Estuaries and Lagoons

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Estuaries and Lagoons
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• Estuaries are inlets of the sea that reach up
  river valleys to the upper limit of tidal rise
  The seaward portion of a drowned valley
  Estuaries only form during sea level rise, or
  where tides shape the coast.
• Lagoons are shallow parts of the sea, partly or
  completely separated from it by a bar or sand
  bank

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Types of estuaries

• Estuaries
• Fjords excavated by glaciers.
• Sea Level Rise Estuaries drowned valleys 11.33
  2 Chesapeake Bay --waves block off a river
  valley.
• Tidal Estuaries

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Environments of Estuaries

• Salt Wedge Fjord or drowned valley
• Partially mixed
• Fully mixed Tidal
• Reverse

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Salt Wedge

• Wave dominated estuaries Drowned valleys
• Barrier and tidal delta
• central Basin
• Bay head Delta

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Tide Dominated Well Mixed

• Tidal Sand Bars
• Upper Sand Flat with Channel
• Upper Muddy
• Tidal flat with channels
• Salt marsh.

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Lagoons

• Highly varying salinity
• Saline lagoons
• Laguna Madre little freshwater input
• Brackish water lagoons Pimlico Sound
• Muddy, highly varied sediments, restricted but
  abundant biota

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