In accreting situations  small mounds of vegetation or tide-washed debris form  and tend to enlarge as the wind-speed drops in the lee of the mound, allowing blowing sand (picked up from the off-shore banks) to fall out of the air stream.
In accretion situations, small mounds of vegetation or tide-washed debris form and grow larger as wind speed decreases in the lee of the mound, allowing sand blown from offshore banks to fall out of the air stream.