Environment Agency
Over the coming decades, climate change will make average sea levels rise. High tides will be higher and storm tides bigger and more frequent. This will increase the risk of water going over the estuarys tidal flood defences (overtopping).
Thames Estuary 2100 (TE2100) is adapting the estuary to these changes. This workstarted in 2012 and is continuing.
The Environment Agency and our partners will maintain the flood defence system to keep it in good condition while it provides the required standard of protection.
At the same time, we need to prepare to upgrade the tidal defences in phases throughout the rest of this century. Find out how we are taking a riverside strategy approach to upgrading flood defences.
Types of flood risk
Thames Estuary 2100 manages all types of tidal flood risk.
The Thames Estuary is at risk of flooding from:
- high tides
- storm tides
- heavy rainfall
High tides happen twice a day. They are a result of the force of gravity from the Moon and the Sun, and the rotation of the Earth.
A storm tide happens when there is a storm in the North Sea. High winds and changes in atmospheric pressure can cause extremely high water levels, making tides much higher than usual.
Heavy rainfall can cause surface water flooding, fluvial flooding and groundwater flooding. It can increase tidal flood risk in the estuary.
How the estuarys flood defence system works
Map showing 80 km of the Thames Estuary from Twickenham in the west to Southend-on-Sea and Sheerness in the east. It shows tidal flood defences along the estuary by ownership type with the Thames Barrier shown at Woolwich. Private individual, company or charity defences are mostly west of the barrier. Environment Agency defences are mostly east of the barrier. It also shows local authority and unknown ownership defences.
A network of tidal flood defences provides a very high standard of protection in the Thames Estuary. The network includes:
- 330 kilometres (km) of walls and embankments
- 9 major barriers and gates, including the Thames Barrier
- over 400 other structures (including flood gates, outfalls and pumps)
The Thames Barrier is on the River Thames just downstream (east) of the Isle of Dogs in east London. The walls and embankments work in different ways upstream (west) or downstream of the Thames Barrier.
Upstream of the Thames Barrier, the walls and embankments protect against daily high tides. The Thames Barrier protects these areas against storm tides.
Downstream of the Thames Barrier, the walls and embankments are higher than upstream to protect against high tides and storm tides. The Thames Barrier does not protect these areas from flooding.
The Environment Agency closes the Thames Barrier when water levels are forecast to overtop the walls or embankments upstream. This happens when:
- a high tide is predicted to be particularly high
- a storm tide is expected
Closing the barrier stops the high tide from moving upstream. This prevents it from overtopping the walls and embankments and causing flooding.
The lower sections of the rivers that flow into the Thames (the tributaries) are affected by the tide. There are major barriers on some of them, including:
- the River Roding in Barking, east London
- the River Darent in Dartford
- the creeks around Canvey Island in Essex
Walls and embankments protect against daily high tides upstream of these barriers. When tides are forecast to overtop them, the barriers are closed.
Upgrading the flood defences
The network of defences was designed in the 20th century for the water levels that we expected then. We have invested in them so that they still give the standard of protection that we need today. But we need to upgrade them, ready to face higher sea levels later in the 21st century.
We have identified required heights for all the defences in each phase of Thames Estuary 2100. Some defences may already be at the required height above sea level, but we will need to raise others.
Thames Barrier closures and upgrading the upstream defences
The Environment Agency needs to maintain the Thames Barrier to make sure it is reliable and can close when it is needed. But closing it too frequently means it may become less reliable, because it cannot be maintained to the required standards.
Frequent closures would also affect water quality upstream and cause problems for ships navigating the river.
As sea levels rise, the barrier will be closed more and more often for daily high tides.
Raising upstream defences will allow us to let higher tides upriver, reducing the number of times the barrier needs to close. This will mean that it can still be maintained effectively.
Options for adapting to sea level rise
Map showing a 34km area of the Thames Estuary from Greenwich in the west to East Tilbury in the east. It shows 3 potential locations for a future barrier and 4 potential flood storage areas.
There are 7 end-of-century options for the future of the flood defence system. We will carry out the chosen option together with the other defence upgrades.
Upgrade the Thames Barrier
This option involves improving the existing Thames Barrier so that it can manage higher storm tides.
Flood storage and upgrade the Thames Barrier
This option involves creating 4 tidal flood storage areas at:
- Erith
- Aveley
- Dartford or Crayford
- Shorne Marshes
These areas would store flood water, reducing the level of storm tides. This would mean that the Thames Barrier would still be able to keep out storm tides and we would upgrade it at a later date.
New barrier with one set of gates in Gravesend Reach
This option involves building a new barrier within Gravesend Reach, downstream of the existing Thames Barrier site. The new barrier would have a single set of gates like the existing Thames Barrier. This location has a straight approach of 1km, so ships could align themselves to pass through the barrier.
New barrier with one set of gates in Long Reach
This option involves building a new barrier, with one set of gates, in Long Reach, downstream of the existing Thames Barrier site. The new barrier would have a single set of gates like the existing Thames Barrier. This location has a straight approach of 1km, so ships could align themselves to pass through the barrier.
New barrier with second set of gates and locks in Gravesend Reach
This option involves building a new barrier, with 2 sets of gates and a set of locks in Gravesend Reach. The barrier gates would be closed to keep out many high tides as well as storm tides. A second set of gates would provide greater reliability. For example, they could be used when the first set is being maintained.
Locks would allow boats to pass through the barrier when its closed.
New barrier with second set of gates and locks in Long Reach
This option involves building a new barrier, with 2 sets of gates and a set of locks in Long Reach. The barrier gates would be closed to keep out many high tides as well as storm tides. A second set of gates would provide greater reliability. For example, they could be used when the first set is being maintained.
Locks would allow boats to pass through the barrier when its closed.
Convert existing Thames Barrier by adding second set of gates and locks
This option involves adding a second set of gates and a set of locks to the existing Thames Barrier. The barrier gates would be closed to keep out many high tides as well as storm tides. A second set of gates would provide greater reliability. For example, they could be used when the first set is being maintained.
Locks would allow boats to pass through the barrier during closures.
Choosing an option
Well decide on the options by 2040. The decision will be based on:
- the balance of costs and benefits
- an assessment of environmental impacts
- other changes in the estuary that affect the possible locations
- technical considerations
The balance of costs and benefits is very similar between 4 of the options: