Tidal Circulation in a Sinuous Coastal Plain Estuary
H. Seim, UNC-CH
J. Blanton, S. Elston, SkIO
Tidal propagation – interaction with the shelf
Residual circulation
Overtides
•Finite Element •Nonlinear•2D (ADCIRC)•Western North Atl.•Crossshelf Amplification•Equatorward phase propagation •Latest phase along GA/FL border
•Shelf response sensitive
NC
SC
FL
GA
M2 Elevation without estuaries – tide experiences two-fold
amplitude increase and notable phase change
m
(B. Blanton)
In the SAB large sections of the coastline are backed by extensive estuaries
(K. Smith, D. Lynch)
depth (m
)
M2 Solution Elevation Difference
Amplitude Ratio Est sol’n Amp-------------------------- > 1 NoEst sol’n Amp
Phase Diff (in red) Est Phase - NoEst Phase>0
(B. Blanton)
Including estuaries increases dissipation >25%...
Strange result – inclusion of highly dissipative estuaries leads to 10% increase in tidal range.
Log10W/m2
Longitude Latitude
(B. Blanton)
Satilla River 1 m tide2-4 m mean depth50 m3/s avg riverflow0.5-1 m/s tidal currentsPristine, typically 2 channel5 km MHHW width, 1km MLW width
Depth-scaling accounts for ~25% of variance – rest due to non-linearities?
M2 phase – earlier in shallow channels, remarkable changes at triple junction
M2+M4 fit reasonable on neap,arger residuals on spring tides
Conclusions
• Damping of propagation appears weak – need to do some simple modeling
• Tidal residual flows strong, structure reminiscent of headland eddies
• Sub-basin exhibits much different behavior
• Overtide generation complex, varies spatially and with time.