Impact of climate change being assessed

Horizons Regional Council has been assessing the impact climate change could have on coastal communities in Manawatu/Whanganui.

Once completed the work will feed in to advice Horizons provides on dealing with coastal hazards.

In light of the release this week on the second part of the fifth United Nations Intergovernmental Panel on Climate Change assessment report, the Manawatu Standard asked Horizons how it was preparing for climate change.

The report predicted a 0.5-metre increase in sea levels by 2100, and warned of an increased risk of wildfire, storms, floods and landslides.

Horizons has been assessing several coastal communities for the impacts of both current coastal hazards and future increases in these hazards due to climate change.

Detailed assessments have been completed on Akitio, Herbertville, Foxton Beach and the Waikawa Beach to Waitarere coastline. Work is now being done on parts of the Koitiata to Wainui coastline.

"These assessments focus on both coastal inundation due to storms, assessing the magnitude of storm surges and storm surge wave runup, and coastal erosion," Peter Blackwood of Horizons said.

The assessments looked at the current risk and forecast risks in 50 years and 100 years' time, according to the latest guidelines from the Ministry for the Environment.

"Horizons Regional Council for several decades has been providing advice on the various coastal hazards and supporting planning mechanisms so that houses and other infrastructure are not located in these vulnerable areas or are constructed to mitigate the risk - for example by setting minimum floor levels and ensuring that safe egress is available both now and in the future."

Paying for erosion protection work was not generally a function of Horizons, Blackwood said, but of district councils. "However, Horizons has provided recent design advice on erosion mitigation structures at Waikawa Beach and Akitio", and it has also assessed the impact of climate change on flood events.

"The current assessment considers a forecast 2.1 degree rise in temperature to the year 2090. This essentially results in a 16.8 per cent increase in rainfall intensity and close to 20 per cent increase in peak flood flows by 2090.

"In constructing scheme upgrades Horizon has been mindful of how these increases could be accommodated."

The Manawatu City Reach project, which protects Palmerston North from flooding, was an example of future-proofing for climate change.

"Some flood mitigation measures, such as stopbanks, may be relatively easy to raise, subject to community affordability. However, others . . . are not simply raised and Horizons has built some of their floodwalls higher than the current design requirements - in anticipation."

Manawatu Standard