Climate change impact assessment on urban rainfall extremes and urban drainage: methodologies en difficulties

Cities became since last decades more vulnerable to flooding because urban drainage infrastructure has been built at large scale, but also due to climate change. The number of quantitative assessment studies of the impact of climate change on urban drainage remains, however, rather limited. This is partly because of the particular difficulties when dealing with this type of impact. First problem is that the results of climate models need be downscaled to very small space and time resolutions (e.g. catchments of few kilometers, time scales as low as 5 minutes). The impact results consequently are highly uncertain, a problem that becomes more challenging since the properties of extremes do not automatically reflect those of average precipitation. This paper gives a state-of-the-art overview of the methodologies and results of climate change impact assessment on urban rainfall extremes and on urban hydrology and hydraulics. The several difficulties and uncertainty sources are being discussed, as well as the challenges in dealing with the urban hydrological climate change impact assessment and responses.status: publishe