Restoration and management decisions about the south Florida ecosystem are based in part on the results of numerical surface-water models. Model results are sensitive to the expressions used for vegetative flow resistance and to the values of the coefficients that appear in these expressions. U.S. Geological Survey (USGS) hydrologists and ecologists are conducting studies to quantify vegetative flow resistance to improve numerical models of surface-water flow. For use in the models, vegetative flow resistance must be expressed in terms of parameters describing the flow and the vegetation. These parameters include the flow velocity through the vegetation, the water depth, the slope of the water surface, and the type, geometric characteristics, and density of the vegetation.

Both indoor flume and field measurements are being conducted to develop methods for evaluating the resistance of relatively uniform stands of vegetation and to identify the most appropriate parameters for representing resistance due to vegetation types typically found in the Everglades. By using computer models, remote-sensing techniques, and geographical-information-system tools, empirical expressions will be developed to define flow resistance in areas of mixed vegetation of variable density. Such expressions will quantify flow resistance at scales appropriate for large-scale hydrodynamic models or regional hydrologic models. These expressions for flow resistance will be tested by comparing results from computer flow models with measurements in selected areas of the Everglades.

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