Sea-level rise problem for whole city

The view across southern Dunedin towards Otago Harbour. Photo by Stephen Jaquiery.
The view across southern Dunedin towards Otago Harbour. Photo by Stephen Jaquiery.
Sea-level rise will be painful for the whole of Dunedin and the city needs to respond to the threat now, the University of Otago's Centre for Sustainability says.

To help with the response, researchers from the centre have developed a map which collates 140 layers of information about the at-risk part of greater South Dunedin, including house ages, demographic details and modelled water ponding under different scenarios.

It was hoped the data would help agencies, including the Dunedin City Council and Otago Regional Council, understand the impact of sea-level rise or flooding in the vulnerable area on residents, community facilities and infrastructure.

Centre director Dr Janet Stephenson said the university would continue to work with both councils on finding solutions to the threat from climate change and it was hoped the data could be used by researchers across the university.

''We have had amazing co-operation with them in developing this,'' Dr Stephenson said.

The data included physical information, such as different area's heights above sea level, and information on the human population taken from the census, including income levels and age.

''Once you have got those overlays, you can start answering questions about who might be worst impacted.''

She emphasised sea-level rise would be ''painful'' for the whole of Dunedin and not just South Dunedin.

Low-level areas, which also included St Kilda, Forbury and St Clair, contained many facilities all Dunedin residents used.

''This is all of Dunedin's problem, not just South Dunedin's problem.''

It was understandable some people in affected areas wanted to deny there was going to be an issue, but the science was settled and sea-level rise was occurring.

''I think what we can be sure of is sea-level rise will occur. Where the science is uncertain is just about how rapidly that might occur.''

Deputy director Dr Caroline Orchiston said the centre had been keen to pursue the work since late 2015, when parliamentary commissioner for the environment Dr Jan Wright pinpointed South Dunedin as New Zealand's most vulnerable urban area to sea-level rise.

''The spatial database is an important step because it brings together information from many different agencies and holds it all in one place,'' Dr Orchiston said.

Summer scholarship student Leigh McKenzie, who put together the maps, said even without detailed analysis interesting things could be seen.

''For example, the biggest area that is less than one metre above sea level is around St Kilda East, but the areas most subject to ponding are mainly around Forbury and St Kilda West.''

vaughan.elder@odt.co.nz

Comments

The scholarship student who worked on this project for the UoO Centre for Sustainability points out some inconvenient truths. She says "'For example, the biggest area that is less than one metre above sea level is around St Kilda East" - this is true, but contradicts Prof Jim Flynn's recent claims that the lowest parts of South Dunedin are less than 25cm above sea level.

She also observes that the areas most subject to ponding are not the low lying parts of South Dunedin. This was shown as a result of the 2015 flood event where the lowest parts were not badly affected. The parts most severely affected were where the DCC stormwater system was most restricted by the dilapidated, narrow pipes and the failure of the DCC to modernize the 1960's design.

Dr Stephenson is therefore wrong to say that the low-level areas are at risk of rizing sea-level. The reason for this is that for nearly all of South Dunedin, there is no relationship between ground-water level and sea level. We know this because the ground-water level of South Dunedin is about 600mm ABOVE sea level; also the ORC has been recording ground-water levels for several years and there is no sign of rizing ground-water.

The University of Otago Centre for Sustainability (CSAFE) has been doing this sort of thing for a while now. First it was the fearmongering about "peak oil" and how they predicted that the oil was running out and would soon be unaffordable. Reality quickly destroyed that theory which was heavily promoted by Mayor Dave Cull and his ideological comrades. Now the Centre for Sustainability is helping the gloom and doom campaign originized by the DCC and ORC to torment the citizens of South Dunedin and destroy the businesses confidence of the area.

In the same way that we learned the truth about the "peak oil" campaign, the people of South Dunedin will realize that there is no threat to them from rizing sea level. The threat to South Dunedin is not from rizing sea level, it is from those that make false and wildly exaggerated claims about sea-level rize.

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