U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 02-4254

Prepared in cooperation with the

SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT

Extent of Areal Inundation of Riverine Wetlands Along

Cypress Creek and the Peace, Alafia, North Prong Alafia,

and South Prong Alafia Rivers, West-Central Florida
Cover photographs

Top— Downstream view of the Peace River from the gaging station near Bartow (02294655);

Polk County, Florida

Photograph by B.R. Lewelling, January 2003

Bottom— Downstream view of Cypress Creek from Old Ranch Road in section 9, township 27 

south, and range 19 east; Hillsborough County, Florida

Photograph by Dan Duerr, January 2003
Contents I

Extent of Areal Inundation of Riverine Wetlands 

Along Cypress Creek and the Peace, Alafia, 

North Prong Alafia, and South Prong Alafia 

Rivers, West-Central Florida

By B.R. Lewelling

U.S. Geological Survey

Water-Resources Investigations Report 02-4254

Prepared in cooperation with the

SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT

Tallahassee, Florida

2003
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

Use of trade, product, or firm names in this publication is for descriptive purposes only 

and does not imply endorsement by the U.S. Geological Survey.

For additional information 

write to: 

U.S. Geological Survey

2010 Levy Avenue

Tallahassee, FL 32310

Copies of this report can be 

purchased from:

U.S. Geological Survey

Branch of Information Services

Box 25286

Denver, CO 80225-0286

888-ASK-USGS

Additional information about water resources in Florida is available on the internet 

at http://fl.water.usgs.gov
Contents III

CONTENTS

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

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

Purpose and Scope ........................................................................................................................................................... 2

Previous Investigations..................................................................................................................................................... 2

Acknowledgments............................................................................................................................................................ 2

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

Methodology.............................................................................................................................................................................. 4

Cypress Creek ............................................................................................................................................................................ 6

Peace River ................................................................................................................................................................................ 9

Reach 1–Arcadia to Zolfo Springs................................................................................................................................. 12

Reach 2–Zolfo Springs to Fort Meade........................................................................................................................... 17

Reach 3–Fort Meade to Bartow ..................................................................................................................................... 21

Inundated Area and Effects of Potential Discharge Withdrawals Along the Three Peace River Reaches .................... 33

Alafia River System ................................................................................................................................................................. 33

Alafia River ................................................................................................................................................................... 33

North Prong Alafia River ............................................................................................................................................... 47

South Prong Alafia River ............................................................................................................................................... 50

Inundated Area and Effects of Potential Discharge Withdrawals Along the Alafia River System................................ 59

Summary.................................................................................................................................................................................. 60

Selected References ................................................................................................................................................................. 72

Appendices:.............................................................................................................................................................................. 73

A. Extent of inundation at Cypress Creek cross sections for selected percentile discharges ............................................ 74

B. Hydraulic depth at Cypress Creek cross sections for selected percentile discharges ................................................... 75

C. Acreage of areal inundation between adjacent Cypress Creek cross sections.............................................................. 76

D. Decrease of inundated acreage resulting from a potential 10-percent discharge withdrawal at Cypress Creek 

cross sections ................................................................................................................................................................ 77

E. Extent of inundation at cross sections along reach 1 of the Peace River for selected percentile discharges................ 78

F. Hydraulic depth at cross sections along reach 1 of the Peace River for selected percentile discharges....................... 79

G. Acreage of areal inundation between adjacent cross sections along reach 1 of the Peace River ................................. 80

H. Decrease of inundated acreage resulting from a potential 10-percent discharge withdrawal at cross sections 

along reach 1 of the Peace River................................................................................................................................... 81

I. Extent of inundation at cross sections along reach 2 of the Peace River for selected percentile discharges................ 82

J. Hydraulic depth at cross sections along reach 2 of the Peace River for selected percentile discharges....................... 83

K. Acreage of areal inundation between adjacent cross sections along reach 2 of the Peace River.................................. 84

L. Decrease of inundated acreage resulting from a potential 10-percent discharge withdrawal at cross sections 

along reach 2 of the Peace River................................................................................................................................... 85

M. Extent of inundation at cross sections along reach 3 of the Peace River for selected percentile discharges................ 86

N. Hydraulic depth at cross sections along reach 3 of the Peace River for selected percentile discharges....................... 86

O. Acreage of areal inundation between adjacent cross sections along reach 3 of the Peace River ................................. 87

P. Decrease of inundated acreage resulting from a potential 10-percent discharge withdrawal at cross sections 

along reach 3 of the Peace River................................................................................................................................... 87

Q. Extent of inundation at cross sections along the Alafia, North Prong Alafia, and South Prong Alafia Rivers for 

selected percentile discharges ....................................................................................................................................... 88

R. Hydraulic depth at cross sections along the Alafia, North Prong Alafia, and South Prong Alafia Rivers for 

selected percentile discharges ....................................................................................................................................... 89

S. Acreage of areal inundation between adjacent cross sections along the Alafia, North Prong Alafia, and South 

Prong Alafia Rivers for selected percentile discharges................................................................................................. 90

T. Decrease of inundated acreage resulting from a potential 10-percent discharge withdrawal at cross sections 

along the Alafia, North Prong Alafia, and South Prong Alafia Rivers for selected percentile discharges .................. 91
IV Contents

FIGURES

1. Map showing location of study area including Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, west-central Florida............................................................................................................3

2. Graph showing percentiles of daily mean discharge for the Peace River at Arcadia, Alafia River at Lithia, 

and Cypress Creek near Sulphur Springs gaging stations for selected periods..............................................................4

3. Diagram showing example cross section showing Manning’s n-values, subareas, and water-surface elevation ...........5

4. Map showing locations of Cypress Creek and the Sulphur Springs, Worthington Gardens, and San Antonio 

gaging stations and the study cross sections, west-central Florida.................................................................................6

5. Graph showing water-surface profiles along Cypress Creek for existing conditions and a potential 10-percent 

discharge withdrawal, from the mouth to SR 52 ............................................................................................................8

6. Diagram showing extent of areal inundation along the Cypress Creek channel and floodplain for selected 

percentile discharges.....................................................................................................................................................10

7-8. Graphs showing:

7. Estimated extent and frequency of areal inundation and hydraulic depth for Cypress Creek at selected cross 

sections for each of the selected percentile discharges...........................................................................................11

8. Estimated total inundated area along Cypress Creek for existing conditions and for a potential 10-percent 

discharge withdrawal, and percentage of inundated area decreased by a potential 10-percent discharge 

withdrawal for each of the selected percentile discharges......................................................................................13

9. Diagrams showing extent of areal inundation along Cypress Creek for the P50, P70, P80, P90, P98, P99.5, 

and P99.9 discharges for existing conditions and a potential 10-percent discharge withdrawal ............................. 14-17

10-11. Maps showing location of:

10. The Peace River, study reaches, and the Arcadia, Zolfo Springs, Fort Meade, and Bartow gaging stations, 

west-central Florida ................................................................................................................................................18

11. Reach 1 and channel cross sections along the Peace River from Arcadia to Zolfo Springs, west-central 

Florida.....................................................................................................................................................................21

12. Graph showing water-surface profiles along reach 1 of the Peace River for existing conditions and a potential 

10-percent discharge withdrawal..................................................................................................................................22

13. Diagram showing extent of areal inundation along reach 1 of the Peace River channel and floodplain for 

selected percentile discharges ......................................................................................................................................23

14-15. Graphs showing:

14. Estimated extent and frequency of areal inundation and hydraulic depth for Peace River cross sections along 

reaches 1, 2, and 3 for each of the selected percentile discharges..........................................................................24

15. Estimated total inundated area along reach 1 of the Peace River for existing conditions and for a potential 

10-percent discharge withdrawal, and percentage of inundated area decreased by a potential 10-percent 

discharge withdrawal for each of the selected percentile discharges .....................................................................25

16. Diagram showing extent of areal inundation along reach 1 of the Peace River channel and floodplain for 

the P10, P50, P70, P80, P90, P98, P99.5, and P99.9 discharges for existing conditions and a potential 10-percent 

discharge withdrawal.............................................................................................................................................. 26-29

17. Map showing location of reach 2 and cross sections along the Peace River from Zolfo Springs to Fort Meade, 

west-central Florida......................................................................................................................................................30

18. Graph showing water-surface profiles along reach 2 of the Peace River for existing conditions and a potential 

10-percent discharge withdrawal..................................................................................................................................31

19. Diagram showing areal inundation along reach 2 of the Peace River channel and floodplain for selected 

percentile discharges ....................................................................................................................................................32

20. Graph showing estimated total inundated area along reach 2 of the Peace River for existing conditions and for 

a potential 10-percent discharge withdrawal, and percentage of inundated area decreased by a potential 10-percent 

discharge withdrawal for each of the selected percentile discharges ...........................................................................33

21. Diagrams showing extent of areal inundation along reach 2 of the Peace River channel and floodplain for 

the P10, P50, P70, P80, P90, P98, P99.5, and P99.9 discharges for existing conditions and a potential 10-percent 

discharge withdrawal.............................................................................................................................................. 34-37

22. Map showing location of reach 3 and study cross sections along the Peace River from Fort Meade to Bartow, 

west-central Florida .....................................................................................................................................................38
Contents V

23. Graph showing water-surface profiles along reach 3 of the Peace River for existing conditions and a potential 

10-percent discharge withdrawal ................................................................................................................................. 39

24. Diagram showing extent of areal inundation along reach 3 of the Peace River channel and floodplain for selected 

percentile discharges.................................................................................................................................................... 40

25. Graph showing estimated total inundated area along reach 3 of the Peace River for existing conditions and for 

a potential 10-percent discharge withdrawal, and percentage of inundated area decreased by a potential 

10-percent discharge withdrawal for each of the selected percentile discharges ........................................................ 41

26. Diagrams showing extent of areal inundation along reach 3 of the Peace River channel and floodplain for 

the P10, P50, P70, P80, P90, P98, P99.5, and P99.9 discharges for existing conditions and a potential 10-percent 

discharge withdrawal ..............................................................................................................................................42-45

27. Graph showing estimated total inundated area along the three reaches of the Peace River for existing 

conditions and for a potential 10-percent discharge withdrawal, and percentage of inundated area decreased 

by a potential 10-percent discharge withdrawal for each of the selected percentile discharges.................................. 46

28. Map showing location of the Alafia, North Prong Alafia, and South Prong Alafia Rivers and cross sections, 

west-central Florida ..................................................................................................................................................... 47

29. Graph showing water-surface profiles along the Alafia River for existing conditions and a potential 10-percent discharge 

withdrawal, from the SR 640 bridge to the confluence with the North and South Prong Alafia Rivers..................... 49

30. Diagram showing extent of areal inundation along the Alafia River channel and floodplain for selected percentile 

discharges, from SR 640 to the confluence with the North and South Prong Alafia Rivers ...................................... 51

31-32. Graphs showing:

31. Estimated extent and frequency of areal inundation and hydraulic depth for Alafia, North Prong Alafia, 

and South Prong Alafia Rivers selected cross sections for each of the percentile discharges............................... 52

32. Estimated total inundated area along the Alafia River for existing conditions and for a potential 10-percent 

discharge withdrawal, and percentage of inundated area decreased by a potential 10-percent discharge 

withdrawal for each of the selected percentile discharges ..................................................................................... 53

33. Diagrams showing extent of areal inundation along the Alafia River channel and floodplain for the P10, P50, 

P70, P80, P90, P98, P99.5, and P99.9 discharges for existing conditions and a potential 10-percent discharge 

withdrawal...............................................................................................................................................................54-57

34. Graph showing water-surface profiles along the North Prong Alafia River for existing conditions and a 

potential 10-percent discharge withdrawal, from the confluence with the Alafia and South Prong Alafia 

Rivers to cross section 23 ............................................................................................................................................ 58

35. Diagram showing extent of areal inundation along the North Prong Alafia River channel and floodplain for 

selected percentile discharges, from the confluence with the Alafia and South Prong Alafia Rivers to cross 

section 23 ..................................................................................................................................................................... 59

36. Graph showing estimated total inundated area along the North Prong Alafia River for existing conditions and 

for a potential 10-percent discharge withdrawal, and percentage of inundated area decreased by a potential 

10-percent discharge withdrawal for each of the selected percentile discharges ........................................................ 60

37. Diagrams showing extent of areal inundation along the North Prong Alafia River channel and floodplain for 

the P10, P50, P70, P80, P90, P98, P99.5, and P99.9 discharges for existing conditions and a potential 10-percent 

discharge withdrawal ..............................................................................................................................................61-64

38. Graph showing water-surface profiles along the South Prong Alafia River for existing conditions and a

potential 10-percent discharge withdrawal, from the confluence with the Alafia and North Prong Alafia Rivers 

to cross section 29........................................................................................................................................................ 65

39. Diagram showing extent of areal inundation along the South Prong Alafia River channel and floodplain for 

selected percentile discharges, from the confluence with the Alafia and North Prong Alafia Rivers to section 29.... 66

40. Graph showing estimated total inundated area along the South Prong Alafia River for existing conditions and 

for a potential 10-percent discharge withdrawal, and percentage of inundated area decreased by a potential 

10-percent discharge withdrawal for each of the selected percentile discharges ........................................................ 67

41. Diagrams showing extent of areal inundation along the South Prong Alafia River channel and floodplain for 

the P10, P50, P70, P80, P90, P98, P99.5, and P99.9 discharges for existing conditions and for a potential 10-percent 

discharge withdrawal ..............................................................................................................................................68-71

42. Graph showing estimated total inundated area along the Alafia, North Prong Alafia, and South Prong Alafia 

Rivers for existing conditions and for a potential 10-percent discharge withdrawal, and percentage of inundated

area decreased by a potential 10-percent discharge withdrawal for each of the selected percentile discharges ......... 72
VI Contents

TABLES

1. Cross sections, drainage area, and percentile discharges used in step-backwater analysis based on the concurrent 

period 1965-98 at the Cypress Creek, Sulphur Springs, and San Antonio gages ..................................................................9

2. Approximate number of days daily mean discharge equaled or exceeded the selected percentile discharges at Cypress 

Creek near Sulphur Springs, 1965-98 ..................................................................................................................................12

3. Cross sections, drainage area, and percentile discharges used in step-backwater analysis based on the concurrent 

period 1940-98 at the Peace River at the Arcadia, Zolfo Springs, and Bartow gages .........................................................19

4. Approximate number of days daily mean discharge equaled or exceeded the selected percentile discharges at 

Peace River at Arcadia, 1940-98..........................................................................................................................................20

5. Cross sections, drainage area, and percentile discharges used in step-backwater analysis based on the concurrent 

period 1964-92 at the Alafia, North Prong Alafia, and South Prong Alafia Rivers gages...................................................48

6. Approximate number of days daily mean discharge equaled or exceeded the percentile discharges at Alafia River 

at Lithia, 1964-92.................................................................................................................................................................50

CONVERSION FACTORS, DATUMS, ACRONYMS, AND ABBREVIATIONS

ACRONYMS USE IN THIS REPORT

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD of 1929); 

horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).

Multiply By To obtain

acre 4047 square meter

foot (ft) 0.3048 meter

inch (in.) 25.4 millimeter

 mile (mi) 1.609 kilometer

square mile (mi2

) 2.590 square kilometer

cubic foot per second (ft3

/s) 0.02832 cubic meter per second

HEC–RAS Hydrologic Engineering Center River Analysis System

NWI National Wetlands Inventory

SR State Road

SWFWMD Southwest Florida Water Management District

US U.S. Highway

USGS U.S. Geological Survey
Abstract 1

Extent of Areal Inundation of Riverine Wetlands Along 

Cypress Creek and the Peace, Alafia, North Prong Alafia, 

and South Prong Alafia Rivers, West-Central Florida

By B.R. Lewelling

ABSTRACT

Riverine and palustrine system wetlands are a

major ecological component of river basins in

west-central Florida. Healthy wetlands are dependent upon the frequency and duration of periodic

flooding or inundation. This report assesses the

extent, area, depth, frequency, and duration of periodic flooding and the effects of potential surfacewater withdrawals on the wetlands along Cypress

Creek and the Peace, Alafia, North Prong Alafia,

and South Prong Alafia Rivers. Results of the study

were derived from step-backwater analysis

performed at each of the rivers using the U.S. Army

Corps of Engineers Hydrologic Engineering

Center-River Analysis System (HEC-RAS) onedimensional model. The step-backwater analysis

was performed using selected daily mean

discharges at the 10th, 50th, 70th, 80th, 90th, 98th,

99.5th, and 99.9th percentiles to compute extent of

areal inundation, area of inundation, and hydraulic

depth to assess the net reduction of areal inundation

if 10 percent of the total river flow were diverted

for potential withdrawals.

The extent of areal inundation is determined

by cross-sectional topography and the degree to

which the channel is incised. Areal inundation

occurs along the broad, low relief of the Cypress

Creek floodplain during all selected discharge

percentiles. However, areal inundation of the Peace

and Alafia Rivers floodplains, which generally

have deeply incised channels, occurs at or above

discharges at the 80th percentile. The greatest area

of inundation along the three rivers generally

occurs between the 90th and 98th percentile

discharges. The decrease in inundated area resulting from a potential 10-percent withdrawal in

discharge ranged as follows: Cypress Creek, 22 to

395 acres (1.7 to 8.4 percent); Peace River, 17 to

1,900 acres (2.1 to 13.6 percent); Alafia River, 1 to

90 acres (1 to 19.6 percent); North Prong Alafia

River, 1 to 46 acres (0.7 to 23.4 percent); and South

Prong Alafia River, 1 to 75 acres (1.5 to 13.4

percent).

INTRODUCTION

Locating alternative sources of water supply to

meet the demand caused by an increasing population

has become a major concern in west-central Florida.

The need for water supply is further complicated by

declining ground-water levels in the Upper Floridan

aquifer, the principal source of supply in the area.

Surface-water withdrawals from area rivers, however,

have become an increasingly important alternate

supply source. The health of the riverine wetlands
2 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

located along these rivers depends upon the frequency

and duration of periodic flooding or inundation. The

U.S. Geological Survey (USGS), in cooperation with

the Southwest Florida Water Management District

(SWFWMD), evaluated a potential range in areal inundation resulting from withdrawals of 10 percent of

average daily flows when flows exceed regulatory

minimum for Cypress Creek and the Peace, Alafia,

North Prong Alafia, and South Prong Alafia Rivers

(Southwest Florida Water Management District, 2001).

Purpose and Scope

The purpose of this report is to present the extent

of areal inundation using period-of-record streamflow

and the extent of areal inundation based on a potential

diversion of 10 percent of the total discharge during

periods when flows exceed the regulatory minimum

along Cypress Creek, and the Peace, Alafia, North

Prong Alafia, and South Prong Alafia Rivers (fig. 1).

Extent of areal inundation was determined for the 10th,

50th, 70th, 80th, 90th, 98th, 99.5th, and 99.9th percentiles.

Percentiles were determined based on the long-term

concurrent daily mean discharge record for gages on

Cypress Creek (1965-98), Peace River (1940-98), and

Alafia River (1964-92). Regulatory minimums determined by the SWFWMD for the Peace and Alafia

Rivers approximate the 10th percentile discharge used

in this report at 130 and 67 ft3/s, respectively.

Water-surface elevations at selected cross

sections of the study rivers were computed using the

U.S. Army Corps of Engineers Hydrologic Engineering Center-River Analysis System (HEC-RAS) onedimensional step-backwater model (Warner and Brunner, 1998). Computed water-surface elevations were

used to generate water-surface profiles, areal inundation width and acreage, and hydraulic depth (the ratio

of the cross-sectional area to the surface width). Existing hydrologic, hydraulic, and cross-sectional data

were used for the step-backwater analysis.

Previous Investigations

Most analyses of data from flooding events in

west-central Florida have focused on hazard and

damage analysis of peak flows and widespread areal

inundation for events with a relatively rare probability

of occurrence (for example, the 25-, 50-, or 100-year

flood). Robertson (1978) presented flood profiles based

on E431 step-backwater analysis (Shearman, 1976)

along a 19.2-mi reach of the Alafia River, a 9.5-mi

reach of the North Prong Alafia River, and a 9.8-mi

reach of the South Prong Alafia River. Murphy (1978)

computed flood profiles using E431 step-backwater

analysis along a 27.3-mi reach, from the mouth of

Cypress Creek to the gage at State Highway 52, and

along a 4.0-mi tributary and a 1.2-mi distributary reach.

Murphy and others (1978) computed flood profiles

using E431 step-backwater analysis along a 70-mi

reach of the Peace River from Arcadia to Bartow.

Acknowledgments

The author gratefully acknowledges Dr. Arthur

Miller, Pennsylvania State University, and the Texas

Department of Transportation for their assistance with

the HEC-RAS model. Special thanks are given to Caroline (Humphrey) Masek, engineering student, for her

contribution to the study.

DESCRIPTION OF STUDY AREA

The study area includes three river systems

located in west-central Florida: Cypress Creek in

south-central Pasco and north-central Hillsborough

Counties; Peace River in Polk, Hardee, and De Soto

Counties; and the Alafia, North Prong Alafia, and

South Prong Alafia Rivers in southeastern Hillsborough and southwestern Polk Counties (fig. 1). 

Based on map delineation by the National

Wetlands Inventory (NWI) of the U.S. Fish and Wildlife Service, the three study rivers have been classified

predominately as riverine system and palustrine system

wetlands (Cowardin and others, 1979). The riverine

system includes all the wetlands contained within a

channel, and the palustrine system consists of river

floodplains. Water in a riverine system is usually, but

not always, flowing. The riverine system is bounded by

the palustrine system, which is bounded by uplands. 

Cypress Creek is a major tributary to the Hillsborough River and is characterized by low-topographic

relief and frequent, widespread, and prolonged areal

inundation. Much of the 27-mi-long study reach has a

poorly incised and poorly defined low-gradient channel, located within a broad, swampy floodplain. The

extent of areal inundation at locations along Cypress

Creek can be large during the relatively low-discharge

conditions that occur at the 50th percentile or median

discharge (4 to 21 ft3/s).
Description of Study Area 3

75





41

17

4

275

83° 82°

28°27°





CYPRESS CREEK

ALAFIA RIVER--

PEACE RIVER

EXPLANATION

(a)(b)(c)

AREAS OF STUDY

Area

Shown

Florida

1

23

1

2

3

Reach 3 Reach 2 Reach 1 

North ProngSouth Prong

52

70

Cypress

Creek

Peace

River Alafia River South Prong

North

Prong

Gulf of Mexico

New Port Richey

Tampa

Clearwater

Bradenton

Sarasota

Arcadia

Port Charlotte

Sebring

Wauchula

Bartow

0 10

0 10

20 MILES

20 KILOMETERS

(a) (b)

(c)

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972Albers Equal-Area Conic projectionStandard Parallels 29°30′ and 45° 30′, central meridian -83° 00′

Figure 1. Location of study area including Cypress Creek and the Peace, Alafia, North Prong Alafia, and South Prong Alafia Rivers, west-central Florida.
4 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida DISCHARGE, IN CUBIC FEET PER SECOND

PERCENTILE DISCHARGE

0.1

1

10

100

1,000

10,000

100,000

99.99th 90th 80th 70th 60th 50th 40th 30th 20th 10th 0.00th

Peace River at Arcadia (1940-98)

Cypress Creek near Sulphur Springs (1965-98)

Alafia River near Lithia (1964-92)

No Flow

The Peace River channel generally is deeply

incised and well defined along most of the 70-mi-long

study reach, except for areas along the upper Peace

River where the banks are low lying. Much of the

surface drainage to the upper reach of the Peace River

is controlled by phosphate-mine outfall structures and

reclaimed channels. Surface drainage to the middle and

lower reaches of the Peace River typically is from welldeveloped, naturally formed tributaries. The Peace

River floodplain, generally characterized by low topographic relief, is subject to periodic inundation. 

Channels along the Alafia River system study

reaches typically are deeply incised, confining all but

the highest discharges within the bank. The Alafia

River system channel has a moderate gradient and

meanders slightly. The Alafia River is affected by

tidally influenced backwater from the mouth to the

reach directly downstream from the Alafia River at the

Lithia gage.

Unique physiographic characteristics (shape,

gradient, and length of the basin and channel) affect the

hydraulic conditions of the three river systems. Percentile discharges at each of the three study rivers were

determined from cumulative frequency curves for

selected record periods. Cumulative frequency curves

indicate the percentage of time that the daily mean

discharge is less than or equaled over specific periods

of time (fig. 2). Periods of zero flow at Cypress Creek

result from poorly incised channel reaches that occur

above the water table, limiting baseflow contribution.

Both the Peace and Alafia Rivers have similar flow

regimes due to the size of the watersheds and their

generally deeply incised channels, which support baseflow conditions sufficient to avoid zero-flow days.

Although the record periods differ, a comparison of the

50th percentile or median discharge for Cypress Creek,

Peace River and Alafia River indicates a wide variation

in flow characteristics, of 21, 481, and 184 ft3/s,

respectively. 

METHODOLOGY

The HEC-RAS step-backwater analysis model

was used to estimate water-surface elevation, extent of

areal inundation, and hydraulic depth at each cross

section. Water-surface profiles were generated along the

channels using computed water-surface elevation at each

cross section. Study river reaches are referenced in this

report from a downstream to upstream location, consistent with the direction the step-backwater analysis was

performed. 

Figure 2. Percentiles of daily mean discharge for the Peace River at Arcadia, Alafia River at Lithia, and Cypress 

Creek near Sulphur Springs gaging stations for selected periods.
Methodology 5

0 500 1,000 1,500 2,000 2,500

30

35

40

45

50

55

60

65

REFERENCE DISTANCE FROM LEFT BANK, IN FEET

ELEVATION, 

IN FEET ABOVE NGVD OF 1929

.05 .16 .07 .16 .05

Channel

Manning’s n-value Subarea 1

Cross Section Water Surface

Subarea 2

Subarea 4

Subarea 5

Subarea 3

Land-Surface Elevation

 Floodplain Floodplain

View Looking Downstream

Left Bank

Right Bank

Hydraulic and cross-sectional geometry data for

the stream channels and floodplains were determined

from three sources: (1) field surveys; (2) detailed aerial

1-ft topographic contour maps (scale 1:200); or

(3) previous step-backwater analyses by Murphy

(1978), Murphy and others (1978), and Robertson

(1978). Original E431 hydraulic and cross-sectional

data were reformatted or modified to be compatible

with HEC-RAS. 

Cross-section geometry of the channel and floodplains are defined by coordinates of both the horizontal

distance from the left bank (looking downstream) and

the corresponding land-surface elevation (fig. 3). The

land-surface elevation of the first and last horizontal

coordinate were selected to contain the highest watersurface elevation estimated at each cross section.

However, because water elevations computed in this

study represent more frequently occurring discharge

conditions, the maximum water-surface elevation rarely

approached the estimated elevation in the original stepbackwater analysis for a 100-year flood. The reference

distance of the cross-section location, measured in feet

upstream from the mouth, and the corresponding reference identification number assigned to each cross

section were obtained from the previous referenced

investigations of the three river systems. The area of

inundation for a given flow was estimated by extending

straight lines between the landward extents of inundation at the various cross sections and calculating the

water-surface area within this boundary. Such estimates

do not reflect the natural shape of the topographic

contours between adjacent cross sections. Selection of

cross-section locations were determined to best represent

existing field conditions along the reach.

Cross sections were divided into subareas based

on existing hydraulic characteristics. The Manning’s

roughness coefficient, n, was used to describe the degree

of flow resistance of the channel and floodplain, and is a

function of bed material size, depth of flow, cross

sectional geometry, type and density of vegetation, and

degree of channel meandering. Most of the roughness

coefficients used in previous step-backwater analyses of

Cypress Creek (Murphy, 1978), Peace River (Murphy

and others, 1978), and Alafia River (Robertson, 1978)

were used in this study. 

Percentile discharges used in the step-backwater

analysis were based on concurrent long-term streamflow

records for each study location. Selected percentiles

included the 10th, 50th, 70th, 80th, 90th, 98th, 99.5th, and

99.9th. Percentile is a value on a scale of 0 to 100 that

indicates the percentage of a streamflow distribution that

is equal to or less than a specific discharge. For example,

at the 90th percentile discharge, 90 percent of the flows

are equal to or less than a specific discharge, based on

the selected period, and 10 percent of the flows are

greater. To simplify terminology in this report, the 10th

percentile of daily mean discharge is identified as P10

discharge, the 50th percentile as the P50 discharge, and so

forth for each of the selected percentile discharges. Also,

the potential 10-percent withdrawal at the P10 discharge

is identified as P10-10 discharge, the P50 discharge as the

P50-10 discharge, and so forth. The P10 discharge was

omitted from the Cypress Creek analysis because the

daily mean discharge was less than 0.01 ft3/s.

Figure 3. Example cross section showing Manning’s n-values, subareas, and water-surface elevation.
6 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

To estimate differences in area of inundation

resulting from a potential 10-percent surface-water

withdrawal for the three river systems, a second stepbackwater analysis was performed using 10-percent

less discharge for each of the selected percentile

discharges. To differentiate between the two analyses,

the analysis performed using 100 percent of the

discharge for the selected period of record is identified

as the “existing step-backwater analysis” and the analysis performed using 10-percent less discharge is identified as the “potential step-backwater analysis.”

Results of the existing and potential analyses were then

compared to evaluate effects of the potential withdrawals.

The reliability of the step-backwater analysis is

limited by the quality of hydraulic and cross-sectional

data. The basis for the selection of discharge data is

critical when considering the period of record for analysis and the confidence in the data and method used to

develop the analysis. Selection of Manning’s n-value

roughness coefficients is subjective, and affects the

computed water-surface elevation at a cross section.

Accuracy of the cross-sectional data, whether field

surveyed or determined from aerial-contour maps,

affects the reliability of the results of the step-backwater analysis. If the distance between adjacent crosssection locations is too great, it can affect the stepbackwater energy balance computation. Results of the

step-backwater analysis are judged to be good when

the computed water-surface elevation converges

successfully within +/- 0.5 ft of the established stagedischarge relation at an upstream gaged cross section.

CYPRESS CREEK

Cypress Creek drains approximately 164 mi 2 in

south-central Pasco and north-central Hillsborough

Counties and is a major tributary to the Hillsborough

River (fig. 1). The upstream half of the watershed is

largely undeveloped, whereas the downstream half is

dominated by numerous residential subdivisions. The

floodplain is characterized by low topographic relief

and frequent, widespread, and prolonged areal inundation. The low-gradient channel generally is poorly

incised and poorly defined. The USGS operates three

long-term streamflow gages on Cypress Creek at:

Sulphur Springs (02303800); Worthington Gardens

(02303420); and San Antonio (02303400) (fig. 4).

Railroad

Well-field

Control

Structure

San Antonio 

Gaging Station

02303400

99

100 102

98

96

97

94

92 90

88

86 85 84

81

80

78

76

74

72

70

68

66

64

62

60

58

56

57

UPPER STUDY 

LIMIT

Cyp r ess Creek

EXPLANATION

GAGING STATION-- 

 With site number

CROSS SECTION-- 30 With number

54 55

53 51

50 49 48 47 46

44 42

40

38

36 37

34

32

33

30

28

26

24

22

20

18

16

15

14

12

10

9 7

6

4

2

1

Hillsborough River

Cypress

Creek

275

54

52

581

Fletcher Avenue Lower Study Limit



Worthington Gardens 

Gaging Station

02303420

Sulphur Springs 

Gaging Station

02303800

75

28°05′

28°10′

28°15′

28°20′

82°27′30′′ 82°22′30′′

Base from Florida Highway Department

County Highway Maps 1:63,360

0 2 MILES

0 2 KILOMETERS

Figure 4. Locations of Cypress Creek and the Sulphur 

Springs, Worthington Gardens, and San Antonio gaging 

stations and the study cross sections, west-central Florida. 

(Location of study area shown in figure 1).
Cypress Creek 7

The Cypress Creek channel and floodplain were

delineated by the NWI and are classified as predominately forested wetlands of the palustrine system.

Because the channel is poorly incised and poorly

defined along most of its length, limited open-water

reaches are classified as riverine wetlands. These riverine wetlands typically are located along contracted

reaches bounded by uplands. The forested wetlands

that occur along the broad Cypress Creek floodplain

are classified by the NWI as either broad-leaved,

needle-leaved, or indeterminate deciduous. The length

of the study floodplain corridor is bounded by uplands.

Step-backwater analysis was performed along

the 27.3-mi Cypress Creek study reach, from the mouth

at the confluence with the Hillsborough River to the

San Antonio gage at SR 52 (fig. 4). Initial watersurface elevations for each of the selected percentile

discharges were determined from the stage-discharge

relation developed at the Sulphur Springs gage at

SR 581. Selected percentile discharges, P50, P70, P80,

P90, P98, P99.5, and P99.9, were based on the concurrent

period 1965-98 at the Sulphur Springs and San Antonio

gages. The Worthington Gardens gage at SR 54 was

not included in the analysis because the gage had a

10-yr shorter period of record than the other two gages.

However, the stage-discharge relation developed at the

Worthington Gardens gage was used to check

computed water-surface elevations.

Water-surface profiles were based on elevations

computed at the 97 cross sections along Cypress Creek

for each of the seven selected percentile discharges

(fig. 5). Water-surface elevations computed at the

Worthington Gardens and San Antonio gages for each

of the percentile discharges were considered reliable

because they converged within 0.5 ft of the developed

stage-discharge relation. Modeled discharges were

proportionally reduced at selected upstream cross

sections during the analysis to adjust for the decrease in

size of contributing drainage area (table 1). 

Topographic relief, channel gradient and depth,

and discharge control the extent of areal inundation

along Cypress Creek. Areal inundation may be

substantial during relatively low-discharge conditions.

At the mouth of Cypress Creek, for example, the width

of the areal extent of inundation can range from more

than 6,000 ft during a P50 discharge (21 ft3/s) to 8,000 ft

during a P99.9 discharge (1,602 ft3/s) (figs. 6 and 7a and

app. A). Many cross sections along Cypress Creek

have low topographic relief that result in widespread

areal inundation for most of the selected percentile

discharges. The reach from the Interstate 75 bridge

(cross section 33) to the arched bridge (cross section

54) is controlled by high relief, limiting areal inundation to only the highest percentile discharges (fig. 6).

A comparison of the maximum extent of areal inundation for the selected percentile discharges at each cross

section is shown in figure 6. However, the figure does

not indicated the existence of elevated land surface

along the cross section that may be completely inundated during high-flow periods or may form islands

during low-flow periods, thus reducing the actual

distance inundated. Appendix A presents the actual

distance, in feet, each cross section is inundated.

Based on the number of days that streamflow

equaled or exceeded the selected percentile discharges

during the 34-year study period, areal inundation along

Cypress Creek was highly variable among years (table 2).

The number of days that flow was at the P50 discharge

ranged from a minimum of 35 days (1992) to a maximum of 284 days (1966), with an average of 180 days

per year. However, the P99.9 discharge occurred only

once (1965) for a 2-day period. By far the percentiles

of common occurrence to the wetlands are the P50, P70,

P80, P90 discharges, which generally occur annually,

with durations typically exceeding 100 days during

moderate-to-wet conditions. The frequency of the P98

and P99.5 discharges occurred in less than one-half of

the years during the 34-year record period. 

The estimated mean number of days per year

during the 34-year record that selected percentile

discharges occurred at two example cross sections are

shown in figure 7. Cross section 1 is widely inundated

during the P50 discharge, which occurs on an average of

180 days per year. At cross section 28, however, the

extent of areal inundation for the P50 discharge is

confined within the banks of the channel during that

same period. Areal inundation of the floodplain along

the entire study reach occurs only for percentiles above

the P70 discharge. Floodplain inundation at the P80

discharge occurs an average of 72 days per year.

Hydraulic depths were computed at each cross

section for the selected percentile discharges (app. B).

Because the channel is not well defined or incised

along much of Cypress Creek, hydraulic depth at many

cross sections can be considered an estimate of the

floodplain inundation depth. Hydraulic depth increases

at locations where reaches contract, whether the

contraction is the result of channel modifications, such

as a bridge, culvert, or control structure, or the result of

the natural topography (fig. 5). Differences in hydraulic
8 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

20

30

40

50

60

70

80

1 4 6 7 10 12

14

15

18

2022 24 26

28 30 3233.3 36374042 44 46

47

49

50 50.5555657

58

60

62

64

66

68

70 72

74 76

78 80

84

85

86 88

90

92

94

96

97

DISTANCE UPSTREAM FROM MOUTH, IN FEET

Cypress

ELEVATION, IN FEET ABOVE NGVD OF 1929

 Springs Gaging StationSR 581 Bridge and Sulphur

Interstate 75 Bridge (Hillsborough Co)

 Line Road Bridge

Hillsborough-Pasco County

 (Pasco Co)

Interstate 75 Bridge

 Gardens Gaging Station

Arch Bridge

 water Control StructureCypress Creek Wellfield SurfaceSan Antonio Gaging Station

Creek

Cypress Creek

Mouth

Solid lines indicate percentile discharge profile

0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 10,000 30,000 50,000 70,000 90,000 110,000 130,000 150,000 SR 52

Dashed lines indicate potential 10-percent discharge withdrawal

2

Channel

Maximum Elevation

 of Bridge Opening

Cross Section Number

Land-Surface Elevation

8

SR 54 Bridge and Worthington

P99.9

P99.5

P98

P90

P80

P70

P50

P98-10

P90-10

P70-10

P50-10

P99.5-10

P99.9-10

P80-10

depth shown at cross sections 1 (mouth) and 28 in

figure 7 may be attributed to topography, channel

configuration, and slope. Hydraulic depth at cross

section 1 is affected by backwater from the Hillsborough River. Mean hydraulic depth of the channel and

floodplain ranged from approximately 0.85 to 2.89 ft.

The relatively shallow mean depths of Cypress Creek

reflect the effects of widespread inundation.

Areal inundation along Cypress Creek was

computed in acres for each of the selected percentile

discharges (app. C). Total acreage of inundated area

along Cypress Creek was calculated by totaling the

computed water-surface area between adjacent cross

sections. This calculation was done for each of the

selected percentile discharges. Areal inundation ranged

from approximately 1,200 (P50) to 9,000 (P99.9) acres

(fig. 8). The greatest increase in inundated area

between percentile discharges is 2,326 acres, which

occurs between the P90 to the P98 discharges.

Based on the period of streamflow record 1965-98,

the difference in total inundated area of the existing

step-backwater analysis was compared to the inundated

area that resulted from a potential 10-percent withdrawal in streamflow. This evaluation was made by

Figure 5. Water-surface profiles along Cypress Creek for existing conditions and a potential 10-percent discharge withdrawal, 

from the mouth to SR 52.
Peace River 9

performing a second step-backwater analysis for the

concurrent period using the same selected percentile

discharges reduced by 10 percent. The difference in the

total inundated area was compared between the two

step-backwater analyses. Hydraulic and geometric data

used for both analyses were identical, except for the

starting discharge and water-surface elevation used at

the initial cross section. Rated and computed watersurface elevations of the second step-backwater analysis converged successfully at both the Worthington

Garden and the San Antonio gages. A comparison in

elevation of the computed water-surface profiles resulting from a potential 10-percent discharge withdrawal is

shown in figure 5. The lower water-surface elevation

profiles resulting from a potential 10-percent discharge

withdrawal reduces the extent of areal inundation from

about 22 (P50) to 395 (P90) acres, which corresponds to

an approximate 1.7 and 8.4 percent decrease of inundated area, respectively (fig. 8 and app. D). The greatest decrease in inundated area (395 acres) occurs at the

P90-10 discharge (fig. 9a-g), and most of the decrease in

area is attributed to the reaches between cross sections

70, 72, and 74 (fig. 9d).

PEACE RIVER

The 2,350-mi2 Peace River watershed is located

in Polk, Hardee, De Soto, and Charlotte Counties

(fig. 10). The Peace River begins northeast of Bartow,

at the confluence of Saddle Creek and the Peace Creek

Drainage Canal, and flows southward for about 105 mi

to Charlotte Harbor. The watershed is predominately

rural with several small municipalities. Much of the

upper and middle watershed has been strip-mined for

phosphate and subsequently reclaimed. 

Generally well defined and deeply incised, the

Peace River channel is delineated on maps by the NWI

predominately as a riverine system (Cowardin and

others, 1979). The riverine system is further classified

as lower perennial because the gradient is low and the

velocity is slow. In areas along the upper Peace River,

where the channel is poorly defined and poorly incised,

the channel may be classified as a palustrine forest

wetland. Palustrine wetlands, dominated by either

broad-leaved, needle-leaved, or indeterminate deciduous forest, occur along most of the Peace River floodplain. The length of the study floodplain corridor, from

Arcadia to Bartow, is bounded by uplands.

Surface-water drainage to the upper Peace River,

from Bartow to Bowling Green, is generally limited to

phosphate-mine outfalls and reclaimed channels.

Along this reach, much of the natural surface drainage

has been altered by the effects of strip mining. Surfacewater drainage to the Peace River, from downstream of

Bowling Green to Charlotte Harbor, typically is from

well-developed, naturally formed tributaries. The

lower reach of the Peace River, from downstream of

Arcadia to Charlotte Harbor, is affected by tidally

influenced backwater. 

Table 1. Cross sections, drainage area, and percentile discharges used 

in step-backwater analysis based on the concurrent period 1965-98 at the 

Cypress Creek, Sulphur Springs, and San Antonio gages

[ft3/s, cubic feet per second; mi2, square miles]

Crosssection 

range

Drainage 

area (mi2)

Discharge (ft3/s)

P50 P70 P80 P90 P98 P99.5 P99.9

1-8 165 21 67 124 250 670 1,124 1,602

19-17 160 20 65 120 242 650 1,090 1,554

18-26 134 13 44 80 164 449 796 1,233

28-48 122 12 40 73 149 409 725 1,123

240-72 117 12 38 70 143 392 695 1,077

74-81 76 8 25 46 93 255 451 700

82-94.5 70 7 23 42 86 235 416 644

395-102 56 4 14 25 52 148 284 487

1Sulphur Springs gage at SR 581.

2Worthington Gardens gage at SR 54.

3San Antonio gage at SR 52.
10 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

Cypress Creek

P99.9

P99.5

P98

P90

P80

P70

P50

EXPLANATION

Percentile Discharges

0 500 1,000 1,500 2,000 METERS

0 2,000 4,000 6,000 8,000 FEET

102

96 95 94

92

90

88

86

84

82

78 76

74

72

70

68

66

64

62

60

58

57

56

55

54

50

48

46

44

42

40

36

34 33

32

30

28

26

24

22

20

18

17 16

14

12

10

9

6

4

2

1

100

39

Sulphur Springs Gaging Station

SR 581 Bridge

Interstate 75 Bridge

(Hillsborough County)

Hillsborough-Pasco

Countyline Bridge

Interstate 75 Bridge

 (Pasco County)

Worthington Gardens Gaging Station

SR 54 Bridge

Cypress Creek

Wellfield SurfaceWater Control

San Antonio Gaging Station

SR 52 Culvert Flow

Cypress Creek

 Channel

CROSS SECTION

Mouth

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

Arched Bridge

15

CROSS SECTION NUMBER

Figure 6. Extent of areal inundation along the Cypress Creek channel and floodplain for selected 

percentile discharges.
Peace River 11

ELEVATION, IN FEET ABOVE NGVD OF 1929

DISTANCE FROM LEFT BANK, IN FEET

Cypress Creek Channel

Interstate 275

P99.9, 1.67 ft

P99.5, 1.32 ft

P98, 0.91 ft

P90, 0.71 ft

P80, 0.37 ft

P50, 0.67 ft

P70, 0.82 ft

0 2,000 4,000 6,000 8,000 10,000

42

40

38

36

34

32

44

46

48

50

 

Based on 34 Years Record, 1965-98

Cypress Creek near Sulphur Springs

 Percentile Mean number Occurrence 

 days/yr in years 

 P50 180 34

 P70 114 33

 P80 72 31

 P90 37 27

 P98 19 16

 P99.5 4 9

 P99.9 2 1 

(b) 

20

25

30

40

35

45

0 2,000 4,000 6,000 8,000 10,000

P99.9, 5.05 ft

Cypress Creek Channel

P99.5, 4.79 ft

P98, 4.35 ft

P90, 3.51 ft

P80, 2.96 ft

P50, 1.80 ft

P70, 2.49 ft

DISTANCE FROM LEFT BANK, IN FEET

(a)

P99.9 Percentile Discharge

1.67 ft Hydraulic Depth

EXPLANATION

P99.9 Percentile Discharge

5.05 ft Hydraulic Depth

EXPLANATION

Cross Section 28

Cross Section 1

Looking Downstream

Looking Downstream

Land-Surface Elevation

Cypress Creek

Cypress Creek

Figure 7. Estimated extent and frequency of areal inundation and hydraulic depth for Cypress Creek at selected 

cross sections for each of the selected percentile discharges.
12 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

Step-backwater analysis was performed at 238

cross sections located along a 70-mi length of the

Peace River channel from Arcadia to Bartow. Stepbackwater analysis was performed using the selected

percentile discharges (P10, P50, P70, P80, P 90, P98, P99.5,

and P99.9) for the concurrent long-term period 1940-98

at three Peace River gages: Arcadia (02296750); Zolfo

Springs (02295637); and Bartow (02294650). Proportionally reduced discharges, based on gaged data, were

introduced into the step-backwater analysis at selected

cross sections to compensate for the decrease in

contributing drainage area (table 3). 

Because of the large number of cross sections

and variations in channel and hydraulic characteristics,

the step-backwater analysis of the Peace River was

divided into three study reaches. Each reach began and

ended at a long-term streamflow gage. Reach 1

included 81 cross sections along the 32.3-mi length

from the Arcadia to Zolfo Springs gages; reach 2

included 95 cross sections along the 23.6-mi length

from the Zolfo Springs to Fort Meade gages; and reach 3

included 64 cross sections along the 13.9-mi length

from the Fort Meade to Bartow gages (fig. 10). The

reach downstream from Arcadia to Charlotte Harbor

was not included in the analysis because of tidally

affected backwater conditions. Cross sections used for

the Peace River were developed by Murphy and others

(1978), except at bridge locations. 

The number of days areal inundation occurs annually along the Peace River for a specific percentile

discharge is variable, based predominantly on seasonal

climatic conditions. However, discharge conditions

along the upper Peace River may be affected by a

limited number of surface-water control structures at

phosphate-mine outfalls and losses to sinkholes. Most of

the percentiles at or below the P90 discharge occur annually, based on the Arcadia gage (table 4). However, the

highest percentile discharge (P99.9) occurred for only

6 years out of the 59-year period, 1940-98.

Reach 1–Arcadia to Zolfo Springs

The Peace River channel along reach 1, from

Arcadia to Zolfo Springs, is generally broad, well

defined, and deeply incised (fig. 11). The channel

generally confines all but the highest discharges within

the banks. Numerous meanders and oxbows along the

reach are characteristic of a sandy, low-gradient channel. Daily mean discharge at the Arcadia gage during

the study period (1940-98) ranged from 14 to 24,200

ft3/s, with a median discharge of 481 ft3/s (P50) (fig. 2).

Table 2. Approximate number of days daily mean 

discharge equaled or exceeded the selected percentile

discharges at Cypress Creek near Sulphur Springs,

1965-98

[P50, 50-percentile discharge; --, no days]

Year

Number of days/year

P50 P70 P80 P90 P98 P99.5 P99.9

1965 258 176 101 66 33 10 2

1966 284 216 134 61 -- -- --

1967 188 118 57 34 11 -- --

1968 112 80 48 6 -- -- --

1969 263 121 83 49 8 2 --

1970 277 257 190 109 16 -- --

1971 155 81 47 20 5 -- --

1972 189 95 30 -- -- -- --

1973 178 120 82

1974 211 150 115 77 19 1 --

1975 169 86 64 16 -- -- --

1976 207 132 61 9 -- -- --

1977 122 18 4 -- -- -- --

1978 219 144 87 41 3 -- --

1979 156 108 83 44 22 1 --

1980 209 73 32 73 10 1 --

1981 113 77 50 77 17 -- --

1982 246 173 114 62 13 4 --

1983 283 227 165 103 34 4 --

1984 277 211 106 16 -- -- --

1985 61 57 48 25 5 -- --

1986 232 158 57 10 -- -- --

1987 282 123 58 26 13 5 --

1988 156 69 35 18 12 -- --

1989 156 74 38 10 -- -- --

1990 57 -- -- -- -- -- --

1991 104 68 46 8 -- -- --

1992 35 9 -- -- -- -- --

1993 92 23 -- -- -- -- --

1994 59 34 9 -- -- -- --

1995 206 104 57 13 -- -- --

1996 226 134 45 13 -- -- --

1997 72 34 11 3 -- -- --

1998 267 219 182 133 84 10 --

Mean

number 

days

180 114 72 37 19 4 2
Peace River 13

PERCENTILE DISCHARGE

TOTAL INUNDATED AREA, IN ACRES

50 70 80 90 98 99.5 99.9 th th th th th th th

Area inundated

Area inundated after a 10-percent

discharge withdrawal

Cypress Creek 1965-98

Lines indicate interpolated inundated area

Percent inundated

area decreased

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

1.7 %

5.0 %

4.8%

8.4 %

3.3 %

3.5 %

2.6 %

Water-surface profiles were based on elevations

computed at the 81 cross sections along reach 1 for

each of the eight selected percentile discharges (fig. 12).

Extent of areal inundation, acreage of inundation, and

hydraulic depth also were computed based on the

results of the water-surface elevations. 

Estimated maximum extent of floodplain inundation exceeds 12,400 ft (cross section 264) during P99.9

discharge (fig. 13 and app. E). Mean extent of inundation for the 81 cross sections along the reach 1 can range

from 99 ft (P10) to 5,181 ft (P99.9). The channel along

much of the reach generally confines most flow regimes

at or below the P80 discharge (fig. 13). The mean inundation extent at the P80 discharge (238 ft) approximates the

channel width. Mean inundation extents are similar for

both the P99.5 (4,529 ft) and P99.9 (5,181 ft) discharges,

which indicates a limited increase in inundation for

increased discharge at these percentiles. However, an

approximate four-fold increase in mean inundation

extent occurs from the P90 (625 ft) to the P98 (2,521 ft)

discharge, and about a two-fold increase from the P98

(2,521 ft) to the P99.5 (4,529 ft) discharge. A comparison

of the maximum extent of areal inundation for the

selected percentile discharges at each cross section is

shown in figure 13. However, the figure does not indicated the existence of elevated land surface along the

cross section that may be completely inundated during

high-flow periods or may form islands during low-flow

periods, thus reducing the actual distance inundated.

Appendix E presents the actual distance, in feet, each

cross section is inundated.

The estimated mean number of days a year and

the number of years during the 59-year record that

selected percentile discharges occurred at three example cross sections for the Peace River are shown in

figure 14. In example cross section 208 (fig. 14a),

surface-water elevations at or below the P90 discharge

are confined within the banks of the channel and elevations at or above the P98 discharge can inundate the

floodplain.

Hydraulic depths for the selected percentile

discharges ranged from a minimum of 0.8 to a maximum of 12 ft, and a mean of 1.7 to 5.4 ft (app. F). A

mean depth of approximately 5 ft occurs during the P80

discharge, and generally is confined within the channel.

Because of the large cross-sectional area of the floodplain, hydraulic depths may be relatively shallow for

those higher percentile discharges that inundate both

the channel and the floodplain, which is illustrated in

example cross section 208 (fig. 14a). The hydraulic

depth for the P90 discharge is 10.2 ft, whereas, the P98

discharge depth is only 2.4 ft.

Figure 8. Estimated total inundated area along Cypress Creek for existing conditions and for a potential 10-percent 

discharge withdrawal, and percentage of inundated area decreased by a potential 10-percent discharge withdrawal for 

each of the selected percentile discharges.
14 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

102

96 95 94.5

92

90

88

86

84

82

78

76

74

72

70

68

66

64

62

60

58

57

56 55

54

50

48

46

44

42

40

36

34 33

32

30

28

26

24

22

20

18

17 16

14

12

10

9.5

6.2

4

2

1

100

39

102

96 95 94.5

92

90

88

86

84

82

78

76

74

72

70

68

66

64

62

60

58

57

56 55

54

50

48

46

44

42

40

36

34 33

32

30

28

26

24

22

20

18

17 16

14

12

10

9.5

6.2

4

2

1

100

39

Mouth

Sulphur Springs Gaging Station

SR 581 Bridge

Interstate 75 Bridge

(Hillsborough County)

Hillsborough-Pasco

Countyline Bridge

Interstate 75 Bridge

(Pasco County)

Worthington Gardens Gaging Station

SR 54 Bridge

Cypress Creek

Wellfield 

SurfaceWater 

Control

San Antonio Gaging Station

SR 52 Culvert

Flow

Cypress Creek Channel

CROSS SECTION

Cypress Creek

(a) (b)

P50 P70

P P 50-10 70-10 (a) and (b)

 P P 50 70 (a) and (b)

EXPLANATION

Mouth

CROSS SECTION NUMBER

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

0 500 1,000 1,500 2,000 METERS

0 2,000 4,000 6,000 8,000 FEET

Figure 9. Extent of areal inundation along Cypress Creek for the (a) P50, (b) P70, (c) P80, (d) P90, (e) P98, (f) P99.5, 

and (g) P99.9 discharges for existing conditions and a potential 10-percent discharge withdrawal. 
Peace River 15

102

96 95 94.5

92

90

88

86

84

82

78 76

74

72

70

68

66

64

62

60

58

57

56 55

54

50

48

46

44

42

40

36

34 33

32

30

28

26

24

22

20

18

17 16

14

12

10

9.5

6.2

4

2

1

100

39

102

96 95 94.5

92

90

88

86

84

82

78

76

74

72

70

68

66

64

62

60

58

57

56 55

54

50

48

46

44

42

40

36

34 33

32

30

28

26

24

22

20

18

17 16

14

12

10

9.5

6.2

4

2

1

100

39

Mouth

Sulfur Springs Gaging Station

SR 581 Bridge

Interstate 75 Bridge

(Hillsborough County)

Hillsborough-Pasco

Countyline Bridge

Interstate 75 Bridge

 (Pasco County)

Worthington Gardens Gaging Station

SR 54 Bridge

Cypress Creek

Wellfield SurfaceWater Control

San Antonio Gaging Station

SR 52 Culvert

Flow

Cypress Creek Channel

CROSS SECTION

Cypress Creek

(c) (d)

Mouth

CROSS SECTION NUMBER

P80-10 (c) and P90-10 (d)

 P80 (c) and P90 (d)

EXPLANATION

0 500 1,000 1,500 2,000 METERS

0 2,000 4,000 6,000 8,000 FEET

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

P80 P90

Figure 9. Extent of areal inundation along Cypress Creek for the (a) P50, (b) P70, (c) P80, (d) P90, (e) P98, (f) P99.5, 

and (g) P99.9 discharges for existing conditions and a potential 10-percent discharge withdrawal. (Continued)
16 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

102

96 95 94.5

92

90

88

86

84

82

78

76

74

72

70

68

66

64

62

60

58

57

56 55

54

50

48

46

44

42

40

36

34 33

32

30

28

26

24

22

20

18

17 16

14

12

10

9.5

6.2

4

2

1

100

39

102

96 95 94.5

92

90

88

86

84

82

78

76

74

72

70

68

66

64

62

60

58

57

56 55

54

50

48

46

44

42

40

36

34 33

32

30

28

26

24

22

20

18

17 16

14

12

10

9.5

6.2

4

2

1

100

39

Mouth

Interstate 75 Bridge

(Hillsborough County)

Hillsborough-Pasco

Countyline Bridge

Interstate 75 Bridge

 (Pasco County)

Worthington Gardens Gaging Station

SR 54 Bridge

Cypress Creek

Wellfield

SurfaceWater

Control

San Antonio Gaging Station

SR 52 Culvert

Flow

Cypress Creek Channel

CROSS SECTION

LIMIT OF STUDY

FLOODPLAIN

BOUNDARY

Cypress Creek

(e) (f)

Sulphur Springs Gaging Station

SR 581 Bridge

P98 P99.5

CROSS SECTION NUMBER

P98-10 (e) and P99.5-10 (f)

 P98 (e) and P99.5 (f)

EXPLANATION

0 500 1,000 1,500 2,000 METERS

0 2,000 4,000 6,000 8,000 FEET

Figure 9. Extent of areal inundation along Cypress Creek for the (a) P50, (b) P70, (c) P80, (d) P90, (e) P98, (f) P99.5, 

and (g) P99.9 discharges for existing conditions and a potential 10-percent discharge withdrawal. (Continued)
Peace River 17

102

96 95 94.5

92

90

88

86

84

82

78

76

74

72

70

68

66

64

62

60

58

57

56 55

54

50

48

46

44

42

40

36

34 33

32

30

28

26

24

22

20

18

17 16

14

12

10

9.5

6.2

4

2

1

100

39

Mouth

Interstate 75 Bridge

(Hillsborough County)

Hillsborough-Pasco

Countyline Bridge

Interstate 75 Bridge

 (Pasco County)

Worthington Gardens Gaging Station

SR 54 Bridge

Cypress Creek

Wellfield SurfaceWater Control

San Antonio Gaging Station

SR 52 Culvert

Flow

LIMIT OF STUDY 

FLOODPLAIN 

BOUNDARY

Cypress Creek

 Channel

CROSS SECTION

Cypress Creek

(g)

Sulphur Springs Gaging Station

SR 581 Bridge

P99.9

P99.9-10

P99.9

EXPLANATION

CROSS SECTION 

NUMBER

0 500 1,000 1,500 2,000 METERS

0 2,000 4,000 6,000 8,000 FEET

Total area of areal inundation within the channel

and floodplain for reach 1 ranged from 377 to 17,196

acres for the selected percentile discharges (fig. 15 and

app. G). Inundated area that occurred below the P80

discharge generally was confined within the banks of

the channel (fig. 13). The difference in total area inundated between the P10 (377 acres) and P80 (888 acres)

discharges was 511 acres, which largely included just

the channel. However, the area between the P90 (2,120

acres) and P99.9 (17,196 acres) discharges was greater

than 15,000 acres, which included both the channel and

the floodplain. The greatest increase in area of inundation occurred from the P90 to P98 discharges and from

the P98 to P99.5 discharges, with more than 6,000 acres

each.

Based on the period of streamflow record, 1940-98,

differences in the total inundated area of the existing stepbackwater analysis were compared with a potential reduction in streamflow of 10 percent. The loss of inundated

area between the existing step-backwater analysis and the

potential step-backwater analysis ranged from approximately 5 (P10) to 1,500 (P98) acres, which corresponds to a

decrease in inundated area of 1.3 and 17.8 percent, respectively (fig. 15 and app. H). Decreases of inundated area at

or below the P80-10 discharge generally occurred within

the channel and ranged from 5 to 110 acres (fig. 16a-h

and app. H). The greatest decrease of inundated

area occurred at the P98-10 discharge with 1,469 acres.

The decrease in inundated area at both the P99.5-10 and the

P99.9-10 discharges was greater than 700 acres.

Reach 2–Zolfo Springs to Fort Meade

Reach 2 of the Peace River, from Zolfo Springs

to Fort Meade, shares many of the same channel characteristics as reach 1 (fig. 17). The channel is generally

well defined and deeply incised, confining low-tomoderate discharges (P10, 106 ft3/s to P50, 329 ft3/s)

within the banks. At many locations along the channel,

the banks are formed from rock outcrops. Daily mean

discharge at the Zolfo Springs gage during the study

period (1940-98) ranged from 19 to 15,200 ft3/s, with a

median discharge of 329 ft3/s (P50).

The step-backwater analysis computed watersurface profiles using 95 cross sections along the 23.6-mi

reach 2 (fig. 18). Mean inundation extent along reach 2,

based on the average of 95 cross sections along the

reach, was similar to that of reach 1 for the P10 (82 ft)

through P90 (448 ft) discharges, due to similar channel

Figure 9. Extent of areal inundation along Cypress Creek 

for the (a) P50, (b) P70, (c) P80, (d) P90, (e) P98, (f) P99.5, 

and (g) P99.9 discharges for existing conditions and a 

potential 10-percent discharge withdrawal. (Continued)
18 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

28°00′

82°15′ 82°00′ 81°30′ 45′

27°00′

45′

30′

15′

37

17

92

98

98

4

17

17

60

37

630

62

64

64

66

70

70

72

74

31

41 75

Bow l eg s

Creek

Payne Creek

Char lie

Cree k

Saddle Creek

Punta Gorda

Port Charlotte

Fort Ogden

Arcadia

Brownville

Gardner

Zolfo Springs

Wauchula

Bowling Green

Fort

Meade 

Homeland

Lake ales

Bartow

Lakeland Winter

Haven 

Bermont

EXPLANATION

PEACE RIVER-- 

 Basin boundary

Reach 3 

Reach 2 

Reach 1 

CITY OR TOWN

Lake

Hancock

Peace Creek

Drainage

 Canal

Base from SWFWMD digital data, 1:250,000, 1992

Albers Equal-Area Conic Projection

Standard Parallels 29°30′ and 45°30′, central meridian -83°00′

Lake Alfred

W

Peace 

River

0 5 10 MILES

0 5 10 KILOMETERS 

Horse

C

reek

GAGING STATION

Charlotte

Harbor

STUDY REACHES--

Figure 10. Location of 

the Peace River, study 

reaches, and the 

Arcadia, Zolfo Springs, 

Fort Meade, and Bartow 

gaging stations, westcentral Florida. 

(Location of study area 

shown in figure 1).
Peace River 19

characteristics (app. I). Maximum estimated floodplain

inundation exceeds 4,600 ft (cross section 294) during

P99.9 discharge. Mean extent for the 95 cross sections

along the reach ranged from approximately 82 ft (P10)

to 2,542 ft (P99.9). The channel generally confines most

discharges at or below the P90 discharge, except at a

few cross sections of low relief (fig. 19). The mean

extent at the P80 discharge (209 ft) approximates the

mean extent of a bankfull channel. Increases in the

extent of mean areal inundation, of over 750 ft, occur

from both the P90 (448 ft) to the P98 (1,209 ft) discharge

and from the P98 (1,209 ft) to the P99.5 (2,063 ft)

discharge (app. I). Example cross section 292 shows

river stages at or below the P90 discharge are generally

confined within the banks of the channel, whereas

those above may inundate the floodplain (fig. 14b).

A comparison of the maximum extent of areal inundation for the selected percentile discharges at each cross

section is shown in figure 19. However, the figure does

not indicated the existence of elevated land surface

along the cross section that may be completely inundated during high-flow periods or may form islands

during low-flow periods, thus reducing the actual

distance inundated. Appendix I presents the actual

distance, in feet, each cross section is inundated. 

Hydraulic depths that occur below the P90

discharge generally are confined within the banks of

the channel, except at a limited number of cross

sections in low-lying areas. Mean hydraulic depths

range from approximately 1.5 to 5.5 ft and maximum

depths ranged from 2.5 to 11 ft (app. J). A large difference in hydraulic depth occurs in the transition

between channel and floodplain, because of the

increase in cross-sectional area. This difference is illustrated in example cross section 292, where the hydraulic depth for the P90 discharge (3.9 ft) is largely

confined to the channel (fig. 14b). However, when the

large cross-sectional area of the floodplain is included

during the P98 discharge, a hydraulic depth of 1.3 ft is

calculated.

Total area of inundation within the channel and

floodplain ranged from 225 (P10) to 6,065 (P99.9) acres

(fig. 20 and app. K). Inundated area below the P90

discharge generally was confined to the channel (fig. 19).

Table 3. Cross sections, drainage area, and percentile discharges used in step-backwater analysis 

based on the concurrent period 1940-98 at the Peace River at the Arcadia, Zolfo Springs, and 

Bartow gages

[ft3/s, cubic feet per second; mi2, square miles]

Crosssection

range

Drainage 

area

(mi2)

Discharge (ft3/s)

P10 P50 P70 P80 P90 P98 P99.5 P99.9

1148-174 1,367 130 481 1,009 1,549 2,747 6,160 11,920 15,950

176-210 1,302 127 463 960 1,464 2,591 5,826 11,170 15,149

212-284 960 112 367 699 1,030 1,768 4,069 7,224 10,936

2286-321 826 106 329 597 860 1,446 3,380 5,678 9,285

322-339 791 99 312 568 819 1,379 3,211 5,378 8,777

340-380 730 87 281 517 747 1,261 2,916 4,856 7,890

382-390 583 58 208 394 574 979 2,206 3,598 5,754

391-406 542 50 187 360 525 900 2,008 3,247 5,159

3406-446 465 35 148 296 434 752 1,636 2,588 4,040

448-490 434 29 133 270 398 693 1,487 2,323 3,589

492-4500 390 20 111 233 346 608 1,274 1,946 2,950

1Arcadia gage upstream from SR 70 bridge.

2Zolfo Springs gage at US Highway 17 bridge.

3Fort Meade gage at US Highway 98 bridge.

4Bartow gage at SR 60.
20 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

Table 4. Approximate number of days daily mean discharge 

equaled or exceeded the selected percentile discharges at 

Peace River at Arcadia, 1940-98 

[P10, 10-percentile discharge; -- no days]

Year

Number of days

P10 P50 P70 P80 P90 P98 P99.5 P99.9

1940 350 221 131 86 28 -- -- --

1941 309 205 118 64 33 -- -- --

1942 365 248 151 98 50 8 -- --

1943 287 109 98 94 83 5 -- --

1944 307 107 75 37 14 -- -- --

1945 260 128 109 101 82 27 -- --

1946 329 161 106 74 41 -- -- --

1947 365 244 163 142 123 25 9 5

1948 359 269 184 116 62 12 5 2

1949 314 153 126 90 63 31 10 4

1950 318 86 38 25 19 9 -- --

1951 354 183 130 77 32 -- -- --

1952 366 178 62 26 8 3 -- --

1953 363 291 207 151 112 40 -- --

1954 365 323 206 158 101 27 -- --

1955 329 144 68 40 18 -- -- --

1956 299 56 32 17 8 -- -- --

1957 365 259 199 133 64 -- -- --

1958 365 284 182 107 69 4 -- --

1959 365 283 184 145 124 37 -- --

1960 366 308 218 157 100 35 12 7

1961 365 200 72 43 26 9 -- --

1962 260 118 86 64 32 10 -- --

1963 358 187 101 60 27 -- -- --

1964 366 220 128 67 24 -- -- --

1965 325 138 87 56 45 -- -- --

1966 360 224 169 88 49 3 -- --

1967 314 125 84 46 24 -- -- --

1968 334 140 110 89 66 6 -- --

1969 365 205 121 68 38 -- -- --

1970 365 314 217 114 43 -- -- --

1971 336 92 63 28 14 4 -- --

1972 366 130 75 25 5 -- --

1973 359 170 128 90 32 -- -- --

1974 294 116 91 68 46 15 -- --

1975 281 94 55 28 7 -- -- --

1976 311 159 119 60 25 -- -- --

1977 290 86 33 8 5 -- -- --

1978 356 203 112 73 38 5 -- --

1979 336 170 94 62 27 1 -- --

1980 366 151 62 29 16 6 -- --

1981 216 47 27 15 2 -- -- --

1982 234 139 114 97 60 14 6 2

1983 365 252 179 122 78 -- -- --

1984 345 175 91 34 1 -- -- --

1985 123 60 34 13 4 -- -- --

1986 305 125 62 17 4 -- -- --

1987 347 148 74 40 16 -- -- --

1988 345 196 125 74 34 10 -- --

1989 316 88 13 -- -- -- -- --

1990 316 100 34 11 -- -- -- --

1991 281 127 89 73 37 -- -- --

1992 285 110 83 58 31 -- -- --

1993 365 169 96 38 12 -- -- --

1994 315 146 80 62 37 13 -- --

1995 353 296 182 113 82 18 -- --

1996 366 224 88 48 21 -- -- --

1997 239 98 52 34 13 -- -- --

1998 329 243 180 157 129 33 4 3

Mean 

number 

days

326 173 108 71 42 15 7 4

Table 4. Approximate number of days daily mean discharge 

equaled or exceeded the selected percentile discharges at 

Peace River at Arcadia, 1940-98 (Continued)

[P10, 10-percentile discharge; -- no days]

Year

Number of days

P10 P50 P70 P80 P90 P98 P99.5 P99.9
Peace River 21

EXPLANATION

CROSS SECTION--

 With number

216

GAGING STATION--

 With number

Peace

River

Ch arlie

Creek

279

278

276 02295637

274

272

270

268

266

262

264

260

258

256

254 252

250

248

246

Railroad

242

240 238

234

230

228

224

220

216

212

210

208

206

204

202

200

196

194

189

186 184

182

180

178

174 176

173

172

170

168

166

164 160

154

151150

148

02296750

158

156

152

232

236

244

282 291

Arcadia

Zolfo

Springs

02296750

81°52′30′′ 81°47′30′′

17

27°30′

27°25′

27°20′

27°15′

81°50′

64

70

Base from Florida Highway Department

County Highway Maps 1:63,360

0 2 MILES

0 2 KILOMETERS

The difference in inundated area between the P10 (225

acres) and P90 (1,118 acres) discharges, which were

confined largely to within the channel, was approximately 900 acres. In contrast, the area of inundation

between the P90 (1,118 acres) and P99.9 (6,065 acres)

discharges was approximately 5,000 acres, reflecting

inundation changes solely within the floodplain. The

greatest increase in inundated area occurred between

the P90 to P98 discharges and between the P98 to P99.5

discharges, with 1,964 and 1,810 acres, respectively.

The loss of inundated area between the existing

step-backwater analysis and the potential step-backwater analysis ranged from 5.6 (P10) to 373 (P98) acres,

which corresponds to a decrease in inundated area of

2.0 and 17.7 percent, respectively (fig. 20 and app. L).

Decrease in inundated area at or below the P80-10

discharge generally occurred within the channel, and

ranged from 5.6 to 45.8 acres. The greatest decrease in

inundated area was 373 acres at the P98-10 discharge

(fig. 21a-h).

Reach 3–Fort Meade to Bartow

Channel characteristics along the 13.9-mi reach

from Fort Meade to Bartow vary greatly (fig. 22). The

channel is deeply incised in one part of the reach and

poorly defined in another. Numerous sinkholes, located

in the channel and floodplain, divert streamflow and

recharge underlying aquifers. Elevated reclaimed phosphate-mined landforms define the outer boundary

along much of the floodplain corridor. Although widespread floodplain inundation can occur at moderate-tohigh-discharge conditions, the extent is confined generally to within the corridor by adjacent reclaimed landforms. Daily mean discharge at the Peace River at

Bartow gage during the study period (1940-98) ranged

from 1.2 to 4,100 ft3/s, with a median discharge of

111 ft3/s (P50).

Water-surface profiles were based on elevations

computed at the 60 cross sections along reach 3 for

each of the eight selected percentile discharges. Extent

of areal inundation, acreage of inundation, and hydraulic depth were also computed based on the results of

the water-surface elevations (fig. 23). Of the eight

selected percentile discharges studied, the channel

mostly confined only the P10 discharge (35 ft3/s). Widespread inundation of the floodplain occurs at the P50

discharge in most areas, based on the Bartow (111 ft3/s)

and Fort Meade (148 ft3/s) gaging stations, because the

poorly incised channel cannot confine the streamflow

Figure 11. Location of reach 1 and channel cross sections 

along the Peace River from Arcadia to Zolfo Springs, westcentral Florida. (Location of study area shown on figures 1 

and 10).
22 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

DISTANCE UPSTREAM FROM MOUTH, IN FEET

ELEVATION, IN FEET ABOVE NGVD OF 1929

180,000 200,000 220,000 240,000 260,000 280,000 300,000 320,000 340,000 360,000 380,000

0

10

20

30

40

50

60

Peace River Channel

Arcadia

Reach 1 Arcadia to Zolfo Springs Railroad Bridge Brownville Road Bridge

SR 64 Bridge

Zolfo Springs

Solid lines indicate percentile discharge profile

Maximum Elevation

 of Bridge Opening

Dashed lines indicate 10-percent discharge withdrawal

US 17 Bridge

148

152

154

156

158

164

166

168

170

172

173

174

176

178

180

182

184

186

188

196

198

200

202

204

206

208

210

212

214

216

218

220

222

224

228

230

232

236

238

242

244

246

248

250

252

254

258

260

262

264

266

268

270

272274

276

278

282

286

291

Cross Section Number

Land-Surface Elevation

P99.9

P99.5

P98

P90

P80

P70

P50

P10

P98-10

P90-10

P70-10

P50-10

P10-10

P99.5-10

P99.9-10

P80-10

within its banks. Maximum extent of floodplain inundation is 4,552 ft (cross section 492) during P99.9

discharge (fig. 24 and app. M). The mean inundation

width for the 60 cross sections along reach 3 can range

from approximately 104 ft (P10) to 1,953 ft (P99.9). The

inundated width of 104 ft may approximate the width

of a bankfull channel. The largest increase in extent of

mean inundation between percentiles is over 300 ft.

This increase occurs both between the P10 (104 ft) to

the P50 (424 ft) discharge and between the P50 (424 ft)

to the P70 (819 ft) discharge (app. M). A comparison of

the maximum extent of areal inundation for the

selected percentile discharges at each cross section is

shown in figure 24. However, the figure does not indicated the existence of elevated land surface along the

cross section that may be completely inundated during

high-flow periods or may form islands during low-flow

periods, thus reducing the actual distance inundated.

Appendix M presents the actual distance, in feet, each

cross section is inundated. 

Example cross section 480 shows that areal inundation of the floodplain is widespread for all percentile

discharges greater than the P10 discharge (fig. 14c).

An abrupt rise in land-surface elevation exists along

Figure 12. Water-surface profiles along reach 1 of the Peace River for existing conditions and a potential 10-percent discharge 

withdrawal.
Peace River 23

0

0 500 1,000 1,500 METERS

2,500 5,000 FEET

291 290

284

278

274

272

270

266

264

262

260

258

256

252

250

248

246

244

242

240

236

232

230

228

226

222

220

218

216

214

212

210

208

206

204

202

200

198

196

191

186

184

182

180

178

176

174

173

172

168

166

148

158

156

154

152

150

164 162

224

238

254

268

276

292

151

160

Arcadia

Railroad Bridge

Brownville Road Bridge

SR 64 Bridge

CROSS SECTION

Peace River Channel

LIMIT OF STUDY

FLOOD PLAIN BOUNDARY

Peace River-Reach 1

Arcadia to Zolfo Springs

Flow

Zolfo Springs

US 17 Bridge

P99.9

P99.5

P98

P90

P80

P70

P50

EXPLANATION

P10

Percentile

Discharges

CROSS SECTION NUMBER

Figure 13. Extent of areal inundation along reach 1 of the Peace River channel and floodplain for 

selected percentile discharges.
24 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida ELEVATION, IN FEET ABOVE NGVD OF 1929

DISTANCE FROM LEFT BANK, IN FEET

0 1,000 2,000 3,000 4,000 5,000 6,000 30

35

40

45

50

55

60

65

70

Peace River Channel

P99.9, 6.0 ft

P98, 1.3 ft

P90, 3.9 ft

P80, 3.2 ft

P50, 1.6 ft

P70, 2.5 ft

P10, 0.9 ft

10

20

30

40

50

60

P99.9, 5.7 ft

Cross Section 208

Peace River Channel

P99.5, 4.4 ft

P98, 2.4 ft

P90, 10.2 ft

P80, 8.0 ft

P50, 4.1 ft

P70, 6.4 ft

0 2,000 4,000 6,000 8,000 10,000

P10, 1.6 ft

0 200 400 600 800 1,000 1,200 1,400

85

90

95

100

105

110

Cross Section 292

P99.5, 3.8 ft

Reach 1-Peace River

Reach 2- Peace River

Reach 3-Peace River

P99.9, 5.6 ft

P99.5, 4.3 ft

P98, 3.3 ft

P90, 2.0 ft

P80, 1.2 ft

P50, 1.7 ft P70, 1.1 ft

P10, 1.6 ft

Cross Section 480

Peace River Channel

(c)

(b)

(a)

 Percentile Mean Number Occurrence 

 Days/Year (Years) 

 P99.9 4 6 

 P99.5 7 6

 P98 15 27

 P90 42 57

 P80 71 58

 P70 108 59

 P50 173 59

 P10 326 59

Looking Downstream

Looking Downstream

Looking Downstream EXPLANATION

P99.9 Percentile Discharge 

5.7 ft Hydraulic Depth

P99.9 Percentile Discharge 

6.0 ft Hydraulic Depth

EXPLANATION

P99.9 Percentile Discharge 

5.6 ft Hydraulic Depth

EXPLANATION

Land-surface Elevation

Figure 14. Estimated extent and frequency of areal inundation and hydraulic depth for Peace River 

cross sections along reaches 1, 2, and 3 for each of the selected percentile discharges.
Peace River 25

TOTAL INUNDATED AREA, IN ACRES

Peace River-Reach 1 Arcadia to Zolfo Springs

Total number of acres inundated

Total number of acres inundated

after 10-percent flow reduction

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

PERCENTILE DISCHARGE

10 50 70 80 90 98 99.5 99.9 th th th th th th th th

Lines indicate interpolated inundated area

Percent inundated

1.3 % area decreased 3.0 % 4.6 %

12.6 %

14.2 %

17.8 %

5.0 %

4.2 %

much of the floodplain boundary, which limits the

extent of areal inundation during high flows in some

areas. This change in topography is the result of

elevated reclaimed phosphate-mined landforms

constructed along the floodplain corridor boundary. 

Hydraulic depths that occur at or below the P10

discharge generally are confined to the channel. Mean

hydraulic depths ranged from 1.5 to 4.6 ft, and maximum depths ranged from 2.5 to 7.2 ft (app. N). Difference in mean hydraulic depth between successive

percentile discharges is less than 1 ft. Example cross

section 480 shows the mean number of days per year

that a particular hydraulic depth could occur for an

expected percentile discharge (fig. 14c). Because the

channel generally is poorly incised, the maximum

hydraulic depth for reach 3 is 7.2 ft, which is much less

than the mean hydraulic depths for reach 1 or reach 2,

which are 12 ft (app. F) and 11 ft (app. J), respectively. 

Total inundated area within the channel and

floodplain ranged from 173 (P10) to 2,828 (P99.9) acres

(fig. 25 and app. O). Inundated area at or below the P10

discharge generally was confined within the channel at

most cross sections (fig. 24). The greatest increase in

inundated area was from the P10 to the P50 discharges

with 571 acres, which occurred during the transition

from channel to floodplain inundation.

Loss of inundated area between the existing stepbackwater analysis and the potential step-backwater

analysis, ranged from 6.5 (P10) to 99.3 (P98) acres,

which corresponds to an approximate 4.0 and 1.1

percent decrease of inundated area, respectively (fig. 25

and app. P). However, the greatest percentage decrease

of inundated area occurred at the P50-10 discharge

with 12.0 percent. The decrease of inundated area at

the P10-10 discharge generally occurred within the channel and was 6.5 acres. The greatest decrease in inundated area was 94.9 and 99.3 acres, which occurred at

the P50-10 and P99.9-10 discharges, respectively (fig. 26a-h

and app. P). Decreases associated with the P50-10

discharge occur frequently, because the P50 discharge

averages approximately 173 days per year (table 4).

Whereas, the P99.9-10 discharge occurs rarely, approximately once every 10 yrs for an average of 4 days.

Decrease of inundated area at the P70, P80, P90, P98, and

P99.5 discharges were similar, and ranged from 48.1 to

76.7 acres, with a mean decrease of 61.6 acres (app. P).

Figure 15. Estimated total inundated area along reach 1 of the Peace River for existing conditions and for a 

potential 10-percent discharge withdrawal, and percentage of inundated area decreased by a potential 10-percent 

discharge withdrawal for each of the selected percentile discharges.
26 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

291 290

284

278

274

272

270

266

264

262

260

258

256

252

250

248

246

244

242

240

236

232

230

228

226

222 220

218

216

214

212

210

208

206

204

202

200

198

196

191

186

184

182

180

178

176

174

173

172

170

168

166

148

158

156

154

152

150

164 162

224

238

254

268

276

292

151

160

291

290

284

278

274

272

270

266

264

262

260

258

256

252

250

248

246

244

242

240

236

232

230

228

226

222 220

218

216

214

212

210

208

206

204

202

200

198

196

191

186

184

182

180

178

176

174

173

172

170

168

166

148

158

156

154

152

150

164 162

224

238

254

268

276

292

151

160

Arcadia Gaging Station

Railroad Bridge

Brownville Road

Bridge

SR 64 Bridge

Zolfo Springs Gaging Station

at US Highway 17 Bridge

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

CROSS SECTION

Peace River Channel

Peace River-Reach 1 Arcadia to Zolfo SpringsFlow

(a)

CROSS SECTION NUMBER

P P 10-10 50-10 (a) and (b)

P P 10 50 (a) and (b)

EXPLANATION

(b)

0

0 500 1,000 1,500 METERS

P 2,500 5,000 FEET 10 P50

Figure 16. Extent of areal inundation along reach 1 of the Peace River channel and floodplain for the (a) P10, 

(b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions and a 

potential 10-percent discharge withdrawal.
Peace River 27

291

290

284

278

274

272

270

266

264

262

260

258

256

252

250

248

246

244

242

240

236

232

230

228

226

222 220

218

216

214

212

210

208

206

204

202

200

198

196

191

186

184

182

180

178

176

174

173

172

170

168

166

148

158

156

154

152

150

164 162

224

238

254

268

276

292

151

160

291 290

284

278

274

272

270

266

264

262

260

258

256

252

250

248

246

244

242

240

236

232

230

228

226

222 220

218

216

214

212

210

208

206

204

202

200

198

196

191

186

184

182

180

178

176

174

173

172

170

168

166

148

158

156

154

152

150

164 162

224

238

254

268

276

292

151

160

P70 P80

Arcadia Gaging Station

Railroad Bridge

Brownville Road

Bridge

SR 64 Bridge

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

Zolfo Springs Gaging Station

at US Highway 17 Bridge

CROSS SECTION

Peace River Channel Flow

Peace River-Reach 1 Arcadia to Zolfo Springs

(c) (d)

CROSS SECTION NUMBER

P P 70-10 80-10 (c) and (d)

 P P 70 80 (c) and (d)

EXPLANATION

0

0 500 1,000 1,500 METERS

2,500 5,000 FEET

Figure 16. Extent of areal inundation along reach 1 of the Peace River channel and floodplain for the (a) P10, 

(b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions and a 

potential 10-percent discharge withdrawal. (Continued)
28 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

291 290

284

278

274

272

270

266

264

262

260

258

256

252

250

248

246

244

242

240

236

232

230

228

226

222 220

218

216

214

212

210

208

206

204

202

200

198

196

191

186

184

182

180

178

176

174

173

172

170

168

166

148

158

156

154

152

150

164 162

224

238

254

268

276

292

151

160

291

290

284

278

274

272

270

266

264

262

260

258

256

252

250

248

246

244

242

240

236

232

230

228

226

222 220

218

216

214

212

210

208

206

204

202

200

198

196

191

186

184

182

180

178

176

174

173

172

170

168

166

148

158

156

154

152

150

164 162

224

238

254

268

276

292

151

160

Arcadia Gaging Station

Railroad Bridge

Brownville Road

Bridge

SR 64 Bridge

Zolfo Springs Gaging Station

at US Highway 17 Bridge

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

CROSS SECTION

Peace River Channel Flow

Peace River-Reach 1 Arcadia to Zolfo Spring

(e) (f)

CROSS SECTION NUMBER

P P 90-10 98-10 (e) and (f)

 P P 90 98 (e) and (f)

EXPLANATION

0

0 500 1,000 1,500 METERS

2,500 5,000 FEET

P90 P98

Figure 16. Extent of areal inundation along reach 1 of the Peace River channel and floodplain for the (a) P10, 

(b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions and a 

potential 10-percent discharge withdrawal. (Continued)
Peace River 29

291 290

284

278

274

272

270

266

264

262

260

258

256

252

250

248

246

244

242

240

236

232

230

228

226

222 220

218

216

214

212

210

208

206

204

202

200

198

196

191

186

184

182

180

178

176

174

173

172

170

168

166

148

158

156

154

152

150

164 162

224

238

254

268

276

292

151

160

291 290

284

278

274

272

270

266

264

262

260

258

256

252

250

248

246

244

242

240

236

232

230

228

226

222 220

218

216

214

212

210

208

206

204

202

200

198

196

191

186

184

182

180

178

176

174

173

172

170

168

166

148

158

156

154

152

150

164 162

224

238

254

268

276

292

151

160

P99.5 P99.9 Arcadia Gaging Station

Railroad Bridge

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

Brownville Road

 Bridge

SR 64 Bridge

Zolfo Springs Gaging Station

at US Highway 17 Bridge

CROSS SECTION

Peace River Channel Flow

Peace River-Reach 1 Arcadia to Zolfo Springs

(g) (h)

CROSS SECTION NUMBER

P P 99.5-10 99.9-10 (g) and (h)

 P P 99.5 99.9 (g) and (h)

EXPLANATION

0

0 500 1,000 1,500 METERS

2,500 5,000 FEET

Figure 16. Extent of areal inundation along reach 1 of the Peace River channel and floodplain for the (a) P10, 

(b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions and a 

potential 10-percent discharge withdrawal. (Continued)
30 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

17

630

17



Base from Florida Highway Department

County Highway Maps 1:63,360

0 2 MILES

0 2 KILOMETERS

81°47′30′′

27°40′

27°35′

27°30′

81°50′

U.S. 98 405

406

404

400

398

396

402

496

490 388

386

380

384

378

376

372 374

370

368

366

364

362

360

354

358

352

350

346

344

342

339

340

338 336

334

332

330

328

326

322

321 318

314

310

308

306

304 305

302

300

298

296

294 292

291

286

284

282

Zolfo

Springs

Wauchula

Bowling

Green

Fort

Meade

02295637

Bowlegs Creek

Payne Creek

02294898

EXPLANATION

CROSS SECTION--

 With number

GAGING STATION --

 With number

336

02295637

Figure 17. Location of reach 2 and cross sections along the Peace 

River from Zolfo Springs to Fort Meade, west-central Florida. 

(Location of study area shown in figures 1 and 10).
Peace River 31

807060504030

340,000 360,000 380,000 400,000 420,000 440,000 460,000 480,000 500,000

287

291

294

296

298

300

302

304

308

310

314

316

318

320

321

326

327.5

330

332

334

336

337

339

340

342

346

350

352

354

358

360

362

364

366

368

370

372

374

376

378

380

382

386

388

390

391

396

398

400

402

404

405

406.2

84

ELEVATION, IN FEET ABOVE NGVD OF 1929

DISTANCE UPSTREAM FROM MOUTH, IN FEET

Reach 2 Zolfo Springs to Fort Meade

Peace River Channel

Zolfo Springs Gaging Station

 US 17 Bridge

SR 652 Bridge

 Wauchula

SR 64A Bridge

 Wauchula

SR 664A Bridge

 Wauchula

SR 664 Bridge

Bowling Green

SR 664 Bridge at Polk-

 Hardee Countyline

SR 657 Bridge

 Fort Meade

 US 98 Bridge

Fort Meade Gaging Station

Maximum Elevation of Bridge Opening

Solid lines indicate percentile discharge profileDashed lines indicate potential 10-percent discharge withdrawal

P99.9P99.5

P98P90P80P70P50P10

P98-10P90-10P70-10P50-10

P10-10

P99.5-10P99.9-10

P80-10

Figure 18. Water-surface profiles along reach 2 of the Peace River for existing conditions and a potential 10-percent discharge withdrawal.
32 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

0 2,000 4,000 FEET

0 500 1,000 METERS

CROSS SECTION

Peace River Channel

LIMIT OF STUDY

FLOODPLAIN BOUNDARY Flow

Zolfo Springs

US 17 Bridge

Fort Meade

US 98 Bridge

338

340

341

344

348

350

352

354

358

360

362

364

366

368

370

372

374

376

378

380

382

384

386

388

390

391

396

398

400

402

404

405

406.2

286

294

296

298

300

302

304

306

310

314

316

318

320

321

324

326

327.5

330

332

334

336

337

SR 664 Bridge at Polk-Hardee County line

SR 657 Bridge

SR 652 Bridge at Wauchula

SR 64A Bridge at Wauchula

SR 664A Bridge above Wauchula

Peace River-Reach 2

Zolfo Springs to Fort Meade

CROSS SECTION NUMBER

P99.9

P99.5

P98

P90

P80

P70

P50

EXPLANATION

P10

Percentile

Discharges

Figure 19. Areal inundation along reach 2 of the Peace River channel and floodplain for selected 

percentile discharges.
Alafia River System 33

TOTAL INUNDATED AREA, IN ACRES

Area inundated after a10-percent

discharge withdrawal

Area inundated

Peace River-Reach 2 Zolfo Springs to Fort Meade

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

5,500

6,000

6,500

10 50 70 80 90 98 99.5 99.9

PERCENTILE DISCHARGE

th th th th th th th th

Lines indicate interpolated inundated area

2.0 % 3.6 % 8.4 % 8.2 %

17.7 %

12.1 %

6.0 %

2.7 %

Percent inundated

area decreased

Inundated Area and Effects of Potential 

Discharge Withdrawals Along the Three 

Peace River Reaches

Combined area of total inundation for the three

reaches of the Peace River, from Arcadia to Bartow,

ranged from 775 (P10 discharge) to 26,089 (P99.9

discharge) acres (fig. 27). The number of inundated

acres for each of the reaches is based on differing reach

lengths and their channel and floodplain configuration.

Areal inundation along reaches 1 and 2, which share

similar characteristics, is generally proportional to their

channel lengths, 32.2 and 23.6 mi, respectively.

However, reach 3 (13.9 mi), which is only 20 percent

of the study channel length, has proportionally higher

total areal inundation for most percentile discharges,

especially the P50, P70, P80, and P90 discharges. Because

of a poorly incised channel along much of reach 3,

areal inundation for the P10 discharge was small. Total

decrease of inundated area along the Peace River from

a potential 10-percent discharge withdrawal, based on

the selected percentile discharges, ranged from about

17.1 (P10 discharge) to 1,891 (P98 discharge) acres,

which corresponds to an approximate 2.1 and 13.6

percent decrease of inundated area, respectively.

ALAFIA RIVER SYSTEM

The Alafia River System is defined in this report

as the Alafia, North Prong Alafia, and South Prong

Alafia Rivers. The Alafia River System drains an

approximate 420 mi2 area of southwestern Polk County

and southeastern Hillsborough County (figs. 1 and 28).

The two principal tributaries, the North and South

Prong Alafia Rivers, join together at the confluence

with the Alafia River to form the headwaters.

Alafia River

The Alafia River channel meanders westward for

approximately 23 mi, from the confluence with its two

tributaries to the mouth. The approximately 335-mi2

area of the upper Alafia River watershed is drained

at the Lithia gage (02301500) at SR 640. Streamflow

data have been collected continuously by the USGS

at the Lithia gage since 1932. Extremes in daily

mean discharge at the gage ranged from 6.6 (1945) to

40,800 ft3/s (1933). The Alafia River downstream

of the Lithia gage is affected by tidally influenced

backwater.

Figure 20. Estimated total inundated area along reach 2 of the Peace River for existing conditions and for 

a potential 10-percent discharge withdrawal, and percentage of inundated area decreased by a potential 

10-percent discharge withdrawal for each of the selected percentile discharges.
34 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

Peace River-Reach 2 Zolfo Springs to Fort Meade

P10

338

340

341

344

348

350

352

354

358

360

362

364

366

368

370

372

374

376

378

380

382

384

386

388

390

391

396

398

400

402

404

405

406.2

286

294

296

298

300

302

304

306

310

314

316

318

320

321

324

326

327.5

330

332

334

336

337

292

P50

338

340

341

344

348

350

352

354

358

360

362

364

366

368

370

372

374

376

378

380

382

384

386

388

390

391

396

398

400

402

404

405

406.2

286

294

296

298

300

302

304

306

310

314

316

318

320

321

324

326

327.5

330

332

334

336

337

292

SR 664 Bridge at PolkHardee County Line

SR657 Bridge at Fort Meade

Fort Meade Gaging Station

at US Highway 98 Bridge

Zolfo Springs Gaging Station

at US Highway 17 Bridge

SR 652 Bridge at Wauchula

SR 64A Bridge at

Wauchula

SR664A Bridge

above Wauchula

CROSS SECTION

Peace River Channel

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

Flow

(a) (b)

CROSS SECTION 

NUMBER

P P 10-10 50-10 (a) and (b)

 P P 10 50 (a) and (b)

EXPLANATION

0 2,000 4,000 FEET

0 500 1,000 METERS

Figure 21. Extent of areal inundation along reach 2 of the Peace River channel and floodplain for the 

(a) P10, (b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions 

and a potential 10-percent discharge withdrawal. 
Alafia River System 35

P80

338

340

341

344

348

350

352

354

358

360

362

364

366

368

370

372

374

376

378

380

382

384

386

388

390

391

396

398

400

402

404

405

406.2

286

294

296

298

300

302

304

306

310

314

316

318

320

321

324

326

327.5

330

332

334

336

337

292

P70

338

340

341

344

348

350

352

354

358

360

362

364

366

368

370

372

374

376

378

380

382

384

386

388

390

391

396

398

400

402

404

405

406.2

286

294

296

298

300

302

304

306

310

314

316

318

320

321

324

326

327.5

330

332

334

336

337

292

SR 664 Bridge at PolkHardee County Line

SR657 Bridge at Fort Meade

Fort Meade Gaging Station

at US Highway 98 Bridge

Zolfo Springs Gaging Station

at US Highway 17 Bridge

SR 652 Bridge at Wauchula

SR 64A Bridge at Wauchula

SR664A Bridge

above Wauchula

CROSS SECTION

Peace River Channel

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

Flow

(c) (d)

Peace River-Reach 2 Zolfo Springs to Fort Meade

CROSS SECTION 

NUMBER

P P 70-10 80-10 (c) and (d)

 P P 70 80 (c) and (d)

EXPLANATION

0 2,000 4,000 FEET

0 500 1,000 METERS

Figure 21. Extent of areal inundation along reach 2 of the Peace River channel and floodplain for the 

(a) P10, (b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions 

and a potential 10-percent discharge withdrawal. (Continued)
36 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

Figure 21. Extent of areal inundation along reach 2 of the Peace River channel and floodplain for the 

(a) P10, (b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions 

and a potential 10-percent discharge withdrawal. (Continued)

P98

338

340

341

344

348

350

352

354

358

360

362

364

366

368

370

372

374

376

378

380

382

384

386

388

390

391

396

398

400

402

404

405

406.2

286

294

296

298

300

302

304

306

310

314

316

318

320

321

324

326

327.5

330

332

334

336

337

292

P90

338

340

341

344

348

350

352

354

358

360

362

364

366

368

370

372

374

376

378

380

382

384

386

388

390

391

396

398

400

402

404

405

406.2

286

294

296

298

300

302

304

306

310

314

316

318

320

321

324

326

327.5

330

332

334

336

337

292

SR 664 Bridge at PolkHardee County Line

SR657 Bridge at Fort Meade

Fort Meade Gaging Station

at US Highway 98 Bridge

Zolfo Springs Gaging Station

at US Highway 17 Bridges

SR 652 Bridge at Wauchula

SR 64A Bridge at

Wauchula

SR664A Bridge

above Wauchula

CROSS SECTION

Peace River Channel

LIMIT OF STUDY

FLOODPLAIN 

BOUNDARY

Flow

SR664 Bridge below

Bowling Green

(f)

Peace River-Reach 2 Zolfo Springs to Fort Meade

CROSS SECTION 

NUMBER

(e)

P P 90-10 98-10 (e) and (f)

 P P 90 98 (e) and (f)

EXPLANATION

0 2,000 4,000 FEET

0 500 1,000 METERS
Alafia River System 37

P99.9

338

340

341

344

348

350

352

354

358

360

362

364

366

368

370

372

374

376

378

380

382

384

386

388

390

391

396

398

400

402

404

405

406.2

286

294

296

298

300

302

304

306

310

314

316

318

320

321

324

326

327.5

330

332

334

336

337

292

P99.5

338

340

341

344

348

350

352

354

358

360

362

364

366

368

370

372

374

376

378

380

382

384

386

388

390

391

396

398

400

402

404

405

406.2

286

294

296

298

300

302

304

306

310

314

316

318

320

321

324

326

327.5

330

332

334

336

337

292

SR 664 Bridge at PolkHardee County Line

SR657 Bridge at Fort Meade

Fort Meade Gaging Station

at US Highway 98 Bridge

Zolfo Springs Gaging Station

at US Highway 17 Bridge

SR 652 Bridge at Wauchula

SR 64A Bridge at

Wauchula

SR664A Bridge

above Wauchula

CROSS SECTION Flow

SR664 Bridge below

Bowling Green

(g) (h)

Peace River-Reach 2 Zolfo Springs to Fort Meade

CROSS SECTION NUMBER

P99.5-10 (g) and P99.9-10 (h)

 P99.5 (g) and P99.9 (h)

EXPLANATION

Peace River Channel

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

0 2,000 4,000 FEET

0 500 1,000 METERS

Figure 21. Extent of areal inundation along reach 2 of the Peace River channel and floodplain for the 

(a) P10, (b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions 

and a potential 10-percent discharge withdrawal. (Continued)
38 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

Peace

River

27°50′

27°45′

81°50′ 81°47′30′′

60

17

98

Base from Florida Highway Department

County Highway Maps 1:63,360

0 2 MILES

0 2 KILOMETERS

EXPLANATION

CROSS SECTION--

 With number

GAGING STATION--

 With number

466

02294650

Study Limits

500 496

490 488

486 481

476

472

467

Railroad

466

462

458

460

454

452 450

448

443

442

438

434 430

426

422

417

416

414 412

410

408

406

02294898

420

Bartow 02294650

Fort Meade

The Alafia River study reach extends from

SR 640 to the confluence with the North and South

Prongs Alafia River. The channel generally is deeply

incised and well defined, containing most low-tomoderate-discharge conditions (74.3 ft3/s at P10 to

601 ft3/s at P90) within the banks. The floodplain corridor width is relatively narrow and uniform along the

channel and is defined by high topographic relief at the

boundary.

Although generally well defined and deeply

incised, the channels along the Alafia, North Prong,

and South Prong Alafia Rivers study reaches are delineated on NWI maps as palustrine forested wetlands.

Most of the open-water channel of the Alafia River,

downstream of the study reach, is classified as riverine

wetlands. The floodplain corridor along the Alafia

River system is delineated as a palustrine forested

wetlands, bounded by uplands.

Step-backwater analysis was performed at 21

cross sections located along a 8.2-mi reach of the

Alafia River, from the Lithia gage at SR 640 to the

confluence with the North and South Prongs of the

Alafia River. Step-backwater analysis was not

performed downstream of the Lithia gage because of

tidally influenced backwater conditions. Cross sections

used for the Alafia River and tributaries were developed by Robertson (1978), except at bridge locations.

Step-backwater analysis was based on the selected

Figure 22. Location of reach 3 and study cross sections along the 

Peace River from Fort Meade to Bartow, west-central Florida. 

(Location of study area shown in figures 1 and 10).
Alafia River System 39

Cross Section Number

Land-Surface Elevation

P99.9P99.5

P98P90P80P70P50P10

P98-10P90-10P70-10P50-10

P10-10

P99.5-10P99.9-10

P80-10

95908580757065

105100

480,000 490,000 500,000 510,000 520,000 530,000 540,000 550,000 560,000

DISTANCE, UPSTREAM FROM MOUTH, IN FEET

ELEVATION, IN FEET ABOVE NGVD OF 1929

Reach 3-Fort Meade to Bartow

406.3

407

408

410

412

414

416

417

422

424

426

428

430

432

434

436

438

440

442

443

448

450

452

454

456

458

460

462

464

466

467

472

474

476

478

480

486

488

490

492

494 498

504

Fort Meade Gaging Station

US Highway 98

Phosphate

Mine Bridge

SR 640 Bridge at Homeland

Clear Springs

 Bridge

Gas Pipeline

Truss Bridge

Bartow Gaging Station

SR 60 Bridge

Maximum Elevation of Bridge Opening

Solid lines indicate percentile discharge profile Dashed lines indicate 10-percent discharge withdrawal

Peace River Channel

Figure 23. Water-surface profiles along reach 3 of the Peace River for existing conditions and a potential 10-percent discharge 

withdrawal.
40 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

0 2,000 4,000 FEET

0 500 1,000 METERS

Cross Section

US 98 Bridge

Fort Meade

422

424

426

428

430

432

434

436

438

440

442

443

448

450

452

454

480

486

492

494

498

504

460

490

456

458

462

464

466

467

472

474

476

478

406.3

407

408

410

412

414

416

417

488

Phosphate Mine Bridge

SR 640 Bridge

 at Homeland

Clear Springs Mine Bridge

Abandoned Mine Bridge

Bartow Gaging Station at SR 60 Bridge

Peace River Channel

Flow

Peace River-Reach 3

Fort Meade to Bartow

Bartow

CROSS SECTION NUMBER

P99.9

P99.5

P98

P90

P80

P70

P50

EXPLANATION

P10

Percentile Discharge

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

Figure 24. Extent of areal inundation along reach 3 of the Peace River channel and floodplain for 

selected percentile discharges.
Alafia River System 41

Total number of inundated acres after 10-percent discharge withdrawal

 Peace River-Reach 3 Fort Meade to Bartow

TOTAL INUNDATED AREA, IN ACRES

10 50 70 80 90 98 99.5 99.9

PERCENTILE DISCHARGE

th th th th th th th th

Lines indicated interpolated inundated area

Percent inundated area decreased

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

2,200

2,400

2,800

2,600

3,000

Total number of inundated acres

4.0 %

12.0 %

5.0 %

3.8 %

1.6 %

1.1 %

1.2 %

2.4 %

percentile discharges (P10, P50, P70, P80, P 90, P98, P99.5

and P99.9) for the concurrent long-term period, 1964-92,

at the Alafia River at Lithia, North Prong Alafia River

at Keysville, and South Prong Alafia River near Lithia

gages. The period of analysis included only concurrent

record through 1992, because the North Prong Alafia

River gage was temporarily discontinued during

1993-94. Proportionally reduced discharges were introduced at selected cross sections during the step-backwater analysis to compensate for the decrease in

contributing drainage area (table 5). The results of the

step-backwater analysis were considered reliable

because the computed water-surface profiles converged

within 0.5 ft of the stage-discharge relation at the North

and South Prong Alafia River gages. Water-surface

profiles, extent of areal inundation, and hydraulic depth

at the 21 Alafia River cross sections were based

on water-surface elevations computed during the

step-backwater analysis (fig. 29).

The number of days per year that a specific

percentile discharge occurred at Alafia River at Lithia

gage was variable. The P10, P50, P70, P80, and P90

discharges occurred every year, and ranged from 1

(P 90) to 366 (P10) days (table 6). During the 29-year

study period, however, the frequency that the P98

(19 years), P99.5 (16 years), and P 99.9 (4 years)

discharges actually occurred was limited. The mean

number of days the discharges occurred for the P98,

P99.5, and P 99.9 discharges were 8, 4, and 3 days,

respectively. 

Maximum extent of floodplain inundation

exceeds 3,300 ft (cross section 77) during P99.9

discharge (3,820 ft3/s) (fig. 30 and app. Q). Mean inundation width, based on the 21 cross sections, range

from 61 ft (P10) to 2,081 ft (P99.9). The incised channel

generally confines most discharges at or below the P90

discharge (601 ft3/s) (table 5). Mean inundation width

at the P90 discharge (132 ft) may approximate the bankfull channel width. A large increase in mean inundation

occurs in the transition from channel to floodplain

during the P90 (132 ft) to the P98 (942 ft) discharge. A

comparison of the maximum extent of areal inundation

for the selected percentile discharges at each cross

section is shown in figure 30. However, the figure does

not indicated the existence of elevated land surface

along the cross section that may be completely inundated during high-flow periods or may form islands

during low-flow periods, thus reducing the actual

distance inundated. Appendix Q presents the actual

distance, in feet, each cross section is inundated.

Figure 25. Estimated total inundated area along reach 3 of the Peace River for existing conditions and for a 

potential 10-percent discharge withdrawal, and percentage of inundated area decreased by a potential 10-percent 

discharge withdrawal for each of the selected percentile discharges.
42 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

P50

Peace River-Reach 3 Fort Meade to Bartow

(b)

450

422

424

426

428

430

432

434

436

438

440

442

443

448

452

454

480

486

492

494

498

504

460

490

456

458

462

464

466

467

472

474

476

478

406.3

407

408

410

412

414

416

417

488

P10

Fort Meade Gaging 

Station US Highway 98

Phosphate Mine

Bridge

SR 640 Bridge

at Homeland

Clear Springs Mine

Bridge at Bartow

Abandoned Mine

Bridge at Bartow

Bartow Gaging Station

SR 60 Bridge

CROSS SECTION

Peace River Channel

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

Flow

(a)

450

422

424

426

428

430

432

434

436

438

440

442

443

448

452

454

480

486

492

494

498

504

460

490

456

458

462

464

466

467

472

474

476

478

406.3

407

408

410

412

414

416

417

488

CROSS SECTION 

NUMBER

P P 10-10 50-10 (a) and (b)

 P P 10 50 (a) and (b)

EXPLANATION

0

0 500 1,000 METERS

2,000 4,000 FEET

Figure 26. Extent of areal inundation along reach 3 of the Peace River channel and floodplain for the (a) P10, 

(b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions and a 

potential 10-percent discharge withdrawal.
Alafia River System 43

422

424

426

428

430

432

434

436

438

440

442

443

448

450

452

454

480

486

492

494

498

504

460

490

456

458

462

464

466

467

472

474

476

478

406.3

407

408

410

412

414

416

417

488

P80

422

424

426

428

430

432

434

436

438

440

442

443

448

450

452

454

480

486

492

494

498

504

460

490

456

458

462

464

466

467

472

474

476

478

406.3

407

408

410

412

414

416

417

488

P70

Fort Meade Gaging 

Station US Highway 98

Phosphate Mine

Bridge

SR 640 Bridge

at Homeland

Clear Springs Mine

Bridge at Bartow

Abandoned Mine

Bridge at Bartow

Bartow Gaging Station

SR 60 Bridge

CROSS SECTION

Peace River Channel

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

Flow

Peace River-Reach 3 Fort Meade to Bartow

(c) (d)

CROSS SECTION

 NUMBER

P P 70-10 80-10 (c) and (d)

 P P 70 80 (c) and (d)

EXPLANATION

0

0 500 1,000 METERS

2,000 4,000 FEET

Figure 26. Extent of areal inundation along reach 3 of the Peace River channel and floodplain for the (a) P10, 

(b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions and a 

potential 10-percent discharge withdrawal. (Continued)
44 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

422

424

426

428

430

432

434

436

438

440

442

443

448

450

452

454

480

486

492

494

498

504

460

490

456

458

462

464

466

467

472

474

476

478

406.3

407

408

410

412

414

416

417

488

P90

422

424

426

428

430

432

434

436

438

440

442

443

448

450

452

454

480

486

492

494

498

504

460

490

456

458

462

464

466

467

472

474

476

478

406.3

407

408

410

412

414

416

417

488

P98

Fort Meade Gaging 

Station US Highway 98

Phosphate Mine

Bridge

SR 640 Bridge

at Homeland

Clear Springs Mine

Bridge at Bartow

Abandoned Mine

Bridge at Bartow

Bartow Gaging Station

SR 60 Bridge

CROSS SECTIONFlow

Peace River-Reach 3 Fort Meade to Bartow

(e) (f)

CROSS SECTION 

NUMBER

P90-10 (e) and P98-10 (f)

P90 (e) and P98 (f)

EXPLANATION

Peace River Channel

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

0

0 500 1,000 METERS

2,000 4,000 FEET

Figure 26. Extent of areal inundation along reach 3 of the Peace River channel and floodplain for the (a) P10, 

(b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions and a 

potential 10-percent discharge withdrawal. (Continued)
Alafia River System 45

422

424

426

428

430

432

434

436

438

440

442

443

448

450

452

454

480

486

492

494

498

504

460

490

456

458

462

464

466

467

472

474

476

478

406.3

407

408

410

412

414

416

417

488

422

424

426

428

430

432

434

436

438

440

442

443

448

450

452

454

480

486

492

494

498

504

460

490

456

458

462

464

466

467

472

474

476

478

406.3

407

408

410

412

414

416

417

488

P99.5 P99.9

Fort Meade Gaging 

Station US Highway 98

Phosphate Mine

Bridge

SR 640 Bridge

at Homeland

Clear Springs Mine

Bridge at Bartow

Abandoned Mine

Bridge at Bartow

Bartow Gaging Station

SR 60 Bridge

CROSS SECTION

Peace River Channel

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

Flow

Peace River-Reach 3 Fort Meade to Bartow

(g) (h)

CROSS SECTION NUMBER

P P 99.5-10 99.9-10 (g) and (h)

 P P 99.5 99.9 (g) and (h)

EXPLANATION

0

0 500 1,000 METERS

2,000 4,000 FEET

Figure 26. Extent of areal inundation along reach 3 of the Peace River channel and floodplain for the (a) P10, 

(b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions and a 

potential 10-percent discharge withdrawal. (Continued)
46 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida TOTAL INUNDATED AREA, IN ACRES

PERCENTILE DISCHARGE

10 50 70 80 90 98 99.5 99.9

th th th th th th th th

Lines indicate interpoloated area

Total inundated area

Area inundated after a potential

10-percent discharge reduction

Percentage of inundated area

decreased by withdrawals

Peace River-Reaches 1, 2, and 3

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

20,000

22,000

24,000

26,000

28,000

7.8 % 2.1 %

6.1 %

3.2 %

10.8 %

13.6 %

2.2 %

3.4 %

Example cross section 79 shows that percentile

discharges at or below the P98 discharge (1,418 ft3/s)

are confined to the channel, and those above can inundate the floodplain (fig. 31a and table 5). At cross

section 79, the extent of inundation at the P99.5

discharge (2,417 ft3/s) was approximately 1,500 ft,

which occurred only 16 times during the 29-year study

period, for an average of 4 days each time. Because the

deeply incised channel contains most discharges, widespread inundation of the study reach floodplain may

occur for a few days about every other year.

Maximum hydraulic depths ranged from 3.4 to

9.2 ft, and mean depths ranged from 1.8 to 4.8 ft. The

hydraulic depth at the P90 discharge generally is

confined to the channel (app. R). Total inundated area

within the channel and floodplain ranged from 53 (P10)

to 1,445 (P99.9) acres (fig. 32 and app. S). Inundated

area below the P90 discharge (601 ft3/s) generally was

confined within the channel (fig. 30, and table 5). The

difference in inundated area from the P10 to the P90

discharges was approximately 50 acres, which largely

included the channel. However, the inundated area

from the P90 to the P98 discharges (577 acres) and from

the P98 to the P99.5 discharges (469 acres) largely

included the floodplain (app. S). 

Total inundated area along the Alafia River for

the period of streamflow record, 1964-92, was

compared to inundated area resulting from a 10-percent

discharge withdrawal. The decrease in inundated area

between the existing conditions step-backwater analysis and the potential withdrawal step-backwater analysis ranged from approximately 1 (P10) to 90 (P99.9)

acres, which approximate a 1.0 and 4.0 percent

decrease of inundated area, respectively (fig. 32 and

app. T). However, the greatest percentage decrease of

inundated area occurred at the P90-10 discharge with

19.6 percent. A decrease in inundated area at or below

the P90-10 discharge generally occurred within the channel and ranged from 0.7 to 20.6 acres (fig. 33a-h). The

greatest decrease of inundated area occurred at the

P99.9-10 discharge with 89.5 acres (app. T). 

Figure 27. Estimated total inundated area along the three reaches of the Peace River for existing conditions and for a 

potential 10-percent discharge withdrawal, and percentage of inundated area decreased by a potential 10-percent 

discharge withdrawal for each of the selected percentile discharges.
Alafia River System 47

0

0

1

1

2 MILES

2 KILOMETERS

Railroad

South 

Prong

Prong

North

Alafia

River

82°10′ 82°05′

676

676

640

39

Jameson Road

11 CROSS SECTION-- Location 

 and identification number

94 CROSS SECTION-- At bridge

BRIDGE

EXPLANATION

 GAGING STATION-- With site number

South Prong

Alafia River

near Lithia, Florida

North Prong 

Alafia River At

Keysville, Florida

Alafia At 

Lithia, Florida

27°55′

27°50′

confluence

02301000

02301300

76 77

78

79 80

82

81

85 87

88

89

91

92

93

7

and 7.5

1

1

2

2 3

3

4

4

5

7

8

9 10

13

18

19 17

20

21

22

23

14

12

16.5 

5

6

8

and 9

90

96 94

and 95

86

83

and 84 74

and 75

10

11

12

13

14

15

16

17

18

19

20

21

22

27

25 26

28

29

23

and 24

73

02301500

Florida

Base from Florida Highway Department

County Highway Maps 1:63,360

North Prong Alafia River

The North Prong Alafia River, a major tributary

to the Alafia River, drains approximately 140 mi2. The

river flows in a southwesterly direction along an

approximate 9.5-mi-long study reach, from cross

section 23 to the confluence with the Alafia and South

Prong Alafia Rivers (figs. 1 and 28). An approximate

135-mi2 area of the North Prong Alafia River watershed is drained at the Keysville gage (02301000) at

SR 676. Discharge data have been collected continuously at the Keysville gage by the USGS from 1950-92

and from 1995 to the present. Extremes in daily mean

discharge at the Keysville gage ranged from 3.9 (1952)

to 8,200 ft3/s (1960). The channel along the study reach

generally is deeply incised and well defined, confining

all but the highest discharges within the banks. 

Step-backwater analysis was performed at 22

cross sections along the North Prong Alafia River

study reach, from the mouth (confluence) to cross

section 23. The step-backwater analysis was based on

the selected percentile discharges (P10, P50, P70, P80,

Figure 28. Location of the Alafia, North Prong Alafia, and South Prong Alafia Rivers and cross sections, 

west-central Florida. (Location of study area shown in figure 1).
48 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

P90, P98, P99.5 and P99.9) for the concurrent long-term

period 1964-92 at the Alafia River at Lithia, North

Prong Alafia River at Keysville, and South Prong

Alafia River near Lithia gages. The step-backwater

analysis began at the Alafia River at Lithia gage and

progressed upstream to the confluence with the North

and South Prong Alafia Rivers. At the confluence and

selected upstream cross sections, discharge was

reduced to reflect the smaller contributing drainage

area size (table 5). Step-backwater computations

continued upstream along the North Prong Alafia River

for approximately 4 mi to the Keysville gage at

SR 676, then continued to termination at cross section

23. Water-surface profiles, extent of inundation, and

hydraulic depth were based on the computed watersurface elevations for the selected discharge percentiles

(fig. 34). 

Estimated floodplain inundation exceeds 1,900 ft

(cross section 16.5) during P99.9 discharge (1,906 ft3/s)

(app. Q). Mean inundation width, based on the 22 cross

sections, ranges from 68 ft (P10) to 1,237 ft (P99.9).

The incised channel along much of the reach

generally confines most flows at or below the P80

discharge (185 ft3/s) upstream and the P90 discharge

(270 ft3/s) downstream of the gage (fig. 35 and table 5).

The mean inundation width at the P80 discharge (160 ft)

may approximate the mean width of the channel. The

greatest increases in the extent of mean areal inundation, approximately 406 ft, occurs between the P90

(258 ft) to the P98 (664 ft) discharge (app. Q).

A comparison of the maximum extent of areal inundation for the selected percentile discharges at each cross

section is shown in figure 35. However, the figure does

not indicated the existence of elevated land surface

along the cross section that may be completely inundated during high-flow periods or may form islands

during low-flow periods, thus reducing the actual

distance inundated. Appendix Q presents the actual

distance, in feet, each cross section is inundated.

Percentile discharges below P98 (683 ft3/s) at

example cross section 17 generally are confined within

the channel, and those percentiles at or above P98 may

inundate the floodplain (fig. 31b and table 5). The

approximate mean number of days that inundation of

the floodplain occurs at the P98 discharge is 8 days per

year based on the Alafia River at Lithia gage (table 6).

During the 29-year study period, discharge conditions

at the P98 occurred 19 times.

Table 5. Cross sections, drainage area, and percentile discharges used in

step-backwater analysis based on the concurrent period 1964-92 at the

Alafia, North Prong Alafia, and South Prong Alafia Rivers gages

[ft3/s, cubic feet per second; mi2, square miles]

Crosssection 

range

Drainage 

area (mi2)

Discharge (ft3/s)

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Alafia River at Lithia

173-84 335 74.3 184 297 404 601 1,418 2,417 3,820

85-95 285 62.6 172 275 363 544 1,348 2,272 3,717

96-21 275 60.2 170 271 355 532 1,334 2,242 3,696

North Prong Alafia River at Keysville

1-14 140 38.3 98 147 185 270 683 1,175 1,906

316-20 135 36.9 94 142 178 260 659 1,133 1,838

21-23 130 35.5 90 136 172 251 635 1,091 1,770

South Prong Alafia River near Lithia

1-6 135 22 72 124 170 262 651 1,067 1,790

6.5-12 130 21 70 119 164 253 627 1,028 1,724

13-22 122 19.8 65 112 154 237 588 965 1,618

424-29 107 17.4 57 98 135 208 516 846 1,419

1Alafia River at Lithia gage.

2Confluence with section 1 of the North and South Prong Alafia Rivers.

3North Prong Alafia River gage at Keysville.

4South Prong Alafia River near Lithia.
Alafia River System 49 80,000 85,000 90,000 95,000 100,000 105,000 110,000 115,000 120,000 125,000

5

4540353025201510

76 77

78

79

80

81

82

85

86

87

88

89

90

91

92

93

96

73

DISTANCE UPSTREAM FROM MOUTH, IN FEET

ELEVATION, IN FEET ABOVE NGVD OF 1929

SR 640 Bridge and Lithia Gaging Station

Railroad Bridge

SR 39 Bridge

Confluence-North and South Prong Alafia Rivers

Alafia River

Alafia River Channel

Solid lines indicate percentile discharge profile. Dashed lines indicate a potential 10-percent discharge withdrawal 

Maximum elevationof bridge opening

Cross Section Number

Land-Surface Elevation

P99.9P99.5

P98P90P80P70P50P10

P98-10P90-10P70-10P50-10

P10-10

P99.5-10P99.9-10

P80-10

Figure 29. Water-surface profiles along the Alafia River for existing conditions and a potential 10-percent discharge withdrawal, from the SR 640 bridge to the confluence with the North and South Prong Alafia Rivers.
50 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

Hydraulic depths below the P90 discharge generally are confined to the channel. Mean hydraulic depths

ranged from approximately 1.6 to 3.7 ft, and maximum

depths ranged from 2.8 to 6.9 ft (app. R). Because of

the increase in cross-sectional area in the transition

from the channel to floodplain in example cross section

17, the hydraulic depth of 2.4 ft at the P90 discharge is

double that of the P98 discharge (1.2 ft) (fig. 31b).

Total area of inundation within the channel and

floodplain ranged from 48.2 (P10) to 854 (P99.9) acres

(fig. 36 and app. S). Inundated area below the P80

discharge upstream and the P90 discharge downstream

of the gage generally was confined within the channel

at most cross sections (fig. 35).The inundated area

from the P10 to the P80 discharges was approximately

111 acres, which largely consists of the channel area,

whereas, the inundated area from the P80 to the P99.9

discharges, which includes both the channel and floodplain, was 695 acres. The greatest increase in area of

inundation between percentiles was 248 acres, which

occurred from the P90 to P98 discharges.

The difference in inundated area, between the

existing conditions step-backwater analysis and a

potential withdrawal step-backwater analysis, ranged

from 0.4 (P10) to 45.5 (P98) acres, which corresponds to

an approximate 0.7 and 9.0 percent decrease of inundated area, respectively (fig. 36 and app. T). However,

the greatest percentage decrease of inundated area

occurred at the P80-10 discharge with 23.4 percent.

Decrease of inundated area at or below the P80-10

discharge generally occurred within the channel, and

ranged from approximately 0.4 to 38 acres. The greatest decrease, 45.5 acres, occurred at the P98-10 discharge

(fig. 37a-h).

South Prong Alafia River

The South Prong Alafia River drains approximately 135 mi2. The 10-mi-long South Prong Alafia

River study reach generally flows in a northerly direction, from cross section 29 to the confluence with the

Alafia and North Prong Alafia Rivers at cross section 1

(figs. 1 and 28). A 107-mi2 area of the watershed is

drained at the South Prong Alafia River near Lithia

gage (02301300) at Jameson Road. Discharge data

have been collected continuously by the USGS at the

gage from 1962 to the present. Extremes in daily mean

discharge at the gage ranged from 1.2 ft3/s (1981) to

2,430 ft3/s (1967). The low-water channel along the

study reach of the South Prong Alafia River generally

is deeply incised and well defined. 

Step-backwater analysis was performed using 31

cross sections located along the South Prong Alafia

River from cross section 1 (confluence) to cross section

29. Step-backwater analysis computations for the

South Prong Alafia River began at the Alafia River

near Lithia gage and progressed upstream to the confluence with the North and South Prong Alafia Rivers.

Table 6. Approximate number of days daily mean discharge 

equaled or exceeded the percentile discharges at Alafia River 

at Lithia, 1964-92

[P10, 10-percentile discharge; -- no days]

Year

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

1964 366 260 187 101 49 7 2 --

1965 365 231 122 69 39 10 3 --

1966 365 282 200 136 67 -- -- --

1967 348 191 130 78 39 15 7 3

1968 348 159 135 99 77 19 7 --

1969 365 237 168 102 52 5 -- --

1970 363 321 250 135 57 10 1 --

1971 345 125 93 49 19 -- -- --

1972 366 141 85 56 27 3 -- --

1973 365 198 149 96 52 4 2 --

1974 350 135 85 62 42 15 3 --

1975 314 107 84 57 22 -- -- --

1976 341 208 140 84 43 2 -- --

1977 270 60 21 7 2 -- -- --

1978 333 157 96 62 32 -- -- --

1979 352 203 147 113 81 21 10 3

1980 366 276 157 72 23 4 2 --

1981 252 72 43 29 19 3 1 --

1982 346 152 112 74 32 6 2 --

1983 365 211 178 140 96 7 2 --

1984 350 225 145 77 23 -- -- --

1985 178 66 38 19 9 3 1 --

1986 284 111 73 39 18 -- -- --

1987 313 145 113 81 45 5 4 --

1988 349 164 118 62 31 9 6 4

1989 312 106 58 25 16 -- -- --

1990 247 77 32 13 1 -- -- --

1991 233 111 76 45 25 8 5 1

1992 228 74 41 21 12 -- -- --

Mean 323 166 113 69 36 8 4 3

Maximum 366 321 225 140 96 21 10 4

Minimum 178 60 21 7 1 0 0 0
Alafia River System 51

0 2,000 FEET

0 250 500 METERS

1,000

SR 39 Bridge

Confluence

Alafia River Channel

CROSS SECTION

Alafia River

Flow

Bank Station

SR 640 Bridge and

Gaging Station

Railroad Bridge

73 75

76

80

82

85

86

88

89

90

91

92

93

96

87

84

81

78

CROSS SECTION NUMBER

LIMIT OF STUDY

FLOODPLAIN 

BOUNDARY

P99.9

P99.5

P98

P90

P80

P70

P50

EXPLANATION

P10

Percentile Discharges

Figure 30. Extent of areal inundation along the Alafia River channel and floodplain for selected 

percentile discharges, from SR 640 to the confluence with the North and South Prong Alafia Rivers.
52 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida ELEVATION, IN FEET ABOVE NGVD OF 1929

0 1,000 2,000 3,000 4,000 5,000 6,000

10

15

20

25

30

35

40

45

Cross section 79

Alafia River Channel

P99.9, 1.8 ft

P99.5, 1.6 ft

P98, 5.8 ft

P90, 6.3

P80, 5.2

P70, 4.4

P50, 3.4

P10, 1.8

1,000 2,000 3,000 4,000

40

45

50

55

60

65

North Prong Alafia River Cross section 17

P90, 2.4

P70, 1.6 P80, 1.9

P50, 1.4 P10, 1.0

P99.9, 2.1

P99.5, 1.5

P98, 1.2

North Prong Alafia River Channel

0 1,000 2,000 3,000

40

50

60

70

South Prong Alafia River Channel

P90, 1.0

P70, 1.1 P,80 1.0

P50, 1.7

P10, 1.5

P99.9, 2.4

P99.5, 1.8 P98, 1.4

DISTANCE FROM LEFT BANK, IN FEET

(b)

(a)

(c) South Prong Alafia River

Alafia River at Lithia, 1964-92

 P99.9 3 4

 P99.5 4 16 

 P98 8 19

 P90 36 29

 P80 69 29

 P70 113 29

 P50 166 29

 P10 323 29

 Percentile Mean Num- Number Years

 of days of Occurrence

Cross Section 14

EXPLANATION

P99.9 Percentile Discharge

2.4 ft Hydraulic Depth

EXPLANATION

P99.9 Percentile Discharge

2.1 ft Hydraulic Depth

EXPLANATION

P99.9 Percentile Discharge

1.81 ft Hydraulic Depth

Looking downstream

Looking downstream

Looking downstream

Land-Surface Elevation

Figure 31. Estimated extent and frequency of areal inundation and hydraulic depth for (a) Alafia, (b) North 

Prong Alafia, and (c) South Prong Alafia Rivers selected cross sections for each of the percentile discharges.
Alafia River System 53

10 50 70 80 90 98 99.5 99.9

PERCENTILE DISCHARGE

TOTAL INUNDATED AREA, IN ACRES

Alafia River

Area inundated

Total number of acres inundated

after 10-percent discharge withdrawal

th th th th th th th th

Lines indicate interpolated inundated area

1.0 % 1.6 % 2.4 % 2.6 %

19.6 %

12.7 %

7.7 %

4.0 %

Percent inundated area decreased

1964-92

0

100

200

300

400

500

600

700

800

900

1,000

1,100

1,200

1,300

1,400

1,500

At the confluence, discharge was reduced to reflect the

smaller drainage area contribution of the South Prong

Alafia Rivers. Step-backwater computations continued

upstream along the South Prong Alafia River for

approximately 7.6 mi to the gage at Jameson Road,

then continued to termination at cross section 29.

Water-surface elevations, computed during the stepbackwater analysis, were used to produce watersurface profiles, extent of areal inundation, and hydraulic depth at the 31 cross sections (fig. 38). 

Estimated floodplain inundation exceeds 1,600 ft

(cross section 20) during P99.9 discharge (app. Q).

Mean inundation width for the 31 cross sections along

the reach can range from 36 ft (P10) to 1,135 ft (P99.9).

The incised channel generally confines most flows

within the banks below the P80 discharge (170 ft3/s)

along much of the reach, except at a limited number of

low-lying cross sections (fig. 39 and table 5). The mean

inundation width at the P80 discharge (109 ft) may

approximate the mean width of the bankfull channel.

The greatest increase in the extent of mean inundation

was 566 ft from the P90 (197 ft) to the P98 (763 ft)

discharge (app. Q). A comparison of the maximum

extent of areal inundation for the selected percentile

discharges at each cross section is shown in figure 39.

However, the figure does not indicated the existence of

elevated land surface along the cross section that may

be completely inundated during high-flow periods or

may form islands during low-flow periods, thus reducing the actual distance inundated. Appendix Q presents

the actual distance, in feet, each cross section is inundated.

Example cross section 14 shows discharges at or

below P50 generally are confined to the channel, and

those above may inundate the floodplain (fig. 31c). The

approximate mean number of days that inundation of

the floodplain occurs at the P50 discharge is 166 days

per year, based on the 29-year study period at Alafia

River at Lithia (table 6).

Hydraulic depths at or below the P50 discharge

generally reflect the channel. Mean hydraulic depths

ranged from approximately 1.2 (P10) to 2.5 (P80) ft, and

maximum depths ranged from 2.2 (P10) to 4.4 (P90) ft

(app. R). Cross section 14 has an approximate 1-ft

hydraulic depth that occurs during the P90 discharge an

average of about 36 days per year, based on a width of

more than 600 ft. 

Figure 32. Estimated total inundated area along the Alafia River for existing conditions and for a potential 

10-percent discharge withdrawal, and percentage of inundated area decreased by a potential 10-percent 

discharge withdrawal for each of the selected percentile discharges.
54 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

0

0 500 METERS

3,000 FEET

P10 P50

78

80

82

85

86

88

89

90

91

92

93

96

73

87

84

75

81

79

77

76

78

80

82

85

86

88

89

90

91

92

93

96

73

87

84

75

81

79

77

76

Confluence

CROSS SECTION

Alafia River Channel

Alafia River

Railroad Bridge

Extent of areal inundation

for P10 discharge

SR 640 Bridge and

Gaging Station

SR 39 Bridge SR 39 Bridge

(a) (b) Flow

LIMIT OF STUDY

FLOODPLAIN 

BOUNDARY

Cross Section Number

P10-10 (a) and P50-10 (b)

 P10 (a) and P50 (b)

EXPLANATION

Figure 33. Extent of areal inundation along the Alafia River channel and floodplain for the (a) P10, (b) P50, 

(c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions and a potential 

10-percent discharge withdrawal.
Alafia River System 55

P70

Confluence

CROSS SECTION

Alafia River Channel

78

80

82

85

86

88

89

90

91

92

93

96

73

87

84

75

81

79

77

76

Alafia River

Railroad Bridge

SR 640 Bridge and

Gaging Station

P80

78

80

82

85

86

88

89

90

91

92

93

96

73

87

84

75

81

79

77

76

SR 39 Bridge SR 39 Bridge

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

(c) (d) Flow

CROSS SECTION NUMBER

P P 70-10 80-10 (c) and (d)

 P P 70 80 (c) and (d)

EXPLANATION

0

0 500 METERS

3,000 FEET

Figure 33. Extent of areal inundation along the Alafia River channel and floodplain for the (a) P10, (b) P50, 

(c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions and a potential 

10-percent discharge withdrawal. (Continued)
56 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

Confluence

CROSS SECTION

Alafia River Channel

Alafia River

Railroad Bridge

SR 640 Bridge and

Gaging Station

P98

SR 39 Bridge SR 39 Bridge

(e) (f) Flow

78

80

82

85

86

88

89

90

91

92

93

96

73

87

84

75

81

79

77

76

P90

78

80

82

85

86

88

89

90

91

92

93

96

73

87

84

75

81

79

77

76

CROSS SECTION NUMBER

LIMIT OF STUDY 

FLOODPLAIN BOUNDARY

P P 90-10 98-10 (e) and (f)

P P 90 98 (e) and (f)

EXPLANATION

0

0 500 METERS

3,000 FEET

Figure 33. Extent of areal inundation along the Alafia River channel and floodplain for the (a) P10, (b) P50, 

(c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions and a potential 

10-percent discharge withdrawal. (Continued)
Alafia River System 57

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

0

0 500 METERS

3,000 FEET

P99.5

Confluence

CROSS SECTION

Alafia River Channel

Alafia River

Railroad Bridge

SR 640 Bridge and

Gaging Station

SR 39 Bridge SR 39 Bridge

(g) (h) Flow

78

80

82

85

86

88

89

90

91

92

93

96

73

87

84

75

81

79

77

76

P99.9

78

80

82

85

86

88

89

90

91

92

93

96

73

87

84

75

81

79

77

76

CROSS SECTION NUMBER

P99.5-10 (g) and P99.9-10 (h)

 P99.5 (g) and P99.9 (h)

EXPLANATION

Figure 33. Extent of areal inundation along the Alafia River channel and floodplain for the (a) P10, (b) P50, 

(c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions and a potential 

10-percent discharge withdrawal. (Continued)
58 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

656055504540353025

DISTANCE UPSTREAM FROM CONFLUENCE, IN FEET

1 2

3

4

5

8

9

10

13

15 17

18 19

20

21

22

23

0 10,000 20,000 30,000 40,000 50,000 50,500

ELEVATION, IN FEET ABOVE NGVD OF 1929

Railroad Bridge

Railroad Bridge

SR 676 Bridge and Gaging Station

Confluence

North Prong Alafia River

North Prong Alafia River Channel

Solid lines indicate percentile discharge profile.Dashed lines indicate10-percent discharge withdrawal 

Maximum elevationof bridge opening

Cross Section Number

Land-Surface Elevation

P99.9P99.5

P98P90P80P70P50P10

P98-10P90-10P70-10P50-10

P10-10

P99.5-10P99.9-10

P80-10

Figure 34. Water-surface profiles along the North Prong Alafia River for existing conditions and a potential 10-percent discharge 

withdrawal, from the confluence with the Alafia and South Prong Alafia Rivers to cross section 23.
Alafia River System 59

Confluence

North Prong Alafia

 River Channel

Flow

CROSS SECTION

North Prong Alafia River

3

4

5

8

9

10

16.5

17

18

19

21

22

23

2

20

1

Railroad Bridge

Railroad Bridge

SR 676 Bridge and

Gaging Station

CROSS SECTION

NUMBER

LIMIT OF STUDY

FLOODPLAIN

BOUNDARY

P99.9

P99.5

P98

P90

P80

P70

P50

P10

EXPLANATION

Percentile Discharge

0

0

2,000 FEET

500 METERS

Total inundated area of the channel and floodplain ranged from 36.6 (P10) to 1,055 (P99.9) acres

(fig. 40 app. S). The difference in inundated area

between the P10 and P80 discharges was approximately

80 acres, which largely includes the area confined

within the channel, whereas the inundated area

between the P80 and P99.9 discharges, which generally

includes the floodplain, was 938 acres. The greatest

increase in area of inundation (538 acres) occurs

between the P90 and P98 discharges.

Decrease in inundated area, between the existing

step-backwater analysis and the potential step-backwater analysis, ranged from 0.2 (P10) to 75 (P98) acres,

which corresponds to an approximate 1.5- and 10-percent decrease of inundated area, respectively (fig. 40

and app. T). However, the greatest percentage decrease

of inundated area occurred at the P90-10 discharge with

13.4 percent. Decrease of inundated area at or

below the P80-10 discharge generally occurred within

the channel and ranged from 0.2 to 10.4 acres. The

greatest decrease in inundated area (75 acres) occurs at

the P98-10 discharge (fig. 41a-h).

Inundated Area and Effects of Potential 

Discharge Withdrawals Along the Alafia 

River System

Total inundated area for the Alafia, North Prong

Alafia, and South Prong Alafia Rivers ranged from

137.8 (P10 discharge) to 3,354 (P99.9 discharge) acres

(fig. 42 and app. S). Although the lengths of the Alafia,

North Prong Alafia, and South Prong Alafia River

study reaches are similar at 8.2, 9.5, and 10 mi, the

acreage of inundation for the P99.9 discharge for the

Alafia River was 41 and 27 percent greater than that of

the North and South Prong Alafia River, respectively

(app. S). At the P80 discharge, the 348 acres inundated

along the Alafia River system generally are confined to

the channel. The largest increase in inundated area is

1,363 acres, which occurs between the P90 and the P98

discharges. Decrease of total inundated area along the

Alafia, North Prong Alafia, and South Prong Alafia

Rivers study reaches ranged from about 1.3 (P10

discharge) to 196 (P98 discharge) acres, which corresponds to a 1.1 and 10.7 percent decrease of inundated

area, respectively. However, the greatest percentage

decrease of inundated area occurred at the P80-10

discharge with 14.5 percent.

Figure 35. Extent of areal inundation along the North 

Prong Alafia River channel and floodplain for selected 

percentile discharges, from the confluence with the 

Alafia and South Prong Alafia Rivers to cross 

section 23.
60 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

PERCENTILE DISCHARGE

10 50 70 80 90 98 99.5 99.9 th th th th th th th th

Areal inundated

Total number of acres inundated after

10-percent discharge withdrawal

TOTAL INUNDATED AREA, IN ACRES

North Prong Alafia River

Lines indicate interpolated inundated area

0.7 % 1.1 % 14.7 %

23.4 %

10.7 %

9.0 %

4.9 %

2.3 %

Percent inundated area decreased

0

100

200

300

400

500

600

700

800

900

SUMMARY 

Riverine and palustrine wetlands are a major

ecological component of river basins in west-central

Florida. Healthy wetlands are dependent upon the

frequency and duration of periodic inundation. This

report assesses the extent, area, depth, frequency, and

duration of periodic flooding and the effects of potential surface-water withdrawals on Cypress Creek and

the Peace, Alafia, North Prong Alafia, and South Prong

Alafia Rivers. Results of the study were based on stepbackwater analysis performed at each of the river

systems using the U.S. Army Corps of Engineers

Hydrologic Engineering Center-River Analysis System

(HEC-RAS) one-dimensional model. Step-backwater

analysis of selected mean daily discharges at the 10th,

50th, 70th, 80th, 90th, 98th, 99.5th, and 99.9th percentiles

was used to compute extent of inundation, area, and

hydraulic depth. An assessment of the net changes of

areal inundation was compared between existing and

potential conditions, if 10 percent of the total river flow

were diverted for potential withdrawals. 

Cypress Creek, a major tributary to the Hillsborough River, drains a 164 mi2 area north of the city of

Tampa. The low-gradient channel generally is poorly

incised and defined. Widespread areal inundation of

lower Cypress Creek occurs at the 50th percentile.

However, the most widespread inundation of the broad

palustrine wetlands, which dominate the length of the

Cypress Creek floodplain, occurs at the 80th percentile.

The total inundated area of Cypress Creek ranged from

about 1,200 (50th percentile) to 9,000 (99.9th percentile)

acres. The mean hydraulic depth ranged from 0.8 to 2.9 ft,

with a maximum depth of 7.8 ft. Based on a potential

10-percent withdrawal in discharge, the decrease in area

of inundation along Cypress Creek ranged from 22 to

395 acres, and the percent of decreased inundated area

ranged from 1.7 to 8.4 percent.

A 70-mi-long channel of the Peace River was

divided into three study reaches: Arcadia to Zolfo

Springs (reach 1), Zolfo Springs to Fort Meade (reach

2), and Fort Meade to Bartow (reach 3). The step-backwater analysis was based on the concurrent long-term

streamflow record, 1940-98, at the Peace River at

Arcadia, Zolfo Springs, and Bartow gages. Total inundated area of reach 1 ranged from 377 to 17,196 acres.

Mean hydraulic depth ranged from 1.7 to 5.4 ft, with a

maximum depth of 12 ft. The decrease in area of inundation from a potential 10-percent withdrawal in

discharge ranged from approximately 5 to 1,500 acres.

Figure 36. Estimated total inundated area along the North Prong Alafia River for existing conditions and 

for a potential 10-percent discharge withdrawal, and percentage of inundated area decreased by a 

potential 10-percent discharge withdrawal for each of the selected percentile discharges.
Summary 61

5

North Prong Alafia River

P10

Confluence

Railroad Bridge

Railroad Bridge

SR 676 Bridge

and

Gaging Station

North Prong Alafia River Channel

CROSS SECTION

P50

Flow

3

4

8

9

10

16.5

17

19

21

22

23

2

20

1

3

4

5

8

9

10

16.5

17

18

19

21

22

23

2

20

1

18

(a) (b)

CROSS SECTION NUMBER

P P 10-10 50-10 (a) and (b)

 P P 10 50 (a) and (b)

EXPLANATION

LIMIT OF STUDY

FLOODPLAIN 

BOUNDARY

0 1,000 2,000 FEET

0 250 500 METERS

Figure 37. Extent of areal inundation along the North Prong Alafia River channel and floodplain for the (a) P10, 

(b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions and a potential 

10-percent discharge withdrawal.
62 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

0 1,000 2,000 FEET

0 250 500 METERS

3

4

5

8

9

10

16.5

17

18

19

21

22

23

2

20

1

3

4

5

8

9

10

16.5

17

18

19

21

22

23

2

20

1

North Prong Alafia River

P70

Confluence

Railroad Bridge

Railroad Bridge

SR 676 Bridge 

and

Gaging Station

North Prong Alafia River Channel

CROSS SECTION

LIMIT OF STUDY

FLOODPLAIN 

BOUNDARY

P80

Flow

(c) (d)

CROSS SECTION NUMBER

P70-10 (c) and P80-10 (d)

 P70 (c) and P80 (d)

EXPLANATION

Figure 37. Extent of areal inundation along the North Prong Alafia River channel and floodplain for the (a) P10, 

(b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions and a potential 

10-percent discharge withdrawal. (Continued)
Summary 63

0 1,000 2,000 FEET

0 250 500 METERS

LIMIT OF STUDY

FLOODPLAIN 

BOUNDARY

3

4

5

8

9

10

16.5

17

18

19

21

22

23

2

20

3

4

5

8

9

16.5

17

18

19

21

22

23

2

20

1 1

10

North Prong Alafia River

Confluence

Railroad Bridge

Railroad Bridge

SR 676 Bridge and

Gaging Station

North Prong Alafia River Channel

CROSS SECTION Flow

(e) (f)

CROSS SECTION NUMBER

P90-10 (e) and P98-10 (f)

 P90 (e) and P98 (f)

EXPLANATION

P90 P98

Figure 37. Extent of areal inundation along the North Prong Alafia River channel and floodplain for the (a) P10, 

(b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions and a potential 

10-percent discharge withdrawal. (Continued)
64 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

LIMIT OF STUDY

FLOODPLAIN 

BOUNDARY

0 1,000 2,000 FEET

0 250 500 METERS

North Prong Alafia River

Confluence

Railroad Bridge

Railroad Bridge

SR 676 Bridge 

and

Gaging Station

North Prong Alafia River Channel

CROSS SECTION

Flow

(g) (h)

3

4

5

8

9

10

16.5

17

18

19

21

22

23

2

20

1

3

4 5

8

9

10

16.5

17

18

19

21

22

23

2

20

1

CROSS SECTION NUMBER

P99.5-10 (g) and P99.9-10 (h)

 P99.5 (g) and P99.9 (h)

EXPLANATION

P99.5 P99.9

Figure 37. Extent of areal inundation along the North Prong Alafia River channel and floodplain for the (a) P10, 

(b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions and a potential 

10-percent discharge withdrawal. (Continued)
Summary 65

65

60

55

50

45

40

35

30

25

1 2

3 4 5

66.59.5

10

11

12

13

14

15

16

17

18

19

20

2122

25

26

27

28

29

0 10,000 20,000 30,000 40,000 50,000 50,500

DISTANCE UPSTREAM FROM CONFLUENCE, IN FEET

ELEVATION, IN FEET ABOVE NGVD OF 1929

Confluence

SR 640 Bridge

Jameson Road Bridge

Gaging Station South Prong Alafia River

South Prong Alafia River Channel

Solid lines indicate percentile discharge profileDashed lines indicate potential 10-percent discharge withdrawal 

Cross Section Number

Land-Surface Elevation

P99.9P99.5

P98P90P80P70P50P10

P98-10P90-10P70-10P50-10

P10-10

P99.5-10P99.9-10

P80-10

Figure 38. Water-surface profiles along the South Prong Alafia River for existing conditions and a potential 10-percent discharge withdrawal, from the confluence with the Alafia and North Prong Alafia Rivers to cross section 29.
66 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

0 1,000 2,000 FEET

0 250 500 METERS

South Prong Alafia River Channel

Flow

CROSS SECTION

South Prong Alafia River

Jameson Road and

 Gaging Station

SR 640

Bridge

3

4

5

9

10

16

17

18

19

21.5

22

2

20

1

28

27

26

25

24

15

14

13

12

11

6

P99.9

P99.5

P98

P90

P80

P70

P50

EXPLANATION

P10

CROSS SECTION NUMBER

Percentile Discharge

Figure 39. Extent of areal inundation along the South Prong Alafia River channel and floodplain 

for selected percentile discharges, from the confluence with the Alafia and North Prong Alafia 

Rivers to cross section 29.
Summary 67

10 50 70 80 90 98 99.5 99.9

PERCENTILE DISCHARGE

th th th th th th th th

TOTAL INUNDATED AREA, IN ACRES

South Prong Alafia River

1.5 %

2.1 %

10.0 %

4.8 %

Area inundated

Total number of acres inundated

after 10-percent discharge withdrawal

Lines indicate interpolated inundated area

5.1 % 9.6 % 9.0 %

13.4 % Percent inundated area decreased

0

100

200

300

400

500

600

700

800

900

1,000

1,100

Total inundated area of reach 2 ranged from 225 to

6,100 acres. Mean hydraulic depth ranged from 1.5 to

5.5 ft, with a maximum depth of 11 ft. The decrease in

area of inundation, from a potential 10-percent withdrawal in discharge, ranged from about 6 to 370 acres.

Total inundated area of reach 3 ranged from about 170

to 2,800 acres. The mean hydraulic depth ranged from

1.5 to 4.6 ft, with a maximum depth of 7.2 ft. The

decrease in area of inundation, from a potential 10-

percent withdrawal in discharge, ranged from about 7

to 100 acres. Total area of inundation for the three

reaches of the Peace River ranged from 775 to 26,100

acres. Based on a potential 10-percent withdrawal in

discharge, the decrease in area of inundation along the

three reaches of the Peace River ranged from about 17

to 1,900 acres, and decreased inundation ranged from

2.1 to 13.6 percent.

The 8.2-mi-long Alafia River study channel, from

the SR 640 bridge to the confluence with the North and

South Prong Alafia Rivers, is deeply incised, confining

most discharge at or below the 90th percentile. Total

inundated area ranged from approximately 50 to 1,400

acres. Mean hydraulic depth ranged from 1.8 to 4.8 ft,

with a maximum depth of 9.2 ft. Based on a potential

10-percent withdrawal in discharge, the decrease in area

of inundation along the Alafia River ranged from about

1 to 90 acres, and the percent of decreased inundated

area ranged from 1.0 to 19.6 percent.

The 9.5-mi-long North Prong Alafia River study

channel also is deeply incised. Discharges below the

80th percentile generally are confined within the banks.

Step-backwater analysis was performed at 22 cross

sections. Total inundated area ranged from about 48 to

850 acres. Mean hydraulic depth ranged from 1.6 to 3.7 ft,

with a maximum depth of about 7 ft. Based on a potential 10-percent withdrawal in discharge, the decrease in

area of inundation along the North Prong Alafia River

ranged from less than 1 to about 46 acres, and the

percent of decreased inundated area ranged from about

1 to 23 percent.

The 10-mi-long South Prong Alafia River channel

is deeply incised and generally contains discharges below

the 80th percentile. Step-backwater analysis was

performed using 31 cross sections. Total inundated area

ranged from about 40 to 1,100 acres. Mean hydraulic

depth ranged from 1.2 to 2.5 ft, with a maximum depth of

4.4 ft. The decrease in area of inundation, from a potential 10-percent withdrawal in discharge, ranged from less

than 1 to 75 acres, for discharges at the 10th and 98th

percentiles, respectively. Based on a potential 10-percent

withdrawal in discharge, the percent of decreased inundated area ranged from 1.5 to 13.4 percent.

Figure 40. Estimated total inundated area along the South Prong Alafia River for existing conditions and for a 

potential 10-percent discharge withdrawal, and percentage of inundated area decreased by a potential 10-percent 

discharge withdrawal for each of the selected percentile discharges.
68 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

15

16

17

18

19

20

21.5

25

26

27

29

28

24

22

3

4

5

6

10

11

12

13

14

1

2

9

15

16

17

18

19

20

21.5

25

26

27

29

28

24

22

3

4

5

6

10

11

12

13

14

1

2

9

P10 P50

South Prong Alafia River

Jameson Road and

Gaging StationFlow

Confluence

SR 640

CROSS SECTION

South Prong Alafia River Channel

(a) (b)

CROSS SECTION NUMBER

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

P10-10 (a) and P50-10 (b)

 P10 (a) and P50 (b)

EXPLANATION

0 1,000 2,000 FEET

0 250 500 METERS

Figure 41. Extent of areal inundation along the South Prong Alafia River channel and floodplain for the 

(a) P10, (b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions 

and for a potential 10-percent discharge withdrawal.
Summary 69

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

15

16

17

18

19

20

21.5

25

26

27

29

28

24 22

3

4

5

6

10

11

12

13

14

1

2

9

15

16

17

18

19

20

21.5

25

26

27

29

28

24

22

3

4

5

6

10

11

12

13

14

1

2

9

South Prong Alafia River

Jameson Road and

Gaging Station

Confluence

SR 640

CROSS SECTION

South Prong Alafia River Channel

(c) (d) Flow

CROSS SECTION NUMBER

P70-10 (c) and P80-10 (d)

 P70 (c) and P80 (d)

EXPLANATION

0 1,000 2,000 FEET

0 250 500 METERS

P70 P80

Figure 41. Extent of areal inundation along the South Prong Alafia River channel and floodplain for the 

(a) P10, (b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions 

and for a potential 10-percent discharge withdrawal. (Continued)
70 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

15

16

17

18

19

20

21.5

25

26

27

29

28

24

22

3

4

5

6

10

11

12

13

14

1

2

9

15

16

17

18

19

20

21.5

25

26

27

29

28

24

22

3

4

5

6

10

11

12

13

14

1

2

9

South Prong Alafia River

Jameson Road and

Gaging Station

Confluence

SR 640

CROSS SECTION

South Prong Alafia River Channel

(e) (f)

P90 P98 Flow

CROSS SECTION NUMBER

P90-10 (e) and P98-10 (f)

 P90 (e) and P98 (f)

EXPLANATION

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

0 1,000 2,000 FEET

0 250 500 METERS

Figure 41. Extent of areal inundation along the South Prong Alafia River channel and floodplain for the 

(a) P10, (b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions 

and for a potential 10-percent discharge withdrawal. (Continued)
Summary 71

South Prong Alafia River

(g) (h)

P99.5-10 (g) and P99.9-10 (h)

 P99.5 (g) and P99.9 (h)

EXPLANATION

0 1,000 2,000 FEET

0 250 500 METERS

Jameson Road and

Gaging Station

15

16

17

18

19

20

21.5

25

26

27

29

28

24

22

3

4

5

6

10

11

12

13

14

1

2

9

Confluence

SR 640

CROSS SECTION

South Prong Alafia River Channel

15

16

17

18

19

20

21.5

25

26

27

29

28

24

22

3

4

5

6

10

11

12

13

14

1

2

9

P99.5 P99.9 Flow

CROSS SECTION NUMBER

LIMIT OF STUDY

FLOODPLAIN BOUNDARY

Figure 41. Extent of areal inundation along the South Prong Alafia River channel and floodplain for the 

(a) P10, (b) P50, (c) P70, (d) P80, (e) P90, (f) P98, (g) P99.5, and (h) P99.9 discharges for existing conditions 

and for a potential 10-percent discharge withdrawal. (Continued)
72 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

PERCENTILE DISCHARGE

10 50 70 80 90 98 99.5 99.9 th th th th th th th th

Inundated area

TOTAL INUNDATED AREA, IN ACRES

Alafia, North Prong Alafia, and

South Prong Alafia River

Lines indicate interpolated inundated area

0

500

1,000

1,500

2,000

2,500

3,000

3,500

2.9 %

6.0 %

10.7 %

13.4 %

14.5 %

2.5 % 9.4 % 1.1 %

Area inundated after a 10-percent

discharge withdrawal

Percent inundated

area decreased

SELECTED REFERENCES

Broska, J.C., and Knochenmus, L.A., 1996, Assessment of

the hydrogeology and water quality in a near-shore wellfield, Sarasota, Florida: U.S Geological Survey WaterResources Investigations Report 96-4036, 64 p.

Cowardin, Lewis, M., Carter, Virginia, Golet, Francis, C.,

and LaRoe, Edward, T., 1979, Classification of wetlands

and deepwater habitats of the United States: U.S. Fish

and Wildlife Service, FWS/OBS-79/31, 103 p.

Hammett, K.M., 1990, Land use, water use, streamflow

characteristics, and water-quality characteristics of the

Charlotte Harbor inflow area, Florida: U.S. Geological

Survey Water-Supply Paper 2359-A, 64 p.

Murphy Jr., W.R., 1978, Flood profiles for Cypress Creek,

west-central Florida: U.S. Geological Survey WaterResources Investigations Report 78-8, 29 p.

Murphy Jr., W.R., Hammett, K.M., and Reeter, C.V., 1978,

Flood profiles for Peace River, south-central Florida:

U.S. Geological Survey Water-Resources Investigations Report 78-57, 35 p.

Robertson, A.F., 1978, Flood profiles of the Alafia River,

west-central Florida: U.S. Geological Survey WaterResources Investigations Report 77-74, 21 p.

Shearman, J.O., 1976, Computer program E431 user’s manual, U.S. Geological Survey Open-File Report 76-499,

175 p.

Southwest Florida Water Management District, 2001,

Brooksville, Fla., Regional Water-Supply Plan.

Stamey, T.C., 1985, Frequency and duration of flooding of

Grove Creek near Kenansville, North Carolina, for

present and proposed restored channel conditions: U.S.

Geological Survey Water-Resources Investigations

Report 85-4298, 52 p.

Warner, J.C., and Brunner, G.W., 1998, U.S. Army Corps of

Engineers Hydrologic Engineering Center, 1998, HECRAS River Analysis System, Hydraulic Application

Guide, version 2.2, CPD-70, 283 p.

–––– 1998, U.S. Army Corps of Engineers Hydrologic Engineering Center, 1998, HEC-RAS River Analysis System, Hydraulic Reference Manual, version 2.2, CPD-69,

251 p.

White, W.A., 1970, The geomorphology of the Florida Peninsula: Tallahassee, Florida Bureau of Geology Bulletin

No. 51, 164 p.

Wolansky, R.M., 1983, Hydrogeology of the Sarasota-Port

Charlotte area Florida: U.S. Geological Survey WaterResources Investigations Report 82-4089, 48 p.

Figure 42. Estimated total inundated area along the Alafia, North Prong Alafia, and South Prong Alafia Rivers for 

existing conditions and for a potential 10-percent discharge withdrawal, and percentage of inundated area 

decreased by a potential 10-percent discharge withdrawal for each of the selected percentile discharges.
Appendices A-T 73

APPENDICES A-T
74 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

Appendix A. Extent of inundation at Cypress Creek cross 

sections for selected percentile discharges

Cross 

section

Percentiles

P50 P70 P80 P90 P98 P99.5 P99.9

Feet

Mouth

1 6,475 7,802 7,840 7,889 7,964 8,012 8,049

2 3,002 3,966 4,231 4,482 4,828 4,989 5,072

4 2,468 2,823 2,959 3,122 3,344 3,502 3,638

6 854 1,293 1,661 2,005 2,861 3,225 3,288

6.1 112 127 130 134 214 385 507

6.2 289 608 773 1,035 1,732 2,025 2,269

7 151 360 471 616 746 1,088 1,227

8 171 277 344 447 1,049 1,225 1,531

9 142 177 197 223 254 886 1,073

9.1 SR 581 Bridge-Cypress Creek near Sulphur Springs Gage

9.2 142 178 197 224 255 895 1,123

9.5 224 479 594 729 855 1,026 1,560

10 387 641 751 900 1,165 1,379 1,548

12 2,372 3,777 4,200 4,629 5,310 5,575 5,808

14 46.0 732 994 1,275 1,707 3,012 3,320

15 104 319 647 1,227 1,945 2,448 2,808

16 85.8 98.7 105 114 132 147 159

17 276 746 1,113 1,416 1,959 2,280 2,395

18 26.4 42.2 444 868 1,296 1,353 1,427

20 24.0 38.6 112 479 4,682 5,811 5,948

22 183 608 1,455 2,372 5,607 5,750 5,944

24 33.5 514 939 2,112 4,279 4,695 4,772

26 35.1 39.3 365 1,888 3,125 3,817 4,306

28 34.5 71.1 936 1,721 4,371 5,015 5,617

30 34.1 38.0 169 1,882 3,783 5,050 5,675

32 66.2 80.5 90.7 103 1,117 1,716 1,949

33 37.8 40.6 42.6 45.2 49.3 56.3 63.2

33.1 39.6 43.6 46.5 49.8 54.6 89.9 116

33.2 Interstate 75 Bridge (Hillsborough County)

33.25 39.8 43.8 46.7 49.9 54.9 95.0 121

33.3 42.3 48.3 52.7 56.6 64.2 96.4 111

34 49.2 52.8 55.4 58.3 75.5 105 275

36 27.7 31.2 33.9 37.9 51.5 63.3 118

37 17.5 21.8 24.5 30.8 106 256 394

37.1 12.5 13.6 14.4 22.8 52.4 148 310

37.2 Hillsborough-Pasco County Line Bridge

37.3 12.6 13.7 14.5 25.0 61.3 155 328

38 31.7 45.3 55.7 64.8 71.6 74.5 77.0

39 37.3 39.0 40.3 49.4 73.9 90.8 154

40 88.2 93.7 97.9 111 207 537 829

42 28.2 30.7 32.6 35.7 252 1,047 1,205

44 41.2 42.6 43.8 46.0 57.8 1,368 1,481

46 26.5 27.0 27.4 28.3 200 1,137 1,747

47 141 142 142 143 369 1,956 2,395

47.1 68.6 73.6 74.6 76.8 154 801 1,433

47.2 Interstate 75 Bridge (Pasco County)

47.3 66.8 69.9 72.6 76.1 183 936 1,593

48 60.2 60.7 61.5 63.0 134 1,548 2,200

49 57.1 59.3 68.3 82.5 183 793 990

50 66.0 81.4 91.9 101 122 244 290

50.5 37.6 43.5 47.5 62.7 111 241 254

51 59.4 67.8 71.3 76.7 85.6 91.2 95.6

51.5 SR 54 Bridge-Cypress Creek at Worthington Gardens Gage

51.6 64.0 72.1 74.4 78.1 85.8 91.5 96.0

52 55.0 58.4 62.2 71.3 188 291 376

53 51.1 63.1 73.1 84.6 110 150 219

53.1 41.3 50.1 55.9 59.0 65.9 77.9 111

53.2 Arch Bridge

53.3 41.3 50.4 55.9 59.1 65.9 78.5 112.3

53.4 38.3 56.3 66.6 71.9 83.2 100.2 138.3

54 23.7 82.7 338 531 691 810 1,014

55 217 1,223 2,205 3,766 4,836 4,923 4,987

56 26.4 159.4 3,36 1,285 2,254 3,148 3,300

57 27.1 28.7 726 1,426 3,802 4,276 4,546

58 26.4 28.6 327 607 1,056 1,476 1,720

60 290 504 562 638 1,023 2,984 3,126

62 25.2 26.5 28.2 261 2,508 2,944 3,060

64 38.8 2,053 2,306 2,681 2,765 2,812 2,876

66 1,103 1,991 2,399 2,697 4,838 5,177 5,966

68 33.7 33.6 35.4 38.4 1,168 1,226 1,290

70 37.8 1,661 1,701 1,769 2,169 2,267 2,355

72 1,433 1,511 1,558 5,331 5,676 5,955 6,178

74 35.2 38.0 976 2,575 3,715 3,973 4,236

76 37.9 712 1,387 2,278 3,782 6,846 6,951

78 34.1 1,579 2,019 2,587 4,666 5,149 5,562

80 57.4 80.1 95.9 148 248 357 468

80.1 137 145 149 157 177 255 367

80.2 Surface-Water Control Structure at Cypress Creek Wellfield

80.3 138 147 153 165 401 841 3,558

80.8 60.2 60.4 60.5 60.7 61.1 61.5 62.0

81 6.0 6.0 6.0 61.0 61.0 61.0 61.0

81.5 140 153 168 252 469 967 3,815

82 140 153 168 252 471 973 3,824

84 31.9 33.9 35.7 39.0 846 1,397 1,985

85 37.1 700 1,195 1,808 2,079 3,002 3,654

86 33.6 38.2 2,471 3,793 4,655 5,393 6,504

88 38.4 1,902 2,889 3,878 5,233 5,376 5,449

90 35.9 195 694 1,445 2,029 2,455 3,057

92 64.4 422 504 597 775 941 1,107

94 142.4 159 171 196 240 267 293

94.5 15.6 30.2 37.0 44.8 57.7 62.9 70.7

95 66.0 76.2 84.3 97.5 134 174 223

96 26.4 31.9 38.9 145.4 273 349 426

97 31.5 55.2 61.9 77.2 137 220 318

98 43.2 49.8 54.8 96.0 338 516 737

99 38.2 45.5 46.1 48.1 82.6 230 786

100 SR 52 Culvert--Cypress Creek near San Antonio Gage

Mean 267 489 667 961 1,479 1,864 2,164

Maximum 6,475 7,802 7,840 7,889 7,964 8,012 8,049

Minimum 6.0 6.0 6.0 22.8 49.3 56.3 61.0

Appendix A. Extent of inundation at Cypress Creek cross 

sections for selected percentile discharges (Continued)

Cross 

section

Percentiles

P50 P70 P80 P90 P98 P99.5 P99.9

Feet
Appendices 75

Appendix B. Hydraulic depth at Cypress Creek

cross sections for selected percentile discharges

Cross 

section

Percentiles

P50 P70 P80 P90 P98 P99.5 P99.9

Feet

Mouth

1 1.80 2.49 2.96 3.51 4.35 4.79 5.05

2 1.42 2.05 2.39 2.81 3.47 3.82 4.05

4 1.53 2.37 2.73 3.15 3.81 4.13 4.29

6 1.31 1.77 1.80 2.02 2.26 2.51 2.81

6.1 2.75 3.47 3.87 4.33 3.33 2.24 2.00

6.2 2.83 2.17 2.13 2.10 2.05 2.25 2.36

7 1.36 1.32 1.44 1.61 2.22 2.00 2.15

8 2.30 2.30 2.28 2.28 1.65 2.01 1.96

9 2.60 3.06 3.22 3.49 4.27 4.88 4.12

9.1 SR 581 Bridge-Cypress Creek near Sulphur Springs Gage

9.2 2.60 3.06 3.22 3.49 4.29 4.93 4.04

9.5 2.12 1.77 1.84 2.04 2.70 2.81 1.97

10 1.05 1.52 1.73 2.00 2.49 2.74 2.98

12 0.59 1.27 1.61 2.08 2.88 3.50 3.97

14 0.82 0.51 0.83 1.24 2.00 1.70 2.17

15 0.52 0.48 0.50 0.66 1.24 1.64 2.00

16 0.46 0.90 1.21 1.59 2.27 2.69 3.02

17 0.10 0.33 0.51 0.86 1.50 1.97 2.45

18 1.13 1.35 0.29 0.41 0.92 1.50 1.94

20 0.40 1.06 0.66 0.63 0.45 0.78 1.18

22 0.29 0.52 0.59 0.93 1.14 1.58 1.96

24 0.73 0.35 0.50 0.62 1.10 1.51 1.98

26 0.95 1.64 0.39 0.41 0.87 1.21 1.56

28 0.67 0.82 0.37 0.71 0.91 1.32 1.67

30 0.81 1.51 0.53 0.32 0.81 1.10 1.48

32 0.87 1.52 1.93 2.43 0.72 0.97 1.38

33 0.75 1.55 2.09 2.77 3.76 4.04 4.22

33.1 0.72 1.49 2.01 2.70 3.73 2.96 2.97

33.2 Interstate 75 Bridge (Hillsborough County)

33.25 0.74 1.50 2.03 2.72 3.78 2.91 3.01

33.3 0.92 1.63 2.11 2.80 3.80 3.38 3.78

34 0.97 1.77 2.34 3.11 3.73 3.76 2.04

36 0.68 1.48 2.05 2.85 3.89 4.59 3.35

37 1.18 1.86 2.38 2.98 2.17 2.06 2.52

37.1 1.41 2.29 2.93 2.77 2.90 2.19 3.33

37.2 Hillsborough-Pasco County Line Bridge

37.3 1.44 2.36 3.02 2.70 2.63 2.23 3.45

38 1.12 1.72 2.17 3.14 5.15 6.57 7.76

39 1.53 2.54 3.29 3.89 4.60 5.24 4.28

40 1.56 2.54 3.27 4.15 3.76 2.60 2.94

42 0.59 1.63 2.37 3.49 1.08 1.34 2.56

44 0.75 1.53 2.27 3.49 5.04 0.43 1.58

46 0.68 1.44 2.08 3.28 1.07 1.39 1.68

47 0.43 0.94 1.42 2.41 2.27 1.37 2.00

47.1 0.51 0.97 1.43 2.36 4.12 3.16 3.88

47.2 Interstate 75 Bridge (Pasco County)

47.3 0.66 1.18 1.62 2.49 3.92 3.29 4.08

48 0.11 0.38 0.85 1.75 2.31 0.99 1.84

49 0.87 1.53 1.85 2.31 2.45 1.50 2.00

50 0.70 1.27 1.71 2.44 3.95 4.95 5.60

50.5 1.03 1.69 2.19 2.48 3.05 2.78 3.92

51 0.98 1.69 2.26 3.10 4.91 6.23 7.24

51.5 SR 54 Bridge-Cypress Creek at Worthington Gardens Gage

51.6 0.97 1.70 2.31 3.22 5.08 6.41 7.44

52 1.12 1.90 2.44 3.11 2.42 2.95 3.50

53 1.17 1.73 2.13 2.82 4.19 4.42 4.26

53.1 1.17 1.76 2.23 3.14 4.97 5.70 6.35

53.2 Arch Bridge

53.3 1.18 1.76 2.24 3.15 4.98 5.67 6.38

53.4 1.10 1.48 1.89 2.76 4.51 5.25 4.97

54 0.92 0.95 0.63 1.32 2.92 4.10 4.51

55 0.23 0.42 0.66 1.14 2.97 4.64 6.01

56 0.82 0.39 0.51 0.60 2.24 3.03 4.30

57 0.99 1.74 0.28 0.66 1.77 3.20 4.55

58 0.49 1.26 0.39 0.60 1.60 2.14 3.12

60 0.22 0.57 0.99 1.48 1.75 1.48 2.55

62 0.19 0.40 0.64 0.33 0.62 1.27 2.17

64 0.78 0.22 0.36 0.60 1.20 1.70 2.39

66 0.12 0.28 0.38 0.58 0.82 1.25 1.67

68 0.35 0.34 0.49 0.75 0.26 0.34 0.45

70 0.70 0.24 0.42 0.71 1.05 1.44 1.78

72 0.12 0.47 0.66 0.30 0.82 1.21 1.57

74 0.48 0.71 0.10 0.29 0.57 0.90 1.21

76 0.70 0.19 0.30 0.39 0.58 0.55 0.82

78 0.66 0.25 0.41 0.59 0.72 0.98 1.19

80 0.36 0.53 0.61 0.66 0.87 0.95 1.08

80.1 0.53 0.84 1.03 1.33 1.86 1.97 2.32

80.2 Surface-Water Control Structure at Cypress Creek Wellfield

80.3 0.57 0.93 1.20 1.64 2.40 3.52 4.76

80.8 0.58 0.97 1.26 1.75 2.91 4.00 5.19

81 0.53 0.81 0.24 0.40 1.05 2.21 3.44

81.5 0.61 1.15 1.61 1.55 1.77 2.51 3.74

82 0.61 1.15 1.61 1.55 1.33 1.40 1.09

84 0.11 0.24 0.35 0.53 0.25 0.53 1.31

85 0.51 0.09 0.22 0.36 0.75 0.77 0.85

86 0.33 0.72 0.07 0.19 0.45 0.67 0.80

88 0.71 0.19 0.29 0.40 0.61 0.85 1.11

90 0.53 0.21 0.19 0.27 0.56 0.74 0.86

92 0.26 0.23 0.36 0.50 0.73 0.91 1.08

94 0.20 0.31 0.45 0.64 1.04 1.35 1.63

94.5 0.19 0.26 0.34 0.48 0.80 1.10 1.37

95 0.56 0.86 1.03 1.31 1.66 1.85 1.99

96 0.09 0.42 0.77 0.60 1.15 1.67 2.16

97 0.65 1.08 1.32 1.60 1.66 1.69 1.88

98 0.65 1.22 1.58 1.45 1.23 1.59 1.85

99 0.07 0.62 1.09 1.82 2.02 2.16 3.07

100 SR 52 Culvert--Cypress Creek near San Antonio Gage

Mean 0.85 1.22 1.41 1.79 2.28 2.49 2.89

Maximum 2.83 3.47 3.87 4.33 5.15 6.57 7.76

Minimum 0.07 0.09 0.07 0.19 0.25 0.34 0.45

Appendix B. Hydraulic depth at Cypress Creek

cross sections for selected percentile discharges (Continued)

Cross 

section

Percentiles

P50 P70 P80 P90 P98 P99.5 P99.9

Feet
76 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

Appendix C. Acreage of areal inundation between adjacent 

Cypress Creek cross sections 

Cross 

section

Percentiles

P50 P70 P80 P90 P98 P99.5 P99.9

Acres

1 Mouth

2 420 520 534 548 567 576 582

4 204 254 269 284 305 317 326

6 106 131 144 158 186 200 206

6.1 2.8 4.1 5.1 6.1 8.8 10.4 10.9

6.2 0.9 1.4 1.7 2.2 3.5 4.3 5.0

7 9.5 19.7 24.9 32.7 48.9 60.8 68.1

8 2.4 4.7 6.0 7.7 13.2 17.5 20.6

9 0.2 0.3 0.4 0.5 0.9 1.4 1.8

9.1 SR 581 Bridge-Cypress Creek near Sulphur Springs Gage

9.2 0.6 0.8 0.9 1.0 1.2 4.1 5.0

9.5 0.4 0.6 0.8 0.9 1.1 1.9 2.6

10 9.9 18.2 21.9 26.4 32.8 38.9 49.8

12 108 170 190 212 247 266 281

14 86.4 158 182 206 244 293 311

15 5.2 36.5 57.0 87.0 127.0 190 213

16 0.4 1.0 1.7 3.1 4.8 6.0 6.8

17 0.8 1.9 2.8 3.5 4.8 5.6 5.9

18 5.5 14.2 28.1 41.3 58.9 66.0 69.5

20 1.9 3.0 17.3 41.0 176 210 216

22 4.9 15.1 37.3 68.8 214 237 244

24 7.2 35.4 74.7 141 318 337 345

26 2.1 15.0 34.9 105 195 226 242

28 3.0 4.5 45.2 130 266 309 344

30 2.0 3.2 29.4 91.2 209 260 291

32 3.8 4.5 7.9 50.4 115 157 177

33 1.4 1.7 1.8 2.1 11.5 18.8 21.5

33.1 0.1 0.2 0.2 0.2 0.2 0.3 0.3

33.2 Interstate 75 Bridge (Hillsborough County)

33.25 0.1 0.1 0.1 0.1 0.1 0.2 0.3

33.3 0.2 0.2 0.2 0.3 0.3 0.4 0.5

34 1.3 1.4 1.5 1.6 1.9 2.6 3.4

36 3.1 3.4 3.6 3.9 4.8 5.9 10.2

37 1.4 1.6 1.8 2.1 4.1 7.2 10.8

37.1 0.1 0.1 0.1 0.1 0.4 0.8 1.4

37.2 Hillsborough-Pasco County Line Bridge

37.3 0.0 0.0 0.0 0.0 0.1 0.2 0.3

38 0.1 0.1 0.2 0.2 0.3 0.4 0.7

39 0.1 0.1 0.2 0.2 0.3 0.3 0.4

40 1.3 1.4 1.4 1.7 2.8 5.9 9.0

42 3.7 4.0 4.2 4.7 12.7 40.0 51.5

44 2.4 2.5 2.6 2.8 8.5 58.7 65.6

46 2.3 2.4 2.4 2.5 8.6 78.4 93.8

47 5.1 5.2 5.2 5.3 13.1 66.2 89.1

47.1 0.2 0.2 0.2 0.3 0.6 3.2 4.4

47.2 Interstate 75 Bridge (Pasco County)

47.3 0.3 0.3 0.3 0.3 0.8 4.0 6.9

48 0.1 0.2 0.2 0.2 0.4 2.8 4.4

49 2.2 2.2 2.4 2.7 5.3 31.4 42.9

50 2.3 2.6 3.0 3.4 5.2 14.6 17.7

50.5 2.7 3.3 3.7 4.2 5.8 11.5 12.8

51 0.1 0.1 0.1 0.2 0.2 0.3 0.4

51.5 SR 54 Bridge-Cypress Creek at Worthington Gardens Gage

51.6 0.1 0.1 0.1 0.1 0.2 0.1 0.2

52 0.1 0.2 0.1 0.2 0.3 0.4 0.6

53 0.5 0.6 0.6 0.7 1.3 1.9 2.6

53.1 0.1 0.1 0.1 0.1 0.2 0.2 0.3

53.2 Arch Bridge

53.3 0.0 0.1 0.1 0.1 0.1 0.1 0.1

53.4 0.0 0.1 0.1 0.1 0.1 0.1 0.1

54 0.4 0.7 1.9 2.8 3.5 4.1 5.2

55 4.2 22.2 43.0 72.5 93.4 96.9 101

56 4.1 23.1 42.5 84.6 118.5 135 139

57 1.2 4.1 22.6 59.5 131.3 159 168

58 1.5 1.6 25.4 50.1 116.4 137 148

60 12.0 18.2 29.1 41.0 71.3 160 174

62 7.0 12.1 13.4 20.3 75.5 125 131

64 2.2 70.2 79.2 99.8 169 183 190

66 38.1 136 159 181 258 271 299

68 31.8 55.8 66.8 74.9 162 173 196

70 2.0 44.5 45.6 47.4 87.4 91.5 95

72 33.0 70.5 72.4 157 174 182 189

74 57.0 60.1 98.2 306 364 385 405

76 2.5 24.3 76.1 156 241 348 360

78 2.6 76.2 113 162 280 396 413

80 4.0 71.5 91.1 118 209 234 256

80.1 0.3 0.4 0.4 0.5 0.7 1.1 1.4

80.2 Surface-Water Control Structure at Cypress Creek Wellfield

80.3 0.1 0.1 0.1 0.1 0.2 0.4 1.6

80.8 0.0 0.1 0.1 0.0 0.1 0.2 0.8

81 0.1 0.1 0.1 0.1 0.1 0.1 0.1

81.5 0.2 0.2 0.2 0.4 0.6 1.2 4.4

82 0.5 0.5 0.6 0.9 1.6 3.3 13.2

84 7.2 7.8 8.5 11.8 50.6 90.5 219.6

85 1.3 13.4 21.2 30.8 49.4 71.0 91.0

86 1.3 13.5 62.2 91.3 112 139 172

88 2.7 60.2 172 250 317 344 380

90 2.7 73.2 124 185 252 270 292

92 3.1 18.7 36.1 61.6 84.2 102 124

94 5.5 14.4 16.7 19.6 25.2 30.0 34.8

94.5 0.3 0.3 0.3 0.4 0.5 0.5 0.6

95 0.1 0.2 0.2 0.2 0.3 0.4 0.5

96 3.2 3.7 4.2 8.2 13.6 17.4 21.6

97 1.0 1.4 1.7 3.5 6.4 8.8 11.4

98 1.1 1.6 1.8 2.6 6.6 9.9 14.0

99 0.1 0.1 0.1 0.2 0.5 0.9 1.8

100 SR 52 Culvert--Cypress Creek near San Antonio Gage

Total 1,253 2,352 3,184 4,588 6,914 8,326 9,130

Appendix C. Acreage of areal inundation between adjacent 

Cypress Creek cross sections (Continued)

Cross 

section

Percentiles

P50 P70 P80 P90 P98 P99.5 P99.9

Acres
Appendices 77

Appendix D. Decrease of inundated acreage resulting from a 

potential 10-percent discharge withdrawal at Cypress Creek 

cross sections 

[Blanks indicate no decrease in inundated acreage]

Cross 

section

Percentiles

P50 P70 P80 P90 P98 P99.5 P99.9

Acres

1 Mouth

2 4.52 3.33 1.89 2.14 2.1 1.93 1.58

4 1.68 3.57 2.18 2.45 2.34 2.78 2.37

6 0.05 2.08 1.95 2.22 1.6 1.83 1.63

6.1 0.03 0.11 0.15 0.16 0.19 0.18 0.16

6.2 0.5 0.04 0.05 0.07 0.13 0.19 0.19

7 0.15 0.86 1.09 1.25 1.11 2.31 2.22

8 0.23 0.24 0.28 0.72 0.51 2.19

9 0.01 0.01 0.06 0.03 0.27

9.1 SR 581 Bridge-Cypress Creek near Sulphur Springs Gage

9.2 0.01 0.02 0.03 0.3

9.5 0.42 0.03 0.01 0.03 0.01 0.08 0.57

10 4.43 0.83 0.64 0.75 0.65 1.6 8.19

12 3.39 5.67 2.98 3.58 3.7 4.27 4.58

14 0.4 7.31 3.3 3.97 3.49 17.93 5.62

15 0.03 4.09 4.84 3.64 4.43 22.15 5.24

16 0.06 0.08 0.24 0.14 0.21 0.28 0.13

17 0.44 0.14 0.17 0.1 0.1 0.33 0.09

18 0.03 1.16 2.39 1.99 0.88 3.06 1.09

20 0.34 0.32 3.36 3.63 20.1 1.22 1.68

22 0.48 2.15 4.84 3.58 13.28 0.97 1.28

24 0.02 4.33 8.97 11.83 3.51 1.43 1.72

26 0.03 1.39 6.11 11.34 5.29 4.29 3.28

28 1.06 7.97 9.04 6.96 8.22 8.46

30 0.04 0.81 5.9 10.27 9.26 9.26 6.64

32 0.02 0.09 1.85 8.45 6.03 6.27 4.28

33 0.02 0.02 0.03 0.36 0.64 0.69

33.1 0.01 0.02 0.02

33.2 Interstate 75 Bridge (Hillsborough County)

33.25 0.01 0.01 0.02

33.3 0.01 0.03 0.01

34 0.01 0.01 0.01 0.02 0.11 0.08 0.3

36 0.01 0.03 0.05 0.04 0.2 0.17 1.87

37 0.01 0.03 0.03 0.06 0.34 0.63 1.25

37.1 0.02 0.03 0.09 0.28

37.2 Hillsborough-Pasco County Line Bridge

37.3 0.06

38 0.01 0.02 0 0.02 0.02 0.31

39 0.01 0.01 0.02 0.01

40 0.01 0.01 0.01 0.05 0.51 0.65 0.34

42 0.03 0.04 0.1 4.29 4.22 1.56

44 0.01 0.02 0.03 3.2 31.41 1.79

46 0.01 0.02 0.01 0.02 5.83 46.54 4.68

47 0.01 0.01 6.34 19.8 6.59

47.1 0.25 0.95 0.32

47.2 Interstate 75 Bridge (Pasco County)

47.3 0.01 0.68

48 0.13 0.53 0.23

49 0.03 0.02 0.05 0.06 0.57 4.89 1.48

50 0.03 0.06 0.04 0.06 0.28 1.03 0.76

50.5 0.07 0.04 0.09 0.32 0.13 0.14

51 0.01 0.01 0.01

51.5 SR 54 Bridge-Cypress Creek at Worthington Gardens Gage

51.6 0.01

52 0.01 0.01 0.03 0.03

53 0.01 0.01 0.02 0.08 0.21 0.13

53.1 0.01 0.01 0.03 0.01

53.2 Arch Bridge

53.3 0.01 0.01 0.01

53.4 0.01 0.01

54 0.75 0.03 0.19 0.01 0.14 0.19 0.35

55 0.73 4.83 3.84 4.22 0.93 0.84 1.35

56 0.01 5.38 3.68 7.83 1.57 1.29 0.7

57 0.01 0.7 4.06 6.73 5.44 1.42 0.86

58 0.7 0.02 4.55 3.47 5.09 1.57 1.76

60 0.39 0.93 1.56 2.3 11.94 4.55 3.94

62 0.02 0.78 0.24 1.72 11.43 1.9 2

64 0.68 6.96 1.37 4.29 7.41 1.06 1.92

66 0.56 9.86 2.5 3.86 2.44 2.07 20.46

68 0.01 2.86 0.95 1.38 2.07 1.74 16.79

70 0.17 0.18 0.22 0.28 0.69 0.83 1.37

72 0.29 0.32 0.37 82.18 1.27 1.64 1.5

74 0.02 0.35 14.66 147.72 3.15 4.28 4.68

76 0.04 9.37 17.97 6.76 6.73 2.4 3.06

78 0.13 12.39 8.75 7.56 8.3 3.58 4.44

80 3.87 3.7 4.61 3.89 4.76 5.67

80.1 0.01 0.02 0.01 0.03 0.07 0.11

80.2 Surface-Water Control Structure at Cypress Creek Wellfield

80.3 0.01 0.03 0.05 0.43

80.8 0.01 0.01 0.01 0.02 0.28

81 0.01

81.5 0.01 0.01 0.01 0.06 0.22 0.82

82 0.04 0.01 0.02 0.02 0.16 0.67 2.48

84 0.01 0.1 0.19 0.32 3.64 19.69 29

85 0.01 2.18 1.21 1.4 1.2 5.42 7.15

86 0.05 2.18 2.59 2.7 2.31 3.01 14.3

88 0.03 4.24 7.1 6.76 8.01 4.75 12.55

90 0.04 7.67 7.69 7.2 8.11 3.18 1.48

92 0.08 2.9 3 1.89 2.78 3.57 1.92

94 0.2 0.29 0.4 0.69 1.04 1.19

94.5 0.01 0.02 0.01 0.01 0.02

95 0.03 0.01 0.01 0.02 0.02 0.02

96 0.02 0.06 0.12 0.56 0.5 0.76 0.89

97 0.02 0.06 0.26 0.33 0.43 0.55

98 0.01 0.03 0.04 0.3 0.56 0.53 1.17

99 0.02 0.05 0.07 0.21

100 SR 52 Culvert--Cypress Creek near San Antonio Gage

Total 22 118 152 395 210 281 233

Appendix D. Decrease of inundated acreage resulting from a 

potential 10-percent discharge withdrawal at Cypress Creek 

cross sections (Continued)

[Blanks indicate no decrease in inundated acreage]

Cross 

section

Percentiles

P50 P70 P80 P90 P98 P99.5 P99.9

Acres
78 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

Appendix E. Extent of inundation at cross sections 

along reach 1 of the Peace River for selected percentile 

discharges 

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Feet

Arcadia Gaging Station

148 121 140 174 186 628 719 2,794 4,236

150 178 189 306 520 1,391 3,553 8,284 9,586

151 99 105 215 271 1,011 2,948 6,500 7,748

152 102 155 224 281 914 2,673 4,612 4,643

154 125 146 168 205 343 2,403 6,903 6,955

156 108 121 137 151 241 3,458 9,187 9,251

158 111 120 128 203 483 4,145 6,458 6,568

160 138 155 178 196 426 2,545 6,468 6,740

161 Railroad Bridge

161.5 129 155 187 213 460 2,935 6,579 6,799

162 137 169 205 233 1,351 3,863 5,055 5,241

164 129 152 209 254 396 3,106 5,185 5,225

166 107 122 136 147 725 1,302 6,175 6,298

168 85 100 120 147 1,690 3,596 6,481 6,860

170 75 86 113 181 546 1,794 3,286 3,883

172 159 167 181 195 218 656 2,945 3,269

173 82 95 137 182 453 2,986 4,253 4,591

174 122 136 161 306 1,028 2,260 3,812 4,177

176 98 112 132 149 174 1,110 3,467 3,743

178 83 101 135 164 553 1,513 4,349 4,482

180 99 121 132 271 702 1,661 4,293 4,574

182 68 86 104 122 435 1,066 3,329 3,743

184 82 103 120 135 367 2,416 4,158 4,618

186 106 133 171 216 842 2,380 2,791 2,889

188 89 153 213 286 1,293 3,350 4,292 4,605

189 89 154 215 288 1,311 3,363 4,307 4,623

190 Brownwille Road Bridge

190.5 90 156 219 292 1,345 3,398 4,351 4,682

191 140 176 208 231 317 3,469 4,094 4,368

196 106 163 363 1,067 1,925 5,818 6,342 6,542

198 132 155 175 190 791 4,702 5,564 5,847

200 120 150 162 170 182 3,462 6,094 6,753

202 105 134 162 181 456 2,642 3,667 4,660

204 96 109 119 126 558 2,546 3,448 3,605

206 104 119 134 144 159 2,797 4,105 4,332

208 85 96 107 115 126 2,927 4,938 5,483

210 89 109 126 139 157 721 3,426 4,067

212 86 96 108 117 207 2,484 4,948 5,052

214 104 136 169 187 347 1,135 5,002 5,382

216 84 97 118 132 468 3,053 4,549 5,184

218 58 78 105 126 194 2,055 6,542 8,915

220 78 122 318 483 1,057 3,858 6,212 8,969

222 120 149 172 619 1,329 6,683 9,684 9,983

224 110 219 348 579 1,716 5,883 7,602 8,747

226 89 114 152 331 699 5,878 8,105 8,996

228 114 129 323 773 1,419 2,615 7,692 7,772

230 78 96 112 395 893 2,127 7,427 7,883

232 82 91 101 129 179 2,660 7,149 8,624

234 86 102 117 129 150 1,571 3,842 4,642

236 84 115 131 145 168 1,378 3,256 3,843

238 95 136 166 189 325 1,103 3,018 3,643

240 100 146 197 237 429 1,237 2,599 2,936

242 73 89 106 688 2,310 2,791 4,251 5,446

244 60 70 95 113 804 2,380 2,892 3,949

246 95 110 124 174 1,738 3,326 3,759 4,660

248 98 138 200 384 783 3,514 4,987 5,370

250 93 106 150 274 1,755 4,110 5,739 5,889

252 88 121 144 161 189 4,071 8,314 8,477

254 107 137 148 156 171 4,268 5,125 5,359

256 75 108 137 160 825 2,166 2,621 2,720

258 71 100 133 194 405 2,198 2,705 3,113

260 63 94 126 148 182 1,549 3,797 4,833

262 99 122 143 162 192 1,792 3,732 4,918

264 153 268 369 441 554 4,268 8,831 12,410

266 78 160 287 344 538 3,957 6,869 9,514

268 74 86 98 127 459 3,410 3,611 5,441

270 83 87 90 247 501 2,187 3,347 4,249

272 101 107 114 184 279 470 1,238 1,967

274 86 93 98 114 453 2,086 4,909 7,958

276 102 123 139 321 729 2,171 3,758 4,965

278 126 161 190 234 471 2,057 3,851 4,117

279 88 95 106 118 130 452 865 976

279.1 128 144 155 160 168 264 448 972

279.2 SR 64 Bridge

279.5 128 144 155 160 168 264 449 980

280 69 75 81 90 102 117 130 139

282 80 84 88 116 228 420 519 790

284 80 100 115 126 173 262 291 718

286 81 85 89 99 133 791 998 1,290

287 65 70 74 86 141 758 1,112 1,481

288 US 17 Bridge and Zolfo Spring Gaging Station

Mean 99 124 161 238 625 2,521 4,529 5,181

Maximum 178 268 369 1,067 2,310 6,683 9,684 12,410

Minimum 58 70 74 86 102 117 130 139

Appendix E. Extent of inundation at cross sections 

along reach 1 of the Peace River for selected percentile 

discharges (Continued)

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Feet
Appendices 79

Appendix F. Hydraulic depth at cross sections along 

reach 1 of the Peace River for selected percentile 

discharges 

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Feet

Arcadia Gaging Station

148 2.0 3 4 5.3 3.8 7.2 3.1 2.9

150 2.2 3.4 3.7 3.4 3.4 4.4 3.7 4.2

151 2.2 3.5 3.2 4 3 4 3.8 4.2

152 2.0 2.4 3.2 4 2.4 3.7 4.7 5.7

154 1.9 3.3 4.6 5.1 5.2 2.6 3.1 4.2

156 2.1 3.6 5 6 5.8 1.3 2.8 4

158 2.2 3.9 5.5 4.7 3.8 1.8 3.8 4.9

160 2.2 3.8 5.2 6.2 7.9 5.2 5.3 6.1

161 Railroad Bridge

161.5 2.1 3.5 4.7 5.7 7.2 4.3 5.8 6.9

162 2.0 3.3 4.6 5.6 2.1 3.9 5.7 6.6

164 2.0 3.5 4.3 5 5.4 1.9 3.9 5

166 2.1 3.7 5.3 6.4 3.3 5.5 2.5 3.7

168 2.1 3.8 5 5.6 1.8 4 4.5 5.5

170 2.5 4.2 5.1 4.5 3.3 3.1 4.1 4.6

172 2.6 4.8 6.6 7.9 9.7 5.4 3.1 4.1

173 2.1 4 4.8 5.2 4 2.5 4.8 5.9

174 1.9 3.9 5.7 4.3 3.2 4.5 5.5 6.5

176 1.3 3.3 5.5 7 9.1 2.9 3.2 4.4

178 1.2 2.6 4.4 5.7 3.2 3.5 3.6 5

180 1.1 2.2 4.1 3.4 3.6 5.5 4.7 5.8

182 1.6 2.9 4 5.1 2.6 3.7 3.4 4.4

184 1.8 3.4 5 6.3 4.6 2.3 4.2 5.1

186 1.8 3.6 5.1 5.9 2.9 4.9 7.4 8.5

188 1.7 3.5 5 5.6 7.6 6.5 9.9 11.5

189 1.7 3.5 5 5.6 7.7 6.5 10 11.6

190 Brownwille Road Bridge

190.5 1.9 3.7 5.1 5.7 7.8 6.7 10.2 12

191 2.1 4.6 6.6 7.9 8.1 3.7 6.5 7.7

196 2.3 3.9 3.7 2.5 3.6 3.6 6.8 8.3

198 2.1 4.7 6.9 8.4 3.4 2.3 5.3 6.8

200 2.0 4.6 7.1 8.8 11 1.8 4 5.2

202 2.2 4.5 6.4 7.7 5.1 3.2 5.2 5.6

204 1.9 4.6 7 8.7 3.2 2.6 5.2 6.7

206 2.1 4.6 6.9 8.4 10.5 2.5 5 6.5

208 1.6 4.1 6.4 8 10.2 2.4 4.4 5.7

210 1.8 3.9 6 7.5 9.5 3.5 3.6 4.7

212 1.6 3.7 5.9 7.5 6.1 2.5 4.2 5.8

214 1.8 3.4 5.3 6.7 5.8 4.6 3.7 5.2

216 1.7 3.5 5.5 6.9 3.6 2.8 4.9 6

218 1.8 3.2 4.7 5.8 6.1 2.3 3.4 3.9

220 1.1 2.1 2.4 3.1 3.5 3.4 4.7 4.7

222 1.1 2.2 3.6 2 3.2 2.9 4.9 6.5

224 1.2 1.6 2.2 2.6 2.8 3.1 5.3 6.4

226 1.2 2.1 2.7 2.3 3 2 4.2 5.6

228 1.2 2.3 1.7 1.7 3 4.6 3.9 5.7

230 1.5 2.5 3.3 1.6 2.3 4.1 3.6 5.2

232 1.7 3 3.9 4.1 4.7 1.9 2.5 3.8

234 2.2 3.4 4.3 5 6.2 2.5 2.9 4.1

236 1.4 2.5 3.5 4.3 5.7 2.8 3.2 4.4

238 1.4 2.9 3.8 4.4 4.1 3.6 3.1 4.2

240 1.2 2.6 3.3 3.8 3.5 3.8 3.8 5.1

242 1.4 2.8 3.8 0.8 1.6 4.8 5.3 5.9

244 1.6 3 3.6 4 1.5 2.8 4.8 5.3

246 1.6 3.1 4.2 3.9 1.4 3.3 5.5 6.1

248 1.0 2.1 2.7 2.2 2.3 2.8 4.2 5.8

250 1.2 2.2 2.6 2.2 1.2 2.8 4.4 6.2

252 1.1 1.9 2.6 3.2 4.2 1.4 2.9 4.7

254 1.2 2.1 3 3.7 4.8 1.3 3.1 4.7

256 1.4 2.1 2.6 3 1.3 2.2 3.6 5.2

258 1.4 2.3 2.7 2.6 2.2 1.7 3.2 4.4

260 1.7 2.6 3 3.4 4 1.2 1.7 2.8

262 1.8 3.1 4 4.4 5.1 1.4 1.8 2.6

264 1.4 2.2 2.8 3.3 4 1.7 2.1 2.5

266 2.3 2.6 2.4 2.9 3.2 1.5 2.1 2.7

268 2.1 3.7 4.7 5.1 2.5 2 3.7 3.7

270 1.4 3.3 4.7 2.9 2.5 2.1 2.7 3.5

272 1.8 3.6 5 4.3 4.2 5.1 2.8 3.1

274 1.9 3.7 5.1 5.7 2.7 2.7 2.2 2.7

276 1.9 3.4 4.5 3.4 2.5 3.5 3.2 4

278 1.7 3.1 4.2 4.7 4 2.3 3 4.5

279 2.0 3.7 4.9 5.6 6.9 5.4 3.5 4.7

279.1 1.4 3.1 4.4 5.5 7.2 7.0 7.2 7.9

279.2 SR 64 Bridge

279.5 1.5 3.2 4.5 5.6 7.3 7.2 7.3 8.4

280 2.1 3.8 5.1 6.0 7 9.3 10.7 11.7

282 2.0 3.8 5.2 6.0 4.3 4.8 5.2 5.6

284 1.4 2.9 4.0 4.9 5.4 6.4 8.1 4.9

286 1.7 3.4 4.8 5.7 6.1 2.9 4.8 5.6

287 1.7 3.3 4.6 5.4 5 7.5 6.0 6.3

288 US 17 Bridge and Zolfo Spring Gaging Station

Mean 1.7 3.3 4.4 4.9 4.6 3.6 4.5 5.4

Maximum 2.6 4.8 7.1 8.8 11 9.3 10.7 12

Minimum 1.0 1.6 1.7 0.8 1.2 1.2 1.7 2.5

Appendix F. Hydraulic depth at cross sections along 

reach 1 of the Peace River for selected percentile 

discharges (Continued)

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Feet
80 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

Appendix G. Acreage of areal inundation between adjacent 

cross sections along reach 1 of the Peace River 

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Acres

148 Arcadia Gaging Station

150 0.9 0.9 1.4 2.2 5.8 13.2 31.2 37.8 

151 4.0 4.3 7.6 11.6 32.5 92.5 197.8 227.2 

152 3.1 4.0 6.7 8.4 28.9 84.1 166.0 185.1 

154 7.3 8.7 10.5 12.3 21.8 68.2 150.7 151.8 

156 6.4 7.3 8.4 9.7 15.8 153.0 417.2 420.1 

158 7.6 8.3 9.2 11.7 22.2 212.1 434.0 439.0 

160 1.7 1.8 2.1 2.7 6.1 44.9 86.8 89.4 

161 Railroad Bridge

161.5 0.3 0.4 0.4 0.5 0.8 3.9 8.8 9.1 

162 0.2 0.2 0.3 0.3 1.5 5.7 9.3 9.5 

164 5.7 6.9 8.8 10.4 30.2 110.9 162.0 166.4 

166 9.0 10.4 13.1 15.2 41.0 150.0 374.3 379.8 

168 5.7 6.6 7.7 8.8 58.8 116.6 300.6 312.5 

170 5.9 6.9 8.6 11.6 64.3 150.3 275.0 302.8 

172 7.0 7.6 8.8 11.3 22.7 72.4 181.9 207.0 

173 7.8 8.4 10.2 12.1 19.7 95.5 192.7 209.2 

174 7.3 8.2 10.6 17.1 49.9 139.4 191.1 207.2 

176 7.8 8.8 10.4 14.9 34.4 100.5 232.9 252.9 

178 5.2 6.1 7.6 9.0 18.9 62.9 182.3 191.8 

180 5.4 6.6 8.0 11.5 27.3 58.3 116.9 121.5 

182 5.4 6.6 7.6 11.0 28.7 65.9 204.2 223.0 

184 4.5 5.6 6.7 7.7 22.7 94.0 189.8 211.3 

186 5.2 6.5 8.0 9.6 29.8 119.4 177.7 192.9 

188 5.8 8.5 11.5 14.9 58.7 156.0 191.9 202.8 

189 0.2 0.3 0.5 0.7 1.9 7.0 9.2 9.9 

190 Brownwille Road Bridge

190.5 0.3 0.5 0.8 1.0 4.6 11.6 14.9 16.0 

191 1.2 1.7 2.2 2.7 6.5 29.0 35.5 37.8 

196 8.5 11.4 18.2 33.5 54.8 229.5 257.5 269.1 

198 6.3 8.2 13.0 31.9 71.9 242.8 276.2 288.2 

200 6.9 8.4 9.3 9.9 25.0 227.9 330.6 357.9 

202 6.2 7.8 8.9 9.7 16.1 142.3 223.0 259.3 

204 6.0 7.3 8.4 9.2 30.8 156.4 215.6 251.1 

206 9.2 10.5 11.6 12.4 25.6 182.8 243.8 255.3 

208 5.6 6.4 7.2 7.8 8.5 170.8 269.9 292.9 

210 5.8 6.8 7.8 8.4 9.4 107.9 230.7 263.0 

212 8.0 9.4 10.7 11.7 15.8 120.8 337.6 365.4 

214 6.6 8.0 9.5 10.5 18.5 112.7 300.1 315.3 

216 6.5 8.1 9.9 11.0 24.9 117.9 265.7 293.7 

218 4.1 5.0 6.4 7.4 17.6 146.3 306.9 381.5 

220 4.7 6.9 14.6 21.0 40.5 171.5 356.4 492.5 

222 6.5 8.9 16.0 33.4 66.8 282.6 427.5 512.5 

224 7.0 11.2 15.8 33.9 79.7 298.5 405.3 437.4 

226 4.3 7.3 10.8 19.1 46.2 221.1 294.4 333.7 

228 7.5 9.0 16.2 35.3 65.8 255.9 474.3 503.7 

230 5.3 6.2 11.0 27.6 53.5 108.8 341.0 353.0 

232 4.6 5.4 6.1 13.3 27.7 119.0 368.7 418.4 

234 5.8 6.6 7.5 8.9 11.3 110.7 280.1 334.8 

236 3.9 5.0 5.7 6.3 7.3 56.2 134.7 161.0 

238 7.4 10.4 12.3 13.8 19.4 80.8 193.8 230.4 

240 2.4 3.6 4.6 5.4 9.2 27.3 63.5 74.2 

242 5.8 7.6 9.4 23.8 71.5 101.2 164.8 199.4 

244 3.8 4.6 5.8 18.7 66.5 108.7 150.5 198.2 

246 5.2 6.0 7.3 9.3 71.6 131.1 156.4 209.8 

248 5.5 7.1 8.9 14.1 56.9 151.1 192.7 220.7 

250 5.5 7.0 9.1 15.2 53.0 147.7 211.0 221.6 

252 5.4 6.8 8.7 12.5 52.8 222.7 379.4 387.9 

254 7.2 9.5 10.7 11.6 13.2 130.4 199.8 207.1 

256 4.0 5.3 6.2 6.9 26.0 177.2 207.1 214.4 

258 4.7 6.7 8.7 11.2 40.0 142.7 172.3 188.7 

260 5.2 7.6 10.1 12.8 19.3 90.9 150.2 181.5 

262 4.9 6.4 8.0 9.2 11.2 90.0 196.7 253.7 

264 7.5 11.7 15.3 18.0 22.3 122.7 247.2 343.4 

266 7.2 13.3 19.2 22.7 31.1 184.2 341.3 464.4 

268 5.1 8.2 12.1 14.3 25.0 169.3 237.6 330.2 

270 3.6 4.0 4.3 7.3 16.3 81.7 101.3 142.1 

272 6.9 7.3 7.7 12.8 20.7 57.3 94.0 124.6 

274 6.2 6.6 7.1 10.0 23.5 83.9 186.9 278.3 

276 5.4 6.2 6.8 13.1 34.8 108.7 223.1 358.4 

278 6.6 8.1 9.4 16.5 36.5 112.5 197.0 238.3 

279 3.6 4.3 4.9 5.9 10.0 41.8 78.5 84.8 

279.1 0.5 0.6 0.6 0.6 0.7 1.6 3.0 4.5 

279.2 SR 64 Bridge

279.5 0.2 0.3 0.3 0.3 0.3 0.5 0.8 1.8 

280 0.2 0.3 0.3 0.3 0.3 0.4 0.7 1.3 

282 1.1 1.2 1.3 1.5 2.6 4.4 5.3 6.8 

284 1.3 1.5 1.6 2.0 3.2 5.5 6.5 12.1 

286 4.2 4.9 5.4 5.9 8.0 25.0 30.7 48.2 

287 0.8 0.9 0.9 1.1 1.6 11.3 14.4 16.5 

288 US 17 Bridge and Zolfo Spring Gaging Station

Total 377 474 609 888 2,120 8,412 15,081 17,196

Appendix G. Acreage of areal inundation between adjacent 

cross sections along reach 1 of the Peace River (Continued)

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Acres
Appendices 81

Appendix H. Decrease of inundated acreage resulting from 

a potential 10-percent discharge withdrawal at cross sections 

along reach 1 of the Peace River 

[Blanks indicate no decrease in inundated acreage]

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Acres

148 Arcadia Gaging Station

150 0.01 0.2 0.6 0.8 4.9 1.4

151 0.02 0.4 1 4.2 7 35.5 4

152 0.05 0.4 0.4 10.4 6.7 22.5 2.3

154 0.04 0.03 0.3 0.6 6.5 6.3 0.5 0.4

156 0.05 0.69 0.2 0.4 2.7 63 3.4 1

158 0.57 0.2 0.6 3.9 118.7 4.6 1.6

160 0.11 0.2 1.2 19.1 1.4 1

161 0.18 0.08

161.5 0.01 0.02 1.5 0.01 0.8 0.2 0.1

162 0.07 0.5 0.8 0.1

164 0.08 0.4 0.4 7.3 23.9 1.5 0.5

166 0.06 0.02 0.4 0.6 5 43 30 1.6

168 0.05 0.15 0.3 0.3 8.6 10.9 43.3 2

170 0.01 0.19 0.4 0.8 10.9 27.8 28.3 5.1

172 0.04 0.09 0.3 0.6 2.3 25.9 6.9 6

173 0.06 0.14 0.5 0.6 1.7 21.8 6.0 5.9

174 0.05 0.08 0.5 2.7 5.8 19 4.1 4.7

176 0.04 0.07 0.3 2 3.4 14.2 15.9 6.2

178 0.06 0.1 0.4 0.3 0.7 17.6 9.1 3.5

180 0.07 0.11 0.3 1.6 2.1 7.1 1.7 1.6

182 0.06 0.11 0.1 1.7 9.8 5.6 15.2 7.1

184 0.05 0.11 0.2 0.2 6.9 24.2 15 6.7

186 0.08 0.11 0.2 0.7 6 22.9 6.3 3.2

188 0.11 0.6 1 30.7 8.1 3.8 3.9

189 0.18 1.1 0.4 0.2 0.3

161 Railroad Bridge

190.5 0.02 0.01 0.1 3.3 0.6 0.4 0.4

191 0.1 0.1 0.2 3.1 1.9 0.8 0.9

196 0.04 2.0 6.5 7.1 16.6 4.0 4.1

198 0.15 0.06 1.6 12.5 11.6 26.5 4.0 3.9

200 0.17 0.5 0.2 0.2 3.8 25.5 12.1 11.3

202 0.08 0.35 0.1 0.2 0.7 14.4 14.4 19

204 0.15 0.11 0.1 0.1 2.6 44.2 12 19.7

206 0.06 0.14 0.2 0.2 1.8 52.2 3.5 4.4

208 0.07 0.13 0.2 0.2 0.2 37 7.6 7.3

210 0.11 0.14 0.2 0.1 0.1 16.6 10.1 10.6

212 0.06 0.1 0.1 0.3 2.3 53.6 10.2 9.7

214 0.05 0.11 0.3 0.2 3.7 31.1 5.5 5

216 0.04 0.16 0.2 0.2 4.6 7.8 7.7 6.5

218 0.09 0.2 0.3 0.3 3.7 25.1 9.4 36.8

220 0.1 0.23 1.5 1.7 4.9 35.7 28.5 73.6

222 0.15 0.16 1.3 5.8 6.8 27.8 33.8 41.8

224 0.11 0.36 1 6.2 7.7 37.5 13.4 4.8

226 0.11 0.33 1 2.2 5.5 66.2 17 3

228 0.07 0.46 2.4 4.1 5.7 85.1 19.3 1.8

230 0.04 0.34 1.3 2.6 3.8 14.8 3.8 4

232 0.06 0.15 0.3 1.0 3.2 16.4 9.1 21.5

234 0.07 0.1 0.2 0.4 0.7 14.7 12.1 20.5

236 0.13 0.09 0.1 0.1 0.2 6.7 9.3 6.8

238 0.03 0.11 0.3 0.5 1.4 10.3 11.9 8.5

240 0.04 0.1 0.3 0.2 1.4 2.5 3.4 2.2

242 0.03 0.26 0.3 13.3 5.9 3.9 14.3 11.2

244 0.05 0.15 0.2 12.3 6.1 7 12.6 12

246 0.09 0.27 0.2 1.4 7.3 6.5 4.4 14.8

248 0.08 0.1 0.3 3.0 5.5 3.3 5.6 10.2

250 0.08 0.11 0.5 2.5 8.3 6.9 4.5 1.9

252 0.22 0.19 0.4 1.3 7.3 36.6 2.6 1.3

254 0.12 0.19 0.2 0.2 0.3 23 2.1 2.2

256 0.12 0.18 0.1 0.2 5.6 20.7 2.3 1.8

258 0.13 0.19 0.4 0.6 8.5 13.2 3.8 4.7

260 0.09 0.12 0.5 0.6 1.9 11 11 5.9

262 0.18 0.29 0.2 0.4 0.4 16.5 19.6 10.7

264 0.14 0.38 0.7 0.7 0.8 21.8 21.9 52

266 0.03 0.21 0.9 1 1.9 38.8 36.8 43.3

268 0.02 0.51 0.5 0.5 2.9 32.3 23.4 21.8

270 0.02 1.17 0.1 0.8 2.3 2.7 3.8 14.9

272 0.03 0.83 1.9 1.6 3.1 14 7.7

274 0.04 0.03 0.1 1.5 2 5.3 18.5 29.3

276 0.08 0.05 1.9 2.3 6 9.5 38.4

278 0.04 0.05 0.3 1.9 3.1 17.7 5.3 8

279 0.01 0.09 0.1 0.3 1.2 12.7 1.4 1.5

279.1 0.18 0.1 0.4 0.1 0.7

279.2 SR 64 Bridge

279.5 0.01 0.1 0.1

280 0.01 0.1 0.1 0.1 1.0

282 0.02 0.2 0.3 0.2 0.5 7.5

284 0.05 0.1 0.2 0.2 0.2 1.9 7.5

286 0.02 0.1 0.2 0.5 3 5.2 4.6

287 0.02 0.1 0.2 2.2 0.6 0.4

288 US 17 Bridge and Zolfo Spring Gaging Station

Total 4.96 13.7 29.9 110 307 1,469 751 715

Appendix H. Decrease of inundated acreage resulting from 

a potential 10-percent discharge withdrawal at cross sections 

along reach 1 of the Peace River (Continued)

[Blanks indicate no decrease in inundated acreage]

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Acres
82 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

Appendix I. Extent of inundation at cross sections 

along reach 2 of the Peace River for selected percentile 

discharges 

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Feet

286 81 85 88 95 126 855 1,010 1,291

287 65 69 73 82 134 836 1,127 1,477

288 Zolfo Springs Gaging Station at US 17 Bridge

289 65 69 73 82 134 852 1,150 1,493

290 71 78 83 97 128 370 1,358 1,441

291 53 60 65 70 519 2,874 2,960 3,047

292 83 98 117 135 205 3,304 3,509 3,671

294 71 87 112 157 256 3,229 4,348 4,612

296 80 103 426 542 766 3,791 3,936 4,077

298 104 137 165 261 346 1,775 2,332 2,645

300 110 120 129 135 148 177 801 3,174

302 74 85 99 112 136 1,473 2,024 3,978

304 74 104 120 137 155 192 2,408 2,632

304.1 113 150 164 175 191 223 277 339

304.2 SR 652 Bridge at Wauchula

304.3 114 152 165 176 193 226 288 355

304.4 72 121 175 196 220 268 311 2,680

305 77 88 112 124 540 867 2,908 3,063

306 85 107 140 161 711 1,130 2,552 3,643

308 98 110 144 173 215 304 3,832 4,233

310 109 122 140 201 614 1,173 3,774 4,504

310.1 159 268 512 529 1,941 2,923 3,684 3,980

310.2 SR 64A Bridge at Wauchula

310.3 157 274 512 530 1,956 2,932 3,699 4,035

310.4 99 153 195 372 422 1,740 3,836 3,941

314 93 104 113 120 130 150 1,382 2,801

316 130 137 146 152 162 185 1,364 2,709

318 118 129 138 145 157 2,492 2,771 2,862

320 75 97 115 144 1,671 2,166 2,563 2,784

321 98 148 188 258 2,348 3,167 3,635 3,833

322 116 134 148 165 201 1,768 2,137 2,377

322.1 126 143 158 184 212 236 1,695 2,583

322.2 SR 664A Bridge near Wauchula

322.3 126 143 158 184 212 237 1,713 2,629

324 119 143 162 185 269 1,453 1,662 2,268

326 107 124 144 191 293 677 878 1,090

327 139 190 356 463 871 1,259 1,456 1,605

327.5 173 295 426 599 1,165 1,802 1,987 2,186

328 90 125 210 513 1,542 2,147 2,329 2,408

330 75 88 127 180 246 2,587 2,766 2,927

332 69 89 117 135 1,819 2,676 3,106 3,683

334 90 107 129 144 163 2,595 3,043 3,270

336 86 96 109 118 129 1,329 2,647 2,889

337 73 105 122 389 499 980 1,314 2,589

338 84 115 137 152 172 202 1,529 1,920

339 61 80 115 139 171 1,802 2,118 2,535

340 49 89 106 119 136 1,551 2,643 2,853

341 61 78 94 107 234 1,676 2,513 2,790

342 85 105 125 143 221 1,516 2,553 3,230

342.2 SR 664 Bridge at Bowling Green

343 85 105 125 144 222 1,517 2,554 3,232

343.5 30 38 53 67 174 1,541 2,191 2,541

344 37 56 72 98 226 596 2,842 3,191

346 62 78 97 169 543 1,364 3,726 4,440

348 96 134 180 263 568 2,313 3,491 4,091

350 67 89 114 197 507 1,252 2,225 3,100

352 50 68 87 101 279 1,132 2,118 2,635

354 76 92 115 128 144 755 2,131 2,365

354.1 61 67 104 156 234 308 2,133 2,338

354.2 SR 664 Bridge at Polk-Hardee Countyline

354.5 61 67 106 156 234 308 2,136 2,344

356 54 81 119 156 225 456 2,121 2,442

358 57 75 93 106 131 592 2,224 2,435

360 59 94 105 115 134 451 2,418 2,615

362 62 83 94 103 121 1,173 1,769 2,592

364 75 95 111 123 186 1,967 2,491 2,777

366 56 79 97 111 137 532 1,360 1,955

368 42 67 96 117 154 972 1,347 2,192

370 88 121 133 142 158 191 1,076 1,208

372 63 92 111 125 148 563 1,711 2,374

374 87 121 147 165 196 422 2,641 3,683

376 97 160 234 288 381 563 688 792

378 154 239 355 477 691 1,115 1,410 1,801

380 46 152 309 448 699 1,211 1,574 1,975

382 61 77 84 92 108 367 782 1,375

384 51 66 94 114 151 238 307 1,008

386 47 54 60 102 184 361 974 1,745

388 54 73 106 127 164 541 1,086 1,697

390 69 129 180 216 276 723 1,030 1,410

391 89 113 138 251 766 1,546 2,460 2,743

392 71 92 114 130 157 293 2,468 2,942

392.1 SR 657 Bridge near Fort Meade

392.5 72 98 120 137 164 1,384 2,575 2,970

393 83 89 113 129 142 167 1,489 2,482

396 86 115 278 565 1,396 2,007 2,170 2,278

398 63 141 477 726 1,319 1,485 1,570 1,716

400 82 199 323 393 579 1,162 1,383 1,644

402 64 83 96 124 896 1,438 1,557 1,697

404 58 150 286 390 550 1,355 1,635 2,026

405 61 71 79 84 170 561 1,635 1,794

406.2 95 226 347 596 744 897 1,002 1,282

406.3 68 106 137 158 711 816 923 1,041

406.4 Fort Meade Gaging Station at US 98 Bridge

Mean 82 113 159 209 448 1,209 2,063 2,542

Maximum 173 295 512 726 2,348 3,791 4,348 4,612

Minimum 30 38 53 67 108 150 277 339

Appendix I. Extent of inundation at cross sections 

along reach 2 of the Peace River for selected percentile 

discharges (Continued)

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Feet
Appendices 83

Appendix J. Hydraulic depth at cross sections along 

reach 2 of the Peace River for selected percentile 

discharges 

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Feet

286 1.7 3.3 4.7 5.6 6.1 2.9 4.7 5.7

287 1.7 3.2 4.5 5.3 5 7.8 5.1 6.6

288 Zolfo Springs Gaging Station at US 17 Bridge

289 1.6 3.2 4.5 5.3 4.9 7.8 4.8 6.7

290 1.7 3.2 4.5 5.1 5.8 5 5.2 7.3

291 0.9 2.3 3.6 4.6 1.1 2.6 4.9 7.3

292 0.9 1.6 2.5 3.2 3.9 1.3 3.6 6

294 1.4 2.2 2.5 2.6 3.1 2.4 4 6.2

296 1.4 2.3 0.9 1.4 2.4 2.4 4.6 6.9

298 0.8 1.7 2.3 2.1 2.8 1.8 3.4 5.3

300 1.2 2.2 2.9 3.4 4.4 6.5 1.9 2.7

302 1.5 2.4 3 3.4 4 2.5 3.9 4.1

304 1.3 2.1 2.8 3.2 4.1 5.9 1.8 3.8

304.1 1.2 2.1 3 3.5 4.6 6.6 7.3 8.8

304.2 SR 652 Bridge at Wauchula

304.3 1.1 2.2 3 3.6 4.7 6.8 7.4 9.2

304.4 1.3 1.8 2.2 2.7 3.8 5.9 7.2 4.2

305 1.5 2.7 3 3.5 1.8 3.8 2.5 4.7

306 1.2 2.3 2.7 3.1 2.5 3.9 3.4 4.5

308 1.4 2.6 3 3.4 4.1 5.5 2.7 4.7

310 1.5 2.7 3.5 3.3 2.5 4.3 2.6 4.3

310.1 1.2 2.2 3.3 4.3 3.5 6.5 8.7 10.9

310.2 SR 64A Bridge at Wauchula

310.3 1.2 2.1 3.3 4.3 3.5 6.5 8.8 11

310.4 0.9 1.8 2.5 2.2 3.4 3.1 3 5.2

314 1.5 2.5 3.6 4.4 5.5 7.7 4.2 4.5

316 1.4 2.7 4.1 5.1 6.7 9.9 3.8 4.7

318 1.9 3.6 5 6.1 7.9 2.8 4 5.4

320 2.4 4 5.1 6.2 1.7 3.5 4.4 5.7

321 2.2 3.6 4.6 5.4 2.1 3.5 4.6 6

322 2.5 4.5 6 7.7 8.6 2.5 3.6 4.9

322.1 2.5 4.6 6.1 7.5 9 10.3 9.5 9.7

322.2 SR 664A Bridge near Wauchula

322.3 2.5 4.6 6.1 7.5 9 10.3 9.7 10.1

324 2.4 4.3 5.7 7.2 7 2.7 4 4.6

326 2.3 4.3 5.6 6.3 6.2 4.6 5.1 5.9

327 2.2 3.8 3.4 4.8 4.3 5.1 6.1 7.5

327.5 1.9 3.1 3.8 4.8 4.2 4.9 6.3 7.7

328 2.3 3.8 3.7 3.2 3.1 4.5 5.9 7.8

330 1.8 3.8 4.4 5.1 6 2.6 4.3 6.2

332 2 3.7 5.8 7 1.5 3 4.2 5.4

334 1.6 3.6 5.9 7.3 9 2.7 3.9 5.6

336 1.7 3.8 6.3 7.8 9.7 2.5 2.8 4.6

337 1.5 3 5.5 3.6 5.3 4.3 4.9 5.2

338 1.6 3.1 5.4 6.8 8.6 9.7 3.4 4.6

339 1.7 3.2 4.7 5.8 7.1 2.3 3.8 5.2

340 1.6 2.8 4.8 6.2 7.9 3.5 4 5.9

341 1.6 3.2 5.1 6.3 4.6 1.7 2.8 4.7

342 1.5 3.2 5.1 6.3 6.3 6.4 6.6 8.9

342.2 SR 664 Bridge at Bowling Green

343 1.5 3.2 5 6.2 6.2 6.4 6.6 8.9

343.5 1.3 2.9 4.3 5.2 3.8 1.3 2.7 4.5

344 1.5 2.5 4 4.5 3.8 3.1 2.2 4.1

346 1.3 2.6 4 3.6 2.8 3 2.5 4.2

348 1.3 2.4 3.6 3.9 3.7 3 3.8 5.4

350 1.3 2.4 3.6 3.3 3.1 3.1 3.4 4.5

352 1.3 2.3 3.2 4.2 3.2 2.3 3 4.5

354 1.5 2.6 3.4 4.4 6.2 2.4 2.7 4.7

354.1 1.6 2.9 3 3.2 4.1 6.1 6.5 8.9

354.2 SR 664 Bridge at Polk-Hardee Countyline

354.5 1.6 2.9 3 3.2 4.1 6.1 6.6 8.9

356 0.7 1.7 2.4 3.1 4.1 4.1 2.5 4.4

358 1.3 2 2.7 3.4 4.8 2.4 2.2 4.3

360 1.7 2.3 3.1 3.8 5 3.7 2.2 4.2

362 1.2 2.2 3 3.6 4.8 1.8 2.9 3.9

364 1.3 2.3 3 3.5 3.6 2.1 3.6 5.3

366 1.4 2.2 2.8 3.3 4.1 2.7 2.3 3.5

368 1.6 2.3 2.6 2.9 3.5 2.8 3.8 4.1

370 1.4 2.5 3.4 4 5 6.6 2.3 4.1

372 1.9 2.7 3.3 3.8 4.6 2.6 2.4 3.6

374 1.6 2.6 3.3 3.8 4.6 4 2.4 3.5

376 0.9 1.9 2.3 2.7 3.3 4.7 5.7 7.1

378 1.1 1.9 2.2 2.4 2.9 4.3 5.2 6.1

380 1.2 1 1.2 1.5 2.2 3.6 4.7 5.8

382 0.8 1.7 2.1 2.5 3.3 2.6 2.7 3.4

384 0.7 1.3 1.6 1.8 2.3 3.4 4.4 2.7

386 1 1.9 2.5 1.9 1.9 2.7 2.3 3

388 1.2 1.9 2.2 2.4 2.9 2 2.4 3.3

390 0.8 1.3 1.8 2.1 2.7 2.5 3.2 4.1

391 1 1.8 2.3 2.4 2.3 3 3.3 4.9

392 1.3 2 2.5 2.8 3.4 3.4 3.5 5.4

392.1 SR 657 Bridge near Fort Meade

392.5 1.3 2 2.5 2.9 3.5 2.2 3.8 5.8

393 1.4 2.6 3 3.3 4.2 5.7 1.5 2.5

396 1.6 2.6 1.8 1.4 1.4 2.7 4 5.4

398 1.7 2.1 1.4 1.5 1.7 3.1 4.3 5.4

400 2 2.2 2.4 2.7 2.7 2.8 3.7 4.6

402 1.7 3.3 4.2 3.9 1.2 2.6 3.8 5.1

404 1 1.8 1.9 2.2 2.6 2.6 3.4 4.3

405 1 2.5 3.5 4.1 2.8 2.1 1.7 3.1

406.2 1 1.5 2 1.8 2.7 4 4.9 5.1

406.3 0.8 1.8 2.5 2.9 1.8 3.6 4.8 6.2

406.4 Fort Meade Gaging Station at US 98 Bridge

Mean 1.5 2.6 3.5 4.0 4.2 4.1 4.2 5.5

Maximum 2.5 4.6 6.3 7.8 9.7 10.3 9.7 11

Minimum 0.7 1.0 0.9 1.4 1.1 1.3 1.5 2.5

Appendix J. Hydraulic depth at cross sections along 

reach 2 of the Peace River for selected percentile 

discharges (Continued)

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Feet
84 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

Appendix K. Acreage of areal inundation between adjacent 

cross sections along reach 2 of the Peace River 

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Acres

288 Zolfo Springs Gaging Station at US 17 Bridge

289 0.3 0.3 0.3 0.4 0.4 1.0 1.9 2.2

290 0.2 0.3 0.3 0.3 0.4 1.7 3.3 4.3

291 1.9 2.1 2.2 2.5 7.8 46.9 63.7 65.9

292 1.6 1.8 2.1 2.3 7.4 63.1 66.0 68.4

294 4.3 5.1 6.3 8.0 12.7 132.3 156.7 165.3

296 3.5 4.4 11.3 14.6 21.3 139.4 164.6 172.6

298 4.9 6.4 14.5 19.5 26.6 129.3 145.5 156.2

300 9.1 10.9 12.5 15.8 19.0 61.6 98.1 180.5

302 6.3 7.1 7.9 8.5 9.8 59.8 95.8 217.9

304 3.1 3.9 4.5 5.1 6.0 32.9 87.0 138.4

304.1 0.5 0.7 0.7 0.8 0.9 1.1 6.9 7.7

304.2 SR 652 Bridge at Wauchula

304.3 0.2 0.3 0.3 0.3 0.3 0.4 0.4 0.5

304.4 0.4 0.6 0.8 0.8 0.9 1.1 1.4 8.3

305 1.0 1.4 2.0 2.2 4.5 7.1 19.0 32.5

306 0.7 0.9 1.1 1.3 5.7 9.2 25.1 30.8

308 1.9 2.2 2.9 3.4 8.9 14.0 63.0 78.3

310 4.0 4.5 5.5 7.4 16.7 28.2 144.6 165.4

310.1 0.8 1.1 1.9 2.1 7.3 11.8 21.4 24.3

310.2 SR 64A Bridge at Wauchula

310.3 0.4 0.6 1.2 1.2 4.5 6.7 8.5 9.2

310.4 0.9 1.5 2.4 3.1 8.2 16.1 25.9 27.5

314 6.3 8.4 10.0 14.5 16.1 48.8 135.6 173.0

316 3.8 4.2 4.5 4.7 5.0 5.8 47.6 95.8

318 6.5 7.0 7.5 7.8 8.4 70.1 112.2 147.5

320 6.0 7.0 7.8 9.0 48.1 116.7 133.2 140.9

321 3.0 4.2 5.2 6.9 61.2 81.2 94.4 101.0

322 2.3 3.1 3.7 4.6 37.1 72.7 84.9 90.7

322.1 0.3 0.3 0.3 0.4 0.5 2.3 4.4 5.7

322.2 SR 664A Bridge near Wauchula

322.3 0.2 0.3 0.3 0.3 0.4 0.4 1.3 1.8

324 0.4 0.5 0.5 0.6 0.9 2.9 5.1 8.8

326 3.9 4.6 5.3 6.5 9.5 28.9 34.9 44.9

327 3.1 4.0 6.2 8.1 14.3 23.7 28.6 33.0

327.5 2.9 4.4 7.1 9.6 18.2 27.4 30.7 33.8

328 1.8 2.9 4.4 7.7 18.6 27.2 29.7 31.6

330 3.8 4.9 7.7 15.9 39.7 103.3 111.2 116.3

332 4.9 6.1 8.4 10.7 66.0 166.9 186.1 209.4

334 4.9 6.1 7.6 8.6 35.5 86.6 100.2 112.7

336 5.4 6.3 7.4 8.1 9.0 115.7 167.6 181.3

337 2.9 3.7 4.2 10.3 13.0 41.8 71.6 94.4

338 2.3 3.3 3.9 7.8 9.6 16.7 39.8 64.8

339 1.7 2.2 2.9 3.3 3.9 21.3 38.1 47.0

340 2.2 3.3 4.3 5.0 6.0 56.6 81.4 92.3

341 1.8 2.8 3.3 3.8 6.4 54.3 86.2 94.3

342 0.3 0.4 0.4 0.5 0.8 4.1 7.7 9.3

342.2 SR 664 Bridge at Bowling Green

343 0.2 0.2 0.2 0.3 0.4 1.2 1.8 2.3

343.5 0.4 0.5 0.6 0.7 1.4 10.5 16.3 19.9

344 0.7 1.0 1.3 1.7 4.2 22.4 52.8 60.0

346 1.1 1.5 1.9 2.8 7.1 17.4 55.7 65.2

348 0.9 1.2 1.6 2.4 6.2 20.1 39.5 46.6

350 4.9 6.7 8.8 12.5 24.4 72.5 113.7 141.9

352 3.4 4.5 5.8 8.3 20.6 61.4 111.4 146.9

354 2.7 3.4 4.3 4.9 8.3 34.3 76.0 89.6

354.1 0.3 0.4 0.5 0.6 0.9 2.4 9.5 10.0

354.2 SR 664 Bridge at Polk-Hardee Countyline

354.5 0.1 0.1 0.2 0.2 0.3 0.4 1.5 1.7

356 0.4 0.5 0.8 1.1 1.6 2.7 16.4 18.2

358 1.8 2.5 3.4 4.2 5.7 14.0 51.8 57.9

360 4.7 6.8 8.0 8.9 10.6 30.0 118.0 128.0

362 3.6 5.3 5.9 6.5 7.6 35.1 90.3 111.2

364 3.8 4.9 5.6 6.2 8.1 68.5 92.0 115.0

366 3.0 4.0 4.8 5.4 7.4 50.7 78.0 96.6

368 3.6 5.4 7.1 8.4 10.7 31.7 51.2 73.1

370 2.7 3.9 4.7 5.4 6.4 19.9 38.0 52.8

372 5.2 7.3 8.4 9.2 10.5 23.0 76.8 97.5

374 4.3 6.1 7.4 8.3 9.9 23.5 106.0 149.5

376 5.3 8.1 10.7 12.6 15.8 26.2 85.4 114.3

378 5.8 9.0 11.6 14.2 18.7 27.4 33.5 40.6

380 6.9 13.3 21.1 28.6 42.0 68.8 87.7 110.3

382 2.2 4.7 7.9 10.7 15.9 30.3 45.0 63.8

384 1.8 2.3 2.8 3.2 3.9 8.6 15.3 33.7

386 2.1 2.6 3.1 3.9 5.4 8.8 15.3 29.1

388 2.1 2.6 3.4 4.4 6.3 15.1 34.6 57.9

390 3.8 5.5 7.4 8.8 11.0 26.4 41.7 59.5

391 4.2 5.4 6.5 8.7 16.6 33.6 51.1 60.4

392 0.4 0.6 0.7 1.1 2.4 4.6 12.7 14.8

392.1 SR 657 Bridge near Fort Meade

392.5 0.2 0.2 0.3 0.3 0.4 2.1 6.4 7.5

393 0.3 0.4 0.5 0.5 0.6 3.8 9.2 11.8

396 2.9 3.5 6.1 10.0 20.7 28.8 47.6 61.5

398 4.4 7.3 19.5 32.5 66.9 85.8 91.8 98.0

400 3.7 7.5 15.7 21.4 35.3 48.0 53.4 60.5

402 3.5 6.7 9.9 12.1 34.8 60.4 68.3 77.6

404 3.6 7.0 10.5 13.4 31.6 59.1 67.0 77.7

405 2.2 4.1 5.9 7.0 9.4 19.0 29.9 34.4

406.2 3.8 6.5 8.9 13.8 18.2 28.4 49.5 57.7

406.3 0.7 1.3 1.9 3.0 5.8 6.9 7.7 9.3

406.4 Fort Meade Gaging Station at US 98 Bridge

Total 225 312 431 565 1,118 3,082 4,892 6,065

Appendix K. Acreage of areal inundation between adjacent 

cross sections along reach 2 of the Peace River (Continued)

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Acres
Appendices 85

Appendix L. Decrease of inundated acreage resulting from a 

potential 10-percent discharge withdrawal at cross sections 

along reach 2 of the Peace River 

[Blanks indicate no decrease in inundated acreage]

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Acres

286

287 0.1 2.4 0.4 0.3

288 Zolfo Springs Gaging Station at US 17 Bridge

289 0.1 0.1 0.4 0.1

290 0.1 0.2 0.3 0.1

291 0.1 0.1 4.3 0.3 0.5 0.5

292 0.1 0.1 4 4.3 0.5 0.4

294 0.1 0.4 0.5 1.1 15 2.3 1.5

296 0.1 0.1 6.2 1.1 1.5 8.7 2 1.4

298 0.2 0.2 7.2 1.1 1.6 9.8 2.7 2.5

300 0.2 0.3 0.6 0.8 11.5 22.1 6.1

302 0.2 0.2 0.2 0.2 3.7 15.9 7.3

304 0.1 0.1 0.1 0.2 2 2.5 4.6

304.1 0.1 0.4 0.2

304.2 SR 652 Bridge at Wauchula

304.3 0.1 0.1

304.4 0.1 0.1 0.1 0.3

305 0.1 0.1 0.1 1.5 3.4 0.5

306 0.1 0.1 0.2 2.5 5.5 1.1

308 0.1 0.1 0.1 0.1 3.8 6.6 2.8

310 0.1 0.3 0.8 0.3 9.1 14.8 1.6

310.1 0.1 0.1 1.5 1.8 2.2 0.2

310.2 SR 64A Bridge at Wauchula

310.3 0.7 0.1 0.1 1.2 0.2 0.1

310.4 0.2 1.8 1.2 0.6 0.3

314 0.2 0.3 0.2 0.3 0.3 5.9 36.1 1.8

316 0.1 0.1 0.1 0.1 20.9 2

318 0.1 0.1 0.1 0.1 0.1 29.3 1 2.9

320 0.2 0.2 0.1 0.3 37.9 30.1 0.8 0.8

321 0.1 0.1 0.2 0.5 23.4 1.8 1.1 0.7

322 0.1 0.2 0.3 1.2 2.4 1.4 1.2

322.1 0.1 0.1 0.1 0.1 0.2

322.2 SR 664A Bridge near Wauchula

322.3 0.1 0.1

324 0 0.1 0.1 0.3 1 0.2

326 0.1 0.1 0.1 0.3 1.2 2.9 1 1.7

327 0.1 0.1 0.4 0.3 1.2 1.2 1 1.1

327.5 0.1 0.3 0.4 0.6 2.7 1 0.6 0.7

328 0.1 0.1 0.6 0.8 3.2 0.6 0.5 0.5

330 0.2 1.3 2.2 5.2 3 1.5 1.2

332 0.1 0.1 0.4 0.6 46.1 5.1 4.4 4.9

334 0.1 0.2 0.1 0.2 22.5 1.7 2.2 3.2

336 0.2 0.2 0.1 35.8 2.7 3.2

337 0.1 0.1 0.1 5.9 0.2 21.1 2.9 1.3

338 0.1 0.1 0.1 3.6 0.1 2.1 4 2.2

339 0.1 0.2 0.1 8.4 2.7 3.1

340 0.1 0.1 0.1 0.2 0.2 12.8 2 4

341 0.1 0.2 0.1 0.6 0.7 1.5 1.7

342 0.1 0.1 0.3 0.1 0.4

342.2 SR 664 Bridge at Bowling Green

343 0.1 0.1 0.1

343.5 0.1 0.1 4.3 0.4 0.7

344 0.1 0.1 0.2 0.4 13.5 1.9 0.8

346 0.6 0.7 2.7 4.6 3.2

348 0.1 0.6 0.6 1.9 3.3 2

350 0.1 0.3 0.3 2.3 1.9 6.6 7.7 1.9

352 0.1 0.1 0.3 1.6 2.2 9.7 10.8 1.9

354 0.1 0.1 0.2 0.1 0.6 7.6 4.8 2.4

354.1 0.1 0.1 0.1 0.5 0.8 0.1

354.2 SR 664 Bridge at Polk-Hardee Countyline

354.5 0.1 0.1

356 0.1 0.1 0.1 0.3 1.3 0.4

358 0.1 0.2 0.2 0.3 2.9 3 1.1

360 0.1 0.2 0.3 0.3 0.3 4.7 8.1 1.5

362 0.1 0.1 0.2 14.5 7.8 5.1

364 0.1 0.1 0.2 0.3 0.9 18.8 5.4 5.9

366 0.1 0.1 0.1 0.1 0.9 4.5 3.7 4.3

368 0.1 0.3 0.4 0.4 0.5 2.3 2.7 3.8

370 0.1 0.1 0.2 0.2 0.3 0.8 2 2.4

372 0.2 0.3 0.2 0.3 0.3 1.1 6.5 4.4

374 0.1 0.2 0.2 0.3 0.3 2 6.5 4.2

376 0.2 0.3 0.5 0.5 0.7 2 3.2 1.7

378 0.1 0.3 0.6 0.8 1 1.3 1.3 1.8

380 0.2 1 1.9 2.4 2.9 3.6 4.1 5.6

382 0.5 0.7 0.8 1.2 2.1 3.5 4.5

384 0.1 0.1 0.1 0.2 0.8 1.8 4.4

386 0.1 0.2 0.3 0.3 0.5 1.6 3.2

388 0.1 0.2 0.1 0.3 0.4 2 4.6 5.1

390 0.2 0.3 0.4 0.5 2.9 3.5 4

391 0.1 0.1 0.2 0.3 1.6 1.6 3 1.9

392 0.1 0.1 0.3 0.7 0.1

392.1 SR 657 Bridge near Fort Meade

392.5 1.4 0.4 0.1

393 0.1 0.1 0.1 0.1 2.9 1.1 0.3

396 0.1 1 1.1 0.5 0.7 4.9 2

398 0.1 0.5 3.7 3.6 1.9 1.8 1 2.3

400 0.2 0.6 1.5 1.5 2.4 1 1.3 2.5

402 0.1 0.5 0.6 1 2.6 1.5 1.9 2.3

404 0.2 0.4 0.6 1 0.9 1.4 2.2 2.1

405 0.2 0.4 0.3 0.8 0.6 1.2 0.8

406.2 0.1 0.3 0.4 1.4 1.6 1.1 1.4 3

406.3 0.2 0.2 0.2 0.2 0.1 0.6

Total 5.6 11.7 36.5 45.8 196 373 297 165

Appendix L. Decrease of inundated acreage resulting from a 

potential 10-percent discharge withdrawal at cross sections 

along reach 2 of the Peace River (Continued)

[Blanks indicate no decrease in inundated acreage]

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Acres
86 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

Appendix M. Extent of inundation at cross sections 

along reach 3 of the Peace River for selected percentile

discharges 

Cross

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Feet

406.5 71 112 148 208 730 847 946 1,072

406.6 71 156 232 307 577 1,061 1,542 2,170

407 63 84 103 163 286 896 1,272 1,639

408 82 179 338 644 922 1,142 1,286 1,432

410 78 154 612 982 1,210 1,520 1,819 1,945

412 65 159 317 670 847 1,610 1,807 2,029

414 57 303 950 1,378 1,657 1,938 2,322 2,519

416 100 443 1,000 1,320 1,512 1,674 1,792 2,626

417 68 133 329 396 485 647 718 1,660

418 77 157 327 384 472 662 745 1,708

418.5 Phosphate Mine Bridge

419 79 165 337 390 482 672 750 836

420 50 67 83 94 121 310 435 577

422 40 139 376 1,098 1,436 1,888 1,984 2,075

424 46 136 759 934 1,209 1,658 1,823 1,869

426 57 387 1,134 1,213 1,346 1,501 1,582 1,670

428 71 359 633 857 1,267 1,851 2,285 2,368

430 64 993 1,284 1,509 1,633 1,916 2,281 2,508

432 74 502 987 1,106 1,388 2,357 2,727 3,133

434 65 919 1,304 1,520 1,667 1,823 2,006 2,639

436 97 315 386 429 502 642 746 966

438 68 584 726 835 988 1,218 1,608 1,895

440 69 115 129 710 824 852 1,038 1,085

442 44 123 603 1,173 1,192 1,228 1,259 1,294

443 48 97 1,158 1,412 1,905 2,125 2,352 2,781

444 47 98 1,178 1,431 1,912 2,129 2,357 2,790

444.5 SR 640 Bridge at Homeland

445 48 159 1,209 1,456 1,928 2,147 2,460 2,919

446 68 660 1,880 2,049 2,181 2,357 2,456 2,540

448 46 736 1,154 1,432 1,603 1,919 2,177 2,342

450 68 557 1,268 1,364 1,516 1,799 2,026 2,543

452 91 788 948 976 1,092 1,392 1,881 2,133

454 56 787 957 1,021 1,135 1,437 1,535 1,626

456 1,807 2,374 2,482 2,591 2,929 3,061 3,122 3,168

458 81 125 144 158 182 228 264 1,713

460 159 678 1,003 1,060 1,288 1,817 1,890 1,983

462 57 7,79 1,117 1,253 1,454 1,691 1,711 1,737

464 80 709 1,089 1,170 1,323 1,447 1,468 1,495

466 38 540 881 988 1,171 1,194 1,213 1,236

467 70 206 466 644 821 1,972 2,004 2,346

468 124 233 470 608 739 961 1,072 1,502

468.5 Clear Springs Mine Bridge

469 124 236 471 615 748 967 1,158 1,521

470 129 217 397 563 665 1,363 1,651 1,939

472 71 105 127 1,193 1,290 1,415 1,470 1,537

474 89 1,671 1,869 1,896 1,922 1,969 2,004 2,042

476 56 733 1,251 1,258 1,270 1,290 1,306 1,325

478 91 522 1,016 1,110 1,182 1,249 1,300 1,340

480 86 246 717 1,048 1,112 1,183 1,225 1,253

481 144 291 768 1,054 1,119 1,195 1,235 1,277

482 Abandoned Mine Bridge

483 144 295 785 1,056 1,121 1,196 1,238 1,278

484 45 331 1,632 1,654 1,697 1,747 1,786 1,825

486 46 90 109 118 135 168 354 642

488 72 852 1,026 1,126 2,237 3,530 4,001 4,067

490 24 527 1,382 1,451 1,539 1,688 2,177 2,204

492 90 922 2,812 2,886 2,987 3,041 3,110 4,552

494 83 268 397 406 423 456 483 3,213

498 61 93 211 430 792 1,002 1,335 1,358

500 36 132 373 589 818 1,025 1,293 1,450

501 Bartow Gaging Station at SR 60

Mean 104 424 819 1,007 1,096 1,466 1,641 1,953

Maximum 1,807 2,374 2,812 2,886 2,987 3,530 4,001 4,552

Minimum 24 67 83 94 121 168 264 577

Appendix N. Hydraulic depth at cross sections along reach 3 

of the Peace River for selected percentile discharges

Cross

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Feet

406.5 0.9 1.9 2.7 3.2 1.8 3.4 4.5 4.9

406.6 0.9 1.5 2.2 2.5 2.4 2.7 2.9 3.6

407 1.3 2.3 3.1 2.7 2.7 2.4 2.7 3.5

408 1.6 2.1 2.0 1.8 2.4 3.5 4.4 5.3

410 1.1 2.0 1.2 1.4 2.3 3.4 4.1 5.3

412 1.4 1.6 1.7 1.4 2.0 2.3 3.3 4.3

414 1.4 1.0 0.9 1.2 1.8 3.1 3.6 4.7

416 1.3 1.0 1.1 1.3 1.9 3.2 4.1 4.0

417 1.2 1.8 1.4 1.6 2.1 2.9 3.7 2.4

418 1.4 1.9 1.6 1.9 2.3 2.9 4.0 5.4

418.5 Phosphate Mine Bridge

419 1.4 1.9 1.6 1.9 2.3 2.9 4.1 5.5

420 1.7 2.7 3.1 3.2 3.3 2.3 2.6 3.2

422 1.8 1.6 1.3 1.0 1.5 2.5 3.5 4.7

424 1.9 1.8 1.0 1.2 1.6 2.4 3.2 4.5

426 1.7 0.9 0.9 1.3 1.9 3.0 3.9 4.9

428 2.1 1.7 1.7 1.6 1.8 2.3 2.9 4.0

430 0.8 0.8 1.5 1.7 2.4 3.3 3.8 4.7

432 1.5 0.6 0.9 1.3 1.8 2.1 2.9 3.7

434 1.3 0.7 1.1 1.4 2.0 3.2 3.9 4.0

436 1.5 1.5 1.9 2.1 2.5 3.2 3.8 4.1

438 2.3 0.9 1.4 1.7 2.3 3.3 3.6 4.3

440 1.8 2.7 3.3 0.9 1.6 3.0 3.6 4.8

442 1.7 1.8 0.8 1.0 1.7 3.0 4.1 5.3

443 1.9 2.5 0.8 1.1 1.5 2.6 3.4 4.1

444 1.6 2.4 1.9 1.8 2.0 3.3 4.4 5.8

444.5 SR 640 Bridge at Homeland

445 1.7 1.6 1.9 1.8 2.1 3.5 4.7 6.1

446 1.9 0.9 1.1 1.5 2.2 3.4 4.5 5.7

448 1.5 0.9 1.5 1.7 2.2 3.2 4.0 5.1

450 1.5 0.9 1.2 1.6 2.2 3.2 4.0 4.5

452 1.1 1.0 1.6 2.0 2.6 3.4 3.5 4.4

454 1.3 0.6 1.1 1.5 2.1 3.1 4.0 5.1

456 0.2 1.0 1.5 1.9 2.5 3.8 5.0 6.3

458 1.3 1.5 1.9 2.2 2.6 3.4 4.1 1.4

460 0.8 0.9 1.2 1.6 2.1 2.7 3.6 4.8

462 1.6 0.8 1.1 1.4 2.0 3.1 4.1 5.4

464 1.3 0.6 1.0 1.3 1.9 3.1 4.1 5.3

466 2.0 0.6 0.9 1.1 1.6 2.8 3.8 5.0

467 2.1 1.8 1.5 1.5 1.8 1.9 2.8 3.6

468 2.4 3.2 4.0 4.3 4.8 5.3 5.3 3.2

468.5 Clear Springs Mine Bridge

469 2.5 3.3 4.0 4.3 4.8 5.4 5.0 3.6

470 2.4 3.0 2.3 2.0 2.4 2.3 2.8 3.7

472 2.5 3.3 3.5 0.7 1.5 2.7 3.7 4.9

474 2.1 0.6 1.3 1.9 2.7 4.0 5.0 6.3

476 1.7 1.0 1.3 1.8 2.6 4.0 5.1 6.4

478 2.2 1.0 1.2 1.6 2.3 3.6 4.6 5.8

480 1.6 1.7 1.1 1.2 2.0 3.3 4.3 5.6

481 1.7 2.7 3.1 3.7 4.5 6.0 7.2 5.9

482 Abandoned Mine Bridge

483 1.8 2.7 3.2 3.7 4.6 6.1 7.2 5.8

484 1.6 0.9 0.8 1.3 2.1 3.6 4.6 5.9

486 1.3 2.2 2.6 2.8 3.2 3.9 2.5 2.4

488 1.4 0.9 1.6 1.9 1.6 2.3 3.1 4.5

490 1.7 0.4 0.6 1.0 1.7 3.0 3.4 4.7

492 0.9 0.4 0.5 0.9 1.7 3.1 4.2 4.0

494 0.4 0.9 1.2 1.6 2.3 3.5 4.4 1.8

498 1.0 1.4 1.1 0.9 1.1 2.0 2.4 3.7

500 0.8 0.9 0.8 0.9 1.4 2.5 3.0 4.2

501 Bartow Gaging Station at SR 60

Mean 1.5 1.5 1.7 1.8 2.3 3.2 4.0 4.6

Maximum 2.5 3.3 4.0 4.3 4.8 6.1 7.2 6.4

Minimum 0.2 0.4 0.5 0.7 1.1 1.9 2.4 1.4
Appendices 87

Appendix O. Acreage of areal inundation between adjacent 

cross sections along reach 3 of the Peace River

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Acres

406.4 Fort Meade Gaging Station at US 98 Bridge

406.5 0.2 0.2 0.3 0.4 1.3 1.4 1.5 1.8

406.6 0.7 1.4 1.99 2.6 5.6 8.0 10.3 13.0

407 0.8 1.9 2.83 4.1 7.4 14.9 20.7 27.3

408 3.1 5.2 8.16 13.9 20.1 33.1 41.3 49.2

410 4.4 8.4 22.3 37.5 49.0 61.1 71.2 77.4

412 3.1 6.2 17.23 30.3 37.4 56.5 65.1 70.9

414 3.1 10.2 26.12 41.5 50.6 71.3 83.4 92.1

416 4.0 16.3 42.55 58.7 68.0 75.9 82.8 103.7

417 3.3 9.9 20.34 25.8 30.3 36.3 39.7 63.0

418 0.1 0.2 0.38 0.4 0.6 0.8 0.8 1.9

418.5 Phosphate Mine Bridge

419 0.2 0.4 0.75 0.9 1.1 1.4 1.5 1.1

420 0.4 0.7 1.2 1.4 1.7 2.8 3.4 4.1

422 1.3 2.8 5.81 14.3 18.5 25.9 28.5 31.1

424 1.7 5.1 20.27 34.2 45.0 61.0 65.1 67.5

426 2.4 10.2 35.02 39.7 47.2 58.4 63.0 65.5

428 2.2 11.5 25.42 29.4 36.6 47.7 56.1 58.9

430 2.6 24.6 34.79 42.8 52.3 68.0 82.5 88.0

432 2.9 30.1 45.07 52.0 59.9 84.9 99.7 112.0

434 2.2 15.7 24.96 28.8 33.3 45.7 51.6 61.4

436 2.4 16.0 21.81 25.1 27.9 31.6 35.2 46.0

438 3.0 15.7 19.55 22.2 26.1 32.5 40.8 49.8

440 2.5 10.9 13.32 25.6 29.9 33.8 42.0 46.9

442 2.2 4.6 14.29 36.4 38.9 40.2 44.5 46.1

443 1.5 3.5 28.31 41.5 49.6 53.8 57.9 65.3

444 0.1 0.2 2.69 3.3 4.4 4.9 5.4 6.4

444.5 SR 640 Bridge at Homeland

445 0.1 0.3 2.74 3.3 4.4 4.9 5.5 6.5

446 0.3 1.3 6.84 8.1 9.8 10.7 11.8 13.3

448 2.1 25.4 51.82 58.3 63.1 70.9 76.6 80.3

450 2.8 21.3 44.31 53.0 60.0 72.9 83.4 99.8

452 3.6 30.6 45.91 48.2 53.0 63.3 75.7 88.7

454 3.3 33.7 40.89 42.9 47.9 61.0 73.7 81.2

456 37.0 61.1 66.21 69.4 77.7 85.8 88.7 91.3

458 26.5 36.2 38.13 40.0 45.8 48.4 49.8 72.3

460 4.6 14.7 20.55 21.8 26.1 36.5 38.5 65.4

462 3.8 24.4 34.38 37.4 43.9 56.2 57.7 59.6

464 2.2 19.7 29.21 32.1 36.7 41.5 42.1 42.8

466 2.2 18.7 28.92 31.6 36.3 38.4 38.9 39.6

467 2.1 13.2 22.79 27.7 33.8 55.3 56.2 61.7

468 0.3 0.7 1.4 1.9 2.3 4.4 4.6 5.7

468.5 Clear Springs Mine Bridge

469 0.3 0.4 0.58 0.7 0.8 1.0 1.3 2.3

470 0.2 0.4 0.7 0.9 1.1 1.9 2.3 2.8

472 1.8 3.0 4.75 15.6 17.3 25.1 28.2 31.4

474 3.5 34.2 38.41 55.5 57.6 60.6 62.2 64.2

476 3.3 48.7 62.9 63.6 64.3 65.7 66.7 67.8

478 3.9 26.7 45.14 47.3 49.0 50.8 52.1 53.3

480 4.7 16.5 34.45 42.1 44.7 47.3 49.2 50.6

481 0.4 0.9 2.56 3.6 3.8 4.1 4.2 4.4

482 Abandoned Mine Bridge

483 0.3 0.5 0.99 1.3 1.3 1.4 1.4 2.2

484 0.2 0.7 2.77 3.1 3.2 3.4 3.5 3.6

486 1.5 7.0 24.35 24.8 25.7 26.9 30.5 34.9

488 2.2 16.4 19.72 21.6 41.0 63.9 75.2 81.3

490 2.8 31.6 55.82 59.6 84.6 114.9 134.9 137.0

492 1.6 18.9 52.56 54.3 56.7 59.2 66.5 85.3

494 3.3 20.8 43.24 44.1 45.5 46.7 48.0 102.0

498 1.2 2.5 3.46 4.8 7.0 8.8 11.5 30.2

500 0.3 0.6 1.68 2.8 4.3 5.2 6.5 7.0

501 Bartow Gaging Station at SR 60

Total 173 744 1,266 1,537 1,798 2,196 2,449 2,828

Appendix P. Decrease of inundated acreage resulting from a 

potential 10-percent discharge withdrawal at cross sections 

along reach 3 of the Peace River

[Blanks indicate no decrease in inundated acreage]

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Acres

406.4 Fort Meade Gaging Station at US 98 Bridge

406.5 0.1 0.2 0.2

406.6 0.1 0.1 0.3 0.6 0.3 0.9 0.3

407 0.2 0.2 0.6 0.7 0.7 2.3 0.7

408 0.1 0.2 1.5 1.6 0.7 0.8 2.9 1.6

410 0.2 0.4 4.5 3.8 1.4 1.9 2.4 1.5

412 0.1 0.5 2.4 2.1 1.6 1.6 2.1 1.4

414 0.1 1.3 3.1 1.3 2.1 1.2 5.6 2.2

416 0.1 2.7 4.8 2.7 1.3 0.6 3.2 2.3

417 0.1 1.3 1.7 1.4 0.8 0.8 0.9 12.8

418 0.1 0.1 0.5

418.5 Phosphate Mine Bridge

419 0.1 0.1 0.1 0.1 0.1

420 0.1 0.1 0.1 0.1 0.2 0.1 0.2

422 0.1 0.5 0.5 1.1 0.8 0.6 0.4

424 0.4 1.6 1.5 2.7 1.5 0.5 0.4

426 0.1 2.6 1.4 1.3 1.6 1.2 0.6 0.5

428 0.1 1.8 1.1 1.1 1.5 2.2 0.6 0.6

430 0.6 1.7 1.6 1.6 1.9 3.2 2.3 0.6

432 0.7 3.0 2.1 1.1 1.1 5.8 2.9 2.0

434 0.1 1.2 1.5 1.1 0.5 3.0 1.3 4.4

436 0.2 0.8 0.9 1.0 0.4 0.6 1.6 5.8

438 0.2 0.6 0.7 0.8 0.8 1.4 2.0 2.1

440 0.4 0.5 11.0 0.7 1.0 1.5 0.8

442 0.2 3.9 12.7 0.4 0.2 0.3 0.4

443 0.2 9.8 2.5 0.4 0.4 1.0 2.0

444 0.6 0.2 0.1 0.1 0.1 0.3

444.5 SR 640 Bridge at Homeland

445 0.1 0.2 0.1 0.2 0.2

446 0.3 0.4 0.4 0.1 0.1 0.3 0.5

448 3.8 1.2 3.8 0.9 1.3 1.4 0.6

450 0.1 2.5 1.1 6.1 1.4 2.1 2.7 1.1

452 0.1 2.0 0.9 0.7 1.3 1.5 3.1 1.6

454 0.2 1.8 0.8 0.6 1.5 1.4 3.0 2.0

456 0.9 1.5 0.7 1.4 1.7 0.8 0.5 0.7

458 0.6 0.3 0.3 0.9 1.3 0.4 0.3 9.1

460 0.7 0.8 0.3 0.4 0.9 0.4 0.5 12.4

462 0.6 1.3 1.0 0.8 1.4 0.3 0.4 0.6

464 0.1 1.7 1.0 0.8 1.0 0.1 0.1 0.2

466 0.1 1.9 1.0 0.8 0.9 0.1 0.1 0.2

467 0.1 1.1 0.9 1.0 1.1 0.2 0.2 5.0

468 0.1 0.1 0.1 0.1 0.1 0.5

468.5 Clear Springs Mine Bridge

469 0.2 0.1

470 0.1 0.2 0.1

472 0.1 0.3 0.3 0.3 0.4 0.8 0.5

474 18.2 0.6 0.3 0.4 0.4 0.4 0.5

476 0.1 19.3 1.6 0.2 0.1 0.3 0.3 0.2

478 0.1 3.5 1.2 0.6 0.2 0.3 0.3 0.2

480 0.1 2.5 2.2 1.5 0.4 0.4 0.5 0.2

481 0.1 0.3 0.1 0.1

482 Abandoned Mine Bridge

483 0.1 0.1

484 0.1 0.1 0.0 0.1

486 1.0 0.1 0.2 0.2 0.2 2.9 2.0

488 1.2 0.1 1.5 3.9 3.6 3.2 2.8

490 0.1 3.6 3.5 2.1 5.1 4.6 0.4 0.6

492 0.1 3.1 6.7 0.4 0.4 0.3 0.3 4.0

494 0.2 3.0 4.1 0.2 0.1 0.2 0.4 7.2

498 0.1 0.1 0.1 0.3 0.4 0.1 1.9

500 0.2 0.3 0.3 0.1 0.1 0.1

501 Bartow Gaging Station at SR 60

Total 6.5 94.9 75.6 76.7 48.1 49.0 58.6 99.3
88 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

Appendix Q. Extent of inundation at cross sections along the 

Alafia, North Prong Alafia, and South Prong Alafia Rivers for 

selected percentile discharges

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Feet

Alafia River

73 29 40 42 42 44 48 950 1326

74 SR 640 Bridge and Alafia River near Lithia Gaging Station

75 36 37 38 39 40 44 759 2,494

76 16 25 31 34 55 983 1,657 2,010

77 66 78 86 92 386 2,322 2,679 3,313

78 43 45 46 47 49 319 1,983 2,806

79 68 75 80 84 90 156 1,512 2,671

80 57 71 83 93 107 447 1,411 2,364

81 42 43 44 45 46 50 864 1,401

82 70 73 76 78 82 348 1,311 1,914

83 Railroad Bridge

84 54 58 61 64 73 422 1,241 1,728

85 41 43 44 45 47 141 896 1,016

86 62 63 64 65 67 356 927 1,173

87 42 44 45 46 48 1,191 1,866 1,958

88 42 44 45 46 48 1,695 1,924 2,025

89 60 76 87 96 110 1,799 2,628 2,907

90 33 36 38 39 236 1,967 2,599 2,680

91 36 52 62 69 235 1,846 2,016 2,199

92 40 43 49 57 72 1,890 2,340 2,620

93 179 198 210 219 238 1,644 1,801 1,988

94 SR 39 Bridge

95 190 199 206 211 217 1,306 1,624 1,899

96 72 104 239 338 478 813 948 1,202

Mean 61 69 80 88 132 942 1,616 2,081

Maximum 190 199 239 338 478 2,322 2,679 3,313

Minimum 16 25 31 34 40 44 759 1,016

North Prong Alafia River

1 35 37 39 40 98 1,004 1,519 1,600

2 35 38 39 45 311 931 1,187 1,278

3 35 38 49 123 243 1,291 1,398 1,471

4 38 44 48 94 262 683 1,319 1,421

5 30 31 32 42 77 113 126 146

6 Railroad Bridge

7 30 31 33 50 84 114 128 193

7.5 31 32 33 33 34 57 126 216

8 34 36 38 39 49 442 1,215 1,362

9 33 35 36 37 39 348 946 1,234

10 32 35 36 38 40 596 1,250 1,386

11 Railroad Bridge

12 32 35 36 38 40 690 1,268 1,391

13 37 39 41 42 44 900 1,381 1,553

14 272 278 282 286 293 783 1,157 1,865

15 SR 676 Bridge and Gaging Station

16 276 280 284 287 293 783 1,165 1,869

16.5 278 280 282 284 288 712 1,417 1,908

17 43 49 53 56 65 400 985 1,439

18 54 69 78 83 103 270 868 1,240

19 36 39 181 240 378 719 887 1,026

20 35 38 40 584 1,093 1,247 1,360 1,470

21 35 39 115 180 379 827 1,068 1,179

22 36 40 151 531 982 1,062 1,117 1,176

23 35 40 264 369 491 641 699 781

Mean 68 72 100 160 258 664 1,027 1,237

Maximum 278 280 284 584 1,093 1,291 1,519 1,908

Minimum 30 31 32 33 34 57 126 146

Appendix Q. Extent of inundation at cross sections along the 

Alafia, North Prong Alafia, and South Prong Alafia Rivers for 

selected percentile discharges (Continued)

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Feet

South Prong Alafia River

1 35 39 57 98 180 1,268 1,279 1,291

2 28 30 56 94 275 1,146 1,314 1,425

3 29 72 116 153 348 1,189 1,220 1,268

4 39 65 85 109 460 1,139 1,263 1,298

5 37 204 348 414 609 744 1,008 1,211

6 40 49 64 73 82 105 597 1,095

6.5 78 82 84 169 190 334 845 1,035

7 34 108 132 140 151 181 488 839

8 SR 640

9 34 108 132 140 151 182 490 847

9.5 185 210 221 233 302 538 662 759

10 28 34 43 48 55 510 693 914

11 39 47 66 95 150 482 821 1,106

12 24 29 128 190 368 919 1,238 1,337

13 21 33 53 75 122 792 896 1,009

14 29 65 193 310 611 953 1,098 1,222

15 37 51 64 75 93 385 706 971

16 33 38 46 60 164 889 1,017 1,126

17 24 28 82 211 348 646 786 941

18 19 30 81 101 124 850 1,039 1,127

19 25 29 130 173 230 1,020 1,166 1,263

20 17 20 22 23 25 1,313 1,627 1,668

21 33 36 38 39 190 1,392 1,420 1,455

21.5 28 32 35 37 145 871 902 947

22 25 28 30 32 34 567 832 1,087

23 Jameson Road and Gaging Station

24 25 28 30 31 33 585 853 1,093

24.5 25 31 35 39 111 1,074 1,138 1,221

25 22 24 26 27 29 458 686 973

26 27 30 33 35 38 804 870 944

27 23 26 27 29 335 846 1,042 1,196

28 43 58 68 76 88 942 1,425 1,638

29 30 35 40 43 48 539 705 884

Mean 36 55 83 109 197 763 972 1,135

Maximum 185 210 348 414 611 1,392 1,627 1,668

Minimum 17 20 22 23 25 105 488 759
Appendices 89

Appendix R. Hydraulic depth at cross sections along the 

Alafia, North Prong Alafia, and South Prong Alafia Rivers for 

selected percentile discharges

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Feet

Alafia River

73 0.6 1.2 2.1 2.9 4.1 7.5 2.4 4.4

74 SR 640 Bridge and Alafia River near Lithia Gaging Station

75 2.0 2.7 3.4 4.0 5.1 8.3 2.6 4.3

76 1.6 2.5 3.1 3.4 3.2 1.5 2.4 3.7

77 3.1 4.4 5.1 5.7 1.8 2.0 3.3 4.2

78 2.5 4.4 5.5 6.4 7.6 1.9 1.1 2.1

79 1.8 3.4 4.4 5.2 6.3 5.8 1.6 1.8

80 1.5 2.5 3.3 3.9 4.7 2.3 1.9 2.2

81 2.0 3.3 4.2 5.0 6.2 9.2 1.7 2.3

82 3.3 4.5 5.4 6.1 7.2 3.1 2.2 3.6

83 Railroad Bridge

84 3.4 4.5 5.4 6.1 6.6 2.8 2.3 3.7

85 0.9 2.5 3.6 4.5 5.9 3.8 1.3 2.6

86 1.7 2.9 3.9 4.7 6.0 2.5 2.7 3.5

87 1.6 2.9 3.8 4.5 5.7 0.9 1.9 3.2

88 1.9 3.3 4.3 5.0 6.2 1.3 2.2 3.2

89 1.6 2.6 3.2 3.7 4.5 1.1 1.6 2.5

90 2.0 3.3 4.1 4.7 1.2 1.4 2.1 3.0

91 1.7 2.5 3.1 3.5 1.8 0.9 1.7 2.6

92 2.4 3.9 4.5 4.7 4.8 0.9 1.5 2.2

93 1.3 2.8 3.8 4.5 5.3 6.2 6.1 6.9

94 SR 39 Bridge

95 0.9 2.6 3.6 4.4 5.4 6.0 6.3 7.3

96 1.0 1.8 1.6 1.8 2.3 3.5 4.0 4.1

Mean 1.8 3.1 3.9 4.5 4.8 3.5 2.5 3.1

Maximum 3.4 4.5 5.5 6.4 7.6 9.2 6.3 7.3

Minimum 0.6 1.2 1.6 1.8 1.2 0.9 1.1 1.8

North Prong Alafia River

1 2.7 4.0 4.7 5.2 2.9 1.6 2.1 3.5

2 2.8 4.1 4.8 4.8 1.0 2.2 3.0 4.2

3 2.3 3.7 3.7 1.9 1.8 1.3 2.5 3.8

4 1.7 3.0 3.7 2.3 1.6 2.2 2.4 3.6

5 1.6 3.0 3.8 3.4 2.7 4.0 4.9 5.5

6 Railroad Bridge

7 1.2 2.4 3.1 2.6 2.4 3.9 4.8 4.2

7.5 1.5 2.6 3.5 4.1 5.0 4.7 3.1 3.0

8 1.8 2.9 3.6 4.1 4.4 1.9 2.1 3.2

9 1.9 3.2 3.9 4.5 5.5 1.8 1.5 2.4

10 1.1 2.2 2.9 3.4 4.4 0.9 1.8 3.1

11 Railroad Bridge

12 1.1 2.0 2.7 3.1 4.1 0.9 1.9 3.2

13 1.2 2.0 2.6 3.0 3.9 1.1 1.9 2.8

14 0.6 1.4 1.9 2.4 3.3 5.5 6.4 6.7

15 SR 676 Bridge and Gaging Station

16 0.7 1.4 2.0 2.4 3.3 5.6 6.4 6.9

16.5 0.7 1.4 2.0 2.4 3.3 3.1 2.5 3.0

17 1.0 1.4 1.6 1.9 2.4 1.2 1.5 2.1

18 1.6 2.3 2.8 3.0 3.1 2.8 1.5 1.8

19 2.2 3.3 1.2 1.3 1.5 2.5 3.3 3.9

20 2.2 3.6 4.4 0.5 0.8 2.1 3.1 4.1

21 2.3 3.8 1.8 1.6 1.2 1.4 1.9 2.8

22 2.6 4.3 1.7 0.8 1.0 2.3 3.2 4.1

23 1.9 3.5 1.0 1.1 1.4 2.4 3.3 4.1

Mean 1.6 2.8 2.9 2.7 2.8 2.5 3.0 3.7

Maximum 2.8 4.3 4.8 5.2 5.5 5.6 6.4 6.9

Minimum 0.6 1.4 1 0.5 0.8 0.9 1.5 1.8

Appendix R. Hydraulic depth at cross sections along the 

Alafia, North Prong Alafia, and South Prong Alafia Rivers for 

selected percentile discharges (Continued)

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Feet

South Prong Alafia River

1 2 3.1 2.7 2 1.9 1.9 3.0 4.3

2 2.2 3.5 2.5 2 1.2 1.7 2.5 3.6

3 0.7 1.4 1.5 1.6 1.3 0.9 1.8 2.9

4 1.6 2.1 2.3 2.3 0.8 1.3 2.0 3.0

5 1.8 0.9 1.2 1.5 1.6 2.5 2.5 3.1

6 1.5 2.7 2.8 3 3.3 3.8 1.1 1.5

6.5 1.5 3 3.8 2.3 2.7 2.7 1.9 2.4

7 0.9 1.1 1.7 2.2 2.7 3.7 3.5 4.2

8 SR 640

9 0.9 1.1 1.7 2.2 2.7 3.7 3.5 4.2

9.5 0.9 2.3 3.1 3.4 3.2 3.0 3.5 3.9

10 0.3 0.8 1.4 1.8 2.2 1.0 1.7 2.2

11 1.2 2.1 2.1 1.9 1.7 1.3 1.3 1.7

12 1.2 2.3 1.3 1.4 1.1 1.2 1.5 2.1

13 1.3 1.9 2.1 1.9 1.8 1.2 1.6 2.2

14 1.5 1.7 1.1 1 1.0 1.4 1.9 2.4

15 1.2 2.3 2.6 2.6 2.6 1.1 1.2 1.5

16 1.3 2.5 2.9 2.8 1.6 1.3 1.8 2.4

17 1.4 2.5 1.3 1 1.1 1.5 1.9 2.3

18 1.2 2 1.4 1.5 1.7 0.8 1.2 1.9

19 1.8 3.1 1.3 1.4 1.5 1.0 1.5 2.1

20 0.8 2.2 3 3.4 3.9 0.6 0.9 1.5

21 1.2 2.4 3.2 3.7 1.2 1.2 1.7 2.2

21.5 1 2.1 2.9 3.4 1.4 0.8 1.3 1.9

22 1.2 2.4 3.1 3.6 4.3 1.3 1.8 2.4

23 Jameson Road and Gaging Station

24 1.3 2.4 3.2 3.6 4.4 1.4 1.9 2.5

24.5 1 2 2.7 3.1 1.6 1.0 1.5 2.1

25 1.1 2.2 3 3.5 4.3 0.9 1.2 1.5

26 0.7 1.6 2.3 2.8 3.7 0.9 1.6 2.2

27 1.5 2.5 3.2 3.7 0.7 1.2 1.5 2.1

28 0.9 1.7 2.3 2.7 3.2 1.0 1.2 1.9

29 0.8 1.5 2 2.3 2.9 0.8 1.3 1.7

Mean 1.2 2.1 2.3 2.4 2.2 1.6 1.8 2.5

Maximum 2.2 3.5 3.8 3.7 4.4 3.8 3.5 4.3

Minimum 0.3 0.8 1.1 1 0.7 0.6 0.9 1.5
90 Extent of Areal Inundation of Riverine Wetlands Along Cypress Creek and the Peace, Alafia, North Prong Alafia, and 

South Prong Alafia Rivers, West-Central Florida

Appendix S. Acreage of areal inundation between adjacent cross 

sections along the Alafia, North Prong Alafia, and South Prong 

Alafia Rivers for selected percentile discharges

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Acres

Alafia River

73 SR 640 Bridge and Alafia River near Lithia Gaging Station

74

75 0.1 0.1 0.1 0.1 0.1 0.1 1.3 2.4

76 0.8 0.9 1 1.1 1.4 12.7 29.4 54.6

77 2.3 3 3.4 3.6 10.9 74.4 97.5 119.8

78 4.5 5.1 5.5 5.8 12.7 63.4 109.8 143.2

79 3.7 4 4.2 4.4 4.7 14.5 96.4 151.3

80 3.8 4.5 5 5.4 6 15.3 61.6 103.7

81 3.2 3.6 4.1 4.4 4.9 12.9 50.2 78.7

82 1.1 1.2 1.1 1.2 1.3 4.0 22.4 34.1

83 Railroad Bridge

84 0.1 0.1 0.1 0.1 0.5 1.4 1.8

85 3 3.3 3.4 3.5 3.8 15.3 54.6 70.0

86 3.2 3.3 3.3 3.4 3.5 11.8 38.7 46.2

87 5 5.1 5.3 5.3 5.5 44.8 70.4 78.2

88 2.5 2.6 2.7 2.8 2.8 47.1 60.2 63.1

89 3.9 4.6 5 5.3 6 90.8 118.1 127.9

90 3.5 4.2 4.8 5.1 9.5 74.9 103.0 110.0

91 1.5 2 2.1 2.4 8.2 62.3 75.3 79.6

92 2.9 3.6 4.2 4.8 8.4 73.7 85.5 94.1

93 3.8 4.1 4.5 4.7 5.2 33.6 39.1 43.3

94 SR 39 Bridge

95 0.6 0.6 0.7 0.7 0.8 2.3 2.5 2.8

96 3.7 4.4 6.2 7.5 9.4 27.5 33.4 40.2

Total 53 60 67 72 105 682 1,151 1,445

North Prong Alafia River

1

2 1.2 1.3 1.3 1.4 5.9 26.9 37.5 39.9

3 3.3 3.6 4.0 5.8 14.4 51.8 59.9 63.6

4 2.0 2.3 2.6 4.9 10.5 38.5 52.5 55.9

5 1.4 1.6 1.7 2.6 5.8 12.8 22.6 24.5

6 Railroad Bridge

7 0.1 0.1 0.2 0.2 0.4 0.5 0.6 0.7

7.5 0.2 0.2 0.2 0.2 0.3 0.5 0.7 1.1

8 2.5 2.7 2.8 2.9 3.2 13.2 32.6 38.1

9 2.8 2.9 3.1 3.2 3.6 24.0 63.6 76.2

10 1.6 1.8 1.8 1.9 2.0 17.0 38.7 46.1

11 Railroad Bridge

12 0.1 0.1 0.1 0.1 0.1 1.4 2.4 2.6

13 0.3 0.3 0.4 0.4 0.4 5.3 8.7 9.6

14 1.9 1.9 1.9 2.0 2.0 9.9 14.8 19.8

15 SR 676 Bridge and Gaging Station

16 0.6 0.6 0.6 0.6 0.6 1.1 1.5 2.1

16.5 2.2 2.3 2.3 2.3 2.3 6.0 10.4 15.2

17 7.3 7.5 7.7 7.8 8.1 22.6 47.0 64.9

18 3.6 4.3 4.8 5.1 5.9 13.9 31.1 43.2

19 2.0 2.4 4.7 5.7 8.1 15.7 27.1 34.7

20 2.1 2.3 5.4 18.5 32.5 43.1 49.2 54.6

21 3.4 3.7 5.9 22.7 42.1 58.5 68.2 74.2

22 5.5 6.1 15.2 36.7 68.0 93.5 108 116

23 4.2 4.7 16.6 33.9 54.2 62.4 66.5 71.5

Total 48.2 52.5 83.1 159 270 518 743 854

Appendix S. Acreage of areal inundation between adjacent cross 

sections along the Alafia, North Prong Alafia, and South Prong 

Alafia Rivers for selected percentile discharges (Continued)

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Acres

South Prong Alafia River

1

2 1.1 1.2 1.8 2.8 6.3 32.2 34.5 36.1

3 3.1 5.3 7.6 10.1 22.6 79.6 86.2 91.5

4 1.3 2.5 3.5 4.6 12.7 35.7 38.1 39.3

5 2.0 5.6 8.8 10.6 20.1 33.9 40.9 45.2

6 1.8 4.9 7.7 9.0 12.6 15.5 28.6 40.6

6.5 0.8 0.8 0.9 1.4 1.5 2.3 7.0 10.1

7 0.5 0.9 1.0 1.3 1.5 2.1 5.8 8.2

8 SR 640 Bridge

9 0.1 0.2 0.3 0.3 0.3 0.4 0.6 0.8

9.5 0.5 0.7 0.8 0.9 1.0 1.6 2.7 3.7

10 2.4 2.8 3.0 3.2 4.1 10.4 13.0 15.8

11 1.4 1.7 2.3 3.0 4.0 16.3 24.5 32.4

12 2.8 3.4 7.4 10.7 17.3 40.9 58.3 68.4

13 1.0 1.4 3.8 5.5 9.9 31.7 39.2 43.0

14 1.1 2.3 4.8 7.2 13.2 29.4 33.4 37.2

15 2.0 3.5 6.5 9.1 15.5 28.2 37.3 44.8

16 2.2 2.7 3.4 4.2 7.2 31.4 42.1 51.0

17 1.3 1.5 2.7 5.3 9.7 28.1 32.9 37.6

18 1.0 1.4 3.6 6.4 9.5 28.1 34.1 38.5

19 1.0 1.4 4.1 5.2 6.6 30.9 36.2 39.1

20 1.4 1.7 4.4 5.6 7.1 60.7 72.6 76.2

21 0.7 0.8 0.9 0.9 3.1 38.9 43.8 44.9

21.5 0.2 0.2 0.3 0.3 1.1 8.2 8.4 8.7

22 0.2 0.2 0.2 0.2 0.5 5.2 6.3 7.3

23 Jameson Road and Gaging Station

24 0.0 0.1 0.0 0.0 0.0 0.6 0.8 0.9

24.5 0.2 0.2 0.2 0.3 0.5 6.1 7.3 8.5

25 0.9 1.1 1.2 1.3 2.6 26.6 31.6 38.0

26 1.1 1.2 1.3 1.3 1.4 24.8 30.5 37.6

27 1.7 1.9 2.1 2.2 9.0 36.9 42.6 47.6

28 0.8 1.0 1.2 1.3 6.4 28.7 39.8 45.7

29 1.8 2.3 2.7 3.0 3.4 33.5 47.7 56.3

Total 36.6 54.9 88.4 117 211 749 927 1,055
Appendices 91

Appendix T. Decrease of inundated acreage resulting from a 

potential 10-percent discharge withdrawal at cross sections 

along the Alafia, North Prong Alafia, and South Prong Alafia 

Rivers for selected percentile discharges

[Blanks indicate no decrease in inundated acreage]

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Acres

Alafia River

73 SR 640 Bridge and Alafia River near Lithia Gaging Station

74

75 0.3 0.1

76 0.1 0.7 2.8 1.6

77 0.1 0.1 0.1 6.6 2 6.7 2.4

78 0.1 0.1 0.1 0.1 6.6 4.4 7.7 2.7

79 0.1 0.1 0.1 5.6 7.3 13.1

80 0.1 0.1 0.1 0.1 0.2 6.1 6.8 12.8

81 0.1 0.1 0.2 0.1 5.6 6.9 5

82 0.1 1.2 3 2.1

83 Railroad Bridge

84 0.1 0.2

85 0.1 0.1 2.2 2.4 26

86 0.1 0.1 0.8 1.2 17.4

87 0.1 5.2 2.3 0.4

88 0.1 6.2 1.4 0.4

89 0.1 0.2 0.1 0.1 0.2 14.7 3.7 1

90 0.2 0.1 2.4 12.7 2.7 0.7

91 0.2 0.1 2.5 4.9 0.8 1

92 0.1 0.1 0.3 0.9 1.1 1.7 1.3

93 0.1 0.1 0.3 0.9 0.4

94 SR 39 Bridge

95 0.1 0.1 0.1 0.1

96 0.2 0.4 0.5 0.5 1.7 1.1 1

Total 0.7 1.2 1.6 1.8 20.6 75.4 59.9 89.5

North Prong Alafia River

1

2 0.5 0.6 3.9 1.2 0.9 0.8

3 0.1 0.2 1.1 6.2 7.7 1 0.9

4 0.2 1.7 1.3 8.5 0.7 0.7

5 0.1 0.9 0.7 2.4 0.4 0.5

6 Railroad Bridge

7 0.1 0.1

7.5 0.1 0 0.2

8 0.1 0.3 0.5 0.9

9 0.1 0.1 1.3 5.8 1.6

10 0.1 0.1 0.1 5.1 4.2 0.9

11 Railroad Bridge

12 0.4

13 1.3 0.3 0.2

14 0.1 0.1 1 2 0.8

15 SR 676 Bridge and Gaging Station

16 0.2 0.2

16.5 0.4 1.8 0.8

17 0.1 4.9 5.1 3.4

18 0.1 0.1 0.2 0.2 0.3 3.1 3.8 1.8

19 0.8 0.5 1 0.8 3 1.1

20 0.9 6.1 3.5 1 1.2 1.2

21 0.1 0.1 1.7 7.8 4.5 2.1 1.5 1.1

22 0.1 4.4 10.4 4.6 3.3 2.4 1.2

23 0.2 3.6 8.2 2.5 0.7 0.8 1.3

Total 0.4 0.4 12.8 37.8 29.1 45.5 35.6 19.6

Appendix T. Decrease of inundated acreage resulting from a 

potential 10-percent discharge withdrawal at cross sections 

along the Alafia, North Prong Alafia, and South Prong Alafia 

Rivers for selected percentile discharges (Continued)

[Blanks indicate no decrease in inundated acreage]

Cross 

section

Percentiles

P10 P50 P70 P80 P90 P98 P99.5 P99.9

Acres

South Prong Alafia River

1

2 0.3 0.5 1.8 0.6 0.3 0.4

3 0.1 0.2 0.6 1.1 3.8 28.7 0.9 1.2

4 0.2 0.2 0.4 3.5 13.2 0.2 0.3

5 0.7 0.5 0.6 4.3 0.9 1.4 0.5

6 0.6 0.4 0.4 0.3 0.4 3.7 0.6

6.5 0.2 0.9 0.2

7 0.1 0.1 0.3 0.9

8 SR 640 Bridge

9 0.1

9.5 0.1 0.1 0.1 0.4

10 0.1 0.1 0.1 0.6 0.5 0.5 0.5

11 0.3 0.2 0.3 1.1 2.0 0.9

12 1.1 1.0 1.2 2.3 6.2 1.2

13 0.1 0.4 0.7 0.7 1.1 3.2 0.8

14 0.2 0.6 1.3 1.4 0.8 0.8 0.8

15 0.3 0.7 1.2 1.5 2.0 1.4 1.7

16 0.1 0.3 0.3 0.8 2.3 1.8 1.9

17 1.0 0.9 1.1 1.2 1.0 1.1

18 1.1 0.9 0.7 2.5 0.8 1.0

19 0.4 0.3 0.3 3.4 0.6 0.4

20 0.4 0.4 0.4 3.5 6.0 0.5

21 0.8 0.7 3.1 0.3

21.5 0.3 0.1 0.1 0.1

22 0.1 0.2 0.3 0.1

23 Jameson Road and Gaging Station

24

24.5 0.2 0.2 0.3 0.1

25 0.9 1.0 1.2 1.4

26 1.2 1.3 1.6

27 1.8 1.4 1.0 0.8

28 1.3 2.4 2.3 0.8

29 0.1 0.1 0.1 0.1 2.9 3.1 1.4

Total 0.2 2.7 8.4 10.4 28.3 75.0 44.8 22.0