Using a Dynamically Coupled 3D-2DV Model to Simulate Hydrodynamics in the Lower Peace River — Upper Charlotte Harbor System in Southwest Florida

The Peace River, located in southwest Florida, flows southwestward and drains approximately 6213 km² of watershed into Charlotte Harbor, a relatively large estuary in the state. The river is generally meandering and narrow except for its downstream area where the river width varies from several hundred meters to several kilometers. To establish a regulatory freshwater inflow rate for the Lower Peace River, a dynamically coupled 3D-2DV model was developed and used to simulate hydrodynamics in the Lower Peace River — Upper Charlotte Harbor system. The simulation domain includes a 3D sub-domain that consists of the northern portion of Charlotte Harbor and the most downstream 15.5 km of the Lower Peace River and a 2D sub-domain that extends about 43 km further upstream and covers the entire tidal reach of the river. In the coupled model, 3D Reynolds Averaged Navier-Stokes (RANS) equations are solved in the 3D sub-domain, while laterally averaged (2DV) RANS equations are solved in the 2D sub-domain. A free-surface correction (FSC) method is used to solve governing equations in both the 3D and 2D sub-domains. The FSC method is unconditionally stable with respect to gravity waves, wind and bottom shear stresses, and vertical eddy viscosity terms. The use of the FSC method allows both 3D and 2DV equations to be solved simultaneously instead of in sequence. The coupled model was run for a simulation period of about 12.6 months, from June 13, 2003 to July 7, 2004. Model results were compared with measured surface elevations, velocities, salinities, and temperatures at four stations in the simulation domain. Model runs show that the coupled model is very efficient and yields good model results for the complex Lower Peace River — Upper Charlotte Harbor system.