On the Cantabrian coast in the summer it is relatively common for a tourist’s vehicle to end up taking a dip when they park where they shouldn’t, but in the Passage du Gois In France there is no surprise factor: the road sinks when the tide rises, something that happens twice a day.
Given the risk, it would be worth considering closing that route and using the alternative Noirmoutier bridgebut there are many people here who have come to play: in 2021 exactly 387,823 vehicles passed by, according to data from the Noirmoutier Tourist Office. If you’re one of those people who ventures out, the landscape is already iconic: the Tour de France has started there on several occasions.
Now there is a road, now there is not. The Passage du Gois is 4,125 kilometers long and runs through Bourgneuf Bay, literally in the middle of the Atlantic Ocean. On one side is the island of Noirmoutier and the connection with the rest of the continent takes place in Beauvoir-sur-Mer, near Nantes. This infrastructure belongs to the D948 network of the Vendée department. The passage or not is determined by the tides: according to the tidal coefficient That day, the road is covered by between 1.30 and 4 meters of water at each high tide.
The Passage du Gois on Google Maps
To pass or not to pass, that is the question. Step recommendations from the local tourist office are enough to make you think twice before crossing: if the tide coefficient is high, you have 90 minutes before and after low tide. When the coefficient is low, the margin is reduced so much that it is recommended to cross only at the exact moment of low tide. If you measure wrong, you’re risking it: four kilometers can be fatal.
The good news is that Since the 19th century there have been nine safety beacons where you can leave the car and wait for the tide to go out or the emergency services to arrive. Spoiler: every year there are cars that end badly. Everything is signposted, but the authorities They have encountered another enemy unexpected: the GPS, which does not indicate low tides or weather conditions. Be very careful if you are one of those people who follows what Google Maps says to the letter.
The movements of the tides in the Passage du Gois. Marine Hydrographic and Oceanographic Service
Why build a road there?. Short answer: because nature put it there. Not so short answer: the origin of the Passage du Gois is geological: it was formed by the convergence of two opposite currents, one from the northwest influenced by the Loire estuary and another from the south influenced by the Atlantic. Both are found on the island and slow down there, producing a phenomenon known as wantijthat is, the deposition of particles at that point of collision of the currents, which causes the seabed to rise until it forms that natural back on which the roadway was planted.
Building it was not easy or fast. Paving the road lasted five yearsfrom 1935 to 1939, which sounds truly outrageous even though it is almost a century old. The reason is that the works had to be carried out during low tide, which greatly limited the daily work time to two daily periods in a period of about two hours. From then on, the road was passable for vehicles on its already characteristic cement slabs. Since then, several sections have been subject to different paving tests that have never come to fruition.
A future that looks very blue black. The Passage du Gois floodable road is neither the first nor the longest, but it is one of the first candidates to disappear in the immediate future. Considering sea level rise projections provided by the IPCC of the Intergovernmental Panel on Climate Change, will be between 0.38 and 0.77 meters by 2100, with different emissions scenarios starting in 2050. This implies that roads like this will see their safe operating window progressively reduced, making it increasingly unviable and dangerous.
Cover | Pinpin and Florian Pepellin
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