Out of the erosion zone - quake's unexpected boon

9:32 am on 19 April 2017

Coastal uplift from the massive Kaikōura earthquake may have saved the local council from having to spend millions of dollars protecting the town from erosion.

Coastline south of Kaikōura.

Last year's magnitude 7.8 earthquake raised 120km of coastline up out of the ocean by between 1-6 metres. Photo: RNZ / Claire Eastham-Farrelly

Coastal erosion is the wearing away of land by wave action, currents, or high winds - it can impact infrastructure near the sea including roads and buildings.

Last year's 7.8 magnitude quake, raised 120 kilometres of coastline up out of the ocean by one to six metres.

Canterbury's regional council, Environment Canterbury (ECan), is now investigating whether the event could have put previously at-risk infrastructure around Kaikōura out of reach.

Council natural hazards scientist and spokesperson Justin Cope said it was too soon to say if the uplift of the coastline would dispel erosion concerns in the area - but there was no doubt it would find some changes.

"Certainly when you get uplift - which is essentially a drop in sea-level, relative sea level - so we're expecting some changes, it's just we haven't got around to collecting all of the data we need to make those assessments."

Mr Cope said ECan would be gathering data from the area over the next few months, so it could advise Kaikōura District Council on the way forward.

Kaikoura District Mayor Winston Gray

Winston Gray said the issue of coastal erosion "now appeared to have gone away" Photo: RNZ / Claire Eastham-Farrelly

Kaikōura mayor Winston Gray said coastal erosion had been a huge concern for the council before the earthquakes.

The land had been receding all around the coastline surrounding the township, including in commercial and residential areas, he said.

"It was actually the elephant in the room for us, like many councils, because it was such a big job to deal with, particularly along the esplanade where it's a very popular residential area."

The council had expected to spend millions of dollars on managing the coastal erosion issue, he said.

"Now with the uplift ... certainly it has taken the issue away for a given period of time. How long, we don't know."

His council was waiting for the regional council to present its findings before making any further decisions around erosion management, he said.

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