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Bel Espoir - Diau Traverse

by Bassett

Reseau Bel Espoir - Diau, Plateau du Parmelan, Haute Savoie

Location: This complete hydro-geological traverse is found in the spectacular lapiaz of the plateau of Parmelan.  The upper entrance is the Tanne du Bel Espoir (pothole of good hope) and the system comes out at the Grotte de la Diau.

One reaches the Tanne du Bel Espoir, situated in the parish of Dingy-St-Clair, by taking the track that goes from Aviernoz to the Chalet de l'Anglette and then following the path towards the Gouffre des Etoiles Filantes (pothole of shooting stars).  The Tanne opens 100m below this pothole.  1.7km to the north east, in the parish of Thorens Glieres, at the bottom of a cirque, at the foot of the plateau in the continuation of the valley of Perthuis, the Grotte de la Diau begins as a spectacular opening.  One reaches there via la Verrerie and a track on the right hand side of the torrent de la Filliere.

History: The entrance of the Grotte de la Diau has always been known and the beginning of the cave had been explored as early as the last century.  In 1932 de Joly and his team, reached a sump a short distance from the entrance.  At the end of 1938 various expeditions explored the cave afresh.  In 1949 the team of Chevalier and the Clan de la Diau reached a sump at a height of 130m and 2650m from the entrance.

The systematic re-exploration of the cave was not taken up again until 1974 (with S.C. Fontaine la Tronche) and in 1975 (by S.C. C.A.F. de Grenoble).  The Chevalier sump was passed by diving but the climbs in the Gronoblois streamway reached a height of + 338m at the base of the Puits des Echos.  In August 1975 B. Talour (S.C. C.A.F.) discovered the Tanne du Bel Espoir, whose exploration, because of a mistake, did, not begin until July 1976.  The junction with the Diau was made at the Puits des Echos on June 6th, resulting in a vertical range of reached of 613m.

In 1978 a junction was made with the Tanne du Tordu, and the vertical range reached 698 m.

Paul Courbon, Atlas des Grandes Gouffres du Monde, 1979. translated by G. W.-J.

While up at the B.P.C. winch meet this year Jane and I were invited to join some of the Bradford on their caving holiday in France during the summer, and do the traverse of the Bel Espoir - Diau system, up in the mountains above the lakeside resort of Annecy. Neither of us had heard anything about the place, although a little research at home would have revealed info in Courbon's "Grandes Gouffres du Monde" and in Caving International. 2. There is also something about the system in Scialet No 4 (1976) and in Spelunca (1976) but we could not get hold of those in a hurry.  So it was all a bit of an unknown – just 500m in 24 pitches (the longest about 50 m) down from the plateau, and into 2½km of  streamway descending a further 100m to emerge at a big cave in the valley.  A fairly straightforward pull-through trip, reckoned Biffo (the other Biffo, i.e. Brian Smith.)

After our Chamonix jaunt we all met up near the little town of Thorens Glieres ands made camp 'a la ferme' at Nantizel, the only camp-site around, so there were no rendezvous problems at all.  Some people were only just at home, tents erected, when we were attacked by the most vicious thunderstorm imaginable.  We cowered in our tent while Geoff Crossley and his little velvet friend 'Mole' cowered in their tent, only a few feet away among the mole hills. The rains whipped down out a dark sky, lit frequently by jagged, purple streaks and bright orange glares. Gradually the sound of accompanying thunder closed the time gap behind the lightning until suddenly light and sound were instantaneous.  The flashes were almost blinding, even through tent and flysheet, and on one occasion we both smelt burning.  Neither of us was prepared to risk going outside to investigate immediately, but as the storm abated we ventured forth to find that all was well - nobody struck and no-one drowned, and all tents still up.  Only the morning light revealed a charred patch of earth, once a proud, up-standing mole-hill, a few feet from our tents.  The lightning need not come any closer than that!

The morning also revealed mist on the plateaux and the chance of yet more storms.  However, we stuck to our plan of going in search of the Diau.  In fact it was not difficult to find as it is a kind of tourist attraction in its own small way.  We only had a black triangle on a Michelin 1 : 200,000 map, but Biffo had slightly more detailed instructions.  Leaving Thorens Glieres on the eastern road, climbing slowly towards a col, we drove along the valley to la Verrerie and then turned right and onto a track beside the stream.  From Thorens Glieres we had gained very little height when the drivable section of track gave way at a decrepitating wooden bridge.  Parking the cars we headed into the soaking wet undergrowth of the wooded slopes.  The B.P.C. stuck to the main path but we followed a narrow, steep, largely overgrown route, and later asked the way of some French tourists, which was helpful. The slopes became steeper as the path zig-zagged its way upwards, leaving the stream tumbling down its own narrow gully far below and to our right.  Past a little cliff face and along a section of path with a near vertical drop below, the trees suddenly thinned out and we emerged into a boulder strewn amphitheatre. Behind and below us a little stream trickled from beneath massive piles of boulders and ran away down a series of waterfalls. In front of us, and to our right and left, the cliffs rose up, overhanging impressively as the cirque reached up to the level of the plateau. Beyond the falling stream came the sound of cowbells.  Far away, across the other side of the valley, the road could be seen, still climbing towards the col, and entrances gaped in the cliffs above it. More immediate to us though, were the gaping holes in the cliffs that surrounded us.  Fortunately we had our climbing headsets with us and were able to do a little exploring straight away.

There are entrances higher up in the cliffs but the four at the base were the ones which interested us. We headed for the nearest first: a good draught came out from it and a little cloud of mist hung in the entrance. A short walk along the single passage brought us to a pitch which was not easily climbable, but the sound of a large stream was enticing.  The second entrance gave us more to explore, and proved to be quite a complex affair, with steep and slippery climbs, rifts, pools, and several interconnecting passages. Following the draught took us along a widening rift over pools until a particularly long and deep looking one turned us back (we were only in walking gear).  En route out a passage on the left dropped to a chamber where a wide, deep-looking pool prevented us from reaching the daylight on the other side, and the third entrance.  The fourth entrance is the biggest one, tens of metres wide and high.  Approaching it, on the left there are large banks of scree and then sand leading up to a choke with the fragile roof, while the way into the main part of the cave is through the lower, wet section on the right.  We clambered across boulders, trying hard to keep our feet dry, until we reached a black space in which our feeble lights picked out nothing.  We left the cave, being careful not to touch the walls, which had that shaly appearance of 'touch me if you dare'.

The B.P.C. had still not arrived so, after a brief search for the resurgence of the water under the boulders below the entrances and in the deep gully with the waterfalls, we headed away from the cirque.  Instead of taking the path back down we followed an upward trending path.  This continued in the same zig-zag fashion and we had soon climbed up above the cliffs that form the cirque.  We began to head away into a more level area - the base of a wide, heavily wooded valley between two plateaux.  The path continued, obviously little used, although sign-posted at one point as going to Dingy, on the far side of the Parmelan Plateau, which now extended to our right.  A few bits lapiaz peeped through the mouldering leaves, and occasional, shallow shafts broke the monotony of the woods.  When it began to rain we rapidly returned, not even stopping for the wild strawberries.

Two of the Bradford - Biffo and Jim Abbott, I think - had gone into the Diau with their one torch and had done a round trip from one entrance to another, just emerging as their light packed up - a token of things to come!  Apparently all four entrances join up inside at a big chamber, the beginning of our black space.

Next day we set off relatively early to "do" the Diau, exploring upstream as far as the Affluent Grenoblois.  Biffo had a good survey with him, and he had also copied out a description written by someone from Sheffield University who had done the trip before.  It seems that it is a classic French through trip and the complete traverse from Bel Espoir is frequently made.

Once inside the big chamber we had to wade/swim around the edge of a lake.  Jane's light had already packed up at the entrance so it was just as well she likes water.  Her light flicked on and off occasionally, usually being off when it was most needed. From the lake we squeezed up into a high chamber whose name, the Ship's Hull, describes it perfectly.  A 5m climb up an ancient electron ladder and through an amazing tangle ropes, belays, bolts and krabs, led to a similar sized and shaped chamber, again with a lake, surrounded this time by vertical walls.  A little climb up the wall led to a shelf. Traversing around this brought us to another fixed ladder and more passage with lakes and deep, blue pools. Soon we could hear the roar of the stream and we suddenly emerged from one passage to find the route blocked by a wide pothole.  Opposite us the stream appeared from the darkness beyond and, roaring and foaming, dropped into the abyss.

We easily found a passage that avoided the pot and came out where we could access the streamway.  The stream flowed down a beautiful phreatic tube, very reminiscent of the Peak streamway, with several fossil or overflow tubes on one side.  After splashing up the stream for some distance, over superb scallops and beside chert nodules and tubes that looked remarkably like fossil arms and legs, the streamway lowered at the approach to a sump.  Into the overflow passages at the side we climbed up one fixed ladder, then another, and into a narrow rift with a howling gale blowing in our faces. At the end of this we climbed down a series of wooden stemples onto a floor of moonmilk, just like the floor used to be in Salubrious in OFD.  A little way down a slippery slope the chamber widened to drop into a large, circular pool.  We had reached the stream beyond the sump, and were about half an hour into the cave.

We had already made use of some Gournier style traverse wires to get along above the stream if we did not want a wetting, and these traverses now began in earnest.  The stream in places was channelled into a relatively narrow passage, less than 2 m wide, and rushed down several cascades and over deep pools.  Above us, but still not near the high roof, was another set of wires, rusty and fragile, indicating the efforts to which previous explorers had gone in order to remain dry.  For hours we seemed to continue, along traverses, through chest deep pools, up waterfalls, under roofs that were almost beyond the beams of nife cells, but always up the stream.  If we had any route finding problems now, it simply meant we had to take to the water and wade or swim.  Eventually we came upon a rope dangling out of a little rift high up on our left. This led to the Maze and avoided some evil, deep ducks in the main streamway.  In fact the Maze was easily negotiated, not being at all complex as supposed.  We just went against the draught.  The Maze was one of the well decorated parts of the system, and deserves some photography, although it is well into the cave and carrying gear would be a bind.  We soon dropped back down to the streamway, onto a floor of boulders underneath a big aven.  The size of the passage was back to normal - big - and we continued quickly up the Salle de Chaos.  A few of us went on as far as the presumed exit of the Grenoblois inlet and a deep pool. Jim and Buzby went on to the Chevalier sump, passing the Affluent Grenoblois proper on the way. Miraculously Jane's light was made to function again (she says it's a real experience doing 2½km of hard streamway in the dark!) and we sped out, reaching the entrance after 5½ hours.

Our third day of activity was spent in finding the top entrance.  We began by driving out to the little village of Aviernoz, on the opposite side of the Parmelan Plateau from the Diau, and then taking the forest road up towards the top of the plateau.  For the first, low section this is a good, tarmac road, but it soon deteriorated into rough track, surfaced with medium to large limestone lumps, and with numerous potholes, steep drops into the nothingness, and huge logs to be avoided.  As we drove gingerly up in the Marina, breaking the steel in two tyres even so, Biffo roared away in his Sid Perou (Subaru) amidst clouds of dust and flying boulders to do the three mile journey up to the plateau in only half an hour!  At the end of the "made up" track someone has very sensibly built the Chalet de l'Anglette, where we all met up and sipped coffee or beer while we perused a huge survey of the system, courtesy of the chalet proprietor.  We already had some instructions for finding the entrance, and he gave us more, so we were clearly going to have very little difficulty.  H-hmm.

We began our walk by circling the head of a long, narrow, upland meadow, following a path that rose quickly into the woods.  The path is well marked with orange and yellow paint as it also led to other, more well known if less deep, caves, and to the summit of the plateau (if plateaux can have such things).  After about a half an hour the conifers thinned out and the paths divided.  Soon the soil itself thinned out leaving nothing but bare limestone - typical lapiaz - with straggling plants and occasional trees growing from cracks in the rocks.  To the east the plateau dropped down in a series of steps and the vegetation increased again.  Suddenly the ground plunges steeply down through a deep, wide, wooded valley, which drops over the Diau cirqu to the north.  This is where Jane and I had walked on that first, damp day.

There is only one sure way to find the Bel Espoir entrance if you have never visited it before.  From the point at which the path breaks out onto the bare lapiaz a line of widely spaced, unintentionally well camouflaged, small cairns leads out just south of east.  The line is fairly straight, passing from the lapiaz into a region of grassy hummocks and dolines, where the trees become more numerous.  The last cairn is perched on a little hill on the very edge of the plateau, and the opening of the Bel Espoir is some 50 m. below it.

We had been told that the entrance was located beside two dead trees, standing uppright in the shape of a "V".  For three hours we searched, always too far to the north.  It seemed that every dead tree, and there must have been hundreds, had another one beside it and all these pairs of trees could be imagined as forming a "V".  We must have found every other site of spelaeological importance on the plateau, and we certainly inspected every pair of dead trees several times.  On occasions we were all spread out so far apart that no-one knew where anyone else was.  Jane got herself utterly lost and only found herself when she had walked in a complete circle and accidentally stumbled upon the marked path that led back to the Chalet de l'Anglette.  Eventually Jim and Biffo found the cairns (and me) and, following the line of these, we found the entrance.  There is a pair of dead trees, not even remotely resembling a "V" shape. They will probably fall down soon - we were almost in the mood to help them on their way.   It was late afternoon by now and the clouds had threatened once or twice to roll in and conceal all, but we delayed long enough for Frank to change into his gear and descend the first pitch for photographs.  We then dumped all the rope and SRT gear we had carried up, re-traced our steps to the cars, and left the plateau.

In the morning, as early as possible, we set out through the mists for the 'big trip'.  Imagine the amazement of a party of Swiss schoolchildren 'en vacances' when an English car hurtles up the track, is rapidly parked, two people jump out and quickly disappear back along the track, then a second car roars up the track, does a quick turn around the first, and also disappears the way it came.  Actually we were dumping my car below the Diau ready for our emergence.  Not much later we had driven up through the dripping pines to the Chalet de l'Anglette once more.  Some of the group were very kindly, if unwillingly, going to return the vehicles to the bottom.  Some had taken much cajoling the day before, and so all shall remain nameless! Nevertheless, many thanks to them. The rest of us - Jim Abbott, Frank Croll, Geoff Crossley, John Green, Raymond "Snake" Lee, Mark Perry, Brian Sellars, Brian "Biffo" Smith and your very own B.E.C. reps speedily crossed the plateau and kitted up at the Bel Espoir entrance.  Some of us had opted for wetsuits while others intended to do the trip in dry gear. Neither proved ideal, although water conditions were now quite low and the 'dry 'people were much warmer during the overlong lays in the vertical section of the cave.  We 'wet' people were at least able to enjoy ourselves much more in the river passage, swimming, wading or even running downstream at times.

We also had differing ideas about lighting - some used mega-carbides, one or two were on stinkies and some used electrics.  Two people even had back up lights (some new fangled device in case your main light failed). The B.E.C. duo each had an ultra reliable nife cell, with super bulb, pilot bulb plus spares, guaranteed eighteen hours brilliant lighting, freshly top-up charged on the Bassett-mobile charging unit.  The first failed on the first pitch, the second failed on the second pitch.  Not to be outdone, the B.P.C. decided to have a little light-pox, but even by the end of the trip they had been unable to match our magnificent 100% failure, only managing a miserable 62½%.

The first, second and fourth pitches are each pendulums.  Belaying to the obvious, rotten tree at the entrance, part-way down the pitch it is necessary to swing or traverse around the wall to reach a little alcove and the narrow drop into the next shaft.  Part way down the second pitch was a much longer swing, in space, to reach a rift in the far wall - quite how Jim and Geoff achieved this initially we are not certain, but everyone else was pulled across by those already there.  By now the entrance pitch rope had been pulled down behind us and our only way on was downwards - no going back!  We began to gather at the base of the short, third shaft, waiting for the rope from above in order to rig the next pitch.  Now our next little difficulty occurred.  The second rope pulled through the belay, as it should, until the end reached the hanger, where it stuck, fast.  Even when all of us hung on the other end of it and jumped up and down it remained stuck.  At least it gave us faith in the strength of both Marlow rope and the Frog belays, however awful the latter may appear to be (see next page for diagram).  The belays are designed for pull through trips and are basically a bar set across a piece of "U" channel alloy. Unfortunately, if, our theory is correct, the space behind the bar is only just sufficient for the rope, and B.P.C. ropes have very stiff marker sleeves on their ends.  The rope ends simply would not bend around the gaps available.  Fortunately we had a knife - what would the B.P.C. do without the B.E.C.? - and were able to cut off the bottom part of the rope.  We then cut off every identification sleeve from the other ropes.  True, we could have managed by removing only one marker sleeve from each rope but we were not taking any chances.  Now we each had to remember the length of the piece of that we each carried.  Needless to say, memories are short and tackle bags were soon mixed up, resulting in several interesting pseudo-mathematical discussions to determine which bag held which rope, but we managed.


frog pull-through hanger plate

After the fourth shaft and an enormous pendulum across a wide void the passage deteriorated into a series of very muddy descents for a while, with a good draught showing that this was, indeed, the way.

Suddenly the route opened out once more and the walls became clean of the sticky clay.  A beautiful shaft hung clear of the wall and dropped into a large, boulder floored chamber, the Salle des Rhomboedres.  Some of us saw only vague shadows and inky blackness, had to be led across the chamber among some rather precarious boulders. Water was available here, dripping heavily down a corner of the wall above another precarious pile of boulders. The opportunity was taken to re-water carbides, although we found that water was plentiful from now on.  We also had a bite to eat while waiting here.

In the Salle des Rhomboedres the cold draught was briefly lost as it circulated around the chamber, but was soon found once more as we traversed steeply down a narrow rift that began between the boulders and one wall.  The rift became steeper and narrower until it went vertical.  Ahead we could hear Jim and Geoff's shouts echoing tremendously.  We had reached the top of the Puits des Echos, where echoes reverberate for several tens of seconds.  The pitch is split into three sections.  Once out onto the second part it is clear that the shaft rises an unbelievable distance above. The landing is on a ledge part way down a wide, beautifully fluted shaft, and the final section of 50m is the longest drop of the system.  At the base of the Puits des Echos writing on the wall records the link up of surveying/exploration parties, and indicates the way on down towards, the Diau.  This point marks a change in the character of the cave.  The route soon develops into a well decorated bedding cave whose mud-slope floors drop into a narrow, vadose trench.  The trench deepens and eventually it is possible to drop down, by rope to its floor and the streamway itself.  The bolt and hanger at this point were among the most lethal in the cave.  We had no spanner (a box spanner is necessary) and several of us decided not to risk the hanger.  We sacrificed some more rope in order to create a belay around a large boulder embedded in the mud slope.

In the refreshing streamway we spread out more - even without lights the B.E.C. managed to move a surprising distance downstream, arguably a dangerous practice but neither of us fell down any of the shafts.  The next shafts had single ropes rigged on them, and these were of Marlow S.R.T. rope, cut to length.  At first, those of us towards the back of the party, i.e. the de-rigging group, wondered why B.P.C. rope was being squandered in this way.  However it turned out that a British group had been through the system only a fortnight previously and it was they who had left ropes in place, for speed.

We all met up again at the 30m shafts.  The first is wet, but part way down it is possible to traverse across to a ledge and drop the second shaft, which is dry.  It was fortunate that the others had waited for us. The rope down the first section of the wet pitch was just long enough and the end was simply a frayed tassel.

It was necessary to abseil down this, lock off, lean out and up, clip into a tyrolean, unlock and abseil off the rope end, and traverse to the ledge.  Actually it was a very easy process, with lots of lights and helpful advice, but in the dark that 4m rope over a 30m drop would have been deadly. If this process was worrying then the next pitch, the dry 30m was mind destroying.  The hanger plate loosely clung to fractured lumps of limestone in a shattered wall, with no possibility of a back up belay.  A steeply sloping ledge stopped short of this almost fictitious belay and we had to lean out to the rope.  Once on the rope the swing out was enough strain to bring down bolt, hanger, wall and all so we did this bit very gingerly and then zipped down the rope almost in free-fall mode to avoid excessive jerking.  With burnt out neurons we all made the bottom otherwise unscathed.  We have all since become somewhat blasé about the solidity of belays.

The final pitch of this Affluent Grenoblois is simply a steep slope, notable mainly for its excess of bits of decaying rope.  We had now reached a more or less level area of muddy climbs and pools, very sumpy looking. The lively little stream had disappeared.  Wading through one pool we suddenly came into larger passage, and we took some moments to recognise it as the Diau, where some of us had been only two days before. From here we were home and, though not dry, we had fewer problems with water than before, for stream levels had reduced considerably.  One group raced off out, finally making exit only one light.  We were more sedate, even though we had two working lights. Nevertheless we made steady progress out.  We thought we were lost near the Diau entrance series - one of the lakes in which we had swum before had now dried up completely.

We had entered the Bel Espoir around midday and we emerged to starlight at the large Diau entrance and amphitheatre about fifteen hours later.  Mark had not come onto the plateau with us the day before, but he had not been lazy.  He had visited the Diau had deposited a bottle of beer among the rocks on the entrance chamber floor.  We now drank our fill and toasted our success.  The cave still tried to beat us, to have the last word.  As we sat supping ale a rock plummeted off the roof, only just missing Jane.  But we had won.

Just give us a light or two, a few metres of rope and a bottle of beer.  We can do anything!


I have a survey and location maps.  If I can get photocopies of them for nix, I'll put them in the next B.B. They may be of interest.