Case study

Rotterdam - NbS for building a waterproof city

Trees floating on colourful planters in the tidal park in Rotterdam.

Objective:

Rotterdam aims to be 100 % climate-proof by 2025. This is the goal expressed in the city’s climate change adaptation programme. This means that by 2025 measures will already have been taken to ensure that each specific area is minimally disrupted by climate change both then and throughout the following decades. Furthermore, all urban planning in Rotterdam will take into account long-term foreseeable climate change while allowing for contingencies.

The ‘waterproof city’ is robust and resilient with a mix of paving and vegetation. The focus is on adaptive measures whereby rainwater is captured and drainage is delayed.

The Dutch government is also preparing for the consequences of the rising sea level, land subsidence and rising temperatures with a combination of infrastructure works (e.g. dikes) and building with nature (restoring ecosystems in flood areas — the tidal park programme). These actions are included in the annual Delta Programme.

Financing:

The Ecorys study shows that making Rotterdam climate-proof will require investment of EUR 4 to 5 billion (2010). Benefits, such as economic development, better spatial planning, nature, safety and lower insurance costs are being studied at present. The study results are expected to be published in 2018.

Actions:

Water storage capacity

The changing climate will lead to more frequent extreme rainfall and heavier downpours. This will increase the risk of disruption and damage caused by flooding, particularly in areas that already have a water storage capacity deficit and densely built-up, paved urban areas. The drainage and storage capacity of the urban water system is being adapted to deal with extreme rainfall. The ‘sponge function’ of the city will be restored by taking measures to capture and store rainwater where it falls and to delay drainage. These measures include green roofs and façades, less paving and more vegetation in public streets and neighbourhoods, water squares and infiltration zones as infrastructure. These measures will be especially effective in highly populated, built-up areas with little open space.

Delta plan

The main priority in outer-dike Rotterdam is multi-layered flood protection based on adaptive construction and design: e.g. ‘flood-proof’ buildings, 'flood-proof' public areas, floating communities and ‘building with nature’. Special attention is being paid to the port and essential infrastructure, which are well protected from flooding. The protection of inner-dike Rotterdam focuses on prevention. Storm surge barriers will be optimised and dikes reinforced as needed and made multifunctional, to merge into the city as e.g. recreational routes, natural embankments or as part of new development.

Tidal park programme (Esch, Mallegat)

Climate change adaptation can easily be combined with improving the ecology of the city. More water and vegetation, ‘greening’ the city, will make it more resilient in periods of extreme rainfall or drought. In the tidal park programme, several outer-dike areas are being developed with alternatives to solid constructions to prevent flooding at high water levels. In this way various wetland-related ecosystem services are being restored: water storage, water flow regulation, and water filtration. Green banks improve the quality of the water, make it easier to enjoy these areas and improve ecological connectivity.

In parts of the city where there is more space, increasing the water storage capacity of canals and lakes and constructing green-blue corridors will significantly contribute to making the city climate-proof. This green-blue adaptation of the city is a ‘no regrets’ measure — one that will help make the city climate-proof and make it a more attractive and pleasant place in which to live.

Lessons learnt:

  • Working together: partners in climate change adaptation should include municipal services, other government departments such as the water boards and Rijkswaterstaat, the citizens of Rotterdam and private organisations such as housing corporations, project developers, utilities and the Port of Rotterdam.
  • The implementation approach is not a blueprint listing measures to be implemented in each area. However, it does give an indication of the priorities.
  • Implementation is in tune with the ‘rhythm of the city’: renovation or replacement of buildings and infrastructure occurs on average every thirty to fifty years. This timeframe is fine to adapt to climate change.
  • The implementation is area-specific: specific measures have to be developed for specific areas in the city.
  • Rotterdam has more than 130 000 m2 green roofs.

Contacts:

Paul Ramjiawansingh, senior projectleider, Havensteder, Rotterdam, The Netherlands

Nick van Barneveld, senior beleidsadviseur water, City of Rotterdam, The Netherlands

Nienke Maas, senior adviseur Gebiedsontwikkeling, TNO, Den Haag, The Netherlands

Impacts:

Rotterdam’s climate change adaptation programme is not focused solely on the use of nature-based solutions but combines ‘grey’ solutions with green and blue solutions.

The city is addressing heavy rainfall threats. It has built water storage spaces, including the Museum Park car park underground water store with a capacity of 10 000 m3, and is integrating ‘blue-green corridors’ into the urban landscape. These blue-green corridors — watercourses and ponding areas — are designed to facilitate natural hydrological processes such as groundwater replenishment whilst minimising urban flooding, enhancing biodiversity and improving the city’s quality of life. Rotterdam has also installed over 130 000 m2 of green roofs. Finally, the drainage capacity of the system is being increased through above-ground drainage of rainwater. All these measures are leading to decreased drainage peaks.

Investment in flood protection and water security has broad local support. Protection against flooding in urban deltas has improved.

The Netherlands is a successful participant in various international programmes. There is increased awareness and political support for ‘water diplomacy’ and climate change adaptation.

Future actions as part of the Delta Plan are shifting from ‘grey’ to ‘green’ infrastructure (including nature restoration), making increasing use of nature-based solutions.

Multiple benefits:

Water storage capacity

The combination of grey and green solutions has proven capable of regulating water flow and mitigating runoff by reducing flood peaks and reducing the risk of flooding by flash-floods. A secondary effect is increased availability of groundwater. While in the city centre primary actions are focused on grey solutions and green roofs, measures on the outskirts of the city are focused more and more on green corridors and a combination of nature restoration and flood prevention. This helps connect structure and function in the city landscape. Local ecological restoration has a direct impact on biodiversity, increasing the richness and composition of species of indigenous vegetation. Another indirect effect is increased carbon sequestration in those areas. The availability of green and blue areas has a positive effect on evapotranspiration, which has cooling effect, so reducing heat stress in the city. The increased number of green spaces in the city not only has health benefits (less stress, better mental health) but also provides access to recreation areas. At the same time, it diverts recreation from sensitive biodiverse areas. The city’s efforts to promote green roofs support energy efficiency, as buildings are better insulated, and have a (small) effect on temperature in the city.

The delta plan

While the main aim of the delta plan is flood risk reduction, the measures taken have a direct impact on water retention capacity and an indirect impact on cost in terms of the lower load on the sewage system. The increased infiltration has a positive effect on the restoration of ecosystems. These measures are leading to increased flood regulation. The delta plan is shifting toward greater use of nature-based solutions, creating green and blue corridors resulting in greater landscape connectivity. It also creates additional high-value nature areas, with the secondary benefit of increased carbon storage capacity. Due to the increased evapotranspiration, those newly created habitats also reduce heat stress. The creation of high-value nature areas also has a positive effect on health and improves air quality.

Tidal park programme (Esch, Mallegat)

The flood areas of Esch and Mallegat combine flood risk reduction and related costs, increased water infiltration, and increased flood regulation with ecological restoration, creating greater connectivity through the creation of green and blue corridors in the city. The creation of high-value nature in the flood areas increases biodiversity and landscape connectivity. This will increase storage of carbon and evapotranspiration, resulting in less heat stress. The creation of green and blue corridors can be combined with the creation of new recreational areas, giving inhabitants the possibility of using them for sports and leisure activities. This will have a positive effect on their health. Bike paths can be used for public transport, reducing the use of energy for transport. The improved air quality in the region will have a positive effect on the heath of people living close to or passing through the area.

Integration:

Nature-based solutions have been incorporated into a number of city plans and strategies: Investing in sustainable growth; Rotterdam climate city: mitigation action programme; and the climate change adaptation programme Rotterdam Climate Proof (RCP). Several EU projects have contributed to these city plans and strategies (ECODISTR-ICT, TURAS), providing an insight into the vulnerability of the city, the threats to its functioning and the specific work that must be carried out.

Stakeholder Participation/Participatory Planning and Governance:

There are already many green urban initiatives in progress, each in their own way encouraging people to play an active part in making the city more attractive and to improve the environment. Examples include urban farms on (temporarily) unused plots in the city, collective gardens and the construction of wilderness playgrounds and child-friendly districts.

Potential for new economic opportunities and green jobs in the EU and in global markets:

Rotterdam is home to many businesses that operate internationally in the maritime service, hydraulic engineering and delta technology sectors. It is estimated that 3 600 jobs in the construction industry, in consultancy offices and in ICT are currently directly related to climate change adaptation. Rotterdam has always been a showcase and testing ground for innovative adaptive measures and hopes to remain so in the future. Many companies active in the maritime sector are increasingly taking nature-based solutions into account when developing climate change-related solutions.

Universities and colleges and the regional authorities have always played an important role in exporting knowhow ‘made in Rotterdam’. Rotterdam cooperates with other delta cities via networks such as C40 and Connecting Delta Cities. Dozens of international delegations visit Rotterdam each year to learn about the city’s approach to climate change.

Success and Limiting Factors:

In order to play a significant role in global competition among urban regions, the city’s spatial development strategy has two main goals: to be an attractive residential city, and to build a strong economy. Nature contributes greatly to a city’s attractiveness. This is why Rotterdam has applied nature-based solutions to its climate-related challenges. The adoption of nature-based solutions by the large maritime sector partly explains the fast and increasing implementation of nature-based solutions in Rotterdam.

Drivers:

Rotterdam is located in the delta of the rivers Rhine and Maas. The city has open links to the sea and is influenced by the tide. Much of Rotterdam, including the main port, lies in outer-dike areas. The inner city is mostly well below sea level. If the region were to flood, the consequences would be disastrous. In 2008, the City Council of Rotterdam ratified the Rotterdam Climate Proof programme, which has three main activities: development of knowledge, implementation of climate change adaptation measures and presenting Rotterdam internationally as an innovative delta city. Devising an adaptation strategy is a vital step in creating a climate proof Rotterdam.

Rotterdam is working with neighbouring communities (Metropolitan Region Rotterdam), with the most important cities in the Netherlands (G4: Den Haag, Rotterdam, Utrecht, and Amsterdam), and with major European cities (ICLEI — Local Governments for Sustainability; the European Climate Adaptation Platform — the European Environment Agency). Worldwide it is participating with other cities in the C40 Cities Climate Leadership Group. It participates in several European programmes including FP7 (ECODISTR-ICT, TURAS, BASE), Horizon 2020 (FOSTERREG, BINGO), and the European Environment Agency (Climate-ADAPT).

Monitoring and evaluation:

No dedicated monitoring or evaluation system is currently in place to understand if NbS initiatives are successful.

Impacts of EU research and innovation projects:

As part of the Rotterdam Climate Proof climate change adaptation programme, the Knowledge for Climate programme has carried out extensive research into how climate change will affect Rotterdam and what the consequences will be. Within the Delta Programme, considerable knowledge has also been developed concerning the Rijnmond-Drechtsteden region. The EU-funded projects ECODISTR-ICT and TURAS have contributed in the field of flood prevention, urban heat islands and the use of nature-based solutions (green roofs) in the renovation of social (subsidised) renting districts. In the Rotterdam Climate Change Adaptation Strategy, this knowledge is being applied to describe climate change effects, the consequences for Rotterdam and the risks that the city must take into account. Much of this information has been included in the newly developed Rotterdam interactive climate atlas.

Further information: