Cardiff Barrage
Cardiff BayCardiff
Cardiff CF64 1TT
The Cardiff Bay Barrage in Wales is one of the greatest civil engineering projects in Europe and well worth visiting.
A 0.6 mile (1 km) long barrier has been constructed between Queen Alexandra Dock and Penarth Head, blocking off Cardiff Bay’s entry into the Bristol Channel. Behind the barrage the Rivers Taff and Ely have backed up to create a huge freshwater lake which has rejuvenated the dockland area of south Cardiff. Sluice gates control the flow of the rivers through the barrage and 3 massive sea locks provide 24 hour access to and from the Bristol Channel for leisure craft.
As well as the impressive locks, bascule bridges, sluices and fish pass there is a landscaped embankment walk, a children's play area, and a sea fishing zone.
Pedestrian and cycle paths linking Mermaid Quay and the Penarth Marina cross the barrage giving residents and visitors a chance to view the Bristol Channel estuary, Somerset coast and the regenerated Inner and Outer Harbours. This amazing project has brought Cardiff’s waterfront back to life and made the Bay accessible to everyone.
The Barrage can be reached by car but by far the best way is to catch a river waterbus from the city centre and travel down the River Taff to the docks, then through the Bay to Penarth and the Barrage. A walk across the barrage and the 875 yard (800 metre) embankment will bring you back to the bustling quays of the Inner Harbour and Mermaid Quay with its restaurants, cafes and bars.
Until the barrage was built, Cardiff Docks were at the mercy of the Bristol Channel tides. At really low tides the water level could drop 46 feet (14 metres) leaving exposed mudflats and a shallow channel causing disruption for up to 14 hours. Shipping moved to other ports and the ‘Tiger Bay’ population of south Cardiff became unemployed. Something had to be done to bring the area back to life.
It took 14 years to build the barrage and associated works but successful regeneration has taken place and investment has returned to the area. Cardiff Bay is now a popular place to live, shop, indulge in water-based activities, and attend land-based events. It attracts many thousands of visitors each year.
The main operational section of the Barrage, which includes the locks, sluices and fish-pass, was constructed in the dry, in a sand cofferdam. The sand used was dredged from the Bristol Channel, and was then re-used for completing the embankment.
As far as possible all materials were locally sourced. The stone used for the embankment came from local Welsh quarries. The steel reinforcement came from the steel mill in Cardiff, and the concrete caissons for the outer harbour breakwaters were constructed in the dry dock at Cardiff and floated into position.
A staggering amount of materials was used in the construction of the Barrage - 135,000m3 of concrete; 250,000m3 of rock armour and 1,700,000m3 of sand.
Embankment Paths
The embankment has been landscaped with native and foreign plants which thrive in extreme maritime environments. Visitors can see native Sea Holly, Thrift and Campion along with New Zealand Phormiums in many different hues and sizes, spiky Yucca from America and feathery Tamarix from Asia and the Mediterranean. There are low growing Cistus with pink or white flowers and in springtime the blue flowers of Ceanothus.
The pedestrian and cycle paths are open for use between 07:00 and 22:00 hours every day.
There are three huge 131 feet (40 metre) long locks in the barrage. Two are 26 feet (8 metres) wide and one is 34½ feet (10.5 metres) wide. The locks allow boats to navigate between the Severn Estuary and Cardiff Bay.
Because of the estuary’s high tidal range, the sector lock gates are up to 52½ feet (16 metres) high to enable the boats to pass through at all stages of the tide.
Each lock can accommodate up to 10 average size vessels and passage through the locks takes between 5 and 20 minutes. To minimise water loss boats wait in the outer harbour for the locks to open.
Outbound locks run on the hour and half past the hour. Inbound locks run on a quarter past and a quarter to the hour.
The locks have been specially constructed to prevent saline water from entering the Bay during operation. Any salty water that does get in is contained in a sump and is then flushed out via a 47 inch (1200 mm) gravity discharge pipe.
When the lock gates are closed each lock can be crossed by a bascule bridge. These ‘see-saw’ bridges each weigh 97 tons (88 tonnes) and work on a cantilever design using minimum energy to raise and lower the bridge decks.
Five sluice gates control the level of water in the Bay. Each gate is 29½ feet (9 metres) wide and 24.7 feet (7.5 metres) high and can allow the passage of over a quarter of a million litres of water per second.
The position of the gates is determined by information received from water level sensors in the Bay and the estuary. When the estuary level is higher than the Bay level the sluices close to exclude the tide from the Bay and 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 in the Bay.
The perennial problem of flooding from high tides combined with high river flows from the Taff and Ely has been mitigated by the building of the barrage and sluice gates. Gates are closed to exclude the high tide from the Bay until it ebbs and then opened to release the excess fresh water flow from the rivers.
Fish Pass
Water quality in the rivers of the Welsh Valleys has improved dramatically in recent years and Salmon and Sea Trout are once again spawning in the Rivers Taff and Ely.
The barrage incorporates a specially designed fish pass to allow these migratory fish to return to their home rivers.
Freshwater flows into the fish pass from the Bay and down a system of pools and weirs that allow the fish to swim at all states of the tide from the estuary up and into the Bay. The fish outside the Bay sense the fresh water from their home river and enter the fish pass.
A special fish trap facility allows environmentalists to monitor the success of the fish pass.
Information Points
Around the Barrage site there are numerous large visitor information signs which provide details of the Barrage operation and the surrounding area.
Clean public toilets with disabled facilities are available at both ends of the Barrage.
Contact & Further Information
The Barrage, Inner and Outer Harbours and the Bay are managed by the Cardiff Harbour Authority (CHA).
Telephone  029 2087 7900
The CHA has an excellent website at  Web:  Cardiff Harbour
Getting There
Water Transport
There are two commuter services currently running in the Bay. They both provide a regular service between Mermaid Quay, Penarth (the Barrage) and the city centre. For timetable information contact:
- Bay Link (Aquabus)
Tel:    (029) 2047 2004  
Web:  Aquabus
- Cardiff Waterbus (The Yellow Boat)
Tel:     (07940) 142409
By Cycle
The Cardiff Bay Trail is a 6 mile (10 km) route.
Bicycles can be hired from Cardiff Pedal Power
Tel:     029 2039 0713
or The Cardiff Council Smart Bike Scheme.
By Car
Take Junction 33 off M4 motorway following signposts for Cardiff Bay on A4232. Travel for about 8 miles (12 km) and exit at the junction sign posted Penarth on the A4055 (the Cogan Spur). On the A4055 exit at the next roundabout (at the top of the hill) turning left onto the A4160 and heading toward Penarth.
Turn left after 100 metres at the roundabout, sign posted Penarth Marina. At the roundabout take second left and head towards Penarth Marina. Tesco's is on your right.
At next roundabout go straight on and continue for half a mile over speed bumps, turning left at the roundabout and into the Barrage car park.
You will see the Barrage Control building a short walk away across the lock bridges.