What was left of the Hall family's Pouawa Beach cottage following the 1947 "stealth tsunami". Photo / Alexander Turnbull Library
What was left of the Hall family's Pouawa Beach cottage following the 1947 "stealth tsunami". Photo / Alexander Turnbull Library
Monster 12-metre waves, an entire settlement swept out to sea, and a bridge lifted and dumped a kilometre upriver are a few examples of the might of tsunami that have struck New Zealand in the last two centuries.
Toka Tū Ake EQC and GNS Science have combed hundreds of years worth of historical tsunami data to create a new public resource, detailing all recorded tsunamis since 1835.
The hope is the resource, a modern database, will increase awareness of New Zealand's tsunami risk and help inform better land-use planning.
The database gathers information from monitoring equipment, newspaper articles, maritime records, personal diary entries, and Māori oral records to tell the story of New Zealand's tsunami history.
While the country has not experienced any tsunamis in the timeframe that would be categorised as "devastating" or worse, there were several incidents described as "very destructive".
Among these were the two "stealth tsunamis" in Gisborne in 1947, so named because the earthquakes that generated them were not widely felt.
According to the database, the Hall family of Pouawa Beach were at home with visitors when their cottage was "overwhelmed" by the first wave.
"The water reached the eaves and the room the three people were in was turned completely round. The other four rooms and three sheds were demolished," the database said.
Most of the house was swept out to sea but miraculously nobody was killed in the terrifying event.
The same tsunami, described by some witnesses to be about 40ft [12m] high, swept the Pouawa Bridge 800m upstream.
Another of New Zealand's biggest tsunamis happened at the Chatham Islands in 1868, washing a 60-70-person settlement out to sea.
Sparked by an earthquake in Peru, the waves destroyed a whole Māori pā and the homes of two or three Pākeha settlers.
"Sand and kelp were the only remains of the pah [sic], drays were smashed, and a 7-8 cwt [50kg] grindstone erected at the pah was hurled a 'considerable distance'," said the historical recording of the incident.
The inhabitants were described as being left "destitute".
"All they possessed was carried away as water receded, the loss of everything being aided by an offshore wind."
There was also a huge wave in 1855 at Palliser Bay, Wairarapa, which, destroyed a shed perched 8m above sea level.
"The earthquake waves were about 30 feet high [9m], and showed a white crest although the night was cloudy; they succeeded the shocks," an anonymous recollection stated.
"One family would certainly have been drowned had not some sailor, who had been on the South American coast, recognised the character of the approaching wave the moment it became visible."
Another recollection noted the tsunami had swept numerous bales of wool out to sea.
"Strange to say the return wave brought the wool ashore again, and none was lost."
The fascinating database will be a "key tool for decision-making" and would help steer New Zealand's science and hazard risk management sector, Toka Tū Ake risk reduction and resilience manager Sarah-Jayne McCurrach said.
The database shows 939 records of tsunami, 866 of which are categorised as "definite".
It is hosted by GNS and will allow open access for the scientific community as well as the public.
The database is available to the public. Image / Supplied
The announcement of the database coincides with the 75th anniversary of the second of two big historic earthquakes that happened near Gisborne in 1947.
The information can help scientists understand other locations in New Zealand where this type of event could occur and provoke research leading to further investment in New Zealand's tsunami monitoring and detection network.
"Significant research into these types of events has allowed us to better understand and model what could happen and where," McCurrach said.
"While we might not have experienced significant or damaging tsunami events like other countries have in recent years, this database shows we have experienced very large tsunamis in the past.
That's why it is important to know as much as we can about what we could face in New Zealand."
