Estuaries
Coastal embayment with important freshwater contribution
Drowned river valleys
Fjords
Embayments formed from human influence (Harbors)
Typically have
Tidal flats and marshes or mangrove swamps
Influence from rivers, tides, and waves (fresh and marine)
Sediment accumulation
Sediment deposition in an estuary depends on relative role of waves, tides and river, but
generally fill in toward the middle of the embayment
Sea level rise/fall can dramatically change the sediment balance in an estuary
Mixing of Sea and Fresh water
Stratified (fresh water floats on salt water)
Mixed (fresh and salt water mix in the estuary)-waves (Outer Banks of N. Carolina) and
strong tidal currents (Bay of Fundy)
Intermediate types
Seasonal Variation and the amount of river water input/storms
Sediment from the river-deposited in Bay Head Delta
Estuaries often have fine-grained sediment unless there is significant wave/tidal current
General Estuary Model
River

Low Salinity
River sediment
Low tidal influence
Low wave influence
Estuary

Mixed
Mix
Low photosynthesis
(suspended sediment)
Tide Dominated
Funnel Shaped
Lack of wave influence
Fully Mixed
Sand accumulates (mud is transported out with the tide)
Marine
35 ppt
Marine sediment
High tidal influence
high wave influence
Wave Dominated
Usually have a barrier across the mouth
Mud is the dominant sediment type
Likely to have stratified water column
Washington/Oregon examples
Pamlico Sound, North Carolina Outer Banks