Hydrological challenges in urban areas

Urbanization alters hydrological processes and is often associated with increasing flood risks, which threaten human wellbeing and social and economic development. The conventional paradigm of flood protection relying on structural measures based on hard engineering solutions (e.g., dams, piped systems) has proven insufficient to mitigate floods. Sustainable water management, including solutions to enhance natural processes within urban areas, is a promising approach to enhance flood resilience and address the multiple sustainability challenges faced by cities. However, implementation of solutions based on mimicking natural processes has been slow. Mainstreaming of urban sustainable flood management is inhibited by governance aspects (e.g., limited collaborative governance), and knowledge gaps on effectiveness compared with conventional engineering approaches. The increasing flood hazards driven by growing urban populations and climate change projections of increasing frequency and intensity of large precipitation events demand improvements in spatial planning. This also provides opportunities for sustainable water management mainstreaming in order to complement the relatively limited drainage capacity of conventional systems.