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Beaches - PowerPoint PPT Presentation

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Beaches. What is a beach?. Area along coast where sediment accumulates. Coastal zones begin when waves interact with seafloor. Beaches Shoreline Divisions. Littoral zone. Part of coast that stretches from land plants to where waves start to break. Shoreface. Permanently covered by water.

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What is a beach
What is a beach?

  • Area along coast where sediment accumulates

  • Coastal zones begin when waves interact with seafloor

Beaches shoreline divisions
BeachesShoreline Divisions

  • Littoral zone

  • Part of coast that stretches from land plants to where waves start to break

  • Shoreface

  • Permanently covered by water

  • Foreshore

  • Exposed at low tide and covered at high tide

  • Backshore

  • above mean high tide – only affected by storms

Beaches shoreline divisions1
BeachesShoreline Divisions

Divided by wave action:

  • Breaker zone

  • Where waves become unstable and break

  • Surf zone

  • Shallower waves move up beach face

  • Swash zone

  • alternately covered by “swash” and uncovered by “backwash”

Beaches sediment profile
BeachesSediment Profile

  • Berm

  • Flat-top ridge of backshore

  • Berm crest

  • High point on a beach

  • Beach face

  • Sloping portion of the beach

  • Longshore bars

  • In winter, sediment from berm is transported below breaker zone

Beaches types




Pink sand



Black sand



  • Shape and structure

  • Composition

  • Size

  • Color

Beaches summer and winter



BeachesSummer and Winter

  • Summer

  • Winter

  • Gentle waves

  • Erosive storm waves

  • Carry sand to shore but too weak to carry back to sea

  • Sand carried seaward to offshore sandbars

  • Wide, sandy beach

  • Narrow, rocky beach

Beach processes refraction
Beach ProcessesRefraction

  • Wave crests approach shore at an angle

  • Slows over shallow water

  • Wave bends

  • Wave rays travel perpendicular to wave crest

  • Energy focused on headlands  erosion

Beach processes rip currents
Beach ProcessesRip Currents

  • Incoming waves create underwater sandbar close to shore

  • Waves cause sandbar to collapse

  • Excess water is pushed through gap

  • Creates a strong, narrow current away from shore

Beach processes longshore current and transport
Beach ProcessesLongshore Current and Transport

  • Longshore current moves parallel to shore

  • Longshore transport moves sediment along shore by LS current

  • Zig-zag motion has an overall net transport

  • Swash moves sediment onto beach at an angle

  • Backwash moves sediment down perpendicular to shore

Beach dynamics deposition and erosion

Sandy shore

Rocky shore

Beach DynamicsDeposition and Erosion

  • Deposition

  • Accumulation of sediment

  • Coasts build out by waves and currents

  • Erosion

  • Little incoming sand, usually no major river

  • Sediment is removed

  • Reshaping of coastline by wave action

Beaches depositional features
BeachesDepositional Features

  • Longshore current deposits sand in a line downcurrent

  • Sand spits

  • Bay mouth bars

  • When a sand spit closes off a bay

  • Barrier island

  • Long sand island enclosing a bay or lagoon

Beaches erosional features
BeachesErosional Features

  • Arches

  • Weaker rocks erode



  • Stacks

  • Offshore column formed from collapsed arch

  • Tombolo

  • Sand bar connecting to a rock or offshore outcrop


Beaches erosional features1


Wave cut bench

BeachesErosional Features

  • Wave cut bench

  • Cliff

  • Cliff bottom attacked by waves

  • Waves undercut cliff to form wave cut notch

  • Overhanging rock collapse

  • As cliff retreats, area of flat rock exposed

Beaches erosional features2
BeachesErosional Features

  • Marine terrace

  • If sea level lowers or land uplifted, wave cut bench becomes marine terrace

Beaches human impacts
BeachesHuman Impacts

  • Parallel concrete structures

  • Absorbs wave energy

  • Sea walls

  • Actually promotes erosion

  • Groins

  • Wall perpendicular to shore

  • Stops erosion

  • Erodes downcurrent side

  • Jetties

  • Designed to maintain navigation routes

  • Erosion and deposition

  • Breakwaters

  • Wall parallel to shore

  • Reduce wave energy

  • Interrupts beach drift

Beaches human intervention

Miami Beach



BeachesHuman intervention

  • Beach nourishment

  • Import sand into coastal areas

  • Dredging

  • Underwater excavation to clear waterways