12th Congress INTERPRAEVENT 2012 Grenoble / France – Extended Abstracts www.interpraevent.at
A NEW VULNERABILITY FUNCTION FOR DEBRIS FLOW
THE IMPORTANCE OF PHYSICAL VULNERABILITY IN ALPINE AREASMaria Papathoma-Köhle1, Margreth Keiler2, Reinhold Totschnig 3 and Thomas Glade4
INTRODUCTION
Alpine hazards such as debris flow, floods, snow avalanches, rock falls and landslides pose a significant threat to local communities. These natural processes can cause damage to lifelines, critical infrastructure, agricultural lands, housing, public and private infrastructure, but also loss of life. The assessment of the vulnerability of the built environment to these hazards is a topic that is growing in importance due to climate change impacts. In most studies concerning physical vulnerability assessment, vulnerability is perceived as “The degree of loss to a given element, or set of elements, within the area affected by a hazard. It is expressed on a scale of 0 (no loss) to 1 (total loss)”
(UNDRO, 1984). However, for the authors of the present study vulnerability is considered connected to a pre-existing condition that is related to those characteristics and properties of the elements at risk that increase their susceptibility to the impact of hazards. In a wider sense, ‘‘vulnerability is a characteristic of human behaviour, social and physical environments, describing the degree of susceptibility (or resistance) to the impact of e.g. natural hazards’’ (CENAT, 2004). It is a fact that a better understanding of vulnerability will lead to more effective risk assessment, emergency management and to the development of mitigation and preparedness activities that may reduce the loss of life and economic costs following a disastrous event. Therefore, a detailed investigation on the relation of the degree of loss and the intensity of the processes as well as on the identification of factors influencing this relation is presented. In this study the importance of physical vulnerability assessment is demonstrated through a case study in South Tyrol, Italy. The results of the case study are integrated in a general framework of vulnerability assessment and will be discussed critically.
VULNERABILITY ASSESSMENT METHODS FOR ALPINE HAZARDS
The majority of the studies concerning mountain hazards focus on hazard assessment, modelling, monitoring and risk management. Vulnerability assessment of alpine hazards is a relative new field of research and the number of studies focusing on vulnerability assessment for these types of hazards is limited. In a review of existing physical vulnerability assessment methods for alpine hazards Papathoma-Köhle et al. (2011) identify the gaps and difficulties of existing vulnerability assessment methodologies and point out the future needs for vulnerability assessment to alpine hazards, which can serve as a tool for effective emergency and disaster management. In more detail, Papathoma-Köhle et al. (2011) suggest that there is lack of common language between scientists, many difficulties in the implementation of the existing methodologies (e.g. data availability, time consumption), differences between them regarding their scale, the consideration of the hazardous phenomenon and its properties, the consideration of important vulnerability indicators and the use of technology such as GIS and remote sensing. In the present abstract the methodological steps to the creation of a vulnerability curve for debris flow are presented.
1 Dr. Maria Papathoma-Köhle. University of Vienna, Institute for Geography and Regional Research, Universitätsstrasse 7, 1010 Vienna, Austria (e-mail: maria.papathoma@univie.ac.at)
2 Dr. Margreth Keiler. University of Bern, Institute for Geography, Switzerland
3 DI Reinhold Totschnig, MSc. University of Natural Resources and Life Sciences, Institute of Mountain Risk Engineering, Austria
4 Prof. Thomas Glade. University of Vienna, Institute for Geography and Regional Research, Austria
- 290 -
CASE STUDY: SOUTH TYROL, ITALY
South Tyrol has been often affected by different types of alpine hazards such as debris flow, avalanches and landslides that led to damages of the infrastructure and the built environment. Photos from buildings following a catastrophic event were collected together with maps and air photographs indicating the location of these buildings as well as further relevant GIS data. Information regarding the building characteristics and its surroundings, the damage on the buildings and the thickness of the debris deposits could be acquired from the photos. Moreover, prices regarding restoration costs of buildings and building values were taken from a study regarding the costs of flood disasters in South Tyrol (Kaswalder, 2009). Based on this information a vulnerability curve was created as a function of the intensity of the process (in this case thickness of debris flow in meters) and the degree of loss (expressed as percentage of the object value). In other words, a curve was created showing the degree of loss that corresponds to different intensities of the process. This curve can be improved by adding more data from other events and it can be used to assess the degree of loss of future events.
CONCLUSION AND FUTURE DEVELOPMENTS
We present herein the methodological steps for the creation of a vulnerability curve as a function of the intensity of the process and the degree of loss that can be a valuable tool in the hands of local authorities, emergency and disaster planners and other stakeholders. The vulnerability curve can provide useful information to improve risk analysis. By knowing what could possibly happen in the future and how much would it cost, the stakeholders can organise not only preparedness and mitigation measures but also the response phase following the disastrous event. Moreover, the vulnerability curve can provide information to support a cost-benefit analysis regarding costly mitigation measures. However, there is always room for further development. More curves can be developed for different types of houses and the existing curve could be improved by entering more data that can be acquired from future events. For this reason a standardised method of documentation would improve significantly the information quality. Last but not least by looking at the response of buildings and other elements at risk to a hazardous event we could identify the factors that contribute to their vulnerability (vulnerability indicators) and assess their importance.
REFERENCES
CENAT (2004). Monte Verita Workshop 2004, Coping with Risks due to Natural Hazards in the 21st Century, 28 November 2004–03 December 2004, Online GLOSSARY.
Kaswalder C. (2009). Schätzungsstudie: Zur Berechnung des Schadenspotentials bei Hochwasserereignissen durch die Rienz im Abschnitt Bruneck-St. Lorenzen. Autonome Provinz Bozen – Südtirol. Abteilung 30 – Wasserschutzbauten.
Papathoma Köhle M., Kappes M., Keiler M., Glade T. (2011). Physical vulnerability assessment for alpine hazards: state of the art and future needs. Natural Hazards 58:645-680.
UNDRO (1984). Disaster prevention and mitigation—a compendium of current knowledge, vol 11.
Preparedness Aspects, New York.
Keywords: vulnerability, alpine disasters, vulnerability curve, degree of loss
- 291 -
