River crossing in snow covered areas
When crossing rivers and streams in snow-covered areas, leaders should be very aware of cold and exposure injuries. Remember that the water being crossed will be extremely cold, and if people spend an extended time in the water, they will soon lose all feeling and ability to use those limbs in the water.
Whenever possible avoid crossing rivers in such cold environments. When planning your trip, you may want to consider packing a pair of wet-suit boots to protect your feet and keep your boots dry.
Crossing snow bridges is a particular danger nearly all skitourers face at times. Assessing the strength of a snow bridge is difficult, and the consequences should a person end in the water (or in a crevasse) are potentially very serious indeed. Examine any snow bridge you are considering crossing carefully from the side. Consider the thickness of the bridge, and in particular the amount of ice within the layers of snow, and at the bottom, as it is the icy layers which give strength. Also consider the temperature, and the part of the snow season. Bridges which are very cold are stronger, and those warming toward the end of the snow season will be much weaker. Be very wary of snow bridges even when they appear secure. Think what would happen if the snow bridge gave way. How deep is the water? Can you get out, or is there a steep, high wall? Most importantly, can you get access to the river if someone else fell in? All of these considerations need to be taken into account. As a general principle, if in doubt, find another way!
If the decision is taken to cross a snow bridge, there are a number of generally accepted principles:
- Try to cross smoothly and quickly, with even weight on both skis.
- Do not kick down hard if diagonal striding – the downward pressure could crack the bridge.
- If the bridge is level with the stream bank, approach and leave the bridge at 90o
- If the bridge is much lower than the surrounding area, this is a danger sign. If you have to cross such a bridge, approach it from the lowest level possible, generally from one side, and cross it by making a U turn from one bank, across the side of the bridge, and onto the other bank.
- Do not approach a lower level bridge at 90o, as your downward momentum is likely to crack the bridge.
- Send the lightest and most agile skier first.
- Send the least experienced skiers across in the middle of the group, as the bridge is likely to become weaker with each person crossing, and having the least capable skiers separated from the main group by a broken snow bridge is a very serious situation.
- If the bridge cracks and breaks under a person, they must throw themselves forward – the snow behind them will already be broken.
The issue of crossing on skis or on foot is a complex one, but crossing on skis is generally preferred, as it is quicker, smoother and results in less jarring onto the bridge. However, if a person does go though a snow bridge, extricating themselves from the water is much easier without skis. For this reason, undo safety bindings to make the job of releasing skis easier should this be necessary.
River crossings are one of the most dangerous hazards encountered when bushwalking or ski touring. Leaders must be attentive and diligent at all times when tackling river crossings. If in doubt do not cross!