“Before water rose, but left faster”, how this forgotten practice makes it possible to fight against floods

This is one of the ways to fight floods: maintain watercourses. This task most often is the responsibility of the owners of the plots bordering the rivers, but this practice tends to get lost and is not without consequences during flood episodes.

Philippe Boehmler, Charolais breeder in Forstfeld (Bas-Rhin) keeps a traumatic memory. In May 2024, most of its plots were overwhelmed by waters after torrential rains. The manager: La Sauer, a river bordering its fields.

“On the lower parts, there were up to 1.20 meters of water” recalls the farmer. “The meadow was really defiled, there were no more herbs for animals that had to graze. And the harvest for winter was of poor quality” Add the one who lost € 180,000 in turnover in just a few days.

Cultivated corn was completely destroyed by the flood. The farmer was never able to harvest his plots drowned by waters.

Many residents are unaware of it, but the maintenance of non -domanial rivers is the owners of the plots they line. But the practice would have been lost believes the farmer. “In the past ten years, tIt is ancient to tell us that flows worse than before. Before, the water rose, but left faster ” Described the one who counted a hundred hits (heaps of dead wood) over the fifteen kilometers of rivers around his town.

The rule indeed wants that non-domanial rivers are maintained by the owners residents themselves up to half the shore. If the watercourse crosses a property, this is the sole owner that this responsibility returns.

In France, 95 % of the banks are private. THE Environment Code therefore requires owners to ensure the free movement of water, in order to prevent the risk of flooding.

Maintenance consists in regularly withdrawing the debris which hinders the flow of water, such as dead branches or detritus, and pruning the trees likely to fall on the banks. However, the SDEA (Water and Sanitation Union Alsace-Moselle) stresses that it should not be done any way.

Only dead woods that completely block the circulation of water should be removed. Those located near the banks must be left in place because they serve as a refuge for biodiversity. In addition, these interventions must be carried out outside the reproduction periods of fish and birds.

In the absence of maintenance, communities are sometimes forced to act in place of the owners. This is the case of the SDEA which intervenes when the security of the populations is threatened.“We replace the owners who lack their duty, but only if it is for the general interest” explains Vincent Moitrier, head of water management and aquatic environments at the SDEA.

In 2024 alone, its teams intervened 500 times in place of the owners residents, about a third more than in 2023.

We observe a tendency to abandon by the owners residents.

Vincent Moitrier, head of the management of water and aquatic environments SDEA

“There can be many owners along rivers. And the successions make that sometimes we lose knowledge of the plots. We therefore observe a tendency to abandon maintenance by the resident owners”finally sums up Vincent Moitrier. In 2023, these operations cost € 380,000 to the Water Syndicat. Funded by a new tax, the GEMAPI, to management of aquatic environments and the prevention of floods.

All owners contribute to it, whether or not they are residents of a watercourse, according to the principle of financial solidarity. On average, this represents € 7.50 per year per inhabitant, but can reach up to € 40 in certain communities of municipalities.

The Eurometropolis of Strasbourg has chosen, for the moment, not to charge this tax. This is not the case with Mulhouse Métropole or Colmar Agglomeration.