Maidenhead Windsor and Eton Flood Alleviation Scheme
Overview
The Maidenhead, Windsor and Eton Flood Alleviation Scheme
The Maidenhead, Windsor and Eton Flood Alleviation Scheme is made up of a combination of different elements in to reduce flood risk in the area. These include
- Cookham - flood walls, flood gates and earth embankments
- North Maidenhead - flood walls and an earth embankment
- The Jubilee Flood Relief Channel
These were designed to work together to reduce the risk of flooding to approximately 3,000 properties in Maidenhead, Windsor and Eton. The Jubilee Flood Relief Channel is not designed to reduce flood risk to communities upstream or downstream of the scheme. It does not adversely impact communities downstream.
On this page you can find out about the Jubilee Flood Relief Channel.
Jubilee Flood Relief Channel repair work - updated Friday 20 December 2024
The recent high water levels and flows in the Jubilee Flood Relief Channel have created a scour hole in the western bank of the channel, between Taplow Weir and Berry Hill footbridge. We are carrying out emergency repairs later this week, ahead of more extensive long-term repairs in the New Year. This briefing note provides further information.
What is the issue?
Heavy rains associated with Storm Bert last month resulted in us operating the Jubilee Flood Relief Channel to reduce the risk of flooding to properties in Maidenhead, Windsor and Eton. Flows in the Jubilee reached 120 cubic metres of water per second (cumecs), each cubic metre of water weighing a metric tonne - so levels were high and flows were strong.
While we were operating the Jubilee, we could see - just above the water level - that a section of bank had subsided. As weather conditions settled down and we were able to progressively drop flows and levels in the Jubilee, the full extent of what we now know to be a scour hole was revealed.
In response, we immediately carried out surveys of the embankment, including using divers, to understand the cause and quickly plan emergency repairs. We established that strong eddies had scoured, or eroded, part of the base of the embankment and caused a section above it to subside.
How do we plan to fix it?
Last Friday, 13 December, we partially filled the scour hole with approximately 120 bags of rock lowered into place by helicopter. As surveys showed that the scour hole was deeper than we first thought, we returned on Thursday 19 December to fill the hole with a further 150 tonnes of rock and 50 tonnes of sand using the same method. This will prevent any significant additional erosion of the area and stabilise the embankment.
The river levels in this location are stable and so we are able to continue to manage the Thames and the Jubilee safely.
Next year, we will carry out a more extensive long-term repair.
Jubilee Flood Relief Channel background information
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The 11.6 kilometres long Jubilee Flood Relief Channel is part of the Maidenhead Windsor and Eton Flood Alleviation Scheme (MWEFAS). The channel has been engineered. It is very deep in places around 5 metres and has very steep sides. Although engineered, the channel blends with surrounding landscape with many marginal areas where wildlife can thrive.
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The Jubilee Flood Relief Channel always has some water flowing through it. In flood conditions, we split some of the water away from the River Thames through the Jubilee. The Jubilee provides extra space for this water before it rejoins the River Thames at Datchet.
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We operate weir gates at Taplow to control the amount of water being split into the Jubilee Flood Relief Channel. As the flow in the River Thames increases, we open the gates gradually in small increments to allow water to flow through the channel.
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When the Jubilee Flood Relief Channel reaches capacity and if river levels continue to rise, water would then spill out of the River Thames onto the floodplain. It is possible that properties in the area normally better protected by the scheme could flood. As with any area we would issue a flood warning if property flooding is expected.
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With climate change we are seeing more frequent and more intense rainfall, which will lead to flooding more often across the Thames Valley. In response to this we are having to operate the Jubilee more frequently.
We have created a short video to illustrate how the Jubilee Flood Relief Channel works. Please click on the below to watch this - you can click on the four arrow icon to expand this to full screen.
We have created a second short illustration explainer that answers some of the key questions we get asked about the Jubilee Flood Relief Channel. Please click on the below to watch this - you can click on the four arrow icon to expand this to full screen.
What happens downstream of the Jubilee Flood Relief Channel?
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The River Thames generally tends to respond slowly after heavy or prolonged rainfall, with river levels in the Thames rising slowly, and then staying high for weeks before dropping back down.
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Communities along the lower Thames are at risk of flooding. Many of these communities have suffered serious floods in the past.
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At the Environment Agency we work hard to find ways to reduce flood risk to communities without increasing flood risk to others.
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The Maidenhead Windsor and Eton Flood Alleviation Scheme (MWEFAS) which includes the Jubilee Flood Relief Channel is designed and operated to ensure that it does not make flooding worse for communities downstream.
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The flooding seen along the River Thames, both upstream and downstream of the Jubilee Flood Relief Channel, is caused by the natural behaviour of the river in response to heavy or prolonged rainfall.
Why do we see flooding along the River Thames?
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Rain falls in the hills and travels into the streams and rivers that flow into the River Thames.
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The water then moves gradually down the Thames, and when river levels get too high, water will naturally flow across the floodplain, flooding low lying land including fields and roads and sometimes properties. This happens all along the River Thames.
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If we didn’t use the Jubilee, many homes and businesses in Maidenhead, Windsor and Eton would be at risk of flooding. The flood waters would flow downstream and continue to flood communities downstream of the Jubilee.
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By using the Jubilee Flood Relief Channel, we split some water from the Thames, so that it flows down the Jubilee rather than across the floodplain. This reduces flood risk to homes and businesses in Maidenhead, Windsor and Eton.
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The channel rejoins the Thames just above Datchet in the Royal Borough of Windsor and Maidenhead.
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Communities downstream of the Jubilee do not benefit from it, but they are not at increased risk either.
How do I find out if the Jubilee Flood Relief Channel is being operated at the moment?
You can call Floodline 0345 988 1188 (24 hour service) and enter the unique reference for the Jubilee Flood Relief Channel 215007.
When requested, select 1 for England, select 1 for flood warnings in your area, select 1 for flood warnings, select 1 to enter Code 215007.
Unlike flood alert and flood warning messages, you will not be notified by text, phone, or email that a message has been issued, and this means that you need to call in for information.
If there is a flood alert is in force the alert wording will say that the Jubilee is being operated, and if there’s no flood alert in place there will just be a simple message if the Jubilee is being operated.
The usual pattern is operational message > flood alert > flood alert removal > Jubilee closed.
To find out more about how the Environment Agency work to manage flood risk including the part the Jubilee Flood Relief Channel plays, please watch this video
If you have any further questions please click below to email the Environment Agency
Audiences
- Members of the public
Interests
- Flood management
- Specific projects, issues, or activity pages
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