Suggestions for Designing and Constructing Bioretention Cells for a Nordic Climate / Forslag til dimensjonering og utforming av regnbed for nordiske forhold
Bioretention cells (also referred to as raingardens or biofilters) are constructed as shallow vegetated depressions and are generally considered a flexible practice for local stormwater management. Runoff is retained at the cell surface before it percolates to the ground or is conveyed to the stormwater system. Flood risk is reduced via retention and volume reduction of the surface runoff. Additionally, pollutants are removed from the stormwater via physical, chemical, and biological processes in the bioretention system. This paper suggests design principles for bioretention cells based on international literature and Norwegian experiences. The following topics are discussed: facility location, sizing, criteria for local soils and engineered bioretention media compositions, vegetation strategies, and maintenance. Bioretention cells have become popular in many parts of the world but are so far not implemented as a common practice in the Nordic countries. In order to make bioretention a more appealing practice in Nordic cities and communities this paper seeks to give guidance on how to design and build bioretention cells.