Watch for warning signs says scientist

A tsunami expert just back from Sri Lanka says New Zealanders must learn to watch for signs of a big tsunami.

Dr James Goff, of Lyttelton, who joined a United States mission to Sri Lanka last week, met a fisherman who saved 5000 lives when he noticed the sea "behaving strangely" and warned villagers to run to higher ground.

New Zealanders needed to be alert for similar signs.

"We are far more prone to tsunamis than Sri Lanka. We need to know what to do," said Dr Goff.

Last year he and Government scientist Roy Walters listed geological evidence of 10 major tsunamis that hit New Zealand in the past 6300years.

The latest, around AD 1450, was 32m high at Henderson Bay just south of North Cape - five times the height of the Boxing Day wave in Sri Lanka - and rolled up to 3.5km inland as far afield as Abel Tasman National Park and Palliser Bay, near Wellington.

It is believed to have been triggered by an undersea volcano in the Kermadec arc northeast of East Cape, an active volcanic area that creates a "tsunami crescent" from the Far North to the eastern Bay of Plenty.

Dr Goff wants signs on the beaches warning people, "You are in a tsunami inundation zone," and listing telltale signs that should alert people to escape to high ground.

In Sri Lanka, the fisherman saw "a little wave" come in and go out again just before the big wave.

"Even before that, he saw the water behaving, as he said, strangely. The boats were rattling together. It was a very unusual sensation."

Flamingoes, elephants, bats and other wildlife in the nearby Yala National Park picked up the signals and fled inland minutes before the big wave.

Dr Goff said sand dunes provided natural protection where they existed. But one resort at Yala had cleared the dunes to give tourists a better view. It was flattened and 150 people died.

"Farther along the coast, the dunes were still there. It's as clear as daylight that if the dune had still been there, that resort would still have been there."

Another resort was destroyed in a small bay where the headlands on either side directed the wave into the centre of the bay.

"It was the wrong place to be in an environment like this. If you understood the geology of the coastline, you wouldn't have built it there.

"The lesson is that you can build in bays, but you have to think about the kind of structure you build. You don't want to put a hospital or a school there. And if you do have buildings in areas that are exposed, you should have a good evacuation plan."

A railway that ran along the coast in Sri Lanka was badly damaged and 1500 people died in a train.

"Bring that into New Zealand and look at where we put those things. Look at State Highway 1 and the main trunk line in the South Island." 

Giant waves
32m - North Cape tsunami in 1450
10m - Khao Lak, Thailand, Boxing Day
6m - Southern Sri Lanka, Boxing Day
1.7m - Height of average New Zealander over 15