Limiting flooding in Bouvignes, nature as a first solution?

Limiting flooding in Bouvignes, nature as a first solution?
Limiting flooding in Bouvignes, nature as a first solution?

What if the damage from the Bouvignes floods in 2021 could have been limited? Underground experts maintain that nature could have mitigated these disastrous consequences.

On July 24, 2021, intense precipitation hit the heights of Onhaye and Dinant, on the left bank of the Meuse. The village of Bouvignes, located below, suffered the consequences. Runoff water from the upper basins rushes down and carries away everything in its path. Georges Michel, coordinator of the Walloon Commission for the Study and Protection of Underground Sites, briefly discusses the reasons for the episode:

All the water that falls on this basin with an area of ​​several square kilometers must pass through a narrowing which corresponds to the end of the funnel. All this runoff flows into Bouvignes, in a very tight valley. We then witness a flood wave which arrives suddenly.

If this flash flood phenomenon could not have been avoided, the disastrous consequences could have been limited. These underground experts surveyed the valley and identified strategic areas to monitor. This is the case of an ancient cave, hidden under the rock. Jean-Benoit Schram, vice-president of the commission, regrets that it is not used correctly.

At one time this cave was fourteen meters deep. It was blocked by the municipality in the 1970s. However, it made it possible to recover water from the entire plateau located above. In 2021, this would have saved a few hundred cubic meters from flooding.

Fortunately, everything was not blocked. The Rostenne chantoir, for example, was able to do its job. A sort of natural storm basin, this chasm can absorb an enormous quantity of water. Georges Michel adds:

It is a chance. In the Bouvignes catchment area, there are a certain number of water infiltration points. They are saving compared to the problem of a flood wave.

A natural absorption system?

These karst phenomena, which are the caves or the chantoir, are proof that nature could save Bouvignes from water in the future. But for that, they must be cleared and arranged.

Some adjustments must be made in certain places to be certain that the water flows are directed towards the karst. For example, we could create a small drain. But it is also necessary to be certain that this system adequately absorbs water by having cleared the natural conduits.

The latest floods were exceptional, even if the phenomenon has already occurred in Bouvignes several times in the past.

We should also review, at some point, the entire land use planning policy, avoiding building in areas that are at risk. It may seem paradoxical to say that an area where there is no water is in a flood zone, but this is the case in Bouvignes with runoff water. We must also work on the scale of the entire basin to encourage infiltration and limit impervious areas due to massive cultivation or massive urbanization.

From nature comes one of the solutions to flooding, it is up to man to anticipate it well. For the management of the basins, the municipalities of Onhaye and Dinant will certainly have to collaborate to avoid a new disaster.

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