Implications of Long-Term Oscillations in Rainfall Extremes on Urban Drainage Design Practices

In the last decade damaging floods have affected many European and major Danish cities including Copenhagen. As a result, the concept of integrated resilient water management came in the political agenda for developing climate adaptation plans required for all Danish municipalities. An emerging area within the climate change debate addresses the quantification of natural climatic variations. Recent studies have shown profound multidecadal oscillations in extreme rainfall over Europe including Denmark. The present study focuses specifically on the variation of historical design values for urban drainage design in Denmark. It showed that historical design values exhibit a similar pattern of variation. The analysis also covered Danish and European legislation on water management, concluding that the main directives on protection of the aquatic environment were adopted during periods of few extreme events. This illustrates the importance of the natural variation as a driver for the development of urban design practice and ranks it alongside technological and scientific advances. Therefore it is highly relevant to incorporate the knowledge of the natural variation in the resilient water management concept and future research strategies.