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| Titel |
The 6 August 2010 Mount Meager rock slide-debris flow, Coast Mountains, British Columbia: characteristics, dynamics, and implications for hazard and risk assessment |
| VerfasserIn |
R. H. Guthrie, P. Friele, K. Allstadt, N. Roberts, S. G. Evans, K. B. Delaney, D. Roche, J. J. Clague, M. Jakob |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 12, no. 5 ; Nr. 12, no. 5 (2012-05-04), S.1277-1294 |
| Datensatznummer |
250010797
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| Publikation (Nr.) |
 copernicus.org/nhess-12-1277-2012.pdf |
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| Zusammenfassung |
| A large rock avalanche occurred at 03:27:30 PDT, 6 August 2010, in the Mount
Meager Volcanic Complex southwest British Columbia. The landslide initiated
as a rock slide in Pleistocene rhyodacitic volcanic rock with the collapse of
the secondary peak of Mount Meager. The detached rock mass impacted the
volcano's weathered and saturated flanks, creating a visible seismic
signature on nearby seismographs. Undrained loading of the sloping flank
caused the immediate and extremely rapid evacuation of the entire flank with
a strong horizontal force, as the rock slide transformed into a debris flow.
The disintegrating mass travelled down Capricorn Creek at an average velocity
of 64 m s−1, exhibiting dramatic super-elevation in bends to the
intersection of Meager Creek, 7.8 km from the source. At Meager Creek the
debris impacted the south side of Meager valley, causing a runup of 270 m
above the valley floor and the deflection of the landslide debris both
upstream (for 3.7 km) and downstream into the Lillooet River valley (for
4.9 km), where it blocked the Lillooet River river for a couple of hours,
approximately 10 km from the landslide source. Deposition at the
Capricorn–Meager confluence also dammed Meager Creek for about 19 h
creating a lake 1.5 km long. The overtopping of the dam and the predicted
outburst flood was the basis for a night time evacuation of 1500 residents in
the town of Pemberton, 65 km downstream. High-resolution GeoEye satellite
imagery obtained on 16 October 2010 was used to create a post-event digital
elevation model. Comparing pre- and post-event topography we estimate
the volume of the initial displaced mass from the flank of Mount Meager to be
48.5 × 106 m3, the height of the path (H) to be 2183 m
and the total length of the path (L) to be 12.7 km. This yields H/L = 0.172 and a fahrböschung (travel angle) of 9.75°. The
movement was recorded on seismographs in British Columbia and Washington
State with the initial impact, the debris flow travelling through bends in
Capricorn Creek, and the impact with Meager Creek are all evident on a number
of seismograms. The landslide had a seismic trace equivalent to a M = 2.6
earthquake. Velocities and dynamics of the movement were simulated using
DAN-W. The 2010 event is the third major landslide in the Capricorn Creek
watershed since 1998 and the fifth large-scale mass flow in the Meager Creek
watershed since 1930. No lives were lost in the event, but despite its
relatively remote location direct costs of the 2010 landslide are estimated
to be in the order of $10 M CAD. |
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