Water Stewardship Information Sources

Citation Hungr, O and Evans, SG. 2004. Entrainment of debris in rock avalanches: An analysis of a long run-out mechanism. GSA Bulletin 116
Organization UBC
URL ftp://www.eos.ubc.ca/pub/ohungr/Support/OH_Recent_Papers/Hungr%20and%20Evans%20GSA.pdf
Abstract/Description or Keywords Many rock avalanches entrain and liquefy
saturated soil from their paths. Evidence for
this includes mud displaced from the margins
of rock avalanche deposits, substrate
material smeared along the base of deposits,
extrusion of liquefied soil upward through
the deposits, and increases of volume. A
hypothesis first suggested in 1881 and since
reinforced by several authors suggests that
entrainment of substrate material increases
mobility. Although the process has been
discussed in the literature for more than
100 years, few detailed and quantitative
descriptions exist. The main purpose of this
paper is to describe two recent cases from
British Columbia, Canada, where rockslides
entrained substrate on a very large scale,
influencing the character of the events.
Estimated volume balance curves, based
on detailed field mapping, are provided for
both cases. Dynamic analyses are carried
out using a numerical model and using the
same set of rheological parameters. The
mechanism of material entrainment and
displacement is discussed. The data suggest
that rapid rock failures entraining very large
quantities of saturated substrate material
represent a special type of landslide, transitional
between rock avalanche and debris
avalanche. Many rock avalanches can thus
be seen as end members of a continuum of
phenomena involving rock failure followed
by interaction with saturated substrate.
Keywords: rock avalanche, debris avalanche,
dynamic analysis, runout, entrainment, British
Information Type Article
Regional Watershed Vancouver Island North
Sub-watershed if known Nomash River
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Project status complete
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