A foredune begins
when vegetation or another obstacle traps wind-blown sand. A small
mound of sand deposited downwind of a plant or clump of vegetation
is called a shadow dune because it forms in the wind
shadow of the vegetation. The wind shadow is the area of little or
no wind that is present downwind of an obstacle.
dunes form downwind of American beachgrass.
(Hoffmaster State Park in July 2002.)