The effects of climate change are already manifesting themselves in the dense and urbanized coastal city of Marseille. Due to its characteristic Mediterranean climate (hot and dry summers and cool and wet winters), Marseille is vulnerable to heatwaves, drought, fires, acute rains and storms [pdf]. Scientists forecast that with climate change, extreme weather events will increase in both frequency and intensity [pdf]. Marseille will have to grow into an adaptable and resilient city to preserve its water resources.
To most, water in the «Rhône-Méditerranée» appears abundant. The population of Marseille proudly claim they have the best water of France. The Durance and the Verdon rivers are the principal sources of the city’s water. The canals of Marseille and Provence transport water to Marseille.
Research reveals an absence of flood risk awareness in Marseille. This finding is surprising if we take into account the upsurge in flooding episodes due to increasing urban planning and soil impermeability (as pictured).
Marseille regularly experiences excess rainwater runoff after heavy rain due to its dense industrial and urban landscape. Concrete, tar and other impermeable surfaces prevent rainwater from infiltrating the soil. Fifty-five percent of rain collects as runoffs in urban areas, compared to 10% in natural areas.
Most rainwater is mixed into the wastewater system, which concentrates rainwater and overwhelms the system in heavy rains. The Géolide plant treats 60% of the city’s wastewater, but it rejects excess water into the environment when it is overwhelmed. A large retention basin was commissioned to collect excess water.
Excess runoffs threatens residents, increases maintenance costs and harms the environment. Municipalities regularly close beaches due to runoff.
Marseille’s drainage system is not suited for climate change. Urban planners and water managers are working to retain water in the city using floodable sports fields, permeable parking, and green roundabouts.
Bottom Line: Marseille’s drainage system is not suited for climate change and the extreme rains it brings. Instead of building expensive, inflexible retention basins, the city should work to increase infiltration everywhere.
* Please help my Water Scarcity students by commenting on unclear analysis, alternative perspectives, better data sources, or maybe just saying something nice 🙂