Yesterday (early March) I went out to practice some shelter building and other survival and Search and Rescue skills as our final SAR test is coming up soon. I found that there was a lot less snow than I expected up on Mount Hayman. There was no snow at the Trail head on the end of Bartley Road. Up at the trail at the 2 to 3 km area there was a bit more snow but not too much to keep us from checking out some of the nice view points along the ridges overlooking the Okanagan Lake.
One of our goals was to practice building a waterproof overnight shelter. In a true survival situation we would most likely have used green boughs for thatching across the top of the shelter but in trying not to disturb the forest too much we allowed ourselves the use of a tarp from our 24 hour pack as well as some rope to tie the tarp down.
After a few practice designs, we have decided that the quickest system for the supplies we had on hand would be to lash one end of a ridge pole against a solid tree with the other end on the ground. Place the tarp over the ridgepole with the tarp starting to wrap around the ridgepole by lying it on the ground under the pole, placing the pack on the tarp, putting the tarp up and over the pole and back down to create a triangular shelter. Secure two short poles to the ridge pole, one at the front, keeping the bottom of the front pole on the ground movable for your doorway and the bottom of the next short pole close to the bottom of the first one to form a triangular shape holding the side of the tarp away from your body and secure from blowing winds. Your pack would hold the other side of the tarp out. The best size tarp would be a 10 foot by 12 foot tarp as this size gives you lots of room to seal the end by your feet as well as a movable and securable flap for the door.
So why bring a tarp in your 24 hour pack instead of a small tent? A tarp can be used for any covering such as a quick cover to get out of a brief rainstorm. In the mountains around B.C., you could become drenched very quickly but with a tarp handy, you just stop get under and keep dry until the rain cloud passes. This happens on a regular basis in the mountains even when the weather report has said there would be little chance of rain.
If you have to pack someone out on a stretcher, it would be nice to cover the inujured person or stretcher with a tartp to keep them dry. If you have a hammock for sleeping in when it is warm out, a tarp is nice to secure above the hammock to keep the dew off. Now if you have a tarp, you do not need to carry a tent and save yourself the weight.
One of the tricks we would use is to tie a rope around your ridgepole near the top just ahead of the start of your tarp and if it rains, the rain will not run down the ridgepole into your shelter but down the rope instead.