggests that rockfalls at this site occur most frequently when the seasonal thawing front penetrates to a depth of about 1 m in the bedrock while the freeze thaw penetration controls the maximum dimensions of detachable rock mass joint spacing on the rockface affects the size distribution of rockfall debris boulder falls resulting from seasonal frost weathering are considered to be the most important process responsible for the contemporary modification of the cirque wall the rockfall volume during a thawing period is usually 1 3 m3 which is equivalent to the rate of cirque wall retreat of the order of 0 01 mm year 1 however big boulder falls that occur once per decade can increase the retreat rate significantly

coherent reflection from surface gravity water waves during reciprocal acoustic transmissions during a recent experiment in kauai hawaii reciprocal transmissions were conducted between two acoustic transceivers mounted on the seafloor at a depth of 100 m the passage of moving surface wave crests was shown to generate focused and intense coherent acoustic returns which had increasing or decreasing delay depending on the direction of propagation relative to the direction of surface wave crests it is shown that a rough surface two dimensional parabolic equation model with an evolving sea surface can produce qualitative agreement with data for the dynamic surface returns

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

magnitude and frequency of rock falls and rock slides along the main transportation corridors of southwestern british columbia the two main transportation corridors of southwestern british columbia are subject to a range of rock slope movements rock falls rock slides and rock avalanches that pose significant risks to r

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

spatial and temporal rockfall activity in a forest stand in the swiss prealps a dendrogeomorphological case study abstract rockfall is a major threat to settlements and transportation routes in large parts of the alps while protective forest stands in many locations undoubtedly reduce rockfall risk little is known about the exact frequency and spatial distribution of rockfall activity in a given place or about how these parameters can be assessed therefore the objective of the present study was to reconstruct rockfall events with dendrogeomorphological methods and to analyse the spatial and temporal rockfall activity in a subalpine forest stand the study site is located in the transit zone of frequently passing rather small rockfall fragments mean diameter of 10 to 20 cm in all 33 stem discs from previously felled picea abies trees found at the foot of schwarzenberg in diemtigtal swiss prealps were sampled and a total number of 301 rockfall events were dated to between a d 1724 and 2002 results showed that the spatial distribution of rockfall changed slightly with time and that rockfall activity increased considerably over the last century in contrast rockfall magnitude presumably remained on a comparable level the seasonal occurrence of rockfall showed a clear peak during the dormant season of trees most probably in early spring furthermore on a 10 year moving average basis rockfall rates were positively correlated with mean annual as well as summer and winter temperatures this means that higher temperatures resulted in increased rockfall activity on the other hand no correlation with annual or seasonal precipitation totals was revealed overall this study provides an appropriate method for the detailed assessment of spatial and temporal variations in rockfall activity in a given place

modeling rockfall frequency and bounce height from three dimensional simulation process models and growth disturbances in submontane broadleaved trees the use of dynamic computational methods has become indispensable for the assessment of rockfall hazards and the quantification of uncertainties although a substantial number of models with various degrees of complexity has become available over the past few years models have only rarely been parameterized against observations especially because long term records of rockfalls have proven to be scarce and typically incomplete on forested slopes tree ring analyses may help to fill this gap as they have been shown to provide annually resolved data on past rockfall activity over long periods in this paper a total of 1495 rockfall scars recorded on the stem surface of 1004 trees have been studied at a site in the vercors massif french alps to calibrate the 3d process based simulation model rockyfor3d uncertainties related to the choice of parameters accounting for energy dissipation and surface roughness have been investigated in detail because of the lack of reliable data these parameters typically are estimated based on expert judgments despite the fact that they have significant impacts on runout distances and bounce height we demonstrate that slight variations in roughness can indeed strongly affect the performance of runout modeling and that the decreasing downward gradient observed in field data is properly reproduced only if reduced roughness 10 cm enables blocks to reach the distal parts of the study plot with respect to the height of impacts our results also reveal that differences between simulations and observations can indeed be minimized if softer soil types are preferred during simulation as they typically limit bouncing we conclude that field based dendrogeomorphic approaches represent an objective tool to improve rockfall simulations and to enhance our understanding of parameterization which is of key importance for process dynamics and thus hazard zoning