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Background
The Thredbo landslide occurred on 30 July 1997. It resulted
in the deaths of eighteen people, making it the worst natural
disaster in Australian history. In the aftermath of the
landslide an intense and complex rescue operation occurred,
resulting in the recovery of one survivor nearly three days
after the slide.
Hydrogeological Setting
The landslide occurred on a steep valley side, natural profile
of colluvial and residual soils, including gravels and gravely
clays and peat deposits, overlying variably weathered granodiorite,
had been modified by the placement of poorly-compacted fill.
Groundwater seepage occurs through all of these units and
is controlled by both lithology and the orientation and
character of defects.
Scope
A forensic investigation into the causes of the landslide
began in parallel with the rescue operation, and continued
for over two years. This investigation focussed on the dynamics
of the landslide, the history of the site, the geotechnical
properties of the natural and fill materials involved, and
the complex hydrogeology of the site. It culminated in an
inquest that ran to 180 sitting days and over 12,000 pages
of transcript. The inquest was conducted in an adversarial
manner, with much of the evidence being subjected to vigorous
legal and technical scrutiny. One of the technical witnesses
gave oral evidence for thirty days, much of that under cross-examination.
The inquest found that the landslide was triggered by water
leaking from a pipe, flowing through and changing the saturation
and cohesion of the soils forming the foundation of the
Alpine Way.
Chris Jewell became involved in the investigation, carried
out on behalf of the NSW police service, four days after
the landslide occurred, and was the penultimate witness
at the inquest.
C. M. Jewell & Associates provided hydrogeological
support throughout the investigation. This work included
groundwater sampling, hydraulic conductivity testing, tracer
testing and modelling of partially saturated groundwater
flow using SEEP-W. 
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Projects