landslide characteristics and slope instability modeling using gis lantau island hong kong steep terrain and high a frequency of tropical rainstorms make landslide occurrence on natural terrain a common phenomenon in hong kong this paper reports on the use of a geographical information systems gis database compiled primarily from existing digital maps and aerial photographs to describe the physical characteristics of landslides and the statistical relations of landslide frequency with the physical parameters contributing to the initiation of landslides on lantau island in hong kong the horizontal travel length and the angle of reach defined as the angle of the line connecting the head of the landslide source to the distal margin of the displaced mass are used to describe runout behavior of landslide mass for all landslides studied the horizontal travel length of landslide mass ranges from 5 to 785 m with a mean value of 43 m and the average angle of reach is 27 7 this gis database is then used to obtain a logistic multiple regression model for predicting slope instability it is indicated that slope gradient lithology elevation slope aspect and land use are statistically significant in predicting slope instability while slope morphology and proximity to drainage lines are not important and thus excluded from the model this model is then imported back into the gis to produce a map of predicted slope instability the results of this study demonstrate that slope instability can be effectively modeled by using gis technology and logistic multiple regression analysis

linking hydrological infinite slope stability and land use change models through gis for assessing the impact of deforestation on slope stability in high andean watersheds in the ecuadorian andes episodic slope movements comprising shallow rotational and translational slides and rapid flows of debris and soil material are common consequently not only considerable financial costs are experienced but also major ecological and environmental problems arise in a larger geographical area sediment production by slope movement on hillslopes directly affects sediment transport and deposition in downstream rivers and dams and morphological changes in the stream channels in developing countries world wide slope movement hazards are growing increasing population pressure and economic development force more people to move to potentially hazardous areas which are less suitable for agriculture and rangelands this paper describes the methods used to determine the controlling factors of slope failure and to build upon the results of the statistical analysis a process based slope stability model which includes a dynamic soil wetness index using a simple subsurface flow model the model provides a time varying estimate of slope movement susceptibility by linking land use data with spatially varying hydrologic soil conductivity evapotranspiration soil wetness and soil strength properties the slope stability model was applied to a high andean watershed gordeleg catchment 250 ha southern ecuadorian andes and was validated by calculating the association coefficients between the slope movement susceptibility map of 2000 and the spatial pattern of active slope movements as measured in the field with gps the proposed methodology allows assessment of the effects of past and future land use change on slope stability a realistic deforestation scenario was presented past land use change includes a gradual fragmentation and clear cut of the secondary forests as observed over the last four decades 1963 2000 future land use change is simulated based on a binary logistic deforestation model whereby it was assumed that future land use change would continue at the same rate and style as over the last 37 years 1963 2000 c 2002 elsevier science b v all rights reserved

hydrological and geotechnical investigations of mass movements in an equatorial city yaounde cameroon in the present study mass movements landslide and mudslide bound to a gully located at mendong a suburb of yaounde in cameroon were examined using hydrological geotechnical and geomorphological observations the data indicate that water is an important causative factor of mass movements in the area studied in fact the water flow waste water and runoff provokes the saturation of materials at the slope foot these materials lose their mechanical qualities and some deep ruptures generate landslide during the rainy season when the cumulative rainfall is more than 200 mm these landslides are accompanied by mudslides that generate disturbances on the infrastructure situated around the gully and farther downstream the economic and environmental damages resulting from the mendong mass movements are considerable such as degradation of the topography losses in farm land transportation and downstream sedimentation in a pond situated at the slope foot loss of life and damage to the economy all this calls for a multidisciplinary and integrated approach to hazard assessment and risk mitigation which included data collection and interpretation growing public and authority awareness and preventing or reducing runoff and waste water flows by proper management and drainage

a country wide spatial assessment of landslide susceptibility in romania abstract this paper proposes a brief spatial analysis of landslides in romania completed by a landslide susceptibility model landslides constitute a very common geomorphic hazard in this country mainly in the hilly regions which occupy around 30 of romania s territory the landslide susceptibility assessment at national level was accomplished using a landslide susceptibility index lsi computed in gis which considers and weights the main factors that control landslide activity lithology slope gradient maximum rainfall in 24 h land use seismicity and local relief each factor was classified into 7 18 classes which were rated from 1 to 10 by means of expert judgement a formula was devised to compute the landslide susceptibility index over each 100 m 100 m pixel and the resulting values were ranked into 5 landslide susceptibility classes this synthetic method of landslide susceptibility assessment applied to the whole country is a useful tool to evaluate the distribution of landslide prone areas as well as to validate and to enhance some results obtained in previous studies based on field research and map interpretation the most landslide prone areas correspond to the subcarpathians an outer fringe of hilly terrain accompanying the carpathians as well as to the moldavian plateau in the east the semi quantitative approach has been validated with satisfactory results in a particular sector using independent cartographic landslide inventories

landslide occurrence as a response to land use change a review of evidence from new zealand abstract vegetation cover is an important factor influencing the occurrence and movement of rainfall triggered landslides and changes to vegetation cover often result in modified landslide behaviour however it is difficult to relate the occurrence of landslides directly to variations in land use especially in some european countries in contrast new zealand provides a good opportunity to investigate geomorphic responses to anthropogenic land cover changes before european settlers first arrived in the 1840s hilly regions were only marginally influenced by human activity the maoris new zealand s first settlers lived largely on coastal plains or near lakes and rivers they influenced general vegetation cover only through localized burning practices in contrast european settlers moved into the back country and converted extensive hill areas from native forest and bush to pasture this reduced the strength of the regolith and rendered the slopes more susceptible to landslides pulses of natural sedimentation in the pre european period have been related to volcanic activity climatic variability including changes in frequency of cyclonic storms and wind erosion and fluvial erosion following forest fires initiated either by volcanic eruptions or lightning strikes since european deforestation began sediment production has largely been determined by landslide events on unstable slopes thousands of landslides were triggered by high magnitude low frequency climatic events during storms with estimated return periods in excess of 50 years in contrast low magnitude high frequency rainfall events have caused gully and channel erosion examples from different parts of new zealand indicate changes in sediment generating processes following land use modifications after deforestation landslides have contributed significantly to sediment sequences in depositional basins such as lakes swamps estuaries coastal wetlands and the nearshore and offshore zones of continental platforms

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

the topographic thresholds of hillslope incisions in southwestern rwanda abstract this article presents new quantitative evidence that land use in rwanda contributes to the development of hillslope incisions two types of hillslope incisions can be distinguished in southern rwanda incisions of the first type drain an area depending on the form and extension on the natural topography and geology the runyinya gully 25 and the rugabano soil slippage 39 are two examples on a logarithmic plot of critical slope inclination at the incision head versus drainage area towards the incision head both incisions lay sensibly to the right of the montgomery dietrich m d envelope the latter gives the range of these topographical thresholds for gully and mass wasting incision in parts of north america the runyinya and rugabano cases obey the linear equation s cr 0 6 a 0 6 where scr critical slope gradient tangent of slope in at the gully head or the scar and a the area ha drained towards the incision head hillslope incisions of the second group rely on a run on area larger than normal because they are localised at the outlet of artificially runoff collecting systems like roads soil conservational contour trenches tracks and other linear landscape elements such systems often drain a surface much larger in extension than the natural run on area to the outlet these hillslope incisions taking into account their artificially big drainage area concentrate more or less along the line s cr 0 3 a 0 6 this line is about in the center of the montgomery dietrich envelope if however only the natural drainage area of these outlet incisions is taken into account all points fall close to the left border or even to the left of the montgomery dietrich envelope this indicates a much higher probability for incision in those localities receiving supplementary runoff or interflow from outside the natural drainage area in the case of a soil slippage at rwaza hill detailed stability calculations show that the slope failure should be due to excessive water infiltration into the bottom of a trench the digging of the trench provoked an increase in the area drained to the slippage head by a factor of 6 the phenomenon of forward erosion is compatible with the existence of threshold combinations of slope and drained area for slopes steeper than 7 8 the phase of regressive erosion does often follow the forward incision event with a delay of several years or more finally the scanty data set now available for rwanda suggests that the drainage area critical to hillslope incision on the red brown ferrallitic soils in rwanda might be nearly twice as big as those in north america

an improved set of a x parameters for fe mg ca garnets and refinements of the orthopyroxene garnet thermometer and the orthopyroxene garnet plagioclase quartz barometer

landslides and quaternary climate changes the state of the art abstract climatic factors are considered major causes and triggers of slope instability but the palaeoclimatic implications of landslides have not yet been systematically reviewed as inferred from landslides dated to the late glacial and holocene glacial interglacial transitions are the major intervals of enhanced landsliding but the length of this interval varies between distinct types of landscapes mass movements in non glaciated temperate mountain ranges arid and tropical regions and coastal areas intensified soon after the onset of the holocene alongside the warming and wetting of the climate whereas large rock slides in areas within the limits of pleistocene glaciations mostly show a millennial scale time lag with respect to glacier withdrawal although the incidence of landslides was ubiquitous throughout the holocene the mid to late holocene transition 5 4 ka was especially favourable for the origin of landslides across distinct types of landscapes indicating a strengthened role of mass movements during the culmination phases of interglacial climate optima in addition growing evidence suggests that the enhanced activity of landslides occurred during warmer interstadial conditions which is best demonstrated in the temporal coincidence of arid zone landslides with quaternary pluvials future progress in the understanding of the relationships between landslides and quaternary climate changes should benefit from the i extension of datasets of dated landslides ii geographical expansion of dating studies to regions with a lack of chronologically determined landslides e g tropics iii improvement of landslide dating strategies involving the incorporation of independent palaeoclimatic proxies and iv wider incorporation of numerical modeling within landslide dating studies

the effective elastic thickness of the continental lithosphere comparison between rheological and inverse approaches 1 following the release of global continental effective elastic thickness te maps obtained using different approaches we now have the opportunity to provide better constraints on te we improve previous estimates of te derived from thermo rheological models of lithospheric strength or ter using new equations that consider variations of the young s modulus in the lithosphere these new values are quantitatively compared with those obtained from an inverse approach or tei based on a comparison of the spectral coherence between topography and gravity anomalies with the flexural response of an equivalent elastic plate to loading the two models show in general a good agreement having equal means at the 95 significance level in about half of the continental areas in other regions tei exceeds ter in about 65 of the data points showing that tei provides an upper bound on te the two data sets have a similar range but demonstrate different distributions ter has a bimodal distribution with the two peaks representative of the cratons and of the areas outside of them in contrast tei has more uniform distribution without predominant peaks our models show higher similarities in the meso cenozoic orogens than in the archaean and proterozoic shields and platforms due to the methods employed for the regions with the most robust determinations of ter and tei the relationship between them is close to linear the results of this work can be used for further studies on the mechanical properties of the lithosphere

development of a globally applicable model for near real time prediction of seismically induced landslides substantial effort has been invested to understand where seismically induced landslides may occur in the future as they are a costly and frequently fatal threat in mountainous regions the goal of this work is to develop a statistical model for estimating the spatial distribution of landslides in near real time around the globe for use in conjunction with the u s geological survey usgs prompt assessment of global earthquakes for response pager system this model uses standardized outputs of ground shaking from the usgs shakemap atlas 2 0 to develop an empirical landslide probability model combining shaking estimates with broadly available landslide susceptibility proxies i e topographic slope surface geology and climate parameters we focus on four earthquakes for which digitally mapped landslide inventories and well constrained shakemaps are available the resulting database is used to build a predictive model of the probability of landslide occurrence the landslide database includes the guatemala 1976 northridge 1994 chi chi 1999 and wenchuan 2008 earthquakes performance of the regression model is assessed using statistical goodness of fit metrics and a qualitative review to determine which combination of the proxies provides both the optimum prediction of landslide affected areas and minimizes the false alarms in non landslide zones combined with near real time shakemaps these models can be used to make generalized predictions of whether or not landslides are likely to occur and if so where for earthquakes around the globe and eventually to inform loss estimates within the framework of the pager system

forecasting the magnitude of potential landslides based on insar techniques abstract a new method combining empirical modeling with time series interferometric synthetic aperture radar insar data is proposed to provide an assessment of potential landslide volume and area the method was developed to evaluate potential landslides in the heitai river terrace of the yellow river in central gansu province china the elevated terrace has a substantial loess cover and along the terrace edges many landslides have been triggered by gradually rising groundwater levels following continuous irrigation since 1968 these landslides can have significant impact on communities affecting lives and livelihoods developing effective landslide risk management requires better understanding of potential landslide magnitude fifty mapped landslides were used to construct an empirical power law relationship linking landslide area al to volume vl vl 0 333 al1 399 insar derived ground displacement ranges from 64 mm y to 24 mm y along line of sight los further interpretation of patterns based on remote sensing insar optical image and field survey enabled the identification of an additional 54 potential landslides 1 9 102 m2 al 8 1 104 m2 in turn this enabled construction of a map that shows the magnitude of potential landslide activity this research provides significant further scientific insights to inform landslide hazard and risk management in a context of ongoing landscape evolution it also provides further evidence that this methodology can be used to quantify the magnitude of potential landslides and thus contribute essential information towards landslide risk management

major natural hazards in a tropical volcanic island a review for mayotte island comoros archipelago indian ocean abstract mayotte is a french overseas territory of the comoros archipelago since the 1980 mayotte has developed quickly its population has multiplied by four in less than 30 years infrastructure expanded rapidly in lowlands and slums developed in steep areas through deforestation or close to riverbeds this development urgently required steps to ensure the safety of urban areas from 2002 to 2006 a major programme of natural hazards evaluation and zonation was conducted by the french geological survey in the 17 districts of mayotte the programme resulted in the publication of the first single hazard zonation maps for mayotte at 1 25 000 scale in rural areas and at 1 10 000 scale in urban areas hazard maps regarding landslides and rock falls stream floods seismic lithological and topographical amplification potential liquefaction potential and cyclonic marine submersion were produced for mayors and land planners these atlases also included prevention guidelines to minimize risks associated with land use or urbanization within hazard prone areas this article presents the main achievements of the programme whose main problems were the absence of archives of previous studies and the original volcanic geology of the island of mayotte the atlases highlight areas with numerous landslides zones susceptible to flash floods sectors likely to be submerged by storm surges and areas subject to seismic site effects due to thick volcanic weathered formations this programme emphasizes the fundamental role in such tropical volcanic islands of a good knowledge of the weathered formations for the assessment of most natural hazards this initial hazard mapping represented the first step to achieve specific regulatory risk prevention plans for an efficient land use risk mitigation and reduction policy in mayotte

landslides in a densely populated county at the footslopes of mount elgon uganda characteristics and causal factors manjiya county on the ugandan slopes of mount elgon is a densely populated mountainous area where landslides have been reported since the beginning of the twentieth century the numerous fatalities and the damage done during the extreme rainfall events of 1997 to 1999 drew attention to this phenomenon in order to better understand the causal factors of these landslides 98 recent landslides in the study area mostly debris slumps were mapped and investigated together they displaced 11 millions m 3 of slope material statistical analysis shows that landslides dominate on steep concave slope segments that are oriented to the dominant rainfall direction northeast and at a relatively large distance from the water divide based on landslide occurrence and impact four different zones can be distinguished within the study area causal factors as well as landslide characteristics differ greatly between the four zones besides the fact that steep slopes high rainfall and typical soil properties and stratification turn manjiya into an inherently unstable area human interference cannot be neglected whereas deforestation has reduced the stability of the shallow soils on the eastern slopes of the study area the excavation of slopes mainly for house building is an important destabilizing factor for the western slopes the growing population density not only increases the risk on damage but hampers the search for solutions for the landslide problem as well d 2005 elsevier b v all rights reserved

japan s sediment flux to the pacific ocean revisited abstract quantifying volumes and rates of delivery of terrestrial sediment from island arcs to subduction zones is indispensable for refining estimates of the thickness of trench fills that may eventually control the location and timing of submarine landslides and tsunami generating mega earthquakes despite these motivating insights knowledge about the rates of erosion and sediment export from the japanese islands to their pacific subduction zones remains patchy regardless of the increasing availability of highly resolved data on surface deformation climate geology and topography traditionally natural erosion rates across the island arc have been estimated from regression of topographic catchment metrics and reservoir sedimentation rates that were recorded over several years to decades we review current research in this context correct for a systematic bias in one of the most widely used predictions and present new estimates of decadal to millennial scale erosion rates of japan s terrestrial inner forearc we draw on several independent and unprecedented inventories of mass wasting reservoir sedimentation and concentrations of cosmogenic 10be in river sands we find that natural 10be derived denudation rates of several mm yr 1 in the japanese alps have been sustained over several centuries to millennia and are within error roughly consistent with sediment yields inferred from artificial reservoir sedimentation local exceptions may likely result from release of sediment storage or regional landsliding episodes that trigger transient sediment pulses our synopsis further reveals that catchments draining japan s eastern seaboard differ distinctly in their tectonic lithological topographic and climatic characteristics between the tohoku japanese alps and nankai inner forearc segments which is underscored by a marked asymmetric pattern of erosion rates along the island arc erosion rates are highest up to at least 3 mm yr 1 in the japanese alps that mark the collision of two subduction zones where high topographic relief hillslope and bedrock channel steepness foster rapid denudation by mass wasting comparable if slightly lower erosion rates characterise the nankai inner forearc in southwest japan most likely due to higher typhoon driven rainfall totals and variability rather than its high topographic relief in contrast our estimated erosion and flux rates are lowest in the tohoku inner forearc catchments that feed sediment into the japan trench we conclude that collisional mountain building of the japanese alps drives some of the highest erosion rates in the island arc despite similar uplift and precipitation controls in southwest japan we infer that prior to extensive river damming reservoir construction and coastal works the gross of japan s total sediment export to the pacific ocean entered the accretionary margin of the nankai trough as opposed to the comparatively sediment starved japan trench compared to documented contemporary rates of sediment flux from mountainous catchments elsewhere in the pacific the rivers draining japan s inner forearc take an intermediate position despite high relief steep slopes very high seismicity and frequent rainstorms however the average rates of millennial scale denudation in the japanese alps particularly are amongst the highest reported worldwide local mismatches between these late holocene and modern rates emphasise the anthropogenic fingerprint on sediment retention that may have significantly reduced the island arc s mass flux to its subduction zones as is the case elsewhere in east and southeast asia

tectonics fracturing of rock and erosion 1 we argue that by fracturing rock not by raising it relative to base level tectonics plays its most important role in causing rapid incision of valleys and rapid erosion of hillslopes tectonic deformation riddles the upper crust with fractures which not only provide avenues for water flow and thus promote weathering and further disintegration of rock but also fragment bedrock into debris that is readily extracted and transported by surface processes bends in active faults require straining of adjacent rock masses aftershocks that occur subsequent to slip on primary faults reflect penetrative brittle deformation of the upper crust at least some aftershocks must nucleate or lengthen cracks which contribute to the comminution of these rock masses scaling rules suggest that dimensions of ruptures for very small m 2 earthquakes can be meters or less the gutenberg richter recurrence relationship implies that such earthquakes are common as high magnification seismographs in low noise environments confirm moreover large differences among fault plane solutions for aftershocks show that the small faults on which they occur are not parallel to one another some faults must intersect thus the upper crust in tectonically active regions should be fragmented into blocks down to the scale of boulders or smaller dismembered rock arrives at the earth s surface already prepared to be transported away as a corollary both deeply exhumed lower crust and posttectonic igneous rock never deformed under brittle conditions and not deformed recently should be less susceptible to detachment and subsequent transport than fractured rock

geologic topographic and climatic controls in landslide hazard assessment using gis modeling a case study of souk ahras region ne algeria abstract landslides are the most common hazard in mountainous regions of northeast algeria in this study landslide hazard zonation of souk ahras province was carried out using a raster based gis and statistical processing landslide locations were defined from interpretation of aerial photographs and field surveys rotational planar and complex landslides were identified to reveal the controlling factors of landslides a temporal distribution of 603 recognized landslides 1981 2011 is compared with the monthly precipitation variation indicating a strong correlation between precipitation and landslide occurrence the correlation between landslide and lithology slope angle and elevation shows the same results tabular data maps and satellite images were collected processed and constructed into a spatial database in a gis platform the factors that influence landslide occurrence such as slope angle slope exposition and elevation were derived from the dem lithology soil deposits and faults were digitalized from the geologic maps roads streams and timber were extracted from landsat image precipitation was krigged from pluviometric measurement dataset different classes of thematic layers were assigned a corresponding rating value as attribute information and an attribute map was generated for each data layer in the gis landslide hazard areas were assessed and mapped using the landslide occurrence and permanent factor maps by applying a probabilistic method with a logistic regression approach the results of the analysis were verified using landslides location map compared with the probability model the resulting map can be used to mitigate this hazard and to plan land use and urbanization

landslide inventory maps new tools for an old problem landslides are present in all continents and play an important role in the evolution of landscapes they also represent a serious hazard in many areas of the world despite their importance we estimate that landslide maps cover less than 1 of the slopes in the landmasses and systematic information on the type abundance and distribution of landslides is lacking preparing landslide maps is important to document the extent of landslide phenomena in a region to investigate the distribution types pattern recurrence and statistics of slope failures to determine landslide susceptibility hazard vulnerability and risk and to study the evolution of landscapes dominated by mass wasting processes conventional methods for the production of landslide maps rely chiefly on the visual interpretation of stereoscopic aerial photography aided by field surveys these methods are time consuming and resource intensive new and emerging techniques based on satellite airborne and terrestrial remote sensing technologies promise to facilitate the production of landslide maps reducing the time and resources required for their compilation and systematic update in this work we first outline the principles for landslide mapping and we review the conventional methods for the preparation of landslide maps including geomorphological event seasonal and multi temporal inventories next we examine recent and new technologies for landslide mapping considering i the exploitation of very high resolution digital elevation models to analyze surface morphology ii the visual interpretation and semi automatic analysis of different types of satellite images including panchromatic multispectral and synthetic aperture radar images and iii tools that facilitate landslide field mapping next we discuss the advantages and the limitations of the new remote sensing data and technology for the production of geomorphological event seasonal and multi temporal inventory maps we conclude by arguing that the new tools will help to improve the quality of landslide maps with positive effects on all derivative products and analyses including erosion studies and landscape modeling susceptibility and hazard assessments and risk evaluations

prediction of the occurrence of slope instability phenomenal through gis based hazard zonation slope instability hazard assessment is based on the analysis of the terrain conditions at sites where slope failures occurred in the past for the analysis of the causative factors the application of geographic information systems gis is an essential tool in the data analysis and subsequent hazard assessment three scale levels of hazard mapping are defined a direct experience driven mapping at reconnaissance level a statistical approach to determine the causative factors in a quantitative susceptibility mapping and a methodology at large scale making using of deterministic models

sediment yield in africa abstract several studies have compiled and analysed measured contemporary catchment sediment yield sy t km 2 y 1 values for various regions of the world although this has significantly contributed to our understanding of sy africa remains severely underrepresented in these studies the objective of this article is therefore 1 to review and compile available sy data for africa 2 to explore the spatial variability of these sy data and 3 to examine which environmental factors explain this spatial variability a literature review resulted in a dataset of sy measurements for 682 african catchments from 84 publications and reports representing more than 8340 catchment years of observations these catchments span eight orders of magnitude in size and are relatively well spread across the continent a description of this dataset and comparison with other sy datasets in terms of spatial and temporal distribution and measurement quality is provided sy values vary between 0 2 and 15 699 t km 2 y 1 median 160 t km 2 y 1 average 634 t km 2 y 1 the highest sy values occur in the atlas region with sy values frequently exceeding 1000 t km 2 y 1 also the rift region is generally characterised by relatively high sy values while rivers in western and central africa have generally low sy values spatial variation in sy at the continental scale is mainly explained by differences in seismic activity topography vegetation cover and annual runoff depth other factors such as lithology catchment area or reservoir impacts showed less clear correlations the results of these analyses are discussed and compared with findings from other studies based on our results we propose a simple regression model to simulate sy in africa although this model has a relatively low predictive accuracy 40 it simulates the overall patterns of the observed sy values well potential explanations for the unexplained variance are discussed and suggestions for further research that may contribute to a better understanding of sy in africa are made

bedrock fracturing threshold hillslopes and limits to the magnitude of bedrock landslides abstract bedrock fracturing and rock strength are widely believed to influence landscape morphology and erosional resistance yet understanding of the quantitative relationship between rock mass strength and landscape evolution remains limited here we present a new application of seismic refraction surveys that uses variations in seismic velocity to interpret differences in bedrock fracture density with depth we use a comparative study of fiordland and the western southern alps of new zealand to examine how differences in rock type and bedrock fracturing influence landscape morphology and landslide response to rock uplift in both regions slopes appear invariant with differential rock uplift rates and slope distributions reveal modal hillslope angles of 32 the majority of landslides initiate on slopes steeper than the modal hillslope angle however landslide magnitude frequency distributions reveal order of magnitude differences between the regions with fiordland experiencing considerably smaller and less frequent landsliding events landslide driven denudation rates of 9 mm yr in the western southern alps and between 0 1 and 0 3 mm yr in fiordland approximate estimates of long term rock uplift rates for each region the invariance of hillslope angles near normal slope distributions predominance of landslide initiation on slopes steeper than modal values and the apparent balance between rates of uplift and landslide driven erosion suggest that hillslopes in both regions are at threshold angles their similar modal slopes further suggest that both ranges are characterized by equivalent rock mass strength despite striking differences in lithology additionally our seismic analysis reveals nearly identical surface p wave velocities the unexpected equivalence of both modal slopes and surface velocities between these lithologically distinct ranges is attributed to contrasting degrees of surface fracturing that have differentially affected the intact rock properties such that they now yield equivalent surface velocities and hillslope scale strengths given that surface fractures help regulate threshold angles by modulating hillslope strength we propose that shallow seismic velocities may provide a quantitative proxy for rock mass strength we define two contrasting fracture and landsliding environments in fiordland dense geomorphic fracturing that is focused within the shallow subsurface appears to limit the depth and magnitude of most bedrock landslides conversely in the western southern alps tectonic forces produce pervasive fracturing with depth that results in larger and deeper landslides our data suggest that bedrock fracturing at the earth s surface modulates threshold hillslope angles whereas the depth of bedrock fracturing influences the magnitude and frequency of landslide response to tectonic rock uplift

prolonged seismically induced erosion and the mass balance of a large earthquake large earthquakes deform the earth s surface and drive topographic growth in the frontal zones of mountain belts they also induce widespread mass wasting reducing relief the sum of these two opposing effects is unknown using a time series of landslide maps and suspended sediment transport data we show that the mw7 6 chi chi earthquake in taiwan was followed by a period of enhanced mass wasting and fluvial sediment evacuation peaking at more than five times the background rate and returning progressively to pre earthquake levels in about six years therefore it is now possible to calculate the mass balance and topographic effect of the earthquake the choshui river has removed sediment representing more than 30 of the added rock mass from the epicentral area this has resulted in a reduction of surface uplift by up to 0 25 m or 35 of local elevation change and a reduction of the area where the chi chi earthquake has built topography for other large earthquakes erosion may evolve in similar predictable ways reducing the efficiency of mountain building in fold and thrust belts and the topographic expression of seismogenic faults prolonging the risk of triggered processes and impeding economic regeneration of epicentral areas

the application of gis based logistic regression for landslide susceptibility mapping in the kakuda yahiko mountains central japan as a first step forward in regional hazard management multivariate statistical analysis in the form of logistic regression was used to produce a landslide susceptibility map in the kakuda yahiko mountains of central japan there are different methods to prepare landslide susceptibility maps the use of logistic regression in this study stemmed not only from the fact that this approach relaxes the strict assumptions required by other multivariate statistical methods but also to demonstrate that it can be combined with bivariate statistical analyses bsa to simplify the interpretation of the model obtained at the end in susceptibility mapping the use of logistic regression is to find the best fitting function to describe the relationship between the presence or absence of landslides dependent variable and a set of independent parameters such as slope angle and lithology here an inventory map of 87 landslides was used to produce a dependent variable which takes a value of 0 for the absence and 1 for the presence of slope failures lithology bed rock slope relationship lineaments slope gradient aspect elevation and road network were taken as independent parameters the effect of each parameter on landslide occurrence was assessed from the corresponding coefficient that appears in the logistic regression function the interpretations of the coefficients showed that road network plays a major role in determining landslide occurrence and distribution among the geomorphological parameters aspect and slope gradient have a more significant contribution than elevation although field observations showed that the latter is a good estimator of the approximate location of slope cuts using a predicted map of probability the study area was classified into five categories of landslide susceptibility extremely low very low low medium and high the medium and high susceptibility zones make up 8 87 of the total study area and involve mid altitude slopes in the eastern part of kakuda mountain and the central and southern parts of yahiko mountain

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

the f utility to account for pre failure topography in data driven landslide susceptibility modelling abstract the aim of most data driven landslide susceptibility assessments is to generate a map that depicts zones that are prone to future landsliding the underlying algorithms are usually trained on the basis of a dichotomous response i e landslide presences and absences and a predictor set that includes derivatives of a digital terrain model dtm literature indicates that numerous landslide susceptibility studies are built upon topographic variables which were derived from the most recently available dtm thus the available landslide information may mostly refer to events that were triggered before the topographic data was acquired the resultant predictors are therefore likely to depict the archetypal morphometric signature of past landslides i e the post failure topography however landslide susceptible terrain which did not yet fail but may fail in the future may not exhibit such a distinct post landslide topographic footprint the delineation of landslide prone terrain may therefore require an explicit consideration of the pre landslide morphology i e pre failure topography this research aimed to explore differences among landslide susceptibility models that were based on post failure topography and their counterparts associated with an approximated pre failure topographic situation the objective was to ascertain the situations in which pre failure topography should explicitly be considered or can be ignored in this context a particular emphasis was set on elaborating the influence of spatial modelling resolution and landslide dimension the research focused on a 12 km2 test site located in the walgau region vorarlberg austria where a comprehensive shallow landslide inventory was available the methodical framework consisted of pairwise confrontations of models trained on post failure topographies with their counterparts based on approximated pre failure situations mixed effects logistic regression modelling was applied separately for five raster resolutions from 1 to 25 m and two landslide size groups smaller vs larger landslides to assess the associated effects of dtm generalization and landslide size the results were evaluated by interpreting the discriminatory power of predictors modelled associations predictor importance prediction skills and the spatial prediction pattern the findings showed that dissimilarities between post failure models and their pre failure equivalents were controlled by the selected raster resolution and the size of the underlying landslides the highest degree of mismatch was detected among models that were based on a detailed topographic representation i e high raster resolution and landslides which were associated with a larger morphometric footprint i e larger landslides however these differences were observed to diminish systematically with a decreasing raster resolution the results indicate that a consideration of pre failure topography is dispensable whenever the landslide data consists of smaller events whilst modelling is conducted at a comparatively coarse resolution in contrast landslide susceptibility modelling based on larger landslides may benefit from accounting for post failure topography even though obtained prediction skills might indicate a contrary tendency

spatial patterns of old deep seated landslides a case study in the northern ethiopian highlands abstract during the last decade slope failures were reported in a 500 km2 study area in the geba werei catchment northern ethiopia a region where landslides were not considered an important hazard before field observations however revealed that many of the failures were actually reactivations of old deep seated landslides after land use changes therefore this study was conducted 1 to explore the importance of environmental factors controlling landslide occurrence and 2 to estimate future landslide susceptibility a landslide inventory map of the study area derived from aerial photograph interpretation and field checks shows the location of 57 landslides and six zones with multiple landslides mainly complex slides and debris flows in total 14 8 of the area is affected by an old landslide for the landslide susceptibility modelling weights of evidence wofe was applied and five different models were produced after comparison of the models and spatial validation using receiver operating characteristic curves and kappa values a model combining data on elevation hillslope gradient aspect geology and distance to faults was selected this model confirmed our hypothesis that deep seated landslides are located on hillslopes with a moderate slope gradient i e 5 13 the depletion areas are expected on and along the border of plateaus where weathered basalts rich in smectite clays are found and the landslide debris is expected to accumulate on the amba aradam sandstone and upper antalo limestone as future landslides are believed to occur on inherently unstable hillslopes similar to those where deep seated landslides occurred the classified landslide susceptibility map allows delineating zones where human interventions decreasing slope stability might cause slope failures the results obtained demonstrate that the applied methodology could be used in similar areas where information on the location of landslides is essential for present day hazard analysis

prediction of landslide susceptibility using rare events logistic regression a case study in the flemish ardennes belgium abstract in this article a statistical multivariate method i e rare events logistic regression is evaluated for the creation of a landslide susceptibility map in a 200 km2 study area of the flemish ardennes belgium the methodology is based on the hypothesis that future landslides will have the same causal factors as the landslides initiated in the past the information on the past landslides comes from a landslide inventory map obtained by detailed field surveys and by the analysis of lidar light detection and ranging derived hillshade maps information on the causal factors e g slope gradient aspect lithology and soil drainage was extracted from digital elevation models derived from lidar and from topographical lithological and soil maps in landslide affected areas however we did not use the present day hillslope gradient in order to reflect the hillslope condition prior to landsliding the pre landslide hillslope was reconstructed and its gradient was used in the analysis because of their limited spatial occurrence the landslides in the study area can be regarded as rare events rare events logistic regression differs from ordinary logistic regression because it takes into account the low proportion of 1s landslides to 0s no landslides in the study area by incorporating three correction measures the endogenous stratified sampling of the dataset the prior correction of the intercept and the correction of the probabilities to include the estimation uncertainty for the study area significant model results were obtained with pre landslide hillslope gradient and three different clayey lithologies being important predictor variables receiver operating characteristic roc curves and the kappa index were used to validate the model both show a good agreement between the observed and predicted values of the validation dataset based on a qualified judgement the created landslide susceptibility map was classified into four classes i e very high high moderate and low susceptibility if interpreted correctly this classified susceptibility map is an important tool for the delineation of zones where prevention measures are needed and human interference should be limited in order to avoid property damage due to landslides

spatial patterns causes and consequences of landslides in the gilgel gibe catchment sw ethiopia abstract the gilgel gibe catchment in sw ethiopia is one of the areas in east africa affected by landslides to better understand the patterns and the causal factors of these landslides all landslides in a small study area 14 km in the hilly parts of the gilgel gibe catchment were mapped and analyzed in total 60 landslides were mapped these landslides caused a displacement of 1 million m slope material which corresponds to a mean displaced volume of 50 ton ha 1 y 1 in the last 20 years moreover many landslides deliver directly sediment to the rivers and hence increase the sediment load in the rivers this soil loss to the rivers was estimated at 11 ton ha 1 y 1 during the same period high annual rainfall ca 2000 mm y 1 lithological and pedological properties and to a lesser extent steep 16 slopes turn the area into an inherent unstable situation and can be indicated as preconditions for the landslides in the study area distance to rivers is significantly the most important precondition as slopes near rivers are less stable than slopes further away from the rivers this is mainly caused by river incision and bank erosion which often occur in the area and which can be attributed to increased runoff due to deforestation over the past 20 years therefore recent deforestation caused more shallow landslides but also indirectly more deep seated landslides close to the rivers heavy rainfall is indicated as the main triggering factor for almost all landslides

dynamic earth system and ecological controls of rainfall initiated landslides abstract rainfall initiated landslides continue to inflict damages and loss of life throughout the world processes and mechanisms revealed from hydrological geomorphic geotechnical pedological geological hydrochemical and biological investigations have advanced our understanding of these effects on slope stability however the interactions amongst these processes and attributes as they affect the initiation and propagation of landslides are not as well understood too often landslide studies are conducted from only one or at most two of these perspectives moreover while precipitation and hydrology are recognized as dynamic influences the earth system and ecological effects are often assumed to be static we assess the interplay of these processes related to landslides triggered by positive pore water accretion and loss of soil suction each of these conditions arguably requires a different view on the processes that cause slope failure and predictive approaches this review starts from the perspective of dynamic adapting earth and ecological systems and discusses how these attributes relate to landslide initiation mode location and timing specifically the role that large and small scale preferential flow plays in both contributing to and mitigating instability is elucidated including effects of bedrock exfiltration we also examine how and under what conditions these pathways manifest in different soils lithology and landforms the multiple effects of rhizosphere processes on slope stability are discussed including root reinforcement evaporation from canopies and litter layers transpiration and the role of root structure affecting preferential flow paths rainfall initiated landslides involve highly dynamic hydrologic earth surface and ecological processes that persist over a range of spatial and temporal scales however guidance for overcoming these challenges has been elusive a conceptual framework is presented to shed light on these dynamic and interactive processes that should lend insights into why and when certain slopes fail during storms while other seemingly similar slopes do not fail such advances will benefit landslide hazard assessments and disaster responsiveness protocols

the catastrophic geomorphological processes in humid tropical africa a case study of the recent landslide disasters in cameroon abstract a retrospective analysis of data from the last three decades clearly indicates an upward trend in the number of landslides and mudflows in cameroon their impact on human beings environment and properties has increased considerably for example since june 2001 several cases have been recorded among which two resulted in significant human losses twenty three deaths in june 2001 in limbe town twenty five others in july 2003 at magha and its surroundings in the bamboutos mountains these last two events were really spectacular and may be sounding the alarm of a geomorphological crisis in the region according to each case several tens or hundreds of landslides of different types and magnitudes occurred within a few minutes or hours extending over an area of several tens of square kilometres the reasons for this catastrophic evolution in the geomorphological processes in cameroon are natural and anthropogenic among others the natural factors are the changing climatic conditions with the occurrence of very exceptional rainfalls and the uneven topography of the affected zones for example with very steep slopes as in the magha zone of which area about fifty percent is above twenty degrees the anthropogenic factors are also very relevant with the increasing human pressure on the environment characterised by the extension and or intensification of the agro pastoral activities in the rural areas and the anarchical settlement on the sloping urban zones

a geomorphological assessment of landslide origin at bukavu democratic republic of the congo abstract bukavu on the south coast of lake kivu in the democratic republic of the congo suffers from slow but never ending landsliding this leads to the continuous degradation and destruction of houses buildings and of the roads waterworks and sewerage infrastructure in several districts of the town research of mass wasting processes is hampered by the limited geotechnical and hydrogeological information concerning the deeply weathered tertiary and quaternary lavas there is also a disagreement about the exact location of active faults believed to play a role in the mass wasting additionally there is little information about the exact location and the rate of soil movements and whether ground instability is caused by tectonics and seismics or by increase in hydrostatic pressure based on aerial photographic interpretation landslides cover more than 15 of the town of bukavu thirty one landslides occur outside the bukavu microrift and do not contact active faults rather they occur in actively incising river basins ostensibly caused by neotectonic activity four from the six landslides within the micrograben are bigger and wider than the others apparently governed by pre existing tectonically induced landforms they are adjacent to or crossed by active faults they also fall far below the envelope of topographic thresholds for landslides established for north america and verified in rwanda therefore this threshold a combination of slope at the head of the slide and surface drained to it seems a promising tool to discriminate hydrologically from tectonically seismically induced landslides recent soil movements in bukavu generally correspond to landslide distribution portrayed on the geomorphologic map most bukavu soil movements occur on previous slides therefore from an engineering geologic standpoint old landslides should be avoided or if economically feasible be mitigated

global patterns of loss of life from landslides global loss of life from landslides is poorly quantifi ed a global data set of fatalities from nonseismically triggered landslides that resulted in loss of life between a d 2004 and 2010 permits for the fi rst time proper quantifi cation of impacts and spatial distributions in total 2620 fatal landslides were recorded worldwide during the 7 yr period of the study causing a total of 32 322 recorded fatalities these total numbers of landslides and victims are an order of magnitude greater than other data sets have indicated but analysis of the data suggests that it may still slightly underestimate the true human costs the majority of human losses occur in asia especially along the himalayan arc and in china this geographical concentration dominates the annual landslide cycle which peaks in the northern hemisphere summer months finally numbers of fatalities per event show a fat tailed power law distribution with the density of landslides being moderately correlated with the population density on a national basis

the added value of a regional landslide susceptibility assessment the western branch of the east african rift abstract predicting landslide occurrence is of key importance for understanding the geomorphological development of mountain environments as well as to assess the potential risk posed by landsliding to human societies in such environments global landslide susceptibility models use a generic model formulation to predict landslide susceptibility anywhere on the planet from openly available data regional models on the contrary use local information on landslide occurrence to constrain model parameters and may also benefit from better spatial information with respect to controlling factors this study aims to investigate the added value of the construction of regional landslide susceptibility models versus global and continental models in the western branch of the east african rift a data scarce landslide prone tropical environment first a comprehensive landslide database containing 6446 instances was compiled for the study area using google earth imagery second three regional data driven landslide susceptibility models were developed third the efforts to construct these regional models were quantified by analysing how their quality is impacted by 1 the use of more accurate regional peak ground acceleration and geology data and 2 an increasing inventory size fourth regional and global continental models were compared in terms of predictive power and geomorphological plausibility we observe that global continental landslide susceptibility models are capable of identifying landslide prone areas but lack prediction power and geomorphological plausibility when compared to our regional models importantly this difference in quality is not driven by the use of more accurate and detailed geology and peak ground acceleration data but rather by the use of a detailed regional landslide inventory to calibrate the models we also show that the model quality only increases marginally beyond a certain inventory size we conclude that the regional landslide susceptibility assessment does provide an added value compared to existing global models in terms of geomorphological plausibility and model performance whereby the largest gain is to be found in the construction of a regional landslide inventory rather than the investment in more detailed covariates or the application of more complex modelling techniques the latter suggests that the role of controlling variables depends to some extent on the regional context making adequate susceptibility predictions proves difficult when local conditions are not accounted for by means of a regional inventory

modeling typhoon and earthquake induced landslides in a mountainous watershed using logistic regression landslides can be caused by storms and earthquakes most logistic regression models proposed in recent years have been targeted at rainfall induced landslides in areas such as taiwan where landslides can be triggered by typhoons tropical cyclones and earthquakes a rainfall induced model is insufficient because it provides only a partial explanation of landslide occurrence and overlooks the potential effect of earthquakes on typhoon triggered landslides this study used landslides triggered by a major earthquake and a typhoon prior to the earthquake to develop an earthquake induced model and a typhoon induced model the models were then validated by using landslides triggered by three typhoons after the earthquake according to the results typhoon triggered landslides tended to be near stream channels and earthquake triggered landslides were more likely to be near ridge lines moreover a major earthquake could still affect the locations of typhoon triggered landslides 6 years after the earthquake this study therefore demonstrates that an earthquake induced model both sheds light on the environmental factors for triggering landslides and augments a rainfall induced model in its predictive capability in areas such as taiwan

classification and distribution of recent historic landslides in southern nigeria abstract recent historic landslides in southern nigeria have been catalogued classified and analysed in terms of their seasonal geologic and topographic distributions it is found that 58 of the landslides fall within the complex the distribution reveals that both sedimentary and non sedimentary igneous and metamorphic terrains are vulnerable with the latter yielding a majority 73 of the slide debris flows implications of these distributions are discussed

exploring discrepancies between quantitative validation results and the geomorphic plausibility of statistical landslide susceptibility maps abstract empirical models are frequently applied to produce landslide susceptibility maps for large areas subsequent quantitative validation results are routinely used as the primary criteria to infer the validity and applicability of the final maps or to select one of several models this study hypothesizes that such direct deductions can be misleading the main objective was to explore discrepancies between the predictive performance of a landslide susceptibility model and the geomorphic plausibility of subsequent landslide susceptibility maps while a particular emphasis was placed on the influence of incomplete landslide inventories on modelling and validation results the study was conducted within the flysch zone of lower austria 1 354 km 2 which is known to be highly susceptible to landslides of the slide type movement sixteen susceptibility models were generated by applying two statistical classifiers logistic regression and generalized additive model and two machine learning techniques random forest and support vector machine separately for two landslide inventories of differing completeness and two predictor sets the results were validated quantitatively by estimating the area under the receiver operating characteristic curve auroc with single holdout and spatial cross validation technique the heuristic evaluation of the geomorphic plausibility of the final results was supported by findings of an exploratory data analysis an estimation of odds ratios and an evaluation of the spatial structure of the final maps the results showed that maps generated by different inventories classifiers and predictors appeared differently while holdout validation revealed similar high predictive performances spatial cross validation proved useful to expose spatially varying inconsistencies of the modelling results while additionally providing evidence for slightly overfitted machine learning based models however the highest predictive performances were obtained for maps that explicitly expressed geomorphically implausible relationships indicating that the predictive performance of a model might be misleading in the case a predictor systematically relates to a spatially consistent bias of the inventory furthermore we observed that random forest based maps displayed spatial artifacts the most plausible susceptibility map of the study area showed smooth prediction surfaces while the underlying model revealed a high predictive capability and was generated with an accurate landslide inventory and predictors that did not directly describe a bias however none of the presented models was found to be completely unbiased this study showed that high predictive performances cannot be equated with a high plausibility and applicability of subsequent landslide susceptibility maps we suggest that greater emphasis should be placed on identifying confounding factors and biases in landslide inventories a joint discussion between modelers and decision makers of the spatial pattern of the final susceptibility maps in the field might increase their acceptance and applicability

increase in basin sediment yield from landslides in storms following major seismic disturbance the landslide area along the tachia river catchment of central taiwan was investigated using the remote sensing images of various typhoon and earthquake events taken from 1996 to 2004 and the sediment discharge measured at hydrometric stations our findings indicate that 88 of the coseismic landslides triggered by the 1999 chi chi earthquake were first time occurrences after the chi chi earthquake 59 of the landslide area was reactivated during typhoon toraji and 66 during typhoon mindulle the landslides prone to reactivation were on the formations with closely spaced discontinuities it is suggested that further rock mass defects in the formations were added or opened by the earthquake and that the landslide areas continued to extend until the end of 2004 post 1999 rainstorms delivered large amounts of colluvial sediment into the main channel leading to a 2 fold increase in post seismic sediment discharge while the precipitation was only half that of the pre earthquake rate

comparison of two landslide susceptibility assessments in the champagne ardenne region france abstract the vineyards of the montagne de reims are mostly planted on steep south oriented cuesta fronts receiving a maximum of sun radiation due to the location of the vineyards on steep hillslopes the viticultural activity is threatened by slope failures this study attempts to better understand the spatial patterns of landslide susceptibility in the champagne ardenne region by comparing a heuristic qualitative and a statistical quantitative model in a 1120 km study area the heuristic landslide susceptibility model was adopted from the bureau de recherches geologiques et minieres the gegeaa reims university and the comite interprofessionnel du vin de champagne in this model expert knowledge of the region was used to assign weights to all slope classes and lithologies present in the area but the final susceptibility map was never evaluated with the location of mapped landslides for the statistical landslide susceptibility assessment logistic regression was applied to a dataset of 291 old holocene landslides the robustness of the logistic regression model was evaluated and roc curves were used for model calibration and validation with regard to the variables assumed to be important environmental factors controlling landslides the two models are in agreement they both indicate that present and future landslides are mainly controlled by slope gradient and lithology however the comparison of the two landslide susceptibility maps through 1 an evaluation with the location of mapped old landslides and through 2 a temporal validation with spatial data of recent 1960 1999 n 48 and very recent 2000 2008 n 46 landslides showed a better prediction capacity for the statistical model produced in this study compared to the heuristic model in total the statistically derived landslide susceptibility map succeeded in correctly classifying 81 0 of the old and 91 6 of the recent and very recent landslides on the susceptibility map derived from the heuristic model on the other hand only 54 6 of the old and 64 0 of the recent and very recent landslides were correctly classified as unstable hence the landslide susceptibility map obtained from logistic regression is a better tool for regional landslide susceptibility analysis in the study area of the montagne de reims the accurate classification of zones with very high and high susceptibility allows delineating zones where viticulturists should be informed and where implementation of precaution measures is needed to secure slope stability

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

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

spatial and temporal analysis of a global landslide catalog abstract landslide inventories are critical to support investigations of where and when landslides have happened and may occur in the future however there is surprisingly little information on the historical occurrence of landslides at the global scale this paper presents a new publicly available global landslide catalog glc which is based on media reports online databases and other sources this database is currently available at http ojo streamer herokuapp com the 5741 points in the glc provide a foundation for evaluating spatial and temporal trends in landslide activity from 2007 to 2013 globally landslides were reported most frequently from july to september most events occurred in asia north america and southeast asia in contrast fewer than 5 of the fatalities were reported in north america suggesting a significant amount of under reporting in other regions as well as potential discrepancies between developing and developed regions reported landslide events were also compared to satellite based precipitation estimates from the tropical rainfall measuring mission trmm to evaluate the co occurrence of extreme precipitation and landslide activity of the 3550 points considered in a subset of the glc approximately 60 of the reported landslides have daily precipitation exceeding the 95th percentile of precipitation calculated over a 14 year trmm record for the same location this study also investigated how the recurrence interval of extreme precipitation corresponded to some of the most catastrophic landslide events in spite of several reporting and cataloging biases spatial and temporal analysis of the glc suggests that it is a valuable database for characterizing global patterns of landslide occurrence and evaluating relationships with extreme precipitation at regional and global scales

ultra high temperature metamorphism of metapelitic granulites from kondapalle eastern ghats belt implications for the indo antarctic correlation a suite of quartz and corundum bearing metapelitic granulites intruded by layered gabbronorite pyroxenite anorthosite at kondapalle eastern ghats belt preserves a multitude of reaction textures involving oxide and silicate minerals that attest to several prograde and retrograde reactions in the quartz bearing associations the reactions are a biotite sillimanite quartz garnet liquid b garnet sillimanite spinel magnetite quartz c fe2tio4 o2 ferrian ilmenite magnetite d reversal of reaction b e fe2o3 rich ilmenite plagioclase quartz fe2o3 poor ilmenite garnet o2 reactions in the corundum bearing associations are f spinel biotite sillimanite garnet liquid g biotite sillimanite garnet ti rich spinel corundum liquid h biotite sillimanite garnet corundum liquid i fe2tio4 feal2o4 o2 ferrian ilmenite fe3o4 al2o3 in ilmenite j garnet corundum spinel sillimanite to examine the paragenetic evolution of the metapelitic granulites a petrogenetic grid for the kfmash system at high temperatures and pressures involving quartz and corundum was constructed the sequence of inferred reactions documents an anticlockwise heating cooling path reintegrated compositions of spinel with 10 mol fe2tio4 and feldspars indicate ultra high temperature uht of metamorphism 1000 c comparable with the liquidus temperature of the enclosing magmatic rocks crystallization pressures inferred for the magmatic rocks and the pressure constraints imposed by the petrogenetic grid on the metapelite assemblages indicate that the emplacement of the igneous suite and the accompanying uht metamorphism occurred in the lower crust 8 kbar reported u pb cooling ages of monazite and allanite from a late pegmatite suggest the uht metamorphism to be older than 1600 ma the deduced p t history and the absence of grenvillian high grade metamorphism in the study area provide important constraints on the configuration of east gondwana in particular on the continuation of the napier rayner terrane boundary into the eastern ghats belt