Cities and communities have often develped around waterways. Today, they play a vital role in adapting to climate change and strengthening social bonds.
Rivers are a key resource for food, directly through fishing or indirectly for irrigating crops. In the 19th century, when industrialization began, they became essential to run factories and revolutionize the economy, thus shaping the urban landscape. For that reason, humans have always established their settlements near rivers and have diverted their natural course to adapt to their needs.
However, as cities keep growing, rivers reclaim the space that they occupied. "Rivers are very complex ecosystems that raise a lot of questions in many areas: ecological, political and social," explains Paola Viganò, professor at the Laboratory of Urbanism, who for years has studied the integration of natural and urban environments. "River management requires not only technical solutions but also political agreement and alliances between different stakeholders."
The Rhône, from Valais to the Mediterranean Sea, for instance, is one of the rivers that has been transformed over the decades and has lost a significant fraction of its rich biodiversity. For that reason, several plans to restore part of the original river space have been under discussion for decades. Among other projects, the third correction of the Rhône in Switzerland combines flood protection along its course through the canton of Valais with elements to make the river more natural while improving safety and ecological functions. It involves widening parts of the riverbed and redesigning floodplains. According to Viganò, the way rivers have been domesticated has established a hierarchy between the big city and more marginal territories with a higher risk of floods: "The proximity to water sources is traditional, but the type of relationship and the risk are contemporary."
In the fight against climate change, every drop counts
Preserving not only the quantity but also the quality of water in rivers is essential to respond to climate change. "Many cities in Europe are exposed to heat stress. So each drop counts," says Viganò. According to the urbanism expert, designing future cities and neighborhoods does not involve only preparing them for the next flood. City councils need to find strategies to address the problems related to climate change rather than finding solutions for its consequences. "Climate change will create more extreme conditions. We need to understand that the risks are growing," says Viganò.
Sometimes, the risks that accumulate in the downstream areas of rivers originate way upstream. Viganò is particularly concerned about the population living in these areas. "Often, in the lower parts of the river you can find the most fragile population. This becomes a political problem of environmental justice," says the expert in urbanism. For her, territorial solidarity between upstream and downstream zones is key to understanding how the different parts of the valley can contribute to reducing flood risk. "In this regard, agriculture is fundamental but needs to be rethought in the modern context," says Viganò.
Adapting to climate change
The territory with all its different functions and characters needs to be resilient and contribute to reducing the risks. "To face these challenges, you need to bring together a lot of different types of people, from those that are working on transport to those that are working on biodiversity or on sports activities. Putting together all these actors is challenging. We need to prepare for that," says Viganò.
A closer relationship between nature and cities can help adapt to climate change in many ways. If cities contain more trees, there will be more shade, and they will help refresh urban spaces. At the same time, cities can help retain large quantities of water thanks to soil filtration or groundwater recharge. That is why cities can act as big water collectors. Based on this idea, the concept of sponge cities was born (see "Turning cities into sponges" on p.28). By using natural resources such as green spaces (green roofs, rain gardens) and permeable pavements to absorb excess rainwater, sponge cities can not only help mitigate flooding but also enhance the relationship between urban and natural environments.
Many cities in Europe are exposed to heat stress. So each drop counts.
The privilege of swimming in Swiss rivers
Some cities are finding strategies to guarantee healthy rivers. For instance, the Seine in Paris was partially reconditioned for the 2024 Olympic Games as part of efforts to reduce sewage overflow, microplastics and bacteria. On the other hand, thanks to legislation established forty years ago, Switzerland is one of the rare places where people can swim in urban rivers. As summers become warmer, more and more people use rivers to refresh on hot days or even to commute, as happens in the cities of Bern or Basel. "It is a spectacle when you pass by some Swiss rivers and lakes and see so many people enjoying themselves. We have to realize this is not possible in many places in Europe," says Viganò.
Social dimensions
Today, rivers are very important spaces, crucial for inhabiting cities responsibly and supporting climate adaptation. To restore our relationship with water, both visually and practically, citizens need to remain socially connected to water. Viganò calls for "a new way of reframing the concept of cities," where water can be a driver for more egalitarian cities. Viganò warns that interpreting water as a kind of resource one can claim will lead to significant conflicts in the future: "We need to listen to water. If we accept how water behaves and its interdependencies, it can certainly help build more democratic societies."
Research and sustainable energy meet at Chamberonne
Just a few steps from the EPFL campus lies one of the best examples of how a river can be integrated into an urban environment. Running through both the UNIL and EPFL campuses, the Chamberonne river is formed by two parent rivers, the Sorge and the Mèbre, which cross the western side of Lausanne before converging and continuing their journey toward Lake Geneva.
Flowing through forests, agricultural land and urban landscapes, this watercourse tells a story of environmental change, water innovation. This proximity to the city also comes with challenges. Urban growth has gradually influenced the river's water quality, with aging hydraulic infrastructures and increasing sources of pollution that affect the river's ecosystem.
But all these factors make of the Chamberonne a living laboratory for research, education and environmental monitoring. Thanks to its accessibility to the EPFL campus, the Chamberonne offers unique opportunities to study the influence of human activities on aquatic systems. For instance, in the framework of the UrbanTwins project, the research group led by EPFL professor Rizlan Bernier-Latmani, from the Environmental Microbiology Laboratory, installed sensors along the Sorge to monitor the river and assess the impact of the campus environment on water quality.
The proximity to these sources of water also provides a place to build sustainable infrastructures that heat and cool the campus. Since 1978, Lake Geneva has been the main source of cooling for the Lausanne campus, with water pumped from the lake and distributed through an underground network. In 1986, the installation of heat pumps also enabled the recovery of thermal energy from the lake for use in heating buildings.
Over the years, the infrastructure has evolved significantly, and renovation work enabled EPFL to become entirely oil-free by 2022, reducing its carbon emissions by around 1,400 tons of CO2 per year. Today, more than 85% of the energy used for heating and cooling the buildings on the campus comes from renewable sources, including the campus' 2 MW data center, which is cooled with water from the lake, while the heat produced by its servers is recovered and reused to heat the university buildings.
The EPFL's heating and cooling plant, with its distinctive red blocks covered in solar panels, has become a landmark of the area and a symbol of innovation and sustainability.
