West Lothian soils have a high clay content, and as a result, most of the area’s parks have drainage issues. As part of wider improvements to Falcon Brae park, an experimental rain garden was created to see if it would address waterlogging. The work took place during 2020/21 as part of West Lothian Council's ongoing capital programme. Whilst upgrading drainage in the park, a suitable site within the grassland, and near hedging, was used to create the rain garden. It is one of the first rain gardens created by the council, and the learning is being used to improve its effectiveness as well as to provide protocols for similar solutions in other West Lothian parks.

Drivers for naturalisation

• To explore rain gardens as a solution to sustainable urban drainage within parks
• To enhance biodiversity and ecosystem services 
• To respond the community's desire for more variety in the park, through providing a more varied landscape, and a wider range of flowers and insects

What has been delivered?

In 2020, an oval basin of 6m x 8m was excavated to a maximum depth of about 30cm. An inlet was created leading from path drainage at a higher elevation. The overflow outlet, higher than the basin inlet, allows the water to enter a manhole and mains drainage in the corner of the park.

Marginal plants were put directly into the clay soil. 450 plants of 14 species were used. The final mix of plants included more species, and a smaller quantity per species, than was originally planned, as it was influenced by what was available from commercial suppliers in the timeframe required.

Enhancement work took place in 2022, using the experience of the first two years, in which one spring season was extremely dry. Topsoil was added, in the hopes it would dry out slower than clay, and restocking took place with species that had proved they could cope with the conditions as well as compete with plants that colonised naturally.

Species list 2020 and 2022

How was it done and by whom?

The council’s Open Space Officer (who has since become their Ecology and Biodiversity Officer) instigated and carried out the project, with drainage advice from the council’s Flood Risk Management team. The company contracted for the wider park improvements (Bennie Contracts Ltd) excavated the basin. Local residents helped with signage ideas, which were developed by a graduate placement within the Ecology and Biodiversity Team.

Communication and engagement

The full park improvement works in Falcon Brae park took place as part of the council’s ongoing open space capital programme. Prior to these works, the Community Regeneration Team consulted the community. Feedback included requests for a greater variety of things to do in the park, improved drainage and more planting. The resulting plan included paths for easier access and wheeled play (e.g. scooters), two benches, a bin, drainage and signage.

How is it looked after and maintained?

Once established, the rain garden should be maintenance free. It is located in an informal area of the park near a cornus (dogwood) hedge with woodland nearby, and over time it will be colonised by plants suited to that environment.

Cost of the project

The complete park improvements cost £37,000 for a perimeter asphalt path, link path through the woodland, drainage and rain garden, bin, benches, fencing and signage. The total cost for the rain garden is estimated to be £4750.

Breakdown of the budget for rain garden establishment in 2020:

£750 contractor excavation works (as part of total drainage works in the park of £6600)

£1500 planting and delivery

Budget spend for rain garden enhancement in 2022:

£2500 for plants, topsoil, replanting and A3 signage

Issues and challenges

At Falcon Brae, the council was unable to source plants locally, in the numbers and within the timescale required, and so they were sourced in Hertfordshire from Wetland Plants. The council wanted to avoid using plastic to line rain gardens. Three more raingardens in different parks have now been created. Two are connected to french drains, but the team have reluctantly used a man-made liner in the third which is in a low area that accumulates run-off.

Learning and advice at Falcon Brae

Use of signage to explain what is happening and why the change is important is essential, particularly at areas that do not immediately look finished. This message is for the community, as well as for operatives who may feel the area needs to be cut or sprayed to stay in keeping with more formal areas. Becky Plunkett, Ecology and Biodiversity Officer, West Lothian Council explained

We are learning by doing. Timing is important to give plants the best chance to establish. We have learnt that many plants of a few key species are best – you need the drama from swathes of one colour, and they need to compete with the ‘weeds’. And you probably need more plants than you think!

Next steps - taking the Falcon Brae learning to other West Lothian parks

Three more raingardens in different parks have been created – trying out a different size, design and planting in each. The team are experimenting with pre-planted coir matting (HabitatAid)  and have yet to see how this performs against using seeds and plug plants. They have learnt that each raingarden needs a fence around it for about a year, whilst the plants get established. This protects them from damage (mostly not intentional) by children and dogs.

The raingardens are intended to be as low maintenance as possible. They are only weeded in initial visits to check establishment. It is therefor important that the chosen plants are able to compete with the grassy/rank vegetation that inevitably creeps in. The plants at Falcon Brae that seem to have been able to compete so far are:  Water forget-me-not, Purple loosestrife, Yellow flag, Water mint and Meadowsweet. It is hoped that these plants will spread even more around the rain garden, and progress will be monitored. If necessary, consideration will be given to introducing plants that are hemi-parasitic on grasses, to reduce their vigour. Some docks are tolerated, as they can be beneficial for insects and birds, but they too will be monitored.  

As well as ongoing experimentation and learning in 2024, West Lothian Council plan to try out sensors to monitor water levels after heavy rain.

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For information on other urban naturalised parks and greenspace projects look at the Lyne Burn river restoration project in Dunfermline, Dundee's biodiversity-rich meadows and grasslands, the native flower meadows connecting Edinburgh's coastline, Naturalising the Lade to Whitfield Pond, East Dunbartonshire and NatureScot's Wilding Our Parks case studies. 

Thanks to Becky Plunkett, Ecology and Biodiversity Officer at West Lothian Council for providing information and assistance, and to NatureScot for the funding to create this as part of a series of naturalised management case studies in 2022.