Grim climate-change outlook

Much of already flood-prone Dargaville, on the tidal Northern Wairoa River, is predicted to be up to 1.50m under water by the end of this century. Photo / File

The outlook for Whangarei's central business area and much of Dargaville is grim according to predictions about rising sea levels.

Residents and businesses of those two towns might need to head for the hills, going by the maps in a report released yesterday by Parliamentary Commissioner for the Environment, Jan Wright.

Other low-lying places exposed in the report, called Preparing New Zealand for Rising Seas: Certainty and Uncertainty, are at Bream Bay, Tutukaka Coast, Bay of Islands, Doubtless Bay, Whangaroa Harbour and the west coast north of Hokianga Harbour.

They could be between 50 to 150cm under water by 2100, but most - estuaries, river mouths, salt marshes and drained swamp land, mainly - are already known for their tendency to flood.

Dr Wright's report calls for strong planning to mitigate the likely effects of a rising sea.

"There are aspects of planning that should be done with some urgency," she said.

Granting consents for greenfields development on vulnerable and low-lying land is "foolish", she said.

She wants improved monitoring systems so better models of shoreline erosion can be developed.

Seawalls, drainage, tidal buffers and canals are cited as traditional protection methods which can be improved.

Dr Wright's report contains little new information and has more warnings than solutions, but puts climate change and its impact on New Zealand's vulnerable coast in sharp focus, say scientists and politicians.

"Rather than panic about what is in this report, we should use the science we have and set about looking for sound solutions," Northland MP Winston Peters said.

"For those who want to deny climate change, well, the effects are already there now."

Mr Peters said he agreed with Dr Wright that the onus for future planning was on central government, not on less resourced local governments.

Northland Regional Council (NRC) chairman Bill Shepherd said some issues raised in the report were already part of the council's core business.

"We're in the process of working through the potential impact of sea level rises but we're in the very early stages," Mr Shepherd said.

Whangarei Mayor Sheryl Mai said her council will look closely at the report to see if its own planning needed to be altered.

"Obviously when we hear that our CBD is under threat we take it very seriously.

"We have already been through hazard mapping for the district through the work the NRC is doing. We recognise that we have some vulnerable areas and are already putting measures in place [to] give better future protection," Ms Mai said.

She said mitigation work could be expensive and paying for it may need to be in partnership with central government.

Whangarei based climate-change expert Mick Kelly said the report is a timely wake-up call.

He said that within a decade events such as coastal storms will have a much bigger effect than at present and will be exacerbated by inland erosion, weather patterns and other climate change factors.

Local and central governments needed to start acting, and future-proofing might include people in some areas making "a managed retreat from the coast," Dr Kelly said.

As for the outlook in what is predicted to be Northland's worst affected single community, Dargaville Chief Fire Officer Jeff Palmer said the prospect of more flooding there was a worry.

The fire brigade was the first callout for flooding issues in the town, usually caused by three factors happening together - low barometric pressure, southerly winds and a spring tide.

"That's more or less regardless of the sea level, so if they are predicting sea levels to rise like that it will put even more pressure on things," Mr Palmer said.