A bioswale* is a vegetated, linear and low sloped pit often established in urban areas near/between roads with the objective to reduce flood risk during or after heavy rain events. The intention of bioswales is comparable to rain gardens. Bioswales absorb, store and convey surface water runoff (mainly draining from roadways) and also remove pollutants and sediments, when the water trickles through the vegetation and soil layer. The choice of vegetation for bioswales is variable but deep-rooted native plants are common and preferred. To support infiltration of water runoff, some swales are equipped with dams or similar constructions. Bioswales are not limited to a certain region/country. If properly planned and planted with native plants, a bioswale is a reasonable contribution to local storm water management and control.

* In literature refers to as swale (source: http://nwrm.eu/sites/default/files/nwrm_ressources/u4_-_swales.pdf)

Basic information

Type: 
Retrofitting + Creation

Performance

Evapotranspiration none none
Shading none none
Reflection (Albedo) none
Water Conveyance 1
Water Infiltration 2
Water Retention 1
Water Storage 1
Water Reuse none
Water Filtering 1
Water Bio-remediation 1
Deposition none
Bio-filtration none
Habitat Provision 1
Connectivity 1
Beauty / Appearance 2
Usability / Functionality none
Social Interaction none
Role of Nature / Mode of Action: 
- Processes in bioswales (vegetation, soil) that are inspired by nature: - water retention and storage (vegetation and soil layer retains and stores water) - water infiltration (water infiltrates into natural soils (soil substance has an influence on infiltration rate) - water filtering (plants and soil are natural filters for organic pollutants, sediments and other substances) - water conveyance (natural riverbed conveys water) - water evapotranspiration (plants take up and transpires water)
Technical & Design Parameters: 
- Medium to larger scale installations (larger than rain gardens) - native deep-rooted plants that withstand occasional flooding (often grass, + other plants for esthetical reasons) - relatively dense vegetation (positive for slowing water; too dense vegetation would be negative for water conveyance) - regular maintenance and inspection (grass cutting and removal; removal of sediment) - access for maintenance and management necessary - combination with other SUDs ( e.g. rainwater harvesting and permeable paving) - For planting suggestions see: (Bray et al. 2018)
Conditions for Implementation: 
Storm water from roofs or paved areas need to be collected in order to lead them into a bio swale. Space for implementation is needed, multifunctional uses if possible.
Benefits & Limitations: 
Benefits: - storm water management and control - reduced flood risk - improvement of water quality - habitat provision for wildlife - improvement of amenity value Potential limitations/disservices: - trees are limited  habitat provision limited on ground level

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