Review of the Tsunami Evacuation 2017

5 Background States a tsunami threat and
possible evacuation requirement
was only made clear in the 2.01 am
NWS message received from
MCDEM
7 National Warning
System
8 Local source
tsunami-lead
CDEM Groups are responsible for
disseminating national warnings to
local communities
CDEM Groups analyse information
and decide what to do in their
region.
With regards to warnings from the
Guide to National CDEM Plan
reality as the shaking can be so great that instruments can provide conflicting or confusing
information.
The following message was sent via the National Warning System at 0125 on November 14 th ,
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.”
The Tsunami Advisory and Warning Plan and Guide to the National CDEM Plan make it clear that
MCDEM will provide tsunami warnings describing threats to land, beach marine areas, and not
evacuation advice for the public. This is the responsibility of CDEM Groups. However, given the
scientific advice had changed since the earlier no threat message had been issued, a precautionary
approach was taken due to the risk to life. MCDEM did advise evacuation in this case, as is within
its remit. Up until November 14 th there was no expectation from CDEM Groups that MCDEM
would advise evacuation during any tsunami event.
Note that for regional and distant source tsunami with hours of warning time available, MCDEM
provide messages stating a threat to land and marine or beach and marine with expected wave
heights at the coast. CDEM Groups then assess this based on their local knowledge and evacuation
thresholds and advise the public to evacuate if required. During the November 14 th event the
evacuation message and land threat messages were distributed by MCDEM based on advice that
waves could be significant and widespread.
In such uncertain and potentially life-threatening events with very little response time and a
threat already established, MCDEM expects all CDEM groups to act consistently with national
warnings and not hesitate or take actions inconsistent with national advice.
To promote consistent response, since this event MCDEM has created new warning templates for
large subduction zone earthquakes that advise which areas should evacuate immediately.
This is true for most hazards, but where an event is already occurring and a threat to life has been
identified, MCDEM may include specific instructions to the public its warnings. These messages
are sent to the media as well as CDEM Groups. MCDEM also uses its social media channels in time
critical events.
As stated in the Guide to the National CDEM Plan, warning for local source tsunami is the
responsibility of Groups, this is because it should be strongly focussed on public education for
natural warnings as per various tsunami-related MCDEM guidelines and technical standards.
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