How should Tasman District adapt to rising sea levels and coastal hazards?

The Tasman District Council wants to hear residents’ views on options for adapting to sea level rise and coastal hazards.

A risk assessment released in late 2020 revealed that an estimated 8400 people in the district live in low-lying coastal areas vulnerable to storm inundation and sea level rise.

More than 5000 buildings, mostly in the Motueka-Riwaka area, about 350 archaeological sites, eight closed landfills, 3650 hectares of grassland, 2106ha of coastal indigenous vegetation (much of it in Abel Tasman National Park) and 941ha of urban land were identified as being at risk.

Those risks arise from coastal storm inundation that has a 1 per cent chance of occurring in any year, and up to two metres of sea level rise.

A range of infrastructure is also vulnerable, including the Bell Island wastewater treatment plant, the Motueka wastewater treatment plant, water trunk mains, and about 160 kilometres of roads.

That risk assessment followed the release in July 2019 of coastal hazard maps showing areas of lowlying land and how it may be affected by sea level rise scenarios in half-metre increments, from 0.5m to 2m.

A rise of 0.5m is tipped as possible by 2060 at the earliest. Those maps also show the effect of higher tides caused by storms.

Now the coastal management project team members at the council want to steer the discussion towards options for adapting to those risks, and are seeking feedback from the public.

Project lead Diana Worthy said there was a mix of options that would broadly fit into four categories – accommodate, protect, avoid, and retreat. ‘‘We are already using these options in various ways.’’

Relocatable houses built in some coastal locations were an example of the accommodation option, she said. Sand push-ups and rock walls were soft and hard protection measures.

A plan change made operative in 2015, directing future expansion of Ma¯pua and Ruby Bay away from low-lying land, was an example of avoidance, while a proposal to relocate the Motueka wastewater treatment plan illustrated managed retreat.

Servicing the settlements of Motueka, Riwaka and Kaiteriteri, the Motueka wastewater plant is near the coast, adjacent to the Motueka River within an area expected to be vulnerable to coastal storm inundation. Rather than seeking to renew the plant’s resource consents when they expire, the council is looking at relocating it inland within 15 years.

Worthy said the engagement now was at a ‘‘high level’’ and not sitespecific. The next stage would be local-level discussions.

‘‘These are complex issues, so it is important we start the conversations now,’’ she said.

‘‘At this stage, our focus is to raise awareness and develop a common understanding about what we know and the options we have. It’s an opportunity to talk generally around the options.’’

Resource scientist Glenn Stevens agreed that the options that were ultimately used would be guided by central Government decisions, the proposed replacement legislation for the Resource Management Act in particular. However, the views expressed by residents now would not be wasted.

‘‘They’re still useful,’’ Stevens said, adding that the engagement would help residents prepare for what they might face and help with future decision-making. ‘‘It’s a start, getting all our ducks in a row.’’

Residents are invited to find out more by registering for one of three planned webinars. The first is scheduled to be held from 7pm to 8pm next Tuesday, September 28, with the second on Thursday, September 30 from noon to 1pm, followed by the third later that day, from 7pm to 8pm.

Worthy said that while the rate of sea level rise was uncertain, it would have increasing implications for development and infrastructure in coastal areas, along with environmental, cultural, economic, and societal effects.

‘‘We want to understand the views on these options, and if there are alternative options or ideas for coastal management that we should consider.

‘‘Long-term adaptive planning work will take several years to complete, and the community conversation will be ongoing. However, the decisions we make over the coming years will affect generations to come – shaping the places we live, work, and value.’’

Further information about the project, with links to feedback forms, is available online at tasman. govt.nz/my-council/projects/ coastal-management-responding-toclimate-change/, with feedback due to close on October 15.

‘‘These are complex issues, so it is important we start the conversations now.’’ Diana Worthy, coastal management project lead