Heavy rain hits Mediterranean region

Recent heavy rainfall in the Mediterranean region has led to significant flooding, particularly in the northwest of the Bouches-du-Rhône department. Rainfall accumulations reached 200 to 400 mm in just 36 hours, with even higher amounts recorded in some local areas.

Flooding disrupts infrastructure and livelihoods

The flooding has rendered roads, cities, and villages unusable, putting crops and livestock at risk and forcing businesses to close. The affected area includes the Arles to Bouc canal and the Vigueirat, which together form a watershed of 900 km², representing a fifth of the Bouches-du-Rhône department.

Limited drainage capacity exacerbates the problem

This area has only one outlet at its southern end, in the Port-de-Bouc / Fos-sur-Mer area, regulated by the anti-salt barrage managed by the Marseille major port. Another hydraulic structure at La Roubine du Roy in Arles allows overflow of water from the Vigueirat into the Rhône when the Rhône's level is low.

Expert highlights drainage bottlenecks

Pierre Raviol, president of the mixed interregional syndicate for the development of the Rhône delta and the sea (Symadrem), and also a municipal councilor of Arles in charge of risk management and hydraulics, explained that the Arles to Bouc canal can discharge up to 100 m³/s during a flood, but the anti-salt barrage only allows 40 m³/s to pass, creating a bottleneck.

Proposed solutions for improved drainage

Raviol noted that the port's pumping station has nine pumps, but only one is used for industry, and the other eight could have been used to drain floodwater. He suggested the installation of Archimedes screws at the foot of the salt barrage to remove water more efficiently during heavy rainfall events.

Canal maintenance not the main issue

Raviol also addressed concerns about the maintenance of canals and ditches by the authorized syndical associations (Asa), stating that the canals in the Arles marshes that manage the Vigueirat are well maintained and that the issue is not their maintenance.

Climate change challenges flood management

He emphasized that these canals, some of which were designed centuries ago, are essential for agriculture and irrigation. However, he acknowledged that the system was built to handle rainfall accumulations of up to 100 mm, and that with climate change, the same amount of rain is falling over shorter periods with more intense episodes.

Collaboration needed for future resilience

Raviol concluded that canal managers must collaborate to adapt and improve the situation to continue farming in the area.