20 Nov 2015

Sea levels 'not a matter of speculation'

2:13 pm on 20 November 2015

There is no room for speculation about rising sea levels when you're standing up to your knees in water in your back yard, says Dunedin Mayor Dave Cull.

Emergency services pumping water out from flooded shops.

South Dunedin was hit by severe surface flooding in July Photo: RNZ / Ian Telfer

A report released yesterday by Parliamentary Commissioner for the Environment Jan Wright made it clear the problem of rising sea levels was just beginning, calling it a slowly unfolding red zone.

Dr Wright found 2800 homes and businesses in South Dunedin would be among the first at risk from sea level rises of half a metre.

Despite the threat revealed by the report, Finance Minster Bill English said the government was not intending to put money aside for any future demand from a rising sea level.

He said it had more pressing issues, and he thought people in South Dunedin would be reluctant to up sticks and move on the basis of what he described as "speculation about the sea level rise".

Flooding in Dunedin's Surrey Street in early June.

Flooding in Dunedin's Surrey Street. Photo: RNZ / Ian Telfer

Speaking to Nine to Noon this morning, Mr Cull hit back at Mr English's claim.

"He's just wrong. It's not speculative, it's based on evidence. When you're standing up to your knees in water, it's not a matter of speculation."

He said central government could not sit around and wait for something to happen, it needed to start planning now, model what might happen and prepare for it.

"It doesn't seem very bright to me. We should be learning from previous experience when it hasn't worked."

The major problem in South Dunedin is the rising groundwater, with the pressure from the sea pushing the groundwater up so that the water level was approaching ground level or above.

Dunedin Mayor Dave Cull

Dunedin Mayor Dave Cull Photo: RNZ / Ian Telfer

Mr Cull said the ongoing impact of that was becoming more obvious.

"After the June floods - where we copped a lot of criticism, people were saying our stormwater pipes were blocked and our pumps weren't working - we've done a lot of modelling since then and that modelling vindicates the commissioner's report in that the ground had absolutely no capacity to absorb any of the rain at all, so it all sat on the surface, and that is the effect.

"We've got a problem all the time because the groundwater is high and as it gets higher it will create more problems, but it's exacerbated in rain events because the rainwater has got nowhere to go."

He said the problem did not just need central government funding, but an appreciation that no one agency could tackle it on its own.

"Local government certainly don't have the resources and more importantly, it doesn't have the tools or powers. If there is a problem on an individual property of some kind we can deal with those things, but if there is an issue across a whole suburb, frankly I don't think we have the tools to deal with it.

"We may need legislative facilitation to get those tools, as well as government support and guidance in using them."

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An image from Dr Wright's report showing low-lying areas of Dunedin. Photo: Preparing New Zealand for Rising Seas report

Insurance Council of New Zealand head Tim Grafton backed up Mr Cull's call for a multi-party solution, telling RNZ the new report showed the risks that were being faced.

"What we need to have is a broad consultation. We need seats around the table from local and central government, banks, insurers and businesses, right down to the community level, because all parties bring something to a solution here."

'Once-a-century' flooding every year

NIWA contributed two studies to the report on the implications of rising sea levels.

Rob Bell - co-ordinator for hazards and risks at NIWA, and the author of its report on risk exposure in low-lying coastal areas - said the next few decades would be crucial, and some areas would find once-in-a-century flooding becoming an annual event.

"The ones that are probably already in the firing line have probably experienced some flooding over the last decade or two. Those are the ones that a very modest sea level rise of 30cm - or in some places even 20cm - will find this kind of flooding is an annual affair."

Extreme flooding events, such as the January 2011 Auckland flooding that saw Tamaki Drive and the Northwestern Motorway shut down, could be the new benchmark, he said.

"That's the type of event that would have occurred once every 100 years, so with a 35-40cm sea level rise, that becomes an annual affair. But then the more rarer events in the future will be even deeper and of a wider extent than that."

He said the issue would affect more than just the homes of local residents.

"All these issues are not just in terms of people's homes, it's the infrastructure that services that local community."

"We need to start now in terms of planning and having those conversations with communities, with infrastructure operators, and looking at infrastructure planning, and all those other aspects."

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