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Mountain regions are typically characterized by rugged terrain which is susceptible to different types of landslides during high-intensity precipitation. Landslides account for billions of dollars of damage and many casualties, and are expected to increase in frequency in the future due to a projected increase of precipitation intensity. Early warning systems (EWS) are thought to be a primary tool for related disaster risk reduction and climate change adaptation to extreme climatic events and hydro- meteorological hazards, including landslides. EWS are highly complex systems, and it is therefore dificult to understand the effect of the different components and changing conditions on the overall performance, ultimately being expressed as human lives saved or structural damage reduced. In this paper we utilize a numerical model using 6 hour rainfall data as basic input. A threshold function based on a rainfall-intensity/duration relation was applied as a decision criterion for evacuation. Correct evacuation was assessed with a 'true' reference rainfall dataset versus a dataset of artificially reduced quality imitating the observation system component. Performance of the EWS using these rainfall datasets was expressed in monetary terms (i.e. damage related to false and correct evacuation). We applied this model to a landslide EWS in Colombia that has been implemented in recent years within a disaster prevention project. We evaluated the EWS against rainfall data with artificially introduced error and computed with multiple model runs the probabilisic damage functions depending on rainfall error. Then we modified the original precipitation pattern to reflect possible climatic changes e.g. change in annual precipitatin as well as change in precipitation intensity with annual values remaining constant. We let the EWS model adapt for changed conditions to function optimally. Our resuts show that for the same errors in rainfall measurements the systems performance degrades

Mountain regions are typically characterized by rugged terrain which is susceptible to different types of landslides during high-intensity precipitation. Landslides account for billions of dollars of damage and many casualties, and are expected to increase in frequency in the future due to a projected increase of precipitation intensity. Early warning systems (EWS) are thought to be a primary tool for related disaster risk reduction and climate change adaptation to extreme climatic events and hydrometeorological hazards, including landslides. EWS are highly complex systems, and it is therefore difficult to understand the effect of the different components and changing conditions on the overall performance, ultimately being expressed as human lives saved or structural damage reduced. In this paper we utilize a numerical model using 6 hour rainfall data as basic input. A threshold function based on a rainfall-intensity/duration relation was applied as a decision criterion for evacuation. Correct evacuation was assessed with a ‘true’ reference rainfall dataset versus a dataset of artificially reduced quality imitating the observation system component. Performance of the EWS using these rainfall datasets was expressed in monetary terms (i.e. damage related to false and correct evacuation). We applied this model to a landslide EWS in Colombia that has been implemented in recent years within a disaster prevention project. We evaluated the EWS against rainfall data with artificially introduced error and computed with multiple model runs the probabilistic damage functions depending on rainfall error. Then we modified the original precipitation pattern to reflect possible climatic changes e.g. change in annual precipitation as well as change in precipitation intensity with annual values remaining constant. We let the EWS model adapt for changed conditions to function optimally. Our results show that for the same errors in rainfall measurements the system’s performance degrad

Landslide early warning systems (EWS) are an important tool to reduce landslide risks, especially where the potential for structural protection measures is limited. However, design, implementation, and successful operation of a landslide EWS is complex and has not been achieved in many cases. Critical problems are uncertainties related to landslide triggering conditions, successful implementation of emergency protocols, and the response of the local population. We describe here the recent implementation of a landslide EWS for the Combeima valley in Colombia, a region particularly affected by landslide hazard. As in many other cases, an insufficient basis of data (rainfall, soil measurements, landslide event record) and related uncertainties represent a difficult complication. To be able to better assess the influence of the different EWS components, we developed a numerical model that simulates the EWS in a simplified yet integrated way. The results show that the expected landslide-induced losses depend nearly exponentially on the errors in precipitation measurements. Stochastic optimization furthermore suggests an increasing adjustment of the rainfall landslide-triggering threshold for an increasing observation error. These modeling studies are a first step toward a more generic and integrated approach that bears important potential for substantial improvements in design and operation of a landslide EWS.

Hochgebirgsregionen mit Gletschern und Permafrost reagieren sensitiv auf Temperaturveränderungen. Klimaänderungen können entsprechend einen Einfluss auf die Hangstabilität ausüben. Verschiedene Ereignisse in den letzten Jahren haben bestätigt, dass Eis- und Felslawinen eine besonders zerstörerische Wirkung haben können. Die Prozesse im Zusammenhang mit Hanginstabilitäten und Lawinenausbreitung sollten deshalb besser verstanden werden. In dieser Studie werden neue Forschungsarbeiten präsentiert, die einerseits hoch aufgelöste topographische Messungen einer grossen vergletscherten Wand in den Alpen (Monte Rosa) über 50 Jahre umfassen und dabei wichtige Erkenntnisse über Ursachen und Zusammenhänge der Fels- und Eisstürze erlauben. Andererseits wurden Laborexperimente und numerische Modellierungen von Lawinen durchgeführt, um den Einfluss von Eis auf die Lawinendynamik und -ausbreitung zu verstehen. Die Studie macht klar, dass die Gefahrenanalyse von Fels- und Eislawinen im Hochgebirge interdisziplinär angegangen werden muss mit einem besonderen Augenmerk auf Prozessinteraktionen.

In the course of glacier retreat, new glacier lakes can develop. As such lakes can be a source of natural hazards, strategies for predicting future glacier lake formation are important for an early planning of safety measures. In this article, a multi-level strategy for the identification of overdeepened parts of the glacier beds and, hence, sites with potential future lake formation, is presented. At the first two of the four levels of this strategy, glacier bed overdeepenings are estimated qualitatively and over large regions based on a digital elevation model (DEM) and digital glacier outlines. On level 3, more detailed and laborious models are applied for modeling the glacier bed topography over smaller regions; and on level 4, special situations must be investigated in-situ with detailed measurements such as geophysical soundings. The approaches of the strategy are validated using historical data from Trift Glacier, where a lake formed over the past decade. Scenarios of future glacier lakes are shown for the two test regions Aletsch and Bernina in the Swiss Alps. In the Bernina region, potential future lake outbursts are modeled, using a GIS-based hydrological flow routing model. As shown by a corresponding test, the ASTER GDEM and the SRTM DEM are both suitable to be used within the proposed strategy. Application of this strategy in other mountain regions of the world is therefore possible as well.

Rock-ice avalanches larger than 1x106 m3 are high magnitude low frequency events that may occur in all ice-covered high mountain areas around the world and can cause extensive damage if they reach populated regions. The temporal and spatial evolution of the seismic signature from two events was analyzed and recordings at selected stations were compared to numerical model results of avalanche propagation. The first event is a rock-ice avalanche from Iliamna volcano in Alaska which serves as a 'natural laboratory' with simple geometric conditions. The second one originated on Aoraki/Mt. Cook, New Zealand Southern Alps, and is characterized by a much more complex topography. A dynamic numerical model was used to calculate total avalanche momentum, total kinetic energy, and total frictional work rate, amongst other parameters. These three parameters correlate with characteristics of the seismic signature such as duration and signal envelopes, while other parameters such as flow depths, flow path and deposition geometry are well in agreement with observations. The total frictional work rate shows the best correlation with the absolute seismic amplitude suggesting that it may be used as an independent model evaluation criterion and in certain cases as model calibration parameter. The good fit is likely because the total frictional work rate represents the avalanche’s energy loss rate, part of which is captured by the seismometer. Deviations between corresponding calculated and measured parameters result from site and path effects which affect the recorded seismic signal, or indicate deficiencies of the numerical model. The seismic recordings contain additional information about when an avalanche reaches changes in topography along the runout path and enable more accurate velocity calculations. The new concept of direct comparison of seismic and avalanche modelling data helps to constrain the numerical model input parameters and to improve the understanding of (rock-ice) a

Fragile ecosystems, rapidly retreating glaciers, threatened water resources, extreme events and disasters in harsh environments, as well as demanding livelihood conditions make mountain regions particularly vulnerable to ongoing climate change. For many developing countries adequate response and short- to long-term adaptation strategies to climate change will be the big challenges over the coming decades. However, overcoming these challenges will also be fundamental to the future existence of many societies in mountain regions. The Andes in Peru is expected to be seriously affected by climate change.2 The Swiss and Peruvian governments have therefore joined forces – through the Swiss Agency for Development and Cooperation and the Ministry of Environment, respectively – to improve the scientific baseline for climate change adaptation, and to implement an adaptation programme in the Cusco and Apurímac regions of the Peruvian Andes. The Programa de Adaptación al Cambio Climático (PACC) was initiated in 2008 and is implemented by a non-governmental organization consortium including Intercooperation, Predes and Libélula. The programme is also supported by Peruvian and Swiss scientific institutions. The Swiss consortium is led by the University of Zurich and includes: Meteoswiss; Meteodat; Agroscope Reckenholz-Tänikon ART; the Swiss Federal Institute for Forest, Snow and Landscape Research WSL-SLF; and the University of Geneva.

The Andes as mountain regions worldwide, provide fundamental resources, not only for the local population. Due to the topographic characteristics, the potential for natural hazards is higher than elsewhere. In these areas, assessments of climate change impacts and the development of adequate adaptation strategies therefore become particular important. The data basis, however, is often scarce. Moreover, perceptions of changes and needs are often divergent between national and local levels, which make the implementation of adaptation measures a challenge. Taking the Peruvian Andes as an example, this paper aims at initiating a discussion about scientific baseline and integrative concepts needed to deal with the adverse effects of climate change in mountain regions.

Lahars frequently affect the slopes of ice-capped volcanoes. They can be triggered by volcano-ice interactions during eruptions but also by processes such as intense precipitation or by outbursts of glacial water bodies not directly related to eruptive activity. We use remote sensing, GIS and lahar models in combination with ground observations for an initial lahar hazard assessment on Iztaccíhuatl volcano (5230 m a.s.l.), considering also possible future developments of the glaciers on the volcano. Observations of the glacial extent are important for estimations of future hazard scenarios, especially in a rapidly changing tropical glacial environment. In this study, analysis of the glaciers on Iztaccíhuatl shows a dramatic retreat during the last 150 years: the glaciated area in 2007 corresponds to only 4% of the one in 1850 A.D. and the glaciers are expected to survive no later than the year 2020. Most of the glacial retreat is considered to be related to climate change but in-situ observations suggest also that geo- and hydrothermal heat flow at the summit-crater area can not be ruled out, as emphasized by fumarolic activity documented in a former study. However, development of crater lakes and englacial water reservoirs are supposed to be a more realistic scenario for lahar generation than sudden ice melting by rigorous volcano-ice interaction. Model calculations show that possible outburst floods have to be larger than ~5 • 105 m3 or to achieve an H/L ratio (Height/runout Length) of 0.2 and lower in order to reach the populated lower flanks. This threshold volume equals 2.4% melted ice of Iztaccíhuatl’s total ice volume in 2007, assuming 40% water and 60% volumetric debris content of a potential lahar. The model sensitivity analysis reveals important effects of the genetic type of the Digital Terrain Model (DTM) used on the results. As a consequence, the predicted affected areas can vary significantly. For such hazard zonation, we therefore suggest the use of d

Lahars are among themost serious and far-reaching volcanic hazards. In regions with potential interactions of lahars with populated areas and human structures the assessment of the related hazards is crucial for undertaking appropriate mitigating actions and reduce the associated risks. Modeling of lahars has become an important tool in such assessments, in particular where the geologic record of past events is insufficient. Mass-flow modeling strongly relies on digital terrain data. Availability of digital elevation models (DEMs), however, is often limited and thus an obstacle to lahar modeling. Remote-sensing technology has now opened new perspectives in generating DEMs. In this study, we evaluate the feasibility of DEMs derived from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Shuttle Radar TopographyMission (SRTM) for lahar modeling on Popocatépetl Volcano, Mexico. Two GIS-based models are used for lahar modeling, LAHARZ and a flow-routing-based debris-flow model (modified single-flow direction model, MSF), both predicting areas potentially affected by lahars. Results of the lahar modeling show that both the ASTER and SRTM DEMs are basically suitable for use with LAHARZ and MSF. Flow-path prediction is found to be more reliable with SRTM data, though with a coarser spatial resolution. Errors of the ASTER DEMaffecting the prediction of flow paths due to the sensor geometry are associated with deeply incised gorges with north-facing slopes. LAHARZ is more sensitive to errors of the ASTER DEMthan theMSF model. Laharmodeling with the ASTERDEMresults in a more finely spaced predicted inundation area but does not add any significant information in comparisonwith the SRTMDEM. Lahars at Popocatépetl are modeled with volumes of 1×105 to 8×106 m3 based on ice-melt scenarios of the glaciers on top of the volcano and data on recent and historical lahar events. As regards recently observed lahars, the travel distance of lahars of corresp

The Rio Santa valley in the Cordillera Blanca, Peru, has been repeatedly affected by severe glacial flood disasters in the past decades. The continuing high rate of glacier retreat has led to the formation and rapid growth of a large number of glacial lakes. Due to the risk of lake outburst floods, downstream communities are confronted with serious hazards. The regional capital of Huaraz is one of the major sites exposed to these hazards. Mainly due to a lack of resources, no systematic evaluation of the existing hazards and related risks has been performed so far, nor have adequate warning systems been installed. Strict financial limitations make a prioritization of mitigation measures a necessity. Vulnerability assessments are an effective tool to this end. In this article, we present a method to measure the vulnerability of Huaraz to hazards from glacial lake outbursts integrating both physical (ie hazards-related) and socioeconomic factors. The difficulty of quantifying socioeconomic variables and its combination with physical factors, as well as a lack of corresponding concepts, is a challenge for measuring vulnerability. The resulting map shows a high vulnerability for several parts of Huaraz. The results of this study thus make an important contribution to effectively addressing the identified protection deficit and to efficiently assigning the limited resources in the context of a developing country. However, this article also shows the strong need for more vulnerability research integrating both physical and social science components and related theoretical frameworks to be readily applied in practice.

The Monte Rosa east face, Italian Alps, is one of the highest flanks in the Alps (2200–4500m a.s.l.). Steep hanging glaciers and permafrost cover large parts of the wall. Since the end of the Little Ice Age (about 1850), the hanging glaciers and firn fields have retreated continuously. During recent decades, the ice cover of the Monte Rosa east face experienced an accelerated and drastic loss in extent. Some glaciers have completely disappeared. New slope instabilities and detachment zones of gravitational mass movements developed and enhanced rock fall and debris flow activity was observed. This study is based on multidisciplinary investigations and shows that most of the detachment zones of rock fall and debris flows are located in areas, where the surface ice disappeared only recently. Furthermore, most of these detachment zones are located in permafrost zones, for the most part close to the modelled and estimated lower boundary of the regional permafrost distribution. In the view of ongoing or even enhanced atmospheric warming and associated changes it is therefore very likely that the slope instabilities in the Monte Rosa east face will continue to represent a critical hazard source.

Climate change has a particularly strong impact in high-mountain regions, as rapidly shrinking glaciers demonstrate in a clear manner. These drastic geomorphic changes have important implications with respect to natural hazards. The aim of this paper is to document the possible processes and consequences of such hazards, and to demonstrate how modern remote sensing and modeling techniques can be used for rapid assessment of potentially endangered areas. Three case studies are presented from the European Alps, the Andes and the Caucasus. They refer to hazards associated with glacial lake formation and growth, and possible related lake outbursts, as well as massive mass movement processes due to destabilization of large glacierized mountain walls. Due to the remoteness and difficult access in most high-mountain regions, satellite remote sensing is a highly appropriate tool for monitoring purposes in these areas. We outline here the range of currently available satellite sensor data and show how it can be used to identify potential hazard sources. Based on the detected critical areas, we use mass movement propagation models embedded in Geographic Information Systems (GIS) to approximately delineate endangered areas. Such remote sensing and modeling based first-order hazard assessments are an important tool for further detailed studies, for land use planning, and for prevention and mitigation measures.

A massive rock/ice avalanche of about 100x10⁶m³ volume took place on the northern slope of the Kazbek massif, North Ossetia, Russian Caucasus, on 20 September 2002. The avalanche started as a slope failure, that almost completely entrained Kolka glacier, traveled down the Genaldon valley for 20km, was stopped at the entrance of the Karmadon gorge, and was finally succeeded by a distal mudflow which continued for another 15km. The event caused the death of ca. 140 people and massive destruction. Several aspects of the event are extraordinary, i.e. the large ice volume involved, the extreme initial acceleration, the high flow velocity, the long travel distance and particularly the erosion of a valley-type glacier, a process not known so far. The analysis of these aspects is essential for process understanding and worldwide glacial hazard assessments. This study is therefore concerned with the analysis of processes and the evaluation of the most likely interpretations. The analysis is based on QuickBird satellite images, field observations, and ice-, flow- and thermo-mechanical considerations. QuickBird is currently the best available satellite sensor in terms of ground resolution (0.6 m) and opens new perspectives for assessment of natural hazards. Evaluation of the potential of QuickBird images for assessment of high-mountain hazards shows the feasibility for detailed avalanche mapping and analysis of flow dynamics, far beyond the capabilities of conventional satellite remote sensing. It is shown that the avalanche was characterized by two different flows. The first one was comparable to a hyperconcentrated flow and was immediately followed by a flow with a much lower concentration of water involving massive volumes of ice. The high mobility of the avalanche is likely related to fluidization effects at the base of the moving ice/debris mass with high pore pressures and a continuous supply of water due to frictional melting of ice. The paper concludes with implication

On 20 September 2002, an enormous rock/ice slide and subsequent mud-flow occurred on the northern slope of the Kazbek massif, Northern Ossetia, Russian Caucasus. It started on the north-northeast wall of Dzhimarai-Khokh (4780 m a.s.l.) and seriously affected the valley of Genaldon/Karmadon. Immediate governmental actions, available scientific information, first reconstructions, hazard assessments and monitoring activities as well as initial expert judgments/recommendations are documented in order to enable more detailed analyses and modelling of the event by the wider scientific community. Among the most remarkable aspects related to this event are (1) the relation between the recent event and somewhat smaller but quite similar events that occurred earlier in historical times (1835, 1902), (2) the interactions between unstable local geological structures and complex geothermal and hydraulic conditions in the starting zone with permafrost, cold to polythermal hanging glaciers and volcanic effects (hot springs) in close contact with each other, (3) the erosion and incorporation of a debris-covered valley glacier largely enhancing the sliding volume of rocks, ice, firn, snow, water and probably air to a total of about 100 × 10⁶ m³, and (4) the astonishingly high flow velocities (up to 300 km h⁻¹) and enormous length of travel path (18 km plus 15 km of debris/mud-flow). This extraordinary case illustrates that large catastrophic events in high mountain regions typically involve a multitude of factors and require integrated consideration of complex chains of processes, a task which must be undertaken by qualified groups of experts.

Glacier- and permafrost-related hazards increasingly threaten human lives, settlements, and infrastructure in high-mountain regions. Present atmospheric warming particularly affects terrestrial systems where surface and sub-surface ice are involved. Changes in glacier and permafrost equilibrium are shifting beyond historical knowledge. Human settlement and activities are extending toward danger zones in the cryospheric system. A number of recent glacier hazards and disasters underscore these trends. Difficult site access and the need for fast data acquisition make satellite remote sensing of crucial importance in high-mountain hazard management and disaster mapping.

Debris flows triggered by glacier lake outbursts have repeatedly caused disasters in various high-mountain regions of the world. Accelerated change of glacial and periglacial environments due to atmospheric warming and increased anthropogenic development in most of these areas raise the need for an adequate hazard assessment and corresponding modelling. The purpose of this paper is to pro-vide a modelling approach which takes into account the current evolution of the glacial environment and satisfies a robust first-order assessment of hazards from glacier-lake outbursts. Two topography-based GIS-models simulating debris flows related to outbursts from glacier lakes are presented and applied for two lake outburst events in the southern Swiss Alps. The models are based on information about glacier lakes derived from remote sensing data, and on digital elevation models (DEM). Hydrological flow routing is used to simulate the debris flow resulting from the lake outburst. Thereby, a multiple- and a single-flow-direction approach are applied. Debris-flow propagation is given in probability-related values indicating the hazard potential of a certain location. The debris flow runout distance is calculated on the basis of empirical data on average slope trajectory. The results show that the multiple-flow-direction approach generally yields a more detailed propagation. The single-flow-direction approach, however, is more robust against DEM artifacts and, hence, more suited for process automation. The model is tested with three differently generated DEMs (including aero-photogrammetry- and satellite image-derived). Potential application of the respective DEMs is discussed with a special focus on satellite-derived DEMs for use in remote high-mountain areas.

Knowing the height of the snowfall limit during precipitation events is crucial for better understanding a number of hydro-climatic processes, for instance glacier-climate interactions or runoff from high mountain catchments. However, knowledge on heights of the phase change during precipitation events is limited by the small number of meteorological measurements available at high altitudes, such as the Himalayas. The bright band (BB) of satellite based radar data may be a promising proxy for the snow/rain transition during particular stratiform precipitation events over high mountain regions. The BB is a horizontal layer of stronger radar reflectivity caused by the melting of hydrometeors at the level where solid precipitation turns into rain. Here, we present BB heights detected by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) 2A23 algorithm over a mountainous area. To assess the performance of BB heights, we have compared a 17‑year data set of BB estimations of the TRMM PR with radiosonde observations and meteorological station data from Srinagar, Kashmir Valley, India. During March to November, the BB lies mostly about 200 to 800 m below the freezing level (FL) recorded by radiosondes. The correlation between BB and FL heights extrapolated from a ground-based station is smaller and depends on the timing of the air temperature measurement – an important finding for applying extrapolation techniques in data sparse regions. Further on, we found a strong seasonal and monthly variability of the BB height, e.g. extending in summer months from about 2700 m to almost 6000 m asl. Comparison with near surface rain intensity from the TRMM PR product 2A25 indicates that – during intense monsoonal summer precipitation events – the BB height is concentrated between about 3500 and 4000 m asl. We can conclude that TRMM PR BB data deliver valuable complementary information for regional or seasonal variability in snow/rain transition in data sparse regio