COASTAL DEPOSITIONAL FEATURES

GEOL 1033

DEPOSITIONAL COASTAL LANDFORMSare varied and often associated with each other:

• beaches

• sand bars

• sand spits

• tombolos

• beach ridges

• beach cusps

• cuspate forelands

• barrier islands

• coastal sand dunes

• washover fans

• salt marshes

• tidal flats

• lagoons and bays

• tidal deltas

• river deltas

MAJOR OCEANIC MATERIAL INPUTS

• Input source input amount– Rivers 84%– Glaciers 9%– Windblown dust 3%– Coastal erosion (higher than ave. locally) 1%– Volcanic debris <1%– Groundwater flow <2%

A well-defined, lobate sediment plume is seen emerging from a river source on this stretch of wave-dominated (beach-fronted) Atlantic coastline. Currents are starting to carry some of the sediment northward in the offshore environment. Note the broad, well-"fed" beaches in the direction of sediment transport and narrower, retreated beaches in the opposite direction. Typically, river input and cliff erosion are the

major sources of sediment for a coastline (Space Shuttle, March 1994).

WAVE-DOMINATED NILE DELTA

Maps of some US barrier island coastlines

Plum Island, Mass.Plum Island, northeastern Massachusetts, low altitude, oblique, aerial view of barrier island with beach-dune ridge showing washovers, vegetated backdunes, & back-barrier marsh with tidal channels (16 July 1975).

Sand Spits at the Down Drift ends of Barrier Islands

Beach ridges on a barrier island• McLaughlin's Beach (southwest end of Ninety Mile Beach),

Victoria, Australia Recent Low altitude, oblique, aerial view of low-angle truncation of multiple beach-dune ridges (chenier ridges). This once prograding coastline was retreating, at least locally when this picture was taken (1976).

Development on a Barrier IslandOcean City, Maryland, U.S.A.Modern Beach island modification: Ocean City, a developed barrier island. Host to 8 million visitors a year, this city (and others similarly situated) has no effective protection against

flooding and damage from severe storms.

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