Thames Barrier future closure numbers tool
Source: gov.uk (2025-04-04)

How adaptive planning approaches are being used to prepare the Thames Estuary for rising sea levels and changing river flows.

Thames Estuary 2100 – Projections of future Thames Barrier average annual closure numbers

James Brand (https://www.gov.uk/government/collections/thames-estuary-2100-te2100) 1 and Ivan Haigh (https://www.southampton.ac.uk/people/5x8vj5/professor-ivan-haigh) 2

1 Environment Agency, United Kingdom

2 Ocean and Earth Science, University of Southampton

The Environment Agency collaborated with Professor Ivan Haigh from the University of Southampton in 2021 to 2022 to create a tool to model projected future annual closure numbers of the Thames Barrier. The Thames Estuary flood defences, including the Thames Barrier, protect over 1.4 million people and £321 billion worth of residential property in London and the wider estuary (Environment Agency, 2021). To make sure that the Thames Barrier continues to operate reliably, the number of closures needs to be kept at or below an average of 50 per year to allow sufficient time for maintenance.

The projection tool that the team developed uses a Monte-Carlo modelling approach. It simulates a range of possible outcomes to predict minimum, maximum, and average projections for numbers of future barrier closures. As a result, the tool provides a more comprehensive understanding of future closure numbers which allows planners to consider not just sea level rise but also the effects of tidal cycles and storm surges, forecasting improvements, and even potential shifts in fluvial flow.

Impact

The level of detail provided by the projection tool enabled the Thames Estuary 2100 Plan (TE2100) (https://www.gov.uk/government/collections/thames-estuary-2100-te2100) to make more informed decisions about critical deadlines. For example, the tool’s insights led to an adjustment of the first defence-raising deadline for London from 2065 to 2050—15 years earlier than initially planned. This major shift reflected not only updated climate data, but also the anticipated impact of inter-annual tidal cycle peaks on closure frequency.

Beyond simply updating timelines, the tool’s projections enable the Environment Agency to plan strategically. It allows the Environment Agency to test future scenarios where forecasting accuracy does not achieve expected improvements, preparing for possible adjustments in barrier operations and maintenance or further changes to defence raising deadlines.

The tool also helps planners evaluate how future maintenance schedules could be optimised to reduce disruptions during periods with a higher likelihood of closures. This insight is particularly valuable for long-term contingency planning, as it offers flexibility for adapting both routine and large-scale maintenance projects.

Professor Ivan Haigh spoke about the importance of the tool (2024):

Around the world there are more than 50 storm surge barriers in operation protecting tens of millions of people and trillions of pounds of property and infrastructure. However, with climate change, surge barriers are closing increasingly often, and closures are now occurring in months when they typically have not occurred in the past. Increased use of surge barriers in the future has critical implications for barrier management, maintenance and operation.

Working closely with staff in the Environment Agency, we have produced a flexible tool that can estimate how much more often and which times of the year operators are likely to have to use their barriers. Working with the Environment Agency, and other barrier operators in the Netherlands and USA, we have considered the implications of this on future barrier management and maintenance, and identified when in the future barriers might have to be upgraded and replaced.

The tool supported a path forward in climate-resilient infrastructure. The adaptability and foresight embedded in this approach make it a model for global flood risk management. Tools like the barrier closure projection tool have proven indispensable for maintaining the balance between protection, maintenance, and operational efficacy. The use of the tool has demonstrated that proactive steps are being taken to safeguard London’s future and that the insights gained can benefit cities and flood defences across the globe.

Dr James Brand added (2025):

This tool has provided us with vital new evidence to inform our strategic planning for managing London’s tidal flood risk. It helps us to test different scenarios for managing the flood defence system and allows us to make better informed decisions when setting deadlines for implementing improvements to the tidal flood defence system.

Resources

Department of Environment, Food and Rural Affairs (Defra) and Environment Agency. (2023). Thames Estuary 2100 Plan. Available at: https://www.gov.uk/government/collections/thames-estuary-2100-te2100 (Accessed: 24 March 2025).

Environment Agency. (2021). Thames Estuary 2100: 10-year monitoring review (2021). Available at: https://www.gov.uk/government/publications/thames-estuary-2100 (https://www.gov.uk/government/publications/thames-estuary-2100-te2100-monitoring-reviews/thames-estuary-2100-10-year-monitoring-review-20210) (Accessed: 24 March 2025).

Haigh, I., D’Arcy, E., Brand, J., Inavatillah, A., Trace-Kleeberg, S., Walraven, M., Saman, K., Batchelor, A., Lewis, C., Barlow, N.L.M., Thompson, P., O’Brien, P. and Marzion, R. (pre-print). Rapid Acceleration in the Number of Closures of Storm Surge Barriers in the Future: A New Tool for Estimating Barrier Closures. Available at: https://www.preprints.org/manuscript/xx-xxxx-xxxx/v1 (Accessed: 24 March 2025).

Funder
- Environment Agency
Research period
- 2021 to 2022
Impact period
- 2023 and out to 2100
Impact country
- England
- Variants are also being used in the Netherlands and the USA
Contributing to the areas of research interest
- 6 - Digital technology