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INTRODUCTION
Flood risk management is a forward looking meth- od to understand, mitigate or avoid the adverse consequences of flooding. Risk analyses provide a basis for this management and usually address three general questions (e.g. Merz & Thieken 2004): (1) How do possible flood scenarios look like? (2) How likely is their occurrence? (3) What are the consequences in case a scenario occurs?
A probabilistic flood risk evaluation model which is able to answer the three questions was developed (Schneeberger et al. in press). The risk evaluation model consists of three parts, (i) a Hazard Module (ii) an Impact Module, and (iii) a Risk Assessment Module. In the first module the potential flood hazard will be investigated. Therefore, a large set of possible flood events is generated for further analysis. The strength of this approach is to gener- ate more realistic heterogeneous flood events instead of analysing homogeneous events with a constant return period throughout an entire river basin (Schneeberger & Steinberger submitted).
In the Impact Module the potential adverse conse- quences of flooding are characterised by flood impact indicators like potential affected buildings and potential building losses (Huttenlau et al.,
2015). In the Risk Assessment Module flood risk is statistically evaluated (e.g. exceedance probability curves, expected annual flood impact) based on the results of the Hazard Module (set of heterogeneous flood events) and the Impact Module (e.g. loss- probability-relation). A main challenge within the introduced framework remains the selection of suitable damage functions, as they can influence the results considerably (e.g. Huttenlau et al. in press). The present contribution focuses on the Impact Module and further describes the far-reach- ing consequences in the Risk Assessment Module.
METHOD
The study focuses on the analysis of building losses which are used as flood impact indicator. For the assessment of these direct monetary damages the following procedure is applied: (i) Asset pooling and asset assessment. (ii) Exposure analysis where- as inundation maps are spatially combined with the relevant assets to identify the exposures of the elements at risk (e.g. Huttenlau et al., 2015). (iii) Susceptibility analysis whereby an ensemble of damage models (based on literature) are applied.
Loss-probability-relations for defined spatial units (e.g. communities) are, thereby, derived. These
IP_2016_EA241 Figure 1. (a) Flood risk analysis model structure and (b) loss-probability-relations of two exemplary communities including different damage functions
(for b) see also Huttenlau et al., 2015).
Damage functions as crucial factor in a modular flood risk evaluation framework
Matthias Huttenlau, Dr.1; Klaus Schneeberger, Dr.2; Benjamin Winter, Dipl.-Geogr.2; Johann Stötter, Prof. Dr.2
HAZARD AND RISK ASSESSMENT (ANALYSIS, EVALUATION)
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KEYWORDS
flood risk management; risk analysis; damage functions; sensitivity; case study Vorarlberg
1 alpS - Centre for Climate Change Adaptation, Innsbruck, AUSTRIA, huttenlau@alps-gmbh.com
2 alpS - Centre for Climate Change Adaptation, Innsbruck, AUSTRIA; Institute of Geography, University of Innsbruck, AUSTRIA
relations are combined with individual scenarios of the Hazard Module and further statistically evaluat- ed in the Risk Assessment Module.
RESULTS AND DISCUSSION
The results demonstrate (Figure (b)) that the selection of the damage functions is crucial in the context of flood risk analysis. The monetary dam- age within a community can vary by a factor of two or more depending on the considered susceptibility approach. The wide spectrum shows the sensitivity and uncertainty of susceptibility approaches in general. The comparison of documented events and (re)modelled results can further assist to evaluate the most suitable damage models for a specific study area, which can substantially reduce the uncertainties. These findings resulting from a regional flood risk study conducted in the Austrian Federal Province of Vorarlberg. The detailed results of this study will be presented with the conference contribution.
Even if heterogeneous flood events are considered with complex and sophisticated approaches the extensive influence of damage models has to be considered. This has also to be taken into account while comparing and interpreting results of differ- ent studies. The development of site-specific dam- age functions is normally not possible due to the lack of data, and thus the application of an ensem- ble of published susceptibility approaches (damage functions) seems to be adequate in a first step.
In a second step the different applied approach have to be evaluated (if possible) and the best-fit approach(es) for the specific study conditions has to be chosen.
REFERENCES:
- Huttenlau M., Schneeberger K., Winter B., Reiss J., Stötter J. (2015). Analysis of the loss probability relation on a community level: a contribution to a comprehensive flood risk assessment. In: Sener, S.M., Brebbia, C., Ozcevik, O. (Eds.), Disaster Management and Human Health Risk IV, Istanbul, Turkey, 20-22 May 2015, WIT Transactions on The Built Environment, 150, 171-182. doi:10.2495/
DMAN150161
- Merz B., Thieken A. (2004). Flood Risk Analysis:
Concepts and Challenges. Österreichische Wasser- und Abfallwirtschaft 56, 27-34.
- Schneeberger K., Huttenlau M., Stötter J. (2015) Probabilistisches Modell zur Analyse des räumlich differenzierten Hochwasserrisikos. Hydrol. Wasser- bewirtsch. 59, 271-277. doi: 10.5675/
HyWa_2015,5_8.
- Schneeberger K., Steinberger T. (submitted).
Generation of synthetic flood events in an Alpine region - Adaptation and application of a multi- variate modelling procedure. Journal of Hydrology.
