Economic assessment of landslide risks in the Swabian Alb, Germany – research framework and first results of homeowners’ and experts’ surveys

Landslide risks are frequently underestimated by political and economic actors as well as by the local population. The InterRisk Assess research project is working to develop a systematic approach to the analysis and evaluation of economic landslide risks at a local and regional scale. Its major aims are to determine the extent of potential damage and economic losses caused by landslides, to analyze individual and collective patterns of risk assessment and to develop recommendations for pro-active risk management. The research methodology includes GIS-based risk analyses and interviews with relevant actors in politics, administration and planning, private households and land owners. The research findings will facilitate a better-informed, efficient and sustainable use of natural resources and natural risks. The research project also aims to contribute to methodological progress in risk research. 1 Landslides: An underestimated natural risk Landslides are gravitational mass movements of earth or rock. In the last few decades landslides have caused considerable damage (Münchener Rückversicherung, 2000/2004). Abbott (1996) estimated that US$ 1.5 billion costs are caused by landslides in the United States annually. One example illustrating the consequences of landslides is the destruction of the Alaskan Way Viaduct (near Seattle; landslide caused by the Nisqually Earthquake in 2001). The repairs cost some 500 million US$, replacement would have cost US$ 1 billion (Highland, 2003). In Japan, annual losses due to landslides total about US$ 2 billion. In European countries, annual losses can be even higher, for example US$ 2.6 billion per annum in Italy (Schuster, 1996). Landslides may occur as an isolated phenomenon or in conjunction with volcanic eruptions, earthquakes or floods. Landslides are among the most significant natural hazards Correspondence to: A. Blöchl ([email protected]) worldwide. They are integral to numerous geosystems, particularly in alpine regions, but also in many low mountain ranges (Dikau and Glade, 2002). In German low mountain ranges, landslides occur less frequently and with less dramatic consequences than in the Alps. This results in frequent underestimation of the landslide risk in these regions, although landslides cause damage to buildings (in residential areas in most cases), roads, agricultural and forest areas. Smaller landslides occur frequently in Rheinhessen, in the region around Bonn and in the Swabian Alb, for example. Other reasons for the underestimation of risks are the belief that modern technology obviates catastrophic consequences for the population, while a lack of knowledge of landslide processes prevents people from seeing any danger in these movements. Thus it is important to analyze landslide risk and its perception and evaluation by the population and key actors in these regions. In order to reduce private and public losses it is necessary to develop methods to evaluate landslide risks in a socioeconomic context. This requires an integrative approach applying different scientific and methodological perspectives. 2 Objectives of InterRisk Assess InterRisk Assess is part of “InterRisk – Integrative landslide risk analysis and risk evaluation in the Swabian Alb (Germany)”. InterRisk is a group of four projects initiated in 2003. By integrating physical, social, historical and economic perspectives InterRisk is working to develop a comprehensive methodological framework to analyze and evaluate landslide risks and to give recommendations to public and private actors. The research framework is applied to landslide risks in the Swabian Alb in the south-western Germany (federal state of Baden-Württemberg). Within the InterRisk project group, “InterRisk Assess” (Economic evaluation of natural risks of landslides on the Swabian Alb from a collective and individual point of view) aims to examine economic aspects of landslide risks. The 390 A. Blöchl and B. Braun: Economic assessment of landslide risks in the Swabian Alb, Germany Fig. 1. Location of the research area. project combines economic risk analysis and evaluation. It determines regional damage potential and investigates collective and individual patterns of risk evaluation. “InterRisk Assess” has four main objectives: 1. To develop methods for the systematic analysis of risks on a regional scale: The estimation of potential damage (analysis of elements at risk as well as direct and indirect economic effects) must be linked with the identification of exposure to risk. The economic risk assessment is firstly an assessment of financial risk. It will be integrated in a model of systematic risk evaluation, which includes other factors such as perception, prevention or coping capacity (see Objective 2). 2. To develop methods for the systematic evaluation of natural risks: In order to give recommendations to individual actors and public decision-makers, a widely accepted, standardized methodology has to be developed. Individual and collective risk perception and prevention as well as thresholds of acceptability must be studied. In addition, the costs of prevention measures or alternatives should be specified. 3. Search for means of preventing hazards on an individual scale. Analysis of preconditions for actors who take decisions or give recommendations: Actors directly affected include private households, farmers, forest owners or firms located in landslide-prone areas. An analysis of the behavioral patterns of and decisions made by individuals affected or potentially affected is important for optimal adaptation to natural risks and their successful prevention. Fig. 2 Research design one regional scale: risk analysis and evaluation information o former damage events and loss o analysis of economic values in endangered areas detailed specification of elements at risk and possible damages Research design two individual/personal scale: risk perception and strategies of prevention selection of persons or groups for detailed interviews evaluation of empirical data recommendations for risk management on regional, local and individual scale Fig. 2. Basic conception of the working program of InterRisk Assess. 4. Recommendations for sustainable risk management at regional, local and individual levels: Landslide risk management is underdeveloped in the Swabian Alb. Therefore it is necessary to develop and apply tools for integrative risk management. Such tools can consist of maps identifying dangers and risks, to be used by planners or administrative authorities. In order to cope with risks one must be familiar with the scale of possible landslide hazards. This task can only be accomplished out in cooperation with the other sub-projects of InterRisk.