Marine Science A100 Lecture Notes - Lecture 10: Longshore Drift, Surf Zone, Beach Nourishment
15 May 2020
School
Department
Course
Professor
Marine Science A100
Manuel Kellogg
Features of Erosional Coastline
● Wave cut notch
● Sea Caves
○ Blowhole
○ Sea arch
■ Sea stack
Shorelines can be straightened by selective erosion
● Marine erosion is usually most rapid on high energy coasts, areas frequently battered by
large waves
● Low energy coasts are only infrequently attacked by large waves
Beaches often have a distinct profile
● A beach is a zone of loose particles that covers a shore.
What are the features of a beach?
Backshore – dunes
● Not influenced by waves or tides but by wind
Foreshore – scarp beach influenced by waves/tides and wind
Nearshore - area of ocean adjacent to land, where waves break
Berms – top of berm is berm crest
Offshore – ocean beyond
Sandy material is…
Shuffled between nearshore and foreshore
● Berm sand can move to longshore bars
Waves transport sediment on beaches
Longshore drift
● A longshore current moves sediment along the shoreline between the surf zone and the
upper limit of wave action.
Currents generated due to wave activity
Longshore current – picks up sediment and transports it = longshore drift and literal drift
Document Summary
Marine erosion is usually most rapid on high energy coasts, areas frequently battered by large waves. Low energy coasts are only infrequently attacked by large waves. A beach is a zone of loose particles that covers a shore. Not influenced by waves or tides but by wind. Foreshore scarp beach influenced by waves/tides and wind. Nearshore - area of ocean adjacent to land, where waves break. Berms top of berm is berm crest. Berm sand can move to longshore bars. A longshore current moves sediment along the shoreline between the surf zone and the upper limit of wave action. Longshore current picks up sediment and transports it = longshore drift and literal drift. Current parallel to the coast and occurs in the nearshore area. Rip currents water that returns to the ocean has too great a volume to join longshore current, so breaks through it. Groin boulders that are placed perpendicular to the shoreline, they block longshore, litteral drift.
