Review of the Tsunami Evacuation 2017

conflicting, scientists are working with changing data and the threat is complex and difficult to
understand. In these instances, MCDEM operates on the best information we have available. If the
threat turns out to be lower than initially estimated, there may have been unnecessary
precautionary evacuations in some areas. This is the acceptable trade-off given the alternative,
which is to underestimate a threat.
During this event tsunami waves severely damaged a property in Little Pigeon Bay, Canterbury
(see images in reference list). No-one was present in the house at the time. Given the degree of
damage to the building, the depth and velocity of the water, and the movement of very large
furniture inside the house, it is possible that if people were present, there would have been
casualties and potentially fatalities. It is essential that a precautionary approach be taken when
lives are at risk.
New NWS Templates
11 Recommendations Clear understanding of the
Tsunami Expert Panel and MCDEM
decision-making process
MCDEM’s message to evacuate was based on best scientific advice at the time. The advice to
evacuate had been posted on the MCDEM website at 0100 to coincide with Tsunami Threat #1.
The NWS message issued at 0125 stated that evacuation was necessary and included locations
which cover Canterbury and Christchurch:
No: 02
Issued 0125 hours 14 November 2016
The Ministry of Civil Defence & Emergency Management (MCDEM) has issued a tsunami
warning for Eastern coast of North and South Island including the Chatham Islands. It may arrive
in the Eastern Coast of the North Island shortly. Move inland or to higher ground immediately.
MCDEM requests the “Review of the tsunami evacuation” draft report be corrected to show that
evacuation based on a tsunami threat was advised for Canterbury via the NWS at 0125.
MCDEM has updated NWS messages to include the Long or Strong, Get Gone message. MCDEM
acknowledges that official warnings may not be timely for local source events and should not be
expected before the first waves arrive. Inclusion of this message is to reinforce, via media and
CDEM Groups distribution of NWS messages, that those whom have already evacuated have done
the right thing and those that have not should move immediately. This is consistent with all
current guidelines and technical standards on local source tsunami events.
This is outlined step-by-step in the National Tsunami Advisory and Warning Plan [SP 01/09].
Recommend removal of the first paragraph under “Recommendations”. To reiterate, GNS Science
establishes a Tsunami Experts Panel to provide advice to MCDEM, they do not work with MCDEM
on decision-making. MCDEM makes decisions regarding warnings.
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