Scientific Investigations Report 2011–5034
Methods for estimating the magnitude of floods for selected percent chance exceedance probabilities are presented for ungaged streams in Florida that are not substantially affected by regulation, channelization, or urban development. Flood-frequency flows also are presented for 275 Florida streamgages used in the regional regression analysis. Regression relations used generalized least-squares regression techniques to estimate flood magnitude and frequency on ungaged streams as a function of basin drainage area and a storage factor. These regression equations were developed for four different hydrologic regions in Florida. The flood regions were delineated based on plotted residuals, previous flood-frequency studies, and geologic, physiographic, and drainage-area maps. The methods used in this report are based on flood-frequency characteristics for 305 streamgages including 275 in Florida and 30 in the adjacent states of Georgia and Alabama, all having at least 10 years of record through September 2006. For the larger streams outside the limits of the regression equations—the Apalachicola River and Suwannee River at Ellaville and below—the report includes graphical relations of peak flow to drainage area.
First posted May 24, 2011
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Verdi, R.J., and Dixon, J.F., 2011, Magnitude and frequency of floods for rural streams in Florida, 2006: U.S. Geological Survey Scientific Investigations Report 2011–5034, 69 p., 1 pl.
Purpose and Scope
Description of Study Area
Annual Peak Flows
Estimation of Flood Magnitude and Frequency at Gaged Stations
Log-Pearson Type III Flood-Frequency Analysis
Regional Flood-Frequency Regression Analysis
Generalized Least-Squares Regression Analysis
Accuracy and Limitations of Flood-Frequency Estimates
Weighting of Log-Pearson Type III and Regression Analyses
Estimation of Flood Magnitude and Frequency at Ungaged Stations
Sites on Streams that Cross Flood Region or State Boundaries
Comparison with Previous Analyses
Effects of Flood Distribution and Magnitude in the Peak-Flow Dataset
Flood-Frequency Analysis for Large Streams
Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Regions 1–4
Appendix 2. Variance of prediction values for gaging stations used in Florida regional regression analyses
Appendix 3. Flood-frequency estimates using PeakFQ version 5.2