Study: 14,000 coastal properties at risk

AT RISK: Dargaville is also at risk of climate change-related flooding and erosion.PHOTO/FILE

About 14,000 coastal Northland properties have been identified as at risk from climate change-related flooding and erosion, compared to 1090 at the last review 10 years ago.

Following public consultation, the information would go on property files and may have insurance implications for owners and planning implications for local authorities.

The data comes from Northland Regional Council's coastal flood and coastal erosion zone maps, expected to be released in June, which identify around 14,000 properties that could experience severe flooding once a year by 2100.

The flood and erosion modelling took into account a sea level rise of 1m by the end of the century, in line with the Inter-Governmental Panel on Climate Change's most recent predictions.

Even a sea level rise of 30cm by 2100, considered to be the best case scenario, would see today's once-in-100-year storm event happening every year or so. The NRC maps would show which areas would be inundated during such an event.

NRC natural hazards adviser Toby Kay said the floods modelled assumed no mitigation action was taken - an unlikely scenario.

"The overall intent is to avoid increasing the risk from coastal hazards, and ensure any future designs are future-proofed," Mr Kay said. "The main thrust is to try and guide future development and avoid increasing our exposure."

Mr Kay tentatively named Dargaville, Whangarei CBD, Awanui, Ruakaka and Waipu Cove as among the low-lying areas with affected properties.

He stressed the maps about to be released were in draft form and that the public could make submissions until September 1. For example, he said, they would be altered in cases where people had significantly modified their land.

Over time, the flood zones would likely be incorporated into district plans, a process which could take years. However, once the maps were finalised, the information would be available for the public, including engineers and developers, on request.

NRC's piece of work took into account three of the four coastal hazards exacerbated by climate change: flooding, erosion and a rising water table. The fourth was the risk posed by larger-than-ever tsunami.

In November, 2015 Dr Jan Wright, Parliamentary Commissioner for the Environment, released a report on how New Zealand could prepare for the risk posed by rising seas. In it, Dr Wright described the granting of consents to build on vulnerable land as "foolish".