MODELING FLUSHING AND MIXING IN A DEEP ESTUARY

The distribution of constituents from discharges in estuaries can be d etermined only to the detail with which the time-varying velocity held is known. Deep estuaries can exhibit complex vertical and horizontal circulation structures depending on tides, freshwater inflows, density stratification, and geometry. A numerical, time-varying, three-dimens ional hydrodynamic and transport model is applied to the Gastineau Cha nnel, a deep estuary in Alaska, to determine the dilution of material discharged from a submerged outfall into the Channel. The ability of t he model to produce realistic flow fields is first confirmed by compar ing computed velocities to measured velocities for stratified and unst ratified conditions. Methods are then shown for determining the hushin g rate of the estuary and the distribution of dilution throughout the estuary for these same conditions.