Warning over climate change costs for South Dunedin

South Dunedin infrastructure is under pressure, a factor that contributed to flooding in 2015....
South Dunedin infrastructure is under pressure, a factor that contributed to flooding in 2015. PHOTO: ODT FILES
South Dunedin’s climate change-exposed infrastructure has been highlighted in a working paper on the principles and funding options for New Zealand’s managed retreat.

Rates alone will not cover the increasing costs of maintaining or in some cases removing or relocating infrastructure in a managed retreat from the coast, a leading not-for-profit environmental advocacy organisation warns.

The Environmental Defence Society (EDS) yesterday released the first of three working papers as part of its development of recommendations for the Government’s forthcoming Climate Adaptation Bill, due at the end of this year.

The working paper is focused on what the purpose of managed retreat should be, what principles should underpin it and what funding support — if any — should be provided to those affected by it.

The paper is co-authored by EDS policy director Raewyn Peart, Victoria University of Wellington emeritus public policy professor Jonathan Boston, former EDS programme director Dr Sasha Maher and University of Otago coastal geomorphologist Dr Teresa Konlechner.

Climate change would bring higher groundwater, saltwater intrusion, coastal flooding and landslips that could affect infrastructure, the paper said.

Coastal flooding from 1m of sea level rise by 2100 was forecast to affect more than 1441km of roads, 101km of railways, 72km of electricity transmission lines, 141 electricity structures, 14 airports and more than 4000km of Three Water pipelines across New Zealand, it said.

Nationally, costs could reach into the billions if infrastructure was exposed and required some form of intervention, from protection through to relocation, the paper said.

If sea level rise reached 1.5m, $7.8 billion of infrastructure, including 6000km of pipes related to Three Waters, would be at risk.

The extent of infrastructure exposed to climate risk varied by location.

Napier, Lower Hutt and Christchurch were all highly exposed, it said.

"But challenges are also high in niche locations such as South Dunedin and Thames.

"For example, in South Dunedin water infrastructure [along with houses] is coming under significant pressure due to a confluence of factors such as tidal range, land subsidence and climate-induced sea level rise, storms surges and rainfall."

There would be costs related to damage to infrastructure.

There would also be increased operational and maintenance costs.

Planning costs for purchase and rezoning of land for new infrastructure corridors could crop up, as could interim solutions such as flood protection before managed retreat, the paper said.

There could also be "forced abandonment of assets", in some cases, before an asset’s projected, and therefore costed, end of life.

"Such costs need to be seen in light of the current substantial deficit in infrastructure investment.

"The Infrastructure Commission Te Waihanga recently outlined the severity of the deficit problem, which will cost 0.7% of the gross domestic product every year for 30 years."

The Ministry for the Environment published a consultation document on managed retreat in April last year.

The ministry said about 750,000 New Zealanders, and 500,000 buildings worth more than $145 billion, were near rivers or in coastal areas already exposed to extreme flooding.

Several major urban centres and sites of cultural importance were at risk, it said.