International Symposium on Mitigative Measures against Snow ...

<strong>International</strong> <strong>Symposium</strong> on Mitigative Measures against Snow Avalanches
Egilsstaðir, Iceland, March 11–14, 2008
On a new set of rules for avalanche catching dam design
in Switzerland
Martin Kern*, Marc-André Baillifard, Stefan Margreth and Joseba A. Calvo Soto
WSL Institute for Snow and Avalanche Research SLF, Flüelastr. 11, CH-7260 Davos, SWITZERLAND
*Corresponding author, e-mail: kern (at) slf.ch
ABSTRACT
A new dam design procedure has been developed in Switzerland which takes into account
different energy dissipation mechanisms during the avalanche−dam impact. The new design
procedure represents a more objective approach to dam design as it does not require a
subjective estimate of the energy dissipation implied in the traditional „Salm rule of thumb“.
From scaled laboratory experiments, we empirically found hat the energy dissipation may be
governed by gravitational or momentum driven effects, depending on whether a so-called
granular bore develops or not. The degree to which a granular bore develops decisively determines
the dam height necessary to stop a given avalanche. The necessary dam height then
depends on the avalanche Froude number and on the dam geometry given by the mountainside
dam inclination and on the length and inclination of the dam apron. We demonstrate how
the theoretical description of the avalanche−dam interaction was derived and then empirically
justified in scaled experiments with chute flows of dry cohesionless material and snow. We
present some evidence for the applicability of the theoretical framework on the real-scale
from observations at the full-scale field site in Vallée de la Sionne. Furthermore, we discuss
the validity of the theory in the light of similarity considerations. The theoretical description
has been condensed into a set of rules for practitioners in charge of dam design. We test this
set of rules in a series of case studies reviewing project documentations of several avalanche
catching dams that currently are in the project phase in Switzerland.
Kern, Baillifard, Margreth and Calvo Soto 39