Utredning kring val av varaktighet vid skyfallskarteringar / Investigation of the choice of rain duration’s impact on urban flood mapping

Utredning kring val av varaktighet vid skyfallskarteringar / Investigation of the choice of rain duration’s impact on urban flood mapping As a result of intensive cloudbursts, runoff creates pluvial flooding. The risk for more extensive flooding increases in urban areas where a majority of the land use consists of impervious areas. At the same time, extreme rain events are predicted both to be more intense and more frequent in the future which needs to be taken into consideration in spatial and community planning. In 2007 the European Union adopted a flooding directive with the purpose of mapping flooding threats and create risk assessments plans to reduce the consequences of extreme rain events. This has been implemented in Sweden by regulations and it has been declared that the Swedish Civil Contingencies Agency is the responsible authority for the preventive work against floods. In the guidelines published by the Swedish Civil Contingencies Agency, county administration boards and The Swedish Water & Wastewater Association there is a recommendation on which safety level the design rains should have in cloudburst mapping. However, the rain volume and intensity are not unambiguous for a specific safety level but also depends on the rain duration. Though, it seems hard to find a national standard for specific parameters within cloudburst mapping since the modeled areas are so diverse. Utredning kring val av varaktighet vid skyfallskarteringar / Investigation of the choice of rain duration’s impact on urban flood mapping