A rain garden* is a kind of garden that primarily serves as area for water control (storage and infiltration) on a small-scale especially in urban areas. Rain gardens are established in artificial surroundings and catches water runoff from roofs, roads and other (sealed) surfaces. Storm water runoff is drained into rain gardens, where it is stored for a certain period, and infiltrates either into the ground soil or flows into the sewage system. A certain amount of water is taken up and transpired by plants. Different designs/arrangements of rain gardens are established and a variety of elements is used to create a rain garden such as grass filter strips, water ponds, mulch areas, planting soil, plants (e.g. herbaceous plants) or sand beds. All the mentioned elements have a particular function for example slow down, reduce, filter and store water runoff or increase evapotranspiration. Beside their function to store and infiltrate storm water, rain gardens have esthetical functions (amenity value). Raingardens are not restricted to a certain climate condition and can be found in different European countries. But, the selected components (plants) should be native and well adapted to local climate conditions.

* In literature refers to as bioretention area (source: (European Commission n.d.a)

Performance

Evapotranspiration 1 1
Shading none none
Reflection (Albedo) none
Water Conveyance none
Water Infiltration 1
Water Retention 1
Water Storage 1
Water Reuse 2
Water Filtering 1
Water Bio-remediation 1
Deposition none
Bio-filtration none
Habitat Provision 2
Connectivity 1
Beauty / Appearance 2
Usability / Functionality 1
Social Interaction 1
Role of Nature / Mode of Action: 
- Processes in rain gardens (vegetation, soil) that are inspired by nature: - vegetation and soil layer retains and stores water, water infiltrates into natural soils (soil substance has an influence on infiltration rate) - plants and soil are natural filters for organic pollutants, sediments and other substances - natural riverbed conveys water - plants take up and transpires water
Technical & Design Parameters: 
- small-scale installation (private gardens or public space) - native plants that withstand occasional flooding - relatively dense vegetation - gentle slope is positive for infiltration - regular maintenance and inspection - access for maintenance and management - can be combined e.g. with rainwater harvesting and permeable paving
Conditions for Implementation: 
- Space
Benefits & Limitations: 
Benefits: - water retention and storage - water infiltration - water filtering - water conveyance - water evapotranspiration

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 730052 Topic: SCC-2-2016-2017: Smart Cities and Communities Nature based solutions