The NOASC Avalanche Terrain Risk Scale (NATRS) was developed through a need for a logical methodology for prioritizing the steps to identify variable risk avalanche terrain for our backcountry operations. This scale is based on the philosophy put forth by the internationally recognized scale for grading rivers, which is a scale that our guides have an existing understanding, knowledge and experience in the use of, through their summer adventure guiding which includes whitewater raft guiding.

NOASC looked at other terrain risk scales including the Avalanche Terrain Exposure Scale (ATES) developed by Grant Statham and Bruce McMahon, 2004, Parks Canada Agency, and the Avalanche Terrain Scale (ATR) proposed by Dick Penniman and Rene Boisselle, 1996 Decision-making on variable Risk Terrain, International Snow Science Workshop (ISSW), Banff Canada. We have incorporated ideas, concepts, and terrain features used in both of these scales in developing our risk scale. In order to help decrease any subjectivity with interruption of the scale and to reduce an ambiguity problems, we have tried to use easily recognizable/measurable terrain features, assigning quantitative values to them.

Once in the field, we further make decisions on course selection, etc., based on local microclimates and snow pack stability, so as to minimize avalanche risks to the backcountry tour party, as much as is practically possible. If the risk level cannot be controlled inline with the tour's goals by using both snow stability tests, and route/slope selection using the NATRS scale, the guide in the field always has the authority and ultimate responsibility, to cancel the backcountry trip.

Click here to view a our NOASC Avalanche Terrain Risk Scale pdf