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

Barotropic tides: should be straightforward… Finite Element 2D (ADCIRC) Time-dependent Fully Nonlinear Elev. BCs from Global FES95D Performs well except in SAB (B. Blanton, R. Luettich)

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 M 2 Elevation without estuaries – tide experiences two-fold amplitude increase and notable phase change m (B. Blanton)

Problem: typical coastal tide station is not “in” the typical shelf model domain Fort Pulaski, GA Landward Bndy of Operational models (B. Blanton)

In the SAB large sections of the coastline are backed by extensive estuaries (K. Smith, D. Lynch) depth (m)

M 2 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. Log 10 W/m 2 Longitude Latitude (B. Blanton)

Satilla River 1 m tide 2-4 m mean depth 50 m 3 /s avg riverflow m/s tidal currents Pristine, typically 2 channel 5 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

M 2 +M 4 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.