Margreth Keiler

Snow avalanches pose a threat to settlements and infrastructure in alpine environments. Due to the catastrophic events in recent years, the public is more aware of this phenomenon. Alpine settlements have always been confronted with natural hazards, but changes in land use and in dealing with avalanche hazards lead to an altering perception of this threat. In this study, a multi-temporal risk assessment is presented for three avalanche tracks in the municipality of Galtür, Austria. Changes in avalanche risk as well as changes in the risk-influencing factors (process behaviour, values at risk (buildings) and vulnerability) between 1950 and 2000 are quantified. An additional focus is put on the interconnec-tion between these factors and their influence on the resulting risk. The avalanche processes were calculated using different simulation models (SAMOS as well as ELBA+). For each avalanche track, different scenarios were calculated according to the development of mitigation measures...

ABSTRACT Starting with an overview on losses due to mountain hazards in the Russian Federation and the European Alps the question is raised why a substantial number of events still is recorded - despite considerable efforts in hazard mitigation and risk reduction. The main reason for this paradox lies in a missing dynamic risk-based approach, and it is shown that these dynamics have different roots: Firstly, neglecting climate change and systems dynamics, the development of hazard scenarios is based on the static approach of design events. Secondly, due to economic development and population dynamics, the elements at risk exposed are subject to spatial and temporal changes. These issues are discussed with respect to temporal and spatial demands. As a result, it is shown how risk is dynamic on a long-term and short term scale, which has to be acknowledged in the risk concept if this concept is targeted at a sustainable development of mountain regions. A conceptual model is presented that can be used for dynamical risk assessment, and it is shown by different management strategies how this model may be converted into practice. Furthermore, the interconnectedness and interaction between hazard and risk are addressed in order to enhance prevention, the level of protection and the degree of preparedness.

1Institute of Geography, University Bern, Bern, Switzerland 2Department of Geography and Regional Science, University of Graz, Graz, Austria, 3Institute of Remote Sensing and Photogrammetry, Graz University of Technology, Graz, Austria 4Department of Geography ...

Die im Hochwasserschutz notwendige Priorisierung der Massnahmen basiert in der Schweiz auf quantitativen Risikoanalysen, welche die Zustande mit und ohne Massnahmen vergleichen. Die monetaren Werte der potenziell betroffenen Gebaude bilden dabei eine wichtige Eingangsgrosse, sie sind aber oft nicht verfugbar und mussen deshalb geschatzt werden. Der vorliegende Artikel stellt vier volumenbezogene, praxistaugliche Methoden fur die objektgenaue Schatzung von Gebaudewerten vor. Die gleichzeitig prasentierten, aus Daten der Kantonalen Gebaudeversicherungen abgeleiteten Parameterwerte ermoglichen eine robuste Quantifizierung der Wiederherstellungswerte (hochwasser-)exponierter Gebaude in der Schweiz und konnen in regionalen bis nationalen Risikoanalysen verwendet werden.

<p>Understanding the different dimensions of vulnerability to floods is instrumental to gaining knowledge on flood impacts, to guide the development of appropriate risk analysis methods and to make critical decisions in risk management. Vulnerability assessment of complex systems, such as transportation infrastructure, demands an integrated framework to include various analytical methods to investigate the problem from the different characteristic perspectives related to their topological, functional, logic and dynamic properties. One approach to understand the impacts of transportation infrastructure disruptions on people is the accessibility-based vulnerability approach. Accessibility-based vulnerability analysis examines changes of access levels across a traffic network disrupted by floods, thereby providing insight on the impacts to a broader range of socio-economic aspects and to the society as a whole.</p><p>The presented study evaluates two different approaches. The first approach computes direct impacts and investigates different measures for extreme flood impacts to the road network. The second approach computes indirect impacts and</p><p>i) incorporates detailed information about the local road network in the accessibility-based vulnerability analysis by modifying the approach of calculating travel time between zones,</p><p>ii) includes additional contributing factors to the accessibility-based vulnerability analysis by considering residents and socio-economic opportunities in flood-affected areas,</p><p>iii) effectively identifies the most vulnerable traffic zones with respect to selected extreme flood scenarios, and</p><p>iv) investigates the influence of different spatial patterns of floods on accessibility-based vulnerability assessment.</p><p>We used three measures to assess direct flood impacts on the road network towards selecting the flood scenarios, which are representative for different flood patterns. Namely, Loss Index (LI), the total value of normalized edge betweenness centrality (Total-EBC), and the average normalized edge betweenness centrality (Mean-EBC). The Hansen integral accessibility approach was modified for two vulnerability indices considering traffic zones along with average shortest travel time as cost and applied for selected flood scenarios. The resulted vulnerability indices were additionally analyzed to identify the most vulnerable traffic zones for each approach and the spatial influence of the flood and network pattern as well as the distribution of population and opportunities. Finally, effects of the contributing factors to the vulnerability were investigated using correlation and comparison between the flood scenarios.</p><p>The results of the direct impact assessment show that different flood scenario and varying spatial extent are selected as extreme events based on Total-EBC and Mean-EBC. The comparisons of these different measures in assessing direct impact of extreme floods to road network allows to plan different services on disaster mitigation to place mitigation policies to be efficient. Most of the highly vulnerable traffic zones are related to the flood extent in these zones and affected population and opportunities in the traffic zones. However, the most remote traffic zones were also highly vulnerable in flood scenario, if some parts of the important connecting roads for these remote traffic zones were disturbed by a flood in traffic zones faraway. The overall results implicate those different types of flood scenarios could be classified into several groups according to their patterns of vulnerability.</p>

The erosion of and depositions on channel bed surfaces are instrumental to understanding debris flow processes. We present an overview of existing field methods and highlight their respective advantages and disadvantages. Terrestrial laser scanning (TLS), airborne laser scanning (ALS), erosion sensors, cross sections (CS) and geomorphological mapping are compared. Additionally, two of these approaches (i.e. TLS and CS) are tested and applied in the channel reaches of the torrent catchments. The results of the comparison indicate that the methods are associated with variable temporal and spatial resolution as well as data quality and invested effort. TLS data were able to quantify small-scale variations of erosion and deposition volumes. While the same changes could be detected with CS and geomorphological mapping, it was only possible with lower precision and coarser spatial resolution. The study presents a range of potential methods that can be applied accordingly to address the ob...

In natural hazards research, risk is defined as a mathematical function of (1) the probability of occurrence of a hazardous process, and (2) the assessment of the related extent of damage, defined by the value of elements at risk exposed and their physical vulnerability. Until now, various works have been undertaken to determine vulnerability values for objects exposed to hazard processes, in particular with respect to torrent processes and snow avalanches. Yet, many studies only provide rough estimates for vulnerability values based on proxies for process intensities. However, the vulnerability values proposed in the literature show a high range, in particular with respect to medium and high process intensities. In our study, we compare vulnerability functions for torrent processes derived from studies in test sites located in the European Alps and in Taiwan. Based on this comparison we deduce needs for future research in order to enhance mountain hazard risk management with a part...

Zahlreiche Schadensereignisse der letzten Jahre verdeutlichen die grosen Herausforderungen im Schutz vor Naturgefahren im Alpenraum. Bedingt durch den Klimawandel und verstarkt durch soziookonomische Veranderungen steigen Risiken in vielen Regionen an. Der Beitrag diskutiert diese Herausforderungen und zeigt Vorgehensweisen zur Reduktion von Risiken auf.

Communities living in mountain areas are increasingly affected by considerable damage to infrastructure and property as a consequence of flood impacts. The conception of effective flood risk mitigation strategies and their subsequent implementation is therefore essential for a continuing sustainable development in mountain areas. Effective flood risk mitigation strategies can be assessed by their expected utility, which allows the selection of optimal management strategies from a normative point of view. The objective of this paper is to present the underlying procedure, and to derive formal expressions to measure risk mitigation performance starting from the basic theorem of rational choice under risk. Moreover, an overview of existing economic valuation approaches to attach monetary values to the elements at risk is provided.

We present a network study of the Santa Fe Institute Complex Systems Summer School (SFI CSSS) 2009. SFI CSSS 2009 participants consisted of complex systems researchers who were competitively selected to attend the month-long program. The international and interdisciplinary group spent four weeks together attending lectures, engaging in discussions, and collaborating on projects related to complex systems. We found that the CSSS 2009 network became increasingly decentralized and heterogeneous at the end of the program.

The selection of vulnerability models has a significant influence on the overall uncertainty when quantifying flood loss. Several scholars reported a limited spatial transferability of available vulnerability functions to case studies other than those they have been empirically deduced from. As a result, there is a need for computation and validation of regionally specific vulnerability functions. As in many data-scarce regions this option is not feasible, the physical processes of flood impact model chains can be developed using synthetic vulnerability function and validating them by expert opinion. The function presented in our study is based on expert heuristics using a small sample of representative buildings. We applied the vulnerability function in a meso-scale river basin and evaluated the new function by comparing the resulting flood damage with the damage computed by other approaches, (1) an ensemble of vulnerability functions available from the literature, (2) an individua...

The knowledge about potential flood damage is a key issue for disaster risk reduction. However, the scarcity of empirical data has limited flood damage modelling in several regions. As a result, studies in data-scarce regions have mostly been restricted to either building exposure assessment or identification of vulnerability indicators without a further linkage to probable damage. As expert-based approaches do not require empirical damage data, they have a high potential for flood damage modelling in data-scarce regions. In this study, we carried out a comparative assessment between an expert-based and a data-driven approach. The expert-based approach systematically combines the vulnerability indicator method and synthetic what-if analysis based on the knowledge of regional experts. The data-driven approach integrates empirical flood damage data in the analysis applying a multivariate random forest model. Flood damage data, collected through interviews after two flood events in 201...

In natural hazards research, risk is defined as a function of (1) the probability of occurrence of a hazardous process, and (2) the assessment of the related extent of damage, defined by the value of elements at risk exposed and their physical vulnerability. Until now, various works have been undertaken to determine vulnerability values for objects exposed to torrent processes. Yet, many studies only provide rough estimates for vulnerability values based on proxies for process intensities. However, the deduced vulnerability functions proposed in the literature show a high range, in particular with respect to medium and high process intensities. In our study, we compare vulnerability functions for torrent processes derived from studies in test sites located in the Austrian Alps and in Taiwan. Based on this comparison we address challenges for future research in order to enhance mountain hazard risk management with a particular focus on vulnerability on a catchment scale.

Abstract Irrespective of the magnitude and spatial extend, the consequences of a natural hazard are strongly connected to the vulnerability of elements at risk (e.g. people, buildings and infrastructure). It is, therefore, obvious that an analysis and quantification of vulnerability is required for successful disaster risk reduction. The need for vulnerability assessment is crucial due to the effects of climate change as well as the socio-economic dynamics that may directly impact vulnerabilities and coping capacities of affected communities. Vulnerability is multidimensional (physical, social, economic, etc.), however, the dimension which is mainly related to the direct costs and threat to human lives is the physical one. We focus here on the physical vulnerability of buildings subject to torrential hazards occurring in small and steep mountain catchments. These processes include fluvial sediment transport, debris floods, and debris flows. Furthermore, we included flash flood hazards if these are related to torrential catchments. Physical vulnerability to torrential hazards in mountain areas is a topic that has been under scientific investigation over the last 20 years. Several methods to assess physical vulnerability of buildings towards flash floods, debris flows and hyper-concentrated flows can be found in the literature. The plethora of methods and approaches may be classified under the following three categories: vulnerability matrices, vulnerability curves and vulnerability indices. We provide a short review of these methods which became available over the last decade and which dominate the scientific debate in mountain hazard risk management, giving an emphasis to vulnerability curves. The approaches presented herein are highlighted through case studies from the European Alps and beyond. Furthermore, challenges in vulnerability assessment including data requirements, need for improved event documentation, uncertainties and challenges related to future climate and socio-economic changes are outlined. Finally, a discussion on progress-driving factors such as new technologies (e.g. mobile apps, drones), citizen science and new innovative assessment methods is provided.

Flächendeckende Risikoanalysen im regionalen Maßstab erfordern kosten-und zeitsparen-de Methoden für die Erhebung des Naturgefahrenpotentials. Der Schwerpunkt vorliegender Arbeit lag in der Evaluation der Anwendbarkeit bestehender Konzepte zur Gefahrenbeur- ...

<p>We develop a technique for reconstructing floods in small-scale data scarce regions using field interview data and hydro-dynamic modelling. The field interview data consist of flood depths and duration data collected from 300 buildings from a flood event in 2017 in Suleja/Tafa area, Nigeria. The flood event resulted from an overflow of water from five river reaches. The hydrodynamic model utilized, called CAESER LisFLOOD, is an integration of a landscape evolution model (CAESER) and a hydraulic model (LisFLOOD-FP). We employ three steps to reconstruct the 2017 Suleja/Tafa flood event. Firstly, we use a linearly increasing hydrograph to; (a) calibrate Manning’s coefficient and (b) determine optimal peak discharge on each reach. This was carried out by minimizing the Root Mean Square Error (RMSE) between the distributed observed flood depths and the simulated flood depths. Secondly, we use synthetic hydrographs with durations between 6, 12, 18, 20, 24 hours, having peak discharge (extracted from the previous step), to simulate flows on all upstream reaches. Using collected flood duration data, we minimized RMSE between distributed observed flood duration and simulated flood duration to determine optimal flow durations on each upstream reach. In the last step, utilizing peak discharge and flow duration for all upstream reaches, we carried out multiple spatial and temporal iterations to match downstream peak discharge. Thereafter, we use determined upstream hydrographs with their relative catchment response timing to simulate the entire river network. Minimum RMSE computed for the entire river network was between ±15 cm of many current studies that use distributed observed data to calibrate flood models. The method developed in this study is useful for simulating floods in regions where data such as high resolution DEMs, river bathymetry and river discharge are limited. In addition, the study extends current knowledge, on utilizing distributed flood data to determine peak discharge, from a single to multiple river networks.</p>

Beside the flood hazard analysis, a comprehensive flood risk assessment requires the analysis of the exposure of values at risk and their vulnerability. Currently, the main focus of such analysis is on losses on building structure. However, loss on household contents accounts for up to 30% of the total losses on buildings due to floods. Based on insurance claim records, we developed and (cross-)validated two functions. The models based on linear regressions estimate the monetary loss and the degree of loss of household contents by the monetary and degree of loss for building structure, respectively. The main focus herein is to develop functions which provide robustness in prediction and transferability to other regions. Both models generate appropriate results with a comparative advantage of the relative over the absolute loss model. Our results indicate that the ratio of household content to building structure loss is decreasing relatively in regions with comparatively high losses ...