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Prepared in cooperation with the
Florida Department of Transportation

Magnitude and Frequency of Floods for Rural Streams in Florida, 2006

By Richard J. Verdi and Joann F. Dixon

ABSTRACT 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 Report PDF (7 MB) PLATE 1—Locations of Flood Regions and Gaging Stations in Florida (1.1 MB PDF) Supplementary Files For additional information contact: Richard Verdi, Hydrologist U.S. Geological Survey 2639 North Monroe St., Suite A-200 Tallahassee, Fla. 32303 850-553-3676 Florida Water Science Center Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.

Suggested citation:

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.

Contents

Abstract

Introduction

Purpose and Scope

Previous Studies

Description of Study Area

Data Compilation

Annual Peak Flows

Basin Characteristics

Estimation of Flood Magnitude and Frequency at Gaged Stations

Log-Pearson Type III Flood-Frequency Analysis

Skew Coefficient

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

Apalachicola River

Suwannee River

Summary

Acknowledgments

References Cited

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