On sand dune systems, wind is extremely important. It is the agent by which sand is moved, from where it has been deposited by the sea on the beach, inland. A detailed and excellent account of these processes is given here.

Essentially, wind speeds of as low as 5 metres per second are enough to pick up grains and, by a process of saltation, where the grain falls back to earth and kicks up others, this can lead to significant sand grain movement. A film of this happening can be seen at the link here.