Bayesian optimal design of an avalanche dam using a multivariate numerical avalanche model |
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| Authors: | N Eckert E Parent T Faug M Naaim |
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| Institution: | 1. UR ETNA, Cemagref Grenoble, BP 76, 38402, Saint Martin d’Hères, France
2. Equipe MORSE, UMR 518 AgroParisTech/INRA, 19 avenue du Maine, 75732, Paris Cedex 15, France
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| Abstract: | For snow avalanches, passive defense structures are generally designed by considering high return period events. However,
defining a return period turns out to be tricky as soon as different variables are simultaneously considered. This problem
can be overcome by maximizing the expected economic benefit of the defense structure, but purely stochastic approaches are
not possible for paths with a complex geometry in the runout zone. Therefore, in this paper, we include a multivariate numerical
avalanche propagation model within a Bayesian decisional framework. The influence of a vertical dam on an avalanche flow is
quantified in terms of local energy dissipation with a simple semi-empirical relation. Costs corresponding to dam construction
and the damage to a building situated in the runout zone are roughly evaluated for each dam height–hazard value pair, with
damage intensity depending on avalanche velocity. Special attention is given to the poor local information to be taken into
account for the decision. Using a case study from the French avalanche database, the Bayesian optimal dam height is shown
to be more pessimistic than the classical optimal height because of the increasing effect of parameter uncertainty. It also
appears that the lack of local information is especially critical for a building exposed to the most extreme events only.
The residual hazard after dam construction is analyzed and the sensitivity to the different modelling assumptions is evaluated.
Finally, possible further developments of the approach are discussed. |
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