1. 하구및 연안생태Coastal management
2015 년 가을학기

2. Water balance (Pritchard, 1952)
positive estuaries : evaporation < freshwater
Negative estuaries : evaporation > freshwater
Neutral : evaporation = freshwater

3. Water balance (Pritchard, 1952)
No loger in common use
Most estuaries are positive!!

4. Geologic classifications(topography)
Coastal plain; Drowned river valley;
most common.
since the last Ice Age, which is within the last 10–15,000 years
V shaped cross sections
Salt marsh estuaries; lack of a major river; estuary-salt marsh connections;

5. Geologic classifications(topography)
Lagoons; Bar-built:
Also drowned river valleys,
but recent sedimentation has kept pace with their drowning so that they have a characteristic bar across their mouths
Shallow 1~2 m
Physical process; wind dominated
80,000 years ago, 6m above present level raised ridge system eroded during glacial period  transformed to bar at present day
Common on all continents

6. Geologic classifications(topography)
Fjord: Drowned glacial troughs.
Fjord-type estuaries occur where valleys have been deeply eroded by glaciation:
West of Scotland, Fjords in Norway, Sweden, Alaska, British Columbia, New Zealand, such as the coasts of Norway, Western Scotland, Alaska, and New Zealand.
Rock bar: 1. can not scour that part because ice began to float 2. scoured material accumulated;
Depth 800m; sill 10~90 m
U-shaped
Fjards: firths; No u-shaped deep basin; shallow; isostatic rebound of the continent due to cessation of ice loading; rebound rates:15 m per 1000 years

7. Geologic classifications(topography)
Tectonic
Fauting, graben formation, land slide, volcanic eruptions
San Francisco Bay
Much variability

8. Circulation
Residence time of a water parcel is function of circulation pattern
“Residence time / biogeochemical turnover” determines degree of hydrodynamic dominance
Flux of all martials (nutrients, pollutants, salt, sediments, detrital matter, plankton) need information regarding circulations
Estuarine bathymetry  circulation
Defined as the residual water movements; short term effects are averaged out

9. Circulation
Residual movements depends on the time scale for averaging; usually 1, 2 tidal cycles
Need systematic measurements over an extended time period.
Time averaged currents make up the circulation: net currents, tidal currents, tidal residuals nontidal flaows

10. Types of Circulation Passive factors : curvature and friction effects
Circulation energy:
solar heating: also contribute to wind, rainfall, SST
Gravitational attraction between moon (sun) and ocean water
Freshwater input : rainfall; major cause
Tide; 3rd important
Wind stress; second major cause
wave; not very important
Passive factors : curvature and friction effects
Geometry
Bathymetry : curvature and friction effects
Ice cover, human activities (dredging, channelization, damming, diversion)

11. Three main driving force
Gravitational circulation :due to fresh water runoff
Tidal circulation
Wind-driven circulation

12. Gravitational Circulation
Induced by density and elevation difference
Mixing with wind + tide
Freshwater: tilt seaward : seaward movement
Seawater: tilt up-estuary: river ward
Equipontential surface: no net movement
Important for residence time calculation: 1 R inflow and 24R exchange
Temperature effects:
in arctic region: cold fresh water will mix with ocean water that makes gravitational circulation
in lagoon: no fresh water input: large evaporation; 90 ppt !: inverse estuarine circulation; usually wind is high and this “inverse circulation” might not be important
Coriolis effects : surface: stronger right side down stream, bottom left side  questionable

13. Tidal circulations “tidal pumping”
Oscillatory: but interact with bathymetry in nonlinear and complex way; spatial velocity gradient
High tidal circulation; Shallow depth + large tidal range
Gravitational and tidal circulation can be equally important
Ebb directed on one side and flood directed other side: because of boundary interaction not because of “Coriolis effects”
No net loss or gain of water but movement of material happens.

14. Wind driven circulations
Important in lagoons; open water, shallow, small tidal range, low fresh input.
Highly variable
However, some circulation can be related with wind
4 x 10-5 radians(0.4 m per 10 km); 10 m/s
“Wind tides” in Texas: period of few hours
Modify gravitational circulation.