A major earthquake strikes off the coast of Hawke's Bay - Napier locals have 30 to 50 minutes to evacuate their city and avoid a tsunami.
And up to 20,000 of them could head for Napier Hill - the closest elevated ground to Napier's Marine Parade.
How they would evacuate, and the resulting pressure points have been the subject of a two-year research project funded by Natural Hazards Research Platform was led by GNS Science, Massey University, East Coast Lab, the University of Canterbury, with the support of local communities, Councils and Civil Defence Management Groups.
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The resulting information is being collated and will be used to assist in planning that will save lives.
Dr William Power, a tsunami modeller at GNS Science, spoke at a public meeting in Napier this week.
He said the main waves of a tsunami generated by an earthquake on the Hikurangi subduction zone typically expected to reach the coast of Napier in 30-50 minutes.
"Smaller waves may arrive before the main waves so it's important to leave beach and river mouth areas.
"If it is a long or strong earthquake you do need to get to higher ground as soon as possible."
Power said the research had identified that 20,000 or more people could head for Napier Hill during an evacuation.
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"One of the key things for Civil Defence to think about is where about are people going to arrive when they come to Napier Hill. We need to think about how we are going to look after them, and which parts they are going to come to."
The research has also identified:
Maraenui, Te Awa and Marewa:
Maraenui residents have some of the largest distances to cover and the longest times to reach safety.
The shortest route to safety is towards the southwest end of Napier Hill.
The tracks up the Hill are likely to get congested especially outside of working hours.
The shortest route to safety is towards Napier Hill.
The tracks up the hill are congested especially during working hours.
The shortest route to safety is towards Napier Hill but this involves crossing the Pandora Bridge, which may not be safe after the earthquake.
The distance from the north end of Westshore to Napier Hill is quite long, some evacuees may still be on the Pandora Bridge when the main tsunami waves arrive.
The tracks up Napier Hill could become very congested. Napier Hill will have an influx of evacuees. It is very important that people keep moving once they have crossed into the safe zone to make space for new people arriving.
Riverbend Rd resident Denise Bradley said she was interested in learning more about what to do in the aftermath of an earthquake.
"I'm getting older now and I've got to think about where I'm going to go because I won't be moving as quickly as others.
"I live with my daughter and we've sort of always had a plan. We perhaps have been a bit complacent. We will try a trial run."
Power said the research model assumed most people would evacuate by foot within a few minutes of feeling the quake, at the pace of the slowest person in their group.
"In reality, some would bike, drive or not evacuate at all."
People would seek what they thought to be the fastest, safest routes but there would be debris and damage.
"We know, for instance, there were parts of Napier Hill/Bluff hill that had landslides after the 1931 earthquake. There may be car traffic and abandoned cars - people (who) have started driving and given up ...."
Power said the models were not telling people what they should do.
"The advice should come from Civil Defence. We hope that our models would help Civil Defence to give good advice but they have to think through a lot of these other factors.
"We are trying to identify bottlenecks and parts of town that are going to take relatively longer. We get some idea of the number of people that can be expected to arrive in different locations. For instance, a lot of people heading to Napier Hill. Civil Defence and others need to plan for that. "
Hawke's Bay Civil Defence Emergency Management Group Manager Ian Macdonald said the research would help further develop evacuation procedures in the future.
"This research helps to inform how we might work with our local councils to improve potential evacuation routes in the future. This could be things like widening or rerouting pathways that may be used to evacuate areas, and taking the opportunity to improve potential routes when other scheduled works are carried out," Macdonald said.
"We can also use this information to help develop directional signage and more targeted public education, and to help inform long-term land-use planning for local councils."
Recommendations from the research include:
Make a plan with whanau and friends - what route you will take and where you will meet.
Practice your tsunami evacuation hikoi.
Record your tsunami hikoi data - validate our models.
Share what you know with others - help prompt their thinking.
Improve evacuation routes and the efficiency of movement.
Identify safe location meeting points.
Long-Term: Local Government
Improved, more targeted public education including directional signage.
Land use planning - where development is limited or controlled to reduce the type of activities situated within buildings in hazard zones.
Explore vertical evacuations structures.
Power said Japan had tall towers or buildings with easy access to provide refuge.
"These come in various different shapes and sizes. A lot of advice from overseas is that if you have one of these, it is best that it has more than one purpose so people keep using it. In Indonesia, some of these have badminton courts. Other possibilities could be a sports grandstand, with the upper levels for refuge. It could be built on top of a public building. It needs to be built to a high standard so that if a tsunami came it is structurally sound. "