New Napier mapping shows growing coastal flood risk

The new flood modelling risk for Napier based on current sea levels (left), a sea-level rise of 0.5m (centre), and a sea-level rise of 1m (right). Photo / Niwa

New modelling has shown that large areas of Napier are at a growing risk of severe coastal flooding because of climate change and sea levels rising.

Niwa released new mapping today showing areas across New Zealand which will be affected by a one-in-100-year coastal flood.

Sea levels are projected to rise 0.4m by 2065 and 1m by the end of the century, according to Niwa.

As such, the mapping provides a range of flood scenarios based on sea-level rises between zero and 2m.

“We have created maps that help identify the changing risk to land, property, and infrastructure from rising seas, at a regional and national scale,” said Dr Scott Stephens, Niwa’s chief scientist for coasts and estuaries.

“We hope this information will raise awareness and help councils and government to know where to conduct detailed investigations when developing adaptation strategies to protect our coastal communities.”

Napier is particularly vulnerable to coastal flooding as it has large areas built on low-lying land close to the coast.

A view over Napier. Photo / Paul Taylor

If sea levels were to stay as they are, Onekawa and parts of Pirimai and Meeanee would be under water in a one-in-100-year coastal flood, according to the latest modelling.

If sea levels were to rise by just 0.2m, Clive, Parklands, Haumoana and even Hawke’s Bay Airport would also be flooded.

At 0.5m, Te Awa, Tamatea and Marewa would be flooded and, at 1m, even Greenmeadows would be underwater. At 2m, most of the city would be flooded.

The new modelling is based upon a 1 per cent annual exceedance probability (AEP).

That means a 1 per cent chance of severe flooding in any given year, or an average likelihood of once in the next 100 years.

Flooding of that magnitude would likely be caused by a combination of a big storm, high tides and large waves, according to Niwa.

Stephens said the mapping would help shape decisions on how to adapt to sea-level rises.

“It’s difficult to make decisions about the future if you can’t see it - these maps provide a window into the future,” he said.

“With much of our major infrastructure and roughly 65 per cent of New Zealanders living within 5km of the coast, this is an issue that will impact many of us, so we must be aware of what’s coming and be prepared to adapt.”