Question about ECT test and slope angle

[Kai]

I've heard/read conflicting information regarding the importance of slope angle in Extended Column Testing.

Some have said that you should select a slope angle for your test pit that approximates the slope of the ski line you are considering skiing.

Some have said that the slope of the terrain underlying the pit is irrelevant because the behavior of the isolated column is independent of slope angle.


Wondering what the conventional wisdom is on this issue.

[I've seen black diamonds!]

https://avalanche.org/wp-content/upl...T_SlopeAng.pdf

"From a practical perspective, our results show that, as long as the snow structure remains reasonably consistent in space, observers can conduct dependable tests on persistent weak layers such as surface hoar in gentler, safer terrain before committing themselves to more exposed areas. Of course, it is still critically important for observers to carefully assess whether or not the snowpack structure in that lower angled terrain is sufficiently similar to the snowpack structure on the surrounding steeper slopes. The bottom line for avalanche practitioners is that being able to conduct at least some initial tests in safer locations has the potential to greatly increase the safety of stability assessments. In conclusion, the answer to the title question is ‘yes’ if the goal is to collect ECT data on a persistent weak layer such as surface hoar, and the snowpack in the test area is consistent with that on the slopes. "

[Arctos Guides]

I've heard/read conflicting information regarding the importance of slope angle in Extended Column Testing.

Some have said that you should select a slope angle for your test pit that approximates the slope of the ski line you are considering skiing.

Some have said that the slope of the terrain underlying the pit is irrelevant because the behavior of the isolated column is independent of slope angle.


Wondering what the conventional wisdom is on this issue.

https://avalanche.org/wp-content/upl...T_SlopeAng.pdf

The big take away is the need to pick out a representative test profile site. You’re looking to test a layer’s propensity to propagate with an ECT, thus you want to make sure the layer of concern exists in the test site.

Ultimately, a major yellow/red flag is the existence of a PWL on the slope you want to ski. Personally, I’d put more weight in the existence of a PWL than a ECTX or ECTP 28; meaning if the layer is observed and within human triggering depth, I probably go ski elsewhere.

Basing a decision to ski a slope on a fracture character or lack of propensity to propagate isn’t sound decision making. Gathering observations over the course of the day on representative terrain (such as hand shears, breaking trail etc) carries significantly more weight than one data point (ECT result).