With the dozens and dozens of coastal communities along the
3200km plus coastline that makes up the Northland Region it is important is be
aware of the tsunami zones in preparation for a tsunami event. The Northland Tsunami
Evacuation Zones have been prepared by the Institute of Geological and Nuclear
Sciences Limited (GNS Science) for Northland Regional Council and can be
divided into two categories (zones): Orange and Yellow. The Green Zone is symbolization of the land
area not highlighted by the Orange and Yellow zones.The Red Zone: This zone represents the area that is has been
identified as the highest risk and should be considered off-limits during and
after a tsunami event. This zone usually covers the shoreline, a marine and
beach areas which also include rivers, estuaries and harbours. This zone should
be evacuated for any tsunami warning that has a minimum warning threshold
(currently set) between 20cm amplitude up to 1m amplitude. For purposes of
mapping, NRC utilise Mean High Water Springs (as supplied by LINZ) as the Red
Zone.The Orange Evacuation Zone:
This zone represents a middle zone, created to avoid over-evacuation and
the associated issues that this can create when there are official warnings that
can extend pass the Red Zone – meaning that the tsunami is more than an hour
away in travel time therefore there is time for an official warning and are
expected to have a maximum amplitude of 3-5metres. In the case of larger
tsunami, evacuation may escalate to clearing the Yellow Zone.
The
Yellow Evacuation Zone: This zone represents the area that should be evacuated for
precautionary reasons in the case of highest predicted magnitude tsunami. These events are often indicated by
natural/informal warning signs (long, strong earthquakes) or where there is a
maximum amplitude that equated to the 2500-year return period wave amplitude at
the 84% level of confidence. This zone
should cover all maximum creditable tsunami events including the highest impact
events.
The Green Evacuation Zone: This zone represents a safe area
that should not be physically impacted by a tsunami. People evacuating the Red,
Orange and Yellow Zones should retreat to this area.
