Fourbanne Exploration Project

Fourbanne Exploration Project

We explore and survey the Résurgence de Fourbanne, a cave located in the Northeast of France in the Doubs region. You can find the results and reports of our efforts on this page.

Cavediving exploration and survey project in the Resurgence de Fourbanne. This cave is located close to Baume-les-Dames, Doubs - France. The source lies on private property, in the backyard of a beautiful garden with an old water mill (see photo above). Permission of the owner is required before diving here.

Operating as usual


This year has gone a bit different than planned. A trip planned in April to radiolocate a big chamber we had found last year, between S7 and S8, unfortunately got cancelled due to the corona measures taken at that time. Since then agenda's didn't permit us to plan a new trip.

On the positive side: a nice 10 page overview of the Fourbanne-En Versenne project sofar has appeared in the Karst Comtois 2, a publication of GIPEK (

The articles in "Le Karst Comtois 2" are about caves in the Franche Comté and include geological and hydrological studies and reports off cave explorations.

For more information on this interesting 200 page inventory or if you want to get one, take a look here:


The topo for the Fourbanne cave updated with the progression during the last trip.
If you download the topo you can zoom in. 07/09/2019

JT 19/20 Franche-Comté - France 3 Bourgogne-Franche-Comté

Great news. Richard and Ferry explored 220 meters of new cave and added 259 meters to the survey. The new siphon to pass in Fourbanne is siphon 9! Good progress again! More details and a topo will follow later.
In the meantime at the other side in En Versenne last week Stephane Guignard, with the help of diver Christophe Rognon and a big team of speleologists, passed Sump 5 at the En Versenne side and discovered siphon 6. Siphon 5 has been an obstacle for several decennia in En Versenne. So real steps are made in closing the gap between the 2 caves.

Also the French tv-chanel '3 Bourgogne-Franche comté' visited us to do a short reportage on the project. You can see the reportage under the following link. It starts at 10 minutes.


We realised the first goal of the current trip: doing a radiolocation of the end of Siphon 6 which we reached last trip. The radiolocations sofar showed that our surveys were very accurate. However, this time we were a bit off for the first time. But now we can use the radiolocation to correct the survey. It appears that the radiolocations tend to end up in funny places. We have been om the middle of the provincial road on an earlier trip defining the exact location while cars were waiting or trying to pass. This time we managed to be under a big pile of s**t :-).
Tomorrow Ferry and Richard will be trying to push and survey siphon 7 which Marlon discovered last trip.


Testing the MNemo

Update: testing the MNemo for the next Fourbanne trip. This device measures depth, azimuth and length and will make surveying easier and faster.


Summary of the April 2019 trip

From the 17th to the 21st of April we had a new try at passing S6 in the Fourbanne Resurgence.

We reached S6 for the first time in June 2017. Since then S6 has proven to be difficult to pass due to: length and depth of the sump, a lot of sediment and the fact that to push S6 involves an underground trip off 1,8 km. This includes 5 sumps, 1,4 km of diving and having to walk, swim, and pass small waterfalls and boulders between sumps 3,4, 5 and 6 with all the gear needed to push.

We also had several set-backs in our efforts to pass sump 6 (bad circumstances, leaking drysuits, problems while transporting a lot of gear like getting stuck in a restriction, being too negative etc.). However, at the same time we also learned a lot while slowly progressing and becoming more efficient each trip. The biggest progress so far had been made in August 2018 by Ferry who managed to put in nearly 150 meters of line in S6 in one go under difficult circumstances.

In February this year we went to Fourbanne, not to push, but to improve the line and to make set-up dives with a lot off gear easier and safer. Notably, by changing some jumps and gaps into continuous line and by replacing the thin exploration line in S3 by a thicker line. In some places we also rerouted the line circumventing where possible tight passages making it easier to swim with a lot of gear. These improvements were helpful this trip. Reaching the 'bivouac' post-S3 with all the gear needed for pushing (a dive of nearly 1.4 km upstream) was quicker and easier than before thus also improving safety.

The set-up this trip involved getting safeties in S2 (by far the longest sump), 6x 8,5 liter and 2x 7 liter tanks to the beginning of S6 and 4x 5 liter tanks to the start of S4 to transport the previous mentioned bottles through S4 and S5. Also a cooker with pans (thanks Elke) was brought to the bivouac for future use and some more food. A cave link was set-up in the bivouac and Jan and Dennis also made anchors in the walls of the bivouac so hammocks can be placed in the future.

During our set-up dives we got a visit from an old buddy of mine, Stephan Mathies, who I did my fundies with ages ago. He made some nice video shots of our project and he got to know everybody iinvolved and what we are about. It was nice to have him around for a couple of days and we hope to see him back in the future to record our project.

On Thursday the 18th Richard and Ferry got the first 8,5 liter tanks from the bivouac to the start of S6 and Richard set-off on a new effort while Ferry waited at the start of S6. Adding his line where Ferry had tied off the last time, after having passed the deepest part at 20 meters of depth, the sump slowly became shallower. Several times, it looked like he was going to surface, and sometimes he did surface, but than it went down again making for a real yo-yo profile. But finally he surfaced on the other side of S6! Richard saw a corridor going on, Post-S6, but it looked narrow. After tying the line off just above water level he turned around.

At about two-thirds into S6 he also found a promising lead which he noted might be worthwhile investigating, especially if the 'dry' corridor post-S6 proved to be a dead end. Richard and Ferry came up in the source eight hours after having set-off. Richard with a big smile on his face showing a nearly empty explorer reel. Due to this quick and efficient push dive we now still had 6 out of 8 tanks for pushing and surveying still available.

Frans and Marlon went off the next day to check the dry part post-S6. On the way back (downstream) they would check the lead Richard had noted in S6. Post-S6 proved to be chaotic with some big boulders, several leads on the left side and a passage which, fortunately, was passable. Following the river upstream a short way through the passage, walking and swimming, the flow suddenly stopped while the corridor and river seemed to continue. This was confusing. However, on inspection, 2 meters underwater near that point, in the bottom, a big whole was found where the flow clearly passed through. And thus the beginning of S7 was found.

Marlon made a primary tie-off well above the river and put the first line in in S7 working his way against the current through the whole in the bottom. He came up on the other side in the river and after swimming for 10 meters had to go down again. The sump then continued at a depth of around 5 meters. However, soon the dive had to be called due to turn pressure. Larger tanks are going to be needed here. On the way back the lead in S6 was checked but it proved to be a small bypass ending up on the mainline a couple of meters further on.

Saturday the 20th the last 2 tanks were used for surveying. Frans had surveyed the first part of Sump 6 in the August 2018 trip. Ferry managed to survey the rest now, completing the survey to the end of S6. We now know S6 is 355 meters long and at its deepest 20 meters.

Let's see what surprises S7 has in store for us. Transporting the necessary gear to continue pushing to the start of this sump is going to be a real challenge in the future.

Thanks again to the people from the speleology club ASDC for their help and for letting us use their large tent as a space for eating and briefing and for the nice dinner and drinks we had together. Thanks as well to the village of Fourbanne for letting us put up our camp in the middle of their village and to Heleen for sharing her photos of this trip and to Stephan for his interest in our project and the video shots he shared. The dive team: Richard, Ferry, Marlon, Jan, Dennis, Frans and Jeroen.

Together with this post you'll see, as a stick-map, a screenshot of the .kml file on google earth and some photos of this trip. The cave has now been mapped for 2.128 meters (and some more if you include the side passages).


Some more scenic photo's after a successful project week. We will give you a detailed report later on, including an updated stick map.


Sump 6 is now passed and we took a peak into sump 7!


Getting ready to become famous #camera


Today, Dennis and Marlon continued the exploration with the rest of the team.


We will start with a little set up dive for the upcoming week 🙈😊


Ready for a new week of FEP diving😁
Let’s see what this week will bring us.


Frans showing off with dinner after a long day of line improvements in sump 3


We are back in Fourbanne. Frans is warming up a nice meal for everybody. Later more exiting news.


Working in progress :)
Dive team Maaskantje supporting Denis and Claude from ASDC.

Visit a place of the Fourbanne Exploration Project.


Fourbanne trip 31/3-6/4 (Voir le premier commentaire pour la version française).

The main goal of this trip was to pass Siphon 6. Being longer, deeper and more complex (restrictions, side passages, sediment and percolation) than the shallow, short siphons 4 and 5, S6 is a challenge. We also planned a presentation, together with Denis Motte, for the people living in the area.

Through the mayor we got permission to camp on public ground at Fourbanne not far from the cave. The ASDC speleo-club had set-up a spacious tent we could use, including a big table and a gas heater, which was perfect for briefings, eating together etc. Especially, because we had a few cold and rainy days.

For pushing S6 we decided to use steel 8,5 liter side mount tanks this time, as the 5 ltrs used last time were insufficient. The 5 ltrs we would now use for transporting gear through S4 and 5. Unfortunately, before we left for Fourbanne, one day of really heavy rain passed. When we arrived the flow and visibility (somewhere between mushroom and euh …. pea soup) were too bad to dive. Fortunately, after a day the situation improved enough to start setting-up. Although flow was still strong we finished most of the set-up according to plan. As more rain was predicted for later in the week we decided to speed things up doing the last part of the set-up and the push dives in one day instead of 2. On ‘push’ day, 6 divers arrived in the “bivouac”, just after S3, swimming against a strong flow with a lot of gear. With high expectations 3 of us started upstream in the river post-S3 to check the situation. However, the ‘small’ and normally very passable waterfall just before S4, proofed to be not so passable this time: the team was forced to turn around. S6 still keeps its secrets from us.

Still we could test a lot of ideas we had put into practice for this trip. Transporting the full steel tanks went well due to the foam we used to neutralize them underwater. We experimented with a dry tube made by Dennis. And a real experiment it was: it got a bumpy ride of many hours up- and downstream. However, it passed the test. We had four Cave link relays this time (2 from Daniel and 2 from the CEP association). Daniel, Dennis and Jan tested setting-up a network with multiple relays making it possible in the future to communicate between different locations in the cave and on the surface.

We were also invited by the ASDC to assist in digging for a potential new entrance to the still unexplored part between Fourbanne and En Versenne. Hard work for cavers used to floating in water ☺, but absolutely a fun day.

Finally, over 40 people attended the presentation among which several mayors of the villages bordering on the trajectory of the cave. Denis Motte told about the history of the exploration of the En Versenne cave. Especially impressive were the photos he showed of Jeff Loeillot diving in the, then still, polluted water in the first siphons on the en Versenne side and of the artificial entrance dug near Fontenotte. It is clear an incredible amount of work has been spent in the past on this exploration! After Denis, Marlon gave a summary of our efforts exploring upstream into the system from the Fourbanne side. It was really nice to see there was a lot of interest and we got a lot of questions.

The photos in below album give an impression of our trip.

Thanks to Mr. Prost for his hospitality, like always! Thanks to Daniel for being so helpful again and to the ASDC (Mag-Val Richardin, Michel, Louis Hugueny, Denis Motte, Claude and others) for providing and setting-up the big Marebout, looking for a new entrance and for all their support. The dive team this trip: Richard, Ferry, Marlon, Frans, Jan, Dennis, Jeroen and Jeroen.


Back in Fourbanne. Preparation tanks for upcoming dives.


It was great to hear all the presentations yesterday at the cave and wrecknight and also to be able to talk about our project. Thanks to the organisation: scuba-academie and GUE Nederland and to all the people there taking time to listen.
Below, are 2 stickmaps of the Fourbanne cave which were also in our presentation yesterday night.


Report of the November 2017 trip (for French see below/ci-dessous une traduction en Français)

Past trip (1-5 November) had as main goal doing a radiolocation. After nearly 2 km's of mapping we wanted to know how far our topo deviates and the exact location of a dry room Post siphon 3 in case of emergencies. We also planned to have a 2nd go at getting past S6. After S4 and 5, S6 has proven to be more difficult due to length, depth, tight passages and a lot of sediment. Also some distance of dry cave has to be crossed to S6 with the dive gear. Finally, some line improvements had to be done and we wanted to continue mapping from where we stopped surveying last time in post S4. An ambitious planning!

The radiolocation was a success. We realized 4 exact coordinates spread over the distance of the cave thanks to the incredible help of Daniel Chailloux and his radiolocation gear and cavelink system! It was nice to find out that our survey was only 1,4% percent off. Furthermore, line improvements end S1/ beginning S2 were carried out and the survey was completed up to S6. However, S6 itself again proved difficult to pass. There are now 2 leads established in S6 which we will explore further next time. One thing is clear, the diving part is not over yet.

The photo's in below album give a good impression of this trip. A screenshot of a stick map up to S6 on Google Earth has also been included.

Thanks to Daniel Chailloux for making the radiolocation possible and being so helpful and to Denis Motte and Frederic Martin for guiding us in En Versenne and giving us valuable input. Also thanks to the guys from ASDC, Mag-Val Richardin, Michel Mathiot, Louis Hugueny and Claude Gauthier for their help and showing us Grosbois. The dive team this trip: Richard Groot, Ferry Schram, Arno Mol, Marlon Mendonça Dias, Wethorse Heleen, Jan Duikt, Dennis Blom, Frans Janssen, Jeroen Steinberg, Anton van Rosmalen.

Rapport du voyage de novembre 2017

Le voyage précédent (1-5 novembre) avait comme objectif principal de faire une radiolocalisation. Après près de 2 km de 'survey' nous voulions savoir jusqu'où s'écarte notre topo et aussi la localisation exacte d'une salle sèche post siphon 3 en cas d'urgence. Nous avons également prévu d'essayer une deuxième fois à passer S6. Après S4 et 5, S6 s'est avéré plus difficile en raison de la longueur, de la profondeur, des passages étroits et de beaucoup de sédiments. En plus, l’équipement de plongée doit être transporté une certaine distance à pied post-S3 et post-S5 avant de arriver à S6. Enfin, certaines améliorations de lignes ont dû être effectuées et nous voulions continuer la topographie d’ou on est arrêté avec la topo en S4. Une planning ambitieuse!

La radiolocalisation a été un succès. Nous avons réalisé 4 coordonnées exactes réparties sur la distance de la grotte grâce à l'aide incroyable de Daniel Chailloux et de son équipement de radiolocalisation et de son système Cavelink! C'était agréable de découvrir que notre 'survey'/topo a dévié seulement 1,4%. En outre, les améliorations de ligne fin S1 / début S2 ont été réalisées et le topographie a été complétée jusqu'à S6. Cependant, S6 lui-même s'est révélé difficile à traverser. On a maintenant établies 2 possibles 'leads' en S6 qui devront être explorées plus loin la prochaine fois. Une chose c'est claire, la partie de plongée n'est pas encore terminée.

Les photos dans l'album ci-dessous donnent une bonne impression de ce voyage. Une capture d'écran d'une 'stickmap'/topo jusqu'à S6 sur Google Earth a également été incluse.

Merci beaucoup à Daniel Chailloux d'avoir rendu possible la radiolocalisation et à Denis Motte et Fred Martin de nous avoir guidés dans En Versenne et pour toute les informations. Merci aussi aux gars de l'ASDC, Valerie Richardin, Michel Mathiot, Louis Hugueny et Claude Gauthier pour leur aide et pour nous montrer la grotte de Grosbois. L'équipe de plongée ce voyage: Richard, Ferry, Arno, Marlon, Hélène, Jan, Dennis, Frans, Jeroen, Anton.

The Fourbanne Exploration Project

We explore and survey the Résurgence de Fourbanne, a cave located in the North East of France in the Doubs region. This Résurgence is the outlet of the En Versenne cave system. The En Versenne cave has been extensively explored in the 80’s and 90’s by the speleoclubs GSCB and GSD which resulted in over 9 km’s of surveyed cave. Exploration in the En Versenne cave followed the underground river downstream and halted at a siphon about 4 km’s upstream from the Fourbanne Resurgence. At this resurgence the water from the En Versenne cave finally joins the river Doubs. The exploration was continued from the Fourbanne side, by Jeff Loeillot, Cyril Faivre and later Jean Louis Camus. They worked upstream, diving from the Fourbanne Resurgence, making their way to the En Versenne system with the ultimate goal of making a connexion. This part of the exploration halted in the mid 90’s about 500 meters upstream from the Fourbanne entrance. We picked up the exploration from there in 2015. You can find the results and reports of our efforts on this page.

Videos (show all)

Testing the MNemo
Dennis playing with his drone. We have some nice footage, more of that later.