Thomas Glade

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 Zealands 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.

Challenges of analyzing multi-hazard risk: a review

Many areas of the world are prone to several natural hazards, and effective risk reduction is only possible if all relevant threats are considered and analyzed. However, in contrast to single-hazard analyses, the examination of multiple hazards poses a range of additional challenges due to the differing characteristics of processes. This refers to the assessment of the hazard level, as well as to the vulnerability toward distinct processes, and to the arising risk level. As comparability of the single-hazard results is strongly needed, an equivalent approach has to be chosen that allows to estimate the overall hazard and consequent risk level as well as to rank threats. In addition, the visualization of a range of natural hazards or risks is a challenging task since the high quantity of information has to be depicted in a way that allows for easy and clear interpretation. The aim of this contribution is to give an outline of the challenges each step of a multi-hazard (risk) analysis poses and to present current studies and approaches that face these difficulties.

Vulnerability assessment in natural hazard and risk analysis: current approaches and future challenges

Negative consequences of natural hazards are the result of both the frequency and intensity of the hazard and the vulnerability of the society or element at risk exposed. Therefore, vulnerability assessment is an essential step to reduce these consequences and consequently natural hazard risk. The assessment of vulnerability requires an ability to both identify and understand the susceptibility of elements at risk and—in a broader sense—of the society to these hazards. The concept of vulnerability is used today by various disciplines, and hence, it is embedded in multiple disciplinary theories underpinning either a technical or a social origin of the concept and resulting in a range of paradigms for either a qualitative or quantitative assessment of vulnerability. However, efforts to reduce the exposure to hazards and to create disaster-resilient communities require intersections among these theories (e.g. Hufschmidt and Glade 2010), since human activity cannot be seen independently from the environmental settings and vice versa. Acknowledging different roots of disciplinary paradigms, methods determining structural, economic, institutional or social vulnerability should be inter-woven in order to enhance our understanding of vulnerability and to adopt to ongoing global change processes. Current approaches in vulnerability research are driven by a divide between social scientists and natural scientists, even if recently some attempts have been made within to

Improvement of vulnerability curves using data from extreme events: debris flow event in South Tyrol

Alpine hazards such as debris flow, floods, snow avalanches, rock falls, and landslides pose a significant threat to local communities. The assessment of the vulnerability of the built environment to these hazards in the context of risk analysis is a topic that is growing in importance due to global environmental change impacts as well as socio-economic changes. Hence, the vulnerability is essential for the development of efficient risk reduction strategies. In this contribution, a methodology for the development of a vulnerability curve as a function of the intensity of the process and the degree of loss is presented. After some modifications, this methodology can also be used for other types of hazards in the future. The curve can be a valuable tool in the hands of local authorities, emergency and disaster planners since it can assist decision making and cost–benefit analysis of structural protection measures by assessing the potential cost of future events. The developed methodology is applied in two villages (Gand and Ennewasser) located in Martell valley, South Tyrol, Italy. In the case study area, buildings and infrastructure suffered significant damages following a debris flow event in August 1987. The event caused extensive damage and was very well documented. The documented data were used to create a vulnerability curve that shows the degree of loss corresponding to different process intensities. The resulting curve can be later used in order to assess the potential economic loss of future events. Although the validation process demonstrated the reliability of the results, a new damage assessment documentation is being recommended and presented. This documentation might improve the quality of the data and the reliability of the curve. The presented research has been developed in the European FP7 project MOVE (Methods for the Improvement of Vulnerability Assessment in Europe).

The use of historical data in natural hazard assessments

List of Contributors. Preface. An introduction to the use of historical data in natural hazard assessments T. Glade, et al. Part A: Earthquakes P. Albini. Searching for the source of the 1117 earthquake in northern Italy: A multidisciplinary approach F. Galadini, et al. Sismicite historique des petites Antilles. Un test pour quelques annees du milieu du XIXe siecle J. Vogt. The 1828-1829 earthquake sequence in the provinces of Alicante and Murcia (S-E Spain): Historical sources and macroseismic intensity assessment P. Albini, F.R. De La Torre. The seismic history of Nicolosi (Catania, Italy) M.S. Barbano, et al. A new macroseismic catalogue for Catalonia T. Susagna, et al. Expeditious seismic damage scenarios based on intensity data from historical earthquakes M. Mucciarelli, M. Stucchi. Part B: Flooding F. Frances. Incorporating non-systematic information to flood frequency analysis using the maximum likelihood estimation method F. Frances. Historical flood data analysis using AGIS: The Palaeotagus database M.F. De Villalta, et al. Collaboration between historians and hydrologists on the Ardeche river (France) R. Naulet, et al. Availability and potential of historical flood series in the Iberian Peninsula (14th - 20th centuries) M.-C. Llasat, M. Barriendos. Hydraulic modelling and historical inundation assessment for the Versilia river S. Pagliara. Part C: Landslide T. Glade. Landslide hazard assessment and historical landslide data - an inseparable couple? T. Glade. Widespread landslide and flood events in the Catanzaros Isthmus (Calabria, Italy) Relationships with rainfall data V. Rizzo, et al. The development and application of a historicalbibliography to assess landslide hazard in the United States C. Alger, E.E. Brabb. The contribution of historical information in the assessment of landslide hazard D. Calcaterra, M. Parise. Index.

Landslide Hazard Assessment and Historical Landslide Data — An Inseparable Couple?

By definition, landslide hazard assessments must define the probability of landslide occurrence for a given region, area and/or time. If spatial information such as landslide distribution after a single landslide event is used for hazard analysis, the resulting hazard assessment is based purely on spatial components. Another approach for establishing the probability of occurrence involves time. As soon as temporal information is included, the need for historical data is obvious. Probabilities may then be calculated by using data on recent and past landslide failures, by means of recurrence intervals of the triggering agent or by a combination of both. These approaches lead, however, to temporal landslide hazard assessment. The ultimate step towards a comprehensive landslide hazard assessment is to combine both spatial and temporal probabilities. This increases the demand on reliable historical landslide data.

Loss estimation for landslides in mountain areas - An integrated toolbox for vulnerability assessment and damage documentation

Global environmental change includes changes in a wide range of global scale phenomena, which are expected to affect a number of physical processes, as well as the vulnerability of the communities that will experience their impact. Decision-makers are in need of tools that will enable them to assess the loss of such processes under different future scenarios and to design risk reduction strategies. In this paper, a tool is presented that can be used by a range of end-users (e.g. local authorities, decision makers, etc.) for the assessment of the monetary loss from future landslide events, with a particular focus on torrential processes. The toolbox includes three functions: a) enhancement of the post-event damage data collection process, b) assessment of monetary loss of future events and c) continuous updating and improvement of an existing vulnerability curve by adding data of recent events. All functions of the tool are demonstrated through examples of its application. We developed a tool that will support decision making for disaster risk reduction strategies in mountain areas.The tool incorporates three functions: damage documentation, loss estimation and updating of the vulnerability curve.The tool was applied and tested in South Tyrol, Italy.Future developments (more elements at risks and hazards, uncertainty analysis, mobile applications) have been pointed out.

A review of multi-risk methodologies for natural hazards: Consequences and challenges for a climate change impact assessment.

This paper presents a review of existing multi-risk assessment concepts and tools applied by organisations and projects providing the basis for the development of a multi-risk methodology in a climate change perspective. Relevant initiatives were developed for the assessment of multiple natural hazards (e.g. floods, storm surges, droughts) affecting the same area in a defined timeframe (e.g. year, season, decade). Major research efforts were focused on the identification and aggregation of multiple hazard types (e.g. independent, correlated, cascading hazards) by means of quantitative and semi-quantitative approaches. Moreover, several methodologies aim to assess the vulnerability of multiple targets to specific natural hazards by means of vulnerability functions and indicators at the regional and local scale. The overall results of the review show that multi-risk approaches do not consider the effects of climate change and mostly rely on the analysis of static vulnerability (i.e. no time-dependent vulnerabilities, no changes among exposed elements). A relevant challenge is therefore to develop comprehensive formal approaches for the assessment of different climate-induced hazards and risks, including dynamic exposure and vulnerability. This requires the selection and aggregation of suitable hazard and vulnerability metrics to make a synthesis of information about multiple climate impacts, the spatial analysis and ranking of risks, including their visualization and communication to end-users. To face these issues, climate impact assessors should develop cross-sectorial collaborations among different expertise (e.g. modellers, natural scientists, economists) integrating information on climate change scenarios with sectorial climate impact assessment, towards the development of a comprehensive multi-risk assessment process.

Natural hazards and resilience: exploring institutional and organizational dimensions of social resilience

Policy discourses and academic debates provide evidence that resilience has become one of the leading ideas to deal with uncertainty and change in our times. This applies for numerous and diverse discourses such as flood risk management (Steinfuehrer et al. 2009), urban development policy (Linovski 2010; Mueller 2011), responding to terrorism (Coaffee et al. 2009), and mega-projects like the Olympic Games (Jennings and Lodge 2010), just to name a few. Resilience also appears in a diverse range of publications from institutional (Anderies et al. 2004), organizational (Weick 2009), and climate change adaptation research (Pelling 2011). While the need to build resilience is highlighted, the definitions of resilience are manifold and partially blurred. Given this diversity and accessing the more focused usage of the term ‘‘resilience’’ in ecological research, some authors worry about the health of resilience research (Klein et al. 2003; Brand and Jax 2007). Others see the growth and diversity of discourses and publications as a sign of ‘‘good’’ health (e.g., Van de Ven and Hargrave 2004, p. 291). Despite the wide range of diverse discourses and publications, this Special Issue of natural hazards aims to contribute to these debates with a specific perspective on the overall topic of resilience that might be best described with the term ‘‘social resilience.’’

Integration of a limit-equilibrium model into a landslide early warning system

Landslides are a significant hazard in many parts of the world and exhibit a high, and often underestimated, damage potential. Deploying landslide early warning systems is one risk management strategy that, amongst others, can be used to protect local communities. In geotechnical applications, slope stability models play an important role in predicting slope behaviour as a result of external influences; however, they are only rarely incorporated into landslide early warning systems. In this study, the physically based slope stability model CHASM (Combined Hydrology and Stability Model) was initially applied to a reactivated landslide in the Swabian Alb to assess stability conditions and was subsequently integrated into a prototype of a semi-automated landslide early warning system. The results of the CHASM application demonstrate that for several potential shear surfaces the Factor of Safety is relatively low, and subsequent rainfall events could cause instability. To integrate and automate CHASM within an early warning system, international geospatial standards were employed to ensure the interoperability of system components and the transferability of the implemented system as a whole. The CHASM algorithm is automatically run as a web processing service, utilising fixed, predetermined input data, and variable input data including hydrological monitoring data and quantitative rainfall forecasts. Once pre-defined modelling or monitoring thresholds are exceeded, a web notification service distributes SMS and email messages to relevant experts, who then determine whether to issue an early warning to local and regional stakeholders, as well as providing appropriate action advice. This study successfully demonstrated the potential of this new approach to landslide early warning. To move from demonstration to active issuance of early warnings demands the future acquisition of high-quality data on mechanical properties and distributed pore water pressure regimes.