Rappelling in swift water
Swift water presents additional challenges for rappelling and rope work and makes some traditional techniques less effective or dangerous. The "toss-and-go" technique frequently used in the United States desert southwest is not recommended. A contingency block and single strand rappel is preferred for swift water descents.
Double strand rappel
With a double strand rappel, it is not possible to release more rope if someone gets stuck in a waterfall. With no block, the force of the water flow can inadvertently move the rope and produce a strand that does not reach the bottom of the rappel. Few mechanical ascenders exist for double strand, so it could become a problem if a canyoner chooses to abort a route and go back up. Double strand rappelling in swift water should be done sparingly, often only by the last person down.
In general, it is not a good idea to provide a top belay in swift water conditions due to the danger of getting trapped under a waterfall or entangled in a hydraulic. Self belay devices are also not recommended in swift water conditions due to the risk of getting jammed. Bottom (aka fireman) belay is recommended, but it may not always be possible (e.g. when a large, deep pool is present at the bottom of the rappel). The person providing a bottom belay (or anyone else for that matter) should stay out of the fall zone where rocks dislodged during a rappel may fall.
Knot at the end of the rope
In general, a knot at the end of the rope is not recommended when rappelling in swift water conditions. It may be used in long pitches that involve rappelling next to a waterfall, but it is rarely justified when the rappel is in the line of water. In swift water rappels that end in a shallow pool, it will be safer to set the rope length deliberately too long for the first person down and then bring up some. For swift water rappels that end in a deep pool (possibly with a hydraulic) it will be safer to set the length too short and release rope on demand as signaled by the first person down.
In general, for swift water conditions, it is recommended to use a descender that can be quickly disconnected and that stays attached to your harness (Pirana, ATS, OKA, CRITR, Hoodoo, etc.) rather than a descender that requires a complex disconnect (bobbin, rack, etc.) or that needs to detach from your harness to disconnect from the rope (Figure 8, ATC, etc.). The presence of horns is also preferred in order to facilitate friction control, so one descender can be adapted on multiple rope widths and rappel conditions. Regardless of the descender you use, it is highly recommended to carry a Figure 8 descender in order to rig contingency blocks.
A whistle should be attached to the side of the helmet with a thin elastic cord (a hair tie works well). Attaching a whistle to the neck is not recommended. Before starting a descent, prepare to request more rope by keeping the whistle tight between your lips. This eliminates the difficulty of finding and retrieving the whistle under the high-stress situation of being immersed in a powerful waterfall. A standard signal is 3 whistle blasts, representing the three syllables of "give more rope" or "let down rope". It is also better to ask for more rope before you are immersed in a waterfall, because the person managing the station can be slow in responding and unlocking the block.
Lower your head
In a waterfall, people instinctively gasp for air and raise their head, trying to keep it out of the water flow, when the opposite actually works better. Lowering your head allows you to use your helmet as a shield to deflect water and create a pocket of air where you can breathe. You might not be able to see anything around you when surrounded by white water, but you can continue to rappel until you exit the water flow. Just make sure you don't run out of rope. If in doubt, signal that you need more rope as you keep rappelling, and keep both hands on the rope so that if one runs out of rope the other can still hold.
Rappelling through a powerful jet of water can be extremely dangerous. If it hits in your chest, it may push you back and invert you; if it hits your feet, it may sweep you out and cause you to fall, engulfed by the waterfall. In these circumstances, it is good to rappel sideways so that you present a smaller surface area of your body for the water to push against. You can also choose to rappel on your knees (or one knee), which is a more stable position because it lowers the center of gravity. However, make sure to keep your head out of the jet.
When swimming in a calm pool, tightening your waist strap will greatly facilitate forward and backward swims. When swimming in strong current it is best to adopt the defensive position: feet first in a half-seated position, looking forward, and paddling with your arms to control the trajectory. For escaping water hazards, there are special swim styles that are described in further detail below.
When landing in a deep pool and the rope length was not properly set, it will be necessary to perform a swimming disconnect. In such cases, it is best to float "otter style" on the back, and disconnect from the rope with your belly out of the water so that you can clearly see and operate your descender.
If you anticipate the possibility of entering a dangerous hydraulic (usually at the bottom of a waterfall, and often with a frothy appearance), first try to avoid landing in it. Be aware that landing next to a hydraulic is safe if you can stand, but if the pool is deep and you must swim, you run the risk of getting suctioned into the hydraulic by the "blackhole effect". If entry is inevitable, send down the most competent swimmer first to attack the obstacle. The first person tackling an hydraulic shall:
- NEVER wear a pack, in order to minimize surface area (less water force) and be more streamlined (swim better).
- NEVER carry unnecessary gear on the harness, in order to minimize chances of getting stuck with underwater branches/rocks.
- NEVER have a knot at the end of the rope, if present undo knot before entering danger zone.
- NEVER have excessive rope in the pool, always set rope length to barely reach the pool edge to avoid swimmer getting tangled.
If necessary, the first person down may stop at a ledge or wedge in before reaching the danger zone, disconnect from the rope, and jump out to escape the hydraulic and/or getting entangled in the rope. If the rope length is properly set and there is no knot at the end of the rope, sometimes pushing off the wall and letting go of the rope about 5'-10' above the water surface may be the only option. When facing dangerous hydraulics, it will be safer to send two people down on separate rope strands to work together in overcoming a the obstacle. One person should stay on rope in a safe zone at the edge of the pool while the other tackles the hydraulic. The second person may assist the swimmer attacking the obstacle by providing a body push, floating anchor, tow anchor, rescue rope, etc. Once the swimmer has successfully overcome the obstacle he will assist the rest of the team to get people and gear down safely by providing deviation, tagline, zipline, guided rappel, rescue rope, etc.
Always avoid rappeling with a pack wherever there is strong currents or hydraulics. Leave the pack behind and have someone toss it to you afterwords. If there is risk for the pack to get stuck or get trapped in an hydraulic, send packs down using a zipline technique once the first person has safely overcome the obstacle. If you already started a rappel wearing a pack, remove it while still on rappel and either toss it in an area where you can retrieve it later or abandon it somewhere where the pack will stay put till the next person down can retrieve it and toss/zipline it down.
In most cases, the best way to overcome a hydraulic is with a guided rappel. One person (usually the most experienced) will rappel down, overcome the danger, and anchor the rope from the bottom so the rest of the group can safely bypass the danger. Make absolutely sure the rope has enough tension, and pay special attention to where the midpoint of the guided rappel is, and where it will end if the rope sags. If there is not enough tension, the rope will sag in a V shape, which often causes the rappeler to be engulfed by the same waterfall the group was trying to avoid. The sag will make it very difficult to keep moving forward past the middle point.
In extreme cases, a hydraulic may be so dangerous that it will be preferable to use a floating anchor to provide a guided rappel for the first person down. A floating anchor is usually constructed with a pack, with the end of the rope tied to it. It is thrown down into the pool below, and it will flow downstream past the following waterfall due to the current. Once the bag is hanging in the next waterfall downstream, the rope will be tensioned and may be ready to provide a guide for the first person down. If the tension is not strong enough, clip more packs to the rope and zipline them down to join the first pack; add as many packs as needed to guarantee the rope will not sag too much and put the first rappeler in danger.