WRIR 03-4287

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Swain, E.D., Wolfert, M.A., Bales, J.D., and Goodwin, C.R., 2004, Two-Dimensional Hydrodynamic Simulation of Surface-Water Flow and Transport to Florida Bay Through the Southern Inland and Coastal Systems (SICS): U.S. Geological Survey Water-Resources Investigations Report 03-4287, 62 p., 6 pls.


Successful restoration of the southern Florida ecosystem requires extensive knowledge of the physical characteristics and hydrologic processes controlling water flow and transport of constituents through extremely low-gradient freshwater marshes, shallow mangrove-fringed coastal creeks and tidal embayments, and near-shore marine waters. A sound, physically based numerical model can provide simulations of the differing hydrologic conditions that might result from various ecosystem restoration scenarios. Because hydrology and ecology are closely linked in southern Florida, hydrologic model results also can be used by ecologists to evaluate the degree of ecosystem restoration that could be achieved for various hydrologic conditions.

A robust proven model, SWIFT2D, (Surface-Water Integrated Flow and Transport in Two Dimensions), was modified to simulate Southern Inland and Coastal Systems (SICS) hydrodynamics and transport conditions. Modifications include improvements to evapotranspiration and rainfall calculation and to the algorithms that describe flow through coastal creeks. Techniques used in this model should be applicable to other similar low-gradient marsh settings in southern Florida and elsewhere.

Numerous investigations were conducted within the SICS area of southeastern Everglades National Park and northeastern Florida Bay to provide data and parameter values for model development and testing. The U.S. Geological Survey and the National Park Service supported investigations for quantification of evapotranspiration, vegetative resistance to flow, wind-induced flow, land elevations, vegetation classifications, salinity conditions, exchange of ground and surface waters, and flow and transport in coastal creeks and embayments.

The good agreement that was achieved between measured and simulated water levels, flows, and salinities through minimal adjustment of empirical coefficients indicates that hydrologic processes within the SICS area are represented properly in the SWIFT2D model, and that the spatial and temporal resolution of these processes in the model is adequate. Sensitivity analyses were conducted to determine the effect of changes in boundary conditions and parameter values on simulation results, which aided in identifying areas of greatest uncertainty in the model. The parameter having the most uncertainty (most in need of further field study) was the flow coefficient for coastal creeks. Smaller uncertainties existed for wetlands frictional resistance and wind. Evapotranspiration and boundary inflows indicated the least uncertainty as determined by varying parameters used in their formulation and definition.

Model results indicated that wind was important in reversing coastal creek flows. At Trout Creek (the major tributary connecting Taylor Slough wetlands with Florida Bay), flow in the landward direction was not simulated properly unless wind forcing was included in the simulation. Simulations also provided insight into the major influence that wind has on salinity mixing along the coast, the varying distribution of wetland flows at differing water levels, and the importance of topography in controlling flows to the coast. Slight topographic variations were shown to highly influence the routing of water.

A multiple regression analysis was performed to relate inflows at the northern boundary of Taylor Slough bridge to a major pump station (S-332) north of the SICS model area. This analysis allows Taylor Slough bridge boundary conditions to be defined for the model from operating scenarios at S-332, which should facilitate use of the SICS model as an operational tool.



Purpose and Scope
Description of Study Area
Previous Studies
Model Selection and Required Enhancements
Water Level, Currents, and Discharge
Rainfall, Wind and Solar Radiation
Process Studies in Support of Model Development
Model Construction, Calibration, Testing, and Application
Description of Model Structure
Governing Equations
Numerical Solution Technique
Model Input Requirements
Enhancements for Everglades Application
Rainfall as a Time-Varying Point Source
Spatially Detailed Evapotranspiration Calculations
Wind-Sheltering Coefficient
Computational Cells Adjacent to Flow Barriers
Other Code Modifications
Construction, Calibration, Testing, and Application of Flow and Transport Model
Computational Model Domain
Boundary Conditions
Water-Surface Boundary
Lateral Boundaries
Model Parameters
Computational Control Parameters
Wind Coefficients
Frictional Resistance — Vegetation
Flow Coefficient — Coastal Creeks
Dispersion Coefficient
Sensitivity Analysis
Model Application Examples
Flow Estimates at Unmeasured Locations
Water Ponding and Salinity Distribution for Different Inflow and Wind Conditions
Using SICS Model for Restoration Testing
References Cited
Appendix I—SWIFT2D Subroutines Modified for Southern Inland and Coastal Systems (SICS)
Appendix II—Excerpt from Input File Highlighting Areal Gains and Losses

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