Forest Types in the Lower Suwannee River

Floodplain, Florida −

A Report and Interactive Map

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the

Suwannee River Water Management District

WaterResources 

Investigations 

Report 03-4008

Suwannee River

Manatee

Springs

transect
U.S. GEOLOGICAL SURVEY

Water Resources Investigations Report 03-4008

Forest Types in the Lower Suwannee River 

Floodplain, Florida—A Report and 

Interactive Map

Tallahassee, Florida

2003

Prepared in cooperation with the

SUWANNEE RIVER WATER MANAGEMENT DISTRICT

By Melanie R. Darst, Helen M. Light, Lori J. Lewis, and A. Alejandro Sepúlveda
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

The use of firm, trade, and brand names in this report is for identification purposes only 

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

For additional information

write to:

District Chief

U.S. Geological Survey

Suite 3015

227 N. Bronough Street

Tallahassee, FL 32301

Additional information about water resources in Florida is available on the 

Internet at http://fl.water.usgs.gov

U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

CHARLES G. GROAT, Director
Contents III

CONTENTS

List of Scientific Names used with Common Name Equivalents.......................................................................................... VI

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

Introduction ........................................................................................................................................................................... 2

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

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

Setting .......................................................................................................................................................................... 2

Methods ................................................................................................................................................................................. 3

Floodplain Boundaries and River Kilometers.............................................................................................................. 3

Study Sites ................................................................................................................................................................... 3

Transects ............................................................................................................................................................ 6

Establishment of Transects ..................................................................................................................... 6

Vegetation Sampling................................................................................................................................ 6

Verification Plots ............................................................................................................................................... 7

Observation Sites ............................................................................................................................................... 7

Reach Boundaries ........................................................................................................................................................ 7

Mapping Aerial Signatures .......................................................................................................................................... 7

Map Verification, Completion, and Conversion to Interactive Format........................................................................ 9

Floodplain Hydrology, Topographic Features, and Soils ...................................................................................................... 11

Hydrology of the River ................................................................................................................................................ 11

Floodplain Topography and Hydrology....................................................................................................................... 12

Floodplain Soils ........................................................................................................................................................... 12

Major Forest Types ................................................................................................................................................................ 12

Oak/pine Uplands ........................................................................................................................................................ 13

Riverine Wetland Forests ............................................................................................................................................. 14

Upper Tidal Wetland Forests ....................................................................................................................................... 15

Lower Tidal Wetland Forests ....................................................................................................................................... 18

Other Land Cover Types........................................................................................................................................................ 20

Uses of the Forest Map.......................................................................................................................................................... 22

Summary................................................................................................................................................................................ 22

References ............................................................................................................................................................................. 23

FIGURES

1-2. Maps showing:

1. Drainage basin of the Suwannee River in Florida and Georgia...................................................................... 3

2. Study area with locations of reaches, gaging stations, and study sites in the floodplain of the 

lower Suwannee River, Florida. ...................................................................................................................... 4

3. Flow chart of methods for mapping and defining forest types in the lower Suwannee River floodplain................ 8

4. Mapping of the floodplain of the lower Suwannee River, Florida, was based on aerial signatures at 

transects and other study sites.................................................................................................................................. 9

5-6. Graphs showing:

5. Area of land cover types in the 10-year floodplain and main channel of the lower 

Suwannee River, Florida ................................................................................................................................. 12

6. Area of major wetland forest types in the floodplain of the lower Suwannee River, Florida......................... 14
IV Contents

7-18. Photographs showing:

7. Large Quercus virginiana and Quercus laurifolia trees dominate the canopy of a high bottomland 

hardwood forest in the riverine reach of the floodplain of the lower Suwannee River, Florida..................... 14

8. The flared base of Ulmus americana growing in a low bottomland hardwood forest in the riverine 

reach of the floodplain of the lower Suwannee River, Florida. ...................................................................... 15

9. Taxodium distichum trees growing in a dense stand in a riverine swamp in the floodplain of the 

lower Suwannee River, Florida....................................................................................................................... 16

10. Bottomland hardwood trees such as Quercus laurifolia (in right foreground) are the dominant canopy 

species in the most elevated wetlands of the upper tidal reach of the lower Suwannee River, Florida.......... 17

11. The bases of trunks of Nyssa aquatica are usually swollen in upper tidal swamps in the floodplain of

the lower Suwannee River, Florida................................................................................................................. 17

12. Sabal palmetto is the dominant canopy species in lower tidal hammocks in the floodplain of the

lower Suwannee River, Florida....................................................................................................................... 18

13. A dense stand of canopy trees in a lower tidal swamp in the floodplain of the lower Suwannee 

River, Florida. ................................................................................................................................................. 19

14. A stunted stand of Fraxinus profunda trees growing along East Pass near the tree line in the lower 

Suwannee River floodplain, Florida ............................................................................................................... 19

15. The main channel of the lower Suwannee River, Florida, covers 1,767 hectares of the total area 

mapped (21,170 hectares)............................................................................................................................... 20

16. An open water pond in the floodplain of the riverine reach of the lower Suwannee River, Florida .............. 20

17. Marshes, including this freshwater marsh near Gopher River, cover 425 hectares of land upstream

of the tree line in the floodplain of the lower Suwannee River, Florida......................................................... 21

18. Floodplain glades are non-forested areas in the lower Suwannee River floodplain, Florida, that 

usually have a thick ground cover of grasses and sedges............................................................................... 21

TABLES

1. Location and sampling area of transects and verification plots in the lower Suwannee River 

floodplain, Florida .................................................................................................................................................. 6

2. Rules for testing mapped forest types at verification plots in the floodplain of the lower 

Suwannee River, Florida......................................................................................................................................... 10

3. Mapping accuracy based on tests of forest type rules at verification plots in the floodplain of the 

lower Suwannee River, Florida............................................................................................................................... 11

4. Summary of hydrologic conditions, soil textures, and dominant canopy species of forest types in the 

10-year floodplain of the lower Suwannee River, Florida...................................................................................... 13
Contents V

Conversion Factors and Unit Abbreviations

In this report, horizontal coordinate information is referenced to the North American Datum of 1929 (NGVD of 1929).

Acronyms and Abbreviations

 Multiply By To obtain

centimeter (cm) 0.3937 inch (in.)

meter (m) 3.28 foot (ft)

kilometer (km) 0.62 mile (mi)

river kilometers (rkm) 0.62 river miles

square meter (m2) 10.76 square foot (ft2)

square kilometer (km2) 0.3861 square mile (mi2)

hectare (ha) 2.471 acre

hectare (ha) 0.003861 square mile (mi2)

cubic meter per second (m3/s) 35.31 cubic foot per second (ft3/s)

degree Celsius (°C) 1.8 ( + 32 °) degree Fahrenheit (°F)

DOQ Digital Orthophoto Quadrangles

GIS Geographic Information System

LSNWR Lower Suwannee National Wildlife Refuge

PLGR Precise Lightweight Global Positioning System Receiver

SRWMD Suwannee River Water Management District

USGS U.S. Geological Survey

blh bottomland hardwoods

dbh diameter at breast height

rba relative basal area

sw swamps

ham hammocks

up upland
VI Contents

1 Clewell (1985)

2 Lelong (1984)

LIST OF SCIENTIFIC NAMES USED WITH COMMON NAME EQUIVALENTS

[Plant nomenclature used in this report follows that by Godfrey and Wooten (1979, 1981) unless otherwise 

indicated. For species with only one variety present in the study area, variety names have been omitted in the

 body of the report]

Scientific name Common name

Betula nigra L river birch

Cladium jamaicense Crantz sawgrass

Fraxinus profunda (Bush) Bush pumpkin ash

Hydrocotyle verticillata Thunb. whorled marsh pennywort

Liquidambar styraciflua L. sweetgum

Magnolia virginiana L. sweetbay

Nyssa aquatica L. water tupelo

Nyssa biflora (Walt.) Walt.1 swamp gum

Panicum rigidulum Bosc ex Nees2

var. pubescens (Vasey) Lelong

panic grass 

Persea palustris (Raf.) Sarg. swamp red bay

Pilea pumila (L.) A. Gray clearweed

Pinus taeda L. loblolly pine

Planera aquatica J. F. Gmel. planer-tree

Quercus geminata Small sand live oak

Quercus hemisphaerica Bartr. Ex Willd. laurel oak

Quercus laurifolia Michx. swamp laurel oak

Quercus lyrata Walt. overcup oak

Quercus virginiana Mill. live oak

Rumex verticillatus L. swamp dock

Sabal palmetto Lodd. ex J. S. Shult. & J. H. Shult. cabbage palm

Sagittaria lancifolia L. arrowhead

Taxodium distichum (L.) L. C. Rich. bald cypress

Zizaniopsis miliacea (Michx.) Döll. & Asch. southern wild rice 
Abstract 1

Forest Types in the Lower Suwannee River Floodplain, 

Florida—A Report and Interactive Map

By Melanie R. Darst, Helen M. Light, Lori J. Lewis, and A. Alejandro Sepúlveda

Abstract

A map of forest types in 

the lower Suwannee River floodplain, Florida, was created during a study conducted from 1996 

to 2000 by the U.S. Geological 

Survey in cooperation with the 

Suwannee River Water Management District. The map is presented with this report on a 

compact disc with interactive 

viewing software. The forest 

map can be used by scientists for 

ecological studies in the floodplain based on land cover types 

and by landowners and management personnel making land use 

decisions.

The study area is the 

10-year floodplain of the lower 

Suwannee River from its confluence with the Santa Fe River to 

the lower limit of forests near 

the Gulf of Mexico. The floodplain is divided into three 

reaches: riverine (non-tidal), 

upper tidal, and lower tidal, due 

to changes in hydrology, vegetation, and soils with proximity to 

the coast.

The 10-year floodplain 

covers about 21,170 hectares; 

nearly 88 percent of this area 

(18,580 hectares) is mapped as 

14 major forest types. Approximately 29 percent (5,319 hectares) of these forests have been 

altered by agriculture or development. About 75 percent of the 

area of major forest types 

(13,994 hectares) is wetland forests and about 25 percent 

(4,586 hectares) is upland forests. Tidal wetland forests 

(8,955 hectares) cover a much 

greater area than riverine wetland forests (5,039 hectares).

 Oak/pine upland forests 

are present in the riverine and 

upper tidal reaches of the floodplain on elevations that are inundated only briefly during the 

highest floods. High bottomland 

hardwoods are present on the 

higher levees, ridges, and flats of 

the riverine reach where soils are 

usually sandy. Low bottomland 

hardwood forests are present in 

the riverine reach on swamp 

margins and low levees and flats 

that are flooded continuously for 

several weeks or longer every 

1 to 3 years. Riverine swamps 

are present in the lowest and wettest areas of the non-tidal floodplain that are either inundated or 

saturated most of the time.

Upper tidal bottomland 

hardwood forests are present on 

sandy soils on high flats and in 

transitional areas between 

upland forests and swamps. 

Upper tidal mixed forests are 

found on low levees or between 

swamps and higher forest types. 

Upper tidal swamps are present 

at elevations below median 

monthly high stage and usually 

have surface soils that are permanently saturated mucks.

Lower tidal hammocks are 

found on higher elevations that 

do not receive regular tidal inundation but have a high water 

table and are briefly inundated 

by storm surges several times a 

decade. Lower tidal mixed forests include swamps with 

numerous small hummocks or 

less common larger hummocks. 

Lower tidal swamps are found 

on deep muck soils that are 

below the elevation of the 

median daily or monthly high 

stage.
2 Forest Types in the Lower Suwannee River Floodplain, Florida—A Report and Interactive Map

Seven additional land 

cover types (2,590 hectares) are 

mapped. Water in the main channel of the lower Suwannee River 

(1,767 hectares) was mapped 

separately from open water in 

the floodplain (239 hectares). 

Other land cover types are: 

seepage slopes (70 hectares), 

isolated forested wetlands 

(19 hectares), marshes upstream 

of the tree line (505 hectares), 

beds of emergent aquatic vegetation (21 hectares), and floodplain 

glades (46 hectares).

INTRODUCTION

River floodplains provide storage and filtration of surface water, 

diverse habitats for plants and animals, corridors for the movement of 

animals and dissemination of 

plants, and a supply of nutrients to 

estuarine environments. Floodplain 

functions and their contribution to 

ecological integrity have been 

described by many authors, and the 

need for protection is generally 

acknowledged by the scientific 

community (Greeson and others, 

eds., 1979; Brinson and others, 

1981; Clark and Benforado, eds., 

1981; Wharton and others, 1982; 

Gosselink and others, 1990; Lugo 

and others, eds., 1990; Mitsch and 

Gosselink, 1993; Davis and others, 

1996; Messina and Conner, eds., 

1998).

Wetlands protection is an 

important goal of water management in the Suwannee River basin. 

Florida law directs water management districts to use best available 

information to establish minimum 

flows and levels for watercourses in 

their districts. A series of studies 

was undertaken by the U.S. 

Geological Survey (USGS), in 

cooperation with the Suwannee 

River Water Management District 

(SRWMD), to describe the water 

resources and ecology of the lower 

Suwannee River. In one of those 

studies, Light and others (2002) 

described the hydrology, vegetation, 

and soils of the forested floodplain 

of the lower Suwannee River and 

potential impacts of flow reductions. A map of the lower Suwannee 

River floodplain created during that 

study is described and presented 

with this report.

Purpose and Scope

The objective of this report is to 

describe and present a map of forest 

types in the lower Suwannee River 

floodplain, Florida. The study area is 

the floodplain of the lower Suwannee 

River from its confluence with the 

Santa Fe River to the downstream 

limit of forests near the Gulf of Mexico (fig. 1). Mapping began in 1997 

and continued through 2000.

Acknowledgments

The authors are grateful to Rob 

Mattson and John Good, SRWMD, 

and S. Jack Alhadeff and Jonathan 

Musser, USGS, for review of this 

report and map. The authors also 

appreciate the assistance of the following USGS staff with report production: John D. Guthrie for 

computer programming; Teresa 

Embry for technical and editorial 

reviews; Ron Spencer for graphics; 

and Pat Mixson for layout.

Extensive fieldwork was 

needed to accomplish the mapping 

project. Access to study sites and 

logistical support from landowners 

was received from Ken Litzenberger, 

Lower Suwannee National Wildlife 

Refuge (LSNWR); Paul Perras, 

Manatee Springs State Park; Greg 

Galpin, Georgia-Pacific Corporation; Jeff King, Andrews Wildlife 

Management Area; Robert Heeke, 

SRWMD; and John R. Falkenburry, 

private landowner. Many people 

contributed hundreds of hours of 

invaluable assistance with field 

work, including the verification of 

mapped forest types: Lani Webster, 

Angus Gholson, Duncan Johnson, 

Jill Pittman, Donald Foose, Venu 

Oddiraju, Robert Tighe, volunteers; 

Henry Sansing, Russ Langford, 

Kenny McCain, Kendall Smith, 

LSNWR; Kathy Burks, Florida 

Department of Environmental Protection; Dennis Hardin and Penny 

Isom, Florida Division of Forest 

Management; Kip Runyon, Florida 

Fish and Wildlife Conservation 

Commission; Rob Mattson, John 

Good, Christine Sutter, Eric Lewis, 

Kelly Chancey, and Susie Hetrick, 

SRWMD; Gary Mahon, and Ed 

Oaksford, USGS.

Setting 

The Suwannee River flows from 

its headwaters in the Okefenokee 

Swamp to the Gulf of Mexico 

(fig. 1). The drainage basin covers 

approximately 25,770 square kilometers (km2

) of the Gulf Coastal 

Plain in central southern Georgia and 

central northern Florida (Berndt and 

others, 1996). The lower Suwannee 

River refers to that portion of the 

river from its confluence with the 

Santa Fe River to the mouth of the 

river at the Gulf of Mexico. The 

lower Suwannee River flows through 

the Gulf Coastal Lowlands physiographic region (Puri and Vernon, 

1964). Stream characteristics in the 

lower Suwannee River show a combination of blackwater and springfed influences, with some alluvial 

features in the floodplain. Limestone 
Methods 3

is at or near land surface in the lower 

Suwannee River basin. Solution features, such as sinkholes, sinkhole 

lakes, springs, and submerged caves, 

are common in the basin. Surfacewater streams in the non-tidal portion 

of the river are fed predominantly by 

springs rather than from surface runoff (Crane, 1986). Tidal creeks are 

present in the floodplain of the tidal 

portion of the river and increase in 

number and extent with proximity to 

the Gulf of Mexico.

The warm, temperate climate 

of the lower Suwannee River floodplain is characterized by long, 

humid summers and mild, dry 

winters. Average annual precipitaAlbany

GEORGIA

FLORIDA

Tallahassee

Gulf

o f

Mexico

A t l a n t i c O c e a

Jacksonville n

30 KILOMETERS

30 MILES

0 20

0 20

Gainesville

Lake

City

84°

32°

31°

30°

29°

83° 82°

Suwannee

Fe River Santa

Withlacoochee

River

Ala ha pa Rive

R

r

iver

Valdosta

Cedar

Key

EXPLANATION

GA

SUWANNEE RIVER DRAINAGE BASIN

STUDY AREA

OKEFENOKEE SWAMP

FL

Location

map

Area shown

in figure 2

Base from U.S. Geological Survey digital data, 1972

Albers Equal-Area Conic Projection,

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

Figure 1. Drainage basin of the Suwannee River in Florida and Georgia ( from 

Light and others, 2002).

tion (1961-90) at Cross City is 

146 centimeters (cm) (Owenby and 

Ezell, 1992). Average summer air 

temperature (June, July, and 

August) is 26.4 degrees Celsius 

(°C), and average winter air temperature (December, January, and 

February) is 12.1 °C at Cross City 

based on the period 1961 to 1990 

(Owenby and Ezell, 1992). The 

growing season (50 percent probability freeze-free period) varies 

from 259 days at the upstream end 

of the study area to 283 days near 

the mouth of the river (Bradley, 

1975). Annual flood peaks occur 

more often in the growing season 

than in the dormant season.

METHODS

Floodplain Boundaries 

and River Kilometers

The floodplain boundary in 

the non-tidal and upper tidal 

reaches of the lower Suwannee 

River is the 10-year floodplain digitized by the SRWMD from data 

collected by the U.S. Army Corps 

of Engineers. The floodplain 

boundary in the lower tidal reach 

was determined by connecting the 

downstream limit of the 10-year 

floodplain boundary to the drainage basin boundary near the 

mouth, usually along roads or 

other obvious drainage divide features. The lower limit of the study 

area, near the mouth of the river, is 

the tree line, an east-west line 

across the lower tidal floodplain 

with primarily forests on the 

upstream side and marshes on the 

downstream side (fig. 2). River 

kilometers (rkm) indicate stream 

distances starting with rkm 0 at the 

mouth of the river at latitude 

29°17’19.2” and longitude 

83°9’51.8”.

Study Sites

Three types of study sites were 

used to collect data for map creation and verification. Transects 

were established for intensive 

collection of quantitative vegetation data used to interpret aerial 

signatures and define forest types. 

Verification plots were used to collect quantitative vegetation data to 

verify the forest map and describe 

forest types. Observation sites were 

used to obtain non-quantitative 

vegetation data to verify mapping 

signatures. Locations of all 

transects and verification plots are 

shown in figure 2.
4 Forest Types in the Lower Suwannee River Floodplain, Florida—A Report and Interactive Map

29°15′

29°30′

29°45′

30°00′

83°15′ 83°00′ 82°45′

Old Town

26

19

98 27

ALT

LAFAYETTE

DIXIE

LEVY

GILCHRIST

SUWANNEE

Chiefland

Cross City

Wannee

Fanning

Springs

Branford

Fowlers

Bluff

Suwannee Gulf of Mexico

27

ALT

98

19

27 Suwannee River

Suwannee River

Santa Fe River

Fort

White

COLUMBIA

INSET 1

INSET 2

INSET 1

98

19

27

ALT

26

29°30′

29°35′

29°45′

83°00′

29°40′

82°55′

29°50′

Base from U.S. Geological Survey digital data, 1972

Albers Equal-Area Conic Projection,

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

Base from U.S. Geological Survey digital data, 1972

Albers Equal-Area Conic Projection,

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

Manatee

Springs

Old

Town

Wannee

Fanning Springs

Suwannee River

70

40

50

60

80

90

100

MS

FK

LL

CF

0 2 4 MILES

0 2 4 KILOMETERS

0 4 8 MILES

0 4 8 KILOMETERS

Fort

White

gage

Branford

gage

Fort White

gage

FLOODPLAIN REACHES

Riverine

Riverine bottomland hardwoods and upper tidal swamps

Upper tidal

Lower tidal

Coastal marshes (not part of study area)

TRANSECT

LOWER SUWANNEE NATIONAL WILDLIFE REFUGE

DISTANCE FROM RIVER MOUTH, IN

KILOMETERS

VERIFICATION PLOT

GAGING STATION AND NAME

EXPLANATION

FK

60

349

349

Figure 2. Study area with locations of reaches, gaging stations, 

and study sites in the floodplain of the lower Suwannee River, 

Florida (modified from Light and others, 2002).
Methods 5

349

Fowlers

Bluff

Suwannee

Gulf of Mexico

Suwannee River

Suwannee

Sound

10

20

30

Wadley Pass

Pass Gopher River

East Pass

Alligator Pass

Sandfly

Creek

BC

SH

SN

KN

KI

TK

DM

LK

West

INSET 2

29°25′

29°20′

83°10′ 83°05′ 83°00′

0 2 4 MILES

0 2 4 KILOMETERS

Base from U.S. Geological Survey digital data, 1972

Albers Equal-Area Conic Projection,

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

Figure 2. Study area with locations of reaches, gaging stations, and study sites in the floodplain of the lower 

Suwannee River, Florida (modified from Light and others, 2002). (Continued)
6 Forest Types in the Lower Suwannee River Floodplain, Florida—A Report and Interactive Map

Transects

Establishment of transects -- 

Color-infrared photographs (scale 

1:40,000), taken in the winter of 

1994 by the National Aerial Photography Program, were used with 

maps of public lands to determine 

the location of transects. Transect 

locations were selected based on the 

need to adequately sample all major 

forest types within each reach at 

accessible sites where permanent 

transects could be established. Forest types were frequently differentiated in zones parallel to the river; 

therefore, most transects were 

located perpendicular to the river to 

sample vegetation growing in the

Table 1. Location and sampling area of transects and verification plots in the lower Suwannee River 

floodplain, Florida (modified from Light and others, 2002)

[rkm, river kilometers; m, meter; m2, square meters; blh, bottomland hardwoods; sw, swamps]

Reach Transect name or number of 

verification plots

Abbreviated 

transect 

name

Location,

 in rkm

Length of 

transect,

in m

Canopy plants

Area 

sampled, in 

m2

Number 

of plants 

sampled

Riverine

Confluence CF 104.3 441.0 4,400 293

Log Landing LL 77.6 921.2 4,606 189

Falkenburry FK 64.4 362.6 2,570 233

Manatee Springs (blh) MS 42.5 414.11

1The total length of the Manatee Springs transect is 1,009 meters.

3,330 145

58 verification plots 47.9 - 106.7 27,965 1,440

Upper

Tidal

Manatee Springs (sw) MS 42.5 594.91 4,189 392

Keen KN 31.2 734.1 3,709 329

Keen Island KI 31.2 100.0 1,000 21

24 verification plots 23.0 - 36.5 9,824 771

Lower

Tidal

Turkey Island TK 19.8 411.9 2,056 201

Sandfly North SN 13 88.3 1,148 110

Sandfly Hammock SH 12.6 151.0 1,510 102

Barnett Creek BC 11.3 215.6 2,126 235

Lock LK 5.1 145.5 1,455 184

Demory DM 4.8 53.2 532 86

29 verification plots 11.7 - 21.4 11,600 1,170

Subtotal for transects 4,633.4 32,631 2,520

Subtotal for verification plots -- 49,388 3,381

Total 3,624.4 82,019 5,901

center and in transitional areas at the 

edges of each forest type zone. Two 

transects were located in a homogeneous forest type for the purpose of 

sampling that specific type. Location, length, and compass bearings 

of transects were predetermined on 

aerial photographs and then located 

on the ground using a Precise Lightweight Global Positioning System 

Receiver (PLGR) with an approximate 4- to 6-meter (m) horizontal 

accuracy in real-time. Position coordinates at most transects were 

obtained on several field visits.

Twelve belt transects totaling 

about 4,600 m in length and 

33,000 square meters (m2) in area 

were established in the lower 

Suwannee River floodplain (fig. 2) 

(table 1). Details on the location of 

each transect are presented in Lewis 

and others (2002). Transects were 

visited many times throughout the 

data collection period.

Vegetation sampling -- Canopy 

plants were identified to species and 

measured for diameter at breast 

height (dbh) on belt transects 5-13 m 

in width. Canopy plants included all 

woody plants with a stem diameter 

of 10 cm or more measured at breast 

height and with a height of 3 m or 

taller. Swollen bases of trees were 

measured for dbh above the swelling. Trees with multiple trunks were 
Methods 7

considered canopy trees if any single trunk had a dbh of 10 cm or 

more. Trunks of all multipletrunked canopy trees were individually measured for dbh; basal areas 

for these trees were the sum of the 

basal areas of individual trunks. 

Subcanopy and ground-cover vegetation were also sampled and the 

results are presented in Light and 

others (2002) and Darst and others 

(2002), respectively. Only canopy 

plants were used to determine forest 

type. Relative basal area, the percentage of basal area of a species in 

a forest type or sampling area, was 

used to determine and compare forest composition. Relative basal area 

is calculated by dividing the total 

basal area of one species (in square 

meters) by the total basal area of all 

species in that forest type or sampling area.

Plant nomenclature used in this 

report follows that by Godfrey and 

Wooten (1979, 1981) unless otherwise indicated. Common names of 

all species mentioned are listed in 

the front of this report. For species 

with only one variety present in the 

study area, variety names have been 

omitted in the body of the report, 

but are included in the plant list in 

the front of the report.

Verification Plots

A total of 111 verification plots 

with a combined area of over 

49,000 m2

 were established in the 

lower Suwannee River floodplain 

(table 1). Coordinates for the centers of verification plots were 

obtained from Geographic Information System (GIS) aerial photographic images and then located in 

the field using the PLGR. Areas 

selected for verification had to be 

large enough to allow a possible 

field error of about 10-15 m in 

locating the center coordinates due 

to variation in the accuracy of the 

PLGR under forest cover. Some verification plots were located by pacing from known starting points. The 

centers of the plots were marked, 

and then circular plots were established using flagging and meter 

tapes. Plots with recent tree falls or 

obvious alteration (like roadbeds) 

were not used. Verification plots 

usually had a radius of 10 m in 

swamps and 13 m in uplands or bottomland hardwoods. Most verification plots were visited only once 

during the data collection period. 

Canopy plants were identified to 

species and measured using methods for transect sampling. Nine verification plots were used for basic 

data collection and interpretation of 

aerial signatures. The polygons containing these nine plots were 

mapped by forest type determined 

from field data. Mapped forest types 

of polygons containing the 102 plots 

used in map verification were not 

changed regardless of actual forest 

composition.

Observation Sites

About 150 observation sites 

were used for additional verification 

of forest type mapping signatures on 

aerial photography. Observation 

sites were identified on GIS aerial 

photographic images and then 

located in the field using the PLGR. 

At most observation sites, dominant 

tree species were recorded. Locations of observation sites are not 

shown on figure 2. Most observation 

sites were visited once, either during reconnaissance at the beginning 

of the study or later during forest 

map verification.

Reach Boundaries

Floodplain reaches are divisions 

of the floodplain in which hydrologic 

conditions and vegetation are relatively similar (Light and others, 

2002). Three reaches (riverine, upper 

tidal, and lower tidal) were defined 

based on the presence or absence of 

selected canopy species with distributions reflecting tidal influence, 

flood depths, and duration of inundation, and on changes in hydrology 

and soils with proximity to the coast. 

The floodplain from rkm 37 to 45.2 

(containing Manatee Springs and the 

MS transect) has riverine forest types 

on the higher elevations of the floodplain and upper tidal forest types on 

the lower elevations (fig 2).

Reach divisions were initially 

established using data from 

transects, then modified using 

results from verification plots. Divisions were placed halfway between 

the most downstream occurrence of 

a forest at a study site meeting the 

criteria of one reach and the most 

upstream occurrence of a forest 

meeting the criteria of the next 

downstream reach.

Mapping Aerial Signatures

Figure 3 is a flow chart showing the methods used to produce 

the forest map and define forest 

types. Digital orthophoto quadrangles (DOQ), developed from 

color-infrared photographs taken 

in 1994, scanned with 1 meter per 

pixel resolution, and rectified by 

USGS, were used as the basis for 

the floodplain map. The DOQ’s 

were transformed into grids and 

color values were enhanced with 

ARC-INFO programs and display 

options.

Transects were mapped in GIS 

by color signatures. Relative basal 

area was calculated and the canopy 

composition of segments of 

transects with similar signatures 

was analyzed. Minimum areas of 
8 Forest Types in the Lower Suwannee River Floodplain, Florida—A Report and Interactive Map

Floodplain areas containing

transects mapped by color

signatures using digital

orthophoto quadranges

(DOQ's)

Forest type defined for each color

signature using forest composition (in

relative basal area) of all transect

segments having the same signature

Mapping adjustments made to

obtain a best fit between

recognizable signatures and

reasonably consistent species

composition as each new

transect mapped

Forest type polygons mapped for the remainder of the floodplain

using signature definitions from transects (Preliminary reach

boundaries used in this step were finalized after verification)

Mapping adjustments made

based on vegetation data from

9 verification plots and about

Preliminary rules developed to test the canopy 150 observation sites

composition of mapped forest types

Basal area of canopy plants

at transects determined by

vegetation sampling

Preliminary verification completed for

map using data on basal area of canopy

plants from 102 verification plots

Reach boundaries finalized by placing the boundaries halfway between the most downstream

occurrence of a forest type (at any verification plot or transect) meeting the rule criteria of one reach

and the most upstream occurrence of a forest type meeting the criteria of the next downstream reach

Rules to test composition of 14 forest types finalized using new data

from 102 verification plots, but still based on composition of original

mapping data of 12 transects and 9 verification plots

VERIFICATION

(based on 102

verification plots)

AND FINAL MAPPING

PRELIMINARY MAPPING

Figure 3. Methods for mapping and defining forest types in the lower Suwannee River floodplain (modified from Light and 

others, 2000) .
Methods 9

314 m2 for swamp types and 500 m2

for uplands and bottomland hardwood forests were used for analyzing forest type composition. If 

insufficient area of a forest type was 

present at one transect, the data 

from that forest type were combined 

with data from the nearest transect 

with the same forest type, to calcuSu

wannee

e

Riv

r

Confluence

Transects

0 500 METERS

Figure 4. Mapping of the floodplain of the lower Suwannee River, Florida, was based on aerial signatures at 

transects and other study sites.

late species composition. Adjustments in mapping were made to get 

a best fit between recognizable signatures and forest composition. 

Aerial signatures at transects and 

nine verification sites were then 

used as a basis for mapping and 

labeling polygons in the rest of the 

floodplain on the map (fig. 4).

Map Verification, 

Completion, and Conversion 

to Interactive Format

Rules for determining reaches 

and forest types (table 2) were 

developed from the composition of 

mapped forest types on transects 

and nine verification plots that were 
10 Forest Types in the Lower Suwannee River Floodplain, Florida—A Report and Interactive Map

Table 2. Rules for testing mapped forest types at verification plots in the floodplain of the lower Suwannee River, Florida (from 

Light and others, 2002)

[All percentages are based on relative basal area (rba). The rba of a category is equal to the sum of the rbas of all species in that category. sw, swamp; blh, 

bottomland hardwood; ham, hammock; up, upland; >=, greater than or equal to; >, greater than; <=, less than or equal to; <, less than; %, percent]

Categories of species used in forest type 

determinations: Determination of reach:

Category Species 1) IF Sabal palmetto >= 60%, THEN reach is lower tidal.

sw

Cephalanthus occidentalis 1) IF Sabal palmetto < 60%, THEN

Fraxinus caroliniana 2) IF Magnolia virginiana > 0% OR IF Juniperus silicicola > 0%, THEN reach is lower tidal.

Fraxinus profunda 2) OR IF Magnolia virginiana = 0% AND Juniperus silicicola = 0%, THEN

Nyssa aquatica 3) IF sw (including Nyssa biflora) >= 40%, THEN

Nyssa biflora 2 4) IF Nyssa biflora + Fraxinus profunda >= 1%, THEN

Planera aquatica 5) IF Nyssa aquatica >= 5%, THEN reach is upper tidal.

Taxodium ascendens 5) OR IF Nyssa aquatica < 5%, THEN

Taxodium distichum 6) IF Fraxinus profunda + Nyssa biflora >= 40%, THEN reach is lower tidal.

blh

low 

Acer rubrum 6) OR IF Fraxinus profunda + Nyssa biflora < 40%, THEN reach is upper tidal.

Betula nigra 4) OR IF Nyssa biflora + Fraxinus profunda < 1%, THEN

Carya aquatica 5) IF Sabal palmetto >= 2% THEN reach is upper tidal.

Cornus foemina 5) OR IF Sabal palmetto < 2% THEN reach is riverine.

Crataegus viridis 3) OR IF sw (including Nyssa biflora) < 40%, THEN

Forestiera acuminata 4) IF Sabal palmetto >= 2%. THEN reach is upper tidal.

Gleditsia aquatica 4) OR IF Sabal palmetto < 2%, THEN 

Quercus laurifolia 5) IF Fraxinus profunda >= 1%, THEN reach is upper tidal.

Quercus lyrata 5) OR IF Fraxinus profunda < 1%, THEN reach is riverine.

Ulmus americana

Ulmus crassifolia Determination of forest type:

Vitis cinerea Riverine reach forest types:

high

Carpinus caroliniana 1) IF sw > 50% THEN,

Celtis laevigata 2) IF Planera aquatica >= 50%, THEN forest type is Rsw2.

Crataegus flava 2) OR IF Planera aquatica < 50% THEN,

Crataegus marshallii 3) IF blh < 15%, THEN forest type is Rsw1.

Diospyros virginiana 3) OR IF blh >= 15% THEN forest type is Rsw2.

Ilex decidua 1) OR IF sw <= 50% THEN,

Ilex opaca 2) IF blh > 50% THEN,

Liquidambar styraciflua 3) IF sw >= 1%, THEN forest type is Rblh1, 

Nyssa biflora 1 3) OR IF sw < 1% THEN,

Pinus glabra 4) IF high blh + up < 85%, THEN forest type is Rblh2,

Quercus michauxii 4) OR IF high blh + up >= 85%, THEN forest type is Rblh3.

Quercus nigra 2) OR IF blh <= 50%, THEN forest type is oak/pine.

Quercus virginiana Upper tidal reach forest types:

ham

Ilex cassine 1) IF sw >= 85%, THEN forest type is UTsw1.

Juniperus silicicola 1) OR IF sw < 85% THEN,

Myrica cerifera 2) IF sw >= 60%, THEN forest type is UTsw2.

Persea palustris 2) OR IF sw < 60% THEN,

Pinus elliottii 2 3) IF up <= 50% THEN,

Pinus taeda 2 4) IF ham + blh < 75%, THEN forest type is UTmix. 

Sabal palmetto 4) OR IF ham + blh >= 75%, THEN forest type is UTblh.

Viburnum obovatum 3) OR IF up > 50%, THEN forest type is oak/pine.

up

Carya glabra Lower tidal reach forest types:

Lyonia ferruginea 1) IF sw > 70% THEN,

Magnolia grandifolia 2) IF Fraxinus profunda + Nyssa biflora >= 60% THEN, 

Nyssa sylvatica 3) IF ham < 10% AND Magnolia virginiana < 6%, THEN forest type is LTsw1.

Persea borbonia 3) OR IF ham >= 10% OR Magnolia virginiana >= 6%, THEN forest type is LTsw2.

Pinus elliottii 1 2) OR IF Fraxinus profunda + Nyssa biflora < 60% THEN,

Pinus taeda 1 3) IF Fraxinus profunda >= 20% THEN,

Quercus austrina 4) IF ham < 10% AND Magnolia virginiana < 6% AND blh < 15%, 

Quercus chapmanii THEN forest type is LTsw1.

Quercus geminata 4) OR IF ham >= 10% OR Magnolia virginiana >= 6% OR blh >= 15%, 

Quercus hemispherica THEN forest type is LTsw2.

Quercus myrtifolia 3) OR IF Fraxinus profunda < 20%, THEN forest type is LTsw2.

Symplocos tinctoria 1) OR IF sw <= 70% THEN,

Ulmus alata 2) IF up < 50% THEN,

Vaccinium arboreum 3) IF ham + blh < 75%, THEN forest type is LTmix, 1

 In riverine reach.

2

 In tidal reaches.

 3) OR IF ham = blh >= 75%, THEN forest type is LTham,

 2) OR IF up >= 50%, THEN forest type is oak/pine.
Floodplain Hydrology, Topographic Features, and Soils 11

Table 3. Mapping accuracy based on tests of forest type rules at verification 

plots in the floodplain of the lower Suwannee River, Florida (modified from Light 

and others, 2002)

[Rblh, riverine bottomland hardwood forests; Rsw, riverine swamp; UTblh, upper tidal bottomland

hardwood forests; UTmix, upper tidal mixed; UTsw, upper tidal swamp; LTham, lower tidal

hammock; LT mix, lower tidal mixed; LTsw, lower tidal swamp]

Specific forest types

Forest 

type 

name

Number of 

polygons 

mapped

Verification plots

Total 

number 

sampled

Number 

correctly 

mapped

Percent 

correctly 

mapped

Forest types of incorrectly 

mapped plots

oak/pine 506 7 5 71 Rblh2, Rblh3

Rblh3 474 10 6 60 Rblh2, oak/pine (3)

Rblh2 491 11 10 91 Rblh1

Rblh1 654 11 9 82 Rsw2, Rblh2

Rsw2 306 7 4 57 Rsw1 (2), Rblh1

Rsw1 182 5 4 80 Rsw2 

UTblh 202 6 5 83 oak/pine

UTmix 225 5 2 40 UTsw2 (2), UTblh

UTsw2 317 7 4 57 Rsw1, UTsw1, LTsw1

UTsw1 208 4 4 100 none

LTham 204 6 5 83 oak/pine

LTmix 353 7 5 71 UTblh, LTsw2

LTsw2 444 8 5 63 UTsw1, UTblh, LTsw1

LTsw1 417 8 4 50 UTsw1, UTsw2 (2), LTsw2

TOTAL 4,983 102 72 71

used to interpret aerial signatures. 

The forest types of the polygons 

containing the nine verification 

plots were mapped by actual forest 

composition. The forest types (other 

than reach) of polygons containing 

the other 102 verification plots were 

not changed, regardless of actual 

composition.

Seventy-one percent of 102 

verification plots had a canopy composition that qualified as the 

mapped type (table 3), using the 

rules developed from transects. 

Incorrectly mapped sites were 

slightly more likely to be wetter forest types than mapped types. All 

verification sites falling within a 

reach that did not meet rule criteria 

for that reach were considered 

wrongly classified. On 8 of 102 

plots (8 percent), the actual forest 

type was a forest type of a different 

river reach.

Other aerial signatures were 

verified in the field at observation 

sites. Altered upland and wetland 

forests were mapped using a combination of aerial signatures and 

topography based on USGS quadrangle maps. Altered wetland forests could not be assigned to 

specific forest types, but were separated into altered bottomland 

hardwood forests (riverine and 

upper tidal reaches), hammocks 

(lower tidal reach), and swamp 

forests (all reaches).

Mapping was completed for the 

entire study area and the total area 

of each forest type was calculated 

from the polygon coverage. Final 

composition of forest types was 

based on data from transects and 

verification plots. Absolute and relative basal areas and densities for all 

canopy plants and forest types are 

presented in Light and others 

(2002). The areas of altered bottomland hardwood and swamp forests 

were divided between major forest 

types based on the proportion of 

each forest type present in the floodplain reach.

The GIS map was developed as 

a project using ArcExplorer software, and annotations were added to 

polygon label names and land cover 

types (including major forest types). 

ArcExplorer software and instructions are available on the Internet at 

http:\\www.esri.com. The interactive map and software for viewing 

were written on a compact disc 

along with several related coverages 

and this report.

FLOODPLAIN HYDROLOGY, 

TOPOGRAPHIC FEATURES, 

AND SOILS

The hydrology of the river and 

the topographic features, hydrologic 

conditions, and soil characteristics 

of the forested floodplain of the 

lower Suwannee River are discussed 

in detail in Light and others (2002). 

A brief summary of these topics is 

presented in the following sections 

because of their importance in 

determining the distribution of 

floodplain forests.

Hydrology of the River

The Suwannee River is the second largest river in Florida in terms 

of mean discharge. Median flow in 

the upstream part of the study area, 

based on combined flow of the 

Suwannee River at Branford and 

the Santa Fe River near Fort White 

from 1933-99 (fig. 2), was approximately 181 cubic meters per second 

(m3

/s) (6,480 cubic feet per second). At the upper end of the riverine reach, river stages are unaffected 

by tides and have a typical annual 

range of 4.1 m. Tides affect river 

stages at low and medium flows in 

the upper tidal reach, and at all 
12 Forest Types in the Lower Suwannee River Floodplain, Florida—A Report and Interactive Map

flows in the lower tidal reach. 

Median tidal range at the mouth of 

the Suwannee River is about 1 m. In 

the lower part of the lower tidal 

reach, stages during storm surges 

are higher than river flood stages; 

however, duration of storm surges is 

usually less than 24 hours.

Floodplain Topography

and Hydrology

Land-surface elevations and 

topographic relief in the floodplain 

decrease with proximity to the Gulf. 

Elevations range from 4.1 to 7.3 m 

above sea level at the most 

upstream riverine transect and range 

from 0.3 to 1.3 m above sea level at 

lower tidal transects. Elevations 

associated with a variety of statistics describing long-term hydrologic conditions in the river channel 

are shown on cross sections in figure 15 of Light and others (2002). 

Natural riverbank levees are prominent features on the riverine 

transects including the MS transect. 

Levees range from 1 to 3 m high 

and 15 to 80 m wide. Most levees 

and high ridges are vegetated with 

high bottomland hardwood (blh) 

forests. These areas are partially 

submerged during a 2-year flood, 

and totally submerged during a 5-

year flood. Riverbank levees are 

very low or nonexistent on tidal 

transects below MS. The highest 

elevations on tidal transects are in 

blh forests, hammocks, and on the 

tops of the higher hummocks. 

These higher elevations are submerged by large floods and, in the 

lower tidal reach, by storm surges. 

Some lower tidal forests have a distinct hummock-mud floor microtopography that supports hammock 

species on the hummocks and 

swamp species on the mud floor.

Depressions on riverine 

transects are vegetated with swamps. 

Water levels in riverine swamps are 

sometimes higher than water levels in 

the river channel, but standing water 

disappears during severe droughts. 

From the MS transect downstream to 

the Gulf, the influence of river flooding on river stage gradually 

decreases, whereas the influence of 

tides and storm surges on river stage 

gradually increases. Tidal creeks, 

flowing in and out with daily tides, 

are usually located in the riverward 

half of tidal transects. The swamps 

near the upland are isolated from regular tidal inundation.

Floodplain Soils

Soils in all riverine forests 

except the deeper swamps are predominantly mineral (sand, loam, or 

clay) and are dry during low-flow 

periods. Soils in some riverine 

swamps and upper and lower tidal 

forests are predominantly organic 

on the surface, with organic or mineral subsurface textures. Surface 

soils in tidal swamps, lower tidal 

mixed forests, and some riverine 

swamps are continuously saturated. 

Electrical conductivity of surface 

soils in the downstream part of the 

lower tidal reach is high enough to 

exclude some tree species that are 

intolerant of salinity.

MAJOR FOREST TYPES

The 10-year floodplain covers 

about 21,170 hectares; nearly 

88 percent of this area (18,580 hectares) is mapped as upland and 

wetland forest types (fig. 5). About 

75 percent of the area of forest types 

is wetland forests (13,994 ha) and 

about 25 percent is upland forests 

Altered Tidal

Wetland Forests

(1,755 hectares) Upland Forests

(1,681 hectares)

Altered Upland Forests

(2,905 hectares)

Open Water in

Floodplain

(239 hectares)

Open Water in

Main Channel

(1,767 hectares)

Freshwater or Brackish

Marshes (425 hectares)

Other Types (156 hectares)

Altered Riverine

Wetland Forests

(659 hectares)

Upper and

LowerTidal

Wetland Forests

(7,200 hectares)

Riverine (non-tidal)

Wetland Forests

(4,380 hectares)

Seepage slopes (70)

Floodplain glades (46)

Emergent aquatic beds (21)

Isolated wetland forests (19)

Figure 5. Area of land cover types in the 10-year floodplain and main channel of 

the lower Suwannee River, Florida. Numbers in parentheses indicate area, in 

hectares. Total area is about 21,170 hectares.
Major Forest Types 13

(4,586 ha). Tidal wetland forests 

(8,955 ha) cover a much greater area 

than riverine wetland forests 

(5,039 ha). The percentage of wetland forests that would be classified 

as jurisdictional wetlands according 

to criteria in State and Federal wetland regulations is not known. Most 

of the wetlands in the floodplain 

would be classified as palustrine 

using the classification system 

developed by the U.S. Fish and 

Wildlife Service (Cowardin and others, 1979). Approximately 5,320 ha 

(about 29 percent of 18,580 ha) of 

upland and wetland forests have 

been altered by agriculture or development.

Table 4. Summary of hydrologic conditions, soil textures, and dominant canopy species of forest types in the 10-year 

floodplain of the lower Suwannee River, Florida (modified from Light and others, 2002)

[Rbh, riverine bottomland hardwood forests: Rsw, riverine swamp; UTblh, upper tidal bottomland hardwood forests; UTmix, upper tidal mixed; UTsw, 

upper tidal swamp; LTham, lower tidal hammock; LTmix, lower tidal mixed; LTsw, lower tidal swamp]

Forest type Typical hydrologic conditions

Primary soil 

texture in root 

zone

Dominant canopy species

Oak/pine Flooded average of every 10 years; soils dry quickly after floods 

recede Sand

Quercus hemisphaerica

Pinus taeda

Quercus geminata

Rblh3

Rblh2

Flooded average of every 3 years, sometimes for durations of 

1-2 months or more; soils dry quickly after floods recede Sand

Quercus virginiana

Liquidambar styraciflua

Quercus laurifolia 

Rblh1 Flooded average of 2 months every year; soils remain saturated 

another month Sand, loam, clay

Quercus laurifolia

Taxodium distichum

Quercus lyrata

Betula nigra

Liquidambar styraciflua

Rsw2

Rsw1

Flooded 4-7 months every year; soils remain saturated another 

5 months Clay, muck Taxodium distichumPlanera aquatica

UTblh Flooded 1 to 2 months every 2 years; soils dry quickly after floods 

recede Sand Quercus laurifoliaSabal palmetto

UTmix

Flooded 2 to 3 months every year; soils dry quickly in some areas 

and remain continuously saturated in others Loam, muck, sand

Taxodium distichum

Fraxinus profunda

Quercus laurifolia

UTsw2

UTsw1

Flooded monthly by high tides or high river flows; most soils 

continuously saturated Muck

Nyssa aquatica

Taxodium distichum

Fraxinus profunda

LTham

Flooded every 1-2 years by either storm surge or high river 

flows; high water table; surface soils on higher elevations dry 

quickly and soils are continuously saturated in low areas 

Muck, sand Sabal palmetto

Pinus taeda

LTmix Flooded daily or several times a month by high tides, except in 

isolated areas; soils continuously saturated except for hummock 

tops, which have conditions similar to hammocks. 

Muck

Fraxinus profunda

Nyssa biflora

Magnolia virginiana

LTsw2

LTsw1 Muck

Nyssa biflora

Fraxinus profunda

Taxodium distichum

The basic characteristics of 

major forest types with regard to 

hydrologic conditions, soil textures, 

and dominant canopy trees are summarized in table 4. Area of each 

wetland forest type is shown on 

figure 6. Composition of canopy 

and subcanopy vegetation is presented in greater detail in Light and 

others (2002). Composition of 

ground cover vegetation in wetland 

forest types is presented in Darst 

and others (2002).

Oak/pine Uplands

 Oak/pine upland forests are 

present in the riverine and upper 

tidal reaches of the 10-yr floodplain on the highest elevations. 

Most of these forests are inundated 

briefly during the highest floods. 

Many tree species present in 

upland forests cannot survive more 

than brief periods of inundation. 

Quercus hemisphaerica, Pinus

taeda, and Quercus geminata are 

the dominant canopy species in 

oak/pine upland forests. Some 

upland verification sites were oak 

scrub forests where Quercus geminata was the most dominant tree. 

Oak/pine upland forests have been 

altered to a much greater extent 

(63 percent) than wetland forests 

(17 percent).
14 Forest Types in the Lower Suwannee River Floodplain, Florida—A Report and Interactive Map

Riverine Wetland Forests

High bottomland hardwoods 

(Rblh3 and Rblh2) are present primarily on the higher levees, ridges, 

and flats where soils are usually 

sandy (fig. 7). Quercus virginiana is 

the dominant canopy species in 

Rblh3 forests. Quercus laurifolia, 

Quercus virginiana, and Liquidambar styraciflua are dominant in the 

canopy of Rblh2 forests.

Low bottomland hardwood 

forests (Rblh1) (fig. 8) are present 

on slopes around swamps, on low 

levees, ridges, and flats, and in 

higher elevation depressions that 

are flooded continuously for several 

weeks or longer every 1 to 3 years 

and contain plant species adapted to 

periodic inundation and saturation. 

Rblh1 forests have a significant 

proportion of swamp tree species in 

the canopy that distinguish them 

from high bottomland hardwood 

forests in which swamp trees are 

usually absent. Dominance in the 

RIVERINE

UPPER TIDAL

LOWER TIDAL

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000

AREA, IN HECTARES

FOREST TYPE

Rblh3

Rblh2

Rblh1

Rsw2

Rsw1

Utblh

UTmix

UTsw2

UTsw1

LTham

LTmix

LTsw2

LTsw1

891

800

1,060

1,168

461

484

382

1,087

897

617

1,041

1,339

987

179

161

213

76

30

313

21

56

49

1,172

39

50

368 51

UNALTERED FOREST

ALTERED FOREST

STUNTED FOREST

213 AREA IN HECTARES

Figure 6. Area of major wetland forest types in the floodplain of the lower Suwannee River, Florida (modified from Light and 

others, 2002).

Figure 7. Large Quercus 

virginiana and Quercus laurifolia

trees dominate the canopy of a 

high bottomland hardwood forest 

in the riverine reach of the 

floodplain of the lower Suwannee 

River, Florida.
Major Forest Types 15

Rblh1 forest canopy is shared 

between Quercus laurifolia, Taxodium distichum, Quercus lyrata, 

Betula nigra, and Liquidambar 

styraciflua.

Riverine swamps (Rsw2, 

Rsw1) are present in the lowest and 

wettest areas of the floodplain 

(fig. 9) that are either inundated or 

saturated most of the time. Swamps 

contain plant species that have special adaptations for survival in 

anoxic soils. Taxodium distichum is 

dominant in the canopy of Rsw1; 

whereas, Taxodium distichum and 

Planera aquatica share dominance 

in Rsw2. Bottomland hardwood 

species are a minor component in 

the canopy of Rsw1, and a significant component in the canopy of 

Rsw2.

Figure 8. The flared base of Ulmus americana growing in a low bottomland 

hardwood forest in the riverine reach of the floodplain of the lower Suwannee 

River, Florida.

Upper Tidal Wetland 

Forests

Upper tidal bottomland hardwood forests (UTblh) are present on 

sandy soils on high flats and in transitional areas between upland forests and swamps (fig. 10). UTblh 

forests are dominated by Quercus 

laurifolia and Sabal palmetto. 

While the canopy composition of 

UTblh is similar to some hydric 

hammocks, flooding is deeper, 

approximately 1 m during the 

5-year 1-day flood.

Upper tidal mixed forests 

(UTmix) are found on low levees or 

are present as transitional areas 

between swamps and higher forest 

types. A mixed forest (UTmix, 

LTmix) is a tidal forest type dominated by both swamp and bottomland hardwood or hammock tree 

species. Dominance in the UTmix 

canopy is shared by Taxodium distichum, Fraxinus profunda, and 

Quercus laurifolia.

Upper tidal swamps (UTsw2, 

UTsw1) are present at elevations 

below median monthly high stage 

and usually have surface soils that 

are permanently saturated mucks 

(fig. 11). Nyssa aquatica and Taxodium distichum are dominant in the 

canopy of UTsw1. These two species share dominance with Fraxinus 

profunda in UTsw2. Bottomland 

hardwood trees are more important 

in the canopy of UTsw2 than in 

UTsw1.
16 Forest Types in the Lower Suwannee River Floodplain, Florida—A Report and Interactive Map

Figure 9. Taxodium distichum trees growing in a dense stand in a riverine swamp 

in the floodplain of the lower Suwannee River, Florida (from Light and others, 

2002).
Major Forest Types 17

Figure 10. Bottomland hardwood trees such as Quercus laurifolia (in right 

foreground) are the dominant canopy species in the most elevated wetlands of 

the upper tidal reach of the lower Suwannee River, Florida (modified from Light 

and others, 2002).

Figure 11. The bases of trunks of Nyssa aquatica are usually swollen in upper 

tidal swamps in the floodplain of the lower Suwannee River, Florida.
18 Forest Types in the Lower Suwannee River Floodplain, Florida—A Report and Interactive Map

Figure 12. Sabal palmetto is the dominant canopy species in lower tidal 

hammocks in the floodplain of the lower Suwannee River, Florida. Cabbage palms 

become increasingly numerous in hammocks with proximity to the Gulf of Mexico.

Lower Tidal Wetland 

Forests

Lower tidal hammocks 

(LTham) (fig. 12) in the lower 

Suwannee River floodplain are part 

of the Gulf Coastal Hammocks as 

described by Vince and others 

(1989). Hydric hammocks are a 

unique wetland forest type, rare outside Florida, that support a characteristic mixed hardwood forest with 

evergreen and semi-evergreen trees. 

LTham is by far the most altered 

wetland forest type (66 percent) 

(fig. 6). LTham forests are found on 

higher elevations that do not receive 

regular tidal inundation or frequent 

river flooding, but have a high water 

table and are briefly inundated by 

storm surges several times a decade. 

LTham forests are dominated by 

Sabal palmetto and Pinus taeda.

Lower tidal mixed forests 

(LTmix) include swamps with 

numerous small hummocks or less 

common large hummocks, and transitional areas between swamps and 

hammocks. Fraxinus profunda, 

Nyssa biflora and Magnolia virginiana are dominant canopy species in 

LTmix. Lower tidal mixed forests 

and swamps (LTmix, LTsw2, 

LTsw1) are found on deep muck 

soils that are below the elevation of 

the median daily or monthly high 

stage. Fraxinus profunda, Taxodium 

distichum, and Nyssa biflora are the 

most important canopy species in 

LTsw2 and LTsw1 forests (fig. 13). 

Stunted stands of Fraxinus profunda

(fig. 14) are an important variant of 

LTsw1 forests, comprising 27 percent of the total area of LTsw1 

forest (fig. 6). Stunted swamps 

sometimes have scattered individuals or sparse overstories of slightly 

taller Taxodium distichum trees.
Major Forest Types 19

Figure 13. A dense stand of canopy trees in a lower tidal swamp in the 

floodplain of the lower Suwannee River, Florida. Lower tidal swamps were 

dominated by Nyssa biflora, Fraxinus profunda, and Taxodium distichum.

Figure 14. A stunted stand of Fraxinus profunda trees growing along East Pass 

near the tree line in the lower Suwannee River floodplain, Florida. Trees in this 

stand are less than 6 meters tall (from Light and others, 2002).
20 Forest Types in the Lower Suwannee River Floodplain, Florida—A Report and Interactive Map

OTHER LAND 

COVER TYPES

The map of the 10-year 

floodplain includes seven land 

cover types in addition to the 

major forest types (fig.5). Two 

open water land cover types are 

mapped; the main channel of the 

lower Suwannee River (1,767 ha) 

(fig. 15) and open water in the 

floodplain (239 ha). Most areas 

of open water in the non-tidal 

floodplain are ponds in swamps 

(fig. 16). In tidal reaches, open 

water in the floodplain is usually 

found in tidal creeks.

Two minor forest types 

mapped separately are seepage 

slopes and isolated forested wetlands. Seepage slopes (70 ha) are 

usually located between upland 

forests and the wetlands adjacent 

to the main channel. One seepage slope was sampled at a verification plot in the upper tidal 

reach. Although the ground was 

saturated, the vegetation was 

typical of areas with shallow 

flood depths. The presence of 

species such as Pinus taeda, 

Persea palustris, and Pilea 

pumila, indicated that the elevation of this site was probably 

above the average elevations of 

upper tidal mixed forests and 

swamps (Darst and others, 

2002). Small areas of isolated 

forested wetlands (19 ha) were 

separated from the wetlands 

adjacent to the river and were not 

sampled. Their forest composition may be more typical of nonriverine wetlands such as cypress 

domes, shallow sinkholes, and 

gum swamps (Myers and Ewel, 

eds., 1991).

Figure 15. The main channel of the lower Suwannee River, Florida, covers 

1,767 hectares of the total area mapped (21,170 hectares).

Figure 16. An open water pond in the floodplain of the riverine reach of the lower 

Suwannee River, Florida.
Other Land Cover Types 21

Figure 17. Marshes, including this freshwater marsh near Gopher River, cover 

425 hectares of land upstream of the tree line in the floodplain of the lower 

Suwannee River, Florida.

Figure 18. Floodplain glades are non-forested areas in the lower Suwannee 

River floodplain, Florida, that usually have a thick ground cover of grasses and 

sedges.

Nearly all marshes upstream 

of the tree line (425 ha) are found 

in the lower tidal reach (fig. 17). 

Marshes are predominantly freshwater and are dominated by Cladium jamaicense, Zizaniopsis 

miliacea, and other herbaceous 

sedges and grasses. Clewell and 

others (1999) describe tidal 

marshes upstream and downstream 

of the tree line in the lower Suwannee River. Small beds of emergent 

aquatic vegetation (21 ha) are visible on the aerial photographs, 

which were taken in the winter. 

These beds differ from the larger 

beds of emergent vegetation 

present in the main channel in the 

warmer months of the year, which 

were not usually visible on the 

aerial photographs. Winter emergent vegetation is most often found 

in small tidal streams within 

marshes. Emergent plants such as 

Sagittaria lancifolia, Rumex verticillatus, and Hydrocotyle verticillata grow in floating mats or are 

rooted in the shallow edges of 

streams.

Floodplain glades are nonforested areas (46 ha) (fig. 18) that 

were encountered principally in the 

riverine reach of the floodplain. 

Floodplain glades are elevated 

above the wetlands adjacent to the 

river and are usually oval in shape. 

The mean area of the 54 mapped 

glades was less than 1 ha (0.9 ha). 

These areas were seen at several 

observation sites, including one 

shown in figure 18 that was located 

on the eastern side (left bank) of 

the floodplain at rkm 48.0. At this 

site, the ground cover was dominated by Panicum rigidulum.
22 Forest Types in the Lower Suwannee River Floodplain, Florida—A Report and Interactive Map

USES OF THE FOREST MAP

The forest map can be used by 

scientists for ecological studies in 

the floodplain based on land cover 

types and in comparative studies 

with other floodplains. Landowners 

and management personnel can use 

the map to develop property 

descriptions and land use decisions, but on-site verification of 

specific forest types may be desirable on some sites considering that 

verification of the map indicated 

that 71 percent of the polygons 

mapped as major forest types are 

correctly labeled. The mapping of 

seepage slopes and floodplain 

glades will facilitate research on 

these unusual land cover types.

SUMMARY

A map of forest types in the 

lower Suwannee River floodplain, 

Florida, was created during a study 

conducted from 1996 to 2000 by the 

U.S. Geological Survey in cooperation with the Suwannee River Water 

Management District. The map is 

presented with this report on a compact disc with interactive viewing 

software. The study area was the 

10-year floodplain of the lower 

Suwannee River from its confluence with the Santa Fe River to the 

lower limit of forests near the Gulf 

of Mexico. The floodplain was 

divided into three reaches, riverine 

(non-tidal), upper tidal, and lower 

tidal, due to changes in hydrology, 

vegetation, and soils with proximity 

to the coast.

Digital orthophoto quadrangles, developed from color-infrared 

aerial photographs, were used as the 

basis for the floodplain map. Canopy composition for different aerial 

signatures was determined from the 

relative basal area of canopy tree 

species on transects and at nine verification sites. The floodplain map 

accuracy was evaluated using 

102 verification plots. Seventy-one 

percent (71 percent) of verification 

plots had a canopy composition that 

qualified as the mapped forest type.

River stages in the riverine 

reach of the Suwannee River are 

unaffected by tides. The influence 

of river flooding on river stage gradually decreases with proximity to 

the Gulf, and the influence of tides 

and storm surges on river stage 

gradually increases. Tides affect 

river stages at low and medium 

flows in the upper tidal reach, and at 

all flows in the lower tidal reach. In 

the lower part of the lower tidal 

reach, stages during storm surges 

are higher than river flood stages. 

Land-surface elevations and topographic relief in the floodplain 

decrease with proximity to the Gulf. 

Soils in all riverine wetland forests 

but the wettest swamps are mineral 

and dry during low-flow periods. 

Most surface soils in the deepest 

riverine swamps, upper and lower 

tidal swamps, and lower tidal mixed 

forests are continuously saturated 

mucks.

Major forest types in the lower 

Suwannee River floodplain cover 

18,580 ha. Approximately 29 percent 

of the area of floodplain forests has 

been altered by agriculture or development. About 75 percent of the area 

of major forest types is wetland forests (13,994 ha) and about 25 percent 

is upland forests (4,586 ha). Tidal 

wetlands cover a much greater area 

than riverine wetlands.

 Oak/pine upland forests are 

inundated briefly during the highest 

floods. Many tree species present in 

oak/pine forests cannot survive 

more than brief periods of inundation. High bottomland hardwoods 

are present on the higher levees, 

ridges, and flats where soils are usually sandy. Low bottomland hardwood forests are present on slopes 

around swamps, low levees, flats, 

and higher elevation depressions 

that are flooded continuously for 

several weeks or longer every 1 to 

3 years. Most canopy species in low 

bottomland hardwoods are adapted 

to periodic inundation and saturation. Riverine swamps are present in 

the lowest and wettest areas of the 

reach that are either inundated or 

saturated most of the time.

Upper tidal bottomland hardwood forests are present on sandy 

soils on high flats and in areas 

between upland forests and swamps. 

Upper tidal mixed forests are found 

on low levees or in transitional areas 

between swamps and higher forest 

types. Upper tidal swamps are 

present at elevations below median 

monthly high stage and usually have 

surface soils that are permanently 

saturated mucks.

Lower tidal hammocks in the 

lower Suwannee River floodplain 

are found on elevations that do not 

receive regular tidal inundation or 

frequent river flooding, but have a 

high water table and are briefly 

inundated by storm surges several 

times a decade. Lower tidal mixed 

forests include swamps with numerous small hummocks or less common large hummocks. Lower tidal 

mixed and swamp forests are found 

on deep muck soils that are below 

the elevation of the median daily or 

monthly high stage. Stunted stands 

of Fraxinus profunda are an important variant of lower tidal swamps.

The floodplain contains seven 

land cover types covering about 

2,590 ha in addition to the major 

forest types. Water in the main 

channel of the lower Suwannee 

River was mapped separately from 

open water in the floodplain. Seep-
References 23

age slopes usually have saturated 

soils that support species tolerant of 

shallow flooding. Isolated forested 

wetlands were separated from the 

wetlands adjacent to the river. 

Freshwater marshes and beds of 

emergent aquatic vegetation are 

present upstream of the tree line in 

the lower tidal reach. Floodplain 

glades are non-forested areas found 

primarily in the riverine reach of the 

floodplain.

The forest map can be used by 

scientists for ecological studies in 

the floodplain based on land cover 

types and by landowners and management personnel making land use 

decisions. The mapping of seepage 

slopes and floodplain glades will 

facilitate research on these unusual 

land cover types.

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