Waves exert significant influence on the formation and morphology of barriers. It is believed that waves contributed to the formation of some barriers along the Atlantic and Gulf coasts by re-working bottom materials into sand bars, which eventually built above sea level to become barriers.
Storm waves lead to overwash and inlet formation. Overwash occurs when extreme storm waves push sediment from the ocean side to the bay side of a barrier, thereby extending the island landward. Inlet formation takes place when waves and storm surges, along with wind, cut an inlet through a narrow point on a barrier. This leads to the formation of a flood-tidal delta and, eventually, new marsh on the barrier's bay side. These processes are critical to prevent the inundation of a barrier feature.
Waves also cause seasonal erosion and accretion on barriers. High-energy waves in winter erode sand and deposit it in sand bars. Low-energy waves in summer then push the sand back onto the shore.