Cost of future coastal living getting clearer
Kāpiti residents are getting their first look at what coastal adaptation could mean for their properties – and it could cost billions of dollars.
A nine-member panel has released options for how to adapt to the risks of sea-level rise, with managed retreat the endgame for many of them.
As part of Kāpiti Coast District Council’s Takutai Kāpiti project to figure out the area’s future coastal adaptation strategy, the Coastal Advisory Panel, chaired by former prime minister Jim Bolger, divided the 38km-long Kāpiti coastline into five areas to explore medium to long-term options based on community feedback.
Each area
is subdivided into units and categorised on the risk it faces.
The advisory panel, made up of Kāpiti locals, used multiple-criteria decision analysis (MCDA) to score each option using eight measures including its impacts on ecology, public access, te ao Māori, and its potential effectiveness on managing coastal hazards. The top three scored were picked and sent out for public consultation.
The top-scored option was not a recommendation by the advisory panel at this stage. The panel would recommend options to a council meeting in June where councillors will make the final decision.
New documents this week showed the highest-scored option for flood-prone areas at Waikanae Beach was managed retreat when enhanced protections like flood gates or pump stations were no longer effective at managing the risk.
The document estimated it could cost $935.4 million. The next two options had price tags of $58.2m and $357.9m respectively.
Meanwhile, the highest-scored option for areas at risk of erosion at Paekākāriki and Raumati would rely on sea walls in the short term – some of which have already been slated for renewal – before taking a “hybrid approach of retreat and hard engineering” to move “the minimum of properties possible” and build new structures or materials to protect the shoreline.
The Paekākāriki and Raumati North option cost more than $200m, the document estimated, while the Raumati South pathway had a $422.4m price tag.
Kāpiti Coast district councillor Sophie Handford said while cost was an important factor, there were other things to think about when considering the options.
“We also need to look at other ecological potential benefits of the solution and the practical benefits, in terms of climate resilience,” she said.
“These are conversations that will be tough but it doesn’t mean that we should prolong them more. It more important to have them now because those costs will likely increase if we leave it longer.”
Meanwhile, flood-prone Paekākāriki, Raumati, Otaihanga and Paraparaumu properties would have enhanced flood protections or be proactively raised to accommodate the risk, according to the highest-scored pathway, with each costing between $7.9m to $53.4m.
For the remaining areas, the pathway with the highest score proposed importing sand to build dunes for erosion-prone areas at Waikanae Beach and Paraparaumu Beach. Those pathways are estimated to cost around $20m respectively.
At the Waikanae Estuary, where there are currently no properties, the top-ranked pathway was to have its recreational infrastructure moved to make way for wetland migration.
Earlier draft recommendations published by the advisory panel last July for the northern adaptation area — encompassing Te Horo Beach, Ōtaki Beach and Peka Peka — showed the top-ranked option suggested enhancing dune resilience in the short to medium term for areas at risk of erosion, before moving properties “exposed to the erosion hazard” when dune resilience was “no longer effective” at managing the risk.
The highest-scored option for properties at areas with flood risks was to “enhance” existing protections in the short term, like increasing the drainage capacity of existing stormwater outfalls and more effective planting and managing coastal wetlands.
In the long term, properties with flood risks that could no longer be “effectively managed” through protection and raised floor levels would be moved.
Figures released amongst the documents this week revealed these could potentially cost up to hundreds of millions: carrying out managed retreat at Ōtaki and Peka Peka might carry a price tag of $741m and $90.4m respectively.
Coastal adaptation has been a stormy issue on the Kāpiti Coast. The council previously had court battles over including hazard disclaimers on the Land Information Memorandums of 1800 properties in 2012, and it had to delete them the following year when experts concluded the science was not solid.