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Allt nan Uamh Stream Cave

Inchnadamph, Allt nan Uamh, Sutherland.

Probably the best known sporting (non-tourist) cave in Scotland, popularly known by its initials (ANUSC). This cave packs into a a small area probably the most complex subterranean maze in Scotland. While it has been well-surveyed and explored, it is certain that much still remains to be discovered. Extensive areas of larger passage with a network of side passages provide more strenuous caving without any real chance of getting totally lost.

The cave is relatively easy to find and without serious (or at least avoidable) risks for inexperienced cavers. Located on the north bank of the Allt nan Uamh, some 2.5 km from the car park (sign-posted Bone Caves). Follow the tourist path up the valley to the junction of the Allt nan Uamh and the Claonaite Streamway (both streams are normally dry at this point, the surface streams only flow in wet weather). Departing the tourist path follow the deer tracks either alongside the dry stream bed or higher on the west bank. The path by the stream is very rough and you may have to cross the stream bed several times. The higher path is easier but at some point you will have to drop back to the stream. 500 m upstream, a hole in a rock face at the base of a small cliff has been dammed to prevent the stream flooding the entrance. The entrance is about 75 m west of a prominent waterfall (the flow varies from a trickle to a torrent but it is impossible to miss). If you reach the waterfall you have gone too far. From a convenient flattish grassy area on the south bank, scramble across the dry stream bed or if necessary wade across the stream to the entrance. If the water levels are really high - approaching the top of the dam - you might want to reconsider your visit. ANUSC does not flood but some lower passages might become unpleasantly wet. Also, if it is that wet, crossing the burn to get in and out of the cave becomes difficult (the rocks become slippery and the fast flowing water can push the unwary off-balance). The water level has never yet been known to pass over the top of the dam but on occasions it has come close. If this happens while you are in the cave, you will not be trapped but the climb out will be through a stream which may be dammed by your body as it passes through the tube near the entrance.

Entrance Passages

From the dam, there is 2 m climb down and slightly left into a small chamber at the mouth of the cave. Sit down and feed your feet into a tight hole to the right (The Chiseled Hole - this tube was originally a honeycomb of corroded passage but was too tight. It was chiselled open by the members of the Sheffield University Mountaineering Club who discovered the cave in 1948). In wet weather, a small puddle might form in the entrance chamber above the tube but it is never more than 50 mm deep (any more and it drains down into the cave). Though the tube, you drop 1.5 to 2 m into a tight slot. In 1948, Pete Wilkinson and another un-named caver stuffed Norman Brindle (of the Craven Pothole Club) head first through this hole to where chiseling could continue from both sides. The adventurous, who like Norman, go through head first will emerging from the other side have to either brace themselves across the passage until they can swing their legs down under themselves (relatively easy) or lower themselves head first to the floor 1.5 m below (also easy but probably painful). Once on the floor, you are in a small chamber and ahead is a low stooping height arch through which is the rest of the cave. It is important to remember where this chamber is as it is the only way out. Not a problem if you know the cave, but on at least one occasion an unfamiliar caver has spent some time trying to locate this chamber. The low arch is not immediately obvious from the other side. To get out of the cave, it is necessary to raise your body the 1.5 m to the level of the tube (difficult as there are few footholds) and then wriggle through. For the shorter cavers an assist may be helpful, or by facing back into the cave and wedging your upper body against the sides, you can go in backwards swinging your feet up onto the ledges. This can be easier, as once in the tube the scalloping of the roof provides hand and footholds that the smooth floor of the tube (worn away by hundreds of caves) does not. Below the Chiseled Hole, a low crawl at floor level (now choked) runs back 10 m to solutional rifts under the streamway.

The first explorers ducked under the arch into what they called the Main Hall , a two way passage (now called the Assembly Hall). To the left, a crouching height passage runs 12 m southwest to a boulder choke. When the surface stream is flowing, the sound of water roaring past can be heard at the end of this passage. The surface water probably sinks in 7 m Hole (an unstable 4 m deep void through the boulders of the streamway about 7 m downstream of the ANUSC entrance) and emerges in Second Stream Chamber, only metres away in a straight line but not directly connected to the Assembly Hall so only reached by going much deeper into the cave.

To the right (northeast) are dry, comfortably sized passages leading to a short scramble down a steeply sloping side wall to a breakdown chamber with a complex set of junctions. known as Piccadilly. Water from Uamh an Leanaibh Neochiontach (Cave of the Innocent Child) flows under the right hand wall and a boulder choked crawl stretches towards it.

Directly ahead the obvious slope ascends to Oxford Street . The way on leads to Breakdown Cavern and the dry connection through to the Farr Series, while passages below and to the right lead to the Rift Stream Series (all described later). To the left, a high wide rift (West Rift) has been climbed , but it leads nowhere. Behind a boulder to the right, a sandy inlet rises for 12 m to some chokes. Further right, another crawl almost connects with the Rift Series. The Rift above has been climbed but becomes too tight after 10 m. A few metres farther into Piccadilly, a high rift (East Rift) joins. This enters the Rift Series, as does a hole in the floor by the left wall. To the left is the route to the First Stream Chamber, from which a low passage (The Subway) rises to re-join the higher level at Piccadilly.

Parallel Crawl, a long, low, oxbow lying west of Oxford Street was also explored by SUMC but although the lower active series was clearly entered at several points it was not forced either in 1948 or on a return trip in 1952. Attempts to determine the flow of water based on temperature readings at the Pit, Second Stream Chamber and on the surface seemed to clarify that there were two unassociated streams at work in the system. A survey to CRG Grade 3 was carried out by Pete Wilkinson and Trevor Ford and published in 1953. Nine cavers were involved in the first explorations. The cave then lay undisturbed until 1957.

Downstream ANUSC

Turning left at Piccadilly, an easy traverse around the left-hand wall above First Stream Chamber enters West Passage. After 10 m, at a Z-bend, the two-level Gypsum Passage runs off to the left to end in chokes, quickly followed by another passage on the left which leads to the Pit and a complex of small passages connecting to the Second Stream Chamber. Other passages in this complex carry water which may be that sinking in Uamh an Leanaibh Neochiontaich (Cave of the Innocent Child) or alternatively one of the downstream sinks. Returning to West Passage, a step up over boulders enters Drip Chamber, a large cavern with its mud floor pock-marked with drip pits. A boulder choke halts progress after 25 m, but a low excavated crawl on the right can be pursued for another 10 m into an area of breakdown lying above Second Stream Chamber.

Second Stream Chamber

The main route to Second Stream Chamber starts as a low passage to the left from Drip Chamber. This passes over a steepening muddy slope which leads down to the head of the Pit. and chokes after 15 m. However, 5 m before the end a rocky crawl to the right turns left and soon enlarges at a climb down into a small chamber. A crawl at floor level leads back to the Pit, while to the right the passage soon reaches a tricky 3 m climb down into the Second Stream Chamber, currently aided by a short section of 'fixed' ladder. Second Stream Chamber is a large cavity whose true size is disguised by the quantity of sediment occupying most of its area.

The large mud-coated passage ahead leads to the Static Sump but by passing over the sediment bank (a dam?) to the left, the main stream is found. The stream actually emerges from a low wet passage under the 3 m climb and loops past the dam before dropping into a series of voids dropping to low level. The stream can be followed upstream to where it emerges from a series of ducks and sumps which connect back to the base of the Pit. In the wall near here, a tight slot leads to a narrow dig in solid rock which has so far been penetrated for 5 m before becoming too tight to follow. This appears to pass beneath the surface valley and may offer one possible route into the area of dolostone between ANUSC and Uamh an Claonaite. To the right of this a small stream flows out of a large boulder choke. The source of this may be yet more of the water sinking in Uamh an Leanaibh Neochiontaich or again another local sink. At least some of this water comes from '7 m Hole' as the flow increases dramatically when the surface stream reaches that sink (about 5-6 m away from the boulder choke). The main stream descends steeply under a large boulder and to the left the remains of a Dexion hauling rail lead down a muddy gravel slope to Sink Chamber. The Dexion is now buckled and half buried as a recent collapse has shown how unstable the rock is left of this passage. About halfway down the stream disappears into a short side chamber where it disappears into an impenetrable slot. The water sinks into fissures in the floor and is not seen again until it emerges at the Fuaran Rising, some 1.5 km away to the west and 130 m lower. To the left a blasted passage soon chokes. Above the sink point, Sam's Crawl leads for another 20 m to a rift in the floor, where a 1.5 m drop gains a further crawl which continues for 5 m to a choke. Near the end of Sam's Crawl a tentative audio connection has been made to a point on the north bank of the surface streambed.

In 1957, members of the Gritstone Club diverted from their main mountaineering activity to enter the cave. They examined Second Stream Chamber and after some clearance penetrated down into Sink Chamber. Inspired by what they saw, three members (Rodger Sutcliffe, Chris Ambler and Pete Massey) returned in July of the following year and in one 5-hour stint surveyed the cave to CRG Grade 4. This survey served as the standard route map for over 20 years. During the survey work, they gained access to a thrust plane boulder choke at the end of Breakdown Chamber, explored Sam's Crawl and the passage ending at the Static Sump. Their broken line survey shows a right angled bend to the left at the end, suggesting they managed some progress in the sump (August 1961) . The sump is usually too full to show this corner. Cursory examinations of the caves resulted in a few small additions to the cave system in the early 1970s (for the most part extensions to the lower active passages from Breakdown Cavern to Piccadilly).

Static Sump Series

The large, mud -coated, phreatic passage soon descends to the Static Sump. The water level can be lowered by a self-starting siphon located in Sink Chamber to gain a crawl through liquid mud to reach an air-bell with a small stream flowing down a slight mud slope on the far side. This can be followed through a muddy crawl to the foot of a 10 m high rift, which is choked at the top. A low muddy crawl at floor level turns right after a body length to end below a hole up into another 10 m aven. The water flowing down the far wall gradually refills the Static Sump.

From here an arched passage gradually emerges from the sediments, passing a 15 m side passage on the left which ends in a choke of river boulders near the end of Sam's Crawl. Another smaller tunnel on the left becomes choked with sand after 8 m. The main passage terminates after 40 m in another choke of river boulders, just below the end of which a low draughting crawl to the right holds the promise of future extensions. An audible connection to UNCABAC has been established here. NOTE: the line through the first part of the Static Sump must not be used for free-diving into the extension. It is intended solely for emergency use by a party wishing to exit in the short time available between the lowest section sumping and the whole passage becoming flooded. Parties entering the extension should check that the siphon is cycling properly and leave someone in the Second Stream Chamber to watch over it.

Upstream ANUSC, The Pit and the Farr Series via the Upstream Sumps.

Originally only accessible to cave divers entering via the Pit, the large extension to the north can now be visited by dry cavers entering from Breakdown Cavern. Turning left just before the step up into Drip Chamber, a strides to the left brings one to the brink of the Pit, where an exposed, straddling traverse to the right leads to a 3 m climb down to the main stream. This normally starts with a short sump followed by ducks and low air-space crawls, although the whole length can sump in high water. Upstream, the water rises from a sump which until 1999 offered the only route to the Farr Series. The most important breakthrough occurred in 1976 when Welsh diver Martyn Farr entered the outfall pool in the Pit, finding a large tunnel floored with undulating silt banks. After a dive of 76 m, he reached an air-bell. Sump 1 would provide a straightforward dive if it were not for the abysmal visibility once the first diver has stirred up the silt. The sump deepens rapidly to 5 m and stays deep until it ascends rapidly to the air bell. The sump is not straight and the unweighted line can pull into low corners. There is usually one short low section where progress becomes energetic in high flow conditions.

Another 3 m section enters a canal with a low roof, 18 m of mud-coated passage with the stream flowing between mudbanks. Martyn followed this until forced to dive once more. Sump 2 extends for 24 m and varies from a low air-space canal, with a short duck at the end, to a true sump over its entire length, depending on water conditions. It surfaces in a fairly roomy 2-3 m wide passage that ends after 51 m at Sump 3. Just before the end, a high aven aligned along a fault can be climbed to Sotanito Chamber (part of an extensive upper series).

Two days after his first dive Martyn Farr returned and tacked Sump 3. This is about 45 m long and up to 4 m deep. From its end, a further 12 m of streamway reaches the foot of the 5 m high Thundergast Falls. Before this point, a number of aven-climbs gain the upper series some 15 m above Sump 3. Martyn climbed one of these avens to reach the spacious upper series which extended into the hillside and back parallel to the sumps reversing his dive routes. The easily negotiated roof tunnel led to Sotanito Chamber, a high, narrow chamber where a fissure in the floor communicated with the airspace between Sumps 1 and 2. Beyond this point, a wide but low sandy crawl descended gently for 48 m to a pebble -strewn blockage. Upstream of Thundergast Falls, the river can be followed up a series of cascades and a 3 m pot to merge with the far end of the upper series (now the normal point of entry). beyond which another 30 m of very large passage ends at Sump 4. Various holes in the roof open to diminishing inlets but provide no bypass to the fourth sump. The sump has been dived for some 30 m, in a low passage, to enter an underwater chamber at a depth of about -7 m.

Oxford Street, Parallel Crawl and Breakdown Cavern

Returning to Piccadilly, an easy scramble up the steep mud bank opposite the point of entry reaches Oxford Street (keep right for the easiest route upslope and keep your head down as you ascend as there is an area of low rock ceiling at the top of the slope which catches the unwary). Easy walking for 40 m leads to a T-junction. To the left lies Parallel Crawl, a low sandy passage which traverses a series of sand-floored chambers, and several (failed) digging attempts to reach the Farr Series, before gradually lowering to reach a final back-breaking squeeze. Despite the passage of many cavers this rather desperate manoeuvre never seems to improve. A few metres to the left, a tricky climb down for 3 m, devoid of handholds, lands in First Stream Chamber.

To the right of the T-junction, Oxford Street continues its impressive dimensions, and passes over a hole in the floor - yet another failed attempt to reach the Farr Series - before entering Breakdown Cavern, a large hall floored in breakdown. An oxbow leads back on the left, while further forward a low, narrow excavated passage on the left is the Sphincter, the actual dry connection to the Farr Series. Beyond, the main passage first lowers then becomes a wide, ascending thrust plane endowed with many perched boulders which chokes after another 10 m Its end lies near the surface waterfall 75 m upstream of the entrance, some of the water from the falls percolates through the roof.

A crawl up over boulders across the chamber, from the Farr Series connection, enters Private Deann's Chamber. This spacious rift, running above and parallel to the Rift Stream Series, can be followed for 15 m before closing down A sandy crawl on the right (Corporal Punishment) heads back for 10 m towards Breakdown Cavern, while a 3 m climb up to thee roof is halted by a choke with yet more territory visible (The Sergeant's Mess).

Rift Stream Series

A small stream sinking at the surface waterfall has invaded the older passages of the cave. It can be followed for a sportingly wet 100 m from Breakdown Cavern to First Stream Chamber. The stream is first met flowing down the north wall of Breakdown Cavern before disappearing behind boulders. Nearby, a wriggle down through loose boulders reaches a low streamway. Downstream, 15 m of crawling enters a small chamber. A crawl at head height on the left leads back to Breakdown Cavern. At the next junction, a few metres of wet crawl heads off to the left. The stream now turns a corner, the roof lowers, and an unpleasant duck follows. After more low streamway, the passage emerges through another low duck into a sloping chamber. Climbing uphill, then to the left, one enters a succession of sandy chambers and also the upper levels of East Rift. From the pool, the water flows through an opening down a narrow channel eroded in a sloping chamber. At the foot, a short crawl to the right enters the bottom of East Rift, below a boulder-climb into Piccadilly. The passage is now 3 m high as it swings left then right for 15 m to emerge in First Stream Chamber. Here, it flows into a gravelly sump under the far wall, which descends steeply. An ascending passage 8 m from its base has been followed for 3 m. The main sump is presumed to continue downwards.

The Farr Series

Originally accessed by diving through sumps 1 and 2, this extension was opened up in 1999. Near the far end of Breakdown Cavern, on the left, a low, excavated passage leads to the Sphincter. The floor of the crawl rises gently then drops away as the roof also dips into an annoying gravelly puddle. Water seeps in from a small chamber on the right which occasionally drops small rocks and gravel into the low passage below and requires to be periodically dug out (when cleared of gravel the puddle does slowly drain). The approach to the Sphincter has been re-shaped to channel both gravel and water away from the low point but this is not always successful. The upward dig in the small side chamber quickly becomes unstable if actively pushed (and it would probably emerge in the surface stream near the waterfall) so in the interest of keeping the dry entrance to the Farr Series open, digging is discouraged. Beyond the puddle at the low point, through the tight flat out crawl, the passage rises again and enlarges. Past a small complex of passages on the right, 50 m of easy progress reaches a climb down from Sotanito Chamber. The hole in the floor is free-climbable and descends to the short section of streamway between the two flooded upstream passages, Sumps 2 and 3. Across the hole, a loose scramble up a debris slope (aided by a length of rope)regains the large passage (Sotanito Chamber). Take care not to drop rubble on anyone climbing the hole below.

As can be seen from the confusing description, the cave is a maze of interconnecting loops which eventually drop to the level of the streamway. The streamway passage is challenging. In dry weather it is a shallow stream in a moderately sized passage in wet weather it becomes very unpleasant with a strong flow and little air space. That said the upper passages remain dry and there is a lot to see without descending into the wetter areas. Even in the wettest weather there are many other loops of passage which can be explored some of which arrive at the same locations by different routes.

Upstream from the streamway is Thundergast Falls, a 6 m high waterfall which in very dry weather it is possible to free-climb in wetter weather ropes are essential.

Downstream, a dam has been built across the streamway diverting the main flow down a hole to the left while beyond a syphon has been used to suck the water out of the muddy passage ahead. If the syphon is working and the weather is not too wet, then it is possible to pass through the static sump to the furthers t parts of the cave. The static sump at its best is a wet muddy squeeze. Conditions vary from aqua-mud to to 0.5 m or more of water. In very wet weather or if the syphon is not working, the static sump becomes impassible. DO NOT ENTER THE STATIC SUMP IN WET WEATHER.

A voice connection has recently been made between on of the side passages beyond the static sump to a tube off the entrance to UNCABAC. This remains only a voice connection and there is no exit from this point except back through the static sump.

Alternative Names: ANUSC, A.N.U.S.C., ANUS Cave, A.N.U.S. Cave, 'Stream of the Caves' Stream Cave

Notes: The name of the cave derives from the Gaelic 'Allt nan Uamh' which translates as 'Stream of the Caves' (being the stream passing the Bone Caves at Creag nan Uamh), to this is added the designation stream cave indicating that this is the cave through which the underground section of the Allt nan Uamh flows. This cave is NOT part of the Creag nan Uamh Scheduled Ancient Monument.

The Allt nan Uamh Valley is part of the Ben More Assynt Site of Special Scientific Interest.

Another note from 1961 states: "After diverting the stream from Top Sink, a horizontal bedding plane was forced 20 feet by one who shall be nameless [Chris Ambler], but it continued to get tighter as it progressed downstream and eventually became too narrow". 70 years on there is no record of anyone duplicating this effort. And there is little sign today of where entry was gained.

In April 1969, a party from Bristol University carried out a series of water tracing tests in the region using 'Lycopodium indica' spores. Samples were introduced into the sink point and detected not only in the cave but also at the Fuaran Allt nan Uamh and at a secondary resurgence a short distance upstream proving a definite connection. Later, it was established that the Claonaite waters also resurged at the Fuaran, suggesting a merging at some point mid-valley.

Sotanito is a Spanish word meaning 'little basement'.

Hydrographic Feeds: Allt nan Uamh

Hydrographic Resurgences: Allt nan Uamh