The warning was issued in an audit of the council’s 2024-34 long term plan consultation document, with Audit saying it considered the council’s funding assumption for coastal hazards as “unreasonable”.
On Wednesday it was announced stop banks had been confirmed as the preferred option for the town’s foreshore with the protection of the town being treated as a high priority after a shoreline management project showed $1 billion in assets in the township were at risk over the long term from hazards associated with sea-level rise.
Audit said the council had assumed 60% of shoreline protection costs ($55.8m) would be funded by Government and considered the assumption unreasonable because Government had not yet agreed to provide funding.
If Government did not provide funding, the council might not be able to proceed, Audit said.
If less funding was provided, the projects might need to be delayed or have their scope revised.
“Until such time as the council decides on these options, we are unable to quantify the effects on the information and assumptions underlying the forecast information in the plan.”
The default design is for a stop bank. An indicative height of 1.3 metres has been suggested. This is what might be expected at Victoria Park in the north end of Thames township.
A public meeting held in June presented various concept designs for protection against a half metre of sea-level rise and a one-in-100-year storm in Thames.
In a statement on Wednesday, the council said that level of storm was becoming more frequent along the Thames coastline and put the town at significant risk of flooding.
“After taking on board public feedback from the meeting, the project’s governance team confirmed stop banks will be constructed where space allows along the Thames foreshore.
“The stop banks will generally follow the existing footpath, with an expected height increase of approximately 1.4 metres.”
While the council was not specific about design or costs, it said in narrow areas with limited space, for example behind the Pak’n’Save supermarket, a wall or sheet-pile solution would be required.
“Everyone involved in the project is also keen to explore additional nature-based solutions that will offer another layer of protection to our town,” project lead Amon Martin said.
“These solutions include things like shell banks, oyster islands and chenier ridges, which could bring a range of benefits, including as habitats for birds.”
It was confirmed Richmond Villas Retirement Village had proposed partnering with the council to deliver a section of stopbank protection associated with its property.
The proposed partnership included Richmond Villas leading the engineering, design and construction process, and covering all associated costs.
It was hoped construction on that section could begin early next year, the council said.
