Second, the slope where the hikers built their camp had an incline of less the 30 degrees, which is typically considered the minimum angle for an avalanche to occur, Gaume said. Remember that slope angle is just one piece of the puzzle. I’ve been using a Suunto MC-2 compass and the clinometer is super easy to read using the mirror or looking at it directly. The slope on which the fatal avalanche occurred faces northeast at 9,400 feet. Luckily for us there are a few ways that we can accurately determine the steepness of a slope. If the dangling pole touches the bottom mark, you’ve created an equilateral triangle with 3 equal sides and 3 equal inside angles of 60°. Most avalanche activity typically starts on slopes between 30 and 45 degrees. The rule of thumb is that every 10cm (4 inches) past the mark is another 3° of steepness. And the BIG inclinometer dial changes colors based on the slope which provides instant feedback on how the steepness of the terrain is contributing to the likelihood of an avalanche. In these maps, slope angles between 25 and 30 are yellow, and angles above 30 are red. At an angle of 30°, slopes are just barely steep enough to slide but they reach peak slide danger at 38°. This only applies to slopes you are standing on, so is less useful than a clinometer. Then take both your poles and put the end of one in the top mark you just made. Slope Angle Shading and Avalanche Forecast. The Silva Expedition S is another reasonably priced compass with a built in clinometer that gets pretty good reviews. It took me a while to get it and I’m pretty decent at math…. This is nice and compact and is useful for measuring slopes that you are on as well as slopes in the distance. I'd imagine geologists and avalanche pros use beta angle quite a bit for things like evaluating how violent a given avalanche could be, or as another way of looking at how steep an avalanche slope is. Required fields are marked *, Avalanche Safety: Terrain Management – Slope Angle. Some of these methods work without setting foot anywhere near the slope in question which is helpful in treacherous conditions. On steeper slopes, the dangling pole will touch the snow further down the slope than the bottom mark. You will also be able to spot potentially dangerous adjacent slopes from a distance and stay well away from them. Slope Angle Maps. Knowing slope angle is a critical factor in assessing avalanche hazard. Neat! Slope Angle and Avalanche Correlation: Because slope steepness directly correlates to avalanche activity, savvy backcountry travelers pay close attention to slope angles. One inexpensive tool that will show you the steepness of a slope is a clinometer (or inclinometer). Every avalanche course teaches that the primary terrain feature of an avalanche start zone is the incline of the slope (a.k.a. Allow the other pole to dangle freely from the other end of the first pole (hold them together loosely with your hands). Terrain management is a skill that is critical to living a long and happy life in the backcountry. Alpha angles for “100 year” avalanches (i.e. The most dangerous range, the sweetspot, is 35-38 degrees. Many higher end compasses have a built in clinometer. Your email address will not be published. Slope Angle – Using an in-built inclinometer SAH gives you a quick and accurate reading of the slope angle. Slope angle (or steepness) is just one aspect of terrain management but is quite an important one to master. Navigating on safe terrain negates the danger of a high hazard snowpack. Always verify angles with a slope meter, and seek proper education before venturing into avalanche terrain. If the angle is less than 30 degrees, it’s typically not steep enough to trigger an avalanche. Use it to your advantage. Don’t take this to mean that deep slab avalanches never occur on really steep slopes. Avalanche forecasting uses many tools to analyze avalanche risk in the field. You don’t need to remember the why. The card presents you with checklists to keep track of present avalanche conditions and to assess the seriousness of individual slopes on your route. Each line on the PoleClinometer sticker is labeled with the angle so you know what the slope angle is. Over 90% of avalanches start on slopes between 30° and 45° degrees. It doesn’t have to be level to take a reading. Training, experience, and judgement are necessary to employ backcountry slope cuts safely. So what do we do with this newfound knowledge of the slope angles all around us? Terrain management is one of the three pillars of avalanche safety along with the snowpack and weather.

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