Skyfall och avrinning från gröna tak med sedumvegetation / Heavy rainfall and runoff from green roofs vegetated with sedum
Precipitation and runoff are increasing due to changes in climate and urbanization. As a result, more stormwater is produced and needs to be handled locally. Internationally, roofs with vegetation are regarded as a suitable measure for sustainable urban drainage system (SUDS), but have not been much studied in Norway. For five years, two extensive green roofs with substrate depth 3 cm have been compared with a roof without vegetation in a rather harsh environment in Oslo. Annual retention for the green roof was 25 %. The retention of intensive rainfalls could be 50 % and even higher for extreme events. Green roofs without drainage systems performed best. A 1 cm cloth under the substrate increased the performance and made the vegetation flourish. Green roofs utilize areas that are in little use, and are a good supplement to SUDS on costly ground areas.