Green-blue climate corridor Kamen - Disconnection of rainwater from sewage systems to prevent urban flooding

Published: 15 November 2016
Last edited: 01 October 2020
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The green-blue corridor project in Kamen, Germany was developed to improve the urban climate and restore the nature water supply in the area, thereby reducing flood risk. In conjunction with 2 km of ecologic improvement and stream restoration, rainwater from around 80 adjoining buildings and properties was diconnected from the sewage system. Residents were involved in the project and were responsible in some cases for the implementation of individual adaptation measures on their own properties.


West and South Europe
Scale of implementation
Freshwater ecosystems
River, stream
Urban ecosystem and build environment
Urban wetlands
Disaster risk reduction
Local actors
Outreach & communications
Urban planning
Watershed management
Erratic rainfall
Loss of Biodiversity
Ecosystem loss
Inefficient management of financial resources
Lack of public and decision maker’s awareness
Sustainable development goals
SDG 11 – Sustainable cities and communities
SDG 13 – Climate action
Aichi targets
Target 14: Ecosystem services
Target 15: Ecosystem restoration and resilience


Kamen, Germany


The Heerener Mühlbach was a canalized water body used as an open wastewater system, creating ecological and social challenges. The poor quality of the water in a concrete bed damaged local biodiversity, significantly reduced the ecosystem’s resilience and led especially in summer to a disturbing smell within the neighborhood. Extreme rainfall events became more frequent leading to flood events and endangering adjoining private and industrial properties. Finally, the physical form of the banks made it dangerous to use the area recreationally.


The residents of Kamen enjoy reduced flood risk, increased recreational opportunities and amenity values and improved microclimate offered by the restored corridor area. The area’s biodiversity also benefited from improved water quality and balance.

How do the building blocks interact?

The ecological improvement of the Heerener Mühlenbach brook by “Transforming the water body to nature-like banks” (BB3) in combination with the disconnection of storm water of the nearby paved areas is ready to make a significant contribution to weakening the potential impacts of climate change. If the effects of climate change do not come true as expected, the “Selection of no-regret adaptation measures” (BB2) will still allow for a number of benefits. Local inhabitants enjoy better living conditions with the recreational purposes the river now offers. “Engaging private citizens to implement adaptation measures” (BB1) is also a great opportunity to raise their general awareness of the water cycle and own responsibility for sustainable development. This was strongly supported by the “Communication strategy to increase understanding and support on flood prevention“ (BB4). At the level of the municipality, the city has become more attractive due to the ecological innovations. For the water board Lippeverband, such a no-regret measure is also a way to attain the EU Water Framework Directive, to reach better flood resilience and to allow for a more cost-effective water treatment.


The project achieved a long-term and cost-effective adaptation of the local water infrastructure, an improved microclimate, and increased ecosystem resilience. Pressure on the mixed canalization system and thus flood risk were significantly reduced during severe rainfall periods, while enabling the maintenance of water bodies during the summer. The diversification of rainwater into the naturally designed stream resulted in a restoration of the natural water supply and balances, support of diverse biotopes and increased amenity and recreational values for residents.


(c) Anke Althoff
The idea of “no-regret measures”: In view of the uncertainties of climate change, so-called no-regret measures were the solution: Most anticipatory options are not only beneficial for climate change adaptation but also for other sectors such as economic growth. Even if climate change impacts do not occur as expected, the measures will still be beneficial and cost-effective. According to the long-term rainfall measurements of the water board Lippeverband, no significant trend towards climate change could be observed. But it can also not be sure that rainfall will not increase. The ecological improvement of the stream in combination with the disconnection of storm water of the nearby paved areas is ready to make a significant contribution to weakening the impacts of potential climate change, no matter in which dimension this will happen. In case of more intense and frequent heavy rainfall, it reduces the flood risks since the water run-off is slowed down by means of meandering and infiltration through the natural bed and banks. Also, the ecological improvement and the sustainable use of rainwater can reduce floods because the sewer system does no longer have to cope with the same amount of rainwater. With rising temperatures in summer the water bodies tend to dry out. Due to the use of rainwater for the open water body the water cycle remains sound even in dry periods and evaporation creates a better micro- climate. While combining water management measures with green corridors, the climate in the urban surrounding is enhanced. Communication – a key to motivation Especially the storm water disconnection on the private grounds needed special communication. At the start of the project, inhabitants were not really aware of the coherences between climate change and their own property. A communication strategy to inform about the project and to motivate people for disconnection was set up in combination with an individual assistance. By the end of the project most of the property owners at the Heerener Mühlbach were aware of the need to adapt to climate change and understood how every individual can make his/her contribution. People were encouraged to take action for a better city climate and against climate change.

Contributed by

Anke Althoff Lippeverband

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