What is the difference between snow drift and snow sliding?

[GalileoG]

I thought they were always the same, but the Canadian Code distinguishes between both and requires a 50% increase in snow drift values to account for snow sliding. Can anyone clarify please?

 

[geoffdale]

A snow drift is basically when you have an obstruction such as a higher roof that is flat. If this roof has a slope to it, and snow can slide off of this roof onto the lower roof, that is sliding snow.

 

[GalileoG]

Gotcha. Thanks.

 

[SteveGregory]

Drifting occurs at obstructions such as a large air handling unit or screen wall, at parapet walls and at the wall between a high roof and a low roof.

Drifts can be formed from windward or leeward winds. The upper and lower roof surfaces can be sloped or level.