Mixed-Energy Barriers

Mixed-Energy Barriers

Mixed-energy barrier island systems are typically short and wider at one end than the other end. Historically, this type of morphology has been referred to as a drumstick barrier island because of its approximate similarity in shape to the drumstick of a chicken leg. The tidal inlets between these barriers are large because of the relatively higher tidal energy. Compared to wave-dominated barriers, they also have large ebb-tidal deltas because the strength of the tidal currents is able to transport sediment seaward in a regime of relatively low wave energy. The relatively wider end of the island is the result of the accretion of sediment as waves refract around the edge of the ebb-tidal delta, causing a localized reversal in the longshore transport pattern and leading to sand accumulation.

Several hundred kilometers farther south of the North Carolina coast along the eastern U.S.A is the coast of the state of Georgia with barrier islands that are different from the barrier systems of North Carolina. Because the Georgia barrier islands here are in a mixed-energy environment, waves are not the dominant forcing mechanism of coastal change, and the barriers are shorter with more tidal features such as closely spaced tidal inlets that allow the exchange of large volumes of seawater between the backbarrier and open ocean.

Credit: NASA