Urban flooding has become a major issue throughout Europe, especially with the prevalence of intense rainstorms and overflowing rivers. The traditional urban drainage and concrete defenses that protected against floods are now struggling to keep up with rising tides and climate change. Cities throughout Europe have begun to turn to nature-based solutions – weaving parks, ponds, and gardens into urban infrastructure to help soak up rainwater and reduce the risks of flooding. By blending engineering with ecology, these cities have been increasingly able to manage the growing flood threat.
Nature-based solutions (NBS) use natural landscapes to address environmental challenges. Instead of piping rainwater away, NBS implementations in cities like Rotterdam in the Netherlands, aims to “turn the city into a sponge” that absorbs and stores water. These can include creating open spaces – like parks and plazas – that flood temporarily, using green roofs and walls to catch runoff, and creating or restoring wetlands to act as reservoirs during intense rain. These solutions serve to mitigate the effects of heavy rainfall while integrating greenery that decorates the existing urban landscape. Restoring natural waterways and incorporating permeable pavements and soils into existing and future urban infrastructures can also help to curb the effects of flooding with high payoff. For instance, studies conducted on the effects of restoring floodplains show that for every euro invested in restoration, four euros are avoided in damages. These solutions serve a dual purpose: managing water and improving urban life. European cities implementing NBS are planning ahead, redesigning cityscapes to work with natural water cycles instead of against them.
Spanish cities have taken great strides in promoting nature-based solutions as preventative flood measures. In Madrid, an urban project transformed a section of highway into a prolific green urban park along the Manzanares River that spans an area over 7.5 kilometers. This Madrid Río project provided the city with lawns, trees, bike paths, and playgrounds which all sit over giant stormwater containers that collect excess water, prevent overflow from potential flood events, and even help cool the city during intense heat waves. This park has become one of Madrid’s most popular spots and serves to bring the nearby community together. However, the project cost about 4 billion euros and faced skepticism and political pressure at its outset. Madrid provides a great example of integrating a flexible flood buffer – a green riverpark that can soak up stormwater and return to hosting picnics and soccer games.
With climate change bringing heavier downpours, cities are finding new ways to adapt beyond barriers and surge barriers. As a Dutch port city, Rotterdam has embraced a shift in perspective – living with the water by making the urban landscape itself part of the solution. Under its “Rotterdam Climate Proof” program, the city has spent roughly 100 million euros on climate adaptation, pioneering innovative measures to manage excess rainfall. In 2013, Rotterdam opened Benthemplein Water Square, a public plaza that can retain almost 2 million liters of rainwater when heavy rains hit. Benthemplein fills up like a pond and gradually drains after the storm, a concept so successful that it has since been adapted in cities worldwide. Rotterdam has also tested out multi-use water storage systems, other blue-green schoolyards and parks, dual-purpose waterways, green roofs, and floating architecture to combat sea-level rise. Rotterdam’s success with all of these innovative techniques has attracted attention around the globe, from New York to Tokyo. For cities, especially those like Rotterdam that are below sea-level, Rotterdam’s innovations may provide key insights to keep cities dry and afloat.
Europe’s densest major city, Paris, has relatively few natural areas, increasing the impact of oscillating heat waves and major flooding. In response, Paris is pursuing a greening strategy, including the Paris Climate Action Plan and the “Soil & Rainwater Plan”, which plan to adapt the urban environment to better handle water. This includes ridding the city of excess asphalt, planting more trees, and mandating green roofs on new buildings. They have also developed initiatives like the “Oasis schoolyards” program, which adds green spaces and gardens to schools in order to reduce runoff and increase permeability and water storage. Paris has primarily sought to add parks, urban forests, and green roofs into the urban landscape, infusing nature wherever possible. The city has sought to make the green infrastructure a legal requirement and guide new projects to include NBS and biodiversity considerations. Paris’ developments help demonstrate how developed and populated cities can adapt to flooding or climate change concerns through implementation of NBS initiatives to contribute to a safer, more sustainable urban landscape.
Nature-based urban flood solutions come with major barriers to implementation, the first of which is funding. Green infrastructure often requires significant up-front investment, and while it may be cheaper in the long run, finding the money initially can be difficult. Madrid’s project cost about €4 billion, and even smaller projects like Rotterdam’s water squares or Paris’s schoolyard greenery need steady financing. Cities may be able to seek EU funds, climate resilience grants, or public-private partnerships to fund these sustainable ventures. Some cities are even exploring innovative funding solutions — charging new development fees to fund flood mitigation parks or using insurance savings to invest in nature-based features.
Another challenge is finding space in dense cities where urban land is expensive and contested. Converting a street into a bioswale or a parking lot into a pond may face harsh resistance. It takes political courage and community support to reclaim land for NBS projects. Strong leadership and public engagement are crucial to overcoming the short-term disruptions that the construction of these projects can bring. By informing the public on the benefits of NBS projects, they may be more willing to take on the costs and inconveniences associated with their implementation.
Cities must also ensure equity in climate adaptation, given the risk that creating green amenities will inadvertently fuel “green gentrification”, raising property values and pushing out lower-income residents. This has been observed in North American and European cities where new parks have led to higher rents in surrounding areas. To counter this, planners in major cities strive to distribute nature-based projects to all neighborhoods, alongside affordable housing policies. Combining this with community involvement — such as Rotterdam co-designing water squares with local students and church members — can help ensure projects meet local needs and that residents welcome the change. The implementation of these nature-based solutions must be administered equitably to ensure that the benefits of these greener streets are not merely shared among the affluent.
Some other general considerations are maintenance, performance, and large-scale implementation into urban design. When implementing these solutions, cities must budget for long-term care just as they would for pipes and pumps. Trees grow and die, parks need maintenance, and bioswales can clog if not maintained. There is also a learning curve in city agencies which will only improve as more cities embark on NBS projects, providing more data to validate their effectiveness and provide insights into the best strategies for efficient implementation and upkeep. Even cities such as Valencia — which undertook NBS projects but continues to face flooding concerns — provide key opportunities to learn from and improve these sustainable urban practices. Additionally, to truly counter escalating flood risks, these approaches must move from small isolated demonstrations to standard practice in urban design. Collective action must be taken to successfully integrate these projects through a coordinated strategy to maximize impact and benefits systemically.
European cities have a choice to make: reinforce their fortress mentality with higher barriers and larger sewers, or reinvent themselves to align with nature. The cases above help portray what the latter path can achieve — beautifying cities, improving health, and bringing people together. Going forward, city leaders should incorporate the lessons from these pioneers, incorporating new developments or renovations into urban infrastructure — whether a small park or permeable parking lane. Ambitious targets help set the intention, but clear policies and incentives are necessary to achieve them. Cities may start by updating zoning and building codes but should also include larger-scale planning, collaborating beyond city limits — restoring upstream wetlands for instance — to effectively reduce flooding. The EU and national governments can accelerate progress by funding innovation and implementation within nature-based solutions and facilitating knowledge exchange.
The implementation of these solutions are more robust than some may realize and provide quantifiable benefits as we factor in the severity of the global climate crisis. A recent European Commission study found that combinations of NBS measures could help Europe maintain future flood impacts at today’s levels even under a 3°C warming scenario. Investing in resilience helps avoid disaster losses and results in additional benefits like tourism, recreation, and improved public health. It is also important to make the distinction in sustainable design that grey and green infrastructure are complements. Smart cities will utilize hybrid solutions, pairing grey infrastructure such as a necessary stormwater tunnel or a seawall with green infrastructure such as new parks or restored wetlands. Tying these practices together can help protect cities from floods and diversify the urban landscape in ways that bring unparalleled improvements to cities.
All in all, the battle against urban flooding in Europe is creating a new type of city. A city with tree-lined streets, plazas that welcome water, and rivers reconnected to their floodplains. A city that treats nature as an ally to be woven into its fabric. From Madrid’s revitalized Manzanares to Rotterdam’s sponge-like neighborhoods and Paris’s green schoolyards, we are seeing the blueprint of how to build flood-resilient cities that are also healthier, happier places to live. European cities should continue to scale up these nature-based solutions, sharing successes and learning from setbacks. As climate pressures mount, the choice is clear: embrace nature as part of urban infrastructure, or risk being overwhelmed by future storms. The water will come one way or another – better to work with it, than to fight a losing battle against it.
Featured/Headline Image Caption and Citation: Floods in Bosnia and Herzegovina, Image sourced from Flickr | CC License, no changes made