Overview

The recent exceptionally wet winter weather, localised flooding nearby and concerns about the condition of both the St Ives and the Brownshill Staunch sluices have prompted questions to be asked of the Environment Agency and its partners.

The future of these structures is challenging and the Environment Agency is actively working to identify a long-term approach and available funding for the two structures, considering their primary purpose.

Public event

We are holding a public event on Monday 12 August 2024 (16:00 to 19:00) at the St Ives Corn Exchange. This is your opportunity to find out the latest developments, speak with staff involved in this project and to ask us any project-specific questions. We will also be running two presentations (at 16:30 and 17:45) to go into more detail about aspects of the project.

St Ives Corn Exchange, The Pavement, The Old Riverport, St Ives, Cambridgeshire, PE27 5AD

The venue is close to a number of public transport routes and car parking is available nearby

Background

St Ives Staunch consists of seven sluice gates with a lock gate situated alongside. Four of the seven sluice gates are in poor condition. To manage the risk of the gates becoming stuck open, leaving us unable to maintain statutory water levels for navigation, the four gates have been isolated in the closed position.

Located downstream of St Ives Sluice, the Brownshill Staunch Sluice is made up of three sluice gates with a lock gate situated alongside the structure.

Two of the three sluice gates are in poor condition and have been isolated in the closed position to manage the risk of the gates becoming stuck, leaving us unable to maintain statutory water levels for navigation.

What have we done?

We have assessed a range of information, including river modelling, costs, economic benefits, condition surveys of the asset and historical information. This has been used to understand both the role the sluice plays in managing flood risk and the viability of a potential project.

For all projects, we must demonstrate that capital investment is cost beneficial and value for money. This means the ratio of the benefits of a scheme outweigh the costs. The amount of funding we are eligible for is determined by a funding calculator which prioritises funding for projects which have the greatest benefit to people and the environment. The biggest factor in determining eligibility for funding is the risk of internal flooding to property (homes and businesses).

We have used hydraulic modelling in the case of the St Ives Staunch Sluice to determine the impact the structure has on flood risk. We have modelled several operating scenarios:

• Scenario 1: All seven gates operational.
• Scenario 2: Four gates operational, three gates closed.
• Scenario 3: All seven gates closed.

The modelling indicates that in Scenario 2, whilst there is an impact on river levels, no additional properties are at risk of internal flooding. In Scenario 3, one additional property is at risk in the 20% AEP¹ and two additional properties are at risk in a larger 1% AEP event.

The modelling also indicates that the increase in river levels diminishes the further away from the sluice you go. Scenario 2 and Scenario 3 shows no impact on river levels 0.3km and 1km upstream respectively.

The output of the hydraulic modelling has also been supported by real world data collected over numerous years.

Overall, this evidence demonstrates that, based on the funding calculator we are required to use St Ives sluice, that provides limited flood risk benefit and is uneconomic. Under the current funding policy arrangements, a project would not therefore be eligible for government funding. The evidence also suggests that the current condition of St Ives Staunch Sluice is not having a significant impact on the risk of properties flooding.

We are currently reviewing the evidence relating to the Brownshill Staunch Sluice, but early indications are that the situation is likely to be the same. As a result, we are unable to attract funding via the normal route, but we are continuing toexplore alternative avenues for capital funding to support these structures.

What are we doing?

We’re actively working to identify a long-term approach and available funding for the two structures, considering their primary purpose. We expect this to take some time so in the meantime we are continuing our inspection regime at both structures to ensure they remain safe and to monitor their condition. This includes:

• Operational checks
• Visual asset inspections
• Mechanical, electrical, instrumentation, control and automation maintenance on operational elements
• Public safety risk assessment inspections
• Ongoing reviews of our contingency plans

At the public event on Monday 12 August 2024, we would appreciate your feedback regarding the development, for your say is important to us.

Why your views matter

What should you do?

If you are concerned about the risk of flooding to your property, we advise you to:

1. Sign up to flooding warnings - Flood warnings give people valuable time to prepare for flooding – time that allows them to move themselves, their families and precious items to safety. Flood warnings save lives and enable the emergency services to prepare and help communities Sign up for flood warnings - GOV.UK (www.gov.uk)
2. Check your flood risk- Check the long-term flood risk for an area in England - GOV.UK (www.gov.uk)