Longshore Sediment Movement

Longshore Sediment Movement. Cape May Point State Park. , Most shore bathers soon realize the back-and-forth motion of the waves breaking on the shore not only stirs the sand but also persistently carries them along the beach. This unseen force is called a "longshore" or "littoral" current. In general, the direction of this current along the East Coast is from north to south, although there are many variations., When combined with the turbulence of breaking waves, the current can carry large amounts of sand for miles. The sand is redeposited either at the end of an island or within "inlets," where tidal currents move it in and out of each changing tide. Littoral drift carries an annual average of 200,000 to 300,000 cubic yards of sediment along the mid-Atlantic coast. Storms shift or strip away huge quantities of sediment, especially on steeply-sloped upper beaches. In the end, gravity transfers most beach material to the sea bed., [Captions:] , Atlantic waves continuously reshape the coastal habitats along this section of the Jersey Shore. Littoral drift carries sand southward where it piles up on the north side of the Cold Spring Inlet, blessing the Wildwoods with expansive beaches, while shorelines to the south are sand-starved., Longshore currents are set in motion by the angular approach of waves striking the beach., Background photo shows some of the lost shoreline restored in 2004 through human intervention of beach replenishment. , Photo by: U.S. Army Corps of Engineers, Philadelphia District