East Beach ~ Barrier Beach

Physical Characteristics

What are dunes?

Dunes are hills of sand that create the last barrier protecting the land from the invasion of the sea. This natural barrier is been formed when the wind picks up particles of sand from the barrier beach. A dune begins to form when an obstacle, such as a stone, lies in the wind's path. The obstacle causes the wind to slow down and dump the sand particles it is carrying. As the number of sand particles increase, a hill of sand or a dune is formed. Usually a series of dunes, called a dune field, form. The first dune closest to the beach is also the largest. It's called the primary dune. The windward side of the primary dune is steeper and is called the foredune. This is the side that the wind blows against so that the sand doesn't have a chance to accumulate. The leeward side is sheltered from the wind and sand has the opportunity to build up there. Beyond (landward) the primary dune lies the secondary dunes. These dunes are smaller in size and their sides aren't as steep.

Dunes constantly change if there is nothing to prevent the wind from moving the sand around. The wind doesn't stop moving sand once a dune is formed. If no plants grow on the primary dune, then the wind will remove the sand and deposit it onto the secondary dune until pretty soon there is nothing left of the primary dune. When nothing hold the dune system in place, the dunes move or migrate toward the land. Plants are the primary way dunes are stabilized. Vegetation, such as beach grass, dusty miller, beach peas, and seaside goldenrod keeps the sand in place with their extensive root systems. The roots hold the sand together and the sand on the surface builds up around the plants themselves. You can see how important those dune plants are, so make sure you don't trample them down when you're walking to the beach!