Cardiff Bay barrage


Duration:7 years

Cost:£120m (£182m today)

Country: Cardiff, UK

What did this project achieve?

Regenerate the Cardiff Bay area by creating a freshwater lake and all-new facilities

The idea for the Cardiff Bay barrage came on the back of a visit to the area by secretary of state for Wales Nicholas Edwards in the early 1980s.

Edwards, an opera enthusiast, suggested a project to revitalise the area with a development that included new shops and homes and – as a centrepiece – an opera house on the waterside.

However, the tidal nature of Cardiff Bay exposed mudflats for much of the day and was viewed as an unappealing backdrop to the scheme.

It was suggested that building a barrage – a kind of low level dam – across the mouth of the bay would create a more scenic setting by trapping water from the rivers Ely and Taff and creating a deeper freshwater bay.

It was hoped that the new bay would encourage new businesses and investment into the area.

Despite some local opposition, the scheme went ahead. It was the biggest civil engineering project in Europe at the time.

The barrage is now seen as the catalyst for the regeneration of Cardiff Bay. Since it was built, the area has become a premier residential and commercial centre as well as a popular visitor attraction.

Difference the barrage has made

The Cardiff Bay barrage is seen as having played an important role in the regeneration of the area.

Since it was completed in 2001, attractions such as the Wales Millennium Centre and recreational sports companies have moved onto the waterfront. The National Assembly for Wales has also moved in, along with a range of shops.

The structure is credited with boosting tourism and improving the local economy.

How the work was done

The main part of the barrage is a concrete embankment 800m long with a base 100m wide.

Engineers constructed the embankment on a layer of sand and gravel. Rock for the gravel was quarried in south Wales and delivered by lorry. Sand came from the Bristol area.

Project workers built a cofferdam to help with construction. A cofferdam is a watertight enclosure that can be pumped dry to work below a waterline.

The cofferdam, which looked and worked like a temporary dam, was in place for 2 years. Engineers reinforced the sea-facing side of the structure by using rocks as protection from waves.

Workers constructed 5 sluice gates as part of the barrage. Fully computerised and operated by sensors, the gates control water levels in the bay. Other features include 3 locks to allow small boats to enter.

When the barrage became operational in 1999, it created a 2km2 (490 acre) freshwater lake.


The barrage was… instrumental in the regeneration of this area. [We're] delighted that so many people use it in so many ways.

Nigel Howells

Cardiff councillor, talking about the barrage's millionth visitor in 2005.

Fascinating facts

The Cardiff Barrage was a winner of the ICE Brunel Medal for civil engineering.

The barrage saw its millionth visitor less than 5 years after it opened - a golden retriever called Henry, in October 2005. Henry and his owner were taking their daily constitutional across the structure when council officials told them they'd hit the milestone.

The bay is the location for the fictional Cardiff Rift – a wormhole in time and space that features in the BBC TV series 'Doctor Who.' The Doctor sometimes uses energy from the rift to refuel the Tardis.

People who made it happen

  • Client: Cardiff Bay Redevelopment Corporation
  • Constructed by a joint venture of Balfour Beatty and Costain

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