The lower margins of Glenorchy showing inundation from Lake
Wakatipu on November 19, 1999. Photo by ORC.
The Otago Regional Council (ORC) will meet Glenorchy and
Cardrona Valley residents soon to discuss concerns of
increasing risk of exposure to surrounding natural hazards.
Reports from detailed ORC investigations carried out last
year into the natural hazards in Glenorchy and the Cardrona
Valley said as the populations and resulting demand for
development increased, so too did residents' vulnerability to
"Places that have more things that can be affected can have
higher risk," ORC environmental engineering and natural
hazards director Gavin Palmer said.
Cardrona Valley residents were exposed to hazards including
flooding, sedimentation and erosion.
The Glenorchy township was at risk of inundation from high
lake levels, as in the November 1999 flood, as well as debris
flows and flooding from the Buckler Burn, Bible Stream and
the Rees and Dart rivers, the reports said. For both areas,
mass movement and seismic hazards generated by earthquakes
had the potential to affect residents and infrastructure,
such as access routes, that the wider community depended
Mr Palmer said the hazard studies would be presented soon at
community meetings, although dates were still to be
The Glenorchy and Cardrona Valley studies were part of a
"planned programme of investigations of places where such
information would be valuable", he said.
"The setting of both of these places is such that there are
multiple hazards of varying degrees and there are people
living there now and people going to live there ... it's
about preparing information to help inform decisions by
people about where and how they live ... that's primarily
what the community meetings will be about."
Mr Palmer said the investigations also involved drawing
together information that had been published previously and
providing the public with an overview. For example, in
Glenorchy, the Rees and Dart river deltas were gradually
extending into Lake Wakatipu and research from the University
of Canterbury was giving a better understanding of how the
deltas would continue to change.
The reports noted climate changes could also affect the
frequency and magnitude of flood hazards in the two
"Other PhD work that's been undertaken for the ORC has shown
that we can expect precipitation in the western part of Otago
to increase and we've also been seeing a trend of an
increasing level of Lake Wakatipu."
Providing information on communities' vulnerability to
natural hazards was not just useful for residents and people
who visited or operated businesses there, but also for
territorial authorities which had to make planning decisions
on land use, Mr Palmer said.