Idless flood storage reservoir upgrades will be operational by December, reducing tidal and river flood risk

The newly refurbished tidal barrier forms a critical part of Truro's comprehensive flood risk management system working alongside the Idless and New Mills Dams to reduce risk to commercial and residential properties in the city centre.

The ambitious engineering project began in April 2024 and involved replacing existing gates that had reached the end of their serviceable life. The new gates were successfully installed in August 2024 using a 400-tonne crane during a carefully planned operation that coincided with spring tides to ensure optimal working conditions.

During construction, the project's robust emergency planning was put to the test when tidal surges exceeded forecasts. Temporary flood barriers called stoplogs were deployed for the first time at Truro, successfully protecting the city from flooding and demonstrating the effectiveness of the Environment Agency's flood protection planning.

The gates are designed to be closed during high spring tide and storm surges, providing reliable protection that will operate effectively for decades to come.

The project has delivered unexpected benefits for local sport. When the existing barrier control room needed replacing due to upgraded specifications, the Environment Agency found a new home for the old building at Perranporth Cricket Club. Working with construction partner Kier, the prefabricated building has been transformed into a pavilion, providing additional changing facilities to support the growth of female cricket at the club.

This demonstrates how major infrastructure projects can create positive outcomes beyond their primary purpose, supporting community development alongside essential flood protection.

Andrew Houghton, operations manager at the Environment Agency, said:

This project represents a significant investment in Truro's flood resilience. The barrier and its controls are more reliable, meaning we can ensure effective flood risk management for the community into the future.

Philip Ramsay, operations director for Kier Natural Resources, Nuclear & Networks, said:

The whole team is proud to have been part of the refurbishment of this vital Cornish flood risk management scheme. We've applied innovative techniques and experience from other sectors to make these gates more efficient and reliable.

Completion of the tidal barrier work is scheduled for the end of October 2025, marking a significant milestone in protecting Truro from the increasing flood risks posed by climate change.

Beyond the new tidal barrier, the Environment Agency is enhancing flood protection across Truro through coordinated improvements to the city's reservoir infrastructure.

At Idless Flood Storage Reservoir on the River Allen, vital upgrades to improve the dam's resilience during severe weather are nearing completion. These improvements will ensure the reservoir continues to provide reliable flood protection when extreme conditions put infrastructure under greatest pressure. The enhanced system will be fully operational by December 2025.

Meanwhile, rigorous testing of emergency procedures has strengthened preparedness across the network. In July 2025, specialist Environment Agency teams successfully conducted a major exercise at New Mills Dam flood storage reservoir, demonstrating their ability to rapidly reduce water levels using high volume pumps. A follow-up desktop exercise in September 2025 completed comprehensive training that ensures compliance with reservoir safety legislation and establishes best practice procedures for similar operations nationwide.

Together, these three flood risk assets - the new Truro tidal barrier, the upgraded Idless reservoir, and the operationally-tested New Mills Dam - provide multiple layers of protection that will safeguard Truro against flooding for decades to come.

The Environment Agency are working on a flood risk strategy for Truro to manage the resilience to future flood risks in the city. The strategy is considering climate change impacts, including rising sea levels, increasing river flows and increased rainfall intensity leading to more frequent surface water flooding. This work is being undertaken in partnership with Cornwall Council.

This announcement comes during Flood Action Week; the Environment Agency's annual campaign encouraging people across England to check their flood risk and prepare for potential flooding.

The UK is experiencing more frequent and intense extreme weather due to climate change, and this year, the Met Office has warned of a wetter than average autumn. Communities are warned not to be complacent about the risk of flooding even though drought is still being felt in some parts of the country. Around 6.3 million homes and businesses across England are at risk of flooding from a range of sources, including rivers, the sea, and surface water.

Taking action to protect your home, belongings and loved ones begins with checking your flood risk, getting flood warnings, making an action plan, and considering installing property flood resilience measures. Go to gov.uk/prepare-for-flooding.

New Truro tidal gates ready to swing into action