Climate change leads to more extreme rainfall in The Netherlands, such as more frequent and more intense rainfall events. In some urban areas, like several Dutch historical city centers, this can lead to pluvial flooding and polluting combined sewer overflows. In this report, these challenges are investigated by research for design, and urban landscape design solutions are explored and applied on the basis of the urban acupuncture theory and the rhizomatic approach. The design is applied to the historical city center of Deventer, a city of 100.000 inhabitants in the East of The Netherlands.
A multitude of different rainwater interventions was investigated, and an applicable set of design guidelines is presented to accelerate future design projects dealing with similar challenges. Furthermore, the most vulnerable areas within the neighborhood are explored by investigating (1) the current sewer system, (2) surface water flows and accumulations during heavy rainfall events, and (3) existing pluvial flooding models. In the end, a site-specific landscape design dealing with pluvial flooding and polluting sewer overflows for the historical city center of Deventer is presented. The final design is a suggestion and a source of inspiration on how the threat of more regular pluvial flooding and combined sewer overflows can be addressed in a historical city center.
It was found that urban rainwater interventions make it possible to prevent pluvial flooding and reduce polluting sewer overflows during 1 in 10 year precipitation events in a historical Dutch city center. However, it should be questioned whether the implementation of the required intervention type and size is also desirable. Furthermore, this research and design shows that climate change adaptation should not just be seen as risk limitation, but can also be an opportunity for cities to become greener, healthier, more biodiverse and more pleasant living environments.