Raingardens Glossary

Browse our glossary to find definitions for some of the terms used in relation to raingardens, as well as photo examples.

All images are copyright Green Action Trust, unless stated otherwise.


A larger depression or sunken area which can be wet or dry, usually taking water at the end of a chain of raingarden features, or when it needs more treatment.

Examples: Manor Park, Sheffield; Athlete’s Village, Glasgow; Mauer Park, Berlin.

See an example in our Community Garden leaflet here.

Bog Garden

A shallow dip designed to stay wet and boggy which can be planted with bog loving plants. Sometimes created at the side of ponds.

Example: Mill Dene Garden, Gloucestershire – image Karen Roe.

See an example in our School Raingardens leaflet here.

Filter Strip

A gently sloping, vegetated strip of land that rainwater can flow over. This gives the rainwater time to evaporate or to filter back down into the ground.

Example: Roadside filter strip, Yorkshire.

See an example in our Leisure Parks leaflet here.

Green Roof

Rooftop planting – like a high level raingarden. The plants and substrate layer slow the rainwater runoff. Plants are chosen carefully so they are able to cope with conditions on the roof. The simplest green roofs use sedum but there are many more varied and interesting options that can increase biodiversity. Some green roofs are accessible to people and form part of open spaces, some include solar panels.

Examples: Iona Abbey entrance building, Iona; Scandinavian Green Roof Institute, Malmo; Gabriel Jossonsgatan, Malmo.

See an example in our Schools leaflet here.

Green Wall

Vertically planted vegetation, often within a designed system which may make use of rainwater harvesting from a roof above. A green façade can also be created by using climbing plants on a supporting structure, altering the maintenance needs.

Examples: P-huset Godsmagasinet, Malmo; NatureScot offices, Battleby; Queen Caroline Estate, London.

See an example in our Leisure Park leaflet here.

In-ground Raingarden

A depression or sunken area which can hold rainwater, and then let it infiltrate back into the ground, or overflow into another raingarden. These can be planted with carefully chosen plants. In-ground raingardens can also be called ‘bio-retention’ areas.

Examples: Taylor Wimpey property Torrance Park, Holytown; Wilses Gate, Oslo; Properties around Sorengkaia, Oslo.

See an example in our Community Garden leaflet here.

Permeable Paving

Paving which lets water through, usually through small gaps, and into a layer underneath it. Good for holding water, but has fewer benefits for humans and wildlife.

Without proper maintenance, permeable paving can clog over time and lose its permeability.

Examples: Manor Park, Sheffield; Zetland Park Rose Garden Raingarden, Grangemouth; Residential street, Berlin.

See an example in our Community Garden leaflet here.


A small body of still water. A pond may be designed to overflow into a raingarden or a swale when it becomes too full.

Examples: Springhill Co-housing, Stroud; WWT Slimbridge, Gloucestershire; Centre for Alternative Technology, Machynlleth.

See an example in our Leisure Park leaflet here.


A wide, shallow ditch, often vegetated, which collects rainwater runoff. The water flows down the swale and out at the lower end. Sometimes swales have small check dams or flow control elements along their length which help slow the water. Sometimes these dams can be walked across, or there may be other features such as stepping stones or bridges to encourage play, or to allow walking and cycling networks to cross.

Examples: Olympic Park, London; Kirroughtree Visitor Centre, Newton Stewart; Grey to Green, Sheffield.

See an example of a swale in our Neighbourhood leaflet here.

Rain Chain

A decorative chain sometimes used instead of a drainpipe as a special feature which provides additional sensory qualities.

Examples: Bridget Joyce Square, London; Alnwick Gardens, Northumberland; GAT Hillhouseridge Raingarden, Shotts.

See an example in our Household leaflet here.

Raingarden Planter

A planter which catches rainwater coming from a downpipe. The water flows through vegetation, free draining soil and gravel layers, then out into another raingarden feature or drain.

Examples: GAT offices Hillhouseridge, Shotts; The Hub, Wellhouse; Queensland Court and Gardens, Glasgow.

Our See Inside a Raingarden Planter leaflet shows you the typical layers found inside a planter.


Vegetation plays an important part in slowing down rainwater. Including suitable trees within a scheme can increase interception of rainfall and reduce runoff.

Examples: East Ordsall Lane, Salford; J4M8 Business Park, Bathgate; University of Sheffield Raingardens, Sheffield.

See an example in our Leisure Park leaflet here.

Water Butt or Rain Barrel

Butts or barrels collect and store water from a downpipe which can then be used to water plants or for other uses. A downpipe diverter sends the rainwater to the butt or barrel until it is full. In heavy rainstorms butts and barrels can help attenuate runoff if the tap is left open slightly, acting as a form of flow control.

Examples: Water butt with downpipe diverter at Springhill Co-housing, Stroud; High capacity water butt at 2B Landscape Architects, Beverley.

See an example in our Household leaflet here.


Land which is often found in the flood zone at the edges of water bodies – wetland can also be designed and built. Wetlands have areas of marsh which stay boggy and wet and can provide valuable habitat diversity.

Examples: Sutcliffe Park, London; Royal Bank of Scotland Headquarters, Gogarburn; Olympic Park, London.

See an example in our School leaflet here.