The area of Augustenborg in Malmö, was retrofitted with a green open stormwater system in the late 90s. When a major rainstorm hit the city of Malmö in August 2014, Augustenborg was less affected by flood damage than nearby areas. Since the retrofitting of the stormwater system, it was unknown if the solution was efficient for extreme rainfall events with a 100-year or higher return period.
The nature based stormwater solution in Augustenborg, consists of open canals, swales, ponds and green roofs as well as adapted levelling of green areas to ensure controlled flooding. A model of the system was set up in the simulation software MIKE FLOOD. This included the rain on grid and infiltration, to enable correct quantification of stormwater infiltration in green areas. A scenario of the current stormwater system and one for the old pipe-based system was created. This methodology allowed for evaluation on comparison of the two. Results showed that the retrofitted green stormwater system would result in an approximately 80 percent lower discharge, hence substantially decrease risk of flooding.