Sizewell and the sea

The design of the power station, including its sea defence and the raised platform it will be built on, will protect Sizewell C from flooding. Our plans take account of the effect of climate change and the predicted rise in sea levels over the coming decades. 

Coastal stability

It is true that parts of the Suffolk coastline are experiencing erosion. However, Sizewell is located on a more stable section of land, between two hard points and the offshore bank of sediment known as the ‘Dunwich - Sizewell Bank’. 

Sizewell A has stood on the same part of coastline since 1966 and Sizewell B has operated since 1995. In more than half a century, neither of those power stations has seen any flooding or significant coastal erosion. 

The Government’s Centre for Environment, Fisheries and Aquaculture Science (CEFAS) is based in nearby Lowestoft and has comprehensive data for coastal change on the East Coast going back to the 1800s. The data show that this part of the coast has been very stable.

Radar measures wave action along the Sizewell coast

Sea level predictions

Climate change will lead to rising sea levels around the world. Official forecasts for the UK are published by the Met Office Hadley Centre Climate Change programme as UK Climate Projections (UKCP). They are regularly updated and peer reviewed. 

While the latest projections (UKCP18) provide general, UK-wide estimates of the effects of climate change they also show there will be regional variations. For example, the projections for conditions at Sizewell show that even under the worst-case climate scenario, maximum wave heights are likely to decrease.  

Sea defence

Sizewell C will be built on a platform standing approximately 7 metres above today’s mean sea level and will be protected by a sea defence structure which will be more than 14 metres above mean sea level. These and many other measures incorporated into the design of the power station will protect it from the sea.  

To make sure our plans are future proof, our sea defence will be adaptable and could be raised in future if sea level rise turns out be greater than current predictions. Based on current forecasts, any adaptation would not be needed until 2140. 

We have performed thousands of hours of flood risk modelling using the highest plausible estimates for sea level rise in the Sizewell area. Our assessments show that the power station and access road will be built to withstand a 1-in-10,000-year storm and 1-in-100,000-year surge events.   

Although extreme storm events could result in some sea water coming over the sea defence and pooling around the site, it would drain away in a matter of hours. This is predicted, planned for, and reflected in the design of the entire Sizewell C site. 


Drones are flown over the Sizewell beach each month and photograph every 3cm square of the coastline, producing 3D maps of any changes. Radar and tide gauges will also allow us to monitor sea conditions and levels at Sizewell throughout the lifetime of the power station. If there are any unexpected developments, we will take action to address them.

Drones monitor changes on the Sizewell coastline


Our sea defence plans are strictly regulated by the following organisations:

East Suffolk Council

The Development Consent Order we require for the power station comes with a legal requirement to monitor and mitigate coastal processes throughout construction and operation. 

Environment Agency 

The Environment Agency is responsible for flood and coastal erosion risk management activities on the coast and works in partnership with the Met Office to provide flood forecasts and warnings. Throughout the Construction and Operation of Sizewell C, the Environment Agency will work together with the Local Flood Authorities and Sizewell C to ensure that adequate Flood Risk Management measures are in place.

Office for Nuclear Regulation

The ONR is responsible for regulating safety and security at nuclear sites across the UK. This includes ensuring the design, construction, operation and decommissioning of the Power Station includes a high level of protection against external hazards such as flooding taking account of climate change predictions. The ONR will have to be satisfied that Sizewell C is resilient to any coastal flood (or other) hazards for the entire lifecycle of the facility including recommissioning and remediation prior to any significant construction beginning.   

Further reading

Read the 2021 Sizewell Coastal Defences report here and the draft Coastal Processes Monitoring and Mitigation Plan (CPMMP) here.