Of the numerous hazards that hikers may encounter in the backcountry, rivers are too often overlooked. While seemingly not as threatening as steep, snowy mountains or desolate stretches of desert, rivers can pose the most significant dangers to hikers. Without experience, rivers can easily lure you into a false sense of security before, quite literally, ripping your legs out from under you. This post will outline the objective hazards posed by fast-flowing rivers, as well as the tactics and techniques to help you to cross rivers safely.
Objective Hazards of Fast-Flowing Rivers
All environments have their own inherent hazards. In rivers, the danger lurks beneath the surface.
Fast-flowing rivers are powerful and can easily knock you off your feet and put you in a dangerous situation. The key hazards in rivers are obstacles that can trap you underwater such as logs or bushes (known as strainers), as well as waterfalls/cascades, and the cold. Joshua Brown–an experienced hiker and river rafting guide with swift-water rescue training, and with professional experience on big rivers throughout Australia and North America–says, “The absolute biggest hazard in rivers, particularly in areas people are likely to try and cross, is wood/branches … Water flows through branches but you get stuck, pinned by the water.” This can easily be fatal. Also, depending on the environment and the conditions, water temperature must be considered. “You lose body heat 20 times faster in the water,” says Brown, “so hypothermia will set in within minutes in very cold water.”
Assessing When and Where to Cross Rivers
When hiking in an area that you know will have challenging river crossings, it’s important to prepare yourself mentally and logistically. At each crossing, decisions will need to be made about where, when, and how to cross. This will inevitably add time and it’s entirely possible that you will be stopped in your tracks and need to turn around or take a significant detour to stay safe. It’s important to carry good maps showing side trails and escape routes, as well as extra food to provide the flexibility to be able to change your plans.
Timing Is Critical
Your schedule should revolve around crossing rivers at the safest possible time. In snowmelt catchments (i.e., the area of land that contributes runoff to a river), rivers/creeks are at their lowest in the morning (often 30–50 cm lower) due to lower melting rates overnight, and they peak in the late afternoon/evening. Note that this phenomenon can be significantly muted in large catchments due to lag effects. In larger catchments, the daily rise and fall of river levels is evened out as different tributaries peak at different times and the daily pulse has farther to travel. Be prepared to set up camp next to a river to cross in the morning.
If you are not in snowmelt catchments, but in areas where flooding may occur due to storms, take note of weather forecasts. If you can adjust your schedule to cross a particular river that may become difficult under higher flow, do so. In mountain rivers, high flows from localized storms generally flush through the system within a few hours to a day (this is a broad generalization and will vary for a multitude of reasons), in which case waiting out a flooded river may be reasonable. While waiting, track river levels using rocks or sticks as markers. However, if prolonged rain is forecast, it may be best to decide on an alternative.
Deciding Where to Cross
Sturdy logs can provide a good way to avoid getting your feet wet. Similarly, in certain conditions, snow bridges may make for easy crossing. However, snow bridges should be treated cautiously depending on the conditions and the location. For example, every summer in the Sierra Nevada, every snow bridge fails; you don’t want to be on one when it goes. Photo: Molly Bright.
Undoubtedly, the safest river crossing is one you don’t have to do. For example, if the trail crosses back over the river in a couple of miles, it may be better to bushwhack alongside it rather than make two dangerous crossings. When it is necessary to cross, the safest option is rarely where the trail crosses. Scout upstream and downstream for better options; if you look long enough, you will almost always find a safer place to cross. Accidents occur when people charge into rivers impatiently before taking time to assess better options. When scouting, take note of the depth and velocity of the flow, the number of branches of the river, channel-spanning logs or snow bridges, as well as the runout downstream of any potential crossing locations.
The runout is the area immediately downstream of where you decide to cross (i.e., where you end up in a hurry if you fall). You should always try to avoid crossing closely upstream of strainers or waterfalls where the consequences of a fall could be fatal.
It is safer to cross sections of channel where flow velocity is low, even if it coincides with relatively deeper stretches. You have more time to consider each step and the consequences of a fall are generally lower, as long as you ensure a safe runout and easy exit. Brown notes that “it is helpful if there’s an eddy on the far side of the river so that you aren’t fighting the current when you are trying to get onto the bank.” Remember that even with a weak current, your buoyancy will give you much less control once water levels are around chest deep.
Early-morning crossing of Falls Ck with a (relatively) gentle current in northern Yosemite National Park, June 2019.
When it is necessary to cross fast-flowing water, the depth becomes much more important. Trekking poles can help you check the depth. Once fast-flowing water is above your knees, crossing is particularly challenging and waist-deep water with fast, turbulent flow may be beyond the limits of comfort for many. Needless to say, the sound of boulders tumbling and bouncing along the riverbed should indicate to even the dullest imagination that crossing is unwise.
Look for places where the valley widens, as this is often accompanied by the river widening and becoming shallower and/or splitting into numerous branches that, individually, are easier to cross. Straighter reaches tend to have more regular channel beds, rather than bends that often have deep scour holes. Looking for these features on your topographical map can help speed up the scouting process.
Techniques for High-Water Crossings
The Evolution Meadow alternate across Evolution Creek on the PCT. Note the widened contours and the representation of multiple channels and swamp. Immediately downstream the valley constricts again and the normal PCT crossing is considerably more dangerous under high flow. Look for these reaches when scouting for safer crossing locations. Source: Guthook Guides.
There are a range of solo and group techniques that help make crossing easier and safer. Ideally you would practice these techniques under controlled conditions, because it’s easy to become mentally scrambled once the world is drowned out by roaring water and your legs start going numb.
Solo Crossing with Poles
Keep your shoes on and unbuckle your pack straps; if you fall, you want to be able to ditch your pack quickly if needed. However, this can leave you in a dangerous situation if you can’t retrieve your pack, as hikers on the PCT haveexperienced in the past. Only ditch your pack if it is pushing you under or you will not be able to avoid a downstream hazard while wrangling with it.
Choose your line carefully, typically angling slightly downstream. As you enter the water, face upstream with poles ahead of you, bend your knees, and lean slightly into the current, maintaining 2-3 points of contact at all times. Try to avoid crossing your legs, and be sure of each foot placement.
If you do stumble and find yourself going for a swim, Brown suggests the “white water swimming position–feet downstream, on your back, knees slightly bent, paddling backward with your arms.”
Group Crossing
Group crossing techniques can be much safer, particularly if there are less confident people in the group. In groups of two or three, grab one another around the waist/shoulders, keeping the strongest person upstream to help break the flow and cross in a line, or in a triangle formation. In groups of three or more, cross in a line facing upstream, while holding onto the pack/waist of the person in front of you. “A larger group can create a triangle shape with the strongest at the upstream point and on the sides and weakest in the middle,” says Brown.
Different formations for group river crossing techniques.
What about Ropes or Hand Lines?
Despite a popular perception among some hikers that setting up a rope across a river will make crossing safer, “ropes are almost never a good idea,” says Brown. “Even in professional rescue, ropes are avoided if possible. It creates a hazard in the water that you can get caught by and held underwater.”
Hopefully this post has helped to outline some of the key considerations when facing high river crossings while hiking. Ultimately, as is often the case in the backcountry, your safety relies more on sound judgment than technical skill, and the decisions you make before even getting into a river will be your most important.
No comments:
Post a Comment