Between Grande-Motte and Grau-du-Roi, the pass des abîmes silted up and closed little by little

En décembre, période où le Vidourle est pourtant le plus haut, une langue de sable non loin du pont.

Entre Gard et Hérault, la passe des abîmes se bouche inexorablement avec le sable déposé par la mer.

Residents of the Etang du Ponant in La Grande-Motte are worried. Will the pretty residences lined with pine trees soon be the neighbors of a swamp ? The regular silting of the Passe des Abîmes, this corridor which allows the Vidourle to flow into the sea, and marks thus the separation between La Grande-Motte and Le Grau-du-Roi, or between Hérault and Gard, does not seem a priori the subject of anyone… Or perhaps of too many people for an action efficient. Symadrem, joint union of the Rhône Delta, EPTB of Vidourle, the public basin establishment, Water Agency, Dréal ? Agglo du Pays de l&#39 ;Gold or rather Terre de Camargue ? New agreement for the bay of Aigues-Mortes chaired by Stéphan Rossignol, the mayor of Grand-Motto ?

"We launched a petition, which collected more than a thousand signatures" says Bernard Aubert, the president of the association of residents of the Ponant who, although she is delighted with regular relations with local elected officials, nevertheless wonders who manages the sand which accumulates in this place ? "These Sedimentary contributions are not without consequences, they modify the ecosystem: in the Ponant pond, the sea enters. #39;the whole point of the lagoons is this great diversity of species. Our pond must absolutely remain open to the sea!, insists Bernard Aubert.

Bernard Aubert chairs the Ponant residents' association. Midi Libre – E.L.

The former engineer, member of the Academy of Sciences and Letters of Montpellier, is as interested in history as in geography, and that of the coastline, is closely watched by the association he chairs. Aerial photos show the evolution of sandy deposits which do not date from yesterday…

The pass of the abysses marks the separation between Le Grau-du-Roi and La Grande-Motte, between Gard and Hérault. Midi Libre – E.L.

"If we consult the portolans, these ancient nautical charts, we see that in the 10th century, there were marshes here and boats are well advised to be wary sandy arrows! The crusader ships, which had a large draft, left here, from the tip of La Grande-Motte. Canoe boats shuttled between the shallow water port of Aigues-Mortes and the anchorage at sea. The coastline of Grande-Motte has not changed since the Middle Ages", continues Bernard Aubert who evokes this fairly deep geological fault of the abysses.

Tensions with the Boucanet campsite

The owner of the Boucanet campsite, which suffers from the onslaught of the sea in the event of a swell, found himself in danger. in disagreement with the town hall of Grau-du-Roi as well as with Symadrem (which manages the Gemapi competence, flood protection). Remove around thirty of its bungalows (out of 450) as suggested; by communities was unthinkable for the owner who owns 215 campsites in France, including several in coastal areas. The situation became tense when the campsite wanted to relocate to the campsite. its costs of the ganivelles removed by the Mediterranean episode of last October. However, the beach belongs to the public maritime domain, the threat of a fine for this intervention was raised. brandie. Since then, relations have calmed down.

The Vidourle, a capricious river

"The Mediterranean and its absence of tide has this particularity: the sediments at the outlet of a river are deposited there in the shape of a ;#39;crossbow. This is true of the Nile, the Po, the Elbe and therefore of our Vidourle."   

The pond was created artificially during the creation of the Grand-Mottoise station.

The Racine Mission, during the creation of La Grande-Motte and Port-Camargue a little over fifty years ago, led to the creation of the pond. The course of the Vidourle, a particularly capricious river (during the 2002 flood, its flow rate reached that of the Rhône, i.e. 3,000 m3 per second) has been artificialized since the 19th century.

The Vidourle outlet before the root mission, then in 2005 and in 2018. Association of residents of Ponant

Before the creation of the Ponant, the 80 km long river with its 1,000 meter drop flowed into the Etang de l'Or. Since then, the river has arrived… at a right angle. Depending on the wind, the level of the pond can drop by more than a meter and on the contrary it can fill up if the storm comes from the south. low water, where evaporation is at its maximum, salinity rises: 33 grams per liter at the outlet of the grau. At the end of January, it drops to 20 g per liter. 

The pond, of artificial origin, is a biosphere reserve. Midi Libre – E.L.

"At La Grande-Motte, we are at a point of balance on the coastal plateau. To conserve the sand of the Boucanet and prevent it from accumulating in the pass, we must act at the risk of seeing all the biodiversity degrade. Act yes, but who and when ? 

Recommended dredging operation

Who should manage the pass of the abyss ? Asked the State services to recognize everything makes the problem: "In the absence of significant flooding of the Vidourle since 2014, this pass is essentially silted up by the sea, along the Gard bank of Grau-du-Roi." The narrow navigation channel along the dike on the side& oacute; of La Grande-Motte poses "increasing passage difficulties for fishermen and boaters". State services also relate to "this situation accelerates the confinement of the pond, which can induce periods of anoxia in the summer period water (absence of oxygen) by proliferation of algae along the banks of the shallow areas towards the Vidourle." The Dreal (regional directorate for the Environment, Development and Housing) recalls having given the authorization to Grau-du-Roi in 2020 to dredge & the mechanical excavator a small part of the silted area to re-sand the Boucanet beach (which was not done) but estimates also that in the absence of the Vidourle flood, "dredging greater in volume could prove to be unnecessary. necessary or more regular maintenance dredging of the pass. The State considers here that it is the area of ​​competence of EPTB Vidourle.

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