Comments:
Dynamic analysis time series of current and sealevel measurements shows that the principal force balance is between the frictional stress and the pressure gradient frocing (Swift and Brown, 1983). Hence, the kinematic assumption is confirmed. The computational grid, named gbes4 for the Great Bay Estuary system is created using linear equilateral triangles fitted to the shoreline boundary. There are 22140 nodes and 39617 elements. The bathymetric depth contour reveals a center channel running from Portsmouth Harbour through lower Piscataqua river to the Little Bay and Great Bay areas.There are big tidal flats in the Great Bay-Little Bay area and along the shorelines of Fox Point area, Upper Piscataqua River and Bellamy River.

M2 tidal forcing is specified as a Dirichlet elevation boundary condition at the mouth across the Portsmouth Harbour. The amplitude is found to be 1.35m by extrapolating the field data we have at various tidal stations from (Swift and Brown, 1983). The simulation was started with fluid at rest and was terminated after five M2 tidal period (62.10hrs). The simulation setup is given below. All the simulation parameters are summarized in Table below.

Comments:
Time history of the total fluid volume and the cumulative transport across four selected transects as shown in gbes4 show the system establishes a dynamic equilibrium rapidly, and mass conservation is thereafter maintained throughout the simulation after the initial tidal period. The maximum normal velocity across the transects increases then decreases as one moves southward with maximum level across the middle strait, while the normal transport across the same transects decreases to maintain mass conservation. Both quantities decreases sharply at the two tidal flat cuts. It is noticed that asymmetry exists between flood and ebb.

Residual transport:

Comments:
Residual transport vectors are directed inward along the shore boundary and the shoreline tidal flats and return outward throuh the deeper channel. gbes4-gb-hv.gif shows there is a counter clockwise gyre around a pit at the middle part of the channel just inside the Little Bay area. This causes residual transport out of the inlet at its middle portion. Simulation results indicates that the residual bottom stress is intensified within the channel especially at narrow straits. With M2 forcing, the residual sediment transport is observed to be the most intense near the narrow strait directed southward at Adams Point.

Comments:
The above transient solutions are numerically well-behaved and appear to describe the realistic dynamics of the tidal flooding and dewatering process in this complex domain.