The ‘Climate-Proofing’ of Rotterdam


Credit: Joep Boute
Rotterdam panoramic view

Rotterdam, The Netherlands – How can a major seaport city thriftily bolster its defences against a growing onslaught of costly climate risks while reaping economic benefits and making itself more livable?

Rotterdam’s approach has been to start with a comprehensive risk-and-damage  assessment of long-term climate threats and then adopt a broad systems approach to improving its resiliency.

Adaptation measures are integrated into infrastructure projects and efforts are made to engage the business community. Along the way, the city has endeavoured to seize innovative, cost-effective opportunities to make itself more attractive, more prosperous, and more sustainable, even as it has wavered on its climate mitigation agenda. This has helped make the city’s pragmatic climate adaptation program more popular and has burnished the city’s international image.

Climate risks

Accessibility to the sea and navigable inland waterways are largely responsible for Rotterdam’s prosperity, but make the city especially vulnerable to rising seas and extreme weather. Situated on the Rhine-Meuse-Schelde river delta, densely populated Rotterdam is Europe’s lowest lying city. Parts of its delta lie nearly seven meters (23 feet) below sea level. The city – which is the Netherlands’ second largest – is thus exposed to water from the ocean, the Meuse River, groundwater, and rain.

As intense rainstorms become more frequent in a warming climate, the city’s current drainage system will not be able to cope with the prolonged downpours and higher peak river flows that climate change brings.

Heavy rains already often cause minor flooding. Unless something is done to prevent it, more serious flooding will eventually ensue. Rising seas and higher temperatures are thus a concern and an eventual threat to the city and its dikes.

Large parts of the city, and about 40,000 of its people, are located beyond the dikes and the city’s North Sea storm surge barrier. Tens of thousands of people also live close to the Meuse River. “Doing nothing is not an option,” says Arnoud Molenaar, the head of the city’s Climate-Proof Program and its Chief Resilience Officer.

Rotterdam’s Climate Proof Programme

Determining what is to be done, and how to do it, is the mission of Rotterdam’s Climate Proof Programme (RCP). Its fundamental goals are to make sure that the city stays safe, accessible, habitable, and attractive to residents and investors alike, despite the impacts of climate change.

Formally adopted by the city in 2008, the RCP is part of the more comprehensive Rotterdam Climate Initiative, which initially set out to reduce the city’s CO2 emissions by half by 2020 compared with 1990 levels. The city has since officially backed away from that goal, and its carbon emissions are rising now, rather than falling.

Having abandoned its original ambitious mitigation plans, Rotterdam is now focused on climate adaptation. It must eventually protect the city against a variety of risks. Besides wetter conditions and higher water levels, Rotterdam will also encounter more intense heat waves and more prolonged droughts that can put dangerous cracks in the city’s earthen dikes.

The European heat wave of 2003 took 1,000-2,200 lives in the Netherlands, according to an urban resilience planning report.1 Like most cities, Rotterdam is a “heat island” relative to its nonurban surroundings. Temperatures in Rotterdam have at times been as much as 7°C higher than nearby rural areas.

The RCP programme is thus set up to ensure the resilience of the city’s infrastructure and services while maximizing the economic co-benefits of its adaptation measures. This is what the city leaders mean when they say that the RCP will make Rotterdam fully “climate-proof” by 2025.

The Challenges Ahead

Credit: Roel Dukstra
Flood with submerged cars in Rotterdam

When sea level rises and when the city is deluged by sudden heavy downpours, Rotterdam will still need clean water and fuel supplies, sewers, waste collection, transportation, heat, and power, as well as its information and communication systems, so that essential public utility services remain available.

But protecting the city will not be an easy task: the city’s water purification plant, power plants, and railway lines are all outside the city’s diked core.

Rotterdam’s vast, heavily industrialized port—Europe’s largest by cargo volume—also will need to continue operating and remain accessible to the city, which itself will need to remain accessible by road and rail, so travel and commerce can continue.

The city has existed on the Meuse River since 1270 AD and for centuries has taken measures to protect itself against the sea and riverine, coastal, and rainfall flooding. Therefore, it has an extensive system of dikes, canals, outlets, sewers, pumping stations, and surge barriers.

The dikes around the city north of the Meuse are designed to protect against a once-in-10,000-year flood, while those to the south were built to a once in 4,000 year standard. Because of these high standards, Rotterdam and its port are commonly regarded as “one of the safest delta cities in the world.”

In fact, expert consultants advised the city in 2014 that “no direct strategic urban planning is needed to control current flood risk [emphasis added], like flood zoning or adaptive building. Measures can be taken on the level of the water system by placing dams in the canals after a breach.”1

The consultants noted, however, that by 2100, the current dikes will no longer be adequate because of expected sea-level rise. Continuing economic development and increased population density in the diked inner city will also raise the potential economic costs of flooding.

Climate change is also bringing more extreme weather that exacerbates marine and riverine flood risks, as well as the urban heat island effect (which affects residents’ health). For all these reasons, Rotterdam is working to strengthen its adaptive capacity.

Although the areas of Rotterdam beyond its outer dikes are three to five and a half meters above sea level, they are susceptible to flooding, which can cause costly damage and environmental risks from hazardous substances carried by floodwaters.

Utility corridors for the diked areas of the city permeate the large outer dike region, so flooding beyond the embankments currently can disrupt the inner city. If nothing were done, damage to buildings outside the diked area would be almost double current values by 2050—and triple by 2100.

Public Relations and Flood Protection

Credit: 500 Watt
Rotterdam’s skyline with Erasmus Bridge

Rotterdam officials recognize that the city’s primary dikes will need to be raised periodically to keep up with rising seas and that the city’s storm surge barrier – built after a major flood in 1953 – will only protect the city so long as sea level rise is less than half a meter.

While the city’s climate adaptation programme works with engineers and consultants on quantifying and minimizing flood risks, officials are also engaged in a vigorous public relations effort.

By taking highly visible adaptation measures to increase floodwater storage and retention (like the water plazas described below), officials seek to marshal public support for climate adaptation by demonstrating to their fellow citizens that such measures provide many economic and other benefits in addition to flood protection.

The city thus endeavors to link its adaptation measures to popular municipal ambitions and priorities, such as improving public health, creating new high-quality public spaces, and greening the city.

Officials are also consciously using their programme to project the city’s image as an innovative international leader in climate adaptation, with a view to garnering worldwide attention and attracting new business investment. Thus, it can be difficult to disentangle the programme’s glamorous public relations from its on-the-ground realities and residual risks.

Greening the city by planting trees, shrubs, and grasses and removing pavement can not only provide shade and attenuate the urban heat island effect, but it can simultaneously improve air quality, store carbon dioxide from the air, reduce noise, lessen wind speed, raise local property values, and increase stormwater infiltration and retention.

Greenbelts, parks, and ponds thus not only make the environment healthier and provide recreational benefits but also serve to make the city more climate-resilient. The city planted more than 6,000 trees between 2010 and 2014.

Also on the pragmatic side, the city is focusing on making sure that climate adaptation imperatives are considered during routine municipal operations. Thus Rotterdam, along with area water boards, is working on integrating climate adaptation concerns into its infrastructure maintenance programs and its spatial planning projects, according to Chief Resilience Officer Molenaar.

“All areas inside the dikes are protected against flooding,” Molenaar stated. He pointed out, however, that the area outside the dikes will have to become “climate adaptive by itself.” Those areas “are relatively safe,” he said, because of their higher elevations.

City officials, however, did not provide a simple overall summary of their current adaptation work schedule or adaptation budgets. It was therefore not feasible to assess the extent to which the city is likely to achieve its goal of becoming 100 percent climate-proof goal by 2025, nor quantitatively how much overall risk has been reduced to date.

A Systems Approach to Flood Protection

To protect infrastructure, services, and citizens through dikes alone would be prohibitively expensive and perhaps physically impossible. The city is not only strengthening its dikes, but it is also using innovative, smaller-scale measures that collectively provide the city with enhanced resilience.

Meanwhile, the city is mitigating the costs of diking by designing “multi-functional” dikes that might, for example, provide terraced space for roads, recreational corridors, commercial activity, or buildings.

To augment and make the infrastructure more resilient, the RCP programme started with a formal risk-and-damage assessment of the city’s vulnerabilities to climate change. It soon realized that to keep vital systems robust under new climate conditions, the city had to adopt a systems approach. Thus, it analyzed its water management systems as a whole and is continuously striving to identify new ways to relieve stress on the systems during periods of increased water flows.

Towards this end, the city is constructing numerous widely dispersed, small-scale water management projects. These include four public plazas, recessed below-grade, to store water; water infiltration zones; as well as planting trees and other vegetation.

The water plazas temporarily collect stormwater runoff from rooftops, parking lots, streets, and parks, providing water storage during heavy rainfall. During dry periods, the plazas serve as playgrounds or sport fields.

The city’s Benthemplein water plaza, built in 2013, is the world’s biggest, able to store 1,800 cubic meters of water. Large steel gutters fill three basins with water from roofs and the surrounding area during rainstorms until it can be safely discharged. The top of the Kruisplein garage near Rotterdam’s Central Station has also been equipped with water storage.

Other drainage projects have been completed at Bellamyplein, Kleinpolderplein, and. Frederiksplein. At Bellamyplein, water percolates beneath a green play area through porous lava stones into a below-ground concrete basin from which water can be gradually pumped out.

Kleinpolderplein combines a water square with an adjacent nature reserve that can overflow into the square, from which it can be gradually released. Frederiksplein, the city’s newest water plaza, is a playground in dry weather but captures heavy runoff when needed, which allows it slowly to infiltrate into the soil.

All these public works serve to hold or soak up water during extreme rainfall events and slow its release to protect Rotterdam’s sewer system from becoming overloaded and to prevent streets and other public areas from flooding. A city parking garage basement and several other underground facilities have also been equipped for storing water.

When new development projects in the city are reviewed by municipal authorities, they now consider future water management issues due to expected climate impacts, including runoff from impervious surfaces. City planners try to get businesses to help take responsibility for collecting and managing excess rainfall that falls on their property.

Green Roofs

Apart from reinforcing dikes and finding multiple uses for them, Rotterdam’s climate-proofing measures include the use of rooftop greenery. The city has many flat roofs and sees them as a resource for making buildings more climate-resilient, healthier, and more attractive once they are covered with soils and vegetation. “So far, we have developed 230,000 square meters of green roofs,” Molenaar reports.

“[They] are good for water storage, [and] also for air quality . . . and [to] give a green look to the city,” said Paula Verhoeven, the city’s climate initiative director.

By covering roofs with soil and plants that absorb rainwater, downpours have less impact on the city’s storm sewers and protect them from overloading. Green roofs also help insulate buildings, reducing need for space conditioning, while helping to improve air quality.

Green, tree-lined infiltration zones are also being installed along streets. These areas will increase biodiversity and make the city more pleasant and attractive. During times of heat stress, the trees will also make the city shadier and cooler.

A Coordinated Approach

Credit: Marijniz
Floating Pavilion in Rotterdam’s Rhine Harbour, comprised of three transparent half-spheres to deal with climate change-induced sea level rise.

The RCP’s objectives are not only to keep residents safe from flooding and to protect critical infrastructure, but also to maintain investors’ confidence in the city and region. A secondary but still important RCP goal is to minimize inconveniences to residents from too much or too little water.

The RCP uses a coordinated approach in its outer-dike area that includes spatial planning to raise ground elevations, dike reinforcements, and other design and retrofit measures, including rewiring lower floors of homes to make them more flood-resistant. The city is also studying the feasibility of building floating homes. And where needed, the city is making sure evacuation routes are adequate.

The RCI also is conducting public education to make the city’s businesses and inhabitants aware of the challenges of climate change, the actions they can take, and their responsibilities in times of crisis. As a last resort, citizens are being encouraged to be self-reliant during future climate-related emergencies.

In essence, the RCP’s overarching goal is to create a safe, high-quality living and working environment in a sustainable, prosperous city. Thus, planners intend to climate-proof the city in ways that will directly benefit its economy and make Rotterdam a role model for other cities around the world.

When major redevelopment of an area is necessary to improve its resilience to climate change, Rotterdam’s planners not only focus on water management but also look for ways to enhance public safety, public health, economic diversity, and a neighborhood’s attractiveness as a place to live and work.

Governance and Leadership

The city’s climate-proofing efforts are broadly based and include local, regional, and national government, three water boards, the port authority, and other entities. Implementation of the RCP is guided by the Rotterdam Climate Change Adaptation Strategy, which is managed by the city’s Office for Sustainability and Climate Change.

The leaders of the city’s climate-proofing effort radiate confidence in their ability to meet and surmount the challenges of climate change. A summary of the city’s Climate Change Adaptation Strategy asserts—hopefully correctly—“There is plenty of time to adapt to the changing climate.”

The programme’s standards are high: “Rotterdam must continue to be a city in which it is pleasant to live and work and where climate change does not adversely affect the health and welfare of its inhabitants,” the city’s strategy summary states.

The public pronouncements of the climate adaptation strategy are decidedly upbeat and ambitious. The programme’s descriptive literature even includes positive affirmations. “Rotterdam,” officials write, “is working to become a future-proof city that provides safety and is attractive to its inhabitants, visitors and businesses, both now and in the future. It is a safe, habitable city in the Dutch delta and it is a pleasure for people to work and live there.”

City officials, however, were short on details about how much the city was actually spending on its climate-proofing initiative and were unable to provide specific metrics to indicate how much the risk of flooding had been reduced to date and what risk would remain in 2025 when the city supposedly is “climate-proof.”

“We do not have exact numbers of the costs,” wrote Nick van Barneveld, the city’s senior adviser for water management and climate adaptation. “Our flood-related protection measures ([including] maintenance) cost billions of euros up to 2050 and 2100, which are politically chosen milestones. But sea level rise and soil subsidence are always present, so the work is never done/will never be completed.”

Referring to the question of flood risk, Barneveld said, “. . . purely looking at the flood-related issues: the whole city is ‘at risk’ because of its location in the delta. But the chance of flooding differs because of the protection of primary and secondary dike systems and/or differentiation in ground elevation in the unembanked [sic] areas.”

City officials recognize that collaboration across all levels of society will be needed if the city is to become truly climate-proof. Reflecting this, the motto of the city’s energetic climate-proof program is, “Working together for a climate-proof city.” Hopefully, the measures that Rotterdam puts in place will be equal to the challenges ahead.

Adapted from a five-part series on Rotterdam’s efforts to become a sustainable and “climate-proof” city.2

References

  1. Moel, H et al. Deliverable D4.5 Improved planning for urban resilience and sustainability – tools, measures and recommendations. TURAS [online] (2017). http://www.turas-cities.org/uploads/biblio/document/file/447/Deliverable....
  2. Berger, J. Rotterdam, Striving to be Green, Downplays CO2 Targets. Renewable Energy World [online] (April 21, 2017). http://www.renewableenergyworld.com/ugc/articles/2017/04/17/rotterdam-st....