Deltas and Estuaries

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Deltas and Estuaries

• Lecture D

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Delta

• Sediment washed out of rivers protruding from
  shore.
• River dominated delta
• Wave dominated delta
• Tide dominated delta

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Delta types
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Growth of a river dominated delta
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Growth of deltas
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River Dominated Delta

• Example Mississippi River
• Low energy coastline
• Microtidal
• Strong river current

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River Dominated

• Delta Plain-
• Delta front-
• Prodelta-

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Wave Dominated Delta

• Example Sabine River (western Louisiana)
• High energy coastline
• Usually small river
• Sediment and sand carried away by currents and
  waves
• Few interdistributary area, tidal flats, or salt
  marshes

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Tide dominated

• Low energy coastline
• Macrotidal
• Funnel shaped mouth
• Sand bars parallel to river current
• Caused by strong tidal currents
• Example Colorado River

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Tide dominated

• Tide-dominated deltas are characterised by
  relatively high tide energy at the mouth compared
  with wave energy, and are distinguished from
  tide-dominated estuaries by high river energy.
• Tidal energy is greatest slightly landward of the
  mouth due to constriction by the funnel shaped
  mouth.
• Wave energy is dissipated on shoals seaward of
  the mouth, and declines rapidly landwards.
• River energy remains moderate to high along the
  channel, but drops off significantly as the
  channel widens towards the mouth.

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Tide dominated
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Estuaries

• Habitats Estuaries - Characteristics
• Estuaries are partially enclosed bodies of water
  where freshwater (water without salt) meets salty
  ocean water. Bays, inlets and ocean-flooded river
  valleys are all examples of estuaries.
• Estuaries are divided into four types, depending
  on how they are formed
• 1. Coastal Plain Estuaries are formed by the sea
  level rising and filling an existing river
  valley. Examples of this are the Chesapeake Bay
  in Maryland and the harbor in Charleston, South
  Carolina

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Estuaries

• Partially enclosed bay of water with an influx of
  both freshwater from a river(s) and salt water
  from the sea. The fresh and salt waters mix
  providing an area of remarkable biological
  productivity.
• http//www.onr.navy.mil/focus/ocean/habitats/estua
  ries1.htm

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Estuaries nurseries of the sea

• Between 90 and 97 of all commercial fish caught
  in Florida live in the estuary at some time of
  their lives

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Sediment

• As sediment sinks, they are geologically
  shortlived estuaries are
• varied,
• fragile,
• nutrient rich,
• productive,
• and threatened.

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Osmoregulation

• Sea cucumber
• Salmon
• Oysters
• Blue crabs

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estuaries

• Habitats Estuaries - Characteristics
• Estuaries are partially enclosed bodies of water
  where freshwater (water without salt) meets salty
  ocean water. Bays, inlets and ocean-flooded river
  valleys are all examples of estuaries.
• Estuaries are divided into four types, depending
  on how they are formed
• 1. Coastal Plain Estuaries are formed by the sea
  level rising and filling an existing river
  valley. Examples of this are the Chesapeake Bay
  in Maryland and the harbor in Charleston, South
  Carolina