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A flood and heat proof green Emscher valley, Germany (2015)

A flood and heat proof green Emscher valley, Germany

Over a century ago a sparsely populated landscape of water meadows was transformed into an industrial conurbation, and the untamed river Emscher turned into a man-made system of open waste waterways. Due to ongoing subsidence caused by mining, it was impossible to build an underground sewer system. Therefore, the Emscher and its tributaries were regulated and used to transport the wastewater together with rainwater on the surface. This made the Emscher simply a great open wastewater channel. With the decline in the mining industry, traditional heavy industry gave way to the services and high-tech industries.

In the 1990s restoration of the 82 km stretch of river in a catchment of 865 square kilometres began, gradually creating the New Emscher Valley taking into account challenges of climate change. In future, wastewater will be channelled through closed sewers and the river and its tributaries will be converted into nature-like waterways. Gradually being developed, the valley will comprise cooling green spaces, areas for flood control, recreation areas and a habitat network, therefore enhancing quality of life in the Ruhr metropolitan area under future climate conditions. Taking an integrated and holistic approach, by strengthening the green infrastructure network and changing the water management, the Emscher Valley will have an improved capacity as carbon sink, a more favourable microclimate, reduced flood risks in case of heavy rainfall events and a more balanced water cycle in times of dry summer periods.


Case Study Description


During the 20th century the Emscher was used mainly to quickly and completely drain all the area’s wastewater. This resulted in extreme fluctuations in the amounts of water discharged. Following a downpour, up to 350 cubic meters per second of water would flow through the Emscher, in contrast during dry periods just 11 cubic meters per second of water would trickle through this polluted waterway. Considering climate change projection more extremes can be expected.

Indeed, according to long-range climate projections, the Emscher area will develop more wet and moderate winters, along with more frequent extreme winds and storms. Summers will be hot and with recurring events of extreme rainfall. These climatic changes will leave lasting effects upon the socio-economic conditions of the population, upon security, and upon the region’s productivity and competitiveness. More in detail, the following climate change challenges are expected for the area:

  • Increase of extreme rainfall events: more often and more severe. Climate change will double the events of extreme rainfall. Data from 1961-1990 show rainfall events with more than 40 mm/d to occur about 2 times per year. The projections for similar events for the years 2021-2015 is about 5 times per year and for the years 2071-2100 even more than 5 times. The annual mean precipitation will increase by about 9% by 2050. Together with rising temperature the rainfall events will become more severe, because the warmer atmosphere can accumulate more humidity.
  • Increase of temperature: more hot days, less cold days. Ove the recent 50 years, the average air temperature has shown an increase of 1°C. For the future, the annual mean temperature is expected to increase of another 1,6 degrees by 2050, and about 2,9 degrees by 2100. Not only will the average temperature rise, also extremes will be more common with more days with temperatures higher than 30 degrees. By 2050, 50% more hot days, and by 2100 about 100% more hot days are expected to occur. This will cause heat stress, especially for the aging human population in the Ruhr area. Cold days with frost and ice will decrease by about 50% by 2050 and by about 80% by 2100.
  • Impacts on ground water: less in summer and higher in winter. In summer, higher temperatures are expected to result in a lower ground water recharge rate. In winter, with more precipitation, the level of ground water is expected to rise. This will increase the possibility of floods. Specifically, if no sustainable storm water management is implemented, the areas with flood risk will increase by about 20% in the close future.
  • Impacts on ecosystems. The above described climate changes will have impacts on ecosystem such as water bodies, wetlands and woodlands. Especially water bodies are sensitive: low water levels in summer will raise the level of nutrients and pollutants, extreme rainfall will cause erosion at the river banks and a higher temperature will lower the level of oxygen in water.

To prepare for future climatic conditions, a traditional approach would make use of grey engineering with technical solutions such as building higher dikes and bigger sewers or enhancement of pumping stations. The Emschergenossenschaft, the water management association responsible for Emscher, has decided for a more flexible nature-based solution. Choice was made for combining the channelling of the wastewater from the Emscher and its tributaries into closed sewers, with revitalization of the rivers aiming to strengthen the water cycle and profit from the water buffering as well as from cooling provided by nature’s ecosystem services. In short, the main adaptation objectives are:

  • For summer: creating the green corridors of the Emscher landscape park for cooling, as well as creating a resilient water system thereby avoiding the drying-out of brooks and rivers.
  • For winter: increasing the retention capacity of the water bodies in order to avoid flooding in case of heavy rainfalls.

A traditional solution in response to the expected water discharge needs would be the construction of a sewer system that can cope with expected variation in water amounts. With the Emscher project a more transitional approach was taken strengthening the water cycle by converting the river and its tributaries into nature-like waterways and by having waste water channelled through closed sewers. Gradually being developed, the valley will comprise cooling green spaces, areas for flood control, recreation areas and a habitat network, therefore enhancing quality of life in the Ruhr metropolitan. Nature-like water bodies have a higher capacity to buffer extreme weather events. In case of heavy rainfall, a nature-like water body has a 10% higher retention capacity than a heavily modified water body. The green belts accompanying the Emscher and its tributaries work as fresh air supply corridors for the dense urban areas. Wetlands and areas for storm water retention cool down heat islands. The living quality for people rises, heat stress is reduced, and new cycle paths along the water bodies provide possibilities for sustainable mobility. The overall approach taken is to integrate water management and urban planning for a water sensitive urban development.

Before projects such as dynaklim and Future Cities started, each actor in the Emscher region developed its own adaptation strategy. For example, the water boards analysed whether their sustainable water management was fit to cope with expected impacts of climate change. Cities assessed their building stock and discussed which improvements would be needed in response to the heat island effect. Further, the Regional Association Ruhr (Regionalverband Ruhr) fostered their measurements of urban temperatures. With the support of these two projects a cross-sectoral approach was developed, including all relevant stakeholders such as: water management, planning, building, health sector and emergency service ones. For example, in addressing climate change and the future availability of water, the dynaklim network elaborated a “Roadmap 2020”. This roadmap is a cross-sectoral framework of reference for a future, regional adaptation strategy that coordinates goals and activities of regional administration, politics, economy and society, identifies and coordinates priorities with relevant regional actors and structures them in terms of timing.

In addition, being a partner in the Future Cities project, the Emscher case served as an example to develop strategies to make city regions fit to cope with the expected impacts of climate change. Within the project the joint tool “Future Cities Adaptation Compass” was developed to help city regions to create their own adaptation strategy. This tool fostered very much an interdisciplinary approach to reach cross-sectoral solutions.

An example of an outcome of the Future Cities project is the sustainable development of two climate-proof industrial parks in Bottrop, in the Emscher region. Flash floods after heavy rainfalls often occurred on both sites. This situation is expected to be intensified with climate change. The Emschergenossenschaft and the Bottrop municipality agreed on a cooperation to restructure the industrial parks "Scharnhölzstraße" and "Boytal", thereby combining water, green and energy measures to make them climate-proof.

The “Scharnhölzstraße” is an old business-site with almost completely sealed surface. On the site, heavy rains tend to cause problems as well as overheating during periods of drought. A combined approach was taken for the public space on the one hand and the privately owned premises of the industry on the other hand. Decentralized solutions for rainwater (rainwater infiltration and rainwater use, solar power usage and green-zone enrichment) were envisaged to strengthen the area for upcoming climate events.

The industrial park “Boytal” drained the rainwater into an open ditch which ended in a nearby lake. There was no existing overflow from the lake into a natural body but only into the mixed sewer system. The aim is to disconnect the whole industrial park from the system. As this will take place in the context of the ecological transformation of the river Boye, a new blue-green corridor will be realised in this area.

Although the Emscher system is already well prepared, torrential rainfall events will still cause severe flooding from time to time. Therefore, it remains necessary to plan and implement rainwater retention to improve preparedness. One example has been the planning and construction of Lake Phönix in Dortmund (supported by funding within the Urban Water project) which will be able to absorb up to 240,000 cubic meter of floodwater from the river Emscher. Another example for reducing high water flows is the goal that has been set with the “Future Convention for Stormwater” of reducing inflows of rainwater and clean water into the waste water system by 15 percent within 15 years, from 2005 to 2020.


Case developed and implemented and partially funded as a CCA measure.

Additional Details

Stakeholder Participation

The dynaklim group, established within the dynaklim project, includes more than 50 network partners: companies involved in the regional economy, water boards, municipalities, universities and research facilities, as well as regional and civil society initiatives. Together, they have drawn up a joint regional climate adaptation strategy. The dynaklim network has set up a constant exchange of new knowledge and practical experiences between the project partners and with the public. The design of the network and strategy is meant to ensure that once the adaptation process has been initiated and the funding has stopped it will nevertheless be continued by the region on a self-sustaining basis. Similarly, several actions were defined during the Future Cities project and were set-up with the aim to see continuation after the ending of the project.

A number of initiatives were initiated to ensure durability to the above projects, possibly including stakeholder engagement:

  • The former annual meetings of the dynaklim project are continued by the DWA (Deutschen Vereinigung für Wasserwirtschaft, Abwasser und Abfalland) project partners.
  • Some measures were integrated in the “Klimaschutzplan” in the dynaklim project, an adaptation regulation of the North Rhine-Westphalian government.
  • The dynaklim Roadmap 2020 entitles the responsible organisations for the adaptation process and stipulates the organisations realised during the project stage to continue the needed actions.
  • The use of the Future Cities Adaptation Compass in the city of Dortmund includes wide stakeholder participation. The process started with a stakeholder analyses to make sure that no relevant actor is left out.

Other relevant stakeholder participation activities are:

  • In case of restoring water courses of the Emscher system, the residents are involved in the planning and implementation in a broad information and participation process.
  • Regarding sustainable storm water management the people in the Emscher region are informed in detail about how they can be involved including an internet platform.
  • Specifically regarding extreme rainfall events an information campaign was started within the Future Cities project. The campaign is based on the internet platform.

The watersheds of the Emscher and the adjacent Lippe face similar challenges of climate change. The two water boards, the Emschergenossenschaft and the Lippeverband, have therefore together developed measures for water management.

Success and Limiting Factors

After more than 20 years of planning and implementation, the New Emscher Valley has gone from a purely envisioned ideal to a reality that has inspired new urban development. The modernisation of wastewater infrastructure and associated revitalisation of the Emscher are making the river a valuable space for leisure and relaxation in the region. An integrated perspective on nature and technology shows that the Emscher can be perceived as far more than just an ecosystem. People can now again experience the Emscher, which was once inaccessible to the public due to high levels of pollution. The revitalisation of the Emscher and discharge of wastewater into underground canals has freed up new spaces for innovation above ground, making the Emscher region more attractive. Ecological, social and institutional innovation will be needed to develop these new spaces. Hence, the Emscher conversion is not only a technological project but also framed as an important trigger for notably improving the quality of life and achieving positive economic impacts in the Ruhr area. By reusing and preserving the impressive relics of the industrial era, the Ruhr region has been able to keep its unique identity and has re-branded itself as an ancient monument of industrial society.

The main limiting factor is space. In a densely populated region such as the Emscher region with 2.700 people per square kilometre it is very hard to find space for a meandering river system. The competing demands on space are manifold: economic, social and ecological aspects have to be weighed up against each other. In addition, public authorities can only approve plans based on valid regulations. However, there are no rules that specify dimensions of sewers or dikes with uncertain increases of rainfall for the next 50-100 years.

Costs and Benefits

With an investment volume of 4.5 billion Euros and a project period of several decades, i.e. from 1989 (start of the International Building Exhibition IBA Emscherpark) to 2020, the Emscher conversion is one of Europe’s biggest infrastructure projects. Investments of this size have noticeable impact on a region’s economy. Through the Emscher revitalisation about 1400 jobs per year are created in the years from 1991 to 2020 (cf. study from Rheinisch-Westfälisches Institut für Wirtschaftsforschung, November 2013). The conversion project’s significance extends well beyond its direct effects on employment though. Upgrading the Emscher region will provide a new quality of life and work and bring with it great opportunities to sustainably improve the Ruhr area’s attractiveness. Thus, it will influence positively the decisions of innovation-oriented companies considering moving or starting up in the region. The successful conversion of such a large river system also sends a positive signal for similar large-scale water management and urban development projects throughout Europe.

Considering the challenges of climate adaptation, it is hardly possible to name the costs involved if choice would not have been made to restore the Emscher but to implement higher dikes and bigger sewers. In addition to that it would cost a fortune to provide a purely technical protection system, this would never be 100% proof considering that no-one knows exactly how extreme the next rainfall event will be.

The Emscher Landscape Park was mainly funded by the State Government of North-Rhine Westphalia (NRW), especially from the Ministry of Environment and the Ministry of Urban Development. In addition to the state support, co-financing of EU money especially through objective 2-funding made up part of the financing structure. During the period of the IBA (International Building Exhibition), there were extra funding options; the funding programme ÖPEL (Ökologieprogramm Emscher Lippe) was set up, which still exists today. The Emscher revitalisation is paid through the members of the Emschergenossenschaft, which are municipalities, the mining industry and private parties. Further, best use has been made of several funds: from the federal land NRW, national funding such as KLIMZUG, and EU-funding such as objective 2, INTERREG, FP7 and HORIZON2020, LIFE+. Wherever possible, support from private parties, local businesses and NGOs such as the Emscherfreunde is welcomed.

Implementation Time

The Emscher revitalization started in 1992. The construction of underground sewers takes 15-20 years (end expected by 2017), the ecological enhancement 25-30 years (end by 2020); 123 km (on 326 km) of water bodies have been revitalized (March 2015).

Life Time

The revitalization of the Emscher system will be long lasting.

Reference Information


Emschergenossenschaft / Lippeverband
Office of the board of management
Mario Sommerhäuser, head of office
Tel.: +49 0201 1042564

Martina Oldengott
Tel.: +49 0201 1042223


Emschergenossenschaft / Lippeverband
Department of strategic river basin management
Ekkehard Pfeiffer, head of department
Tel.: +49 0201 1043279

Anke Althoff
Tel.: +49 0201 1042361

EEA Study “Examples and case studies of synergies between adaptation and mitigation and between incremental and transitional approaches in urban areas”; original source: Emschergenossenschaft / Lippeverband.

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