Résumé
Urban rivers are highly disturbed ecosystems. Indeed, urban rivers have been dammed and sometimes buried. The aim was to reduce the risk of flooding and solve health problems due to water pollution. In the mid-20th century, many cities have turned banks into parking. Cities and rivers were therefore separated due to urban development. Since the 1960s and 1970s, the water policy was to build or upgrade the wastewater treatment plants and water treatment plants. In Europe and North America, however, the legislation has evolved over the last fifteen years for increased and overall protection of aquatic ecosystems. The hydromorphological river restoration is now a priority of the new water policy in Europe. This is why cities are experimenting with today's renaturation projects of urban rivers: both territorial marketing and sustainable development. This article defines the concept of renaturation. The paper also presents two case studies: Quebec in Canada and Lyon in France to evaluate the advantages and limitations of this concept.