A simplified hydrodynamics and salt balance model system has been developed for a tidal inlet-costal pond system to predict the consequences of inlet modifications on the inlet flow rate, pond tidal range, and the pond salinity. The hydrodynamics portion of the model solves the momentum and continuity equations for the inlet where the pond behavior is incorporated in the inlet continuity relationship. The salt balance is determined using a tidal prism approach where complete mixing and steady state conditions are assumed. For a single inlet bay system and as sinning no inertial acceleration term or fresh-water inflow, an approximate solution of the governing equations is presented. Extension of the model system to a multiple inlet-bay system, following the computational algorithm developed by Seelig et al, is presented and applied to the Charlestown Pond complex located on the southern Rhode Island coast.