Volcanoes - Ministry of Civil Defence and Emergency Management

Fig 3. Lake Tarawera area evacuation route. Spencer Road west to
Tarawera Road to Rotorua.
Fig 5. Kawerau Evacuation Routes. Two possible evacuation routes:
NE via SH30; or south via the main road or the forestry road.
Lake Tarawera and is a long narrow road that extends
for ~17 km, from Tarawera Road to Rotorua, making
large-scale evacuation on this road hazardous. There is
also the likelihood of landslips occurring on the road,
associated with pre-eruption seismicity, severing the link
to Rotorua. The construction of a loop road extending
northwest from Spencer Road to Millar Road, Lake
Okareka, should be considered. This would be of benefit
to the local residents at any time, but particularly so
if an eruption is imminent. The use of a loop road as
a mitigation measure was implemented by officials at
Mammoth Mountain (Long Valley, California, USA)
during an eruption scare (Mader & Blair, 1987).
The next level of risk will be inside a zone of
40 kms radius from the erupting volcano (Fig.2). This
is the Secondary Evacuation Zone and would include
the urban areas of Rotorua, Kawerau and Murupara.
Effects on these towns will depend very much on the
wind direction, but such variability puts all in potential
danger. The larger population means that any decision
to evacuate becomes a major operation and requires
careful planning.
Fig 4. Rotorua Evacuation Routes. Rotorua has two options: south by
SH 30 or SH 5 to Taupo; or west by SH 5 to Hamilton.
URBAN AREAS
Rotorua is situated 25 km west-northwest of
Tarawera volcano (Fig 4). The population of Rotorua
district is 64,473 (Census 2001), and a compulsory
evacuation notice may be given if the eruption is large
enough or wind direction is from the east. Because of
the larger population however, it would be advisable
that voluntary evacuation is encouraged earlier, to
decrease the number of potential evacuees where the
compulsory order is given. The importance of the timing
of any evacuation order is critical: too soon, and people
will start to return, believing the emergency is over; too
late, and many evacuees will try to evacuate at once,
causing panic.
Kawerau is situated 20 km northeast of Tarawera
volcano (Fig 5), with a population of 6,975 (Census
2001). Kawerau has three main road exits from its
township. It must be remembered that Rotorua and
Te Teko could also have been ordered to evacuate at
this time. This puts pressure on some roads and other
evacuation routes.
Population statistics of the potential evacuation
areas are presented in Table 3. The percentage of
residents who actually evacuate is hard to estimate.
A figure of 50-70% of the population, is presented by
Auckland Regional Council (1996) as the “anticipated
maximum credible [evacuee] number” in the event
of an eruption from the Auckland volcanic field. This
percentage is supported by Dow and Cutter (2002)
who found there was an evacuation rate of 65% during
Hurricane Floyd in the USA. Therefore, in Table 3, an
estimated 60% of the affected Bay of Plenty region
population is taken as a potential figure for numbers of
evacuees.
Plans for evacuation movement, ie. major
evacuation routes and destinations, must be in place
48
TEPHRA
June 2004