Significant climate change of extreme rainfall in Denmark

During recent years, practitioners of urban drainage have complained that, they felt that surcharging occurred more frequently. Therefore, a study was initiated focussing on the variations in extreme rainfall during the last two decades. In Denmark, a total of 41 rain gauges with a high resolution in time and volume have an observation period close to 20 years. The rainfall observed at these gauges was selected for this study. Three variables were analysed for statistically significant trends during the observation period: Maximum average 10 min intensity, maximum average 6 h intensity and the total volume of individual rain events. For the 10 min maximum intensity there is a statistically significant trend towards more extreme and more frequently occurring rain storms. The trend is pronounced in the eastern part of the country and below statistically significant levels in the western part of the country. For the 6 h maximum intensity and total volume of events the trends are less pronounced. The findings are confirmed by comparison to physically based climate models and studies based on large regions.