Motueka faces special sea level rise challenges

November 20th, 2015
[by David Armstrong]

Motueka is one of nine coastal towns and cities in New Zealand which will be greatly affected by forecast sea level rises through the 21st century.

This is spelled out in a major, well researched report released yesterday by the Parliamentary Commissioner for the Environment Jan Wright, and which has since figured in national news headlines.

The report singled out parts of the country's four major cities plus Napier, Whakatane, Tauranga, Motueka, and Nelson as being the most at risk.

These are places that have more than a thousand homes lying less than 150 centimetres above the present spring high tide mark.

The report said in Motueka there are:

45 homes and four kilometres of roads that are less than 50cm above that tide mark
another 390 homes, 3 businesses and 7km of road sitting less than 100cm (1 metre) above the mark
618 homes and 8km of road sitting between 100cm and 150cm above the present spring high tide mark.

That makes a total of about a third of Motueka homes (1053) lying less than 150 centimetres above the spring high tide mark, but the report added that the long sandbar currently protects the town from big waves during storms.

The map showing the areas of Motueka subject to these risks, published with the report, is shown below.

The report is at pains to make clear that there are no easy answers and no need to panic.

"It is certain that the sea is rising and will continue to do so for centuries to come," it says in its overview. "But much is uncertain - how rapidly it will rise, how different coastal areas will be affected, and how we should prepare.

"And we do need to prepare. After all, as an article in the New York Times put it this year: 'Human civilization is built on the premise that the level of the sea is stable, as indeed it has been for several thousand years'.

"The rising sea will lead to flooding on low-lying land near the coast, erosion of many beaches and 'soft' cliffs, and higher and possibly saltier coastal groundwater.

"Flooding of coastal areas will become more frequent, more severe, and more extensive. Erosion - a long-familiar problem around some of our coasts - will become more widespread. Groundwater linked to the sea will rise and possibly become brackish.

"However, care must be taken with generalisations. Local features matter a great deal."

TDC urges discussions at a national level

In a press release, Tasman Mayor Richard Kempthorne says the report has raised what has been until now a predominantly local issue to one of national importance.

"For several years now every New Zealand council with a coastline has been debating and discussing what a future response to the possible impacts of sea level rise could be," he says. "There is no doubt there is a need for a nationally consistent solution to ensure everyone is treated fairly.

"The Commissioner's recommendation to establish a working group sooner rather than later is wise. Waiting until the choices are limited and the need is imminent will inevitably place a greater level of burden on one group over another, whereas with Government support there is a greater chance of a consensus-driven strategy being developed.

"With the open and relatively soft structure of the coastlines in Tasman, this is and will continue to be an issue for us. With the risks facing people's homes and community infrastructure it is natural we want to protect those investments; but how, at what cost, who pays? These are questions we need to discuss.

"Some people will say that if it is going to happen, sea level rise will be a long time in the future. However, we are making decisions and developing land today that will endure for a long time.

"While the Council can, and has done, some planning locally I agree with the Parliamentary Commissioner for the Environment in that the Government needs to be involved in a wider conversation.

"The Government itself has taxpayer interests in roads, schools, national parks, in areas exposed to the potential impacts of sea level rise and cannot stand aside.

"My colleagues and I within Tasman are seeking a national conversation about this issue and it should take place within months, not years. It is not going to be solved overnight, but the sooner we sit down to identify the possible solutions the sooner we can come to an acceptable community response."

The full report by Jan Wright can be found here.

Comment by Phillip Grimmett:
[Posted 21 November 2015]

It's great to read coverage of this very important matter, locally and globally. Clearly, leadership, or lack of it, is the Key issue. All talk and very little significant action.

Comment by Jim Butler:
[Posted 21 November 2015]

Report on National Radio. The present annual increase is only likely to become a serious problem for Motueka in the next 30 to 40 years. Early indications will likely be more short term surface flooding in low lying areas of the town during heavy rain storms because of rise in the level of the aquifer beneath the town, because surface flood water will have less ability to drain away quickly because of the slowly increasing height of high tides. The consequence of more insurance claims will result in increased premiums.

My opinion. For increase protection, there is a need to encourage the spread of ice plants along stopbanks because the thick mat these plants provide strengthens the stopbanks, coupled with suitable tree planting along the stopbanks. This is particularly necessary around the Motueka sewage plant to ensure its 30 year life, as millions of dollars of ratepayers is now being spent on upgrading this plant.

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