Multifunctional Land Use in Urban Spaces to Adapt Urban Infrastructure

Abstract

The research project presented here is an evaluation of problems arising from global warming, increasing stormwater intensities, demographic changes and migration in highly industrialized regions. 1D/2D simulations are used to show the advantages of water sensitive urban design (WSUD) strategies using the MIKE URBAN Flood Software (Danish Hydraulic Institute, DHI, Copenhagen, Denmark). Two regions in the Ruhr area, Germany, were analysed in order to illustrate the advantages of WSUD. More and more frequently, rainwater after an extreme rainfall event cannot be drained by the existing sewer system [DWA (2010) DWA-Themenheft, Klimawandel–Herausforderungen und Lösungsansätze für die deutsche Wasserwirtschaft”, Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e. V., DWA, Hennef] and flooding of urban city centres occurs. One reason why the central sewer system fails to absorb the rainwater is the increased load in the sewers due to a higher discharge of wastewater. More frequent extreme rainfall events due to climate change will worsen the situation [Gerstengarbe F (2009) Klimawandel in Ballungsräumen: Das Beispiel Ruhrgebiet, Bildungszentrum für die Entsorgungs- und Wasserwirtschaft GmbH]. That rainfall characteristics have already started to change is shown by numerous flash flood events all over Europe [Castro D, Einfalt T, Frerichs S, Friedeheim K, Hatzfeld F, Kubik A, Mittelstädt R, Müller M, Seltmann J, Wagner A (2008) Prediction and management of flash floods in urban areas in Germany (URBAS). Final Report, Federal Ministry of Education and Research, Bonn]. Although such events will occur more frequently in Germany in the future, the extension of sewage systems is not financeable. Therefore, decentralized infiltration and storage devices should be introduced to reduce runoff. Additionally, the directed discharge of stormwater runoff across the surface in an urban catchment is required. Within a city, streets and squares could be flooded in order to protect buildings and urban infrastructure. Additionally, the directed discharge into decentralized storage structures is useful to limit the negative effects of flooding. The required storage capacity needs to be integrated in the environment. It has been shown that the directed flooding of public parks or public squares is a useful measure to adapt urban infrastructure to the consequences of climate change.