Cardiff Bay Wetlands Reserve Project Text

wet 'n' wild

by Patrick Ellis

published in Landscape, the Journal of the Landscape Institute November 2004

To say that the Cardiff Bay Wetlands Reserve project has been finished would be rather to miss the point. The engineering works have been done certainly. There is no argument that Edmund Nuttall (Wales) Ltd successfully concluded the final £120,000 contract by the end of November 2003. However most of the team members would agree that, rather than a completed job, what has been achieved to date has been the creation of the conditions for growth.

The 8 hectare reserve lies along the northern shore of Cardiff Bay. Operations Manager Environment for the Cardiff Harbour Authority, David Lowe, explains that in April 2001 the bay attained freshwater impoundment. In very simple terms this refers to the construction of a 1.1 km barrage across the estuary of the Rivers Taff and Ely. Sanctioned by the 1993 Cardiff Bay Barrage Act despite intense opposition from the conservation lobby, this £220 million initiative has created a 8.8 million m3 freshwater lake. In a very short time the peripheral reserve was transformed from estuarine salt marsh to freshwater wetland.

According to Lowe, although Cardiff was once the biggest coal exporting port in the world, by the 1980s the area was in serious decline. The impoundment was intended in part to establish a stable waterfront to the docks. This was seen as a key catalyst for economic regeneration.

Recognising the benefit of the 'excellent recreational potential' offered by the new 200 hectare water surface he also points out that the 1993 Act obliges the harbour authority to promote flora and fauna in the bay area. 'Developing the Wetlands Reserve helps us to fulfil this condition,' he says.

Consequently early 2001 saw the establishment of the development team. According to landscape architect Phil Williams '… there was a change of emphasis in the project at this time. By agreement with the Welsh Assembly, Cardiff County Council had taken over control of the barrage project from Cardiff Bay Development Corporation. To manage this new responsibility the council established the harbour authority. With the latter body in the client role the team drew heavily on the expertise of the council's Highways and Parks Service Area staff.'

David Lowe was Project Manager. Williams in his role as Landscape Officer and Parks Conservation Officer Chris Powell, who also belongs to the Landscape Institute, were involved from an early stage. Other players included Principal Engineer Phil Cadenne and his colleague Paul Warner. Dave Andrews of Environment Agency Wales took part in initial discussions while County Ecologist Vaughan Grantham of the council's Strategic Planning Service Area joined later.

'We were working in a difficult environment,' says Williams. 'The site was not going to develop a new ecology overnight. We didn't know the extent to which the water level in the bay might fluctuate and therefore affect the new communities of species we are trying to attract. Dealing with this changing situation demanded a cautious approach. The site needed careful monitoring.'

Chris Powell agrees that the challenge was tough. He emphasises the value of working with a strong team. 'There was excellent communication between members,' he says. 'We were particularly glad of the opportunity for direct dialogue with Environment Agency Wales. Their early input was invaluable.'

This dialogue led to the adoption of one of the project's defining features. A proposal to protect the wetland's southern margin with sheet piling had been rejected. 'We recognised this as a functional option in certain situations,' says Williams. 'But felt it was both ecologically and visually sterile and therefore inappropriate here'.

The preferred solution was the installation of a submerged bund formed from ecologically inert stone. The spoil from the Environment Agency's river channel clearance in the Taff at Pontypridd was made available free of charge.

Valued at £370,000, the first contract was won by local firm Horan Construction. Contract management and much of the site supervision fell to Phil Cadenne and Paul Warner. This work included the establishment of the axial pedestrian and cycle route through the reserve and the excavation of the reen, or moat, to isolate and protect the colonising species on the larger southern portion. But the most substantial element was the construction of the bund.

The stone, which had been stockpiled on-site, was tipped directly into the bay to build a causeway. 'It's about four metres wide and 360 metres long,' says Cadenne. 'And about 30 metres into the bay beyond the reserve margin'.

Initially protruding above the water, the structure received its final profile from the excavator as it left the site. The fact that the top is 0.20 metres below bay level does give Williams cause for regret. 'Because it remains under water, the public can't see everything they had for their money', he says.

With the bund in place, the next challenge was 'how to keep the wetlands wet.' Surface runoff from Windsor Esplanade, from a new residential development to the west to the site, and from the St David's Hotel car park passes through two petrol interceptors before being collected in an open reservoir at the north of the site. Water can then be released via a system of sluices to maintain the necessary levels.

In practice due to the stability with which the bay has been managed, the levels on the reserve have been self maintaining. Williams suggests that weather conditions may also have had an effect. 'In the early life of the project the impact of such variables is still being assessed,' he observes. David Lowe comments that, in anticipation of more testing conditions an abstraction license is being sought from the Environment Agency to allow temporary pumping from the bay.

During the tenure of the Development Corporation, Slimbridge Wildfowl and Wetlands Trust had carried out early consultative work. Developing their recommendations the team specified a boardwalk which gives access to a viewing platform in the bay.

The framework, which is angled to optimise viewing interest, is South African Ekki. 'This wood has a life expectancy in excess of 25 years,' says engineer Paul Warner. 'It is difficult to work but its resistance to marine borers makes it particularly suitable here'.

Installed by piling specialists Marton Civil Engineering of Nantgarw, the £137,000 structure is supported on tubular steel piles. Some of these reach 11 metres through the clay bed before finding a stable footing on the marl substrate. 'The boardwalk is engineered to carry a full load of spectators, ' says Warner. 'It could serve as a grandstand for events in the bay if necessary.'

Chris Powell is well aware of the potential conflicts of use in this area. He sees the bund as a significant asset in this respect. 'Its original purpose has been achieved,' he says. 'It certainly breaks the wave energy. But it does a lot more than that.'

As well as facilitating the work of the Environment Agency, the bund protects the wetland from incursion by other bay users. With the water at its nominal level of 4.5 AOD (above ordnance datum) the draught over the feature is very shallow. This prevents leisure craft from getting too close to the margin and disturbing the wildlife.

The benefits don't stop here. By creating a new lagoon the bund has also increased the reserve area to nearly 10 hectares. And the 1.5 metre deep lagoon is developing its own ecology. It is already becoming established as a spawning ground for many fish species including residual estuarine Flounders and the locally colonising Chubb, Roach, Rudd, Stickleback and Minnow.

Which is good news all round. More fish mean more birds and County Ecologist Vaughan Grantham is particularly pleased to report Kingfishers and Herons on the site, and the less common Little Egret. 'The birds and the fish are important species communities here,' he says. 'Some, such as the two pairs of mute swans now breeding on the reserve, will build up a tolerance to the public. However migratory birds such as Teal will remain wary.'

Having said that, last winter Grantham counted 120 Teal, in the reserve's shallow waters and 180 Snipe around its soft muddy edges. During the same period he also noted Water Rails and 40 Lapwings. 'This ability to attract over-wintering birds is the real success of the reserve,' he says. ' Lapwings, with their high conservation priority in Wales, are a particular achievement'.

Grantham joined the team in late 2001 by which time the first two contracts had been written. Contract three gave him more opportunity to become involved. He was instrumental in improving the habitat diversity of the reserve by increasing the number of 'scrapes', or shallow excavations into the surface.

Project Manager Lowe points out that the construction elements benefited from good design, relatively low technology and a spell of fine weather that allowed completion on time. 'With the exception of the bund and the boardwalk much of the work was cut and fill,' he says.

To maintain neutral impact on the bay's flood storage capacity, all material excavated from below the surface was disposed of under water. In contract three the arisings were spread along the shore side of the bund. Subsequently this area has been planted with Common Reed.

Early efforts were not spectacularly successful. It is hoped that supplementary work during summer 2004 with larger material from within the site itself will establish and spread the full 360 metres. Reinforcing the screening effect, this will make the lagoon more attractive to wintering ducks and complement the Harbour Authority's own litter boom a further five metres to the south.

It is fair to say that the last three years have been a period of transition. Within six months of freshwater impoundment most of the salt marsh plants had died out. Since then a slow process of natural re-colonisation has been boosted by the hand of man. The final phase three plantings in early 2004, for example, included Branched Bur-reed, Common Reed and Marsh Marigold. Yellow Water Lily, Greater Spearwort, Water Crowfoot and Pondweed have further enhanced the reserve's biodiversity.

Chris Powell is pleased with the way these new communities are establishing in the reserve's rich alluvial soil. Some of the spontaneous colonists are not so welcome. One immediate priority is to spray off Japanese Knotweed before it has a chance to establish. Also Powell is keen to prevent the development of Alder or Willow carr which would quickly dominate the site, transpiring away water and shading out the tall herb fen and other target plant communities.

Well aware that from now on maintenance will be the key to the reserve's success Powell is anxious to establish a service level agreement with the harbour authority. And, although wardens do patrol daily, he would like to increase this presence. 'This would help us monitor the site more effectively, tackle maintenance issues promptly and deal with the public's queries direct,' he says.

Interaction with the public is a theme that is echoed in the comments of the Countryside Council for Wales. 'The site has huge potential for raising understanding and awareness of the value of Cardiff's wildlife heritage,' says Dr Sue Howard, Cardiff and Newport Team Leader. 'It provides an opportunity for people to appreciate the wildlife on their doorstep. They can become involved in a variety of issues such as Cardiff's Local Biodiversity Action Plan, the European importance of the adjacent Severn Estuary and the local nature reserve on Flat Holm. Such sites are important to people's health and well being.'

Recognition from an external agency such as this goes a long way to confirm the team's own sense of success. Phil Williams is upbeat about the future. He points to the educational value of the site. A pond dipping platform on the southern edge of the reservoir will, he feels, be particularly beneficial for local schools.

He is confident that, as the reserve becomes more established, it will be a major draw for the public. He is excited by the proposal to install CCTV on the site and feels that '… this would enhance the educational function still further by streaming images of the reserve into nearby Techniquest.'

And then there's the recreational aspect. Situated a mere 10 minutes walk from the city's smart waterfront bars and restaurants Cardiff Bay Wetlands Reserve is an ideal spot for a postprandial stroll. With this proximity coupled with a rapidly developing ecology proving the reserve's success, there would seem to be no reason why the foundation that the team have created should not grow from strength to strength. Given adequate maintenance funding that is.

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