Simulating Hydrodynamics in the Manatee and Braden River Estuaries in Southwest Florida Using a Multi-Block Model

The Manatee River is one of major tributaries of Tampa Bay on the southwest coast of Florida, while the Braden River is a tributary of the Manatee River. Both rivers are impounded by a dam, forming a distinct separation between an estuarine environment and a freshwater environment. To ensure that the downstream segments of the rivers to have a healthy estuarine environment, regulatory freshwater inflow rates for the two rivers need to be established. For this purpose, a modeling study of hydrodynamics in the Manatee and Braden River estuaries was conducted. The model used in the study was a multi-block model that was previously used for simulating hydrodynamics in the Lower Peace River and the Lower Myakka Rivers in southwest Florida. The multi-block model is a dynamically coupled 3D-2DV model. When applied to the Manatee and Braden River estuaries, it splits the simulation domain into one 3D block and seventeen 2DV blocks. The model solves 3D Reynolds-averaged Navier-Stokes (RANS) equations in the 3D block, but laterally averaged RANS equations in the 2DV blocks. The model was calibrated and verified against measured real-time data of surface elevation and salinity at five stations during March 2005 – July 2006. The calibrated model was used to conduct a series of scenario runs to investigate effects of the flow reduction on salinity distributions in the Manatee and Braden River estuaries, before minimum flows for the two riverine estuaries were set.