Estuaries Introduction • General information about Estuaries Estuaries

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Estuaries Introduction • General information about Estuaries Estuaries Powered By Docstoc
• General information about Estuaries.

  Estuaries are unique, ephemeral
  features that are highly productive yet
  easily stressed. Describe estuaries in
  detail and suggest a practical
  classification for them. Thereafter, apply
  this classification to the estuaries of
         What is an Estuary?
• “An Estuary is a semi enclosed coastal
  body of water which has a free connection
  to the open sea, extending into the river as
  far as the limit of tidal influence, and within
  which sea water is measurably diluted with
  fresh water derived from land drainage”
  Dyer 1998.
        South African Context
• “ a coastal body of
  water in intermitted
  contact with the open
  sea and within sea
  water is measurably
  diluted with fresh
  water from land
  drainage” Day 1980.
           Estuary Boundary
• Uppermost inland extension of an estuary is
  where the salinity is below 0.1ppt or dissolved
  ions have a marked difference from sea water,
  sediments are no longer marine or estuarine but
  fluvial and tidal oscillations have faded out.
• Seaward extension, sea water usually has a
  salinity of 35ppt if undiluted by the fresh water
  from the river, fluvial sediments no longer found.
• Estuaries are some of the most productive
• Variety of habitats. eg. soft shores,
• Supports high levels of biodiversity.
• Different organisms eg. fish, shellfish,
  lobsters, marine worms.
• Calm refuge for sea creatures, nurseries
  for breeding. (pelagic fish come to spawn)
• Visiting species (migrating birds)
• Plentiful nutrients, lots of organic matter
  and nutrients washed down from the river.
• Microbial activity has the ability to cycle
  nutrients. Remove pollution, cleaner water.
              SA Coast
• Low Tidal Range. Approx. 2m so on the
  boundary of Micro and Meso Tidal.

• High Wave Energy, therefore has the
  dominant role in most estuaries.
        Estuary Morphology
• Climatic variation and River discharge.
  Seasonal changes cause reduce flows or
  increased flows in a flood event.
• Hinterland gradient and coastal gradient
  will effect erosion activity and where
  sediments are deposited.
• Sediment Supply rates from rivers can be
  affected by dams, sand mining.
• Sediment type and availability.
• Nature and Intensity of Processes highly
• Some estuaries strong seasonal variation.
• Tidal/Wave vs. Fluvial
• Open mouth vs. Closed mouth.
Geomorphological Classification