Size 2 or Size 3?
20th February 2021
Judging the size of an avalanche can be quite a difficult task. Lets take the avalanche shown above as an example, what size would you estimate it as. Here is my working and result:
Length; in terms of vertical fall distance it ran from an altitude of very roughly 1200 metres down to around 950 metres, giving a fall hieght around 250 metre mark. It’s actual length is probably going to be around 50% or so more, so lets say very roughly 400 metres. This implies somewhere between a size 2 and size 3.
Volume; The debris fan was 58m across where measured, but lets say its average width is around 50 metres. I would say the debris fan is roughly 4 times longer than it is wide, so lets go with a value of 200 metres long. For depth I would say generally between 30cm and 1m, so to make the numbers easier lets say an average value of 50cm. This gives a debris volume of the order of 5000 metres cubed. Again this implies somewhere between a size 2 and size 3.
Destructive power; This avalanche could definitely injure and bury people, but I am not convinced it would bury and destroy cars, destroy a building or damage a truck. Again this implies somewhere between a size 2 and size 3.
These values consistently indicate that this avalanche is between a size 2 and size 3. It might be best described (in my estimation) as a large size 2 avalanche. That is my answer at least, feel free to put your answers, comments or views in the comments section, it is always interesting to get feedback on what we write in the blogs.
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