Barrage story

The Cardiff Bay Barrage is 1.1km long and extends from Cardiff docks in the north to Penarth in the south. This major civil engineering construction project subsequently led to the impoundment of the Bay, which boasts over 13km of waterfront.

The £220 million plan, which commenced in 1994 and was completed in 1999, was the catalyst for the £2 billion regeneration of the old docklands areas of Cardiff and Penarth.

The Barrage features locks and bridges, sluice gates and a fish pass. It also provides a landscaped embankment area – a public open space – where visitors can promenade and picnic, with excellent views out over the sea and Inner Bay.

 

How does the Barrage work?

Around the Barrage site you’ll find information boards outlining its day-to-day running. Here are further details about the individual components that make up the Barrage structure:

Barrage control room

At the centre of Barrage operations, the control room is staffed 24 hours a day, 365 days a year by a team of operators, lock managers and engineers. The room is the main point of contact for boats navigating to and from Cardiff Bay.

Locks & bridges

There are three locks on the Barrage; each one is 40m long, two are 8m wide and one is 10.5m wide. They allow boats to navigate between the Severn Estuary and Cardiff Bay. Each lock can accommodate up to 10 average sized vessels, with passage through the locks taking between 5 and 20 minutes, depending on the tide.

Each lock has a bascule bridge weighing approximately 88 tonnes. As the estuary has a high tidal range, the sector lock gates are up to 16m high to enable the boats to pass through at all stages of the tide.

When the locks are closed, they allow passage over the Barrage structure for pedestrians, cyclists and vehicles.

Sluice gates

There are five sluice gates that control the level of water in the Bay. The sluices are used to either allow flows from the rivers Taff and Ely to exit into the Bristol Channel, or to create a barrier to stop the high tide from entering the Bay. Over a quarter of a million litres of water per second can flow through each gate, which is 7.5m high and 9m wide.

The sluice operation uses information from water level sensors in the Bay and the estuary to determine the position of the gates. When the estuary level is higher than the Bay level, the sluices close to prevent seawater from entering the freshwater lake. When the estuary level is lower than the Bay level, the sluice gates open to maintain a preferred level of water.

Fish pass

The Barrage incorporates a specially designed fish pass to allow salmon and sea trout to return to the rivers Taff and Ely. It’s one of the most advanced of its kind in Europe, featuring underwater cameras and motion and audio equipment, which record the fishes’ passage and identify different species.

Salmon and sea trout spawn in the upper reaches of the Taff and Ely rivers in the winter. When the young fish are in the ‘smolt’ phase of their lifecycle, they journey downstream and out into the sea. After a couple of years, the fish, now adults, will return to the river of their birth and the spawning grounds to complete their lifecycle. Salmon from the river Taff have been known to travel as far as the Atlantic, and even the west coast of Greenland, before returning to Cardiff Bay.

Freshwater flows into the fish pass from the Bay and down a system of pools and weirs, which allow fish to swim during all tide stages, from the estuary up and into the Bay. The fish outside the Bay recognise the freshwater from their home river and enter the fish pass.

Cardiff Harbour Authority monitors the fish pass to ensure that it’s operating efficiently – please see our Environment section for further information.

The pink hut

This distinctive, elevated building was designed to be used by local yacht clubs and other event organisers to start and control races in the estuary.

Barrage story