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
3. SNOW AVALANCHE SEDIMENT TRANSPORT AND HAZARD ASSESSMENT
Sediment included within the snow mass flowing down represent of course an increased
danger when an avalanche hits people and human properties. Apart from these direct dangers,
sediment transported by snow avalanches provide long-lasting evidence of snow avalanche
occurrence, providing crucial information on their frequency, magnitude, especially in terms
of runout distance. Due to the recurrence of snow avalanche events of various kinds in the
same area, from dry-snow avalanches to slush flows in some cases, the accumulation of
sediment transported by the snow flowing down build typical landforms, from tiny (perched
boulders) to major (large snow avalanches dominated colluvial cones). Sediment sequences of
stratigraphical profiles within snow avalanche prone areas, especially on talus cones, reveal
valuable information that attest the past recurrence of snow avalanches. In this way, the work
from Blikra and Sæmundsson (1998) in Flateyri (Fig. 7), Sæmundsson (2002a, 2002b, 2005)
in Bolungarvík and Siglufjörður present great interest in snow avalanche research related to
risk assessment, demonstrating the snow avalanche occurrence of past snow avalanches in the
direct surrounding of populated areas, potentially at risk. Linking sedimentological
information from back country sites to inhabited areas also present a significant interest in
snow avalanche hazard assessment (Decaulne and others, this volume).
Figure 6 Sedimentary sequences and interpretation of deposits on the Skollahvilft cone
above the village of Flateyri. Snow avalanche activity was very common during
the last centuries (modified from Blikra and Sæmundsson, 1998).
Sæmundsson, Decaulne and Jónsson 141