Thames protection and resilience project

The protection of Thames is a high priority for our district, after the Shoreline Management Pathways project showed that $1 billion in assets in the township are at risk over the long-term from hazards associated with sea-level rise.

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Thames Protection and Resilience project aims to manage the risks to the Thames area from coastal hazards such as flooding and storms, which are expected to worsen as a result of climate change and sea-level rise. The initiative is part of the Shoreline Management Pathways (SMP) planning project, launched in 2019 to address risks along Coromandel’s 400 km coastline.

Through the Shoreline Management Pathways project, 138 unique adaptation pathways were developed, with Thames identified as a high-priority area due to $1 billion worth of assets at risk. The proposed design for Thames protection includes the construction of barriers, such as stopbanks, which will be adapted over time to accommodate a projected sea-level rise of 1 metre over the next century.

The project is a collaboration between Thames-Coromandel District Council, Ngāti Maru, and the Waikato Regional Council, alongside local communities and other iwi.

Flooding risks from streams

Work to understand flooding risks from Thames’ streams, or fluvial flooding, is close to completion. Final modelling reports on the river risk component of the project are expected in early 2025. The results will then be presented at a public meeting in February 2025, along with a wider project update.

The proposed protection design looks to integrate nature-based solutions, such as a chenier ridge, to boost resilience and create habitats. The project team has also undertaken preliminary catchment modelling to assess the flooding risks of Thames’ streams.

“We need robust, effective and long-lasting solutions," said project lead Amon Martin. "So, one of our challenges is to ensure we thoroughly understand all the intersecting risks. "These include fluvial flooding risks and the likely effectiveness of pumping stations and related mitigation proposals.”

Coastal protection design

Progress has been made on getting a better understanding of the coastal protection design parameters, and eliciting community feedback on how protection might blend with existing amenities (such as the walkway and small gauge railway).

Public meetings in 2024 presented various concept designs for protection against a half metre of sea-level rise, and a one in one-hundred-year storm. This level of storm is becoming more frequent along our coastline, and puts Thames at significant risk of flooding.

After taking on board public feedback, the project’s governance team confirmed stopbanks will be constructed where space allows along the Thames foreshore. The stopbanks will generally follow the existing footpath, with an expected height increase of approximately 1.4 metres. In narrow areas with limited space, for example behind Pak’n’Save, a wall or sheet-pile solution will 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,” said project lead, Amon Martin. “These solutions include things like shell banks, oyster islands and chenier ridges, which could bring a range of benefits, including as habitats for birds.”

Meanwhile, Richmond Villas Retirement Village has proposed partnering with our Council to deliver the section of stopbank protection associated with its property. The proposed partnership includes Richmond Villas leading the engineering, design and construction process, and covering all associated costs. It’s hoped construction on this section can begin in early 2025.

Fact-finding has been completed to guide roles and responsibility discussions with Waikato Regional Council, including a review of the Waihou Valley Scheme’s objectives and rating system.

Background

Protection was the preferred adaptation pathway for Thames confirmed by community consultation during the Shoreline Management Pathways project. The three-year project examined the risks to the entire Coromandel coastline from the effects of sea-level rise. Specific actions to manage those risks have now been assessed and ranked, with work to protect Thames among the top priorities.

Have a look at our Shoreline Management Pathways project pages to find out more about this process, including information and maps all of all our coastal communities around Thames-Coromandel district, including Thames.

A governance group to progress the Thames protection work met for the first time in February 2024, made up of representatives from our Council, Ngāti Maru and Waikato Regional Council. A further meeting is taking place at the end of July 2024.

“We know that Thames is especially vulnerable to storm surge and flooding associated with sea-level rise, putting around $1 billion of assets in our township at risk,” says our Mayor Len Salt, who is chairing the Thames Protection and Resilience Governance Group.

“Thames is the economic nerve-centre of our district, home to the bulk of the Coromandel’s service provision, maritime industry, healthcare and business infrastructure. It’s our duty to the entire region to ensure Thames is resilient, and able to grow, for generations to come.”

Royal HaskoningDHV is working on design options to protect the township against coastal inundation for a 1% AEP storm over the next 100 years. An earlier feasibility study showed the main challenge associated with protecting Thames is the required cost and scale of any defensive structures, as many locations are low-lying.

Design work will include full hydrodynamic modelling, and joint probability analysis of coincident coastal and fluvial flooding events. The governance group notes that it will be important that any protection structure connects with other stormwater and river management work.

Funding for the design work, and ensuing community consultation on design options, is allocated through 2023-2024 Long Term Plan, with funding for the construction of protection yet to be determined.

“We’re going to come up against some big costs, but those need to be assessed against the value of what’s at risk,” says our Mayor Len Salt. “We’re facing up to these challenges head-on, and doing the forward-thinking, groundbreaking work that’s required, rather than just hoping the issues somehow go away. It’s a multi-generational vision and long-term action plan.”

For more information visit our Shoreline Management Pathways project page.