This project uses Computational-Fluid-Dynamics (CFD) to study Marine-Hydro-Kinetic (MHK) turbine arrays at a geo-physical scale, where turbulent wakes of MHK turbines can interact with estuary-scale flow dynamics. Secondary flows generated by bathymetric features can impact the survivability and efficiency of MHK turbines; and likewise, MHK turbine arrays can alter the aquatic environment. Mesoscale CFD simulations are performed via solutions of the Reynolds-Averaged Navier-Stokes (RANS) equations to capture the combined flow features generated by the coupling of bathymetry-induced flow and tidal turbine wakes. The objectives are: (1) to nest CFD simulations of the MHK turbine array environment (using the STAR-CCM+ code) within the estuary-scale flow (simulated by RegionalOcean-Modeling-System, ROMS) for scenarios of hydrokinetic turbine power plant, and (2) to compare pre-installation and post-installation conditions. This study aims to inform the design of efficient, robust, and environmentally friendly large-scale arrays of tidal turbines.