top of page
image00016.jpeg

The Tidal Bore

  • A notable phenomenon on 66 rivers in the world including 2 in France, the Dordogne and to a lesser extent the Garonne

  • The Dordogne tidal bore, the 15th largest tidal bore in the world

  • The site of the barge, where the tidal bore is strongest thanks to 5 km of straight line

  • A phenomenon observable 8 months a year

  • Up to 200 tidal bores per year in a dry year

  • Waves of 1.5 to 2 meters moving between 20 and 30 km/h

The best observation site
in France of the Tidal Bore

A unique phenomenon and present in a notable way (surfable) on only 66 rivers in the World including 2 in France: the Dordogne and to a lesser extent the Garonne. The Bore of the Dordogne is considered one of the 15 strongest Bore in the world. Contrary to popular belief, a phenomenon that is observed for 8 months in the year from May to December as soon as the tidal coefficient exceeds 75/80 associated with normal rainfall and this at a rate of 2 passages per day (at each rising tide). It can occur up to 200 bores per year during dry years. The lower the flow of the river and the higher the tidal index, the bigger the wave.

Thanks to nearly 5 km of straight line (Canadairs refueling corridor) between the Asques bend and that of Saint Pardon, the wave takes all its power at the site which constitutes as such the best observation point in France of the Tidal Bore.

Aerial view of the Péniche du Mascaret site
09-avec-localisation-GB.jpg

© A. Colas / Thalassa FRANCE 3

Le Mascaret: À propos

Video (© Koprod.fr ) of the Tidal Bore on September 19, 2024 with a coefficient of 115. Note: the winter of 2023/24 saw exceptional rainfall in Bordeaux, making the tidal bore invisible in the spring (first tidal bores in June) and less strong thereafter compared to previous years.

The Tidal Bore Phenomenon

The phenomenon of the Tidal Bore corresponds to a sudden rise in the water of a river or an estuary , caused by the wave of the rising tide, provided that the estuary is shallow and the difference in level between the ocean, the estuary and the river is very small (which is the case on the Dordogne, with only a 15- metre difference in level between Royan and Libourne).

A series of waves then forms at the mouth of the Gironde (from Bec d'Ambès) which goes up the river for nearly 70 km to Vignonet well after Libourne
. The phenomenon was present on the Seine until the 1960s (it disappeared following the developments made to the river, damming and modification of the estuary).

Only the Dordogne (and to a lesser extent the Garonne) remains where it can be observed in France in any significant way. And it is precisely in the towns of Saint Germain de la Rivière and Izon , which face each other on either side of the river, that the wave is strongest (and not in Saint Pardon as is usually written, but the port of St Pardon remains the only possible observatory for the public). The wave moves between 20 and 30 kilometers per hour and regularly reaches 1.5 to 2 meters high.

Site

Aerial view of the Tidal Bore

The site was chosen to be the cover of the reference book on the Mascaret written by Antony COLAS: Mascaret l'onde lunaire Édition YEP (2014)

Avec-localisation-GB.jpg

© A. Colas / Thalassa FRANCE 3

The Péniche tidal bore!
by Antony Colas*

Antony COLAS

Site

*Antony COLAS is a French surfer. Cited as a great specialist of the tidal bore, he is also the author of the guides of the trilogy of "Guides Stormrider World", a sort of guide of the Routard for surfers, sold in more than 200,000 copies worldwide. Originally from Biscarosse, it is on the Basque coast and more precisely in Anglet that he settled. He is also the author of the book Mascaret, l'onde lune (Where he references the tidal bores of the world). But it is to him that we owe the referencing of the tidal bores of Asia. To write and especially illustrate his book, he surfed each of the tidal bores mentioned. From that of the Quiantang river in China, to the Pororoca in Brazil, via Petitcodiac in Canada, the Severn bore(en) in England or more recently in Mozambique and of course that of the Dordogne.

Mesdames et Messieurs !
 

Le mascaret de la Péniche du Mascaret est une production 100 % naturelle. Un miracle de Dame Nature, né de la rencontre entre deux forces hydrauliques dévastatrices. D’abord, celle de la marée, initiée au milieu de l’océan, à plus de 100 km vers l’Ouest. Ensuite, celle du courant de la rivière, qui démarre à la source à plus de 400 km à l’Est. Et c’est précisément ici sur cette immense ligne droite de plus de 4 Km où stationne la péniche que ce face à face aquatique va provoquer les turbulences les plus fortes de ce phénomène dont le nom est né ici dans le Bordelais : j’ai nommé le Mascaret !

 

Pour bien comprendre le phénomène qu’il faut absolument une fois dans sa vie voir ET entendre, Il y a quelques notions à assimiler pour ressentir cette formidable rencontre. Rien de bien compliqué, il suffit de lire !

 

D’abord, parlons timing ! Comme en gare SNCF, le passage du train de vagues va être ponctuel...ou presque ! Cette heure est le résultat complexe de la Grande Horlogerie que sont la genèse de la marée et sa propagation dans l’Estuaire de la Gironde puis dans la rivière Dordogne. Mais cette heure est bien calculable pour les siècles et les millénaires à venir, c’est le phénomène naturel le plus prévisible qui soit.
 

Lors des périodes de grandes marées, que l’on appelle aussi marées de vives-eaux, la renverse du courant de rivière se produit toujours dans les mêmes plages horaires, c’est-à-dire entre 4h et 7h le matin et soir, entre 16h30 et 19h30 le soir. C’est comme ça ! Cette répétition horaire est intimement liée aux cycles de la lune. Cela dit, l’heure précise de passage du Mascaret, peut varier de quelques minutes, parfois jusqu’à 15 minutes, car la propagation de la Marée dans la rivière, peut être ralentie ou accélérée, en fonction : de la force et la direction du vent, de la pression atmosphérique et du débit d’eau de la rivière. Ainsi donc, un fort vent marin, souvent accompagné d’une pression basse, c’est à dire inférieure à 1000 Hectopascals va accélérer le processus tandis qu’un anticyclone de 1030 Hp par exemple avec des  vents faibles va le ralentir.

Screen Shot 02-01-25 at 04.32 PM.JPG

Je vous propose donc de venir sur la Péniche du Mascaret pour parier sur l’heure de passage exacte, pour tenter de gagner une bonne bouteille de vin. Une cloche viendra retentir lorsque la première vague viendra percuter la proue de la Péniche. Celui ou celle dont l’horaire sera la plus proche sera déclaré vainqueur ! Faites vos jeux, rien ne va plus !

 

Avant que vous ne proposiez un horaire de passage, même au pif ! Permettez-moi de continuer à vous expliquer quelques rudiments sur l’événement à venir. Commençons par un peu d’astrophysique ! Qui sait ce qu’est-une syzygie ? Probablement, pas grand monde ! La Syzigie, S-Y-Z-Y-G-I-E, oui 2 Y et 1 Z, si vous jouez au scrabble, je vous le recommande, est le mot qui signifie l’alignement des astres, à savoir la Terre, la Lune...et le Soleil.

 

Quand ces 3 astres sont alignés, les forces de gravitation, celles qui font que je ne m’envole pas quand je saute, la gravitation terrestre !  font que les masses de la lune et du Soleil tirent sur les masses d’eau océaniques et qu’un petit bourrelet se forme à la surface de l’Océan. En fait, pas un bourrelet mais deux, diamétralement opposé, un dans l’hémisphère sud, un dans l’hémisphère nord. Bref, ce bourrelet va se propager avec la rotation de la Terre et surtout s’amplifier quand cette déformation de la surface de l’eau va rentrer dans les Golfes, les baies et les estuaires !

Passage of the Tidal Bore filmed from the barge on September 20, 2024 with a coefficient of 112

Crazy, I tell you, since the ocean ridge that does not exceed 50 cm in the middle of the ocean, will end up being several meters and up to 18 meters in the Bay of Fundy in Canada where the tides are the strongest in the world. At low tide, it is said that you can come and walk on the ocean floor.

 

This is how the tides in the North Atlantic, which is not the case everywhere, reach amplitudes of several metres and in the Bay of Biscay, when the tide passes the Pointe de Grave between Royan and Le Verdon sur Mer, this tide has a spring tide amplitude of 4.5 m on average.

 

As you enter the Gironde Estuary, there will be two SLOWDOWNS of magnitude. First, the tidal wave will be slowed down by the shallowness of the estuary. Second, the tidal wave will be slowed down by the descending current of the river. And since this slowdown will occur in the lower part of the tidal wave, the upper part will begin to tilt imperceptibly as it goes along. A bit like tilting forward when you trip over your feet!

 

So that in a few hours of propagation, the wave deforms, with a staircase phenomenon, which stacks on top of each other and ends up forming a ripple similar to corrugated iron as it approaches the shallowest parts of the river and forms an undulating tidal bore. Be careful, there is still too much depth in the estuary for this tidal bore to break. It is only by hitting very shallow areas (let's say less than 1 meter) that the undulating tidal bore becomes breaking. In the estuary, it is at Macau / Issan, that we observe the first breaking waves, about 20 km from here, downstream therefore.

Couv-avec-localisation.jpg

© A. Colas / Thalassa FRANCE 3

And the propagation is around 15-17 km/h. Speed which can vary between 5 km/h in the dry parts with a few cm of water and 25 km/h in the deep parts at almost 2 m. This tide therefore increased by the shallow estuary, turns into a tidal bore, and comes to shake up everything in its path: the bridge piles creak, the dikes crackle, the branches and trunks on the banks are jostled, the boats at anchor lift up or change direction. The animals become frightened. "Bassilou Mascaret" was said in the past to warn of its passage. It was not uncommon for livestock to get upset or for a sheep seized by fear to find itself stuck in the mud. It is also in reference to livestock that the word tidal bore was born, since it designates the term Hatched from the appearance of the foam when breaking.

 

The sound of the tidal bore is also associated with the pounding of cattle hooves. A sound made of low frequencies, which combines the snapping of air bubbles in the water caught in the surge and the crashing on the banks. When you are in the open countryside, away from the tumult of roads, railways and other sound sources, you can hear the tidal bore a few minutes before you see it, like an approaching train.

 

So look at the Dordogne flowing. It has its source in the Massif Central some 400 km away, tamed by a few dams, and by the slight gradient of its slope when arriving in Gironde, its course flows towards the Ocean. It is therefore on the side of the front of the barge facing due West that we must look, that is where it will soon arrive. Some call it the back and forth, scientists call it a hydraulic jump in translation, dreamers the lunar wave, plumbers a backflow or a regurgitation…

 

It will take all its power in this long west-east arm of 4 km from Izon / Saint Germain de la Rivière precisely at the level of the Péniche du Mascaret. Then, it will pass the bend to feed the famous north-south section of Saint Pardon, the nerve center where hundreds, even thousands of people crowd into the small space of the Port and sometimes up to 300 candidates ON the wave. Half an hour later, it will pass the Viaduc du Mascaret to arrive at Libourne and divide at the confluence of the Isle, where a mini-bore also walks. Past the Pont de Pierre de Libourne, as old as the one in Bordeaux, it will take nearly 45 minutes to go around the big cingle, this loop that the river forms with a few furtive appearances of the Bore. After crossing the Garde-Rose bridge for those who know it, it suddenly resurfaces to surprise between Moulon and Branne and it is at Vignonet, 70 km after its first appearances! that it will finally run out of steam and produce its final surges. Thus, it will have surged here and there for nearly 3 hours! The tide will continue to be felt up to Castillon la Bataille and thus mark the last oceanic influence. It was about time, we are still 200 km from the mouth!

Antony COLAS © 2024

Passage of the Christmas Tidal Bore over the site on December 25, 2022 with a coefficient of 96

Tidal bores in 2025
(coefficient greater than 80)

  • January 1st to 4th (max 83 on January 2nd)

  • January 13-17 (max 86 on January 15)

  • January 31 to February 4 (max 99 on February 1)

  • February 12-16 (max 90 on February 14)

  • February 27 to March 5 (max 111 on March 2)

  • March 13-17 (max 90 on March 15)

  • March 27 to April 3 (max 114 on March 30)

  • April 11-15 (max 85 on April 13)

  • April 25 to May 2 (max 108 on April 28)

  • May 25 to 30 (max 97 on May 27)

  • June 24-29 (max 88 on June 26)

  • July 13-15 (max 81 on July 14)

  • July 24-29 (max 89 on July 26)

  • August 9-15 (max 95 on August 12)

  • August 22-27 (max 92 on August 24)

  • September 6-13 (max 106 on September 9)

  • September 20-25 (max 91 on September 22)

  • October 5-12 (max 110 on October 8)

  • October 20-23 (max 86 on October 21)

  • November 3 to 9 (max 106 on November 6)

  • December 13-18 (max 89 on December 16)

Passage of the Tidal Bore over the site in the heart of autumn on November 11, 2022 with a coefficient of 76

06 15 36 74 08

13, Dordogne road 33240 St Germain de la Rivière

Menu

  • Instagram
  • Facebook
  • LinkedIn
  • Pinterest
  • Youtube

© La Péniche du Mascaret 2022 - 2025 INPI N° 204699461

bottom of page