The Devil’s Bridge Gorges
1. At the lighted footbridge
Coming down the stairs you probably had the impression you were entering a cave;
in fact it is a very narrow gorge, hollowed out through a resistant rock. Here in these galleries , covered over several dozen of metres of piling blocks the Dranse has continued its work of erosion. But the arch itself was heavily cracked; over the millennia it disintergrated from the effect of the infiltrations. The blocks above us are the remains of this original arch. The blocks behind you close the gorge and are presumably the remains of a brief underground passage of the river. Other rockfalls also occurred; they were due to the subsidence of a part of the Rocher de la Garde at the entrance of the valley. Along the access path you probably noticed these piles of rocks which are overgrown by the forest.
The gorge, properly said, is the result of the slow erosion caused by the Dranse de Morzine, which has gradually cut into the rock like a knife. This erosion, which took tens of thousends of years, mainly occurred during the melt of the last Great Glaciers which covered the Alps.
At that time the flow of the torrent could be much more powerful than it is today. This explains the importance of the erosion: the gorge reaches a depth of 60 metres; here you’re 45 metres above the river. The difference in level between the road and the river is 120 metres. It is the force of the torrent that has dug out these enormous cavities you can see along the walls. These are very rapid whirpools which sweep away the sand and shingle that dug them out: They’re called “giants’ kettles”.
Yet the Dranse has cut his way through a very resistant marble-like rock ;
it is grey, white veined; but the walls have been covered with a 2 – 5 centimetre thick deposit by the surface water and have been coloured brown and green by metal oxydes and salts.
In former times red and green marble was extracted from the La Vernaz quarry, a village 2 kilometres from here.
Because the rock is a compact and resistant rock, the walls have remained the way the river had sculpted and polished them. When the rock is more crumbly, they are worn away by the effect of the frost and surface water; the profile of the gorge then opens out, as you will be able to see upstream when you reach the end of the walk. At Bioge, 1 kilometre downstream, the Dranse de Morzine which you drive along, joins the Dranse d’Abondance and the Dranse de Bellevaux, also known as Brevon.
The river containing all three, flows into Lake Geneva at Vongy near Thonon-les-Bains.
The dam at Le Jotty, 1 kilometer upstream, holds back a large part of the Dranse de Morzine, which is then diverted through a tunnel and a forced conduct to the Bioge hydroelectric powerstation.
2. After having descended the big stairs
This enormous block, forming an arch above the Dranse is itself also a collapsed rock ; it is the one people call “Le Pont du Diable” (the Devil’s Bridge).
Once it was used to cross the river by the habitants of Le Jotty and La Forclaz, who used to take the path you can still distinguish on the side of the rock.
This short-cut saved them a 4- kilometre detour via the Bioge bridge.
The Pont du Diable was used until the site first began to be developed as a tourist attraction, already in 1893.A platform was built above the rockfall: it was used both to gain access to the site and to cross the Dranse.
We owe the touristic development of the site in 1893 to one of the region’s craftsmen, a carpenter who had converted himself to tourism, installing footbridges of which some traces can still be seen: forged iron supports and steps carved out of the rock like those surrounding the giant kettle opposite you.
The present installations date from 1936 and 1951.
When you have crossed over, don’t forget to take a look just above you at the largest part of the dislodged arch; it is an enormous rock from which the Pont du Diable itself has become detached and which is estimated to weigh about 5,000 ton.
3. On the lower footbridges
Just after it enters the gorges the Dranse suddenly slows down because the depth reaches here about 6 metres. When the snow melts the two large fallen rocks can be covered by the water which sometimes even comes up to within 1 meter of the lower footbridge.
Very high flood waters may also be caused by heavy rainfall, like in 1968 when the water level rose about 15 meters. The Dranse in spate had totally destroyed the two main lower footbridges.
The green colour of the water outside the spate periods is due to the proliferation of a microscopic moss which remains in suspension and gives the characteristic green colour to mountain lakes, like Lake the Montriond at the foot of Avoriaz or Lake Vallon above Bellevaux, to mention just two in the vicinity.
You probably have admired the arch formed by the trees above the gorges.
Most of these trees are beeches, but you will also find some lime- and ash trees, alders and maples.
At the end of the walk you will notice the very great difference that appears between the layer of marble and the upper zone of less resistant chalk marls, which explains the sudden change of landscape.
ENJOY THE REST OF YOUR WALK AND THANK YOU FOR YOUR VISIT