Route Finding-- why do you want to go that way?
route finding like many things in the bc must be learned. sometime that learning is the result of trial and error. it is not the best method. experience coupled with book knowledge can go a long way here. following someone who knows is the best way to learn this. those of you who tour with trackhead should gain this knowledge by asking why that way.
route finding encompasses many things. avoiding fresh windrifts, watching your slope angle, staying away from thin areas in the snowpack that can be trigger points, avoiding wet and warm slopes, following ridges, staying in thick trees, etc. if you know nothing other than good route finding skills then you can avoid most accidents. remember not to think of it as the long way but rather the safe way.
slope angle is simple. anything above 25 degrees can dry slab avalanche. wet slides can flow on nearly flat ground. the most common angle for a dry slab avalanche is 38 degrees. if you are skiing and traveling on slopes under 30 degrees in relatively stable conditions then you are usually ok. if you have to cross steep slopes (avalanche terrain) you should first assess it with the knowledge you have from reports and your stability tests. then when crossing do so one at a time so that only one person is at risk at a time. if you all go down there is no one left to rescue or call for help locating bodies.
ridges and trees offer protection from most avy situations. dense, not sparse trees can help anchor the snowpack and even if a hard slab fractures under your weight it will not likely move. in sparse trees each tree may become a possible release point. be aware of the differences in wooded areas. gentle ridges can load and hold slabs but sometimes are still your best route option since a slide will flow away from the center and off to the side. a scoured ridge is usually a safe bet. slides can be romotely triggered from a ridge safely and should serve as a warning of where not to ski (ie. the adjacent slope). skiing down a slide path that has run and not yet reloaded can be a safe way out of a dicey situation. when you don't have a slide that has run already you can create one by roping up and kicking a cornice to induce one. just be careful when coming out of the bottom as not to traverse under another still loaded path.
avoiding possible trigger points like shallow snowpack, new windrifts, rocks, shrubbery, etc can be tricky. it is hard to tell where the shallow snowpack may be sometimes. areas that constantly remain scoured are a good guess. spread out rocks, trees and shrubs create a discontinuity in the snowpack and can weaken its shear resistance. avoid putting too much weight right next to them. same goes for new windrifts. if there is a big puffy patch of powder at the top of the slope or on the side of a terrain feature, look to see what the other side looks like. it just might be scoured on the windward side and loaded on the lee. avoid the lee if the new slab is cohesive enough to propagate a fracture.
possible trigger points:
http://www.uoregon.edu/~opp/snow/ava...nlocations.gif
most importantly don't be afraid to turn around. sometimes that is the safest and smartest way out. i've done it on many occasions but not always when i should have. trust your gut coupled with the knowledge you have from stability tests along the way. the mountain will always be here in our time. another day maybe better. remember that route finding is both up and down.
this is far from complete, just the basics. i have attached some of trempers guidlines. i highly recommend reading his book Staying Alive in Avalanche Terrain. it is one of the most complete books i have read.
from bruce tremper:
The rules of routefinding aren’t etched in stone. It’s a dynamic process which depends on the stability of the snowpack, the weather and the kind of people you’re with. The terrain available, and how you travel on that terrain depends on the conditions.
For instance, if we consider the stability of the snowpack, we use the analogy of a stop light where we separate the stability of the snowpack into the categories of red light, yellow light and green light.
Red light conditions
Dry snow
• Localized to widespread recent natural avalanches
• Small to medium sized cornice blocks rolling down slopes produce avalanches most of the time
• Collapsing and cracking
• Most snowpit tests show unstable snow
• Recent heavy loading of new and/or windblown snow
Wet snow
• Localized to widespread recent natural avalanches
• Rain on new snow
• Rapid warming of new snow
• Sinking in past your knees in wet snow while walking
Routes available
• Avoid slopes steeper than about 30 degrees
• Stay out from underneath any slopes steeper than 30 degrees
• If you venture into steeper terrain do so only in dense trees, heavily wind scoured slopes or avalanche paths without multiple starting zones which have recently run.
People considerations
• Travel only with strong, well-equipped people with good avalanche skills.
Yellow light conditions
Dry snow
• None to very localized recent natural avalanches
• Large cornice blocks rolling down slopes produce only localized avalanches
• Localized areas of collapsing and cracking
• Mixed results on snowpit tests
• More than 2 days since heavy loading or rapid warming (longer in cold climates or snowpacks with faceted weak-layers)
Wet snow
• Very localized recent natural avalanches
• Sinking in past your ankles while walking
• Rain on old snow
• Rapid warming of old snow
Routes available
• Selective slopes up to 35 degrees but you have to really know what you’re doing. If you have low avalanche skills, stay on the gentle terrain.
• Still use full repertoire of safe travel techniques
People considerations
• Most avalanche accidents happen during yellow light conditions. Many slopes are safe enough to cross, but there’s still enough booby traps around that people with low avalanche skills will eventually get into trouble. Even someone with good avalanche skills needs to spend a lot of time gathering data to make decisions. Many of the common human factors come into play such as the herding instinct, impatience, euphoria, positive reinforcement, ego, pride, attitude, etc. Some people with lower avalanche skills can accompany skilled members but only under supervision.
Green light conditions
Dry snow
• No recent avalanche activity
• No collapsing and cracking
• Large cornice blocks rolling down a slope produce no avalanches
• Snowpit tests show mostly stable snow
• More than several days without heavy loading or rapid warming
Wet snow
• Thick, refrozen snow surface
• Mature, isothermal snowpack (no layers course-grained with established drainage channels)
• Not sinking in past ankles when walking
Routes Available
• Most routes are safe
• This is the time to do those extreme routes you have always dreamed of, but only after carefully checking them out because some extreme routes might still be dangerous.
People Considerations
• Large groups with low avalanche skills possible
link to trempers artical from above
