Evaluating Flood Risk Reduction by Urban Blue-Green Infrastructure Using Insurance Data

Abstract:
One of many important features of blue-green infrastructure is the ability to lower flood risks by detention of stormwater. This ability of flood risk reduction has for the first time been evaluated with empirical data in this study. In 2014, Malmö, Sweden, was hit with extreme precipitation corresponding to a return period of 50–200 years that led to severe pluvial flooding. This and other large events presented the opportunity to evaluate the efficiency of the 15-year-old stormwater system retrofit in the Augustenborg area (30 ha). Blue- green infrastructure is widely promoted for climate change adaptation, making this unique case important in the discussion of the capabilities of the related technical solutions. The long-term trends showed less flood damage in Augustenborg than in similar neighborhoods that have conventional sewer systems (combined or separate), indicating a direct effect of the retrofit with stormwater control measures. Even though a few properties were flooded in Augustenborg, it was shown that the retrofitted stormwater system performed successfully during the extreme event in 2014.