U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the 

Florida Department of Transportation

Magnitude and Frequency of Floods 

for Rural Streams in Florida, 2006

Scientific Investigations Report 2011–5034
Front cover:

Large photograph: USGS hydrographer Mark Stephens 

measuring streamflow over the road at Withlacoochee River 

near Pinetta, Florida, using acoustic Doppler current profiler 

during the flood of April 2009. Photograph by Erik Ohlson, 

USGS, April 8, 2009.

Small photograph: USGS hydrographer Erik Ohlson measuring 

streamflow through a culvert on Highway 90 at the Suwannee 

River at Ellaville, Florida, gage during the flood of April 2009. 

Photograph by Rachel Pawlitz, USGS, April 11, 2009.
Magnitude and Frequency of Floods 

for Rural Streams in Florida, 2006

By Richard J. Verdi and Joann F. Dixon

Prepared in cooperation with the 

Florida Department of Transportation

Scientific Investigations Report 2011–5034

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2011

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reproduce any copyrighted materials contained within this report.

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.

9781411331013
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................1

Previous Studies ...................................................................................................................................1

Description of Study Area ...................................................................................................................2

Data Compilation............................................................................................................................................4

Annual Peak Flows ...............................................................................................................................4

Basin Characteristics...........................................................................................................................4

Estimation of Flood Magnitude and Frequency at Gaged Stations .......................................................5

Log-Pearson Type III Flood-Frequency Analysis.............................................................................6

Skew Coefficient...................................................................................................................................6

Regional Flood-Frequency Regression Analysis.............................................................................7

Generalized Least-Squares Regression Analysis ...........................................................................7

Accuracy and Limitations of Flood-Frequency Estimates .............................................................8

Weighting of Log-Pearson Type III and Regression Analyses....................................................10

Estimation of Flood Magnitude and Frequency at Ungaged Stations.................................................12

Sites on Streams that Cross Flood Region or State Boundaries ................................................13

Comparison with Previous Analyses...............................................................................................13

Effects of Flood Distribution and Magnitude in the Peak-Flow Dataset.............................................14

Flood-Frequency Analysis for Large Streams.........................................................................................15

Apalachicola River..............................................................................................................................16

Suwannee River..................................................................................................................................17

Summary........................................................................................................................................................19

Acknowledgments.......................................................................................................................................19

References Cited..........................................................................................................................................19

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Regions 1–4 ............................22

Appendix 2. Variance of prediction values for gaging stations used in Florida regional 

regression analyses...............................................................................................................................58

Appendix 3. Flood-frequency estimates using PeakFQ version 5.2 ..........................................................69

Plate

1. Locations of hydrologic flood regions and gaging stations in Florida .............back pocket

Figures

1. Map showing the location of the study area and ecoregions in Florida.............................3

2–4. Graphs showing—

2. Distribution of drainage area and storage for the four hydrologic regions in Florida ....10
iv

3. Relation of flood streamflow to drainage area for selected streamgaging stations 

and P-percent chance exceedance for the Apalachicola River in Florida.......................16

4. Relation of flood streamflow to drainage area for selected streamgaging stations 

and P-percent chance exceedance for the Suwannee River in Florida...........................17

Tables

1. Basin characteristics considered for use in the regional regression analysis .................5

2. T-year recurrence intervals with corresponding annual exceedance probabilities 

and P-percent chance exceedance for flood-frequency discharge estimates.................6

3. Regression equations for geographic regions in Florida.......................................................9

4. Valid ranges of basin characteristics for the regional regression equations..................10

5. Comparison of Bulletin 17B flood-discharge estimates from this investigation with 

Bulletin 17 or Bulletin 17A estimates from previous investigations ...................................12

6. Comparison of regression equation flood-discharge estimates from this 

investigation with regression equation flood-discharge estimates from previous 

investigations ..............................................................................................................................13

7. Comparison of weighted flood-discharge estimates from this investigation with 

weighted estimates from previous investigations ................................................................14

8. Comparison of weighted flood-discharge estimates from this investigation with 

weighted estimates from the Bridges (1982) investigation..................................................15
v

Conversion Factors and Datums

Inch/Pound to SI

Multiply By To obtain

Length

inch 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 2.590 square kilometer (km2) 

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

Hydraulic gradient

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows: 

°C = (°F – 32) / 1.8

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 29).

Horizontal coordinate information is referenced to the North American Datum of 1983 

(NAD 83).

Elevation, as used in this report, refers to distance above the vertical datum.

Abbreviations and Acronyms

DEM Digital Elevation Models

GIS Geographic Information System

GLS generalized least squares

NED National Elevation Dataset

NHD National Hydrography Dataset

QA/QC quality assurance and quality control

R2 root mean square error, coefficient of determination

USGS U.S. Geological Survey
Abstract

Methods for estimating the magnitude of floods for 

selected percent chance exceedance probabilities are 

presented for ungaged streams in Florida that are not sub

stantially 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 floodfrequency studies, and geologic, physiographic, and drainagearea maps. The methods used in this report are based on floodfrequency 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. 

Introduction

Engineers rely on flood-frequency statistics to aid in the 

design and location of bridges, culverts, embankments, dams, 

and other structures near streams and rivers. These data are 

required for flood-insurance rates and for flood-plain management (Hedgecock and Feaster, 2007).

The Florida Department of Transportation needs accurate 

flood-frequency information to efficiently design bridges and 

drainage structures in Florida. To meet this need, the U.S. 

Geological Survey (USGS), in cooperation with the Florida 

Department of Transportation, conducted a study to update 

previous flood-frequency estimates given in several reports 

based on peak-flow data collected through September 2006 

from streamgages (modified from Hedgecock and Feaster, 

2007).

Purpose and Scope

The purpose of this report is to update previously 

published flood-frequency information for Florida by providing methods for estimating the magnitude and frequency of 

floods at ungaged streams. The report also presents frequency 

estimates of peak flow using data collected through September 2006 at streamgages. This report includes: (1) regional 

equations for estimating the magnitude and frequency of peak 

flows on rural ungaged streams in Florida; (2) estimates of the 

magnitude of floods at the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 

0.2-percent chance exceedance levels for 305 streamgages in 

Florida, Georgia, and Alabama; (3) techniques used to develop 

regression equations to estimate the magnitude of floods on 

rural ungaged sites in Florida; (4) the accuracy and limitations 

of these equations; (5) example applications of the methods; 

and (6) comparisons of the data and results in this report with 

previously published studies.

Previous Studies

This report supersedes previous USGS reports estimating 

the magnitude and frequency of flooding in Florida. Earlier 

USGS studies describing flood-frequency relations throughout 

the State include reports completed by Pride (1958), Barnes 

and Golden (1966), Rabon (1971), Seijo and others (1979), 

Bridges (1982), Giese and Franklin (1996), and Hammett and 

DelCharco (2005). Most of the general organization, content, 

equations, and explanatory material contained within this 

Florida report are consistent with the discussions and language 

used for three similar reports from Alabama (Hedgecock and 

Feaster, 2007), Georgia (Gotvald and others, 2009), and South 

Carolina (Feaster and others, 2009). Data and additional 

discussion unique to the magnitude and frequency of floods in 

Florida have been inserted where applicable with the original 

USGS report sources accredited or shown as “modified from.”

Pride (1958) conducted a study estimating and regionalizing floods in Florida using peak-flow data through 1953 based 

on calendar year from 146 streamgages. Flood-frequency 

relations for the 146 streamgages were defined by graphical 

means. The State was divided into two flood regions based on 

Magnitude and Frequency of Floods for 

Rural Streams in Florida, 2006

By Richard J. Verdi and Joann F. Dixon
2 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006

geometric similarities in flood-frequency graphs. Composite 

frequency curves were developed for both regions that defined 

ratios to determine recurrence intervals up to the 2-percent 

chance exceedance probability (50-year flood) based on the 

mean annual flood for that station. Pride (1958) recognized 

that flood-water storage in lakes and marshes could substantially lower flood magnitudes at some locations; thus, Pride’s 

study included a method for adjusting flood magnitudes by 

accounting for attenuation resulting from flood-water storage 

in drainage areas upstream from selected streamgages.

Barnes and Golden (1966) analyzed flood-frequency 

relations throughout the United States based on peak flows 

for each water year (October 1 through September 30) 

through 1961. The evaluation included streamgages from all 

of Florida, and parts of Mississippi, Alabama, and Georgia. 

There were 132 streamgages in Florida used in this analysis, and each streamgage had 5 or more years of record. The 

method and technique employed by Barnes and Golden (1966) 

was similar to the one used by Pride (1958) and is commonly 

referred to as the index-flood method (Dalrymple, 1960). 

Barnes and Golden (1966) subdivided the southern Atlantic 

and eastern Gulf of Mexico States into four hydrologic flood 

regions. Florida was included in all four regions. Flood flows 

for up to the 2-percent chance exceedance probability (50-year 

flood) were determined, as well as methodology for reducing flood flows for drainage areas where lakes and swamps 

provide water storage.

Rabon (1971) made the first attempt to use 

multiple-regression analysis as a way to regionalize floodfrequency relations in Florida. Rabon’s investigation used 

145 streamgages throughout the State with a variety of flow 

characteristics, such as average and low flows and each had 

a minimum of 10 years of record. The annual peak flows for 

the period of record up to water year 1970 for each gage were 

mathematically fitted to a log-Pearson Type III distribution 

curve as a means to estimate magnitudes and frequencies 

of floods up to the 2-percent chance exceedance probability 

(50-year flood). Rabon subdivided Florida into two hydrologic 

flood regions.

Seijo and others (1979) evaluated peak flows from 

64 streamgages throughout west-central Florida using the 

guidelines set forth by the U.S. Water Resources Council 

(1976) in Bulletin 17. A Pearson Type III distribution curve 

was fitted to the logarithms of annual peak-flow data for the 

period of record through 1976 for each streamgage. Westcentral Florida was subdivided into three flood regions, and 

flood-frequency equations were developed for each region 

using multiple regression analysis. Seijo and others (1979) 

reported the average standard error of estimate of the regional 

equations was 43.5 percent. 

Bridges (1982) evaluated annual peak-flow data for 

the period of record through water year 1978 for each of the 

182 streamgages considered throughout Florida. Of the 182 

streamgages evaluated, 159 were long-term streamgages with 

10 to 53 years of record and the remaining 23 streamgages 

were rainfall-runoff streamgages with 7 to 17 years of record. 

Bridges’ (1982) analysis used guidelines presented in U.S. 

Water Resources Council (1977) Bulletin 17A. Multipleregression analysis was used to develop equations for three 

geographic regions for Florida. Three basin characteristics 

within Regions A and C were determined to be statistically 

significant in describing the variability in flood flows: (1) 

contributing drainage area, (2) channel slope, and (3) the 

percentage of drainage area covered by lakes. Two basin 

characteristics were determined to be statistically significant 

in describing the variability in flood flows for Region B: (1) 

contributing drainage area and (2) the percentage of drainage 

area covered by lakes. The average standard error of estimate 

for the regional equations as developed by Bridges (1982) was 

56 percent.

Giese and Franklin (1996) updated the flood-frequency 

relations for 32 streamgages in the boundaries of the Suwannee River Water Management District using period-of-record 

annual peak flows through water year 1994. Their analysis followed guidelines presented in U.S. Water Resources Council 

(1982) Bulletin 17B to generate log-Pearson Type III distribution curves for each gage. The assumption was made that the 

regional regression equation for area of study in the District 

was the same as presented in report by Bridges (1982). The 

average standard error of estimate of the regional equation for 

this region as developed by Bridges (1982) and used by Giese 

and Franklin (1996) was 62 percent.

Hammett and DelCharco’s (2005) investigation 

evaluated annual peak flows from 94 streamgages in westcentral Florida; 75 of the streamgages were within the 

boundaries of the Southwest Florida Water Management 

District and the remaining 19 were along the border. Data for 

each streamgage consisted of at least 10 years of record and 

included period-of-record annual peak flows through water 

year 2001. Similar to the Giese and Franklin (1996) study, 

Hammett and DelCharco (2005) followed guidelines presented 

in U.S. Water Resources Council (1982) Bulletin 17B in their 

analysis to generate log-Pearson Type III distribution curves 

for each station. Additionally, they used multiple-regression 

analysis to develop equations for four regions in west-central 

Florida. Three basin characteristics were determined to be 

statistically significant in describing the variability in flood 

flows throughout regions 2, 3, and 4 in west-central Florida: 

(1) contributing drainage area, (2) channel slope, and (3) 

the percentage of drainage area covered by lakes. Two basin 

characteristics that were statistically significant in describing 

the variability in flood flows throughout Region 1 are: (1) 

contributing drainage area, and (2) the percentage of drainage 

area covered by lakes. The average standard error of prediction for the regional equations as developed by Hammett and 

DelCharco (2005) was 58 percent.

Description of Study Area

This study included all of Florida and covered an area 

of approximately 58,560 square miles (mi2) within three U.S. 
Introduction 3

Environmental Protection Agency level III ecoregions—

Southeastern Plains, Southern Coastal Plain, and Southern 

Florida Coastal Plain (fig. 1; Griffith and others, 2008). The 

ecoregions in Florida represent areas of general similarity in 

ecosystems and in the type, quality, and quantity of environmental resources. Additionally, these ecoregions provide a 

spatial framework for research, assessment, management, and 

monitoring of ecosystems and their components. The relatively flat topography of Florida ranges from sea level to the 

highest known natural point of 345 feet (ft) at Britton Hill near 

Paxton (Walton County in northwest Florida, fig. 1). Hills and 

rolling hills are the predominant features in the panhandle and 

northern parts of the State, whereas the swamps and wetlands 

of the Everglades prevail in the south (Pride and Crooks, 

1962). The wide range of water bodies in Florida include 

thousands of lakes and ponds, more than 50 river systems, 

33 first magnitude springs (flow greater than 100 cubic feet 

per second (ft3/s), more than any other state), and numerous 

bays and estuaries. The St. Johns River is the longest river 

in Florida, measuring 273 miles (mi) in length. Water bodies comprise 4,424 mi2

 of the 58,560 mi2 total area of Florida 

(Florida Office of Cultural and Historical Programs, [undated], 

accessed August 30, 2005, at http://dhr.dos.state.fl.us/facts/

stats/quick/). Replenishment of the water bodies occur in 

multiple ways, but most often from rainfall runoff. Other 

replenishment sources are flow from the upward movement 

of groundwater springflow into surface streams, including 

some that originate in Georgia or Alabama. Water loss occurs 

through evaporation, transpiration, water use, and flow into 

the Gulf of Mexico or the Atlantic Ocean (Pride and Crooks, 

1962).

Level III ecoregion

Level IV ecoregion

State boundary

County boundary

EXPLANATION

65f

65g

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75a

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Southeastern Plains

Southern Pine Plains and Hills

Dougherty Plain

Tifton Upland

Tallahasee Hills/Valdosta Limesink

Southeastern Floodplains and Low Terraces

Southern Coastal Plain

Gulf Coast Flatwoods

Southwestern Florida Flatwoods

Central Florida Ridges and Uplands

Eastern Florida Flatwoods

Sea Island Flatwoods

Okefenokee Swamps

Floodplains and Low Terraces

Sea Islands/Coastal Marsh

Gulf Barrier Islands and Coastal Marshes

Big Bend Coastal Marsh

Southern Florida Coastal Plain

Everglades

Big Cypress

Miami Ridge/Atlantic Coastal Strip

Southern Coast and Islands

Okefenokee Plains

0 20 40 MILE

Albers equal area projection

SCALE 1:940 000

0 20 40 KILOMETER

65f

65g

75a

65f

65o

65h 75g

75e 75f

75j

75c

75d

75b

76a

76c 76b

76d

65p

65f 65p

65p

65f 75i 75a

75i

75i

75i

75a 75i

75a

75k

75k

75k

75k

75l

75l

Tallahassee

Gainesville

Miami

Orlando

Tampa

Jacksonville

Lake

Okeechobee

Key West

Britton Hill

Figure 1. Location of the study area and ecoregions in Florida.
4 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006

Data Compilation

The first step in the regionalization of flood-frequency 

estimates for streams is the compilation of all peak-flow data 

from streamgages with at least 10 years of annual peak-flow 

record. The annual peak-flow record is reviewed for quality 

assurance and quality control (QA/QC) and for homogeneity, 

which implies relatively constant watershed and climatic conditions during the period of record. Once peak-flow records 

are compiled and reviewed, basin characteristics must be 

determined for each streamgage. 

Annual Peak Flows

Annual peak flow is the highest instantaneous flow 

recorded at a site for an independent flood event during the 

water year. Occasionally, the annual peak flow is not the maximum for the year. In such cases, the maximum flow occurs at 

midnight at the beginning or end of the water year, on a recession from or rise toward a higher peak in an adjoining water 

year. 

Streamgages with annual peak-flow record are either 

continuous-record or crest-stage stations. At continuousrecord stations, measured parameters, such as the surfacewater elevation (or stage) of a stream are recorded at fixed 

time intervals, typically at 15-, 30-, or 60-minute intervals. At 

crest-stage stations, only the highest stage that occurs between 

site visits is recorded. Regardless of the type of gage, measurements of flow are made by field personnel throughout the 

range of recorded stages, and a relation between stage and 

flow (known as a rating) is developed for the streamgage. This 

rating is used to determine flows for all recorded stages at a 

streamgage.

Streamgages in Florida and in adjacent parts of Alabama 

and Georgia that monitor Florida streams were evaluated for 

possible inclusion in this investigation. Streamgages were 

only considered for the analysis if 10 or more years of peakflow data were available in the record, and if peak flows were 

not substantially affected by trends, dam regulation, floodretarding reservoirs, tides, urbanization, or channelization. 

These stations were then reviewed for QA/QC using the tests 

as outlined in Ryberg (2008). The QA/QC analysis determined 

that 305 stations were appropriate for the study, consisting of 

275 in Florida, 21 in Georgia, and 9 in Alabama.

Basin Characteristics

Peak-flow information can be estimated for ungaged 

locations through multiple-regression analysis that relates 

peak-flow characteristics (such as the 1-percent chance 

exceedance flow) to selected physical and climatic basin 

characteristics for gaged drainage basins. Basin characteristics 

for this study were generated using geographical information 

system (GIS) techniques. Basin boundaries were determined 

from the National Elevation Dataset (NED) Digital Elevation 

Models (DEMs) at 10-meter horizontal resolution (U.S. Geological Survey, 1999a). To improve basin boundary delineations, processes were completed to make the DEM conform to 

stream locations defined in the National Hydrography Dataset 

(NHD) (U.S. Geological Survey, 1999b) (modified from Gotvald and others, 2009).

Basin characteristics were used as potential explanatory variables in the regression analyses based on theoretical 

hydrologic relation to flood flows and the ability to obtain a 

measurement of the basin characteristics by using digital datasets and GIS technology (modified from Gotvald and others, 

2009). The following nine basin characteristics were tested for 

statistical significance in the regression analysis:

1. Drainage area (DRNAREA), in square miles:

The area that contributes to surface runoff. 

2. Elevation (ELEV), in feet:

The mean basin elevation, in feet above National 

Geodetic Vertical Datum of 1929 (NGVD 29).

3. Forest (FOREST), in percent:

The area of forest, expressed as percent, of the 

contributing drainage area.

4. Lake area (LKAREA), in percent: 

The surface area of lakes and ponds expressed as a 

percentage of the contributing drainage area.

5. Swamps (WETLAND), in percent: 

The surface area of swamps expressed as a percentage 

of the contributing drainage area.

6. Storage (STORAGE), in percent: 

The surface area of lakes, ponds, and swamps expressed 

as a percentage of the contributing drainage area.

Trout Creek near Sulphur Springs, Florida, on the downstream side of 

the bridge during the flood of September 7, 2004. Stage was 43.01 ft 

and the flow rate was 1,610 ft3/s. Photograph by USGS.
Estimation of Flood Magnitude and Frequency at Gaged Stations 5

7. Channel slope (SL), in feet per mile:

The average slope of the main channel between points 10 

and 85 percent of the distance upstream from the gaging 

site to the basin divide.

8. Mean annual precipitation (PRECIP), in inches.

9. Average precipitation event size, in inches per day, over 

an 18-year mean.

Table 1 describes the basin characteristics considered for 

use in regional regression analysis, including the parameter 

name, units of measure, method, and source data.

Estimation of Flood Magnitude and 

Frequency at Gaged Stations

A flood-frequency relation is the relation of annual 

peak flow to probability of exceedance or recurrence interval (Hedgecock and Feaster, 2007). Previous USGS reports 

published flood-frequency flows in terms of the T-year event 

based on the recurrence interval for that flood quantile (for 

example, the “50-year flood”). While the T-year recurrence 

interval flood is statistically expected to occur, on average, 

Table 1. Basin characteristics considered for use in the regional regression analysis (modified from Gotvald and others, 2009).

[DEM, Digital Elevation Models; NHD, National Hydrography Dataset]

 Name Units Method Source data

Drainage area Square miles ArcGIS ArcHydro derived using 

watershed boundary, DEM, NHDPlus 

hydrography, and gaging stations

National Elevation Dataset, 10- and 30-meter 

resolution (http://ned.usgs.gov/#), NHDPlus 

hydrography, (http://www.horizon-systems.

com/nhdplus/), Watershed, http://www.ncgc.

nrcs.usda.gov/products/datasets/watershed/

index.html, NHDPlus hydrography and gaging 

stations, (http://www.horizon-systems.com/

nhdplus/)

Elevation Feet Area-weighted average National Elevation Dataset, 10- and 30-meter 

resolution (http://ned.usgs.gov/#)

Forest Percent (Forested area/drainage area)*100 National Land-Cover Dataset 2001 30-meter 

resolution (http://www.mrlc.gov/index.php).

Lake Percent (Lake area/drainage area)*100 National Land-Cover Dataset 2001 30-meter 

resolution (http://www.mrlc.gov/index.php).

Swamps Percent (Swamp area/drainage area)*100 National Land-Cover Dataset 2001 30-meter 

resolution (http://www.mrlc.gov/index.php).

Storage Percent ((Lake area + Swamp area)/drainage 

area)*100

National Land-Cover Dataset 2001 30-meter 

resolution (http://www.mrlc.gov/index.php).

Channel slope Feet per mile ArcGIS ArcHydro derived using the 

difference in the DEM elevation at 

points along the main channel within 

the drainage area at 10 percent and 

85 percent then divided by the length 

between those points

ArcGIS ArcHydro calculated using DEM and 

Archydro derived channel length, defined in 

the drainage area source data.

Mean annual precipitation Inches Area-weighted average DATMET, Daily Surface Weather and Climatalogical Summaries (http://www.daymet.org/

climateSummary.jsp)

Average precipitation event 

size, in inches per day, 

over an 18-year mean

Inches Area-weighted average DATMET, Daily Surface Weather and Climatalogical Summaries (http://www.daymet.org/

climateSummary.jsp)
6 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006

once during the T-year period, it may occur multiple times 

during the period, or not at all (modified from Gotvald and 

others, 2009). 

Because of the potential for misinterpretation, 

terminology associated with flood-frequency estimates 

has shifted from the T-year recurrence interval flood to the 

P-percent chance exceedance flood. The use of percent chance 

exceedance flood is recommended because it conveys the 

probability of a flood of a given magnitude being equaled 

or exceeded in a given year (Gotvald and others, 2009). For 

example, a 1-percent chance exceedance flood (formerly 

known as the “100-year flood”) corresponds to the flow 

magnitude that has a probability of 0.01 of being equaled 

or exceeded in a given year. That is, a flow with an annual 

exceedance probability of 0.01 has a 1 percent chance of being 

equaled or exceeded in a given year. The T-year recurrence 

interval and exceedance probability are the mathematical 

inverses of one another; therefore, a flood with an exceedance probability of 0.01 (1-percent chance exceedance) has a 

recurrence interval of 1/0.01 or 100 years. Thus, the P-percent 

chance exceedance is computed as the inverse of the T-year 

recurrence interval multiplied by 100. A 100-year T-year 

recurrence interval is equivalent to a 1-percent chance exceedance (1/100-year recurrence interval x 100 = 1-percent chance 

exceedance). A 25-year recurrence interval is equivalent to a 

4-percent chance exceedance (1/25-year recurrence interval 

x 100 = 4-percent chance exceedance), and so forth (modified from Feaster and others, 2009). Therefore, the P-percent 

chance exceedance is computed as follows:

 

, (1)

where

P is the percent chance exceedance

T is the T-year recurrence interval

The T-year recurrence intervals with corresponding 

annual exceedance probabilities and P-percent chance exceedance are described in table 2. 

Log-Pearson Type III Flood-Frequency Analysis

The flood-frequency relation for a stream having at 

least 10 years of record can be defined by fitting a theoretical 

frequency distribution curve to the logarithms of annual peak 

flows. Bulletin 17B (U.S. Water Resources Council, 1982) 

recommends fitting a Pearson Type III distribution to the 

logarithms of annual peak flows as the consistent method for 

determining flood magnitudes and frequencies. This technique, most commonly referred to as the log-Pearson Type III 

flood-frequency analysis, is generally accepted as the standard 

technique by most Federal and State agencies (Hedgecock and 

Feaster, 2007, eq. 1).

The log-Pearson Type III distribution is defined by the 

equation:

, (2)

where

Qp is the P-percent chance exceedance flow, 

in cubic feet per second;

Mx	 is the mean of the logarithms of the 

water-year peak flows;

Kp is a Pearson Type III factor for a skew 

coefficient (G) computed from the 

logarithms of the water-year peak flows 

and a selected percent chance exceedance 

P; and

Sx is the standard deviation of the logarithms of 

the water-year peak flows.

The computer program PeakFQWin version 5.2 

developed by the USGS was used to compute flood-frequency 

estimates for the streamgages considered for this study and 

the results are included in appendix 1. PeakFQWin automates 

many of the analysis procedures recommended in Bulletin 

17B (U.S. Water Resources Council, 1982), including identifying and adjusting for outliers and historical periods, weighting 

station skews and generalized skews, and fitting a log-Pearson 

Type III distribution curve to the annual peak-flow data (Flynn 

and others, 2006; Feaster and others, 2009). 

Skew Coefficient

The skew coefficient is a measure of asymmetry of the 

probability distribution of a set of annual peak flows. The 

skew coefficient is strongly influenced by the presence of 

outliers and is sensitive to extreme events (Feaster and others, 

2009). For example, an inaccurate estimate of the asymmetry 

of the flood-frequency distribution for an individual station 

can result if a single high event has occurred in a relatively 

P

T = 



 



 ×

1 100

Table 2. T-year recurrence intervals with corresponding annual 

exceedance probabilities and P-percent chance exceedance for 

flood-frequency discharge estimates (modified from Gotvald and 

others, 2009). 

 

T-year 

recurrence 

interval

Annual 

exceedance 

probability

P-percent chance 

exceedance

2 0.50 50

5 0.20 20

10 0.10 10

25 0.04 4

50 0.02 2

100 0.01 1

200 0.005 0.5

500 0.002 0.2

logQ M K S p x = + p x
Estimation of Flood Magnitude and Frequency at Gaged Stations 7

short period of record. Thus, the skew coefficient is considered 

a less reliable estimator than the mean and standard deviation 

of a population statistic for an individual site, because of its 

significant variability between samples. Several procedures 

have been introduced to improve the reliability of the sample 

skew coefficient in estimating the population skew. Bulletin 17B (U.S. Water Resources Council, 1982) recommends 

weighting the skew coefficient computed for an individual 

station with a generalized skew coefficient that represents 

the average skew for nearby stations. The weighting procedure recommended in Bulletin 17B (U.S. Water Resources 

Council, 1982) is different than those in Bulletin 17 (U.S. 

Water Resources Council, 1976) or Bulletin 17A (U.S. Water 

Resources Council, 1977) and tends to reduce the influence of 

the generalized skew and increase the influence of the station 

skew (Hammett and DelCharco, 2005).

Program PeakFQ software allows the user to weight the 

station skew coefficient with the generalized skew coefficient 

to compute the log-Pearson Type III flood-frequency curve 

for a station, as recommended in Bulletin 17B (U.S. Water 

Resources Council, 1982). The generalized skew coefficient 

used for this study was determined from Bulletin 17B (U.S. 

Water Resources Council, 1982, pl. 1). The weighted skew 

combines the station and generalized skews by weighting them 

in inverse proportion to their mean-square errors. Because the 

mean-square error of the station skew increases as the length 

of record decreases, weighted skew coefficients for stations 

with short periods of record can be substantially adjusted by 

generalized skews. For stations with longer periods of record, 

the station skew has the greater importance in the computation of a weighted skew coefficient (Hammett and DelCharco, 

2005). The log-Pearson Type III flood-frequency curves 

presented in appendix 1 represent computations based on 

weighted skew coefficients.

Regional Flood-Frequency Regression Analysis

A regional regression analysis was used to 

mathematically relate basin characteristics to estimates 

of flood magnitude and frequency at streamgaging stations. 

Explanatory variables for the regional regression analysis 

were related to the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 

0.2-percent chance exceedance flows that had been calculated 

using Bulletin 17B (U.S. Water Resources Council, 1982) 

criteria. Equations computed from the regression analyses 

can then be used to calculate estimates of flood flows at sites 

where basin characteristics are known, but flow data are 

unavailable or insufficient (less than 10 years of available data 

at the gage).

All possible combinations of explanatory variables 

were investigated to determine which basin characteristics 

were most statistically significant in relation to peak flows. 

Preliminary regression models were evaluated by examining 

the root mean-square error, coefficient of determination (R2) 

for each model, and the significance level of the independent 

variables. Based on the investigation of all possible combinations of explanatory variables, contributing drainage area 

(DRNAREA, eq. 2) was determined to be the most influential 

variable followed by the percent of total surface area covered 

by storage (STORAGE, eq. 2), which includes lakes, ponds, 

and swamps. Hammett and DelCharco (2005), Bridges (1982), 

and Seijo and others (1979) determined that contributing 

drainage area was the most influential variable in their respective studies; however, each of these investigators concluded 

that channel slope and lake area were significant factors at the 

0.05 significance level. The regression analysis for this study 

included storage, rather than lakes (which does not include the 

surface area covered by swamps). Additionally, the channel 

slope variable improved the regression analysis by less than 

1 percent, and thus, was not a final variable included in this 

study considering the relatively flat topography of Florida.

Log transformations were used for the variables in the 

regressions, which is an identical technique employed in previous studies. Throughout the State, there were several gages 

where the percent of storage was zero; therefore, it was not 

possible to transform that characteristic without the addition 

of a constant for all sites, similar to what was done in previous studies. Adding a small constant is a common practice 

when applying log transformations to datasets with some zero 

values, according to Haan (1977). Hammett and DelCharco 

(2005) and Bridges (1982) each added constants of 3.0 or 0.6 

for the lake variable depending on which geographic region 

the site was located. For this study, a constant of 1.0 was 

added to all storage values in the four hydrologic flood regions 

(pl. 1). 

Multiple-regression techniques were used to delineate the 

four hydrologic flood regions defined in Florida (pl. 1). These 

regions were defined based on the plotted residuals from the 

multiple-regression analysis. In addition, data from previous 

flood-frequency studies, and geologic, physiographic, and 

drainage-area maps were also consulted to help better define 

these regions.

Generalized Least-Squares Regression Analysis

Generalized least-squares regression methods, as 

described by Stedinger and Tasker (1985), were used to determine final regional P-percent chance exceedance flow regression equations with the computer program GLSNET developed by the USGS. An investigation by Tasker and Stedinger 

(1989) showed that model error from an ordinary least-squares 

regression can be reduced by using a generalized least-squares 

(GLS) regression, which takes into account the time-sampling 

error of flood-flow characteristics and the correlation of floodflow characteristics between nearby stations. In GLS analysis, 

the total prediction error is partitioned into model error and 

sampling error, thus making it possible to identify errors due 

to inadequacies of model formulation compared with deficiencies in the database (Hammett and DelCharco, 2005).
8 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006

Accuracy and Limitations of 

Flood-Frequency Estimates

Empirical results from regression equations are not 

exact. Regression equations are statistical models that are 

interpreted and applied within the limits of the data and with 

the understanding that the results are best-fit estimates with 

an associated scatter or variance. The development and use 

of a regression equation raises questions about how well the 

predicted values are representative of true values. Errors in the 

model (that is, differences between the predicted and observed 

values) can be examined to determine parameters that describe 

the accuracy of a regression equation, which depends on both 

the model error and the sampling error. Model error measures the ability of a set of explanatory variables to estimate 

the values of peak-flow characteristics calculated from the 

station records that were used to develop the equation. The 

model error depends on the number and predictive power of 

the explanatory variables in a regression equation. Sampling 

error measures the ability of a finite number of stations with 

a finite number of recorded annual peak flows to describe the 

true characteristics of the entire peak-flow record for a station. 

The sampling error depends on the number and record length 

of stations used in the analysis, and decreases as the number 

of stations and record lengths increase (modified from Gotvald 

and others, 2009).

A measure of uncertainty in a regression equation 

estimate for a site, i, is the variance of prediction, Vp,i. The Vp,i

is the sum of the model error variance and sampling error 

variance and is computed using the following equation 

(Gotvald and others, 2009):

 , (3)

where

γ2 is themodel error variance; and

MSEs,i is the sampling mean square error for 

the site, i, 

Assuming that the explanatory variables for the gaged 

stations in a regression analysis are representative of all stations in the region, the average accuracy of prediction for 

a regression equation can be determined by computing the 

average variance of prediction, AVP, for n number of stations 

(Gotvald and others, 2009):

, (4)

where variables are as previously defined.

Traditionally, accuracy of a flood-frequency relation has 

been expressed two ways—the mean standard error of estimate, SEE, or as the mean standard error of prediction, SEP. 

The SEE is a measure of how well the regression equation 

fits the data used to derive the relation and is often referred to 

as the model error. The SEE is computed using the following 

equation (Gotvald and others, 2009):

, (5)

where

SEE is the mean standard error of estimate, 

in percent; and

γ2 is the model error variance.

The standard error of prediction, SEP, is the square root 

of the mean square error of prediction and is a measure of 

how well the regression equation estimates flood flows when 

applied to ungaged basins. The SEP is calculated using the 

following equation (Gotvald and others, 2009):

, (6)

where

SEp is the mean standard error of prediction, 

in percent; and

AVP is the average variance of prediction.

The regression equations and errors presented in table 3 

(eq. 7-38) are only applicable when the equations are used for 

sites where the values of basin characteristics fall within the 

range of values used to develop the equations. Extrapolating 

the regression equations for use in watersheds that have characteristics outside the valid range would produce flood-flow 

estimates with unpredictable errors. A constant of 1.0 is added 

to storage when using the regression equations defined in 

table 3 for the reasons previously discussed. Table 4 describes 

the valid ranges of basin characteristics for each hydrologic 

region, as defined in this study. Figure 2 shows the distribution 

of drainage area and storage. For example, Region 3 has an 

apparent outlier with 91 percent storage, but the limiting value 

for the region is 48 percent storage. A regression of drainage 

area alone versus the 1-percent chance exceedance shows the 

point plots within the general trend of the data; therefore, the 

site was left in the regression. However, there is not enough 

data in the range to verify it truly works, so that is the reason 

for limiting the valid range for storage to 48 percent.

 Regression equations 7-38 are shown on table 3 (7-38)

Previous USGS flood-frequency reports expressed the 

accuracy of the regional regression equations in terms of 

equivalent length of record (in years), which is an estimate of 

the number of years of station data needed at an ungaged site 

to produce peak-flow estimates with accuracy equal to that 

of the associated regression equation. The equivalent lengthof-record concept can sometimes misconstrue the relation 

between flood-frequency estimates and associated variances. 

V M p i SEs i , = + γ , 2

AVP

n

MSEs i

i

n

= + 



 



 =

γ ∑ 2 1

1

,

SEE = − 

 

( ) 100 10 1 2 3026 0 5 2 . . γ

SEP

AVP = − 

  ( ) 100 10 1 2 3026 0 5 . .
Estimation of Flood Magnitude and Frequency at Gaged Stations 9

Table 3. Regression equations for geographic regions in Florida. 

[n, number of stations used in analysis. Table includes equations 7-38 referenced in the text]

 

Exceedance 

probability 

(percent)

Regression 

equations

Equation 

number

Standard 

error of 

prediction 

(percent)

Standard 

error 

of estimate

 (percent)

Equivalent 

length of 

record 

(years)

Average 

sampling 

error 

(log units)

Average 

model error 

(log units)

Average 

variance of 

prediction 

(log units)

 Region 1 (n=77)

50 Q=127A0.656(ST+1)-0.098 7 43 42 2.68 0.0018 0.0307 0.0325

20 Q=248A0.662(ST+1)-0.189 8 40 39 4.84 0.0019 0.0262 0.0281

10 Q=357A0.666(ST+1)-0.239 9 42 40 6.19 0.0022 0.0287 0.0309

4 Q=528A0.671(ST+1)-0.293 10 47 45 7.26 0.0028 0.0353 0.0381

2 Q=684A0.675(ST+1)-0.328 11 52 50 7.69 0.0034 0.0418 0.0452

1 Q=864A0.679(ST+1)-0.362 12 57 55 7.92 0.0040 0.0493 0.0533

0.5 Q=1072A0.683(ST+1)-0.392 13 62 60 8.02 0.0046 0.0576 0.0622

0.2 Q=1395A0.688(ST+1)-0.430 14 70 67 8.03 0.0055 0.0700 0.0755

 Region 2 (n=83)

50 Q=101A0.617(ST+1)-0.211 15 58 57 1.79 0.0026 0.0529 0.0555

20 Q-184A0.620(ST+1)-0.212 16 53 51 2.70 0.0024 0.0443 0.0467

10 Q=253A0.621(ST+1)-0.215 17 52 50 3.69 0.0025 0.0427 0.0452

4 Q=353A0.621(ST+1)-0.221 18 53 51 4.94 0.0027 0.0435 0.0462

2 Q=435A0.621(ST+1)-0.226 19 54 52 5.73 0.0030 0.0455 0.0485

1 Q=525A0.621(ST+1)-0.231 20 56 54 6.34 0.0033 0.0485 0.0518

0.5 Q=622A0.621(ST+1)-0.236 21 59 56 6.80 0.0036 0.0523 0.0559

0.2 Q=764A0.620(ST+1)-0.244 22 63 60 7.19 0.0041 0.0584 0.0625

 Region 3 (n=76)

50 Q=72.7A0.741(ST+1)-0.589 23 87 85 0.99 0.0048 0.1023 0.1071

20 Q=164A0.704(ST+1)-0.587 24 62 60 2.07 0.0031 0.0588 0.0619

10 Q=250A0.686(ST+1)-0.592 25 56 54 3.23 0.0028 0.0486 0.0514

4 Q=390A0.668(ST+1)-0.601 26 53 52 4.77 0.0028 0.0444 0.0472

2 Q=517A0.656(ST+1)-0.608 27 53 52 5.74 0.0030 0.0444 0.0474

1 Q=664A0.646(ST+1)-0.616 28 54 52 6.52 0.0032 0.0459 0.0491

0.5 Q=833A0.638(ST+1)-0.625 29 56 54 7.11 0.0034 0.0482 0.0516

0.2 Q=1094A0.629(ST+1)-0.638 30 59 56 7.68 0.0038 0.0522 0.0560

 Region 4 (n=69)

50 Q=171A0.628(ST+1)-0.401 31 36 35 4.15 0.0017 0.0218 0.0235

20 Q=321A0.618(ST+1)-0.395 32 39 38 4.86 0.0020 0.0250 0.0270

10 Q=447A0.614(ST+1)-0.396 33 43 41 5.54 0.0024 0.0293 0.0317

4 Q=636A0.610(ST+1)-0.401 34 48 46 6.19 0.0030 0.0365 0.0395

2 Q=797A0.609(ST+1)-0.406 35 53 50 6.48 0.0035 0.0427 0.0462

1 Q=975A0.608(ST+1)-0.411 36 57 55 6.64 0.0040 0.0496 0.0536

0.5 Q=1171A0.608(ST+1)-0.416 37 62 59 6.71 0.0046 0.0571 0.0617

0.2 Q=1461A0.609(ST+1)-0.424 38 69 66 6.70 0.0054 0.0681 0.0735
10 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006

Using variances provides a more accurate characterization of 

the underlying uncertainty of the various flow estimates.

Weighting of Log-Pearson Type III and 

Regression Analyses

Flood estimates at streamgages for a selected exceedance 

probability can be determined by weighting the regional and 

station flood estimates for the specified exceedance probability 

using the variance of prediction for each of the two estimates. 

The variance of prediction can be considered as a measure of 

the uncertainty in either the streamgage flow estimate or the 

regional regression results. If the two estimates are assumed 

to be independent and are weighted in inverse proportion to 

the associated variances, the variance of the weighted estimate 

will be less than the variance of either of the independent 

estimates. 

The variance of prediction corresponding to the 

streamgage-flow estimate from the log-Pearson Type III 

analysis is computed using the asymptotic formula given in 

Region 1 Variable Distribution

0

5

10

15

20

25

30

35

40

45

50

-1 0 1 2 3 4

LOG DRAINAGE AREA

Region 2 Variable Distribution

0

10

20

30

40

50

60

70

80

90

100

-2 -1 0 1 2 3 4

LOG DRAINAGE AREA

Region 3 Variable Distribution

0

10

20

30

40

50

60

70

80

90

100

-1 0 1 2 3 4

LOG DRAINAGE AREA

Region 4 Variable Distribution

0

5

10

15

20

25

30

35

40

-1 0 1 2 3 4

LOG DRAINAGE AREA

ST (STORAGE, IN PERCENT) ST (STORAGE, IN PERCENT)

ST (STORAGE, IN PERCENT) ST (STORAGE, IN PERCENT)

Figure 2. Distribution of drainage area and storage for the four hydrologic regions in Florida.

Table 4. Valid ranges of basin characteristics for the 

regional regression equations.

[mi2, square miles]

Basin 

characteristic

Minimum 

in region

Maximum 

in region

Region 1

Drainage area (mi2) 0.14 4385

Storage (percent) 0.00 44.29

Region 2

Drainage area (mi2) 0.06 2647

Storage (percent) 0.00 74.33

Region 3

Drainage area (mi2) 0.41 3244

Storage (percent) 0.18 48.04

Region 4

Drainage area (mi2) 0.20 2833

Storage (percent) 0.00 34.12
Estimation of Flood Magnitude and Frequency at Gaged Stations 11

Cohn and others (2001) with the addition of the mean-squared 

error of generalized skew (Griffis and others, 2004). This variance varies as a function of the length of record and the fitted 

log-Pearson Type III distribution parameters (mean, standard 

deviation, and weighted skew). The variance of prediction for 

the streamgage flow estimate generally decreases with length 

of record and the quality of the log-Pearson Type III distribution fit. The variance of prediction values for the streamgageflow estimates for the 275 streamgages in Florida are shown 

in appendix 2. The variance of prediction from the regression 

equations is a function of the regression equations and the 

values of the independent variables used to develop the flow 

estimate from the regression equations. This variance generally increases as the values of the independent move further 

from the mean values of the independent variables. Once the 

variances have been computed, the two independent-flow estimates can be weighted using the following equation (Feaster 

and others, 2009; Gotvald and others, 2009): 

, (39)

where

QP(g)w	 is the weighted estimate of peak flow for any 

P-percent chance exceedance for a gaged 

station, in cubic feet per second;

Vp,P(g)r is the variance of prediction at the gaged 

station derived from the regression 

equation for the selected P-percent chance 

exceedance, in log units;

Qp(g)s is the estimate of peak flow at the gaged 

station from the log-Pearson Type III 

analysis for the selected P-percent chance 

exceedance, in cubic feet per second;

Vp,P(g)s is the variance of prediction at the gaged 

station from the log-Pearson Type III 

analysis for the selected P-percent chance 

exceedance, in log units; and

Qp(g)r is the peak-flow estimate for the P-percent 

chance exceedance at the gaged station 

derived from the applicable regression 

equation, in cubic feet per second.

When the variance of prediction corresponding to one 

of the estimates is high, the uncertainty also is high, so the 

weight for that estimate is relatively small. Conversely, when 

the variance of prediction is low, the uncertainty also is low, so 

the weight is correspondingly large. The variance of prediction 

associated with the weighted estimate, Vp, P(g)w, is computed 

using the following equation (Feaster and others, 2009 

Gotvald and others, 2009):

, (40)

where variables are as previously defined.

Weighted flood-flow estimates for the 305 streamgages 

used in this study are presented in appendix 1, along with the 

log-Pearson Type III distribution and regression results.

log

, ( ) ( log l ) , ( ) og ( )

, ( )

Q P(g)w

V Q V Q

V V

p P g r P g s p P g s P g r

p P g s p

= +

+ , P g( )r

V V V

V V p P g w

p P g s p P g r

p P g s p P g r

, ( )

, ( ) , ( )

, ( ) , ( )

= +

Aerial view near the 

Alapaha River near 

Jennings, Florida, during 

the flood of April 2009. 

Photograph by the Fish 

and Wildlife Commission.
12 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006

Estimation of Flood Magnitude and 

Frequency at Ungaged Stations

Peak-flow estimates have been calculated for 

275 streamgages in Florida, 21 in Georgia, and 9 in Alabama 

for the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent chance 

exceedance flows. However, flood-flow estimates are 

frequently needed for locations on a stream where little (less 

than 10 years of data) to no-flow data are available. Floodflow estimates for these streams can be derived by directly 

applying the regional regression equations (table 3) for the 

respective hydrologic regions (pl. 1). 

Methods for improved flood-frequency estimates for an 

ungaged site near a gaged site on the same stream with more 

than 10 years of peak-flow data were presented by Sauer 

(1974). To obtain a weighted peak-flow estimate (QP(u)w) for 

P-percent chance exceedance at the ungaged site, the weighted 

peak-flow estimate for a downstream or upstream gaged 

site (QP(g)w) must first be determined using equation 39. The 

weighted peak-flow estimate for the ungaged site (QP(u)w) is 

then computed using the following equation:

, (41)

where

QP(u)w is the weighted estimate of peak flow for the 

selected P-percent chance exceedance at 

the ungaged site, in cubic feet per second;

ΔA is the absolute value of the difference between 

the drainage areas of the gaged site and the 

ungaged site, in square miles;

A(g) is the drainage area for the gaged site, 

in square miles; and

QP(u)r is the peak-flow estimate derived from the 

applicable regional equations for the 

selected P-percent chance exceedance at 

the ungaged site, in cubic feet per second.

Use of this equation gives full weight to the regression 

equation estimates when the drainage area for the ungaged site 

is equal to 0.5 or 1.5 times the drainage area for the gaged site, 

and increasing weight to the gaged site estimates as the ratio 

of the drainage area approaches 1. The weighting procedure 

must not be applied when the drainage-area ratio for the 

ungaged site and gaged site is less than 0.5 or greater than 1.5 

(Feaster and others, 2009; Gotvald and others, 2009).

An example of the application of the procedure described 

in this section is the following computation of the weighted 

1-percent chance exceedance flow for a hypothetical ungaged 

site on the New River located above the USGS station near 

Sumatra, Florida (station number 02330400, site 255, pl. 1) 

(Gotvald and others, 2009):

1. Calculate the value of Q1%(g)w (Q1%(g)w=7,010 ft3/s);

2. Obtain the drainage areas for both the gaged and ungaged 

sites (Ag=151 mi2, and Au=115 mi2);

3. Obtain the storage factor for both the gaged and ungaged 

sites (STg=43.03, and STu=30.1);

4. Compute Q1%(u)r for the ungaged site using equation 12 

((864*(1150.679))(31.1-0.362))=6,240 ft3/s;

Table 5. Comparison of Bulletin 17B (U.S. Water Resources Council, 1982) flood-discharge estimates from this investigation with 

Bulletin 17 (U.S. Water Resources Council, 1976) or Bulletin 17A (U.S. Water Resources Council, 1977) estimates from previous 

investigations.

[N, number of years of record used in the analysis] 

Investigator

Flood discharge (in cubic feet per second) 

P-percent chance exceedance

N 50 20 10 4 2 1 0.5 0.2

02300000 Manatee River near Bradenton, Florida; map number 136

This investigation (2011) 27 2,420 4,530 6,240 8,770 10,900 13,200 15,800 19,500

Bridges (1982) 27 2,410 4,520 6,260 8,840 11,000 13,400 16,100 20,100

Seijo and others (1979) 27 2,360 4,490 6,340 9,230 11,800 14,800 18,200 23,500

02322500 Santa Fe River near Fort White, Florida; map number 212

This investigation (2011) 75 3,860 6,610 8,720 11,700 14,100 16,700 19,400 23,400

Bridges (1982) 47 4,120 6,870 8,940 11,800 14,100 16,500 19,100 22,800

Seijo and others (1979) 45 4,170 7,060 9,340 12,600 15,400 18,300 21,600 26,400

02297100 Joshua Creek at Nocatee, Florida; map number 120

This investigation (2011) 56 1,760 3,180 4,380 6,260 7,930 9,860 12,100 15,500

Bridges (1982) 28 1,920 3,570 4,930 6,950 8,660 10,500 12,600 15,700

Seijo and others (1979) 26 1,960 3,710 5,240 7,630 9,770 12,200 15,100 19,500

Q A

A

A

A

Q

Q P u w

g g

P g w

P g r

( )

( ) ( )

( )

( )

= 









 + −

































2 1 ∆ ∆2 







QP u( )r
Estimation of Flood Magnitude and Frequency at Ungaged Stations 13

5. Compute Q1%(g)r for the gaged site using equation 12 

(Q1%(g)r =6,640 ft3/s);

6. Compute ΔA, where ΔA =151-115=36 mi2;

7. Compute the weighted estimate for the ungaged site, 

Qp(u)w , using equation 41 (Q1%(u)w =[((2*36)/151)+

((1-((2*36)/151))*(7,010/6,640))]*6,240=6,420 ft3/s . 

For an ungaged site that is located between two gaged 

stations on the same stream, two flow estimates can be made 

using the methods and criteria outlined in this section. In addition to evaluating the differences in hydrologic region makeup of the two gaged stations in comparison to the ungaged site, 

hydrologic judgment may be necessary to determine which of 

the two estimates is most appropriate. Other factors may need 

consideration when evaluating the two estimates, including the 

differences in the length of record for the two gaged stations 

and the hydrologic conditions that existed during the data collection period for each gaged station. For example, does the 

time series represent a climatic period that was predominately 

wet or dry? (Modified from Gotvald and others, 2009.)

Sites on Streams that Cross Flood Region 

or State Boundaries

For streams that cross flood region boundaries, flood 

magnitudes can be estimated by weighting the flood estimate 

by the percentage of basin drainage area in each flood region. 

First, the flood estimate is computed as if the total drainage 

area lies in each flood region. Next, the flood estimates are 

weighted on the percentage of drainage area in each flood 

region. The same procedure applies to sites on streams that 

cross state boundaries where different methods are used for 

estimating flood magnitudes.

Comparison with Previous Analyses

Estimates of flood flows for three stations used in this 

investigation are compared to estimates presented by Bridges 

(1982) and Seijo and others (1979) to illustrate the effects of 

changes in methodology, regression equations, and record 

length (tables 5, 6, and 7). Manatee River near Bradenton was 

chosen for comparative purposes and, because the site was 

discontinued in 1966, the same period of record was used 

in all three investigations. Santa Fe River near Fort White 

and Joshua Creek at Nocatee each have substantially longer 

lengths of record now than when they were analyzed in the 

Bridges (1982) and Seijo and others (1979) reports, and these 

sites were chosen as representing sites with additional data for 

analysis in the present study.

Table 5 shows the effects of both additional records and 

changes in methods during the last 30 years of estimating 

flood flows using log-Pearson Type III analyses. Manatee 

River near Bradenton, for example, has 27 years of annual 

peak-flow data and all three investigations used this same 

period of record. This investigation used the U.S. Water 

Resources Council (1982) Bulletin 17B guidelines to compute flood flow. The investigation by Bridges (1982) used the 

guidelines presented in Bulletin 17A (U.S. Water Resources 

Council, 1977). The work by Seijo and others (1979) used 

the guidelines presented in Bulletin 17 (U.S. Water Resources 

Table 6. Comparison of regression equation flood-discharge estimates from this investigation with regression equation flood-discharge 

estimates from previous investigations.

[N, number of years of record used in the analysis] 

Investigator

Flood discharge (in cubic feet per second) 

P-percent chance exceedance

N 50 20 10 4 2 1 0.5 0.2

02300000 Manatee River near Bradenton, Florida; map number 136

This investigation (2011) 27 1,570 2,850 3,890 5,380 6,660 8,050 9,590 11,900

Bridges (1982) 27 1,640 2,990 4,060 5,610 6,890 8,280 9,740 11,900

Seijo and others (1979) 27 1,810 3,360 4,690 6,760 8,600 10,700 13,100 16,900

02322500 Santa Fe River near Fort White, Florida; map number 212

This investigation (2011) 75 4,190 7,780 10,700 14,700 17,900 21,300 24,900 29,700

Bridges (1982) 47 2,620 4,890 6,720 9,410 11,700 15,200 16,800 20,900

Seijo and others (1979) 45 4,050 6,900 9,200 12,600 15,400 18,600 22,100 27,400

02297100 Joshua Creek at Nocatee, Florida; map number 120

This investigation (2011) 56 2,040 3,670 5,010 6,940 8,590 10,400 12,400 15,300

Bridges (1982) 28 2,180 3,910 5,290 7,280 8,930 10,700 12,600 15,400

Seijo and others (1979) 26 2,670 4,900 6,800 9,730 12,300 15,300 18,700 23,900
14 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006

Council, 1976), which used only a generalized skew, rather 

than a map skew weighted with the station skew (Hammett 

and DelCharco, 2005). Comparing this study with the Bridges 

(1982) study shows less than a 1-percent difference in estimated flood flows at the 2-percent chance exceedance level, 

less than 2-percent difference at the 0.5- and 1-percent chance 

exceedance levels, and less than 3-percent difference at the 

0.2-percent chance exceedance level. The report by Seijo and 

others (1979) shows a much wider variance in results because 

the study utilized only a generalized skew over the weighted 

skew. For example, at the 0.2-percent chance exceedance, the 

difference between the Seijo and others (1979) study and this 

study is about 17 percent. At the 50-percent chance exceedance, the difference is less than 3 percent. 

Table 6 shows the differences in the regressions estimates 

derived by the three studies. The differences in regression 

estimates are attributed to the evolution in methods, longer 

lengths of record, changes in geographic groupings, and 

changes in explanatory variables used in the equations. This 

study used contributing drainage area and percent covered by 

storage as explanatory variables. Bridges (1982) and Seijo and 

others (1979) each used contributing drainage area, channel 

slope, and percent covered by lakes in their investigations. 

Seijo and others (1979) used soil index as an additional variable in their regression equations.

Table 7 shows the weighted flood-discharge flow estimates derived in this study compared to those from Bridges 

(1982) and Seijo and others (1979). The difference in weighted 

estimates at Manatee River near Bradenton can be attributed 

to the differences in methodology, lengths of record, and 

several additional high-water events that have occurred since 

the Bridges (1982) and Seijo and others (1979) investigations. 

The Seijo and others (1979) investigation has a noticeable 

overestimation of flows at all three example locations, which 

is probably the reflection of different methods used during 

their study.

Effects of Flood Distribution and 

Magnitude in the Peak-Flow Dataset

Table 8 shows a comparison of the weighted flood-flow 

estimates from this investigation with the weighted estimates 

from the Bridges (1982) investigation. The comparison shows 

the effects of flood distribution and magnitude throughout 

the dataset at three selected stations. The weighted estimates 

from Bridges (1982) investigation and this investigation at 

Choctawhatchee River near Bruce (station number 02366500, 

map number 278, pl. 1) indicate little change in distribution 

or magnitudes of floods during the period of record at the site. 

The estimates are within 2 percent of the previously published 

data and the new data. Flood magnitudes appear to be evenly 

distributed with no high outliers during the 76-year period of 

systematic record. The peak-flow data are available online as 

supplemental data at https://pubs.usgs.gov/sir/2011/5034.

The weighted estimates for Little River near Quincy 

(station number 02329500; map number 243, pl. 1) show the 

effects of a dataset where large magnitude floods occurred 

in the early part of the systematic record. The current study 

estimates approximately 7 percent less water now than was 

estimated in the Bridges (1982) investigation for the 1-percent 

chance exceedance probability. An analysis of the peak-flow 

data indicates that of the top five floods at the site, only two 

have occurred since 1978 (the end of the period of analysis 

for the Bridges (1982) investigation)—one in 1984 (rank 5; 

Table 7. Comparison of weighted flood-discharge estimates from this investigation with weighted estimates from previous 

investigations.

[N, number of years of record used in the analysis] 

Investigator

Flood discharge (in cubic feet per second) 

P-percent chance exceedance

N 50 20 10 4 2 1 0.5 0.2

02300000 Manatee River near Bradenton, Florida; map number 136

This investigation (2011) 27 2,260 4,200 5,740 7,900 9,680 11,500 13,600 16,600

Bridges (1982) 27 2,290 4,240 5,790 8,050 9,990 12,000 14,400 17,600

Seijo and others (1979) 27 2,300 4,230 5,880 8,390 10,700 13,300 16,200 20,900

02322500 Santa Fe River near Fort White, Florida; map number 212

This investigation (2011) 75 3,860 6,640 8,800 11,900 14,400 17,100 20,000 24,200

Bridges (1982) 47 4,050 6,730 8,790 11,600 13,900 16,400 18,800 22,500

Seijo and others (1979) 45 4,160 7,040 9,320 12,600 15,400 18,400 21,700 26,700

02297100 Joshua Creek at Nocatee, Florida; map number 120

This investigation (2011) 56 1,780 3,210 4,440 6,350 8,030 9,960 12,100 15,500

Bridges (1982) 28 1,950 3,620 4,990 7,010 8,710 10,500 12,600 15,600

Seijo and others (1979) 26 2,020 3,940 5,600 8,240 10,600 13,200 16,300 21,000
Flood-Frequency Analysis for Large Streams 15

16,200 ft3/s) and one in 1991 (rank 4; 18,700 ft3/s). However, 

the top three floods were substantially larger in magnitude and 

most likely influenced the results published in 1982, because 

of a relatively short period of record used in the analysis at 

that time. The top ranking flood occurred in 1969 (45,600 

ft3/s); second ranking flood occurred in 1965 (25,400 ft3/s); 

and the third ranking flood occurred in 1960 (23,300 ft3/s). 

The peak-flow data are available online as supplemental data 

at https://pubs.usgs.gov/sir/2011/5034.

The weighted estimates for the Yellow River at Milligan 

(station number 02368000, map number 283, pl. 1) show the 

effects of a dataset where large magnitude floods occur in 

the latter part of the systematic record. The current investigation estimates approximately 45 percent more water now 

than was estimated in the Bridges (1982) investigation for the 

1-percent chance exceedance probability. An analysis of the 

peak-flow data indicates four of the top five floods at the site 

have occurred since the Bridges (1982) investigation—all in 

the 1990s. Until 1978 (the end of the period of analysis for 

the Bridges (1982) investigation), the largest flood during the 

systematic record was 38,600 ft3/s, recorded in 1975 (rank 4 

of the top 5). Since then, however, four more large floods have 

occurred, three of which are substantially larger than that of 

1975. The top three ranking floods in the systematic record 

occurred in 1999 (rank 1; 82,800 ft3/s), 1998 (rank 2; 55,600 

ft3/s), and 1990 (rank 3; 51,500 ft3/s). The peak-flow data are 

available online as supplemental data at https://pubs.usgs.gov/

sir/2011/5034. 

Flood-Frequency Analysis for 

Large Streams

Flood-frequency relations for streamgages along the 

main stem of the Apalachicola River and Suwannee River at 

Ellaville and below (figs. 3–4) were not determined using the 

regional flood-frequency analysis, because the drainage areas 

of these sites are substantially larger than the maximum drainage areas for the streamgages used in the regional analyses. 

Additionally, the streamgages on the Apalachicola River are 

subject to regulation at Jim Woodruff Dam at Lake Seminole 

(pl. 1). Where the data analysis indicated it was appropriate, however, relations of flood magnitudes to drainage area 

were determined for selected exceedance probabilities. The 

flood-frequency relations for each river are summarized in the 

following sections. The estimated flood-frequency flows were 

based on log-Pearson Type III analyses of peak-flow data at 

the gaged sites on the streams, as described by the Bulletin 

17B (U.S. Water Resources Council, 1982) guidelines, and 

are listed in appendix 3. Visual and graphical inspection of 

the data for each analysis indicated that a log-Pearson Type 

III distribution was a reasonable fit for the frequency curves 

published in this report.

Because the gages along the Apalachicola River have 

been affected by regulation of flows from Jim Woodruff Dam 

since 1957 (when the dam was constructed), trend analyses 

for the annual peak flows were performed to test if regulated 

patterns have changed with time. Trend analyses also were 

performed at the gages along the Suwannee River at Ellaville 

and below to test whether flow patterns have changed with 

time within the basin. Trends in regulations and flow were 

examined using Kendall’s tau trend analysis and cumulative 

Table 8. Comparison of weighted flood-discharge estimates from this investigation with weighted estimates from the Bridges (1982) 

investigation.

[N, number of years of record used in the analysis] 

Investigator

Flood discharge (cubic feet per second) 

P-percent chance exceedance

N 50 20 10 4 2 1 0.5 0.2

02366500 Choctawhatchee River near Bruce, Florida; map number 278

This investigation (2011) 76 31,300 49,000 63,600 85,800 106,000 128,000 154,000 194,000

Bridges (1982) 48 31,400 50,000 64,800 87,100 106,000 128,000 153,000 190,000

Percent change 0 -2 -2 -1 0 0 1 2

02329500 Little River near Quincy, Florida; map number 243

This investigation (2011) 41 4,250 9,370 14,300 22,600 30,600 40,000 51,200 69,400

Bridges (1982) 28 4,270 9,850 15,100 24,000 32,600 43,000 55,400 75,500

Percent change 0 -5 -5 -6 -6 -7 -8 -8

02368000 Yellow River at Milligan, Florida; map number 283

This investigation (2011) 66 8,520 17,300 25,600 39,200 51,900 66,600 83,700 111,000

Bridges (1982) 40 8,310 14,900 20,500 29,200 37,000 45,900 56,100 71,800

Percent change 3 16 25 34 40 45 49 55
16 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006

plots of weekday daily-mean flows (single-mass curves, 

Helsel and Hirsch, 1995). Analysis plots included: 

(1) cumulated ratio of 90- to 50-percentile daily-value streamflow by water year, (2) cumulated weekday 50-percentile 

streamflow by water year, (3) cumulated water-year mean 

weekday streamflow, (4) cumulated water-year mean weekend 

streamflow, (5) cumulated ratio of 10- to 50-percentile streamflow by climatic year, and (6) cumulated weekday 

50-percentile streamflow by climatic year. The single-mass 

curve is a basic analytical tool showing a plot of cumulative values against time. The slope of the single-mass curve 

represents the constant of proportionality between the two 

quantities (Searcy and Hardison, 1960). A break in the slope of 

the curve would indicate a sudden change in the proportionality constant. This analysis is particularly useful for regulated 

streams, because it can determine whether or not regulation 

has remained consistent throughout the regulation period.

Flood magnitudes for selected exceedance probabilities 

can be estimated by using figures 3–4 by reading the flow 

scale for the known drainage areas. Peak-flow data at selected 

sites on these large streams are included in appendix 3 of this 

report. The curves in figures 3–4 have been drawn as straight 

lines connecting the plotted data points. These linear representations do not infer that flood estimates or drainage area varies 

uniformly along the stream. The exceedance probability flood 

estimates at multiple streamgages along a stream will vary as a 

result of several factors, including length of record, concurrent 

period of record, and intervening tributaries. Additionally, the 

location of the storm causing a flood will impact flood estimates. If, for example, a storm was located in the lower part of 

a basin, the streamgages in the upper half of the basin would 

not record the runoff associated with the storm. Consequently, 

it is conceivable that a flood of record at a lower gage may not 

necessarily be a flood of record at an upper streamgage. As a 

result of these factors, exceedance probability flood estimates 

between two streamgages on the same stream may not be 

completely linear. However, linearly interpolating between 

two streamgages with relatively similar lengths of record can 

provide a reasonable estimate of flood magnitudes between the 

two streamgages (Hedgecock and Feaster, 2007).

Apalachicola River

The relation of flood flow to drainage area for selected 

exceedance probabilities for the Apalachicola River is shown 

in figure 3 (Hedgecock and Feaster, 2007). Flow patterns at 

all streamgages along the Apalachicola River are impacted 

by regulation predominantly from Jim Woodruff Dam. Trend 

assessments, using Kendall’s tau and single-mass curves, were 

made for the entire period of record from 1920 through 2006 

for the Apalachicola River at Chattahoochee (station number 

02358000, pl. 1). Neither of the tests indicated a trend in the 

data for the high-flow regime. Trend assessments also were 

made for the period from 1957 through 2006, which is the 

period of regulated peaks. Kendall’s tau statistic indicated a 

slightly negative trend in the peak-flow data; however, this 

APALACHICOLA RIVER

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

17,000 17,500 18,000 18,500 19,000 19,500

DRAINAGE AREA

P-PERCENT CHANCE EXCEEDANCE

0.2

0.5

1.0

2.0

4.0

10

20

50

STREAMFLOW, IN CUBIC FEET PER SECOND

Chattahoochee-02358000

Blountstown-02358700

Sumatra-02359170

EXPLANATION

Figure 3. Relation of flood streamflow to drainage area for selected streamgaging stations and P-percent chance 

exceedance for the Apalachicola River in Florida.
Flood-Frequency Analysis for Large Streams 17

trend is most likely the result of the drought that persisted 

through much of the last decade of record. Single-mass curve 

results show a decreasing trend. Additionally, an analysis of 

the daily mean flows shows a difference in the pattern of daily 

mean flows after about 1980. This could be because the late 

1960s and 1970s was a relatively wet period in the southeast and not just an issue of changing regulation patterns. A 

peak-flow analysis using only the regulated peaks from 1957 

through 2006 indicates that the log-Pearson Type III distribution provides a reasonable fit of the data. The results for 

selected exceedance probabilities are shown in appendix 3. 

The results displayed herein assume that similar regulation 

patterns will continue in the future.

Trend assessments were made for Apalachicola River 

near Blountstown (station number 02358700, pl. 1). Similar 

to the results at the Chattahoochee streamgage, Kendall’s tau 

statistic and the single-mass curves indicate a slightly negative 

trend in the data. Again, this is assumed to be predominantly 

the result of the drought that occurred during most of the last 

decade. Additionally, similar to the data at Chattahoochee, 

daily-mean flow patterns at the Blountstown streamgage 

changed after about 1980 and are most likely attributed to the 

change in climatic conditions previously discussed. A peakflow analysis using the regulated peaks from 1958 through 

2006 provides a reasonable fit of the data. The results for 

selected exceedance probabilities are shown in appendix 3. 

The results displayed herein assume that similar regulation 

patterns will continue in the future.

Assessments were made for the Apalachicola River 

near Sumatra (station number 02359170, pl. 1) for the period 

of record from 1978 through 2006. An analysis of the daily 

mean flows shows that 2000 through 2006 was a particularly 

dry period, similar to the Chattahoochee and Blountstown 

streamgages. Trend assessments were performed using Kendall’s tau statistic, which provided a value of 0.051. A value 

of less than 0.05 indicates a trend in the data. Similar to the 

Chattahoochee and Blountstown streamgages, the drought 

years at the end of the record are the most probable reason for 

Kendall’s tau indicating a negative trend at the 0.05 significance level. A peak-flow analysis using the regulated peaks 

from 1978 through 2006 provides a reasonable fit of the data. 

The results for selected exceedance probabilities are shown in 

appendix 3. The results displayed herein assume that similar 

regulation patterns will continue in the future.

Suwannee River

The relation of flood flow to drainage area for selected 

exceedance probabilities for the Suwannee River is shown 

in figure 4. Flood flows for selected exceedance probabilities for the Suwannee River near Benton (station number 

02315000, map number 188, pl. 1), at White Springs (station 

number 02315500, map number 190, pl. 1), and at Suwannee 

Springs (station number 02315550, map number 191, pl. 1) 

are given in appendix 1. These flows are the log-Pearson Type 

III analysis, the regional flood equation estimates, and the 

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

DRAINAGE AREA

P-PERCENT CHANCE EXCEEDANCE

0.2

0.5

1.0

2.0

4.0

10

20

50

STREAMFLOW, IN CUBIC FEET PER SECOND

EXPLANATION

Benton-02315000

White Springs-02315500

Suwannee Springs-02315550

Ellaville-02319500

Luraville-02320000

Branford-02320500

Bell-02323000

Wilcox-02323500

SUWANNEE RIVER

Figure 4. Relation of flood streamflow to drainage area for selected streamgaging stations and P-percent chance 

exceedance for the Suwannee River in Florida.
18 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006

weighted estimates between these two calculations. The flood 

flows shown on figure 4 are those of the log-Pearson Type III 

analysis and are based on the period of record from 1973 and 

1976 through 2002 at Benton, 1907 through 1908 and 1928 

through 2006 at White Springs, and 1961 through 1964 and 

1966 through 1996 at Suwannee Springs. 

For the Suwannee River at Ellaville (station number 

02319500, pl. 1), a trend test using Kendall’s tau trend analysis and single-mass curves for the entire period of record from 

1928 through 2006 indicated no change in flow patterns. A 

log-Pearson Type III analysis was performed for the period of 

record and the resulting flood flows for selected exceedance 

probabilities are provided in appendix 3.

For the Suwannee River at Branford (station number 02320500, pl. 1), a trend test using Kendall’s tau trend 

analysis and single-mass curves for the entire period of record 

from 1928 and 1932 through 2006 indicated no change in flow 

patterns. A log-Pearson Type III analysis was performed for 

the period of record and the resulting flood flows for selected 

exceedance probabilities are provided in appendix 3.

For the Suwannee River near Wilcox (station number 

02323500, pl. 1), a trend test using Kendall’s tau trend 

analysis and single-mass curves for the entire period of record 

from 1928, 1931, 1942, and 1944 through 2006 indicated no 

change in flow patterns. A log-Pearson Type III analysis was 

performed for the period of record and the resulting flood 

flows for selected exceedance probabilities are provided in 

appendix 3.

Generally, rainfall from a storm equally dispersed 

throughout a basin means that flood magnitudes will increase 

along with increasing drainage area. This is not the case in the 

Suwannee River between Luraville (station number 02320000, 

pl. 1) and Branford (station number 02320500, pl. 1). A 

decrease in flood magnitude exists that could be due to peak 

attenuation as cross-sectional area increases in a downstream 

direction. A large part of the attenuation is through transient 

stream losses to springs which effectively become sinks at 

periods of high stream levels. The same phenomenon of peak 

attenuation occurs between Worthington Springs (station number 02321500, map number 204, pl. 1) and High Springs on 

the Santa Fe River (station number 02322000, map 

number 209, pl. 1; Giese and Franklin, 1996). 

Rising floodwaters affect wildlife habitats and often cause species to seek safety in unfamilar environments. 

Above: View of a reflector sign near a road near the Suwannee 

River near Ellaville, Florida, gage during the flood of April 2009. 

Ants are maneuvering up the sign to avoid drowning in the 

floodwaters. Photograph by Mark Stephens, USGS.

Above: An emu observes standing water and USGS surveying 

equipment after a heavy rain event in south Florida (circa 

1999–2000). Photographs by Richard Verdi, USGS.
References Cited 19

Summary

Flood flows for selected exceedance probabilities were 

determined for 275 streamgages on natural streams in Florida 

using the log-Pearson Type III frequency distribution. The data 

for these sites in Florida and 30 additional sites in parts of the 

adjacent States of Georgia and Alabama were used to develop 

regional flood-frequency relations that can be used to estimate 

flood flows for the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 

0.2-percent chance exceedance probabilities for ungaged, 

unregulated streams in Florida.

Multiple-regression techniques were used to define four 

hydrologic regions having similar flood characteristics and to 

develop predictive equations relating peak flow to specified 

drainage-basin characteristics. The flood regions were delineated based on plotted residuals, previous flood-frequency 

studies, and geologic, physiographic, and drainage-area maps. 

The most significant variable determined for predicting flood 

flows in Florida was drainage area, followed by storage. Generalized least-squares regression methods were used to define 

the regression coefficients used in the predictive equations and 

both the model and prediction errors. 

The regional flood-frequency relations can be applied 

to streams in Florida that are not significantly affected by 

backwater, regulation, urbanization, or channelization. Methods are presented in this report for determining flood flows 

for selected exceedance probabilities on ungaged and gaged 

streams. On large streams where the regional flood-frequency 

relations do not apply, flood flows for 50-, 20-, 10-, 4-, 2-, 

1-, 0.5-, and 0.2-percent chance exceedance probabilities are 

estimated from graphical relations of flood flows and drainage areas for the Apalachicola River and Suwannee River at 

Ellaville and below.

Acknowledgments

 The authors gratefully acknowledge the peer reviews 

from Tony Gotvald (USGS Hydrologist, Atlanta, Ga.) and 

Larry Bohman (USGS Southeast Regional Surface-Water 

Specialist, Norcross, Ga.) whose contributions enhanced the 

scientific merit of this report. The technical advisement and 

guidance from Scott Hedgecock (USGS Hydrologist, Montgomery, Ala.) during the project and report compilation were 

invaluable. The design and layout of the plate was performed 

by Katie Lee (USGS Civil Engineer, Montgomery, Ala.). 

Assistance with the preparation of the appendixes was 

provided by Peter Nevels (USGS Hydrologic Technician, 

Montgomery, Ala.). Appreciation is extended to Sandra 

Dickerson (USGS Hydrologic Information Assistant, Orlando, 

Fla.) for her assistance with the extensive preparation and 

formatting of the data presented in this report.

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Appendixes and Supplemental Data 21

Appendixes and Supplemental Data

Data for gaging stations in Florida (modified from Hedgecock and Feaster, 2007).

The following appendix tables contain peak stage and discharge data for streamflow 

gaging stations in Alabama. The tables contain a brief description of the gage location, type 

of gage, gage datum (if known), drainage area in square miles, historical data and explanatory 

remarks. Elevations are referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 29).

The tables of peak stages and discharges show only the annual maximums. The qualification codes in the tables correspond to the peak data codes as used in the U.S. Geological Survey 

National Water Information System (NWIS). The following qualification codes apply to the 

discharge columns:

1 discharge is a maximum daily average;

2 discharge is an estimate;

4 discharge is less than indicated value, which is the minimum recordable discharge at this site;

5 discharge affected to unknown degree by regulation or diversion;

6 discharge affected by regulation or diversion;

7 discharge is an historic peak;

A year of occurrence is unknown or not exact;

B month or day of occurrence is unknown or not exact;

E only maximum peak available for this year.

The following qualification codes apply to the gage height columns:

1 gage height affected by backwater;

2 gage height not the maximum for the year;

3 gage height at different data or at different site and datum;

5 gage height is an estimate.

The following abbreviations apply to the tables: 

--, date or data not available; ft, feet; ft3/s, cubic feet per second; mi, mile; mi2, 

square miles. 

The supplemental data for this report includes full descriptions of the streamgages used 

in this study, such as location, datum information, period of record, and any special remarks 

associated with the streamgage (historic flood information, for example). Additionally, the 

peak-flow data are included. These data are available online at 

https://pubs.usgs.gov/sir/2011/5034.

The drainage area data presented in appendixes 1 and 3 are those as defined by the use of 

GIS analysis for this project. The drainage area data presented in the supplemental data are 

those as historically derived and published in the National Water Information System (NWIS).
22 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 1. [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates; —, no data] Station number Map number Station name Drainage area (mi2

)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02327100 229 Sopchoppy River near Sopchoppy, Fla. 105 43.3 46 2440 1850 2420 3780 2640 3710 4700 3200 4600 5880 3940 5710 6770 4560 6560 7660 5160 7390 8560 5820 8220 9770 6710 9340

02327350a 230 Ochlockonee River Tributary near Coolidge, Ga. 1.98 0.30 42 205 142 197 377 306 367 516 449 505 717 675 708 885 866 880 1070 1090 1070 1270 1330 1290 1550 1710 160002327355a 231 Ochlockonee River (State Road 188) near Coolidge, Ga. 256.03 0.65 26 4000 3370 3930 7900 6520 7710 11300 9120 10900 16800 13000 15900 21700 16200 20100 27300 19700 24800 33800 23600 30000 43900 29400 3770002327415a 232 Little Ochlockonee River (State Road 111) near Moultrie, Ga. 44.87 1.00 24 1600 1080 1480 3160 2160 2860 4550 3080 4020 6790 4470 5760 8840 5630 7240 11200 6930 8860 14000 8370 10700 18500 10500 1350002327500a 233 Ochlockonee River near Thomasville, Ga. 559.15 0.60 50 5740 5480 5730 11000 10400 11000 15700 14500 15600 23000 20400 22700 29700 25400 29100 37400 30700 36300 46300 36600 44300 60200 45500 5660002327550a 234 Barnetts Creek near Meigs, Ga. 14.96 0.50 21

826529771

171010901570

248015702240

368023103230

472029204050

590036204950

723043905930

923055707380

02327700a 235 Barnetts Creek near Thomasville, Ga. 106.69 0.90 27 2840 1860 2650 6200 3670 5550 9430 5180 8050 14900 7450 11800 20000 9340 14900 26200 11400 18300 33700 13700 22000 45700 17200 2740002327860a 236 Popple Branch at State Route 179 near Whigham, Ga. 1.66 2.20 26 167 129 161 295 279 292 401 411 403 560 618 577 698 794 729 854 996 906 1030 1220 1110 1290 1570 141002327900a 237 Wolf Creek near Whigham, Ga. 18.47 1.70 27

1130

616

1100

202012601970

275018202680

380026603680

468033704510

565041605420

670050506400

824063907850
Appendix 1 23

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 1.—Continued[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates; —, no data]

Station 

number

Map

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02328000a 238 Tired Creek near Cairo, Ga. 58.2 2.00 36

237013002300

493026004700

745036906920

11800

5340

10400

16100

6710

13500

21500

8250

17000

28200

9940

21000

396001250026900

02329000 239 Ochlockonee River near Havana, Fla. 1140 1.73 81 7480 11700 7640 14200 21700 14600 19700 30500 20300 27700 44300 28900 34400 57000 36300 41600 71600 44500 49400 88700 53800 60800 115000 6750002329180 240 Megginnis Arm Tributary at Tallahassee, Fla. 1.44 0.41 11 271 156 267 328 296 326 366 419 369 414 609 427 450 781 474 486 976 525 523 1200 579 574 1550 65602329354 241 Attapulgus Creek Tributary near Jamieson, Fla. 1.03 0.00 11 91.1 130 101 184 253 207 267 365 305 398 540 461 517 699 603 654 883 768 811 1100 963 1060 1430 126002329490 242 Willacoochee Creek near Quincy, Fla. 64.9 0.10 15 1380 1940 1460 2510 3860 2790 3470 5620 4000 4940 8440 5960 6240 11100 7780 7700 14200 9930 9370 17900 12500 11900 23600 1640002329500 243 Little River near Quincy, Fla. 237 0.24 41

422044904250

948088809370

148001290014300

241001940022600

334002550030600

451003270040000

596004120051200

841005470069400

02329534 244 Quincy Creek at State Hwy 267 at Quincy, Fla. 16.9 1.10 19 704 753 709 1180 1400 1220 1590 1960 1680 2260 2830 2420 2860 3610 3110 3590 4500 3930 4440 5520 4890 5820 7080 638002329558 245 St. Matthews Church Branch near Quincy, Fla. 0.515 0.00 11 73.2 82.0 74.0 105 160 112 128 230 142 159 338 187 183 437 225 209 551 268 235 682 316 273 682 387

02329559 246 Littman Branch near Quincy, Fla. 0.270 2.90 11 25.8 47.0 27.2 36.4 81.0 40.1 43.4 10849.4 52.2 14761.9 58.7 181 71.8 65.2 21782.3 71.7 25793.6 80.3 316 109
24 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 1.—Continued [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates; —, no data] Station number Map number Station name Drainage area (mi2) Storage (per- cent) Period of record (years) Peak flow, in cubic feet per second, for indicated exceedance probability in percent 50 20 10 4 2 1 0.5 0.2 02329600 247 Little River near Midway, Fla. 305 0.46 42 5000 5220 5040 11300 10200 11100 17800 14700 17000 29100 22000 26800 40500 28700 36100 54700 36600 47100 72500 46000 60200 103000 60700 81200 02329700 248 Rocky Comfort Creek near Quincy, Fla. 9.37 0.09 17 628 547 609 1400 1070 1280 2220 1550 1900 3740 2310 2910 5310 3010 3850 7370 3830 4960 10000 4780 6250 14800 6270 8340 02329877 249 Ocklawaha Creek near Wetumpka, Fla. 28.9 3.19 15 616 1000 665 1110 1750 1240 1530 2380 1750 2190 3320 2540 2780 4140 3250 3450 5050 4060 4230 6080 5000 5440 7620 6410 02330000 250 Ochlockonee River near Bloxham, Fla. 1720 2.84 78 9510 14800 9710 18100 26700 18600 25900 37000 26800 38500 52800 40200 50300 67200 52700 64400 83500 67600 81100 103000 85400 108000 132000 113000 02330050 251 Telogia Creek near Greensboro, Fla. 27.8 1.49 22 1430 1030 1350 3060 1890 2680 4690 2630 3850 7570 3770 5650 10400 4790 7270 14100 5940 9100 18700 7270 11200 26500 9290 14500

02330100 252 Telogia Creek near Bristol, Fla. 128 6.66 53

276025102740

52104200

5110

73405570

7110

10700

7560

10100

13600

9290

12700

17000

11200

15600

209001330018800

270001640023600

02330150 253 Ochlockonee River near Smith Creek, Fla. 2100 5.25 11 14800 16000 15100 27300 27800 27400 36900 37600 37100 50100 52300 50800 60600 65600 62400 71500 80200 74800 82900 97200 88600 98800 123000 10900002330200 254 New River at Vilas, Fla. 24.7 35.11 22

520732539

923

1050

944

127012801270

182015901750

232018402150

290020802570

358023503030

464027103680

02330400 255 New River near Sumatra, Fla. 151 43.03 32

253023602520

365033703630

444040904410

548050605440

630059606260

715066407090

803075007960

926086709170
Appendix 1 25

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 1.—Continued[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates; —, no data]

Station 

number

Map 

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02356510 256

South Mosquito Creek 

Tributary near Hardaway, Fla.

0.290 0.00 11

30.956.033.0

46.5

109

53.7

57.9

157

71.3

73.6

230

97.9

86.1

297121

99.4

373148

114

460178

134596223

02356640a 257 Spring Creek (U.S. 27) at Colquitt, Ga. 283 0.10 24 3250 2340 3050 6330 4220 5720 9020 5630 7820 13200 7480 10700 17000 9100 13100 21300 10800 15600 26200 12400 18000 33800 14700 2160002357000a 258 Spring Creek near Iron City, Ga. 468 0.20 65

437033304250

874059408390

12200

7890

11600

171001040015800

21100

1260019200

253001500022500

296001710025700

356002020030200

02358600 259 Flat Creek near Chattahoochee, Fla. 24.9 0.22 21 1050 1030 1050 2100 2010 2070 3120 2900 3050 4910 4310 4650 6680 5610 6170 8920 7130 7970 11700 8910 10100 16500 11700 1360002358800 260 Chipola River at Oakdale, Fla. 565 7.30 12 3430 6600 3690 5100 11000 5660 6190 14700 7060 7540 20000 8920 8520 24600 10400 9470 29700 11900 10400 35500 13600 11600 44000 1580002358946 261 Mockingbird Run near Cypress, Fla. 0.565 0.00 11 16.8 87.0 51.3 87.3 170 145 210 244 237 545 360 385 1020 465 520 1780 586 678 3000 726 860 5680 942 115002358998 262 Holliman Branch near Altha, Fla. 1.92 0.00 18 297 195 280 539 382 502 743 551 689 1050 817 974 1320 1060 1230 1630 1340 1520 1980 1670 1850 2500 2180 236002359000 263 Chipola River near Altha, Fla. 833 6.74 72

463085704690

7310

14500

7500

9460

19300

9840

126002640013400

154003270016600

184003960020200

219004750024300

271005920030600

02359300 264 Sandy Creek near Panama City, Fla. 28.4 10.03 22 1300 903 1280 1930 1450 1890 2360 1870 2310 2920 2470 2860 3340 2980 3290 3760 3520 3720 4200 4120 4180 4780 4970 4810
26 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 1.—Continued [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates; —, no data] Station number Map number Station name Drainage area (mi2

)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02359350 265 Econfina Creek near Compass Lake, Fla. 40.6 9.38 18 739 1150 758 1040 1850 1090 1240 2410 1320 1500 3190 1640 1700 3870 1890 1900 4580 2160 2100 5380 2450 2380 6520 285002359450 266 Econfina Creek near Fountain, Fla. 70.2 11.24 17 997 1620 1010 1300 2580 1340 1480 3330 1550 1710 4390 1820 1870 5300 2030 2030 6260 2240 2180 7330 2460 2380 8850 275002359500 267 Econfina Creek near Bennett, Fla. 122 8.29 68 1300 2390 1310 1800 3910 1840 2180 5140 2240 2710 6900 2840 3140 8430 3350 3620 10100 3920 4120 11900 4550 4870 14600 549002359550 268 Bear Creek near Youngstown, Fla. 57.1 8.69 24 2030 1440 1980 3290 2350 3160 4290 3070 4070 5750 4100 5380 6990 4980 6470 8370 5920 7660 9900 6970 8960 12200 8500 10900

02361000b 269 Choctawhatchee River near Newton, Ala. 686 6.80 75 8870

—

8910

16500

—

16600

23800

—

23700

36400

—

35000

48800

—

45600

64300

—

58500

83700

—

74300

117000

—

101000

02364500b 270 Pea River near Samson, Ala. 1180 6.30 49

12300

—

12400

19800

—

20500

25800

—

27300

34900

—

37600

42800

—

45900

51600

—

55100

61600

—

65400

76900

—

80700

02365200 271 Choctawhatchee River near Pittman, Fla. 3180 2.20 13 27300 22500 26500 44500 41500 43900 56900 58200 57200 73600 84200 76000 86400 108000 91600 99700 136000 109000 113000 168000 128000 132000 217000 15500002365237 272 Fowler Branch near Leonia, Fla. 5.12 0.00 19

381371380

559732572

686

1060

720

855

1580

934

988

2060

1120

1130

26201320

127032701540

148042901870

02365310b 273 Grants Branch Tributary near Fadette, Ala. 1.44 0.00 10 367

—

324

650

—

539

878

—

700

1210

—

943

1490

—

1160

1800

—

1400

2130

—

1660

2630

—

2040
Appendix 1 27

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 1.—Continued[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates; —, no data]

Station 

number

Map 

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02365470 274

Wrights Creek at State 

Highway 177-A near Bonifay, Fla.

151 6.73 13

206027902140

334046703590

442061904850

606084006780

7520

10300

8490

9200

1240010400

11100

1480012700

142001830016000

02365500 275 Choctawhatchee River at Caryville, Fla. 3510 2.92 75 23300 23500 23300 36500 42600 36800 48400 59100 49100 67900 84600 69700 86300 108000 89300 108000 134000 113000 136000 165000 142000 180000 213000 18800002365700 276 Sandy Creek at Ponce De Leon, Fla.. 116 4.67 30 2900 2420 2860 5380 4160 5170 7640 5590 7160 11300 7710 10200 14800 9580 12900 19000 11600 16000 24000 14000 19500 32200 17400 2480002366000 277 Holmes Creek at Vernon, Fla. 393 7.87 36

395051604020

671085706860

8850

11300

9090

11900

1530012300

144001890015000

170002260018000

199002700021200

241003330026000

02366500 278 Choctawhatchee River near Bruce, Fla. 4380 4.69 76 31400 26200 31300 49200 46000 49000 63700 62800 63600 85600 88100 85800 105000 111000 106000 127000 137000 128000 152000 167000 154000 190000 212000 19400002366859 279 Pate Branch near Freeport, Fla. 1.88 0.00 19

169192171

274376287

357543386

479806541

581

1050

679

694

1330

840

820

16501030

101021501310

02367000 280 Alaqua Creek near Defuniak Springs, Fla. 65.8 0.29 26 2360 1930 2320 4270 3780 4190 5940 5460 5840 8590 8130 8470 11000 10600 10900 13800 13500 13700 17100 16900 17000 22300 22300 2230002367006 281 Alaqua Creek near Portland, Fla. 83.8 1.35 15 2620 2130 2530 4830 3960 4600 6700 5560 6340 9560 8030 8990 12100 10300 11400 14900 12800 14000 18200 15800 17100 23100 20300 21700

02367800b 282 Yellow River near Wing, Ala. 461 5.70 12

6350

—

6700

10400

—

11900

14100

—

16500

20200

—

23300

25900

—

28700

32900

—

35000

41300

—

42000

55400

—

52600
28 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 1.—Continued [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates; —, no data] Station number Map number Station name Drainage area (mi2

)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02368000 283 Yellow River at Milligan, Fla. 624 3.88 66

859074108520

179001300017300

273001780025600

444002490039200

619003130051900

845003850066600

113000

4670083700

164000

59100

111000

02368300 284 Baggett Creek near Milligan, Fla. 7.75 0.84 18 320 458 327 460 857 488 561 1210 614 697 1750 800 804 2230 956 917 2780 1130 1040 3420 1330 1200 4390 162002368326 285

Caney Creek Tributary No. 2 

near Caney Creek Tower near Paxton, Fla.

0.190 0.00 11

51.243.048.7

105

83.095.8

154

118

137

235173201

309223259

397280326

502345402

667445520

02368329 286 Caney Creek Tributary No. 1 near Paxton, Fla. 0.140 0.00 11 91.5 31.0 79.7 150 67.0 122 20096.0 157 280 141 211 351 185 260 436 227 316 534 280 381 692 361 48202368500 287 Shoal River near Mossy Head, Fla. 123 6.98 34 3100 2430 3030 5830 4050 5560 8090 5350 7580 11500 7250 10500 14400 8900 12900 17600 10700 15500 21200 12700 18400 26500 15600 2250002369000 288 Shoal River near Crestview, Fla. 474 5.10 68

772060607660

134001040013200

183001400017900

259001940025100

327002420031400

405002940038400

496003550046500

636004440058900

02369500 289 Yellow River near Holt, Fla. 1220 2.90 18

8520

11800

8710

128002120013700

165002930018400

221004170026300

272005300033600

332006570042400

401008060053000

51200

103000

69400

02369800b 290 Blackwater River near Bradley, Ala. 87.7 0.80 36 2450

—

2500

5540

—

5440

8600

—

8000

13800

—

11800

18900

—

15200

25100

—

19300

32700

—

24200

45100

—

31900

02370000 291 Blackwater River near Baker, Fla. 206 4.37 52 4450 3550 4370 9090 6140 8680 13400 8300 12500 20700 11500 18400 27600 14400 23600 35800 17500 29500 45800 21100 36100 61900 26500 46400
Appendix 1 29

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 1.—Continued[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates; —, no data]

Station 

number

Map 

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02370200 292 Big Juniper Creek near Munson, Fla. 34.5 0.48 10 1080 1250 1120 2140 2400 2240 3140 3440 3280 4850 5070 4970 6500 6570 6540 8520 8300 8380 11000 10300 10500 15100 13500 1400002370500 293 Big Coldwater Creek near Milton, Fla. 240 0.89 60 5830 4340 5720 11800 8270 11300 17400 11800 16500 27100 17300 24800 36400 22400 32600 47900 28300 41600 62000 35200 52300 85400 46000 6940002370700 294 Pond Creek near Milton, Fla. 58.7 0.87 27

621

1730

752

149032701880

24504630

3110

433067605320

636087007470

9110

1090010100

128001350013200

196001760018300

02370750 295 Hurricane Branch near Milton, Fla. 2.85 0.13 23 119 250 159 439 485 462 896 697 775 1970 1030 1290 3310 1330 1770 5340 1680 2330 8320 2090 2980 14400 2720 4010

02372500b 296 Conecuh River near Andalusia, Ala. 1340 7.90 58 13800 —13800 23300 —23700 31000 —31800 42100— 43400 51500 —52900 61800 —63300 73200— 74800 90100 —9160002374500b 297 Murder Creek near Evergreen, Ala. 176 1.80 67 3440 —3490 7030 —7130 10600 —10600 16700— 16000 22800— 21000 30400 —27100 39800— 34500 56000 —4680002374970b 298 Sizemore Creek near Robinsville, Ala. 79.4 2.10 12 4610 —3940 7220 —5970 9290 —7520 12300—9860 14900 —11900 17700 —14200 20800— 16800 25500 —2060002375000b 299 Big Escambia Creek at Flomaton, Ala. 330 4.10 37 7180 —7060 13100 —12600 18600 —17400 27800— 24500 36700— 31000 47700 —38800 61000— 48200 83400 —63100

02375500 300 Escambia River near Century, Fla. 3840 2.04 73 38200 25600 37800 58900 47400 58500 74400 66700 74000 95800 96800 95900 113000 125000 114000 132000 157000 134000 152000 194000 155000 180000 253000 187000
30 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 1.—Continued [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates; —, no data] Station number Map number Station name Drainage area (mi2

)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02376000 301 Pine Barren Creek near Barth, Fla. 74.7 0.28 42 3180 2100 3010 7420 4120 6640 11700 5950 10000 19400 8880 15400 27000 11600 20300 36500 14800 26000 48200 18500 32500 68100 24400 4300002376033 302 Escambia River near Molino, Fla. 4150 2.60 26 37600 26500 36800 60700 48400 59100 80800 67600 78400 113000 97200 109000 143000 124000 137000 178000 156000 170000 220000 192000 209000 288000 248000 27100002376079 303 Carpenter Creek at Pensacola, Fla. 8.81 0.22 13 679 519 645 1260 1010 1180 1780 1450 1650 2620 2150 2400 3400 2780 3090 4320 3520 3890 5410 4380 4830 7160 5720 631002376300 304 Brushy Creek near Walnut Hill, Fla. 52.2 2.02 34 2330 1530 2240 4240 2760 4020 5840 3820 5480 8260 5430 7620 10400 6870 9460 12700 8500 11500 15400 10400 13800 19400 13200 1720002376500 305 Perdido River at Barrineau Park, Fla. 394 8.60 66 7640 5130 7400 14000 8450 13300 19300 11100 18100 27600 15000 25300 34900 18400 31500 43300 22000 38300 52800 26200 45800 67500 32200 57200

aCharacteristics are from Gotvald and others, 2009.bCharacteristics are from Hedgecock and Feaster, 2007.
Appendix 1 31

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 2.[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates]

Station 

number

Map

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02228500 1 North Prong St. Marys River at Moniac, Ga. 131 64.4 63 1350 847 1320 2620 1560 2550 3700 2130 3560 5350 2900 5000 6780 3500 6160 8390 4130 7380 10200 4790 8670 12900 5670 1040002229000 2 Middle Prong St. Marys River at Taylor, Fla. 126 23.3 38 985 1020 987 1840 1880 1840 2420 2570 2430 3140 3520 3170 3640 4260 3720 4120 5060 4270 4560 5900 4820 5120 7000 555002230000 3 Turkey Creek at Macclenny, Fla. 21.0 8.02 27 850 415 827 1320 761 1280 1650 1040 1600 2110 1440 2020 2460 1750 2350 2840 2090 2690 3230 2450 3060 3780 2950 356002230500 4

South Prong St. Marys 

River at Glen St. Mary, Fla.

156 5.86 23

219015202130

390028003780

519038505000

693053006630

830064707880

972077409190

11200

9080

10500

132001090012400

02231000 5 St. Marys River near Macclenny, Fla. 707 27.4 80 5550 2860 5440 11100 5290 10700 16000 7250 15200 23800 9920 21800 30700 12000 27000 38600 14300 32600 47800 16600 38500 61900 19700 4670002231230 6 Pigeon Creek at Boulogne, Fla. 9.36 19.8 11 339 212 329 494 387 484 598 529 590 730 724 729 829 879 838 927 1050 953 1030 1220 1070 1160 1460 124002231250 7 Little St. Mary’s River near Hilliard, Fla. 20.0 7.38 30 622 410 608 1110 752 1070 1510 1030 1440 2120 1420 1980 2650 1730 2410 3250 2070 2870 3930 2420 3370 4960 2920 408002231253 8 St Marys River near Gross, Fla. 1360 18.5 13 7740 4640 7610 10500 8610 10300 12400 11800 12300 14900 16200 15100 16900 19700 17300 19000 23400 19800 21100 27300 22400 24200 32500 2610002231268 9 Alligator Creek at Callahan, Fla. 15.0 13.4 23 338 306 336 537 561 539 686 767 694 893 1050 914 1060 1280 1100 1240 1530 1300 1430 1780 1510 1700 2140 1820
32 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 2.—Continued [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates] Station number Map number Station name Drainage area (mi2

)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02231280 10 Thomas Creek near Crawford, Fla. 30.5 4.55 40 822 580 800 1840 1070 1720 2820 1460 2540 4500 2020 3730 6110 2470 4670 8070 2950 5640 10400 3470 6700 14300 4190 813002244320 52 Middle Haw Creek near Korona, Fla. 72.9 24.2 27 717 721 717 1280 1330 1290 1750 1810 1750 2440 2480 2450 3040 3010 3030 3700 3580 3670 4440 4170 4350 5560 4970 533002244420 53 Little Haw Creek near Seville, Fla. 93.0 24.4 51 486 837 496 856 1540 878 1120 2110 1160 1480 2880 1550 1750 3500 1880 2020 4150 2220 2290 4840 2580 2660 5770 308002244473 54 Rice Creek near Springside, Fla. 43.2 24.9 30 793 519 769 1480 953 1430 2000 1300 1910 2690 1780 2540 3230 2160 3000 3780 2570 3470 4340 2990 3940 5090 3570 457002245050 55 Etonia Creek at Bardin, Fla. 219 15.0 24 672 1560 706 1140 2890 1230 1500 3960 1670 2010 5430 2360 2430 6600 2990 2890 7860 3700 3380 9180 4490 4080 11000 567002245140 56 Simms Creek near Bardin, Fla. 46.9 14.6 30 825 608 810 1450 1120 1420 1910 1530 1870 2520 2100 2460 2980 2550 2910 3460 3040 3370 3940 3550 3850 4590 4250 450002245255 57 Deep Creek near Hastings, Fla. 20.7 11.4 32 204 385 214 403 706 426 573 966 614 831 1330 909 1060 1620 1170 1310 1930 1450 1590 2250 1780 2010 3800 256002245260 58 Deep Creek at Spuds, Fla. 51.7 7.07 15 907 742 895 1420 1370 1420 1800 1870 1810 2320 2580 2360 2730 3150 2820 3160 3760 3310 3620 4410 3840 4260 5300 460002245400 59

South Fork Black Creek 

near Camp Blanding, Fla.

33.8 6.70 25

453577464

945

1060

962

142014501420

222020002150

300024402770

395029203450

512034204190

704041205240
Appendix 1 33

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 2.—Continued[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates]

Station 

number

Map

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02245470 60 Greens Creek near Penney Farms, Fla. 14.9 0.18 25 614 516 607 1120 948 1100 1560 1310 1520 2290 1820 2160 2970 2240 2710 3780 2710 3330 4740 3200 4000 6300 3920 500002245500 61 South Fork Black Creek near Penney Farms, Fla. 136 5.49 67 2710 1410 2650 5370 2600 5180 7680 3570 7270 11200 4930 10300 14400 6020 12700 17900 7200 15200 22000 8450 17800 28100 10200 2160002246000 62 North Fork Black Creek near Middleburg, Fla. 177 9.28 76 3860 1510 3750 7140 2780 6910 9630 3820 9250 13000 5250 12300 15700 6390 14500 18400 7630 16700 21300 8930 18900 25100 10700 2170002246150 63 Big Davis Creek at Bayard, Fla. 13.3 17.2 43 239 271 241 467 496 469 650 678 653 913 929 916 1130 1130 1130 1360 1340 1360 1610 1570 1600 1960 1880 194002246200 64 Durbin Creek near Durbin, Fla. 36.7 28.7 33 540 456 534 1090 837 1060 1610 1140 1520 2490 1560 2220 3330 1890 2780 4360 2250 3400 5610 2620 4050 7680 3120 496002246300 65 Ortega River at Jacksonville, Fla. 31.6 1.51 39 865 700 855 1660 1290 1620 2330 1770 2260 3360 2460 3200 4260 3020 3960 5270 3620 4790 6410 4270 5690 8120 5190 697002246460 66 Williamson Creek at Cedar Hills, Fla. 0.920 0.00 19 146 96.0 146 185 175 184 208 240 209 235 335 239 255 413 261 273 499 284 291 591 308 315 726 34002246497 67 Mccoy Creek at Jacksonville, Fla. 3.51 0.00 13 657 219 644 805 401 792 891 824 889 990 770 979 1060 949 1050 1120 1150 1120 1180 1360 1190 1260 1660 129002246522 68 Red Bay Branch Tributary at Jacksonville, Fla. 0.429 0.00 12 124 60.0 112 228 109 197 316 150 260 448 209 344 563 257 408 693 310 478 839 368 554 1060 452 663
34 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 2.—Continued [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates] Station number Map number Station name Drainage area (mi2

)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02246600 69 Trout River at Dinsmore, Fla. 19.0 11.6 25 440 364 435 789 668 775 1100 914 1070 1600 1260 1510 2070 1530 1880 2620 1820 2290 3280 2130 2730 4350 2560 337002246828 70 Pablo Creek at Jacksonville, Fla. 28.1 27.1 29 483 391 476 906 717 887 1230 979 1200 1690 1340 1630 2050 1620 1960 2430 1930 2300 2820 2240 2650 3370 2680 313002246832 71 Cedar Swamp Creek near Jacksonville, Fla. 4.26 34.3 19 151 117 148 259 212 254 338 289 331 443 395 434 525 478 515 609 567 598 695 660 685 813 787 80502246900 72

Moultrie Creek at State 

Highway 207 near St. Augustine, Fla.

17.0 22.8 31

369298363

691545678

917744900

12001020

1180

140012401380

160014701570

179017101770

202020402030

02247000 73 Moultire Creek near St. Augustine, Fla. 24.4 19.2 25 619 384 585 983 705 969 1150 964 1130 1290 1320 1300 1360 1600 1440 1410 1910 1610 1440 2220 1770 1470 2660 198002247200 74 Fish Swamp Outlet near Summer Haven, Fla. 4.62 34.8 29 92.2 12295.5 223 223 223 355 303 342 580 414 522 797 501 668 1060 594 821 1380 692 984 1890 824 120002247480 75 Tiger Bay Canal near Daytona Beach, Fla. 27.0 49.3 25 143 337 151 236 618 254 295 843 319 365 1150 409 412 1390 483 456 1640 561 496 1910 642 545 2270 75502247510 76 Tomoka River near Holly Hill, Fla. 76.8 38.1 42 751 679 747 1430 1250 1420 1970 1710 1950 2740 2330 2680 3360 2820 3270 4020 3340 3880 4720 3880 4510 5710 4610 538002247600 77 Little Tomoka River near Ormond Beach, Fla. 10.0 29.5 21 146 203 148 232 372 240 297 507 315 390 693 427 466 839 526 549 996 636 639 1160 756 769 1380 932
Appendix 1 35

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 2.—Continued[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates]

Station 

number

Map

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02248000 78 Spruce Creek near Samsula, Fla. 33.4 37.2 55 559 408 557 776 749 775 914 1020 916 1080 1400 1090 1210 1690 1220 1320 2000 1350 1440 2330 1480 1600 2770 166002313400 183 Waccasassa River near Bronson, Fla. 220 7.00 23 282 1820 365 614 3360 799 887 4610 1200 1280 6350 1890 1590 7750 2550 1920 9250 3320 2270 10800 4180 2740 13000 547002314200 184 Tenmile Creek at Lebanon Station, Fla. 26.0 32.0 29 607 361 581 1250 661 1150 1840 902 1620 2820 1230 2280 3730 1490 2780 4810 1770 3290 6100 2060 3840 8160 2450 4560

02314500a 185 Suwannee River at Fargo, Ga. 113 52.2 73 3890 5770 4010 7180 10100 7370 9600 13300 9870 12800 17400 13200 15300 21000 16000 17700 24700 18700 20200 28100 21500 23500 33100 2540002314600a 186 Suwanoochee Creek at Dupont, Ga. 93.7 47.0 25 738 1150 761 1280 2120 1330 1680 2860 1760 2200 3850 2340 2600 4710 2810 3000 5640 3310 3400 6480 3820 3940 7760 455002314700a 187

Suwanoochee Creek at 

State Road 187 near Thelma, Ga.

195 30.0 25

1120

1850

1150

184033601910

239045002520

315060003390

377073204130

444087304960

516099805860

6180

11900

7160

02315000 188 Suwannee River near Benton, Fla. 2100 41.0 28 5780 5140 5720 11000 9550 10800 15100 13100 14800 20700 17900 20200 25300 21600 24500 30100 25600 28900 35100 29700 33400 42100 35200 3960002315200 189 Deep Creek near Suwannee Valley, Fla. 77.6 0.00 14 661 1480 708 1120 2730 1270 1500 3770 1820 2080 5260 2740 2600 6490 3630 3200 7830 4670 3880 9280 5830 4940 11300 759002315500 190 Suwannee River at White Springs, Fla. 2430 33.4 81 7240 5870 7190 13200 10900 13100 17500 15000 17400 23000 20400 22900 27100 24700 26900 31100 29300 31000 35100 34100 35000 40300 40400 40300
36 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 2.—Continued [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates] Station number Map number Station name Drainage area (mi2

)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02315550 191 Suwannee River at Suwannee Springs, Fla. 2650 31.5 35 7230 6270 7190 11700 11700 11700 15000 16000 15100 19400 21800 19600 22900 26400 23300 26400 31400 27100 30200 36500 31200 35300 43300 36900

02317500a 192 Alapaha River at Statenville, Ga. 1340 0.800 79 5660 6630 5690 10200 11600 10200 13700 15200 13800 18500 19800 18600 22400 23900 22500 26400 28100 26600 30600 31800 30700 36500 37500 3660002317600a 193 Little River near Statenville, Ga. 239 40.0 23 2170 2110 2160 4290 3820 4230 5930 5100 5820 8200 6790 7960 9990 8270 9640 11800 9840 11300 13700 11300 13000 16300 13400 15400

02317620 194 Alapaha River near Jennings, Fla. 1660 7.47 13 7830 6240 7640 13400 11600 13100 17400 16000 17200 22800 22000 22700 27000 26800 27000 31300 32000 31500 35700 37500 36300 4170 045000 4290002317630 195 Alapaha River near Jasper, Fla. 1720 1.61 32 6680 8180 6730 11200 15200 11400 14700 21000 15200 19900 29200 21000 24300 35800 26100 29200 43000 31800 34500 50700 38000 42300 61300 48500

02317748a 196 Withlacoochee River near Bemiss, Ga. 498 7.20 25 4730 4270 4710 9740 7900 9620 14000 10800 13700 20500 14700 19900 26000 18100 24900 32200 21700 30400 39000 25400 36200 49000 30800 4450002318000a 197 Little River near Adel, Ga. 577 0.800 42

538038905330

920069409120

12000

9250

11900

159001230015700

189001490018600

221001770021700

254002020024800

299002400029100

02318500a 198 Withlacoochee River near Quitman, Ga. 1490 0.700 36 7850 8450 7890 15200 15200 15200 21600 20400 21500 31300 27600 30700 39800 33600 38500 49400 40000 47100 60300 46400 56300 76700 55800 6980002318600a 199 Okapilco Creek near Berlin, Ga. 108 1.00 22 2200 1900 2190 3910 3750 3900 5370 5290 5370 7630 7610 7630 9640 9530 9630 12000 11700 11900 14600 14000 14500 18800 17600 18500
Appendix 1 37

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 2.—Continued[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates]

Station 

number

Map

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02318700a 200

Okapilco Creek at State 

Road 33 near Quitman, Ga.

272 0.00 27

370034403650

742066607230

10600

9310

10200

156001330014700

200001650018600

250002010022800

305002410027300

390003000034100

02319000 201 Withlacoochee River near Pinetta, Fla. 2150 3.32 76 10600 8430 10500 20700 15700 20400 29300 21700 28800 42400 30000 41100 53800 36600 51300 66700 43900 62400 81100 51600 74400 103000 62200 9150002320700 202 Santa Fe River near Graham, Fla. 93.5 33.3 41 460 788 477 921 1450 955 1290 1980 1350 1830 2710 1930 2270 3280 2420 2730 3880 2950 3220 4520 3520 3920 5370 432002321000 203 New River near Lake Butler, Fla. 189 12.7 37 2620 1480 2500 5460 2730 5130 7680 3740 7100 10700 5130 9590 13100 6240 11300 15400 7440 13000 17900 8700 14600 21100 10400 1670002321500 204

Santa Fe River at 

Worthington Springs, Fla.

608 16.5 75

417028804100

858053408390

12100

7330

11700

170001010016300

209001220019600

249001450023000

291001700026400

348002020030900

02321600 205 Olustee Creek near Lulu, Fla. 50.2 1.51 19 725 932 746 1460 1720 1500 2110 2360 2160 3140 3280 3180 4080 4020 4060 5160 4830 5020 6420 5700 6070 8370 6920 760002321700 206 Swift Creek near Lake Butler, Fla. 46.0 30.7 25 477 517 479 782 949 793 1020 1300 1050 1360 1770 1420 1650 2150 1740 1960 2550 2090 2300 2970 2470 2800 3530 302002321800 207 Olustee Creek near Providence, Fla. 163 9.28 12 2850 1430 2720 4320 2640 4120 5310 3630 5070 6580 4990 6280 7530 6080 7210 8480 7250 8170 9440 8490 9180 10700 10200 1060002321975 208

Santa Fe River at U.S. 

Highway 441 near High Springs, Fla.

958 13.1 10

169040002550

6110

74106790

11500

1020010700

221001400016200

331001700020300

473002020024600

649002370029200

943002830035200
38 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 2.—Continued [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates] Station number Map number Station name Drain- age area (mi2

)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02322000 209 Santa Fe River near High Springs, Fla. 965 13.0 41 3560 4020 3590 7300 7450 7310 10300 10200 10300 14600 14100 14500 18100 17100 17900 21700 20400 21400 25600 23800 25100 30900 28400 30100

02322016 210 Blues Creek near Gainsville, Fla. 7.21 2.53 10 124 262 139 221 479 259 298 658 368 411 911 539 504 1120 694 607 1340 866 718 1580 1050 881 1910 133002322049 211 Bad Dog Branch near Alachua, Fla. 0.530 1.60 11 29.7 56.0 35.3 73.0 10182.3 118 139 127 196 193 195 274 236 250 371 284 311 490 335 376 688 408 46902322500 212 Santa Fe River near Fort White, Fla. 1020 12.3 75 3860 4190 3860 6610 7780 6640 8720 10700 8800 11700 14700 11900 14100 17900 14400 16700 21300 17100 19400 24900 20000 23400 29700 2420002324000 213 Steinhatchee River near Cross City, Fla. 350 62.8 56 2050 1560 2030 3870 2880 3810 5340 3940 5230 7480 5360 7230 9250 6460 8820 11200 7640 10500 13300 8870 12200 16300 10500 1460002324400 214 Fenholloway River near Foley, Fla. 60.0 99.3 51 334 478 341 703 877 716 1060 1190 1070 1650 1620 1640 2220 1950 2150 2920 2300 2720 3760 2670 3340 5130 3140 422002324500 215 Fenholloway River at Foley, Fla. 120 74.3 49 543 778 553 1120 1430 1140 1680 1950 1720 2660 2660 2660 3620 3200 3500 4810 3780 4450 6290 4390 5490 8770 5180 698002325000 216 Fenholloway River near Perry Fla. 160 64.0 32 589 959 602 983 1770 1020 1260 2410 1320 1630 3280 1750 1920 3960 2110 2200 4680 2490 2500 5430 2890 2890 6420 346002326000 217 Econfina River near Perry, Fla. 198 13.5 56 632 1500 658 1210 2770 1260 1640 3800 1720 2190 5220 2360 2600 6340 2880 3010 7560 3450 3420 8830 4050 3940 10600 4900
Appendix 1 39

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 2.—Continued[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates]

Station 

number

Map

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02326250 218 Aucilla River near Aucilla, Fla. 353 12.1 11 2020 2190 2030 2990 4050 3080 3650 5560 3840 4480 7640 4880 5090 9300 5740 5700 11100 6650 6310 13000 7610 7120 15500 894002326261 219 Little Aucilla River near Cherry Lake, Fla. 15.4 0.940 17 109 474 150 284 869 397 473 1200 676 821 1660 1160 1180 2040 1600 1630 2460 2100 2200 2900 2640 3190 3530 342002326300 220 Little Aucilla River near Greenville, Fla. 87.0 9.95 12 483 958 527 872 1770 1000 1200 2420 1440 1710 3330 2160 2160 4050 2810 2670 4840 3540 3260 5660 4330 4160 6790 548002326372 221 Palmer Mill Branch at Monticello, Fla. 0.480 0.00 15 14164.0 135 213 117 204 259 160 248 315 224 302 354 276 341 392 333 381 429 394 422 476 485 47802326500 222 Aucilla River at Lamont, Fla. 748 15.5 41 1820 3310 1960 4650 6140 4820 7210 8430 7390 11100 11600 11200 14400 14100 14300 17900 16700 17500 21700 19500 20800 27000 23300 2530002326512 223 Aucilla River near Scanlon, Fla. 822 15.5 23 2000 3510 2050 3220 6510 3410 4230 8940 4640 5750 12300 6640 7080 14900 8520 8600 17700 10700 10300 20700 13100 13000 24700 1680002326574 224 Ward Creek Tributary near Monticello, Fla. 0.059 0.00 11 6.00 18.0 7.44 12.4 32.0 16.2 18.3 44.0 25.0 27.9 61.0 39.6 36.6 75.0 52.9 46.7 90.0 67.8 58.6 10784.3 77.2 132 10902326595 225 Halls Run near Miccosukee, Fla. 0.095 0.00 11 20.4 24.0 21.0 38.8 43.0 39.7 53.8 59.0 55.2 75.9 82.0 78.0 94.6 10197.2 115 122 118 137 144 141 170 177 17402326598 226 Caney Creek near Monticello, Fla. 2.54 0.00 13 235 179 224 504 328 451 753 451 635 1160 629 893 1540 775 1100 1980 936 1310 2500 1110 1550 3330 1360 1890
40 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 2.—Continued [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates] Station number Map number Station name Drainage area (mi2

)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02326838 227

Lafayette Creek, 

Miccosukee Rd (No. 28) Tallahassee, Fla.

9.78 0.55 14

332376339

724689715

1130

949

1060

186013201570

260016201980

355019602440

477023102930

689028203640

02326900 228 St. Marks River near Newport, Fla. 530 8.40 48 1900 3020 1920 2860 5590 2910 3510 7690 3610 4350 10600 4540 4980 12900 5300 5610 15400 6110 6240 18000 6960 7100 21600 8160

aCharacteristics are from Gotvald and others, 2009.
Appendix 1 41

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 3.[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates]

Station 

number

Map

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02234100 28 Deep Creek near Osteen, Fla. 140 30.8 17 803 369 764 1470 698 1360 1950 957 1770 2570 1320 2250 3020 1610 2580 3470 1920 2910 3910 2240 3230 4480 2690 367002234500 29 St. Johns River near Sanford, Fla. 2480 26.8 13 6460 3360 6320 9570 5720 9280 11600 7450 11200 14200 9800 13500 16000 11600 15200 17800 13400 16800 19600 15300 18500 22000 17900 2080002235000 30 Wekiva River near Sanford, Fla. 188 16.6 71 829 653 829 1130 1220 1130 1340 1670 1340 1600 2310 1610 1790 2820 1820 1990 3350 2040 2180 3930 2260 2460 4750 258002235200 31 Blackwater Creek near Cassia, Fla. 115 20.4 45 295 403 296 446 768 452 558 1060 573 714 1480 751 839 1810 905 972 2160 1080 1120 2540 1270 1320 3070 154002236000 32 St. Johns River near Deland, Fla. 2960 25.6 73 7190 3930 7160 10300 6640 10200 12300 8620 12200 14800 11300 14700 16600 13300 16500 18500 15400 18300 20300 17600 20100 22600 20600 2250002236120 33 Deep Creek near Barberville, Fla. 35.4 27.8 26 220 141 216 424 281 408 604 395 567 888 560 796 1140 695 982 1440 838 1180 1780 992 1390 2310 1210 169002236125 34 St. Johns River at Astor, Fla. 3240 25.8 12 9890 4190 9800 12200 7050 12000 13500 9140 13300 14900 12000 14800 15900 14100 15800 16800 16200 16800 17700 18500 17800 18700 21700 1900002236350 35 Green Swamp Run near Eva, Fla. 43.0 41.0 27 56.1 13158.4 109 258 117 150 361 166 207 509 242 251 628 308 297 754 383 344 888 466 408 1070 58502236500 36 Big Creek near Clermont, Fla. 68.1 43.90 48 87.7 17790.8 207 343 215 306 476 319 446 665 474 555 816 602 667 975 738 780 1140 881 931 1370 1080
42 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 3.—Continued [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates] Station number Map number Station name Drainage area (mi2

)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02236700 37 Little Creek near Clermont, Fla. 14.7 43.0 25 69.9 57.0 68.7 166 118 158 248 168 231 367 242 329 464 302 403 566 366 478 671 435 554 816 531 65802237000 38 Palatlakaha River near Mascotte, Fla. 185 39.2 12 188 395 205 390 739 441 553 1010 646 783 1380 954 968 1680 1210 1160 1990 1490 1360 2310 1780 1640 2760 219002239000 39 Ocklawaha River near Ocala, Fla. 1020 31.0 38 938 1600 944 1390 2810 1410 1680 3720 1720 2040 4960 2130 2290 5910 2450 2540 6890 2790 2790 7920 3140 3110 9340 363002240000 40 Ocklawaha River near Conner, Fla. 1200 30.4 59 2040 1820 2150 2880 3180 2890 3420 4190 3430 4060 5580 4100 4520 6640 4590 4970 7720 5080 5400 8880 5580 5960 10500 625002240500 41 Ocklawaha River at Eureka, Fla. 1370 28.3 37 2620 2090 2610 3900 3640 3890 4760 4790 4760 5840 6370 5870 6650 7560 6720 7450 8790 7580 8240 10100 8460 9300 11900 967002240902 42 Prairie Creek near Gainesville, Fla. 112 18.6 23 174 415 190 429 792 472 652 1090 726 984 1520 1120 1260 1870 1450 1550 2240 1810 1860 2630 2190 2280 3190 2730

022409424 43 Moores Pond Tributary near Micanopy, Fla. 0.410 0.180 11 6.60 34.0 11.1 25.0 79.0 43.0 48.4 12382.8 95.2 195 155 145 260 223 210 337 304 293 425 396 433 562 538

02240950 44 Hogtown Creek near Gainesville, Fla. 18.5 6.98 20 566 186 545 946 378 882 1250 541 1130 1710 786 1460 2100 992 1720 2530 1220 2000 3010 1460 2400 3740 1820 274002240954 45 Hogtown Creek near Arredondo, Fla. 41.2 5.56 31 304 378 306 531 745 541 704 1050 728 944 1510 1000 1140 1890 1240 1340 2300 1500 1550 2760 1800 1850 3420 2230
Appendix 1 43

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 3.—Continued[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates]

Station 

number

Map

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02241900 46 Lochloosa Creek at Grove Park, Fla. 37.4 16.0 28 375 201 364 754 399 712 1080 561 986 1570 800 1360 2000 995 1650 2480 1210 1950 3010 1430 2270 3800 1750 270002242451 47 Orange Lake Outlet near Citra, Fla. 1010 16.6 20 104 2260 371 819 3970 1870 2090 5270 3640 5100 7070 6420 8600 8450 8490 13300 9900 10500 19200 11500 12500 29100 13600 1500002243000 48 Orange Creek at Orange Springs, Fla. 470 17.0 58 490 1270 502 997 2290 1040 1410 3080 1490 2020 4190 2180 2520 5050 2790 3050 5960 3460 3620 6940 4210 4430 8310 529002243500 49 Ocklawaha River near Orange Springs, Fla. 2010 27.3 22 3810 2850 3790 5400 4880 5380 6530 6380 6520 8050 8420 8080 9250 9950 9340 10500 11500 10700 11800 13200 12100 13700 15500 1410002243530 50 Bruntbridge Brook at Kenwood, Fla. 4.63 21.2 16 12236.0 116 19278.0 181 238 114 223 295 169 274 336 215 311 375 265 350 412 319 388 461 397 44202244000 51

Ocklawaha River at 

Riverside Lake near Orange Springs, Fla.

2100 35.8 25

428025204230

650043106400

790056307770

958074009380

10800

8730

10500

11800

10100

11600

12900

11500

12700

142001350014100

02262900 87 Boggy Creek near Taft, Fla. 85.0 11.6 47 537 440 535 980 846 974 1340 1180 1320 1860 1660 1830 2290 2040 2250 2760 2460 2700 3280 2910 3190 4020 3560 389002263800 88

Shingle Creek at 

Airport near Kissimmee, Fla.

90.7 11.9 48

579454576

1020

872

1010

136012101350

183017001820

222021002210

264025202620

308029903060

371036403700

02264000 89 Cypress Creek at Vineland, Fla. 29.3 35.0 60 33.2 10835.2 85.8 21691.6 132 304 142 198 432 223 251 536 294 305 647 375 361 765 462 435 930 587
44 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 3.—Continued [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates] Station number Map number Station name Drainage area (mi2

)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02264051 90

Black Lake Outlet at 

S-101a at Buena Vista, Fla.

0.585 6.65 20

61.915.061.3

78.734.077.4

90.152.088.4

105

80.0

103

116

106

115

128134129

140166143

157213165

02264100 91 Bonnet Creek near Vineland, Fla. 51.9 28.0 40 474 187 465 773 366 755 973 511 946 1220 721 1180 1400 890 1340 1570 1070 1500 1740 1260 1660 1960 1530 187002264495 92 Shingle Creek at Campbell, Fla. 180 15.4 36 984 655 980 1380 1230 1380 1640 1680 1650 1980 2330 1990 2220 2840 2260 2460 3390 2530 2700 3980 2820 3030 4810 322002266200 93 Whittenhorse Creek near Vineland, Fla. 12.4 39.6 40 26.8 53.0 27.5 53.7 11056.0 74.1 15778.7 101 226 112 122 284 141 143 345 174 164 410 209 192 502 26002266300 94 Reedy Creek near Vineland, Fla. 84.6 35.2 46 441 235 436 800 454 780 1100 628 1060 1560 875 1450 1970 1070 1760 2430 1280 2100 2950 1500 2450 3740 1810 295002266480 95 Davenport Creek near Loughman, Fla. 43.0 29.0 37 105 159 106 181 315 185 240 441 250 324 623 350 393 771 438 468 928 538 549 1100 649 666 1330 81302269000 96

Kissimmee River 

below Lake Kissimmee near Lake Wales, Fla.

1610 29.3 39

253023202520

483040004780

670052506560

944069509040

11700

8240

11000

14200

9560

13000

16900

11000

15000

208001290017800

02269520 97 Livingston Creek near Frostproof, Fla. 117 24.8 16 262 366 265 408 697 423 515 959 551 661 1330 745 778 1630 915 900 1950 1110 1030 2280 1310 1210 2760 162002269720 98 Morgan Hole Creek near Avon Park, Fla. 14.3 0.470 30 718 416 710 1120 852 1110 1370 1240 1360 1660 1830 1670 1850 2340 1900 2040 2920 2130 2200 3580 2370 2410 4560 2720
Appendix 1 45

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 3.—Continued[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates]

Station 

number

Map

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02270500 99 Arbuckle Creek near De Soto City, Fla. 386 17.4 67 1500 1080 1500 2720 1960 2700 3730 2650 3670 5240 3620 5070 6540 4370 6220 7990 5170 7450 9610 6020 8760 12000 7220 1060002271500 100 Josephine Creek near De Soto City, Fla. 114 22.4 57 363 380 364 659 724 661 884 997 890 1200 1390 1210 1440 1700 1470 1700 2030 1750 1980 2390 2040 2350 2880 246002272000 105 Istokpoga Canal near Cornwell, Fla. 624 91.0 35 856 597 847 1450 1070 1440 1840 1420 1820 2320 1900 2280 2640 2260 2600 2950 2620 2900 3240 3000 3200 3600 3500 358002293694 106

Peace Creek Drainage 

Canal near Dundee, Fla.

58.0 32.7 13

115

186

119

203363217

266505295

348709409

409874506

470

1050

612

531

1230

724

611

1490

886

02293986 107

Peace Creek Drainage 

Canal near Alturas, Fla.

160 21.2 25

537504534

981949979

137013001360

197018001930

251022002420

314026202940

387030603510

501036904330

02293987 108

Peace Creek Drainage 

Canal near Wahneta, Fla.

163 20.9 16

484513485

700965710

842

1320

868

102018301080

1150

22301260

128026601440

140031201640

157037501920

02294068 109 Lulu Lake Outlet at Eloise, Fla. 23.0 44.2 25 52.7 79.0 54.1 113 159 118 165 225 174 243 320 260 309 1290 334 382 481 415 460 568 502 574 691 62602294650 110 Peace River at Bartow, Fla. 378 19.8 66 947 948 948 1680 1800 1680 2280 2430 2280 3160 3320 3170 3910 4010 3920 4740 4740 4740 5660 5510 5630 7020 6600 692002294898 111 Peace River at Fort Meade, Fla. 454 18.1 33 907 1190 912 1480 2150 1500 1900 2900 1950 2480 3940 2610 2950 4760 3160 3440 5610 3760 3960 6530 4410 4690 7810 5360
46 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 3.—Continued [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates] Station number Map number Station name Drainage area (mi2

)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02295013 112 Bowlegs Creek near Fort Meade, Fla. 58.3 13.5 21 407 306 404 622 597 621 773 835 777 969 1180 991 1120 1460 1160 1270 1770 1350 1430 2100 1550 1640 2560 1840

02301900 153 Fox Branch near Socrum, Fla. 9.23 4.88 42 251 133 245 558 277 526 850 402 770 1340 594 1120 1800 757 1410 2350 937 1710 3000 1140 2040 4050 1430 251002301990 154

Hillsborough River 

above Crystal Springs near Zephyrhills, Fla.

82.0 6.02 21

547604552

1270

1160

1250

194016201860

302023002760

400028503490

512034504260

641041005090

837050506270

02302260 155

Itchepakesassa Creek at 

S-582 near Knights, Fla.

32.0 5.70 14

485309484

583615584

641873645

707

1260

721

753

1580

779

796

1930

838

838

2310

898

890

2870

982

02302500 156 Blackwater Creek near Knights, Fla. 110 4.72 56 1080 847 1080 1760 1610 1760 2320 2240 2320 3160 3160 3160 3880 3910 3890 4700 4720 4700 5630 5620 5630 7040 6920 701002303000 157 Hillsborough River near Zephyrhills, Fla. 205 4.62 67 2000 1360 1990 3690 2530 3640 5090 3470 4990 7200 4850 6940 9030 5950 8560 11100 7150 10300 13400 8460 12200 16800 10400 1490002303205 158

Baker Creek at 

Mcintosh Road near Antioch, Fla.

21.7 6.13 15

246223245

443451444

604645612

845935870

1050

11801100

128014401340

154017401630

192021602040

02303350 159 Trout Creek near Sulphur Springs, Fla. 20.6 9.69 33 382 170 365 839 344 772 1230 490 1090 1820 709 1510 2330 892 1810 2880 1090 2110 3470 1310 2420 4330 1620 284002303358 160 Cypress Creek near Darby, Fla. 7.29 2.94 17 172 141 166 528 297 450 889 434 690 1480 645 1010 2000 827 1250 2580 1030 1500 3220 1260 1770 4140 1590 2140
Appendix 1 47

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 3.—Continued[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates]

Station 

number

Map

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02303400 161 Cypress Creek near San Antonio, Fla. 58.8 15.0 44 125 290 132 348 566 368 574 791 605 952 1120 991 1300 1390 1330 1710 1670 1690 2170 1980 2090 2880 2420 264002303420 162

Cypress Creek at 

Worthington Gardens, Fla.

122 20.1 41

365423367

782805784

1140

1110

1140

168015401650

213018902080

263022602520

318026503000

396032103660

02303800 163

Cypress Creek 

near Sulphur Springs, Fla.

168 21.1 43

522524522

1100

983

1090

156013501540

220018602150

272022702630

32502700

3110

380031703610

456038104290

02306289 164 Lake Magdalene Outlet near Lutz, Fla. 2.26 11.0 21 9.60 31.0 12.6 40.9 68.0 48.9 82.6 10089.9 168 151 158 259 194 216 378 243 278 529 296 345 781 373 44002307200 165

Brooker Creek at Van 

Dyke Rd near Citrus Park, Fla.

5.47 13.6 26

35.153.035.7

69.4

112

72.8

100164109

151242170

197309229

252382297

316461375

418576493

02309848 166

South Branch Anclote 

River near Odessa, Fla.

17.1 15.2 37

97.5

116

98.3

215236217

315337318

464487468

589612595

724748731

869894878

1080

1100

1090

02309980 167 Anclote River near Odessa, Fla. 62.7 15.6 11 796 299 736 1460 582 1250 2030 811 1600 2890 1150 2060 3640 1420 2400 4490 1710 2760 5450 2020 3160 6910 2470 373002310000 168 Anclote River near Elfers, Fla. 68.9 15.0 62 776 326 761 1580 633 1520 2300 882 2140 3400 1240 3000 4390 1540 3680 5510 1850 4360 6780 2190 5070 8720 2670 604002310147 169 Hollin Creek near Tarpon Springs, Fla. 8.31 11.1 24 87.0 81.0 86.8 143 169 145 188 245 193 253 359 269 309 456 337 370 562 415 437 678 503 537 846 637
48 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 3.—Continued [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates] Station number Map number Station name Drainage area (mi2

)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02310240 170 Jumping Gully at Loyce, Fla. 43.0 11.1 32 33.6 27246.8 132 537 183 250 755 349 468 1080 663 683 1340 955 941 1630 1290 1240 1930 1640 1710 2380 2140

02310300 171

Pithlachascotee 

River near New Port Richey, Fla.

182 9.69 44

265851276

569

1590

614

854

2180

954

132030401560

176037202140

228044502820

289052403600

386063704800

02310800 172 Withlacoochee River near Eva, Fla. 130 44.8 35 226 282 230 573 535 568 907 733 874 1450 1010 1320 1940 1230 1680 2510 1460 2030 3150 1700 2400 4120 2040 289002310947 173

Withlacoochee 

River near Cumpressco, Fla.

267 38.3 39

934525918

1700

971

1660

223013102160

290017902770

339021703190

385025603590

430029703980

487035304480

02311500 174 Withlacoochee River near Dade City, Fla. 390 30.2 29 1120 797 1100 2420 1450 2300 3540 1950 3240 5220 2650 4500 6670 3200 5420 8250 3760 6320 9990 4360 7230 12500 5190 843002312000 175 Withlacoochee River at Trilby, Fla. 595 34.8 76 1350 1010 1340 2650 1800 2620 3700 2410 3620 5200 3240 5000 6420 3880 6070 7730 4540 7160 9120 5240 8260 11100 6200 974002312180 176

Little Withlacoochee 

River near Tarrytown, Fla.

85.0 37.0 40

295229289

801442750

1250

611

1120

1890

852

1580

240010401870

291012502140

343014602390

4110

17602710

02312200 177 Little Withlacoochee River at Rerdell, Fla. 132 48.0 48 375 274 370 894 521 858 1350 713 1260 2020 984 1790 2580 1200 2180 3170 1420 2540 3810 1650 2890 4690 1970 334002312500 178 Withlacoochee River at Croom, Fla. 819 33.6 67 1510 1300 1510 2970 2300 2940 4100 3060 4040 5670 4090 5520 6910 4890 6640 8200 5700 7760 9520 6570 8890 11300 7750 10400
Appendix 1 49

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 3.—Continued[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates]

Station 

number

Map

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02312600 179 Withlacoochee River near Floral City, Fla. 939 31.1 23 1280 1500 1300 2990 2650 2940 4460 3510 4260 6610 4690 6020 8390 5590 7310 10300 6530 8560 12200 7510 9820 15000 8870 1150002312667 180 Shady Brook near Sumterville, Fla. 8.00 16.6 24 11563.0 113 189 131 185 243 190 238 314 279 310 369 353 367 426 434 427 484 522 493 562 648 58602312720 181

Withlacoochee R at 

Wysong Dam at Carlson, Fla.

1400 27.8 40

142021501430

253037402570

334049103420

441065304590

523077505520

606090106490

6900

10400

7520

8030

12200

8920

02313000 182 Withlacoochee River near Holder, Fla. 1810 23.6 75 2080 2860 2090 3600 4920 3630 4780 6450 4830 6420 8540 6540 7760 10100 7940 9170 11700 9430 10700 13500 11000 12800 15900 13300
50 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 4. [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates] Station number Map number Station name Drainage area (mi2

)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02231342 11

Fort Drum Creek at 

Sunshine State Parkway near Fort Drum, Fla.

52.6 10.6 29

647771657

101014101040

125019301290

153026701610

173032901850

192039602100

210047002350

233057702690

02231396 12 Blue Cypress Creek near Fellsmere, Fla. 105 18.1 10 1840 973 1470 2670 1780 2500 3240 2420 3080 3980 3330 3840 4540 4090 4430 5110 4910 5060 5690 5810 5720 6480 7110 665002231458 13 Wolf Creek near Kenansville, Fla. 8.60 31.6 11 113 163 133 251 306 273 367 422 389 535 584 557 672 718 694 818 861 839 970 1020 996 1180 1240 121002231565 14 Crabgrass Creek near Holopaw, Fla. 30.2 20.9 14 554 422 521 994 779 935 1360 1070 1270 1900 1480 1750 2360 1810 2140 2880 2180 2580 3460 2580 3050 4330 3140 373002231600 15 Jane Green Creek near Deer Park, Fla. 258 15.9 53 2120 1800 2080 4350 3250 4200 6400 4420 6070 9730 6060 8920 12800 7440 11400 16500 8930 14100 20800 10600 17200 27600 13000 2170002232000 16 St. Johns River near Melbourne, Fla. 905 29.0 60 2930 3140 2950 5780 5630 5770 8120 7600 8060 11500 10300 11400 14300 12700 14100 17400 15100 17000 20700 17900 20100 25400 21800 2460002232155 17 Pennywash Creek near Deer Park, Fla. 17.4 7.9 12 505 427 485 886 789 858 1200 1080 1160 1680 1510 1610 2090 1870 2000 2550 2250 2420 3080 2670 2880 3870 3290 357002232200 18 Wolf Creek near Deer Park, Fla. 24.6 6.77 50 977 562 926 1880 1030 1770 2680 1420 2480 3930 1970 3500 5050 2440 4390 6340 2950 5330 7820 3500 6370 10100 4310 791002232400 19 St. Johns River near Cocoa, Fla. 1330 29.9 53 3270 3960 3330 5940 7060 6010 7720 9520 7830 9860 12900 10100 11400 15800 11700 12700 18900 13400 14000 22300 15000 15600 27300 17200
Appendix 1 51

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 4.—Continued[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates]

Station 

number

Map

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02232450 20 Jim Creek near Christmas, Fla. 22.7 16.2 25 704 389 649 1270 719 1150 1770 986 1560 2560 1370 2160 3300 1680 2670 4160 2020 3210 5180 2400 3830 6820 2930 473002232500 21 St. Johns River near Christmas, Fla. 1470 29.5 71 4150 4230 4160 6760 7540 6790 8470 10200 8530 10500 13800 10700 12000 16900 12200 13400 20200 13800 14700 23800 15300 16300 29100 1730002233001 22

Econlockhatchee River 

at Magnolia Ranch near Bithlo, Fla.

35.3 34.1 29

192385214

343712374

445974487

569

1340

639

656

1650

758

739

1970

885

816

23301020

912

2830

1190

02233102 23

Econlockhatchee River 

Tributary near Bithlo, Fla.

1.83 15.8 20

65.281.069.1

143153146

218212216

346296324

468366420

618441524

800522640

1100

638810

02233200 24

Little Econlockhatchee 

River near Union Park, Fla.

27.1 14.6 47

478452475

876834873

116011401160

154015801540

182019501840

210023502140

238027802440

274034002860

02233475 25

Little Econlockhatchee 

River at State Road 434 near Oviedo, Fla.

72.9 11.0 10

1140

933

1110

162017001630

193023301990

232032102450

261039602810

289047603200

317056503590

35406940

 4140

02233500 26 Econlockhatchee River near Chuluota, Fla. 240 12.7 71 2550 1870 2500 4470 3370 4400 5960 4590 5860 8050 6300 7900 9750 7750 9540 11600 9300 11300 13500 11000 13100 16200 13600 1580002234000 27

St. Johns River above 

Lake Harney near Geneva, Fla.

1950 27.4 25

634052006280

868092308710

102001240010200

11900

1690012200

132002060013600

144002460015000

156002910016500

171003560018400

02249007 79

Eau Gallie River at 

Heather Glen Creek at Melbourne, Fla.

3.80 0.750 15

373316362

637587626

860813847

1200

11501180

150014301480

185017401800

224020902180

285026002730
52 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 4.—Continued [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates] Station number Map number Station name Drainage area (mi2

)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02249500 80 Crane Creek at Melbourne, Fla. 10.8 2.25 20 295 475 325 540 876 590 722 1210 796 969 1690 1090 1160 2100 1340 1360 2550 1610 1560 3050 1900 1830 3770 2310

02249518 81

Crane Creek at U.S. 

Highway 1 at Melbourne, Fla.

20.8 2.22 18

690720693

104013201080

132018201380

171025401850

203031502240

239038202700

277045603200

335056603960

02250000 82 Turkey Creek near Palm Bay, Fla. 95.5 2.52 11 1120 1810 1220 1710 3270 1910 2100 4460 2400 2600 6200 3090 2960 7680 3640 3320 9290 4240 3680 11100 4870 4140 13800 577002251000 83

South Prong St. 

Sebastian River near Sebastian, Fla.

39.4 3.71 20

1380

923

1350

190016901890

224023102240

264032102690

294039803020

323048203370

352057403730

390071004230

02251500 84

North Prong Saint 

Sebastian Creek near Micco, Fla.

28.5 16.4 20

575446537

1220

823

1100

1780

1130

1560

365015602220

340019202770

425023103330

520027303950

661033504830

02256000 85 Fisheating Creek near Venus, Fla. 188 11.0 11 1980 1690 1880 3740 3060 3510 5110 4160 4780 7020 5720 6520 8550 7050 7940 10200 8470 9420 11800 10000 11000 14200 12400 1330002256500 86 Fisheating Creek at Palmdale, Fla. 311 12.1 75 3070 2240 3000 5960 4030 5800 8370 5470 8090 12000 7510 11400 15000 9230 14100 18400 11100 17100 22000 13200 20200 27500 16200 2480002273000 102 Kissimmee R at S-65e near Okeechobee, Fla. 2830 23.2 35 5290 7020 5550 10700 12400 10900 15000 16700 15300 21200 22600 21400 26100 27700 26400 31300 33100 31700 36700 39100 37400 44300 47900 4530002293000 103 Orange River near Fort Myers, Fla. 60.0 8.6 11 827 904 853 1690 1650 1670 2500 2260 2390 3870 3130 3460 5160 3860 4400 6730 4650 5410 8630 5520 6540 11700 6790 8230
Appendix 1 53

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 4.—Continued[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates]

Station 

number

Map

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02293050 104

Orange River at 

Buckingham near Fort Myers, Fla.

70.0 8.6 18

621994671

108018101200

147024801660

206034202390

258042203030

317050903770

384060404600

488074405860

02293400 105 Alligator Creek near Punta Gorda, Fla. 27.1 6.4 13 709 608 688 1220 1120 1190 1650 1530 1610 2330 2130 2250 2940 2640 2810 3650 3180 3430 4480 3780 4120 5770 4660 516002295420 113 Payne Creek near Bowling Green, Fla. 116 6.1 32 1000 1540 1070 1980 2780 2100 2830 3800 2990 4150 5250 4380 5300 6480 5590 6610 7810 6950 8100 9290 8470 10400 11500 1080002295630 114 Thompson Branch near Wauchula, Fla. 5.92 0.00 21 285 522 302 430 963 464 530 1330 584 661 1880 757 762 2350 897 865 2870 1060 970 3450 1230 1110 4320 147002295637 115 Peace River at Zolfo Springs, Fla. 790 12.8 74 4080 3940 4080 7240 7040 7230 10000 9510 9960 14300 13000 14200 18300 16000 17900 22900 19200 22200 28300 22700 27100 36800 27900 3460002296260 116 Charlie Creek near Crewsville, Fla. 142 19.0 26 1200 1160 1190 2680 2100 2520 4080 2860 3700 6360 3930 5430 8480 4830 6910 11000 5790 8460 13900 6850 10200 18400 8390 1270002296500 117 Charlie Creek near Gardner, Fla. 326 9.76 57 2070 2500 2100 3640 4490 3690 4980 6090 5070 7070 8370 7230 8960 10300 9160 11200 12400 11400 13700 14700 13900 17700 18100 1780002296750 118 Peace River at Arcadia, Fla. 1330 10.5 77 6410 5890 6380 11400 10400 11400 15900 14100 15700 23000 19200 22500 29500 23600 28600 37300 28400 35600 46400 33700 43500 61000 41500 5580002297088 119

Hawthorn Creek at 

CR760-A near Nocatee, Fla.

44.0 2.90 24

1160

1070

1150

187019401880

239026602430

3110

37103190

368045903820

428055604510

490066305240

579082206320
54 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 4.—Continued [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates] Station number Map number Station name Drainage area (mi2

)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02297100 120 Joshua Creek at Nocatee, Fla. 129 3.21 57 1760 2040 1780 3180 3670 3210 4380 5010 4440 6260 6940 6350 7930 8590 8030 9860 10400 9960 12100 12400 12100 15500 15300 1550002297155 121 Horse Creek near Myakka Head, Fla. 36.8 5.13 29 822 795 818 1550 1460 1530 2190 1990 2150 3200 2770 3090 4120 3430 3910 5190 4140 4820 6440 4930 5850 8400 6090 739002297251 122 Horse Creek near Limestone, Fla. 130 7.23 23 980 1560 1140 2480 2830 2590 3970 3850 3930 6460 5320 5980 8790 6560 7750 11500 7910 9660 14700 9400 11800 19700 11600 1480002297310 123 Horse Creek near Arcadia, Fla. 206 7.12 57 2110 2100 2100 4140 3780 4110 5890 5140 5800 8540 7090 8320 10900 8740 10500 13400 10500 12800 16400 12500 15400 20700 15400 1920002297320 124 Horse Creek near Nocatee, Fla. 217 7.28 22 2490 2150 2420 4960 3870 4680 7160 5270 6610 10700 7260 9440 13900 8950 11900 17600 10800 14500 21900 12800 17400 28700 15800 2180002298123 125 Prairie Creek near Fort Ogden, Fla. 233 14.4 34 1830 1750 1830 2860 3160 2880 3610 4300 3660 4630 5900 4750 5450 7250 5650 6310 8700 6610 7220 10300 7660 8500 12700 917002298202 126 Shell Creek near Punta Gorda, Fla. 373 10.4 36 2840 2660 2820 4670 4780 4680 6000 6480 6040 7790 8890 7900 9170 10900 13600 10600 13100 10900 12100 15600 12600 14100 19200 1490002298608 127 Myakka River at Myakka City, Fla. 121 8.81 33 1970 1390 1880 3830 2520 3570 5600 3440 5050 8600 4750 7280 11500 5850 9240 15100 7050 11300 19400 8370 13700 26800 10300 1730002298760 128 Howard Creek near Sarasota, Fla. 16.4 0.870 18 514 771 599 1280 1410 1330 2040 1940 2000 3310 2730 3040 4500 3400 3930 5900 4130 4900 7550 4940 5980 10100 6150 7580
Appendix 1 55

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 4.—Continued[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates]

Station 

number

Map

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02298830 129 Myakka River near Sarasota, Fla. 229 8.87 70 1960 2070 1960 3610 3730 3610 5050 5070 5050 7340 6980 7290 9400 8600 9280 11800 10300 11500 14600 12300 14100 19000 15100 1800002298928 130

Tributary to Myakka 

River near Venice, Fla.

0.200 0.00 10

181

62.0

107

432

119

229

669166327

1050

238460

1400

299573

1810

366683

2270

440807

2980

548985

02299120 131

Deer Prairie Slough 

at Power Line near North Port, Fla.

24.7 16.5 10

302406315

438752476

531

1030

595

651

1430

763

742

1760

897

834

2110

1050

929

25001200

106030601430

02299160 132

Deer Prairie Slough 

near North Port Charlotte, Fla.

27.1 16.0 12

248436

311

542805633

799

1100

911

1190

15301330

153018801690

191022602080

232026802510

293032803120

02299410 133 Big Slough Canal near Myakka City, Fla. 35.6 9.40 27 518 630 542 1190 1160 1180 1880 1590 1780 3100 2200 2720 4310 2710 3540 5840 3270 4450 7740 3880 5460 10900 4770 697002299800 134 Phillippe Creek at Sarasota, Fla. 45.0 0.79 20 991 1480 1080 2040 2680 2210 3080 3680 3280 4920 5140 5010 6740 6390 6570 9050 7770 8360 11200 9300 10400 16900 11600 1350002299950 135 Manatee River near Myakka Head, Fla. 69.5 3.84 40 1930 1300 1860 3450 2370 3320 4700 3240 4490 6580 4490 6190 8200 5560 7630 10000 6720 9180 12000 8010 10900 15100 9910 1340002300000 136 Manatee River near Bradenton, Fla. 95.9 4.03 27 2420 1570 2260 4530 2850 4200 6240 3890 5740 8770 5380 7900 10900 6660 9680 13200 8050 11500 15800 9590 13600 19500 11900 1660002300018 137 Gamble Creek near Parrish, Fla. 50.8 4.01 13 1260 1060 1170 3150 1920 2480 5200 2630 3620 9040 3660 5260 13100 4530 6680 18300 5480 8150 25100 6520 9820 37000 8070 12300
56 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 4.—Continued [mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates] Station number Map number Station name Drainage area (mi2

)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02300032 138 Braden River near Lorraine, Fla. 29.3 2.12 19 1260 904 1200 2110 1650 2030 2760 2270 2660 3660 3160 3550 4410 3930 4290 5200 4760 5080 6050 5690 5940 7260 7060 720002300034 139

Hickory Hammock 

Creek near Lorraine, Fla.

2.70 0.400 14

126279145

203520238

256721306

323

1020

406

373

1270

485

423

1550

576

472

1860

672

537

2320

 810

023000355 140

Cooper Creek at 

University Parkway near Sarasota, Fla.

9.75 5.11 14

137346157

210642247

260884313

324

1240

410

371

1530

487

418

1850

575

466

2200

 668

529

2720

 802

02300037 141 Cedar Creek near Sarasota, Fla. 0.940 3.22 13 91.6 92.0 91.6 152 175 157 199 243 209 266 344 286 321 428 351 380 520 423 444 620 502 537 764 61802300038 142 Rattlesnake Slough near Sarasota, Fla. 3.99 2.27 14 143 253 171 296 473 348 436 654 509 664 920 767 874 1140 991 1120 1390 1250 1410 1660 1541 1870 2050 197002300039 143 Nonsense Creek near Bradenton, Fla. 1.14 0.44 14 195 160 181 436 301 381 644 419 548 958 595 786 1220 744 984 1520 909 1190 1830 1090 1410 2290 1360 174002300100 144

Little Manatee 

River near Fort Lonesome, Fla.

39.9 6.37 44

694777699

1190

14201200

159019501630

221027002280

275033402840

336040303490

406048004220

5110

59105310

02300200 145

South Fork Little 

Manatee River near Duette, Fla.

8.58 6.71 46

304291303

550541549

732745733

976

1040

983

1170

1290

1180

136015601390

156018501600

183022801910

02300500 146 Little Manatee River near Wimauma, Fla. 154 6.27 68 2650 1830 2570 5220 3310 5010 7530 4500 7140 11300 6210 10400 14700 7670 13200 18700 9250 16200 23400 11000 19700 30900 13600 24900
Appendix 1 57

Appendix 1. Flood-frequency estimates using PeakFQ version 5.2 for Region 4.—Continued[mi2, square miles; peak-flow data: top line, log-Pearson Type III distribution; middle line, regression equation estimates; bottom line, weighted estimates]

Station 

number

Map

number Station name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02300530 147 Cypress Creek near Wimauma, Fla. 7.81 17.8 11 243 192 233 388 358 381 502 494 500 667 686 673 806 846 820 960 1020 982 1130 1200 1160 1380 1470 1420

02300700 148 Bullfrog Creek near Wimauma, Fla. 30.0 2.89 47 1130 840 1090 2260 1540 2150 3280 2110 3070 4940 2940 4470 6460 3650 5680 8260 4420 7000 10400 5270 8490 13700 6520 1070002301000 149

North Prong 

Alafia River at Keysville, Fla.

114 9.96 54

170012801650

333023303210

473031804470

688043806430

876054008060

10900

65009800

13300

7710

11700

16900

9480

14500

02301300 150

South Prong Alafia 

River near Lithia, Fla.

111 19.7 44

733978754

135017801390

186024301920

261033402710

3250

4110

3380

395049304130

472058304950

587071306160

02301350 151 Little Alafia River near Hopewell, Fla. 8.36 0.00 14 496 649 528 858 1190 917 1110 1650 1200 1420 2320 1590 1650 2910 1890 1870 3550 2220 2080 4260 2570 2360 5330 305002301500 152 Alafia River at Lithia, Fla. 317 12.8 74 2620 2220 2580 5520 4000 5340 8560 5430 8020 14200 7450 12400 20000 9160 16440 27700 11000 20900 37700 13000 26200 55600 16000 34200
58 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 2. Variance of prediction values for gaging stations used in Florida regional regression analyses. [USGS, U.S. Geological Survey; no., number; pl., plate; %, percent; G, computed from the Bulletin 17B analysis of the gaging station; W, weighted using equation] USGS station no. Map no. (pl. 1) 50% chance exceed- ance 50% chance exceed- ance 20% chance exceed- ance 20% chance exceed- ance 10% chance exceed- ance 10% chance exceed- ance 4% chance exceed- ance 4% chance exceed- ance 2% chance exceed- ance 2% chance exceed- ance 1% chance exceed- ance 1% chance exceed- ance 0.5% chance exceed- ance 0.5% chance exceed- ance 0.2% chance exceed- ance 0.2% chance exceed- ance G W G W G W G W G W G W G W G W Region 1 02327100 229 0.0014 0.0012 0.0014 0.0013 0.0018 0.0016 0.0030 0.0025 0.0045 0.0036 0.0064 0.0050 0.0090 0.0067 0.0131 0.0094 02327350 230 0.0028 0.0024 0.0032 0.0025 0.0042 0.0032 0.0071 0.0050 0.0100 0.0069 0.0152 0.0092 0.0210 0.0118 0.0306 0.0158 02327355 231 0.0054 0.0039 0.0066 0.0043 0.0095 0.0055 0.0166 0.0082 0.0250 0.0110 0.0361 0.0141 0.0500 0.0174 0.0728 0.0226 02327415 232 0.0057 0.0041 0.0073 0.0046 0.0106 0.0059 0.0191 0.0088 0.0289 0.0117 0.0419 0.0149 0.0582 0.0183 0.0850 0.0236 02327500 233 0.0025 0.0022 0.0032 0.0026 0.0047 0.0035 0.0085 0.0056 0.0128 0.0078 0.0186 0.0103 0.0258 0.0131 0.0376 0.0175 02327550 234 0.0080 0.0051 0.0090 0.0052 0.0120 0.0063 0.0201 0.0090 0.0299 0.0118 0.0429 0.0150 0.0594 0.0184 0.0865 0.0237 02327700 235 0.0068 0.0046 0.0085 0.0050 0.0122 0.0064 0.0216 0.0093 0.0326 0.0122 0.0471 0.0155 0.0653 0.0189 0.0952 0.0243 02327860 236 0.0037 0.0029 0.0047 0.0034 0.0069 0.0045 0.0123 0.0070 0.0186 0.0096 0.0270 0.0124 0.0375 0.0156 0.0547 0.0204 02327900 237 0.0040 0.0031 0.0046 0.0033 0.0063 0.0043 0.0108 0.0065 0.0161 0.0088 0.0232 0.0116 0.0320 0.0145 0.0466 0.0192 02328000 238 0.0044 0.0033 0.0060 0.0040 0.0094 0.0055 0.0179 0.0086 0.0279 0.0115 0.0412 0.0148 0.0579 0.0182 0.0855 0.0236 02329000 239 0.0016 0.0015 0.0018 0.0016 0.0024 0.0020 0.0039 0.0032 0.0058 0.0045 0.0084 0.0061 0.0116 0.0081 0.0169 0.0111 02329180 240 0.0009 0.0009 0.0013 0.0012 0.0022 0.0018 0.0042 0.0034 0.0067 0.0050 0.0099 0.0069 0.0140 0.0092 0.0208 0.0127 02329354 241 0.0138 0.0069 0.0166 0.0070 0.0234 0.0085 0.0407 0.0117 0.0610 0.0148 0.0879 0.0182 0.1216 0.0218 0.1771 0.0276 02329490 242 0.0072 0.0048 0.0091 0.0052 0.0133 0.0066 0.0237 0.0097 0.0358 0.0127 0.0519 0.0160 0.0720 0.0194 0.1051 0.0249 02329500 243 0.0047 0.0035 0.0062 0.0041 0.0093 0.0055 0.0171 0.0084 0.0262 0.0112 0.0382 0.0144 0.0532 0.0178 0.0780 0.0230

02329534 244 0.0040 0.0031 0.0059 0.0040 0.0099 0.0057 0.0204 0.0091 0.0330 0.0123 0.0499 0.0158 0.0714 0.0194 0.1074 0.025002329558 245 0.0036 0.0028 0.0046 0.0033 0.0067 0.0045 0.0121 0.0069 0.0183 0.0095 0.0265 0.0123 0.0368 0.0154 0.0538 0.020302329559 246 0.0035 0.0028 0.0038 0.0029 0.0051 0.0037 0.0085 0.0056 0.0126 0.0077 0.0182 0.0102 0.0252 0.0129 0.0367 0.017302329600 247 0.0047 0.0035 0.0062 0.0041 0.0092 0.0054 0.0170 0.0083 0.0260 0.0112 0.0380 0.0143 0.0529 0.0177 0.0775 0.023002329700 248 0.0110 0.0061 0.0155 0.0068 0.0249 0.0087 0.0488 0.0122 0.0770 0.0156 0.1145 0.0192 0.1620 0.0229 0.2405 0.028802329877 249 0.0068 0.0046 0.0089 0.0051 0.0013 0.0012 0.0248 0.0098 0.0380 0.0129 0.0555 0.0163 0.0774 0.0198 0.1134 0.025402330000 250 0.0015 0.0014 0.0021 0.0018 0.0032 0.0026 0.0060 0.0044 0.0094 0.0063 0.0137 0.0086 0.0192 0.0112 0.0283 0.015202330050 251 0.0076 0.0049 0.0104 0.0056 0.0164 0.0073 0.0315 0.0108 0.0491 0.0140 0.0725 0.0175 0.1020 0.0211 0.1506 0.026802330100 252 0.0023 0.0020 0.0029 0.0023 0.0042 0.0032 0.0075 0.0051 0.0113 0.0072 0.0163 0.0096 0.0226 0.0122 0.0330 0.016402330150 253 0.0115 0.0063 0.0115 0.0590 0.0143 0.0069 0.0235 0.0096 0.0350 0.0126 0.0509 0.0159 0.0711 0.0194 0.1045 0.0249
Appendix 2 59

USGS 

station 

no.

Map 

no.

(pl. 1)

50% 

chance 

exceedance

50% 

chance 

exceedance

20% 

chance 

exceedance

20% 

chance 

exceedance

10% 

chance 

exceedance

10% 

chance 

exceedance

4% 

chance 

exceedance

4% 

chance 

exceedance

2% 

chance 

exceedance

2% 

chance 

exceedance

1% 

chance 

exceedance

1% 

chance 

exceedance

0.5% 

chance 

exceedance

0.5% 

chance 

exceedance

0.2% 

chance 

exceedance

0.2% 

chance 

exceedance

G W G W G W G W G W G W G W G W

02330200 254 0.0044 0.0033 0.0060 0.0040 0.0092 0.0054 0.0176 0.0085 0.0273 0.0114 0.0401 0.0146 0.0563 0.0181 0.0830 0.023402330400 255 0.0013 0.0012 0.0016 0.0014 0.0022 0.0019 0.0040 0.0032 0.0060 0.0046 0.0087 0.0063 0.0120 0.0083 0.0175 0.011402356510 256 0.0046 0.0034 0.0057 0.0040 0.0083 0.0051 0.0149 0.0078 0.0225 0.0105 0.0326 0.0135 0.0452 0.0168 0.0659 0.021802356640 257 0.0056 0.0040 0.0069 0.0044 0.0098 0.0056 0.0172 0.0084 0.0258 0.0111 0.0372 0.0142 0.0516 0.0176 0.0751 0.022802357000 258 0.0026 0.0022 0.0025 0.0021 0.0030 0.0024 0.0049 0.0038 0.0074 0.0054 0.0109 0.0074 0.0153 0.0097 0.0226 0.013402358600 259 0.0065 0.0044 0.0094 0.0053 0.0153 0.0071 0.0305 0.0106 0.0485 0.0140 0.0726 0.0175 0.1030 0.0212 0.1536 0.026902358800 260 0.0045 0.0034 0.0044 0.0032 0.0055 0.0039 0.0089 0.0058 0.0134 0.0080 0.0195 0.0106 0.0273 0.0135 0.0402 0.018002358946 261 0.0749 0.0117 0.0922 0.0107 0.1321 0.0121 0.2327 0.0153 0.3499 0.0186 0.5050 0.0220 0.6996 0.0257 1.0192 0.031602358998 262 0.0059 0.0042 0.0074 0.0046 0.0108 0.0060 0.0192 0.0088 0.0290 0.0117 0.0420 0.0149 0.0568 0.0181 0.0850 0.023602359000 263 0.0008 0.0008 0.0012 0.0011 0.0018 0.0016 0.0035 0.0029 0.0055 0.0043 0.0082 0.0060 0.0115 0.0080 0.0170 0.011202359300 264 0.0022 0.0019 0.0025 0.0021 0.0033 0.0026 0.0056 0.0042 0.0083 0.0058 0.0119 0.0078 0.0164 0.0102 0.0239 0.013802359350 265 0.0020 0.0018 0.0024 0.0020 0.0033 0.0026 0.0056 0.0042 0.0084 0.0059 0.0121 0.0079 0.0167 0.0103 0.0243 0.013902359450 266 0.0013 0.0012 0.0014 0.0013 0.0019 0.0017 0.0032 0.0027 0.0048 0.0039 0.0069 0.0053 0.0096 0.0070 0.0140 0.009802359500 267 0.0004 0.0004 0.0007 0.0006 0.0011 0.0010 0.0022 0.0019 0.0035 0.0030 0.0053 0.0043 0.0075 0.0058 0.0112 0.008302359550 268 0.0028 0.0024 0.0038 0.0029 0.0057 0.0040 0.0105 0.0064 0.0161 0.0088 0.0235 0.0116 0.0328 0.0147 0.0482 0.019502361000 269 0.0015 0.0013 0.0022 0.0019 0.0037 0.0029 0.0077 0.0052 0.0126 0.0077 0.0192 0.0105 0.0275 0.0135 0.0415 0.018302364500 270 0.0013 0.0012 0.0018 0.0016 0.0029 0.0024 0.0056 0.0042 0.0088 0.0060 0.0129 0.0083 0.0182 0.0108 0.0269 0.014802365200 271 0.0060 0.0042 0.0064 0.0042 0.0083 0.0051 0.0138 0.0075 0.0205 0.0100 0.0295 0.0129 0.0410 0.0161 0.0599 0.021102365237 272 0.0023 0.0020 0.0029 0.0023 0.0041 0.0032 0.0073 0.0050 0.0110 0.0070 0.0158 0.0094 0.0219 0.0120 0.0319 0.016202365310 273 0.0101 0.0058 0.0120 0.0060 0.0167 0.0074 0.0289 0.0104 0.0431 0.0135 0.0621 0.0168 0.0859 0.0203 0.1251 0.025902365470 274 0.0052 0.0038 0.0074 0.0046 0.0120 0.0063 0.0240 0.0097 0.0382 0.0130 0.0572 0.0164 0.0812 0.0201 0.1211 0.025702365500 275 0.0008 0.0008 0.0013 0.0012 0.0023 0.0020 0.0054 0.0041 0.0094 0.0064 0.0149 0.0090 0.0221 0.0121 0.0344 0.016802365700 276 0.0037 0.0029 0.0051 0.0036 0.0082 0.0051 0.0159 0.0081 0.0250 0.0110 0.0371 0.0142 0.0524 0.0177 0.0777 0.023002366000 277 0.0024 0.0021 0.0028 0.0023 0.0039 0.0030 0.0067 0.0048 0.0100 0.0066 0.0144 0.0089 0.0200 0.0114 0.0291 0.015402366500 278 0.0008 0.0007 0.0011 0.0010 0.0018 0.0016 0.0036 0.0030 0.0058 0.0045 0.0087 0.0063 0.0124 0.0085 0.0186 0.011802366859 279 0.0036 0.0029 0.0047 0.0034 0.0071 0.0046 0.0131 0.0073 0.0200 0.0099 0.0292 0.0129 0.0407 0.0161 0.0596 0.021102367000 280 0.0039 0.0031 0.0053 0.0037 0.0082 0.0051 0.0155 0.0080 0.0240 0.0108 0.0352 0.0139 0.0494 0.0173 0.0727 0.022502367006 281 0.0074 0.0048 0.0093 0.0053 0.0135 0.0067 0.0240 0.0097 0.0362 0.0127 0.0524 0.0160 0.0727 0.0195 0.1060 0.025002367800 282 0.0060 0.0042 0.0092 0.0052 0.0163 0.0073 0.0364 0.0113 0.0613 0.0148 0.0954 0.0186 0.1396 0.0224 0.2140 0.028302368000 283 0.0023 0.0020 0.0034 0.0026 0.0056 0.0039 0.0112 0.0067 0.0180 0.0094 0.0270 0.0124 0.0385 0.0158 0.0576 0.0208

Appendix 2. Variance of prediction values for gaging stations used in Florida regional regression analyses.—Continued[USGS, U.S. Geological Survey; no., number; pl., plate; %, percent; G, computed from the Bulletin 17B analysis of the gaging station; W, weighted using equation]
60 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 2. Variance of prediction values for gaging stations used in Florida regional regression analyses.—Continued [USGS, U.S. Geological Survey; no., number; pl., plate; %, percent; G, computed from the Bulletin 17B analysis of the gaging station; W, weighted using equation; %, percent] USGS station no. Map no. (pl. 1) 50% chance exceed- ance 50% chance exceed- ance 20% chance exceed- ance 20% chance exceed- ance 10% chance exceed- ance 10% chance exceed- ance 4% chance exceed- ance 4% chance exceed- ance 2% chance exceed- ance 2% chance exceed- ance 1% chance exceed- ance 1% chance exceed- ance 0.5% chance exceed- ance 0.5% chance exceed- ance 0.2% chance exceed- ance 0.2% chance exceed- ance G W G W G W G W G W G W G W G W 02368326 285 0.0140 0.0070 0.0176 0.0072 0.0256 0.0088 0.0457 0.0120 0.0690 0.0153 0.0998 0.0187 0.1385 0.0223 0.2020 0.0281 02368329 286 0.0064 0.0044 0.0094 0.0053 0.0157 0.0072 0.0323 0.0108 0.0522 0.0142 0.0789 0.0178 0.1129 0.0216 0.1696 0.0274 02368500 287 0.0036 0.0029 0.0042 0.0031 0.0058 0.0040 0.0100 0.0062 0.0149 0.0084 0.0214 0.0111 0.0296 0.0140 0.0431 0.0186 02369000 288 0.0013 0.0012 0.0018 0.0016 0.0028 0.0023 0.0053 0.0040 0.0082 0.0058 0.0120 0.0079 0.0168 0.0103 0.0248 0.0141 02369500 289 0.0027 0.0023 0.0042 0.0031 0.0074 0.0048 0.0167 0.0082 0.0281 0.0116 0.0439 0.0151 0.0642 0.0188 0.0986 0.0245 02369800 290 0.0056 0.0040 0.0070 0.0044 0.0101 0.0057 0.0179 0.0086 0.0270 0.0114 0.0391 0.0145 0.0542 0.0179 0.0790 0.0231 02370000 291 0.0029 0.0024 0.0038 0.0029 0.0057 0.0040 0.0104 0.0064 0.0159 0.0088 0.0232 0.0116 0.0323 0.0146 0.0473 0.0193 02370200 292 0.0136 0.0069 0.0188 0.0074 0.0296 0.0092 0.0569 0.0127 0.0888 0.0160 0.1312 0.0196 0.1846 0.0233 0.2728 0.0292 02370500 293 0.0024 0.0020 0.0032 0.0026 0.0051 0.0037 0.0097 0.0061 0.0151 0.0085 0.0223 0.0113 0.0313 0.0144 0.0462 0.0191 02370700 294 0.0082 0.0051 0.0116 0.0059 0.0187 0.0078 0.0369 0.0113 0.0583 0.0147 0.0869 0.0182 0.1231 0.0219 0.1831 0.0277 02370750 295 0.0219 0.0085 0.0285 0.0085 0.0426 0.0101 0.0780 0.0135 0.1190 0.0168 0.1732 0.0203 0.2412 0.0240 0.3531 0.0299 02372500 296 0.0014 0.0013 0.0018 0.0016 0.0026 0.0022 0.0046 0.0036 0.0070 0.0052 0.0101 0.0070 0.0140 0.0092 0.0204 0.0126 02374500 297 0.0022 0.0019 0.0031 0.0024 0.0049 0.0036 0.0096 0.0060 0.0150 0.0085 0.0223 0.0113 0.0314 0.0144 0.0466 0.0192 02374970 298 0.0049 0.0036 0.0067 0.0043 0.0104 0.0058 0.0197 0.0089 0.0306 0.0120 0.0451 0.0152 0.0632 0.0187 0.0932 0.0242 02375000 299 0.0028 0.0023 0.0041 0.0031 0.0069 0.0045 0.0141 0.0076 0.0227 0.0105 0.0343 0.0138 0.0491 0.0173 0.0736 0.0226 02375500 300 0.0008 0.0007 0.0010 0.0009 0.0014 0.0013 0.0025 0.0022 0.0038 0.0032 0.0055 0.0044 0.0076 0.0059 0.0111 0.0083

02376000 301 0.0051 0.0037 0.0065 0.0042 0.0095 0.0056 0.0172 0.0084 0.0260 0.0112 0.0378 0.0143 0.0525 0.0177 0.0767 0.022902376033 302 0.0025 0.0022 0.0038 0.0029 0.0067 0.0044 0.0144 0.0077 0.0239 0.0108 0.0368 0.0142 0.0534 0.0178 0.0812 0.023302376079 303 0.0085 0.0053 0.0116 0.0059 0.0181 0.0077 0.0344 0.0111 0.0535 0.0143 0.0787 0.0178 0.1105 0.0215 0.1629 0.027202376300 304 0.0032 0.0026 0.0040 0.0030 0.0057 0.0040 0.0100 0.0062 0.0150 0.0085 0.0216 0.0112 0.0300 0.0141 0.0437 0.018702376500 305 0.0016 0.0014 0.0021 0.0018 0.0031 0.0025 0.0056 0.0042 0.0086 0.0060 0.0125 0.0081 0.0173 0.0105 0.0254 0.0143

Region 2

02228500 1 0.0021 0.0019 0.0025 0.0022 0.0035 0.0029 0.0060 0.0044 0.0082 0.0059 0.0114 0.0075 0.0154 0.0094 0.0219 0.012202229000 2 0.0043 0.0036 0.0031 0.0027 0.0034 0.0029 0.0063 0.0048 0.0104 0.0070 0.0162 0.0094 0.0235 0.0120 0.0354 0.015402230000 3 0.0022 0.0020 0.0026 0.0023 0.0036 0.0030 0.0061 0.0047 0.0091 0.0064 0.0131 0.0083 0.0181 0.0104 0.0264 0.013402230500 4 0.0049 0.0041 0.0049 0.0040 0.0062 0.0047 0.0101 0.0067 0.0150 0.0088 0.0218 0.0110 0.0305 0.0136 0.0448 0.017002231000 5 0.0018 0.0017 0.0022 0.0020 0.0031 0.0027 0.0054 0.0043 0.0081 0.0058 0.0117 0.0077 0.0162 0.0097 0.0236 0.012702231230 6 0.0042 0.0036 0.0045 0.0037 0.0060 0.0046 0.0099 0.0067 0.0147 0.0086 0.0212 0.0109 0.0293 0.0133 0.0428 0.016702231250 7 0.0033 0.0029 0.0042 0.0035 0.0061 0.0047 0.0110 0.0071 0.0167 0.0093 0.0242 0.0116 0.0336 0.0142 0.0491 0.017602231253 8 0.0020 0.0019 0.0028 0.0024 0.0042 0.0035 0.0080 0.0057 0.0123 0.0078 0.0181 0.0100 0.0253 0.0124 0.0373 0.015802231268 9 0.0029 0.0026 0.0034 0.0030 0.0049 0.0039 0.0085 0.0060 0.0127 0.0079 0.0183 0.0101 0.0253 0.0124 0.0369 0.0157
Appendix 2 61

USGS 

station 

no.

Map 

no.

(pl. 1)

50% 

chance 

exceedance

50% 

chance 

exceedance

20% 

chance 

exceedance

20% 

chance 

exceedance

10% 

chance 

exceedance

10% 

chance 

exceedance

4% 

chance 

exceedance

4% 

chance 

exceedance

2% 

chance 

exceedance

2% 

chance 

exceedance

1% 

chance 

exceedance

1% 

chance 

exceedance

0.5% 

chance 

exceedance

0.5% 

chance 

exceedance

0.2% 

chance 

exceedance

0.2% 

chance 

exceedance

G W G W G W G W G W G W G W G W

02231280 10 0.0049 0.0040 0.0060 0.0047 0.0087 0.0060 0.0155 0.0088 0.0233 0.0110 0.0337 0.0134 0.0466 0.0160 0.0680 0.019502244320 52 0.0038 0.0033 0.0046 0.0038 0.0066 0.0050 0.0117 0.0074 0.0176 0.0096 0.0254 0.0119 0.0352 0.0144 0.0512 0.017802244420 53 0.0022 0.0020 0.0021 0.0019 0.0025 0.0022 0.0041 0.0034 0.0062 0.0048 0.0091 0.0065 0.0129 0.0084 0.0191 0.011202244473 54 0.0047 0.0039 0.0043 0.0036 0.0051 0.0041 0.0084 0.0060 0.0128 0.0080 0.0189 0.0102 0.0267 0.0128 0.0396 0.016202245050 55 0.0036 0.0031 0.0042 0.0035 0.0058 0.0045 0.0100 0.0067 0.0150 0.0087 0.0216 0.0110 0.0299 0.0134 0.0435 0.016802245140 56 0.0037 0.0032 0.0036 0.0030 0.0044 0.0036 0.0071 0.0053 0.0107 0.0071 0.0156 0.0092 0.0220 0.0116 0.0324 0.014802245255 57 0.0046 0.0038 0.0052 0.0041 0.0071 0.0052 0.0120 0.0075 0.0178 0.0096 0.0256 0.0125 0.0354 0.0145 0.0515 0.017902245260 58 0.0041 0.0035 0.0049 0.0040 0.0069 0.0051 0.0119 0.0075 0.0178 0.0096 0.0256 0.0119 0.0354 0.0145 0.0515 0.017902245400 59 0.0063 0.0050 0.0084 0.0059 0.0128 0.0077 0.0238 0.0109 0.0365 0.0133 0.0534 0.0158 0.0746 0.0184 0.1095 0.021902245470 60 0.0041 0.0035 0.0058 0.0045 0.0092 0.0062 0.0179 0.0095 0.0281 0.0120 0.0417 0.0145 0.0588 0.0173 0.0872 0.020802245500 61 0.0022 0.0020 0.0025 0.0022 0.0035 0.0030 0.0060 0.0046 0.0090 0.0063 0.0130 0.0082 0.0180 0.0104 0.0261 0.013402246000 62 0.0018 0.0016 0.0017 0.0016 0.0050 0.0018 0.0033 0.0029 0.0050 0.0040 0.0074 0.0055 0.0103 0.0073 0.0153 0.009802246150 63 0.0035 0.0030 0.0036 0.0030 0.0045 0.0036 0.0074 0.0054 0.0110 0.0072 0.0159 0.0093 0.0222 0.0116 0.0325 0.014902246200 64 0.0044 0.0037 0.0059 0.0046 0.0091 0.0062 0.0171 0.0093 0.0264 0.0117 0.0388 0.0142 0.0543 0.0169 0.0799 0.020402246300 65 0.0033 0.0029 0.0040 0.0033 0.0055 0.0043 0.0096 0.0065 0.0143 0.0085 0.0206 0.0107 0.0285 0.0132 0.0415 0.016502246460 66 0.0009 0.0009 0.0010 0.0010 0.0013 0.0012 0.0022 0.0020 0.0033 0.0029 0.0048 0.0039 0.0066 0.0052 0.0096 0.007102246497 67 0.0011 0.0010 0.0011 0.0010 0.0014 0.0013 0.0023 0.0021 0.0034 0.0030 0.0050 0.0041 0.0069 0.0054 0.0101 0.007402246522 68 0.0095 0.0068 0.0116 0.0074 0.0165 0.0090 0.0289 0.0119 0.0433 0.0141 0.0625 0.0164 0.0865 0.0191 0.1260 0.022502246600 69 0.0039 0.0034 0.0055 0.0043 0.0089 0.0061 0.0174 0.0094 0.0275 0.0119 0.0408 0.0144 0.0578 0.0172 0.0857 0.020802246828 70 0.0047 0.0039 0.0046 0.0038 0.0057 0.0044 0.0094 0.0064 0.0140 0.0084 0.0204 0.0106 0.0245 0.0132 0.0419 0.016602246832 71 0.0051 0.0042 0.0052 0.0041 0.0065 0.0049 0.0107 0.0070 0.0160 0.0090 0.0231 0.0114 0.0322 0.0139 0.0473 0.017302246900 72 0.0052 0.0043 0.0040 0.0033 0.0044 0.0036 0.0078 0.0056 0.0127 0.0079 0.0196 0.0104 0.0283 0.0131 0.0425 0.016602247000 73 0.0074 0.0056 0.0021 0.0019 0.0047 0.0038 0.0155 0.0088 0.0266 0.0117 0.0384 0.0141 0.0499 0.0164 0.0633 0.019102247200 74 0.0084 0.0062 0.0098 0.0066 0.0136 0.0080 0.0232 0.0108 0.0347 0.0131 0.0499 0.0154 0.0690 0.0181 0.1005 0.021502247480 75 0.0042 0.0036 0.0041 0.0034 0.0034 0.0029 0.0062 0.0048 0.0102 0.0069 0.0159 0.0093 0.0231 0.0119 0.0347 0.015302247510 76 0.0034 0.0029 0.0034 0.0029 0.0043 0.0035 0.0070 0.0052 0.0105 0.0070 0.0152 0.0090 0.0212 0.0114 0.0311 0.014602247600 77 0.0030 0.0027 0.0038 0.0032 0.0056 0.0044 0.0100 0.0067 0.0152 0.0088 0.0220 0.0111 0.0306 0.0136 0.0447 0.017002248000 78 0.0006 0.0006 0.0007 0.0006 0.0009 0.0008 0.0014 0.0013 0.0021 0.0019 0.0031 0.0027 0.0043 0.0036 0.0063 0.005102313400 183 0.0097 0.0069 0.0086 0.0060 0.0101 0.0067 0.0167 0.0091 0.0256 0.0115 0.0380 0.0141 0.0540 0.0168 0.0804 0.020402314200 184 0.0054 0.0044 0.0068 0.0051 0.0099 0.0066 0.0178 0.0095 0.0270 0.0118 0.0391 0.0142 0.0543 0.0169 0.0793 0.020402314500 185 0.0019 0.0017 0.0017 0.0016 0.0020 0.0018 0.0033 0.0028 0.0050 0.0040 0.0074 0.0056 0.0106 0.0074 0.0157 0.0100

Appendix 2. Variance of prediction values for gaging stations used in Florida regional regression analyses.—Continued[USGS, U.S. Geological Survey; no., number; pl., plate; %, percent; G, computed from the Bulletin 17B analysis of the gaging station; W, weighted using equation]
62 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 2. Variance of prediction values for gaging stations used in Florida regional regression analyses.—Continued [USGS, U.S. Geological Survey; no., number; pl., plate; %, percent; G, computed from the Bulletin 17B analysis of the gaging station; W, weighted using equation] USGS station no. Map no. (pl. 1) 50% chance exceed- ance 50% chance exceed- ance 20% chance exceed- ance 20% chance ex- ceed- ance 10% chance exceed- ance 10% chance exceed- ance 4% chance exceed- ance 4% chance exceed- ance 2% chance exceed- ance 2% chance exceed- ance 1% chance exceed- ance 1% chance exceed- ance 0.5% chance exceed- ance 0.5% chance exceed- ance 0.2% chance exceed- ance 0.2% chance exceed- ance G W G W G W G W G W G W G W G W 02314600 186 0.0043 0.0037 0.0041 0.0034 0.0050 0.0040 0.0081 0.0058 0.0123 0.0077 0.0180 0.0100 0.0253 0.0124 0.0374 0.0158 02314700 187 0.0030 0.0027 0.0036 0.0031 0.0050 0.0040 0.0087 0.0061 0.0130 0.0080 0.0187 0.0102 0.0259 0.0126 0.0377 0.0159 02315000 188 0.0051 0.0042 0.0050 0.0040 0.0062 0.0047 0.0101 0.0068 0.0152 0.0088 0.0220 0.0111 0.0308 0.0136 0.0454 0.0171 02315200 189 0.0057 0.0046 0.0078 0.0056 0.0122 0.0075 0.0234 0.0109 0.0365 0.0133 0.0538 0.0158 0.0757 0.0185 0.1117 0.0220 02315500 190 0.0017 0.0016 0.0014 0.0013 0.0016 0.0015 0.0028 0.0024 0.0043 0.0036 0.0065 0.0050 0.0093 0.0067 0.0139 0.0092 02315550 191 0.0022 0.0020 0.0024 0.0021 0.0031 0.0027 0.0052 0.0041 0.0077 0.0056 0.0111 0.0074 0.0154 0.0094 0.0224 0.0123 02317500 192 0.0015 0.0014 0.0015 0.0014 0.0019 0.0018 0.0032 0.0027 0.0047 0.0038 0.0068 0.0052 0.0095 0.0068 0.0139 0.0092 02317600 193 0.0072 0.0055 0.0066 0.0050 0.0079 0.0056 0.0129 0.0079 0.0197 0.0101 0.0290 0.0126 0.0410 0.0153 0.0609 0.0189 02317620 194 0.0075 0.0057 0.0076 0.0055 0.0094 0.0064 0.0155 0.0088 0.0231 0.0110 0.0335 0.0134 0.0467 0.0161 0.0687 0.0196 02317630 195 0.0025 0.0022 0.0031 0.0027 0.0046 0.0037 0.0081 0.0058 0.0123 0.0078 0.0178 0.0099 0.0247 0.0123 0.0361 0.0156 02317748 196 0.0068 0.0053 0.0073 0.0054 0.0095 0.0064 0.0158 0.0089 0.0234 0.0110 0.0337 0.0134 0.0467 0.0160 0.0682 0.0195 02318000 197 0.0023 0.0021 0.0024 0.0021 0.0031 0.0026 0.0051 0.0040 0.0075 0.0055 0.0108 0.0073 0.0151 0.0093 0.0220 0.0122 02318500 198 0.0038 0.0033 0.0045 0.0037 0.0062 0.0047 0.0107 0.0070 0.0160 0.0091 0.0230 0.0113 0.0319 0.0138 0.0464 0.0172 02318600 199 0.0044 0.0037 0.0059 0.0045 0.0089 0.0061 0.0166 0.0091 0.0255 0.0115 0.0373 0.0140 0.0521 0.0166 0.0764 0.0202 02318700 200 0.0056 0.0046 0.0065 0.0049 0.0088 0.0061 0.0151 0.0086 0.0225 0.0108 0.0323 0.0132 0.0447 0.0158 0.0651 0.0193

02319000 201 0.0018 0.0017 0.0021 0.0019 0.0029 0.0025 0.0050 0.0040 0.0074 0.0055 0.0107 0.0072 0.0148 0.0092 0.0216 0.012102320700 202 0.0040 0.0034 0.0040 0.0033 0.0049 0.0039 0.0080 0.0058 0.0120 0.0076 0.0175 0.0098 0.0245 0.0122 0.0361 0.015602321000 203 0.0055 0.0045 0.0047 0.0038 0.0053 0.0042 0.0090 0.0062 0.0140 0.0084 0.0211 0.0108 0.0302 0.0135 0.0452 0.017002321500 204 0.0025 0.0023 0.0023 0.0020 0.0027 0.0024 0.0044 0.0036 0.0068 0.0051 0.0100 0.0069 0.0142 0.0090 0.0211 0.011902321600 205 0.0078 0.0059 0.0095 0.0065 0.0135 0.0080 0.0237 0.0109 0.0355 0.0132 0.0512 0.0156 0.0709 0.0182 0.1033 0.021602321700 206 0.0029 0.0026 0.0034 0.0030 0.0054 0.0042 0.0096 0.0065 0.0145 0.0086 0.0210 0.0108 0.0291 0.0133 0.0424 0.016602321800 207 0.0047 0.0039 0.0050 0.0040 0.0064 0.0048 0.0105 0.0069 0.0156 0.0089 0.0225 0.0112 0.0312 0.0137 0.0457 0.017102321975 208 0.0560 0.0167 0.0566 0.0149 0.0710 0.0154 0.1164 0.0173 0.1735 0.0187 0.2514 0.0205 0.3508 0.0229 0.5152 0.026002322000 209 0.0045 0.0038 0.0042 0.0035 0.0051 0.0040 0.0083 0.0059 0.0125 0.0078 0.0184 0.0101 0.0259 0.0126 0.0383 0.016002322016 210 0.0104 0.0072 0.0121 0.0076 0.0166 0.0090 0.0283 0.0118 0.0422 0.0140 0.0607 0.0163 0.0840 0.0189 0.1223 0.022402322049 211 0.0224 0.0115 0.0272 0.0116 0.0385 0.0130 0.0672 0.0156 0.1008 0.0174 0.1452 0.0194 0.2009 0.0218 0.2926 0.025002322500 212 0.0012 0.0012 0.0014 0.0013 0.0019 0.0017 0.0032 0.0027 0.0047 0.0038 0.0067 0.0052 0.0093 0.0067 0.0136 0.009102324000 213 0.0023 0.0021 0.0025 0.0022 0.0033 0.0028 0.0055 0.0043 0.0082 0.0059 0.0118 0.0077 0.0164 0.0098 0.0239 0.012802324400 214 0.0032 0.0028 0.0042 0.0034 0.0062 0.0047 0.0114 0.0073 0.0174 0.0095 0.0253 0.0119 0.0352 0.0144 0.0516 0.017902324500 215 0.0031 0.0028 0.0043 0.0035 0.0067 0.0050 0.0128 0.0078 0.0200 0.0102 0.0295 0.0127 0.0414 0.0154 0.0611 0.018902325000 216 0.0028 0.0025 0.0028 0.0024 0.0035 0.0030 0.0057 0.0044 0.0085 0.0060 0.0123 0.0079 0.0172 0.0101 0.0253 0.0132
Appendix 2 63

USGS 

station 

no.

Map 

no.

(pl. 1)

50% 

chance 

exceedance

50% 

chance 

exceedance

20% 

chance 

exceedance

20% 

chance 

exceedance

10% 

chance 

exceedance

10% 

chance 

exceedance

4% 

chance 

exceedance

4% 

chance 

exceedance

2% 

chance 

exceedance

2% 

chance 

exceedance

1% 

chance 

exceedance

1% 

chance 

exceedance

0.5% 

chance 

exceedance

0.5% 

chance 

exceedance

0.2% 

chance 

exceedance

0.2% 

chance 

exceedance

G W G W G W G W G W G W G W G W

02326000 217 0.0029 0.0026 0.0024 0.0022 0.0027 0.0024 0.0046 0.0038 0.0073 0.0054 0.0111 0.0074 0.0159 0.0096 0.0239 0.012802326250 218 0.0047 0.0039 0.0049 0.0040 0.0063 0.0048 0.0104 0.0069 0.0155 0.0089 0.0224 0.0112 0.0311 0.0137 0.0455 0.017102326261 219 0.0163 0.0097 0.0200 0.0101 0.0286 0.0116 0.0504 0.0145 0.0758 0.0164 0.1094 0.0186 0.1515 0.0211 0.2207 0.024402326300 220 0.0086 0.0063 0.0111 0.0072 0.0164 0.0089 0.0298 0.0121 0.0454 0.0143 0.0660 0.0167 0.0917 0.0193 0.1341 0.022702326372 221 0.0040 0.0035 0.0037 0.0031 0.0044 0.0036 0.0072 0.0053 0.0110 0.0072 0.0162 0.0094 0.0230 0.0118 0.0341 0.015202326500 222 0.0080 0.0060 0.0070 0.0052 0.0080 0.0057 0.0134 0.0080 0.0207 0.0104 0.0310 0.0130 0.0443 0.0158 0.0661 0.019402326512 223 0.0028 0.0025 0.0040 0.0034 0.0064 0.0048 0.0126 0.0078 0.0198 0.0102 0.0295 0.0127 0.0417 0.0154 0.0619 0.019002326574 224 0.0150 0.0092 0.0181 0.0096 0.0256 0.0111 0.0445 0.0139 0.0667 0.0159 0.0961 0.0181 0.1330 0.0207 0.1936 0.024002326595 225 0.0119 0.0079 0.0133 0.0080 0.0177 0.0093 0.0297 0.0120 0.0440 0.0142 0.0633 0.0165 0.0876 0.0191 0.1276 0.022502326598 226 0.0136 0.0087 0.0164 0.0091 0.0232 0.0106 0.0403 0.0135 0.0604 0.0156 0.0870 0.0178 0.1204 0.0203 0.1754 0.023702326838 227 0.0126 0.0082 0.0176 0.0094 0.0279 0.0115 0.0540 0.0147 0.0846 0.0168 0.1254 0.0190 0.1768 0.0215 0.2618 0.024802326900 228 0.0011 0.0011 0.0012 0.0011 0.0016 0.0014 0.0026 0.0023 0.0038 0.0032 0.0056 0.0044 0.0077 0.0059 0.0113 0.0080

Region 3

02234100 28 0.0083 0.0070 0.0070 0.0055 0.0079 0.0058 0.0133 0.0080 0.0209 0.0103 0.0315 0.0126 0.0452 0.0149 0.0676 0.018002234500 29 0.0041 0.0037 0.0041 0.0035 0.0051 0.0041 0.0083 0.0059 0.0124 0.0077 0.0180 0.0097 0.0251 0.0118 0.0370 0.014702235000 30 0.0004 0.0004 0.0005 0.0005 0.0007 0.0007 0.0012 0.0012 0.0018 0.0017 0.0027 0.0024 0.0037 0.0032 0.0054 0.004402235200 31 0.0011 0.0011 0.0014 0.0014 0.0021 0.0019 0.0038 0.0032 0.0050 0.0040 0.0084 0.0060 0.0117 0.0077 0.0171 0.010502236000 32 0.0006 0.0006 0.0006 0.0006 0.0008 0.0008 0.0013 0.0012 0.0019 0.0018 0.0028 0.0024 0.0039 0.0033 0.0056 0.004602236120 33 0.0050 0.0045 0.0062 0.0051 0.0091 0.0065 0.0162 0.0090 0.0245 0.0111 0.0355 0.0132 0.0492 0.0154 0.0718 0.018202236125 34 0.0012 0.0012 0.0012 0.0012 0.0015 0.0014 0.0024 0.0022 0.0037 0.0031 0.0054 0.0043 0.0075 0.0056 0.0111 0.007602236350 35 0.0059 0.0052 0.0055 0.0045 0.0065 0.0050 0.0107 0.0070 0.0162 0.0090 0.0239 0.0112 0.0338 0.0134 0.0501 0.016402236500 36 0.0061 0.0054 0.0048 0.0041 0.0054 0.0044 0.0094 0.0064 0.0150 0.0086 0.0230 0.0110 0.0332 0.0134 0.0498 0.016402236700 37 0.0114 0.0091 0.0096 0.0071 0.0110 0.0074 0.0185 0.0097 0.0289 0.0119 0.0435 0.0141 0.0622 0.0164 0.0931 0.019402237000 38 0.0162 0.0120 0.0147 0.0095 0.0174 0.0098 0.0286 0.0119 0.0437 0.0138 0.0646 0.0158 0.0914 0.0180 0.1358 0.020702239000 39 0.0014 0.0014 0.0014 0.0013 0.0017 0.0016 0.0027 0.0024 0.0041 0.0034 0.0060 0.0046 0.0084 0.0061 0.0123 0.082002240000 40 0.0007 0.0007 0.0007 0.0007 0.0008 0.0008 0.0014 0.0013 0.0021 0.0019 0.0030 0.0026 0.0042 0.0036 0.0062 0.005002240500 41 0.0014 0.0014 0.0015 0.0014 0.0019 0.0017 0.0031 0.0027 0.0046 0.0038 0.0067 0.0051 0.0093 0.0066 0.0136 0.008802240902 42 0.0134 0.0104 0.0114 0.0080 0.0131 0.0082 0.0219 0.0105 0.0342 0.0127 0.0514 0.0149 0.0735 0.0171 0.1099 0.0200022409424 43 0.0547 0.0250 0.0556 0.0180 0.0699 0.0169 0.1146 0.0172 0.1707 0.0181 0.2472 0.1932 0.3447 0.0210 0.5060 0.023302240950 44 0.0039 0.0036 0.0051 0.0043 0.0076 0.0057 0.0139 0.0082 0.0212 0.0104 0.0308 0.0125 0.0429 0.0147 0.0628 0.017602240954 45 0.0033 0.0031 0.0035 0.0031 0.0046 0.0038 0.0076 0.0055 0.0113 0.0072 0.0162 0.0091 0.0225 0.0112 0.0329 0.0140

Appendix 2. Variance of prediction values for gaging stations used in Florida regional regression analyses.—Continued[USGS, U.S. Geological Survey; no., number; pl., plate; %, percent; G, computed from the Bulletin 17B analysis of the gaging station; W, weighted using equation]
64 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 2. Variance of prediction values for gaging stations used in Florida regional regression analyses.—Continued [USGS, U.S. Geological Survey; no., number; pl., plate; %, percent; G, computed from the Bulletin 17B analysis of the gaging station; W, weighted using equation] USGS station no. Map no. (pl. 1) 50% chance exceed- ance 50% chance exceed- ance 20% chance exceed- ance 20% chance ex- ceed- ance 10% chance exceed- ance 10% chance exceed- ance 4% chance exceed- ance 4% chance exceed- ance 2% chance exceed- ance 2% chance exceed- ance 1% chance exceed- ance 1% chance exceed- ance 0.5% chance exceed- ance 0.5% chance exceed- ance 0.2% chance ex- ceed- ance 0.2% chance exceed- ance G W G W G W G W G W G W G W G W 02241900 46 0.0056 0.0050 0.0062 0.0050 0.0083 0.0060 0.0139 0.0082 0.0207 0.0102 0.0297 0.0123 0.0411 0.0145 0.0599 0.0174 02242451 47 0.0869 0.0302 0.0672 0.0191 0.0745 0.0172 0.1307 0.0176 0.2114 0.0185 0.3249 0.0197 0.4697 0.0213 0.7057 0.0236 02243000 48 0.0030 0.0028 0.0030 0.0027 0.0037 0.0032 0.0060 0.0046 0.0090 0.0062 0.0131 0.0080 0.0182 0.0100 0.0268 0.0128 02243500 49 0.0016 0.0016 0.0021 0.0020 0.0032 0.0028 0.0058 0.0045 0.0088 0.0062 0.0128 0.0080 0.0179 0.0099 0.0262 0.0126 02243530 50 0.0048 0.0043 0.0042 0.0037 0.0050 0.0041 0.0082 0.0058 0.0126 0.0078 0.0188 0.0102 0.0267 0.0122 0.0398 0.0152 02244000 51 0.0026 0.0025 0.0023 0.0021 0.0026 0.0023 0.0044 0.0036 0.0067 0.0051 0.0101 0.0068 0.0144 0.0088 0.0215 0.0114 02262900 87 0.0024 0.0023 0.0028 0.0025 0.0037 0.0032 0.0063 0.0048 0.0094 0.0064 0.0134 0.0082 0.0186 0.0101 0.0271 0.0128 02263800 88 0.0021 0.0020 0.0023 0.0022 0.0031 0.0027 0.0052 0.0042 0.0077 0.0056 0.0111 0.0073 0.0154 0.0091 0.0225 0.0117 02264000 89 0.0062 0.0054 0.0047 0.0040 0.0052 0.0042 0.0092 0.0063 0.0149 0.0086 0.0230 0.0110 0.0332 0.0134 0.0500 0.0164 02264051 90 0.0008 0.0008 0.0012 0.0011 0.0018 0.0017 0.0036 0.0030 0.0056 0.0044 0.0082 0.0059 0.0116 0.0076 0.0172 0.0101 02264100 91 0.0022 0.0021 0.0020 0.0018 0.0023 0.0021 0.0038 0.0032 0.0058 0.0045 0.0087 0.0061 0.0123 0.0079 0.0184 0.0105 02264495 92 0.0010 0.0010 0.0011 0.0011 0.0015 0.0014 0.0026 0.0023 0.0038 0.0032 0.0054 0.0043 0.0075 0.0056 0.0110 0.0076 02266200 93 0.0046 0.0042 0.0039 0.0034 0.0044 0.0037 0.0074 0.0054 0.0117 0.0074 0.0176 0.0096 0.0252 0.0118 0.0379 0.0148 02266300 94 0.0023 0.0022 0.0029 0.0026 0.0042 0.0036 0.0076 0.0055 0.0115 0.0073 0.0166 0.0093 0.0231 0.0114 0.0337 0.0142 02266480 95 0.0025 0.0024 0.0029 0.0026 0.0040 0.0034 0.0068 0.0051 0.0102 0.0068 0.0146 0.0086 0.0202 0.0106 0.0294 0.0134

02269000 96 0.0034 0.0032 0.0038 0.0033 0.0049 0.0040 0.0082 0.0059 0.0122 0.0076 0.0176 0.0096 0.0244 0.0116 0.0356 0.014502269520 97 0.0038 0.0035 0.0045 0.0038 0.0063 0.0049 0.0109 0.0071 0.0164 0.0090 0.0236 0.0111 0.0326 0.0132 0.0474 0.016102269720 98 0.0026 0.0025 0.0020 0.0019 0.0023 0.0021 0.0040 0.0033 0.0064 0.0049 0.0098 0.0067 0.0142 0.0087 0.0214 0.011402270500 99 0.0016 0.0015 0.0020 0.0018 0.0028 0.0025 0.0048 0.0039 0.0073 0.0054 0.0105 0.0070 0.0145 0.0088 0.0212 0.011302271500 100 0.0021 0.0020 0.0021 0.0020 0.0027 0.0024 0.0044 0.0036 0.0066 0.0050 0.0095 0.0065 0.0132 0.0083 0.0194 0.010802272000 101 0.0033 0.0030 0.0025 0.0023 0.0028 0.0025 0.0049 0.0039 0.0079 0.0057 0.0122 0.0077 0.0177 0.0099 0.0266 0.012702293694 106 0.0091 0.0076 0.0082 0.0063 0.0096 0.0067 0.0159 0.0089 0.0243 0.0110 0.0360 0.0132 0.0511 0.0155 0.0761 0.018502293986 107 0.0043 0.0039 0.0056 0.0046 0.0085 0.0061 0.0156 0.0088 0.0239 0.0110 0.0349 0.0131 0.0487 0.0153 0.0713 0.018202293987 108 0.0028 0.0027 0.0030 0.0027 0.0038 0.0032 0.0062 0.0048 0.0092 0.0064 0.0013 0.0082 0.0186 0.0101 0.0272 0.012902294068 109 0.0080 0.0068 0.0080 0.0062 0.0100 0.0069 0.0164 0.0091 0.0244 0.0111 0.0355 0.0132 0.0495 0.0154 0.0728 0.018302294650 110 0.0015 0.0015 0.0018 0.0017 0.0026 0.0023 0.0046 0.0037 0.0068 0.0051 0.0098 0.0067 0.0136 0.0084 0.0198 0.010902294898 111 0.0022 0.0021 0.0026 0.0024 0.0035 0.0030 0.0060 0.0046 0.0090 0.0062 0.0129 0.0080 0.0178 0.0099 0.0259 0.012602295013 112 0.0028 0.0026 0.0030 0.0027 0.0040 0.0034 0.0067 0.0050 0.0099 0.0067 0.0143 0.0085 0.0198 0.0105 0.0288 0.013202301900 153 0.0046 0.0042 0.0056 0.0046 0.0079 0.0058 0.0138 0.0082 0.0410 0.0136 0.0297 0.0123 0.0411 0.0145 0.0599 0.017402301990 154 0.0110 0.0089 0.0118 0.0082 0.0154 0.0091 0.0256 0.0113 0.0379 0.0132 0.0546 0.0151 0.0757 0.0172 0.1106 0.020002302260 155 0.0008 0.0008 0.0008 0.0008 0.0011 0.0011 0.0019 0.0017 0.0028 0.0025 0.0041 0.0034 0.0056 0.0045 0.0082 0.0062
Appendix 2 65

USGS 

station 

no.

Map 

no.

(pl. 1)

50% 

chance 

exceedance

50% 

chance 

exceedance

20% 

chance 

exceedance

20% 

chance 

exceedance

10% 

chance 

exceedance

10% 

chance 

exceedance

4% 

chance 

exceedance

4% 

chance 

exceedance

2% 

chance 

exceedance

2% 

chance 

exceedance

1% 

chance 

exceedance

1% 

chance 

exceedance

0.5% 

chance 

exceedance

0.5% 

chance 

exceedance

0.2% 

chance 

exceedance

0.2% 

chance 

exceedance

G W G W G W G W G W G W G W G W

02302500 156 0.0012 0.0012 0.0017 0.0016 0.0027 0.0024 0.0051 0.0041 0.0079 0.0057 0.0116 0.0075 0.0163 0.0094 0.0241 0.012102303000 157 0.0017 0.0016 0.0020 0.0019 0.0029 0.0026 0.0050 0.0040 0.0076 0.0055 0.0109 0.0072 0.0151 0.0090 0.0220 0.011602303205 158 0.0070 0.0061 0.0085 0.0064 0.0121 0.0078 0.0211 0.0103 0.0316 0.0124 0.0456 0.0144 0.0631 0.0165 0.0919 0.019302303350 159 0.0065 0.0057 0.0064 0.0051 0.0079 0.0058 0.0129 0.0089 0.0193 0.0099 0.0280 0.0120 0.0393 0.0142 0.0578 0.017202303358 160 0.0284 0.0176 0.0238 0.0126 0.0272 0.0123 0.0457 0.0140 0.0715 0.0158 0.1079 0.0175 0.1544 0.0195 0.2312 0.022102303400 161 0.0083 0.0070 0.0081 0.0062 0.0099 0.0068 0.0162 0.0090 0.0242 0.0110 0.0354 0.0132 0.0496 0.0154 0.0733 0.018302303420 162 0.0048 0.0044 0.0049 0.0041 0.0061 0.0048 0.0100 0.0067 0.0149 0.0086 0.0216 0.0106 0.0301 0.0128 0.0442 0.015802303800 163 0.0047 0.0043 0.0042 0.0036 0.0049 0.0040 0.0081 0.0058 0.0124 0.0077 0.0185 0.0098 0.0263 0.0121 0.0392 0.015102306289 164 0.0350 0.0199 0.0336 0.0148 0.0408 0.0144 0.0667 0.0156 0.1004 0.0169 0.1469 0.0183 0.2064 0.0202 0.3050 0.022602307200 165 0.0053 0.0048 0.0068 0.0054 0.0101 0.0069 0.0182 0.0096 0.0277 0.0117 0.0402 0.0138 0.0559 0.0160 0.0817 0.018802309848 166 0.0059 0.0052 0.0057 0.0047 0.0069 0.0053 0.0113 0.0072 0.0170 0.0092 0.0248 0.0114 0.0349 0.0136 0.0516 0.016602309980 167 0.0102 0.0084 0.0126 0.0086 0.0182 0.0100 0.0321 0.0124 0.0484 0.0143 0.0699 0.0161 0.0968 0.0182 0.1412 0.020802310000 168 0.0026 0.0024 0.0030 0.0027 0.0041 0.0034 0.0070 0.0052 0.0104 0.0069 0.0149 0.0087 0.0206 0.0107 0.0300 0.013502310147 169 0.0031 0.0029 0.0040 0.0034 0.0059 0.0046 0.0107 0.0070 0.0162 0.0090 0.0236 0.0111 0.0328 0.0133 0.0479 0.016202310240 170 0.0220 0.0149 0.0190 0.0111 0.0219 0.0110 0.0364 0.0130 0.0565 0.0149 0.0847 0.0168 0.1209 0.0189 0.1806 0.021502310300 171 0.0040 0.0037 0.0049 0.0042 0.0070 0.0053 0.0122 0.0076 0.0184 0.0096 0.0265 0.0117 0.0366 0.0139 0.0534 0.016802310800 172 0.0084 0.0071 0.0084 0.0064 0.0106 0.0718 0.0173 0.0093 0.0258 0.0114 0.0375 0.0134 0.0523 0.0156 0.0769 0.018602310947 173 0.0037 0.0034 0.0029 0.0026 0.0032 0.0028 0.0056 0.0044 0.0090 0.0062 0.0137 0.0083 0.0198 0.0105 0.0297 0.013402311500 174 0.0069 0.0060 0.0070 0.0055 0.0088 0.0063 0.0144 0.0084 0.0215 0.0104 0.0311 0.0125 0.0434 0.0148 0.0637 0.017702312000 175 0.0020 0.0020 0.0020 0.0019 0.0026 0.0023 0.0042 0.0035 0.0063 0.0048 0.0091 0.0063 0.0127 0.0081 0.0186 0.010602312180 176 0.0107 0.0087 0.0077 0.0060 0.0084 0.0061 0.0154 0.0088 0.0257 0.0113 0.0400 0.0138 0.0582 0.0161 0.0874 0.019102312200 177 0.0058 0.0052 0.0051 0.0043 0.0060 0.0047 0.0099 0.0066 0.0152 0.0087 0.0227 0.0109 0.0323 0.0132 0.0481 0.016202312500 178 0.0024 0.0023 0.0022 0.0021 0.0027 0.0024 0.0044 0.0036 0.0067 0.0050 0.0098 0.0067 0.0139 0.0086 0.0206 0.011202312600 179 0.0116 0.0093 0.0102 0.0074 0.0119 0.0078 0.0196 0.0100 0.0303 0.0121 0.0451 0.0143 0.0642 0.0166 0.0958 0.019502312667 180 0.0035 0.0032 0.0036 0.0032 0.0046 0.0038 0.0076 0.0055 0.0113 0.0072 0.0163 0.0092 0.0226 0.0112 0.0332 0.014102312720 181 0.0030 0.0028 0.0028 0.0025 0.0033 0.0029 0.0055 0.0043 0.0083 0.0059 0.0122 0.0077 0.0172 0.0097 0.0255 0.012502313000 182 0.0013 0.0013 0.0014 0.0014 0.0019 0.0018 0.0032 0.0028 0.0048 0.0038 0.0068 0.0052 0.0095 0.0066 0.0138 0.0088

Region 4

02231342 11 0.0026 0.0021 0.0022 0.0019 0.0026 0.0022 0.0043 0.0034 0.0067 0.0050 0.0101 0.0070 0.0144 0.0093 0.0215 0.012802231396 12 0.0044 0.0030 0.0050 0.0035 0.0069 0.0046 0.0117 0.0069 0.0174 0.0094 0.0250 0.0120 0.0346 0.0150 0.0503 0.019502231458 13 0.0212 0.0068 0.0191 0.0072 0.0225 0.0086 0.0370 0.0116 0.0566 0.0149 0.0838 0.0181 0.1189 0.0218 0.1768 0.0270

Appendix 2. Variance of prediction values for gaging stations used in Florida regional regression analyses.—Continued[USGS, U.S. Geological Survey; no., number; pl., plate; %, percent; G, computed from the Bulletin 17B analysis of the gaging station; W, weighted using equation]
66 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 2. Variance of prediction values for gaging stations used in Florida regional regression analyses.—Continued [USGS, U.S. Geological Survey; no., number; pl., plate; %, percent; G, computed from the Bulletin 17B analysis of the gaging station; W, weighted using equation] USGS station no. Map no. (pl. 1) 50% chance exceed- ance 50% chance exceed- ance 20% chance exceed- ance 20% chance ex- ceed- ance 10% chance exceed- ance 10% chance exceed- ance 4% chance ex- ceed- ance 4% chance exceed- ance 2% chance exceed- ance 2% chance exceed- ance 1% chance exceed- ance 1% chance exceed- ance 0.5% chance exceed- ance 0.5% chance exceed- ance 0.2% chance ex- ceed- ance 0.2% chance exceed- ance G W G W G W G W G W G W G W G W 02231565 14 0.0074 0.0042 0.0090 0.0051 0.0129 0.0067 0.0227 0.0097 0.0340 0.0127 0.0492 0.0157 0.0682 0.0192 0.0993 0.0241 02231600 15 0.0029 0.0023 0.0037 0.0028 0.0053 0.0038 0.0094 0.0061 0.0142 0.0084 0.0206 0.0109 0.0286 0.0138 0.0416 0.0181 02232000 16 0.0026 0.0020 0.0027 0.0022 0.0034 0.0027 0.0056 0.0042 0.0083 0.0059 0.0120 0.0079 0.0167 0.0103 0.0244 0.0138 02232155 17 0.0078 0.0044 0.0100 0.0054 0.0147 0.0072 0.0266 0.0104 0.0404 0.0135 0.0586 0.0165 0.0814 0.0201 0.1190 0.0252 02232200 18 0.0026 0.0021 0.0032 0.0025 0.0047 0.0035 0.0083 0.0056 0.0125 0.0077 0.0181 0.0101 0.0251 0.0129 0.0365 0.0170 02232400 19 0.0029 0.0022 0.0020 0.0017 0.0022 0.0019 0.0042 0.0034 0.0070 0.0052 0.0110 0.0074 0.0160 0.0100 0.0240 0.0137 02232450 20 0.0040 0.0028 0.0055 0.0038 0.0087 0.0054 0.0168 0.0084 0.0263 0.0114 0.0389 0.0145 0.0548 0.0179 0.0811 0.0229 02232500 21 0.0013 0.0012 0.0011 0.0010 0.0012 0.0011 0.0020 0.0018 0.0032 0.0028 0.0049 0.0040 0.0071 0.0056 0.0106 0.0080 02233001 22 0.0048 0.0033 0.0036 0.0028 0.0040 0.0031 0.0071 0.0050 0.0137 0.0082 0.0181 0.0101 0.0263 0.0132 0.0395 0.0176 02233102 23 0.0092 0.0048 0.0116 0.0058 0.0170 0.0076 0.0305 0.0109 0.0462 0.0141 0.0670 0.0171 0.0930 0.0207 0.1358 0.0258 02233200 24 0.0029 0.0023 0.0025 0.0021 0.0029 0.0024 0.0049 0.0038 0.0076 0.0055 0.0113 0.0076 0.0161 0.0100 0.0241 0.0137 02233475 25 0.0040 0.0029 0.0043 0.0031 0.0056 0.0040 0.0092 0.0060 0.0137 0.0082 0.0197 0.0106 0.0274 0.0135 0.0400 0.0177 02233500 26 0.0014 0.0012 0.0016 0.0014 0.0021 0.0018 0.0035 0.0029 0.0052 0.0041 0.0075 0.0056 0.0103 0.0074 0.0151 0.0102 02234000 27 0.0013 0.0012 0.0014 0.0012 0.0017 0.0015 0.0028 0.0024 0.0042 0.0035 0.0061 0.0048 0.0085 0.0064 0.0124 0.0089 02249007 79 0.0056 0.0036 0.0076 0.0046 0.0117 0.0064 0.0222 0.0096 0.0343 0.0127 0.0504 0.0158 0.0707 0.0194 0.1041 0.0244

02249500 80 0.0064 0.0039 0.0061 0.0040 0.0074 0.0048 0.0121 0.0070 0.0182 0.0096 0.0266 0.0124 0.0374 0.0156 0.0554 0.020202249518 81 0.0028 0.0022 0.0038 0.0028 0.0059 0.0041 0.0111 0.0067 0.0173 0.0093 0.0254 0.0121 0.0357 0.0152 0.0526 0.019802250000 82 0.0056 0.0036 0.0056 0.0038 0.0069 0.0046 0.0112 0.0068 0.0168 0.0092 0.0244 0.0119 0.0342 0.0150 0.0504 0.019502251000 83 0.0016 0.0014 0.0018 0.0015 0.0023 0.0020 0.0039 0.0032 0.0058 0.0045 0.0083 0.0061 0.0115 0.0080 0.0167 0.011002251500 84 0.0091 0.0048 0.0099 0.0053 0.0129 0.0067 0.0215 0.0095 0.0319 0.0124 0.0459 0.0153 0.0636 0.0188 0.0929 0.023702256000 85 0.0127 0.0056 0.0125 0.0060 0.0155 0.0073 0.0253 0.0102 0.0379 0.0132 0.0551 0.0162 0.0771 0.0198 0.1136 0.024902256500 86 0.0019 0.0016 0.0021 0.0018 0.0028 0.0023 0.0046 0.0036 0.0069 0.0051 0.0099 0.0069 0.0137 0.0090 0.0200 0.012302273000 102 0.0050 0.0033 0.0048 0.0034 0.0057 0.0040 0.0094 0.0060 0.0141 0.0083 0.0208 0.0109 0.0292 0.0139 0.0432 0.018402293000 103 0.0136 0.0058 0.0180 0.0070 0.0272 0.0092 0.0503 0.0127 0.0771 0.0160 0.1126 0.0191 0.0157 0.0228 0.2304 0.028002293050 104 0.0050 0.0033 0.0066 0.0042 0.0100 0.0058 0.0186 0.0089 0.0285 0.0118 0.0416 0.0148 0.0581 0.0183 0.0852 0.023202293400 105 0.0065 0.0039 0.0090 0.0051 0.0143 0.0070 0.0278 0.0105 0.0435 0.0138 0.0645 0.0170 0.0909 0.0206 0.1354 0.025802295420 113 0.0045 0.0031 0.0053 0.0036 0.0073 0.0048 0.0126 0.0072 0.0188 0.0098 0.0271 0.0124 0.0375 0.0156 0.0546 0.020102295630 114 0.0025 0.0020 0.0028 0.0023 0.0038 0.0030 0.0064 0.0047 0.0096 0.0065 0.0137 0.0086 0.0190 0.0111 0.0277 0.014802295637 115 0.0013 0.0011 0.0018 0.0015 0.0028 0.0023 0.0053 0.0040 0.0082 0.0059 0.0122 0.0080 0.0171 0.0104 0.0252 0.014102296260 116 0.0078 0.0044 0.0090 0.0051 0.0124 0.0065 0.0211 0.0094 0.0315 0.0123 0.0453 0.0153 0.0627 0.0187 0.0912 0.023602296500 117 0.0016 0.0014 0.0022 0.0018 0.0034 0.0027 0.0065 0.0047 0.0101 0.0067 0.0149 0.0090 0.0209 0.0117 0.0308 0.0157
Appendix 2 67

USGS 

station 

no.

Map 

no.

(pl. 1)

50% 

chance 

exceedance

50% 

chance 

exceedance

20% 

chance 

exceedance

20% 

chance 

exceedance

10% 

chance 

exceedance

10% 

chance 

exceedance

4% 

chance 

exceedance

4% 

chance 

exceedance

2% 

chance 

exceedance

2% 

chance 

exceedance

1% 

chance 

exceedance

1% 

chance 

exceedance

0.5% 

chance 

exceedance

0.5% 

chance 

exceedance

0.2% 

chance 

exceedance

0.2% 

chance 

exceedance

G W G W G W G W G W G W G W G W

02296750 118 0.0013 0.0011 0.0018 0.0015 0.0028 0.0023 0.0054 0.0041 0.0085 0.0060 0.0126 0.0081 0.0177 0.0106 0.0263 0.014402297088 119 0.0029 0.0023 0.0034 0.0026 0.0046 0.0035 0.0079 0.0054 0.0117 0.0074 0.0169 0.0097 0.0233 0.0124 0.0340 0.016402297100 120 0.0018 0.0015 0.0023 0.0019 0.0035 0.0028 0.0065 0.0047 0.0100 0.0067 0.0145 0.0089 0.0202 0.0115 0.0297 0.015402297155 121 0.0041 0.0029 0.0053 0.0036 0.0079 0.0050 0.0145 0.0078 0.0221 0.0106 0.0322 0.0134 0.0448 0.0167 0.0656 0.021502297251 122 0.0123 0.0055 0.0132 0.0062 0.0170 0.0076 0.0282 0.0106 0.0419 0.0137 0.0604 0.0167 0.0837 0.0202 0.1224 0.025302297310 123 0.0025 0.0020 0.0029 0.0023 0.0040 0.0031 0.0067 0.0048 0.0100 0.0067 0.0144 0.0089 0.0200 0.0114 0.0291 0.015202297320 124 0.0065 0.0039 0.0081 0.0048 0.0116 0.0063 0.0206 0.0093 0.0310 0.0122 0.0460 0.0153 0.0620 0.0186 0.0904 0.023602298123 125 0.0018 0.0015 0.0021 0.0018 0.0030 0.0024 0.0052 0.0040 0.0077 0.0056 0.0111 0.0075 0.0154 0.0097 0.0224 0.013202298202 126 0.0023 0.0018 0.0024 0.0020 0.0031 0.0025 0.0051 0.0039 0.0145 0.0084 0.0110 0.0074 0.0152 0.0097 0.0223 0.013102298608 127 0.0039 0.0028 0.0054 0.0037 0.0087 0.0054 0.0171 0.0085 0.0269 0.0116 0.0400 0.0146 0.0566 0.0181 0.0839 0.023102298760 128 0.0151 0.0060 0.0164 0.0068 0.0214 0.0084 0.0357 0.0115 0.0529 0.0146 0.0761 0.0177 0.1055 0.0213 0.1539 0.026402298830 129 0.0016 0.0014 0.0021 0.0018 0.0031 0.0026 0.0058 0.0043 0.0089 0.0062 0.0130 0.0083 0.0182 0.0108 0.0267 0.014502298928 130 0.0247 0.0071 0.0263 0.0080 0.0341 0.0099 0.0564 0.0130 0.0837 0.0163 0.1206 0.0193 0.1674 0.0230 0.2447 0.028202299120 131 0.0043 0.0030 0.0050 0.0035 0.0068 0.0046 0.0115 0.0069 0.0172 0.0093 0.0247 0.0119 0.0341 0.0150 0.0497 0.019402299160 132 0.0170 0.0063 0.0176 0.0070 0.0222 0.0086 0.0366 0.0116 0.0544 0.0148 0.0787 0.0178 0.1095 0.0214 0.1605 0.026602299410 133 0.0076 0.0043 0.0099 0.0053 0.0147 0.0071 0.0268 0.0104 0.0408 0.0135 0.0593 0.0166 0.0825 0.0201 0.1207 0.025202299800 134 0.0033 0.0025 0.0106 0.0055 0.0170 0.0076 0.0334 0.0113 0.0527 0.0146 0.0784 0.0178 0.1108 0.0215 0.1646 0.026702299950 135 0.0025 0.0020 0.0031 0.0025 0.0045 0.0034 0.0080 0.0054 0.0120 0.0075 0.0174 0.0099 0.0240 0.0126 0.0350 0.016702300000 136 0.0046 0.0031 0.0052 0.0036 0.0070 0.0046 0.0118 0.0070 0.0175 0.0094 0.0251 0.0120 0.0347 0.0151 0.0506 0.019602300018 137 0.0190 0.0065 0.0249 0.0079 0.0374 0.0101 0.0688 0.0136 0.1052 0.0170 0.1534 0.0200 0.2138 0.0237 0.3132 0.028902300032 138 0.0043 0.0030 0.0050 0.0035 0.0070 0.0046 0.0119 0.0070 0.0178 0.0095 0.0256 0.0121 0.0354 0.0152 0.0516 0.019702300034 139 0.0057 0.0036 0.0055 0.0037 0.0067 0.0045 0.0109 0.0066 0.0164 0.0091 0.0240 0.0117 0.0336 0.0149 0.0497 0.0194023000355 140 0.0044 0.0031 0.0045 0.0032 0.0057 0.0040 0.0094 0.0060 0.0140 0.0083 0.0202 0.0108 0.0282 0.0137 0.0414 0.018002300037 141 0.0061 0.0038 0.0073 0.0045 0.0103 0.0059 0.0180 0.0087 0.0269 0.0116 0.0388 0.0144 0.0536 0.0178 0.0781 0.022602300038 142 0.0115 0.0053 0.0141 0.0064 0.0202 0.0082 0.0357 0.0115 0.0536 0.0147 0.0774 0.0178 0.1072 0.0213 0.1562 0.026502300039 143 0.0159 0.0061 0.0155 0.0066 0.0191 0.0080 0.0312 0.0110 0.0467 0.0141 0.0681 0.0172 0.0954 0.0208 0.1407 0.026002300100 144 0.0019 0.0016 0.0025 0.0021 0.0038 0.0030 0.0072 0.0050 0.0110 0.0071 0.0161 0.0095 0.0224 0.0122 0.0329 0.016202300200 145 0.0027 0.0021 0.0025 0.0021 0.0031 0.0025 0.0050 0.0039 0.0076 0.0055 0.0111 0.0075 0.0156 0.0098 0.0231 0.013402300500 146 0.0020 0.0017 0.0026 0.0021 0.0038 0.0030 0.0068 0.0049 0.0104 0.0069 0.0150 0.0091 0.0209 0.0117 0.0305 0.015602300530 147 0.0058 0.0037 0.0077 0.0046 0.0116 0.0063 0.0216 0.0095 0.0330 0.0126 0.0482 0.0156 0.0673 0.0191 0.0987 0.024102300700 148 0.0030 0.0023 0.0039 0.0029 0.0057 0.0040 0.0102 0.0064 0.0154 0.0088 0.0223 0.0113 0.0310 0.0143 0.0452 0.0187

Appendix 2. Variance of prediction values for gaging stations used in Florida regional regression analyses.—Continued[USGS, U.S. Geological Survey; no., number; pl., plate; %, percent; G, computed from the Bulletin 17B analysis of the gaging station; W, weighted using equation]
68 Magnitude and Frequency of Floods for Rural Streams in Florida, 2006 Appendix 2. Variance of prediction values for gaging stations used in Florida regional regression analyses.—Continued [USGS, U.S. Geological Survey; no., number; pl., plate; %, percent; G, computed from the Bulletin 17B analysis of the gaging station; W, weighted using equation] USGS station no. Map no. (pl. 1) 50% chance exceed- ance 50% chance exceed- ance 20% chance exceed- ance 20% chance exceed- ance 10% chance ex- ceed- ance 10% chance exceed- ance 4% chance exceed- ance 4% chance exceed- ance 2% chance exceed- ance 2% chance exceed- ance 1% chance exceed- ance 1% chance exceed- ance 0.5% chance exceed- ance 0.5% chance exceed- ance 0.2% chance exceed- ance 0.2% chance exceed- ance

G W G W G W G W G W G W G W G W

02301000 149 0.0026 0.0021 0.0030 0.0024 0.0042 0.0032 0.0072 0.0051 0.0108 0.0070 0.0156 0.0093 0.0215 0.0119 0.0313 0.015802301300 150 0.0027 0.0021 0.0031 0.0024 0.0042 0.0032 0.0072 0.0051 0.0108 0.0070 0.0155 0.0093 0.0215 0.0119 0.0313 0.015802301350 151 0.0082 0.0045 0.0069 0.0043 0.0079 0.0050 0.0133 0.0074 0.0208 0.0103 0.0313 0.0133 0.0448 0.0167 0.0671 0.021602301500 152 0.0022 0.0018 0.0032 0.0025 0.0053 0.0038 0.0110 0.0066 0.0177 0.0094 0.0267 0.0124 0.0383 0.0157 0.0575 0.0205
Appendix 3 69

Station 

number

Station 

name

Drainage 

area

(mi2)

Storage

(percent)

Period of 

record

(years)

Peak flow, in cubic feet per second, for indicated exceedance probability in percent

50 20 10 4 2 1 0.5 0.2

02358000 Apalachicola River at Chattahoochee, Fla. 17,200 2.55 50 90,500 128,000 154,000 190,000 218,000 248,000 279,000 323,00002358700 Apalachicola River near Blountstown, Fla. 17,600 2.57 49 85,400 124,000 154,000 195,000 230,000 268,000 308,000 369,00002359170 Apalachicola River near Sumatra, Fla. 19,200 3.36 29 79,100 118,000 145,000 181,000 209,000 237,000 266,000 306,00002319500 Suwannee River at Ellaville, Fla. 6,970 14.64 79 18,600 32,300 42,900 57,900 70,200 83,300 97,400 118,00002320000 Suwannee River at Luraville, Fla. 7,280 15.21 25 20,500 36,700 49,400 67,200 81,800 97,400 114,000 138,00002320500 Suwannee River at Branford, Fla. 7,880 14.78 76 16,800 28,000 36,200 47,500 56,400 65,600 75,300 88,80002323000 Suwannee River near Bell, Fla. 9,390 13.93 33 16,500 27,400 36,500 50,700 63,200 77,700 94,400 120,00002323500 Suwannee River near Wilcox, Fla. 9,640 13.95 66 20,700 32,000 40,500 52,300 61,900 72,100 83,100 98,900

Appendix 3. Flood-frequency estimates using PeakFQ version 5.2.[mi2, square miles]
Manuscript approved on February 25, 2011, by Sandy C. Cooper

Publishing support provided by the 

Fort Lauderdale Publishing Service Center

For additional information, please contact

Richard Verdi, Hydrologist

U.S. Geological Survey

2639 North Monroe St., Suite A-200

Tallahassee, Fla. 32303

rverdi@usgs.gov

850-553-3676
R.J. Verdi and J.F. Dixon—Magnitude and Frequency of Floods for Rural Streams in Florida, 2006—Scientific Investigations Report 2011–5034

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