Development of Two-Dimensional Numerical Model of Hydrodynamics and Salinity for Biscayne Bay, Florida

Abstract

The southern reach of Biscayne Bay (South Bay) is formed by Card Sound, Barnes Sound, and adjacent waters, which experience direct tidal exchange with the Florida Straits through a series of natural inlets into Card Sound. These inlets include Angelfish Creek, Broad Creek, and Caesar Creek (known as the ABC's). Barnes Sound is isolated from direct ocean tidal influence. This southern portion of the bay exhibits a complicated pattern of tidal exchange and wind-driven cur¬ rents. Water can enter and leave this area through any of the several mentioned natural inlets exchanging with the Florida Straits to the east, to the Central Bay to the north, or through Jewfish Creek to Florida Bay to the south. Several small connections from Manatee Bay to Long Sound in Florida Bay also exist through culverts under U.S. Highway 1. The present day salinity of Biscayne Bay is governed by the addition of small volumes, compared to the tidal prism, of fresh water from various sources (pri¬ marily canals, rainfall, and groundwater) combined with the influence of tidal exchange with the Florida Straits through various inlets and channels and winddriven circulation. In general, the isohalines tend to align themselves in a northsouth direction, with the fresher water remaining closer to the western shoreline. The north-south alignment changes with inflow patterns, usually seasonally, with the isohalines shifting seaward or landward, depending on the amount of fresh 2 Chapter 1 Introduction 4 Chapter 1 Introduction Features of present effort Although each of the models previously discussed has merit, there are several features unique to the model presented in this report that make it suitable for the evaluation of freshwater impacts on Biscayne Bay. These include: a. The inclusion of South Bay and North Bay in the model domain. b. The extension of the ocean boundaiy eastward from the Safety Valve to a point several miles offshore, thereby minimizing the impact of boundary effects on the model results (especially salinity results). c. High grid resolution, especially in the nearshore. d. The simultaneous inclusion of groundwater inflow, rainfall/evaporation, and wind in the boundaiy forcing.