File:Corner snow drift (5289823749).jpg

Of course Marcel Minnaert has something to say about this observation:

162. Dead leaves. Autumn is the time par excellence for studying air currents and the dry leaves that - in their millions whirl all along the roads, are very sensitive wind-indicators. In every ditch, every slight depression of the terrain - eve if it's only an undulation of a few centimeters deep! - the withered leaves accumulate. At such points, the wind has to be significantly weaker. Other accumulations occur where the air rises temporarily, so that the horizontal component of the airflow is small. Thus one finds sometimes a big pile of leaves in the recessed corner of a building, caused by the whirling ascent of air there.

And look at ribbons of autumnleaves that you can find along any sidewalk and along each wall: as the wind comes closer to the wall the horizontal component of the airspeed decreases and the wind will first drop the sand and only ater that the withered leaves.