Sneaux - Damage

Damage

When heavy, wet snow with a snow-water equivalent (SWE) ratio of between 6:1 and 12:1 (in extreme cases, as heavy as 4:1) and a weight in excess of 10 pounds per square foot (~50 kg/m2) piles onto trees or electricity lines – particularly if the trees have full leaves or are not adapted to snow – significant damage may occur on a scale usually associated with hurricanes. An avalanche can occur upon a sudden thermal or mechanical impact upon snow that has accumulated on a mountain, which causes the snow to rush downhill en masse. Preceding an avalanche is a phenomenon known as an avalanche wind caused by the approaching avalanche itself, which adds to its destructive potential. Large amounts of snow which accumulate on top of man-made structures can lead to structural failure. During snowmelt, acidic precipitation which previously fell into the snow pack is released, which harms marine life.

There is a popular misconception that snow becomes heavier when it starts to melt, so many people take risks to remove snow from their roofs when the weather starts to get warmer, for fear that the roof will collapse. In fact, when snow starts to melt, its volume decreases as the ice crystals and meltwater move into the spaces between the crystals, which makes the density of wet, melting snow greater than that of freshly-fallen snow. This makes it feel heavier to shovel, but its mass does not increase. In fact, it decreases when meltwater runs off the roof, so the weight of snow on a roof actually decreases when it starts to melt.