Shoreline Processes

Photo by W. W. Little

Shoreline Processes

Wave Motion

Waves are formed as energy moves through water. Water particles move in a circular pattern, more or less returning their point of origin once the wave has passed.

Photo by W. W. Little

Breaking Waves

As waves approach shallow water, they hit bottom. Due to the resulting friction, the upper part of the wave moves more rapidly than the lower part. Water piles up and the wave breaks, causing water to rush onto the shore. Sediment is moved both by wave base and by surf.

Photo by W. W. Little

Longshore Transport

Waves typically approach the shore at an angle. Upon breaking, their momentum carries sediment onto the beach in the direction of the angle of encroachment until wave energy is spent. Gravity then pulls the wave and sediment seaward, perpendicular to the shoreline. This process carries sediment along the coast in a zig-zag pattern.

Photo by W. W. Little

Surf/Swash

Breaking waves (surf) are capable of transporting large volumes of sediment diagonally landward as part of the beach swash.

Photo by W. W. Little

Swas

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e)Backwash (return flow)

Backwash

Once wave energy has been expended as swash, water and sediment move seaward, perpendicular to the shoreline, as backwash.

Photo by W. W. Little

Photo by W. W. Little

Beach Progradation

Beach progradation is a type of lateral accretion, as beach ridges build basinward through long-shore transport.

Channels

Numerous small fluvial channels flow to the swash zone.

Rip Currents

Water piled against a shoreline by ocean currents must return to sea. It does so by flowing as a stream through breaking waves.

Cause of Tides

Passage of the Moon overhead creates a gravitational bulge that migrates with the Moon’s orbit. An equal bulge is formed concurrently on the opposite side of the earth.

Transgressive vs. Regressive Shorelines

The types of depositional systems that dominate a shoreline differ depending upon whether base-level is rising or falling.